From b0ef16751cfe0dbc29640ef178ac20f2d7a49dac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=9D=8E=E6=B5=8E=E8=8A=9D?= <whitepure@gmail.com>
Date: Fri, 19 Jul 2024 11:25:30 +0800
Subject: [PATCH] =?UTF-8?q?feat(post):=20=E5=AE=8C=E5=96=84=E6=96=87?=
 =?UTF-8?q?=E7=AB=A0?=
MIME-Version: 1.0
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 rename "blog-site/content/posts/javakeyword/volatile\345\205\263\351\224\256\345\255\227\350\257\246\350\247\243.md" => "blog-site/content/posts/javakeyword/volatile\345\205\263\351\224\256\345\255\227.md" (99%)
 rename "blog-site/content/posts/essays/\346\225\264\345\220\210\346\224\257\344\273\230\345\212\237\350\203\275.md" => "blog-site/content/posts/toy/Java\346\225\264\345\220\210\346\224\257\344\273\230\345\212\237\350\203\275.md" (99%)
 rename "blog-site/content/posts/essays/\346\225\264\345\220\210\346\226\207\344\273\266\344\270\212\344\274\240\345\212\237\350\203\275.md" => "blog-site/content/posts/toy/Java\346\225\264\345\220\210\346\226\207\344\273\266\344\270\212\344\274\240\345\212\237\350\203\275.md" (99%)
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diff --git "a/blog-site/content/posts/essays/Java\347\250\213\345\272\217\344\270\255\345\270\270\350\247\201\351\227\256\351\242\230.md" "b/blog-site/content/posts/codeguide/Java\347\250\213\345\272\217\344\270\255\345\270\270\350\247\201\351\227\256\351\242\230.md"
similarity index 100%
rename from "blog-site/content/posts/essays/Java\347\250\213\345\272\217\344\270\255\345\270\270\350\247\201\351\227\256\351\242\230.md"
rename to "blog-site/content/posts/codeguide/Java\347\250\213\345\272\217\344\270\255\345\270\270\350\247\201\351\227\256\351\242\230.md"
diff --git "a/blog-site/content/posts/essays/Java\347\250\213\345\272\217\345\270\270\350\247\201\346\225\205\351\232\234\346\216\222\346\237\245\345\221\275\344\273\244\345\217\212\345\267\245\345\205\267.md" "b/blog-site/content/posts/codeguide/Java\347\250\213\345\272\217\345\270\270\350\247\201\346\225\205\351\232\234\346\216\222\346\237\245\345\221\275\344\273\244\345\217\212\345\267\245\345\205\267.md"
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rename to "blog-site/content/posts/codeguide/Java\347\250\213\345\272\217\345\270\270\350\247\201\346\225\205\351\232\234\346\216\222\346\237\245\345\221\275\344\273\244\345\217\212\345\267\245\345\205\267.md"
diff --git "a/blog-site/content/posts/essays/\345\246\202\344\275\225\345\201\232\345\245\275\347\250\213\345\272\217\350\256\276\350\256\241\345\212\237\350\203\275.md" "b/blog-site/content/posts/codeguide/\345\246\202\344\275\225\345\201\232\345\245\275\347\250\213\345\272\217\350\256\276\350\256\241\345\212\237\350\203\275.md"
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rename from "blog-site/content/posts/essays/\345\246\202\344\275\225\345\201\232\345\245\275\347\250\213\345\272\217\350\256\276\350\256\241\345\212\237\350\203\275.md"
rename to "blog-site/content/posts/codeguide/\345\246\202\344\275\225\345\201\232\345\245\275\347\250\213\345\272\217\350\256\276\350\256\241\345\212\237\350\203\275.md"
diff --git "a/blog-site/content/posts/essays/\345\246\202\344\275\225\345\207\217\345\260\221\345\217\212\350\247\243\345\206\263bug.md" "b/blog-site/content/posts/codeguide/\345\246\202\344\275\225\345\207\217\345\260\221\345\217\212\350\247\243\345\206\263bug.md"
similarity index 99%
rename from "blog-site/content/posts/essays/\345\246\202\344\275\225\345\207\217\345\260\221\345\217\212\350\247\243\345\206\263bug.md"
rename to "blog-site/content/posts/codeguide/\345\246\202\344\275\225\345\207\217\345\260\221\345\217\212\350\247\243\345\206\263bug.md"
index 9dd41101..9017a33d 100644
--- "a/blog-site/content/posts/essays/\345\246\202\344\275\225\345\207\217\345\260\221\345\217\212\350\247\243\345\206\263bug.md"
+++ "b/blog-site/content/posts/codeguide/\345\246\202\344\275\225\345\207\217\345\260\221\345\217\212\350\247\243\345\206\263bug.md"
@@ -10,7 +10,6 @@ slug: "java-bugs"
 > 1945年，一只小飞蛾钻进了计算机电路里，导致系统无法工作，一位名叫格蕾丝·赫柏的人把飞蛾拍死在工作日志上，写道：就是这个 bug(虫子)，害我们今天的工作无法完成——于是，bug一词成了电脑系统程序的专业术语，形容那些系统中的缺陷或问题。
 
 bug一词，是指“故障”、“缺陷”。了解软件开发的朋友都非常熟悉，程序员和测试人员更不用说，在工作中会常遇到。 作为一名开发人员，项目出现bug是避免不了的。无论你是一名初入职场的小白，还是拥有经验丰富的大佬，只要经常写代码，梳理业务逻辑，很难免不出bug。正所谓常在河边走，哪能不湿鞋。记得以前经常听人说，如果你没有把系统搞宕机过，就不是一名合格的CTO，成为一名出色的开发人员，经验都是一个一个积累起来的。
-
 所谓的bug指的是生产环境发现的问题;那么只要线上不发现问题，那就不是bug。之所以这么讲是因为一旦影响程序的正常使用便会影响公司的利益，公司利益被影响你自己的利益也会被影响;所以为了自己写程序的时候尽量多测试，将可能会应对到的情况想得全一点，减少bug的出现。
 
 程序员能为了减少bug的出现能做的可以从代码方面下手:
diff --git "a/blog-site/content/posts/essays/\346\225\264\346\264\201\347\232\204\344\273\243\347\240\201.md" "b/blog-site/content/posts/codeguide/\346\225\264\346\264\201\347\232\204\344\273\243\347\240\201.md"
similarity index 99%
rename from "blog-site/content/posts/essays/\346\225\264\346\264\201\347\232\204\344\273\243\347\240\201.md"
rename to "blog-site/content/posts/codeguide/\346\225\264\346\264\201\347\232\204\344\273\243\347\240\201.md"
index f82c60ef..d461b51b 100644
--- "a/blog-site/content/posts/essays/\346\225\264\346\264\201\347\232\204\344\273\243\347\240\201.md"
+++ "b/blog-site/content/posts/codeguide/\346\225\264\346\264\201\347\232\204\344\273\243\347\240\201.md"
@@ -152,15 +152,3 @@ slug: "clean-code"
 
 划分代码我认为最重要的作用是使结构单一，减少代码之间的依赖性，降低耦合度，从而提高代码的可维护性。
 
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diff --git "a/blog-site/content/posts/essays/\350\247\204\350\214\203\347\274\226\345\206\231Java\344\273\243\347\240\201\346\200\273\347\273\223.md" "b/blog-site/content/posts/codeguide/\350\247\204\350\214\203\347\274\226\345\206\231Java\344\273\243\347\240\201\346\200\273\347\273\223.md"
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rename from "blog-site/content/posts/essays/\350\247\204\350\214\203\347\274\226\345\206\231Java\344\273\243\347\240\201\346\200\273\347\273\223.md"
rename to "blog-site/content/posts/codeguide/\350\247\204\350\214\203\347\274\226\345\206\231Java\344\273\243\347\240\201\346\200\273\347\273\223.md"
diff --git "a/blog-site/content/posts/essays/\351\207\215\346\236\204\344\270\200\344\270\252\347\250\213\345\272\217.md" "b/blog-site/content/posts/codeguide/\351\207\215\346\236\204\344\270\200\344\270\252\347\250\213\345\272\217.md"
similarity index 99%
rename from "blog-site/content/posts/essays/\351\207\215\346\236\204\344\270\200\344\270\252\347\250\213\345\272\217.md"
rename to "blog-site/content/posts/codeguide/\351\207\215\346\236\204\344\270\200\344\270\252\347\250\213\345\272\217.md"
index e6b6df19..b0199af6 100644
--- "a/blog-site/content/posts/essays/\351\207\215\346\236\204\344\270\200\344\270\252\347\250\213\345\272\217.md"
+++ "b/blog-site/content/posts/codeguide/\351\207\215\346\236\204\344\270\200\344\270\252\347\250\213\345\272\217.md"
@@ -98,18 +98,3 @@ slug: "java-project-reconstitution"
 为此必须要明确重构是经济行为而不是一种道德行为，重构使得开发效率变得更高，因此仅对必要的代码进行重构，某个工作行为如果重复三次就可以认为未来也会存在重复，因此通过重构使得下次工作更加高效，这是一种务实的作法，而重构不一定是需要大规模的展开的任务，重构应该是不断持续进行的，将任务拆解为多个具有完备性的任务，每周完成一个，每个任务的上线都不会引起问题，并使项目变得更好，这是一种持续重构的精神态度，是高效能程序员最应该具有的工作习惯。
 
 如果你在给项目添加新的特性，发现当前的代码不能高效的完成这个任务，并且同样的任务出现三次以上，那么这时你应该先重构，再开发新特性。
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diff --git "a/blog-site/content/posts/essays/ArrayList\350\257\246\350\247\243.md" "b/blog-site/content/posts/detailed/ArrayList\350\257\246\350\247\243.md"
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rename from "blog-site/content/posts/essays/ArrayList\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/detailed/ArrayList\350\257\246\350\247\243.md"
diff --git "a/blog-site/content/posts/essays/CAS\345\216\237\347\220\206.md" "b/blog-site/content/posts/detailed/CAS\350\257\246\350\247\243.md"
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rename from "blog-site/content/posts/essays/CAS\345\216\237\347\220\206.md"
rename to "blog-site/content/posts/detailed/CAS\350\257\246\350\247\243.md"
diff --git "a/blog-site/content/posts/essays/Elasticsearch\350\257\246\350\247\243.md" "b/blog-site/content/posts/detailed/Elasticsearch\350\257\246\350\247\243.md"
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rename from "blog-site/content/posts/essays/Elasticsearch\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/detailed/Elasticsearch\350\257\246\350\247\243.md"
diff --git "a/blog-site/content/posts/essays/HashMap\350\257\246\350\247\243.md" "b/blog-site/content/posts/detailed/HashMap\350\257\246\350\247\243.md"
similarity index 100%
rename from "blog-site/content/posts/essays/HashMap\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/detailed/HashMap\350\257\246\350\247\243.md"
diff --git "a/blog-site/content/posts/essays/MQ\350\257\246\350\247\243.md" "b/blog-site/content/posts/detailed/Kafka\350\257\246\350\247\243.md"
similarity index 99%
rename from "blog-site/content/posts/essays/MQ\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/detailed/Kafka\350\257\246\350\247\243.md"
index 0391d077..9dda9bf5 100644
--- "a/blog-site/content/posts/essays/MQ\350\257\246\350\247\243.md"
+++ "b/blog-site/content/posts/detailed/Kafka\350\257\246\350\247\243.md"
@@ -1,5 +1,5 @@
 ---
-title: "MQ详解"
+title: "Kafka详解"
 date: 2021-10-19
 draft: false
 tags: ["MQ","详解"]
diff --git "a/blog-site/content/posts/essays/MySQL\350\257\246\350\247\243.md" "b/blog-site/content/posts/detailed/MySQL\350\257\246\350\247\243.md"
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rename from "blog-site/content/posts/essays/MySQL\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/detailed/MySQL\350\257\246\350\247\243.md"
diff --git "a/blog-site/content/posts/essays/Netty\350\257\246\350\247\243.md" "b/blog-site/content/posts/detailed/Netty\350\257\246\350\247\243.md"
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rename from "blog-site/content/posts/essays/Netty\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/detailed/Netty\350\257\246\350\247\243.md"
diff --git "a/blog-site/content/posts/essays/Redis\350\257\246\350\247\243.md" "b/blog-site/content/posts/detailed/Redis\350\257\246\350\247\243.md"
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rename from "blog-site/content/posts/essays/Redis\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/detailed/Redis\350\257\246\350\247\243.md"
diff --git "a/blog-site/content/posts/essays/\345\210\206\345\270\203\345\274\217ID.md" "b/blog-site/content/posts/detailed/\345\210\206\345\270\203\345\274\217ID\350\257\246\350\247\243.md"
similarity index 98%
rename from "blog-site/content/posts/essays/\345\210\206\345\270\203\345\274\217ID.md"
rename to "blog-site/content/posts/detailed/\345\210\206\345\270\203\345\274\217ID\350\257\246\350\247\243.md"
index f318f5b0..6f08463f 100644
--- "a/blog-site/content/posts/essays/\345\210\206\345\270\203\345\274\217ID.md"
+++ "b/blog-site/content/posts/detailed/\345\210\206\345\270\203\345\274\217ID\350\257\246\350\247\243.md"
@@ -1,8 +1,8 @@
 ---
-title: "分布式ID"
+title: "分布式ID详解"
 date: 2023-03-13
 draft: false
-tags: ["分布式"]
+tags: ["分布式","详解"]
 slug: "distributed-id"
 ---
 
diff --git "a/blog-site/content/posts/essays/\345\210\206\345\270\203\345\274\217\344\272\213\345\212\241\350\257\246\350\247\243.md" "b/blog-site/content/posts/detailed/\345\210\206\345\270\203\345\274\217\344\272\213\345\212\241\350\257\246\350\247\243.md"
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rename from "blog-site/content/posts/essays/\345\210\206\345\270\203\345\274\217\344\272\213\345\212\241\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/detailed/\345\210\206\345\270\203\345\274\217\344\272\213\345\212\241\350\257\246\350\247\243.md"
diff --git "a/blog-site/content/posts/essays/\345\210\206\345\270\203\345\274\217\351\224\201\350\257\246\350\247\243.md" "b/blog-site/content/posts/detailed/\345\210\206\345\270\203\345\274\217\351\224\201\350\257\246\350\247\243.md"
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diff --git "a/blog-site/content/posts/essays/\346\225\260\346\215\256\347\273\223\346\236\204\344\270\216\347\256\227\346\263\225.md" "b/blog-site/content/posts/detailed/\346\225\260\346\215\256\347\273\223\346\236\204\344\270\216\347\256\227\346\263\225\350\257\246\350\247\243.md"
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rename from "blog-site/content/posts/essays/\346\225\260\346\215\256\347\273\223\346\236\204\344\270\216\347\256\227\346\263\225.md"
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index 3b420c3a..103a2f4d 100644
--- "a/blog-site/content/posts/essays/\346\225\260\346\215\256\347\273\223\346\236\204\344\270\216\347\256\227\346\263\225.md"
+++ "b/blog-site/content/posts/detailed/\346\225\260\346\215\256\347\273\223\346\236\204\344\270\216\347\256\227\346\263\225\350\257\246\350\247\243.md"
@@ -1,8 +1,8 @@
 ---
-title: "数据结构与算法"
+title: "数据结构与算法详解"
 date: 2021-12-10
 draft: false
-tags: ["Java","算法"]
+tags: ["Java","详解"]
 slug: "data-structures-algorithms"
 ---
 
diff --git "a/blog-site/content/posts/essays/Docker\345\205\245\351\227\250.md" "b/blog-site/content/posts/intro/Docker\345\205\245\351\227\250.md"
similarity index 100%
rename from "blog-site/content/posts/essays/Docker\345\205\245\351\227\250.md"
rename to "blog-site/content/posts/intro/Docker\345\205\245\351\227\250.md"
diff --git "a/blog-site/content/posts/essays/Nginx\344\273\213\347\273\215.md" "b/blog-site/content/posts/intro/Nginx\345\205\245\351\227\250.md"
similarity index 99%
rename from "blog-site/content/posts/essays/Nginx\344\273\213\347\273\215.md"
rename to "blog-site/content/posts/intro/Nginx\345\205\245\351\227\250.md"
index 70b2b1a7..d33ccd31 100644
--- "a/blog-site/content/posts/essays/Nginx\344\273\213\347\273\215.md"
+++ "b/blog-site/content/posts/intro/Nginx\345\205\245\351\227\250.md"
@@ -1,5 +1,5 @@
 ---
-title: "Nginx介绍"
+title: "Nginx入门"
 date: 2021-03-04
 draft: false
 tags: ["使用介绍" ,"nginx"]
diff --git "a/blog-site/content/posts/emp/\345\211\215\347\253\257\345\255\246\344\271\240\350\267\257\347\272\277.md" "b/blog-site/content/posts/intro/\345\211\215\347\253\257\345\205\245\351\227\250\345\255\246\344\271\240\350\267\257\347\272\277.md"
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diff --git a/blog-site/content/posts/java/JavaIO.md b/blog-site/content/posts/javabasics/JavaIO.md
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rename to "blog-site/content/posts/javakeyword/strictfp\345\205\263\351\224\256\345\255\227.md"
diff --git "a/blog-site/content/posts/javakeyword/synchronized\345\205\263\351\224\256\345\255\227\350\257\246\350\247\243.md" "b/blog-site/content/posts/javakeyword/synchronized\345\205\263\351\224\256\345\255\227.md"
similarity index 99%
rename from "blog-site/content/posts/javakeyword/synchronized\345\205\263\351\224\256\345\255\227\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/javakeyword/synchronized\345\205\263\351\224\256\345\255\227.md"
index 541b29b1..22688e0c 100644
--- "a/blog-site/content/posts/javakeyword/synchronized\345\205\263\351\224\256\345\255\227\350\257\246\350\247\243.md"
+++ "b/blog-site/content/posts/javakeyword/synchronized\345\205\263\351\224\256\345\255\227.md"
@@ -1,5 +1,5 @@
 ---
-title: "synchronized关键字详解"
+title: "synchronized关键字"
 date: 2024-07-11
 draft: false
 tags: ["Java", "关键字", "详解"]
diff --git "a/blog-site/content/posts/javakeyword/this\345\205\263\351\224\256\345\255\227\350\257\246\350\247\243.md" "b/blog-site/content/posts/javakeyword/this\345\205\263\351\224\256\345\255\227.md"
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diff --git "a/blog-site/content/posts/javakeyword/transient\345\205\263\351\224\256\345\255\227\350\257\246\350\247\243.md" "b/blog-site/content/posts/javakeyword/transient\345\205\263\351\224\256\345\255\227.md"
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diff --git "a/blog-site/content/posts/javakeyword/volatile\345\205\263\351\224\256\345\255\227\350\257\246\350\247\243.md" "b/blog-site/content/posts/javakeyword/volatile\345\205\263\351\224\256\345\255\227.md"
similarity index 99%
rename from "blog-site/content/posts/javakeyword/volatile\345\205\263\351\224\256\345\255\227\350\257\246\350\247\243.md"
rename to "blog-site/content/posts/javakeyword/volatile\345\205\263\351\224\256\345\255\227.md"
index 2dfe4a95..cea7e751 100644
--- "a/blog-site/content/posts/javakeyword/volatile\345\205\263\351\224\256\345\255\227\350\257\246\350\247\243.md"
+++ "b/blog-site/content/posts/javakeyword/volatile\345\205\263\351\224\256\345\255\227.md"
@@ -1,5 +1,5 @@
 ---
-title: "volatile关键字详解"
+title: "volatile关键字"
 date: 2024-07-11
 draft: false
 tags: ["Java", "关键字", "详解"]
diff --git "a/blog-site/content/posts/spring/Spring\350\257\246\350\247\243.md" "b/blog-site/content/posts/spring/Spring\350\257\246\350\247\243.md"
index 34d2a3cb..4ffd3e7b 100644
--- "a/blog-site/content/posts/spring/Spring\350\257\246\350\247\243.md"
+++ "b/blog-site/content/posts/spring/Spring\350\257\246\350\247\243.md"
@@ -1631,7 +1631,7 @@ AbstractAdvisorAutoProxyCreator.getAdvicesAndAdvisorsForBean
    -->AbstractAdvisorAutoProxyCreator.findCandidateAdvisors
    -->BeanFactoryAdvisorRetrievalHelper.findAdvisorBeans
 ```
-BeanFactoryAdvisorRetrievalHelper这个类是一个Spring AOP内部工具类，用来从Bean容器中获取所有Spring的Advisor Bean。
+`BeanFactoryAdvisorRetrievalHelper`这个类是一个Spring AOP内部工具类，用来从Bean容器中获取所有Spring的Advisor Bean。
 该工具内部使用了缓存机制，虽然公开的查找方法可能会被调用多次，但并不是每次都会真正查找，而是会利用缓存。
 ```java
 public List<Advisor> findAdvisorBeans() {
@@ -2171,7 +2171,7 @@ protected Object invokeWithinTransaction(Method method, @Nullable Class<?> targe
 ```
 `invokeWithinTransaction`方法是`TransactionInterceptor`类中的核心方法，它负责在执行目标方法时管理事务的生命周期。首先该方法通过`getTransactionAttributeSource()`获取事务属性源，进而确定当前方法是否需要事务支持。
 接着根据获取的事务属性，选择合适的事务管理器，并生成一个方法标识以记录当前事务的上下文信息。在方法执行前，会检查是否需要开启新的事务，并在事务环境中执行目标方法的逻辑。
-如果方法执行过程中出现异常，事务管理器会回滚事务以保证数据一致性，否则在方法执行成功后，事务管理器将提交事务。最后无论方法执行结果如何，都会清理事务相关的信息，释放资源并恢复状态，来保证事务管理的完整性和有效性
+如果方法执行过程中出现异常，事务管理器会回滚事务以保证数据一致性，否则在方法执行成功后，事务管理器将提交事务。最后无论方法执行结果如何，都会清理事务相关的信息，释放资源并恢复状态，来保证事务管理的完整性和有效性。
 
 简而言之，当一个方法使用了`@Transactional`注解，在程序运行时，JVM为该Bean创建一个代理对象，并且在调用目标方法的时候进行使用`TransactionInterceptor`拦截，代理对象负责在调用目标方法之前开启事务，然后执行方法的逻辑。
 方法执行成功，则提交事务，如果执行方法中出现异常，则回滚事务。同时Spring利用`ThreadLocal`会将事务资源（如数据库连接）与当前线程绑定，以确保在同一事务中共享资源，这些资源在事务提交或回滚时会被清理。
diff --git "a/blog-site/content/posts/essays/\346\225\264\345\220\210\346\224\257\344\273\230\345\212\237\350\203\275.md" "b/blog-site/content/posts/toy/Java\346\225\264\345\220\210\346\224\257\344\273\230\345\212\237\350\203\275.md"
similarity index 99%
rename from "blog-site/content/posts/essays/\346\225\264\345\220\210\346\224\257\344\273\230\345\212\237\350\203\275.md"
rename to "blog-site/content/posts/toy/Java\346\225\264\345\220\210\346\224\257\344\273\230\345\212\237\350\203\275.md"
index 4ef282a8..5e944768 100644
--- "a/blog-site/content/posts/essays/\346\225\264\345\220\210\346\224\257\344\273\230\345\212\237\350\203\275.md"
+++ "b/blog-site/content/posts/toy/Java\346\225\264\345\220\210\346\224\257\344\273\230\345\212\237\350\203\275.md"
@@ -1,8 +1,8 @@
 ---
-title: "整合支付功能"
+title: "Java整合支付功能"
 date: 2023-08-10
 draft: false
-tags: ["应用","设计"]
+tags: ["应用","设计","Java","玩具"]
 slug: "pay-code"
 ---
 
diff --git "a/blog-site/content/posts/essays/\346\225\264\345\220\210\346\226\207\344\273\266\344\270\212\344\274\240\345\212\237\350\203\275.md" "b/blog-site/content/posts/toy/Java\346\225\264\345\220\210\346\226\207\344\273\266\344\270\212\344\274\240\345\212\237\350\203\275.md"
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rename from "blog-site/content/posts/essays/\346\225\264\345\220\210\346\226\207\344\273\266\344\270\212\344\274\240\345\212\237\350\203\275.md"
rename to "blog-site/content/posts/toy/Java\346\225\264\345\220\210\346\226\207\344\273\266\344\270\212\344\274\240\345\212\237\350\203\275.md"
index bbe46fdf..a94d0bff 100644
--- "a/blog-site/content/posts/essays/\346\225\264\345\220\210\346\226\207\344\273\266\344\270\212\344\274\240\345\212\237\350\203\275.md"
+++ "b/blog-site/content/posts/toy/Java\346\225\264\345\220\210\346\226\207\344\273\266\344\270\212\344\274\240\345\212\237\350\203\275.md"
@@ -1,8 +1,8 @@
 ---
-title: "整合文件上传功能"
+title: "Java整合文件上传功能"
 date: 2023-08-11
 draft: false
-tags: ["应用","设计"]
+tags: ["应用","设计","Java","玩具"]
 slug: "uploadfile-code"
 ---
 
diff --git "a/blog-site/content/posts/essays/\347\256\241\351\201\223\346\265\201\350\256\276\350\256\241\347\273\223\345\220\210\344\270\232\345\212\241.md" "b/blog-site/content/posts/toy/Java\347\256\241\351\201\223\346\265\201\350\256\276\350\256\241\347\273\223\345\220\210\344\270\232\345\212\241.md"
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rename from "blog-site/content/posts/essays/\347\256\241\351\201\223\346\265\201\350\256\276\350\256\241\347\273\223\345\220\210\344\270\232\345\212\241.md"
rename to "blog-site/content/posts/toy/Java\347\256\241\351\201\223\346\265\201\350\256\276\350\256\241\347\273\223\345\220\210\344\270\232\345\212\241.md"
index cd48d576..2bb68530 100644
--- "a/blog-site/content/posts/essays/\347\256\241\351\201\223\346\265\201\350\256\276\350\256\241\347\273\223\345\220\210\344\270\232\345\212\241.md"
+++ "b/blog-site/content/posts/toy/Java\347\256\241\351\201\223\346\265\201\350\256\276\350\256\241\347\273\223\345\220\210\344\270\232\345\212\241.md"
@@ -1,8 +1,8 @@
 ---
-title: "管道流设计模式结合业务"
+title: "Java管道流设计模式结合业务"
 date: 2023-06-15
 draft: false
-tags: ["应用","设计"]
+tags: ["应用","设计","Java","玩具"]
 slug: "pipeline-business"
 ---
 
diff --git a/blog-site/public/index.html b/blog-site/public/index.html
index 819d9ffa..ad3563fe 100644
--- a/blog-site/public/index.html
+++ b/blog-site/public/index.html
@@ -299,7 +299,7 @@ <h2><a href='/iblog/posts/javakeyword/java-keyword-volatile/'>volatile关键字
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-arraylist/'>ArrayList详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-arraylist/'>ArrayList详解</a></h2>
     </div>
     
     <div class="list">
@@ -371,7 +371,7 @@ <h2><a href='/iblog/posts/keepupd/interview-junior-javaer/'>速览Java程序员
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/sql-select-fast/'>MySQL详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/sql-select-fast/'>MySQL详解</a></h2>
     </div>
     
     <div class="list">
@@ -505,7 +505,7 @@ <h2><a href='/iblog/posts/jvm/java-memory-divide/'>JVM详解</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/distributed-lock/'>分布式锁详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/distributed-lock/'>分布式锁详解</a></h2>
     </div>
     
     <div class="list">
diff --git a/blog-site/public/index.xml b/blog-site/public/index.xml
index f03dff0a..e36cf75f 100644
--- a/blog-site/public/index.xml
+++ b/blog-site/public/index.xml
@@ -45,9 +45,9 @@
     </item>
     <item>
       <title>ArrayList详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-arraylist/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/java-arraylist/</link>
       <pubDate>Wed, 26 Jun 2024 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-arraylist/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-arraylist/</guid>
       <description>ArrayList 在List接口实现类中，最常用的就是ArrayList，ArrayList类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删</description>
     </item>
     <item>
@@ -59,9 +59,9 @@
     </item>
     <item>
       <title>MySQL详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/sql-select-fast/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/sql-select-fast/</link>
       <pubDate>Thu, 30 May 2024 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/sql-select-fast/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/sql-select-fast/</guid>
       <description>MySQL介绍 MySQL 是一种关系型数据库，主要用于持久化存储我们系统中的一些数据。 MySQL 如此流行的原因，主要具有下面这些优点： 成熟稳定，功能完善。 开源免费。 文档丰富，既有</description>
     </item>
     <item>
@@ -87,9 +87,9 @@
     </item>
     <item>
       <title>分布式锁详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/distributed-lock/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/distributed-lock/</link>
       <pubDate>Sat, 25 May 2024 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/distributed-lock/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/distributed-lock/</guid>
       <description>概述 在代码里面我们常用ReetrantLock、synchronized保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。 类似这样： public</description>
     </item>
     <item>
@@ -583,10 +583,10 @@
       <description>SpringMVC SpringWebMVC是建立在Servlet API上的原始Web框架，从一开始就包含在Spring框架中。正式名称 &amp;ldquo;Spring Web MVC &amp;ldquo;来自其源模块的名称（s</description>
     </item>
     <item>
-      <title>分布式ID</title>
-      <link>http://localhost:1313/iblog/posts/essays/distributed-id/</link>
+      <title>分布式ID详解</title>
+      <link>http://localhost:1313/iblog/posts/detailed/distributed-id/</link>
       <pubDate>Mon, 13 Mar 2023 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/distributed-id/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/distributed-id/</guid>
       <description>分布式ID 在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。 但随着数据日渐增长，主从同步也扛不住了，</description>
     </item>
     <item>
@@ -598,9 +598,9 @@
     </item>
     <item>
       <title>Elasticsearch详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/elasticsearch/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/elasticsearch/</link>
       <pubDate>Tue, 14 Feb 2023 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/elasticsearch/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/elasticsearch/</guid>
       <description>概览 Elasticsearch，简称为 ES， ES是一个开源的高扩展的分布式全文搜索引擎， 是整个 ElasticStack 技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可</description>
     </item>
     <item>
@@ -668,9 +668,9 @@
     </item>
     <item>
       <title>MQ详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-mq/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/java-mq/</link>
       <pubDate>Tue, 19 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-mq/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-mq/</guid>
       <description>概览 MQ 即 messagequeue 消息队列，是分布式系统的重要组件，主要解决异步消息，应用解耦，消峰等问题。从而实现高可用，高性能，可伸缩和最终一致性的架构。使用较多的MQ有：acti</description>
     </item>
     <item>
@@ -696,9 +696,9 @@
     </item>
     <item>
       <title>分布式事务详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-transaction/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/java-transaction/</link>
       <pubDate>Mon, 02 Aug 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-transaction/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-transaction/</guid>
       <description>基础概念 什么是事务 什么是事务？举个例子：你去超市买东西，&amp;ldquo;一手交钱，一手交货&amp;quot;就是一个事务的例子。 交钱和交货必须同时成功，事务才算成功，其</description>
     </item>
     <item>
@@ -717,9 +717,9 @@
     </item>
     <item>
       <title>Redis详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-redis/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/java-redis/</link>
       <pubDate>Thu, 17 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-redis/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-redis/</guid>
       <description>Redis概述 参考文章： https://www.runoob.com/redis/redis-intro.html https://www.redis.com.cn/redis-interview-questions.html 什么是Redis Redis(Remote Dictionary Server) Redis 是一个开源的使用 ANSI C 语言编写、遵守 BSD 协议、支持网络、可基于内存亦可持久化的日志型、Key-Value 数据库，</description>
     </item>
     <item>
@@ -743,13 +743,6 @@
       <guid>http://localhost:1313/iblog/posts/java/rookie-multi-thread/</guid>
       <description>线程与进程 进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。 线程是操作系统能够进行运算调度的最小单位。它被包</description>
     </item>
-    <item>
-      <title>HashMap详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-hashmap/</link>
-      <pubDate>Mon, 03 May 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-hashmap/</guid>
-      <description>HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问</description>
-    </item>
     <item>
       <title>JVM中的一些概念</title>
       <link>http://localhost:1313/iblog/posts/jvm/jvm-about/</link>
@@ -808,9 +801,9 @@
     </item>
     <item>
       <title>Netty详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-netty/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/java-netty/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-netty/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-netty/</guid>
       <description>Netty 参考文章：https://dongzl.github.io/netty-handbook/#/ 概述 Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers &amp;amp; clients. Netty 是一个异步的、基于事</description>
     </item>
     <item>
@@ -960,13 +953,6 @@
       <guid>http://localhost:1313/iblog/posts/essays/java-thread-collection/</guid>
       <description>Java中常用线程安全的集合 在多线程环境中，数据的一致性和线程的安全性是至关重要的。传统的集合类，如ArrayList、HashMap和HashSet，在并发访</description>
     </item>
-    <item>
-      <title>CAS详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/cas-detail/</link>
-      <pubDate>Sat, 04 Apr 2020 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/cas-detail/</guid>
-      <description>CAS CAS全称为Compare and Swap被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更</description>
-    </item>
     <item>
       <title>SpringBoot整合Redis</title>
       <link>http://localhost:1313/iblog/posts/spring/springboot-redis/</link>
@@ -1060,16 +1046,16 @@
     </item>
     <item>
       <title></title>
-      <link>http://localhost:1313/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>http://localhost:1313/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>http://localhost:1313/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>http://localhost:1313/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>http://localhost:1313/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>http://localhost:1313/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
diff --git a/blog-site/public/page/10/index.html b/blog-site/public/page/10/index.html
index 301fd02c..864238b6 100644
--- a/blog-site/public/page/10/index.html
+++ b/blog-site/public/page/10/index.html
@@ -128,72 +128,6 @@ <h1>
         <div class="content">
             
 
-<div class="post animated fadeInDown">
-    <div class="post_title">
-        <h2><a href='/iblog/posts/essays/cas-detail/'>CAS详解</a></h2>
-    </div>
-    
-    <div class="list">
-        <div class="post_content markdown">
-            <p>CAS CAS全称为Compare and Swap被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更......</p>
-        </div>
-    </div>
-    
-    <div class="post_footer">
-        <div class="meta">
-            <div class="info">
-                <span class="field">
-                    <i class="ri-map-pin-time-line"></i>
-                    <span class="date">2020.04.04</span>
-                </span>
-                
-                <span class="field tags">
-                    <i class="ri-stack-line"></i>
-                    
-                    <a href="http://localhost:1313/iblog/tags/%E7%BA%BF%E7%A8%8B/">线程</a>
-                    
-                </span>
-                
-            </div>
-        </div>
-    </div>
-</div>
-
-<div class="post animated fadeInDown">
-    <div class="post_title">
-        <h2><a href='/iblog/posts/spring/springboot-redis/'>SpringBoot整合Redis</a></h2>
-    </div>
-    
-    <div class="list">
-        <div class="post_content markdown">
-            <p>Docker安装和运行Redis 首先从Docker Hub拉取Redis的官方镜像。 docker pull redis:latest 使用docker run命令启动Redis容器。 docker run -d --name redis -p 6379:6379 redis:latest 验证Red......</p>
-        </div>
-    </div>
-    
-    <div class="post_footer">
-        <div class="meta">
-            <div class="info">
-                <span class="field">
-                    <i class="ri-map-pin-time-line"></i>
-                    <span class="date">2020.03.01</span>
-                </span>
-                
-                <span class="field tags">
-                    <i class="ri-stack-line"></i>
-                    
-                    <a href="http://localhost:1313/iblog/tags/springboot/">springboot</a>
-                    
-                    <a href="http://localhost:1313/iblog/tags/redis/">redis</a>
-                    
-                    <a href="http://localhost:1313/iblog/tags/spring/">spring</a>
-                    
-                </span>
-                
-            </div>
-        </div>
-    </div>
-</div>
-
 <div class="post animated fadeInDown">
     <div class="post_title">
         <h2><a href='/iblog/posts/spring/springboot-elasticsearch/'>SpringBoot整合Elasticsearch</a></h2>
@@ -592,7 +526,55 @@ <h2><a href='/iblog/posts/toy/js-birthday-gift/'>Js生日礼物</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/'></a></h2>
+        <h2><a href='/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/'></a></h2>
+    </div>
+    
+    <div class="list">
+        <div class="post_content markdown">
+            <p>......</p>
+        </div>
+    </div>
+    
+    <div class="post_footer">
+        <div class="meta">
+            <div class="info">
+                <span class="field">
+                    <i class="ri-map-pin-time-line"></i>
+                    <span class="date">0001.01.01</span>
+                </span>
+                
+            </div>
+        </div>
+    </div>
+</div>
+
+<div class="post animated fadeInDown">
+    <div class="post_title">
+        <h2><a href='/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/'></a></h2>
+    </div>
+    
+    <div class="list">
+        <div class="post_content markdown">
+            <p>......</p>
+        </div>
+    </div>
+    
+    <div class="post_footer">
+        <div class="meta">
+            <div class="info">
+                <span class="field">
+                    <i class="ri-map-pin-time-line"></i>
+                    <span class="date">0001.01.01</span>
+                </span>
+                
+            </div>
+        </div>
+    </div>
+</div>
+
+<div class="post animated fadeInDown">
+    <div class="post_title">
+        <h2><a href='/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/'></a></h2>
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diff --git a/blog-site/public/page/11/index.html b/blog-site/public/page/11/index.html
index 5a9a2bc2..f72507ce 100644
--- a/blog-site/public/page/11/index.html
+++ b/blog-site/public/page/11/index.html
@@ -128,54 +128,6 @@ <h1>
         <div class="content">
             
 
-<div class="post animated fadeInDown">
-    <div class="post_title">
-        <h2><a href='/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/'></a></h2>
-    </div>
-    
-    <div class="list">
-        <div class="post_content markdown">
-            <p>......</p>
-        </div>
-    </div>
-    
-    <div class="post_footer">
-        <div class="meta">
-            <div class="info">
-                <span class="field">
-                    <i class="ri-map-pin-time-line"></i>
-                    <span class="date">0001.01.01</span>
-                </span>
-                
-            </div>
-        </div>
-    </div>
-</div>
-
-<div class="post animated fadeInDown">
-    <div class="post_title">
-        <h2><a href='/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/'></a></h2>
-    </div>
-    
-    <div class="list">
-        <div class="post_content markdown">
-            <p>......</p>
-        </div>
-    </div>
-    
-    <div class="post_footer">
-        <div class="meta">
-            <div class="info">
-                <span class="field">
-                    <i class="ri-map-pin-time-line"></i>
-                    <span class="date">0001.01.01</span>
-                </span>
-                
-            </div>
-        </div>
-    </div>
-</div>
-
 <div class="post animated fadeInDown">
     <div class="post_title">
         <h2><a href='/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/'></a></h2>
diff --git a/blog-site/public/page/6/index.html b/blog-site/public/page/6/index.html
index 19e3c61a..59f18f06 100644
--- a/blog-site/public/page/6/index.html
+++ b/blog-site/public/page/6/index.html
@@ -361,7 +361,7 @@ <h2><a href='/iblog/posts/spring/java-spring-mvc-webflux/'>SpringMVC与SpringWeb
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/distributed-id/'>分布式ID</a></h2>
+        <h2><a href='/iblog/posts/detailed/distributed-id/'>分布式ID详解</a></h2>
     </div>
     
     <div class="list">
@@ -383,6 +383,8 @@ <h2><a href='/iblog/posts/essays/distributed-id/'>分布式ID</a></h2>
                     
                     <a href="http://localhost:1313/iblog/tags/%E5%88%86%E5%B8%83%E5%BC%8F/">分布式</a>
                     
+                    <a href="http://localhost:1313/iblog/tags/%E8%AF%A6%E8%A7%A3/">详解</a>
+                    
                 </span>
                 
             </div>
@@ -423,7 +425,7 @@ <h2><a href='/iblog/posts/essays/java-bugs/'>如何减少及解决bug</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/elasticsearch/'>Elasticsearch详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/elasticsearch/'>Elasticsearch详解</a></h2>
     </div>
     
     <div class="list">
diff --git a/blog-site/public/page/7/index.html b/blog-site/public/page/7/index.html
index dc4f6add..30cbd657 100644
--- a/blog-site/public/page/7/index.html
+++ b/blog-site/public/page/7/index.html
@@ -260,7 +260,7 @@ <h2><a href='/iblog/posts/essays/net-program-java/'>网络编程</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-mq/'>MQ详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-mq/'>MQ详解</a></h2>
     </div>
     
     <div class="list">
@@ -392,7 +392,7 @@ <h2><a href='/iblog/posts/essays/eye-beam/'>Java程序常见故障排查命令
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-transaction/'>分布式事务详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-transaction/'>分布式事务详解</a></h2>
     </div>
     
     <div class="list">
@@ -491,7 +491,7 @@ <h2><a href='/iblog/posts/essays/java-small-service/'>微服务治理详解</a><
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-redis/'>Redis详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-redis/'>Redis详解</a></h2>
     </div>
     
     <div class="list">
diff --git a/blog-site/public/page/8/index.html b/blog-site/public/page/8/index.html
index 03094c51..f7ff1dfc 100644
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@@ -128,41 +128,6 @@ <h1>
         <div class="content">
             
 
-<div class="post animated fadeInDown">
-    <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-hashmap/'>HashMap详解</a></h2>
-    </div>
-    
-    <div class="list">
-        <div class="post_content markdown">
-            <p>HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问......</p>
-        </div>
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-    
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-        <div class="meta">
-            <div class="info">
-                <span class="field">
-                    <i class="ri-map-pin-time-line"></i>
-                    <span class="date">2021.05.03</span>
-                </span>
-                
-                <span class="field tags">
-                    <i class="ri-stack-line"></i>
-                    
-                    <a href="http://localhost:1313/iblog/tags/java/">Java</a>
-                    
-                    <a href="http://localhost:1313/iblog/tags/%E9%9B%86%E5%90%88/">集合</a>
-                    
-                    <a href="http://localhost:1313/iblog/tags/%E8%AF%A6%E8%A7%A3/">详解</a>
-                    
-                </span>
-                
-            </div>
-        </div>
-    </div>
-</div>
-
 <div class="post animated fadeInDown">
     <div class="post_title">
         <h2><a href='/iblog/posts/jvm/jvm-about/'>JVM中的一些概念</a></h2>
@@ -427,7 +392,7 @@ <h2><a href='/iblog/posts/java/rookie-io/'>JavaIO</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-netty/'>Netty详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-netty/'>Netty详解</a></h2>
     </div>
     
     <div class="list">
@@ -623,6 +588,39 @@ <h2><a href='/iblog/posts/jvm/jvm-stack/'>JVM中的虚拟机栈</a></h2>
     </div>
 </div>
 
+<div class="post animated fadeInDown">
+    <div class="post_title">
+        <h2><a href='/iblog/posts/jvm/jvm-pc-register/'>JVM中的程序计数寄存器</a></h2>
+    </div>
+    
+    <div class="list">
+        <div class="post_content markdown">
+            <p>Java虚拟机定义了若干种程序运行期间会使用到的运行时数据区，其中有一些会随着虚拟机启动而创建，随着虚拟机退出而销毁。 另外一些则是与线程一一对应的，这些与线程对......</p>
+        </div>
+    </div>
+    
+    <div class="post_footer">
+        <div class="meta">
+            <div class="info">
+                <span class="field">
+                    <i class="ri-map-pin-time-line"></i>
+                    <span class="date">2021.03.27</span>
+                </span>
+                
+                <span class="field tags">
+                    <i class="ri-stack-line"></i>
+                    
+                    <a href="http://localhost:1313/iblog/tags/java/">Java</a>
+                    
+                    <a href="http://localhost:1313/iblog/tags/jvm/">JVM</a>
+                    
+                </span>
+                
+            </div>
+        </div>
+    </div>
+</div>
+
 <div class="pagination">
     
     
diff --git a/blog-site/public/page/9/index.html b/blog-site/public/page/9/index.html
index 060c4630..11a016c9 100644
--- a/blog-site/public/page/9/index.html
+++ b/blog-site/public/page/9/index.html
@@ -128,39 +128,6 @@ <h1>
         <div class="content">
             
 
-<div class="post animated fadeInDown">
-    <div class="post_title">
-        <h2><a href='/iblog/posts/jvm/jvm-pc-register/'>JVM中的程序计数寄存器</a></h2>
-    </div>
-    
-    <div class="list">
-        <div class="post_content markdown">
-            <p>Java虚拟机定义了若干种程序运行期间会使用到的运行时数据区，其中有一些会随着虚拟机启动而创建，随着虚拟机退出而销毁。 另外一些则是与线程一一对应的，这些与线程对......</p>
-        </div>
-    </div>
-    
-    <div class="post_footer">
-        <div class="meta">
-            <div class="info">
-                <span class="field">
-                    <i class="ri-map-pin-time-line"></i>
-                    <span class="date">2021.03.27</span>
-                </span>
-                
-                <span class="field tags">
-                    <i class="ri-stack-line"></i>
-                    
-                    <a href="http://localhost:1313/iblog/tags/java/">Java</a>
-                    
-                    <a href="http://localhost:1313/iblog/tags/jvm/">JVM</a>
-                    
-                </span>
-                
-            </div>
-        </div>
-    </div>
-</div>
-
 <div class="post animated fadeInDown">
     <div class="post_title">
         <h2><a href='/iblog/posts/jvm/jvm-start/'>JVM介绍</a></h2>
@@ -629,6 +596,41 @@ <h2><a href='/iblog/posts/essays/java-thread-collection/'>Java中常用线程安
     </div>
 </div>
 
+<div class="post animated fadeInDown">
+    <div class="post_title">
+        <h2><a href='/iblog/posts/spring/springboot-redis/'>SpringBoot整合Redis</a></h2>
+    </div>
+    
+    <div class="list">
+        <div class="post_content markdown">
+            <p>Docker安装和运行Redis 首先从Docker Hub拉取Redis的官方镜像。 docker pull redis:latest 使用docker run命令启动Redis容器。 docker run -d --name redis -p 6379:6379 redis:latest 验证Red......</p>
+        </div>
+    </div>
+    
+    <div class="post_footer">
+        <div class="meta">
+            <div class="info">
+                <span class="field">
+                    <i class="ri-map-pin-time-line"></i>
+                    <span class="date">2020.03.01</span>
+                </span>
+                
+                <span class="field tags">
+                    <i class="ri-stack-line"></i>
+                    
+                    <a href="http://localhost:1313/iblog/tags/springboot/">springboot</a>
+                    
+                    <a href="http://localhost:1313/iblog/tags/redis/">redis</a>
+                    
+                    <a href="http://localhost:1313/iblog/tags/spring/">spring</a>
+                    
+                </span>
+                
+            </div>
+        </div>
+    </div>
+</div>
+
 <div class="pagination">
     
     
diff --git a/blog-site/public/posts/codeguide/clean-code/index.html b/blog-site/public/posts/codeguide/clean-code/index.html
new file mode 100644
index 00000000..37d6a8c3
--- /dev/null
+++ b/blog-site/public/posts/codeguide/clean-code/index.html
@@ -0,0 +1,696 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>整洁的代码 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="为什么要写整洁的代码 为什么要写整洁的代码,回答这个问题之前,也许应该想想写糟糕的代码的原因 是想快点完成吗?还是要赶时间吗?有可能.或许你觉得自己要干好所需要的时" />
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+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
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+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ba%e4%bb%80%e4%b9%88%e8%a6%81%e5%86%99%e6%95%b4%e6%b4%81%e7%9a%84%e4%bb%a3%e7%a0%81">
+                    为什么要写整洁的代码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af%e6%95%b4%e6%b4%81%e7%9a%84%e4%bb%a3%e7%a0%81">
+                    什么是整洁的代码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+                    可读性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
+        
+        
+        
+        
+        
+        
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+        
+        <ul class="nav">
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%90%e8%a1%8c%e6%95%88%e7%8e%87">
+                    运行效率
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
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+        
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+        <ul class="nav">
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%89%a9%e5%b1%95%e6%80%a7">
+                    扩展性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
+        
+        
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%8e%e4%b9%88%e5%86%99%e6%95%b4%e6%b4%81%e7%9a%84%e4%bb%a3%e7%a0%81">
+                    怎么写整洁的代码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
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+        <ul class="nav">
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b3%a8%e9%87%8a%e5%91%bd%e5%90%8d">
+                    注释&amp;命名
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
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+        
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+        
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%87%bd%e6%95%b0%e7%b1%bb">
+                    函数&amp;类
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+        
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+        
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%a3%e7%a0%81%e7%bb%93%e6%9e%84">
+                    代码结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
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+                <a href="http://localhost:1313/iblog/about/">关于</a>
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+        <div id="post_header" class="header animated fadeInDown">
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+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
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+                
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+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
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+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
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+                <span id="sys_function" class="sys_function display_none">
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+                        <h2 id="post_single_title">整洁的代码</h2>
+                        <span id="post_page_title_date" class="date">2022.09.01</span>
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+                    <div class="post_content markdown"><h2 id="为什么要写整洁的代码">为什么要写整洁的代码</h2>
+<p>为什么要写整洁的代码,回答这个问题之前,也许应该想想写糟糕的代码的原因</p>
+<p>是想快点完成吗?还是要赶时间吗?有可能.或许你觉得自己要干好所需要的时间不够;假使花时间清理代码,老板就会大发雷霆.或许你只是不耐烦再搞这套程序,期望早点结束.或许你看了看,自己承诺要做的其他事情,意识到得赶紧弄完手上的东西,好接着做下一件工作.这种事情我们都干过.</p>
+<p>&ldquo;只要你干过编程,就有可能曾经被某人的糟糕代码绊倒过.如果你编程不止两三年,有可能被这种代码拖过腿.进度延缓的程度非常严重.有些团队在项目初期进展迅速,但是有那么一两年的时间却慢如蜗行.如对代码的每次修改都影响到了其他两三处代码.修改无小事.每次修改或添加代码都对那对扭纹柴了然于心,这样才能网上扔更多的扭纹柴.这团乱麻越来越大,在也无法清理,最后束手无策.</p>
+<p>随着混乱的增加,团队生产力也持续下降,趋势余零.当生产力下降时,管理层就只有一件事情可做了:增加更多的人手到项目中,期望提高生产力.可新人不熟悉系统的设计.他们搞不清什么样的修改符合设计的意图,什么样的修改违背设计意图.而且,他们以及团队中的其他人都背负着提高生产力的压力.于是,他们制造了更多的混乱,驱动生产力向零的那端不断下降.</p>
+<p>最后,开发团队造反了,他们告诉管理层,再也无法在这令人生厌的代码基础上做开发.他们要求全新设计.管理层不愿意投入资源完全重启炉灶,他们也不能否认生产力低得可怕.他们只好同意开发者的要求,授权去做一套看上去很美的华丽新设计.</p>
+<p>于是就组建了一只新军.谁都想加入这个团队,因为它是张白纸.他们可以重新来过,搞出点真正漂亮的东西来.但只有最优秀,最聪明的家伙被选中.其余人则继续维护现有的系统.</p>
+<p>现在有两支队伍在竞赛.新团队必须搭建一套新系统,要求实现旧系统的所有功能.另外,还得跟得上旧系统的持续改动.在新系统功能足以对抗旧系统之前,管理层就不会替换掉旧的系统.</p>
+<p>竞赛可能会持续极长的时间.到了完成的时候,新团队的老成员已不知去向,而现有成员则需求重新设计一套新系统,因为这套系统太烂了.</p>
+<p>假如你经历过哪怕是一小段我谈到的这种事,那么你一定知道,花时间保持整洁的代码不但有关于效率,还有关于生存. &quot;</p>
+<p>有时我们抱怨需求变化背离了初期设计.哀叹进度太紧张,没法好好干活.我们把问题归咎于那些愚蠢的经理,苛刻的用户,没用的营销方式.</p>
+<p>经理和营销人员指望从我们这里得到必须的信息，然后才能做出承诺和保证；即便他们没开口问，我们也不该羞于告知自己的想法。用户指望我们验证需求是否都在系统中实现了。项目经理指望我们遵守进度。我们与项目的规划脱不了干系，对失败负有极大的责任：特别是当失败与糟糕的代码有关时尤为如此！
+“且慢！”你说。“不听经理的，我就会被炒鱿鱼。”多半不会。多数经理想要知道实情，即便他们看起来不喜欢实情。多数经理想要好代码，即便他们总是痴缠于进度。他们会奋力卫护进度和需求；那是他们该干的。你则当以同等的热情卫护代码。</p>
+<p>再说明白些，假使你是位医生，病人请求你在给他做手术前别洗手，因为那会花太多时间，你会照办吗？本该是病人说了算；但医生却绝对应该拒绝遵从。为什么？因为医生比病人更了解疾病和感染的风险。医生如果按病人说的办，就是一种不专业的态度,更别说是犯罪了。同理，程序员遵从不了解混乱风险的经理的意愿，也是不专业的做法。我们应该加强这方面的意识。</p>
+<p>程序员面临着一种基础价值谜题。有那么几年经验的开发者都知道，之前的混乱拖了自己的后腿。但开发者们背负期限的压力，只好制造混乱。简言之，他们没花时间让自己做得更快！真正的专业人士明白，这道谜题的第二部分说错了。制造混乱无助于赶上期限。混乱只会立刻拖慢你，叫你错过期限。赶上期限的唯一方法一做得快的唯一方法就是始终尽可能保持代码整洁。</p>
+<p>&ldquo;如果你不明白整洁对于代码有何意义,尝试去写整洁代码就会毫无所益.&rdquo;</p>
+<p><strong>截取自《代码整洁之道》</strong></p>
+<h2 id="什么是整洁的代码">什么是整洁的代码</h2>
+<p>每个人对于整洁的代码理解肯定不同,在我看来,满足业务场景的情况下,可读性强,运行效率高,细节处理好,易扩展的代码就是整洁代码. 抛开业务场景不谈,只谈所谓的&quot;整洁代码&quot;就是所谓的耍流氓。</p>
+<p>整洁的代码总是看起来总是像是某位特别在意它的人写的.几乎没有改进的余地.代码的作者什么都想到了.如果你想改进它,总会回到原点。</p>
+<p>代码的作用是为了解决人们的某种需求,什么语言不重要(但是总有人非要争个高低),问题解决了才重要.在规定的业务场景下,写出能解决用户需求的代码就是程序员的日常工作,而需求并不是一成不变的,需求会变代码也会改变,所以我们就需要再这个特定的业务场景中尽量把代码变得灵活起来,之后增加需求或者修改需求时,会变的容易一些。</p>
+<p>至于方法的规范命名,可读性,注释等.这些也很重要,毕竟开发的时候一般都是团队一起来开发,代码不止你自己看,还需要别人看,说简单一些就是别人好接手你的代码,即代码的维护</p>
+<h3 id="可读性">可读性</h3>
+<p>在一个产品的周期中,开发其实只占了一小段时间,绝大多数时间都在维护代码.代码写出来首先是给人看的,其次是给电脑看,所以代码的可读性至关重要.所以,如果我非要在代码的可读性和运行效率之间选择一个,非可读性莫属.一般来说,要权衡代码的可读性和运行效率,如果差距太大,要看实际的业务场景来决定,毕竟写程序的最终目的是为了解决用户的某些问题.</p>
+<p>可读性通常表现在代码易于理解</p>
+<ul>
+<li>容易理解整个应用程序的执行流程</li>
+<li>容易理解不同对象之间的协作方式</li>
+<li>容易理解每个类的作用和责任</li>
+<li>容易理解每个方法的作用</li>
+<li>容易理解每个表达式和变量的目的是什么</li>
+</ul>
+<p>如果一个方法的行数过多也会影响代码的可读性,一般控制在80行左右。过多无用的注释、API,只会加重使用者的认知负担,过多无用的信息读起来只会浪费时间，所以要尽量保持API的精简，代码注释的合理，保持规范的命名，使注释看起来没那么臃肿。要知道代码有人维护，可注释没有人维护。</p>
+<p>代码依赖性导致了变化的放大和高认知负荷。模糊性造成了未知的不可知性，导致了认知负荷。从而使得代码更加难以理解,从而不能很好的维护. 所以整洁的代码总是复杂性低的。</p>
+<h3 id="运行效率">运行效率</h3>
+<p>运行效率即代码的运行效率，包括运行所占用的时间和空间。如果数据量不是很大（单表在300w左右）可能几乎不用考虑这个问题，空间就更不用说了，现在大多数公司都是用空间来换时间的，即通过增加服务器的配置或数量来提高程序运算速度。所以很多人并不关心程序运行的效率。</p>
+<p>诚然，我也不是很关心软件的运行效率，因为软件的运行效率主要还是取决与硬件的发展水平，现在硬件发展比软件发展快了一个档次，不然现在也不能一下子涌起那么多的软件公司。</p>
+<p>但是，如果业务量非常大，电脑的运行效率也是有限的，当服务器达到一定数量后，企业就会考虑成本毕竟不能一直毫无节制的增加下去，这时候就需要考虑程序的运行效率了。</p>
+<p>作为一个好的程序员，你不得不具备这项技能。</p>
+<p>怎样提高程序的运行效率，有没有想过？程序是算法和数据结构组成的，数据结构决定一个程序的空间复杂度，算法则决定一个程序的时间复杂度。 想要程序跑的更快，空间占用更少，可以从这两个维度来进行探索。</p>
+<p>一个好的算法离不开一个好的想法，这对于一个程序来说是至关重要的，因为它是决定了程序运行速度的关键原因。可能很多人都有一个误区，就是代码越少执行效率就越高，在改进算法的时候会通过删减代码来进行。举个例子：匹配字符串，在数据量很大的情况下，暴力匹配的方式无论你怎么改，都会比那些运用了好的算法的程序慢。</p>
+<p>不整洁的代码是混乱的，代码混乱到一定程度就会对程序的运行速度产生影响。所以，代码的整洁程度一定程度上影响了代码的运行速度。</p>
+<h3 id="扩展性">扩展性</h3>
+<p>整洁的代码除了是可读性强、运行效率高还有最重要的一点是它是容易扩展的。扩展性可理解为易于修改的代码。程序的扩展性代表了维护该程序程度的难易，当然可读性也是，二者都很重要。</p>
+<p>在所有的设计模式中，几乎所有的设计模式都是为了符合开闭原则，即保持程序的扩展性，重要程度可见一斑。</p>
+<p>代码都是为了一定的需求服务的，但是这些需求并不是一成不变的，当需求变更了，如果我们代码的扩展性很好，我们可能只需要简单的添加或者删除模块就行了，如果扩展性不好，可能所有代码都需要重写，那就是一场灾难了，所以提高代码的扩展性是很重要的。</p>
+<p>衡量代码扩展性可以从高内聚，低耦合这两个方面来衡量。</p>
+<blockquote>
+<p>高内聚：一个软件单位内部的关联紧密程度；有关联的事务应该放在一起。
+低耦合：两个或多个软件单位之间的关联紧密程度；软件单位之间尽可能的不要相互影响。</p>
+</blockquote>
+<h2 id="怎么写整洁的代码">怎么写整洁的代码</h2>
+<p>好的代码是不断的迭代出来的,没有人能一下子写完整 ,需求会变代码也会改变 第一次迭代可能写的代码很糟糕,这时一定要再次回头去看之前的代码,去优化,重构,让代码变得易于维护.</p>
+<p>如何写出整洁的代码,那就看你怎么理解整洁的代码,理解的不一样写出来的肯定就不一样.下面是我的几点建议</p>
+<h3 id="注释命名">注释&amp;命名</h3>
+<p>注释只是二手的信息,它和代码所传达的信息并不等价.所以，不要写没有意义的注释(冗余注释,废弃注释,等一些没有意义的信息和不恰当的信息),要知道代码有人维护,可注释没有人维护,最好的办法就是规范变量,方法的命名,做到见名知意; 如果你的方法命名足够明确就可以不用写注释了，当然一段好的注释一定是包含代码中没有体现的信息。</p>
+<p>如果要编写一条注释,就花时间尽量保证写出最好的注释 不要画蛇添足,要保持注释的简洁。比如，无用的代码直接删掉,不要注释它,不用担心会丢,版本服务会有记录能找回。编写注释和迭代代码是一样的道理。但是一般注释是没有人来维护的，因为它不会影响程序的正常运行。</p>
+<p>同样的，命名也不会影响程序的正常运行。注释和命名是不会影响程序的执行的，但是这两个因素是会影响到开发者编写代码的。它会导致开发者的认知负荷增加，从而降低编写代码的效率。</p>
+<p>“ 好的代码本身就是注释，我们要尽量规范和美化自己的代码来减少不必要的注释。若编程语言足够有表达力，就不需要注释，尽量通过代码来阐述。”编程语言的表达力很大程度上就取决于方法的命名。</p>
+<p>那什么是好的命名呢？说实话这也是我编程一直头疼的原因，总觉得命名不够好。在网络上看到一种方法觉得很不错: 把你的变量名拎出来，问别人，你看到这个名字会想到什么，他说的和你想的一致，就用，否则就改。改到基本上不懂程序的人都能大概看懂你写的是什么，那大概就是好的命名了。</p>
+<p>程序的命名我认为是约定俗成的，最初开始编程的开发者们，他们一定会遇到这个问题的，久而久之就会建立一套规则将这些命名进行统一。到了现在一定是有很多成熟的命名规则的，所以我们可以踩着前辈们的肩膀前行。</p>
+<p>虽然是约定俗成的,但是事物的发展一定不是一成不变的,我并不知道在我写下这么多文字后是否适用于未来,或许大概只有思想会适用,而那些具体的方法是一定不会适用的,但是现在我们需要具体的解决方案,或许我能给你提点建议,如果能帮到你我会很高兴的.</p>
+<p>注释</p>
+<ul>
+<li>尽量保持代码的简洁,能不用注释尽量不用注释,切记注释应该展示代码中没有展示的信息</li>
+<li>注释代码,那么应该在注释代码的上方详细的说明,而不是简单的注释,如果没有用则应该删除</li>
+<li>注释也要随着程序的修改而不断更新，一个误导的注释往往比没有注释更糟糕</li>
+</ul>
+<p>命名</p>
+<ul>
+<li>命名尽量不要使用缩写,因为意义不明确,除非缩写是外界公认的,比如: EN,CH</li>
+<li>在Java中较为适用的是驼峰命名法,如: helloWord,HelloWord ,但是这种方法如果命名过长也不能很直观的展示信息,所以尽量不要起太长的名字,否则什么方法都不管用,如果一个方法的名字过长那么很可能这个方法不止做了一件事,这时候我们需要将它拆分.</li>
+<li>接口和类的名称首字母大写(MyClass/MyInterface) ,方法的名称首字母小写(myMethod),常量的命名全部大写(MY _CONSTANT)同时用蛇形命名法,单词的分割用下划线隔开</li>
+<li>方法的命名用动词,类的命名用名词,属性的命名用名词,接口的命名用形容词或动词,抽象类的命名应以Abstract/Base为前缀,实现类命名要以impl结尾,异常类以Exception结尾</li>
+</ul>
+<h3 id="函数类">函数&amp;类</h3>
+<p>最好的方法入参参数是0个,其次是1,最多建议不超过3个,大于三个建议封装成对象,这样做的好处是方便扩展管理;在一个方法中声明变量应该在方法的最前面,我们应该降低方法的复杂度,避免出现if..else多层嵌套的情况，当然,如果一个方法过于复杂可将该方法进行拆分；还应当注意方法中异常块的处理,一般情况下是不会写的,因为有全局异常处理,如果非要写那么可能代码看起来不是那么简洁清晰.注意方法的封装.在方法调用本地方法的时候,本地的方法尽量使用基础类型作为返回值,好处是避免空指针判断和隐式拆包和打包.当我们写方法返回值的时候,如果返回值类型是数组或集合,我们应该避免返回null,否则调用方就有可能出现空指针.可以避免不必要的空指针判断。</p>
+<p>或许我应该更加细致的标出</p>
+<ul>
+<li>减少函数的入参数量，控制在三个以内，超过三个封装成对象</li>
+<li>使用卫语句，策略模式，职责链模式来减少if..else多层嵌套和不必要的else；用三元运算符代替简单if&hellip;else（根据不同的情境使用，可能会影响代码的可读性）</li>
+<li>拆分超长函数(函数行数阈值80~100行左右就要考虑拆分)；复杂的条件表达式，循环语句，代码块，lambda匿名内部类，都可以单独将其封装成方法；如果是方法内部调用方法的返回值应尽量用基础类型 （并不是方法越多越好，方法之间的互相调用也会影响性能，增加复杂度，请根据实际情况拆分）</li>
+<li>方法的返回值如果是集合或者数组，不要返回null，尽量返回空值，这样可以避免空指针的判断，从而精简代码</li>
+</ul>
+<p>除了上述的几点以外，在写函数的时候还要遵循单一职责原则，即每个方法只做一件事，好处是方便管理,代码可读性会提高,复杂度降低 易于维护。也要遵循开闭原则，这会使你的代码更加灵活。当然这些代码肯定不是一次就写出来的，好的代码需要迭代，需要打磨。在你写完几个函数之后，可能会发现重复的地方，这时候就需要将他们抽象出来。</p>
+<p>许许多多的函数组成了类,当函数之间相互调用的时候，就会存在多个类之间的联系，所以在编写类的时候要注意类之间的依赖关系，使它们别那么耦合，一般会遵循迪米特法则。</p>
+<p>属性的存在使类中的元素更加丰富，一般情况下属性在类中都是私有的，会对外提供set，get方法供外部调用修改；这样做的好处是方便控制外部调用，假如你想公共处理某个属性给它加个前缀，就可以通过调用该类中涉及到该属性的方法进行修改，如果你直接修改属性那么改起来会很麻烦。</p>
+<p>极少数情况是公共的，比如定义一个常量类，公共的资源属性。还有多数情况下是受保护的，该种情况一般是用来给子类使用的，当然同一个包下也能访问得到。</p>
+<h3 id="代码结构">代码结构</h3>
+<p>高内聚低耦合，这是我们写代码应该遵循的标准。内聚代表着职责的专一，这是整洁的一个很重要准则。从大的方面来说，系统的使用与构造需要明确的区分开，才不会将整个结构混杂在一起。与此同时，决定了系统的数据流走向也是决定了整个系统的层级划分，不同的层级也需要明确的区分开来。</p>
+<p>那么应该怎么划分代码的结构?最简单的应该同类型的相关联的表需要放在一个类中或一个包中,写一些方法对外提供api,供其他方法调用，而不是跨层调用。</p>
+<p>一个好的结构使代码看上去更加清晰,更加容易维护,其实它更像是对系统架构的拆分。最常见的系统分层应该是MVC结构，即模型层、视图层、控制层。我们应当更加详细的将MVC进行划分，最常见的我们将控制层又分为业务层（service）和持久层（dao）。 划分的目的是规划软件系统的逻辑结构便于开发维护。但是，随着微服务的演变和不同研发的编码习惯，往往导致了代码分层不彻底导致引入了“坏味道”。</p>
+<p>划分代码我认为最重要的作用是使结构单一，减少代码之间的依赖性，降低耦合度，从而提高代码的可维护性。</p>
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+
+
+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/blog-site/public/posts/codeguide/java-always-problems/index.html b/blog-site/public/posts/codeguide/java-always-problems/index.html
new file mode 100644
index 00000000..3cf3cc19
--- /dev/null
+++ b/blog-site/public/posts/codeguide/java-always-problems/index.html
@@ -0,0 +1,1742 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java程序常见问题 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="CPU使用过高 一般在生产环境排查程序故障，都会查看日志什么的，但是有些故障日志是看不出来的，就比如：CPU使用过高。 那应该怎么办呢？我们需要结合linux命令和" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
+    
+
+	
+
+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cpu%e4%bd%bf%e7%94%a8%e8%bf%87%e9%ab%98">
+                    CPU使用过高
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e6%9f%a5%e8%bf%87%e7%a8%8b">
+                    排查过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%ad%bb%e9%94%81">
+                    死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e6%9f%a5%e8%bf%87%e7%a8%8b-1">
+                    排查过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-1">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e8%b5%84%e6%ba%90%e6%9c%89%e5%ba%8f%e5%88%86%e9%85%8d%e6%b3%95%e9%81%bf%e5%85%8d%e6%ad%bb%e9%94%81">
+                    使用资源有序分配法避免死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e9%93%b6%e8%a1%8c%e5%ae%b6%e7%ae%97%e6%b3%95%e9%81%bf%e5%85%8d%e6%ad%bb%e9%94%81">
+                    使用银行家算法避免死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8-trylock-%e8%bf%9b%e8%a1%8c%e8%b6%85%e6%97%b6%e9%94%81%e5%ae%9a">
+                    使用 tryLock 进行超时锁定
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%85%e5%ad%98%e6%b3%84%e9%9c%b2">
+                    内存泄露
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e6%9f%a5%e8%bf%87%e7%a8%8b-2">
+                    排查过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-2">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jvm%e5%8f%82%e6%95%b0%e8%b0%83%e4%bc%98">
+                    JVM参数调优
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e4%b8%8a%e6%8e%a5%e5%8f%a3%e6%85%a2">
+                    线上接口慢
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9a%e4%bd%8d%e9%97%ae%e9%a2%98">
+                    定位问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-3">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e6%8d%ae%e5%ba%93%e6%85%a2sql">
+                    数据库慢sql
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b0%83%e7%94%a8%e7%ac%ac%e4%b8%89%e6%96%b9%e6%8e%a5%e5%8f%a3%e6%85%a2">
+                    调用第三方接口慢
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ad%e9%97%b4%e4%bb%b6%e6%85%a2">
+                    中间件慢
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%a8%8b%e5%ba%8f%e9%80%bb%e8%be%91%e6%85%a2">
+                    程序逻辑慢
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9e%b6%e6%9e%84%e4%bc%98%e5%8c%96">
+                    架构优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#transactional">
+                    @Transactional
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#transactional%e5%a4%b1%e6%95%88%e6%83%85%e5%86%b5">
+                    @Transactional失效情况
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#transactional%e9%81%87%e5%88%b0%e9%94%81">
+                    @Transactional遇到锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1688701481347" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3517" width="16" height="16"><path d="M425.610455 85.814544H149.05897A42.303635 42.303635 0 0 0 106.6274 128.075535V896.492068c0 23.326702 18.976933 42.26099 42.43157 42.26099h682.743143a42.559504 42.559504 0 0 0 42.431569-42.559504v-384.016365a42.644793 42.644793 0 0 1 85.289587 0v384.016365A127.849091 127.849091 0 0 1 831.802113 1024H149.05897A127.635867 127.635867 0 0 1 21.337813 896.449423V128.03289A127.593222 127.593222 0 0 1 149.101614 0.524957h276.466196a42.644793 42.644793 0 0 1 0 85.289587z m564.062683 158.08425l-170.579174 170.579173a42.644793 42.644793 0 1 1-60.299738-60.299738L856.578738 256.393718H618.364922a42.644793 42.644793 0 1 1 0-85.289587h238.213816l-97.784512-97.784511A42.644793 42.644793 0 1 1 819.093964 13.019882l170.579174 170.579174a42.644793 42.644793 0 0 1 0 60.299738zM149.272194 597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h51.514911c59.190973 0 107.891327 23.284057 107.976617 97.102195 0 71.003581-49.46796 102.347504-106.185536 102.347504h-31.343923v66.781747a32.282109 32.282109 0 0 1-64.606862 0V597.552066z m92.709781 100.215264c31.429213 0 46.568114-16.46089 46.568114-45.757863 0-30.064579-17.313786-40.512554-48.359196-40.512554h-26.311837v86.270417h28.145563z m232.414124-142.860058c81.878003 0 136.036891 43.710913 136.036891 147.67892S556.231457 853.420826 477.935617 853.420826h-38.16709a42.644793 42.644793 0 0 1-42.644794-42.644793v-213.223967a42.644793 42.644793 0 0 1 42.644794-42.644794h34.542282z m-4.008611 240.729859c43.32711 0 73.988717-22.047358 73.988717-93.050939 0-71.046226-30.704251-90.705476-73.988717-90.705476h-8.699538v183.79906h8.699538zM692.481573 853.420826a32.282109 32.282109 0 0 1-32.282109-32.282108V597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h99.063855a29.680776 29.680776 0 1 1 0 59.404197h-77.144431v65.374469h61.749661a29.894 29.894 0 1 1 0 59.788h-61.749661v81.66478a32.282109 32.282109 0 0 1-32.282108 32.282108z" fill="#5f5f5f" p-id="3518"></path></svg>
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+                        <h2 id="post_single_title">Java程序常见问题</h2>
+                        <span id="post_page_title_date" class="date">2024.05.28</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
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+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="cpu使用过高">CPU使用过高</h2>
+<p>一般在生产环境排查程序故障，都会查看日志什么的，但是有些故障日志是看不出来的，就比如：CPU使用过高。
+那应该怎么办呢？我们需要结合linux命令和JDK相关命令来排查程序故障。</p>
+<h3 id="排查过程">排查过程</h3>
+<ol>
+<li>首先使用top命令，找出CPU占比最高的Java进程，然后进一步定位后台程序，如果发现使用过高的进程ID，记录下来方便排查。</li>
+<li>定位到具体的线程，使用<code>ps -mp 进程ID -o THREAD,tid,time</code>命令可以找到有问题的线程ID。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">ps -mp 进程ID -o THREAD,tid,time 说明：
+</span></span><span class="line"><span class="cl">-m：显示所有线程；
+</span></span><span class="line"><span class="cl">-p：pid进程使用CPU的时间；
+</span></span><span class="line"><span class="cl">-o：该参数后是用户自定义参数
+</span></span></code></pre></div></li>
+<li>获取到线程ID后，需要将线程ID转化为16进制格式，如果有英文要小写格式；可以用命令<code>printf &quot;%x\n&quot; 线程ID</code>，当然也可以使用工具从10进制转16进制。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">printf &#34;%x\n&#34; 16
+</span></span></code></pre></div></li>
+<li>线程ID转成16进制后，执行最后一个命令：<code>jstack 进程ID | grep 16进制线程ID -A50</code>或者dump下来，<code>jstack pid &gt; pid.log</code>，就能看到有问题的代码。</li>
+</ol>
+<h3 id="解决方案">解决方案</h3>
+<ol>
+<li>将dump文件下载下来，上传到第三方网站，如：https://fastthread.io/ 进行分析，然后找到解决方案；</li>
+<li>确定是否新部署或有新变更： 首先需要确认是否在最近进行了新的部署或有其他相关的变更，例如代码更新、配置修改等。这些变更可能导致应用出现性能问题，特别是在高负载情况下；</li>
+<li>确定是否可重现问题：尝试重现CPU飙高的问题，可以通过模拟实际场景、使用压力测试工具或者观察日志等方式来尽量还原问题。如果能够确定问题的可重现性，将有助于后续的排查和分析；</li>
+<li>确定是否为GC造成：Java应用中频繁进行垃圾回收可能会导致CPU飙高。可以通过查看GC日志、分析堆内存使用情况以及GC时间等指标来确认是否为GC引起了性能问题；</li>
+<li>确定是否线程阻塞：线程阻塞也是常见的导致CPU飙高的原因之一。可以通过线程监控工具，如JMC、VisualVM，来检查是否存在长时间阻塞的线程，并分析造成线程阻塞的原因；</li>
+</ol>
+<h2 id="死锁">死锁</h2>
+<p>死锁是指两个或多个线程在执行过程中，由于竞争资源或者互相等待释放资源而造成的一种僵局，使得所有参与的线程无法继续执行。
+举个例子，当线程A持有锁a并尝试获取锁b，线程B持有锁b并尝试获取锁a时，就会出现死锁。简单来说，死锁问题的产生是由两个或者以上线程并行执行的时候，争夺资源而互相等待造成的。</p>
+<h3 id="排查过程-1">排查过程</h3>
+<p>死锁经常表现为程序的停顿，或者不再响应用户的请求。从操作系统上观察，对应进程的CPU占用率为零，很快会从top的输出中消失。模拟死锁代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;lockA&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;lockB&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadHolderLock</span><span class="p">(</span><span class="n">lockA</span><span class="p">,</span><span class="n">lockB</span><span class="p">),</span><span class="s">&#34;线程AAA&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadHolderLock</span><span class="p">(</span><span class="n">lockB</span><span class="p">,</span><span class="n">lockA</span><span class="p">),</span><span class="s">&#34;线程BBB&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ThreadHolderLock</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Runnable</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ThreadHolderLock</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lockA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lockA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lockB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lockB</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lockA</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 持有锁 &#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockA</span><span class="o">+</span><span class="s">&#34;, 尝试获得&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockB</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lockB</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 持有锁 &#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockB</span><span class="o">+</span><span class="s">&#34;, 尝试获得&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockA</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><ol>
+<li>使用<code>jps -l</code>命令找到程序进程；</li>
+<li>使用<code>jstack pid</code>命令打印堆栈信息；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Found one Java-level deadlock:
+</span></span><span class="line"><span class="cl">=============================
+</span></span><span class="line"><span class="cl">&#34;线程BBB&#34;:
+</span></span><span class="line"><span class="cl">  waiting to lock monitor 0x00007feb0d80b018 (object 0x000000076af2d588, a java.lang.String),
+</span></span><span class="line"><span class="cl">  which is held by &#34;线程AAA&#34;
+</span></span><span class="line"><span class="cl">&#34;线程AAA&#34;:
+</span></span><span class="line"><span class="cl">  waiting to lock monitor 0x00007feb0d80d8a8 (object 0x000000076af2d5c0, a java.lang.String),
+</span></span><span class="line"><span class="cl">  which is held by &#34;线程BBB&#34;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Java stack information for the threads listed above:
+</span></span><span class="line"><span class="cl">===================================================
+</span></span><span class="line"><span class="cl">&#34;线程BBB&#34;:
+</span></span><span class="line"><span class="cl">    at com.github.springcloud.service.ThreadHolderLock.run(MainTest.java:35)
+</span></span><span class="line"><span class="cl">    - waiting to lock &lt;0x000000076af2d588&gt; (a java.lang.String)
+</span></span><span class="line"><span class="cl">    - locked &lt;0x000000076af2d5c0&gt; (a java.lang.String)
+</span></span><span class="line"><span class="cl">    at java.lang.Thread.run(Thread.java:748)
+</span></span><span class="line"><span class="cl">&#34;线程AAA&#34;:
+</span></span><span class="line"><span class="cl">    at com.github.springcloud.service.ThreadHolderLock.run(MainTest.java:35)
+</span></span><span class="line"><span class="cl">    - waiting to lock &lt;0x000000076af2d5c0&gt; (a java.lang.String)
+</span></span><span class="line"><span class="cl">    - locked &lt;0x000000076af2d588&gt; (a java.lang.String)
+</span></span><span class="line"><span class="cl">    at java.lang.Thread.run(Thread.java:748)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Found 1 deadlock.
+</span></span></code></pre></div></li>
+</ol>
+<h3 id="解决方案-1">解决方案</h3>
+<h4 id="使用资源有序分配法避免死锁">使用资源有序分配法避免死锁</h4>
+<p>想要如何避免死锁，就要弄清楚死锁出现的原因，造成死锁必须达成的4个条件：</p>
+<ul>
+<li>互斥条件：一个资源每次只能被一个线程使用。例如，如果线程 A 已经持有的资源，不能再同时被线程 B 持有，如果线程 B 请求获取线程 A 已经占用的资源，那线程 B 只能等待，直到线程 A 释放了资源。</li>
+<li>请求与保持条件：一个线程因请求资源而阻塞时，对已获得的资源保持不放。例如，当线程 A 已经持有了资源 1，又想申请资源 2，而资源 2 已经被线程 C 持有了，所以线程 A 就会处于等待状态，但是线程 A 在等待资源 2 的同时并不会释放自己已经持有的资源 1。</li>
+<li>不剥夺条件：线程已获得的资源，在未使用完之前，不能强行剥夺。例如，当线程A已经持有了资源 ，在自己使用完之前不能被其他线程获取，线程 B 如果也想使用此资源，则只能在线程 A 使用完并释放后才能获取。</li>
+<li>循环等待条件：若干线程之间形成一种头尾相接的循环等待资源关系。比如，线程 A 已经持有资源 2，而想请求资源 1， 线程 B 已经获取了资源 1，而想请求资源 2，这就形成资源请求等待的环。</li>
+</ul>
+<p>避免死锁的产生就只需要破环其中一个条件就可以，最常见的并且可行的就是使用资源有序分配法，来破循环等待条件。
+资源有序分配法指的是，线程 A 和 线程 B 获取资源的顺序要一样，当线程 A 先尝试获取资源 A，然后尝试获取资源 B 的时候，线程 B 同样也是先尝试获取资源 A，然后尝试获取资源 B。也就是说，线程 A 和 线程 B 总是以相同的顺序申请自己想要的资源。
+给资源分配一个全局的唯一编号，进程必须按资源编号的顺序请求资源。这种方法可以避免循环等待，从而防止死锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Resource</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Resource</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Process</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="w"> </span><span class="n">resources</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Process</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">resources</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">resources</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquireResources</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 模拟处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">releaseResources</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">acquireResources</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Resource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired Resource &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">resource</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">releaseResources</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Resource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; released Resource &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">resource</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ResourceOrderingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource1</span><span class="p">,</span><span class="w"> </span><span class="n">resource2</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource2</span><span class="p">,</span><span class="w"> </span><span class="n">resource3</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource3</span><span class="p">,</span><span class="w"> </span><span class="n">resource1</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process3</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用银行家算法避免死锁">使用银行家算法避免死锁</h4>
+<p><img alt="银行家算法" src="/iblog/posts/annex/images/essays/%E9%93%B6%E8%A1%8C%E5%AE%B6%E7%AE%97%E6%B3%95.png"></p>
+<p>银行家算法：一个避免死锁的著名算法，是由艾兹格·迪杰斯特拉在1965年为T.H.E系统设计的一种避免死锁产生的算法。它以银行借贷系统的分配策略为基础，判断并保证系统的安全运行。</p>
+<p>在银行中，客户申请贷款的数量是有限的，每个客户在第一次申请贷款时要声明完成该项目所需的最大资金量，在满足所有贷款要求时，客户应及时归还。银行家在客户申请的贷款数量不超过自己拥有的最大值时，都应尽量满足客户的需要。通过判断借贷是否安全，然后决定借不借。
+举例，现有公司B、公司A、公司T，想要从银行分别贷款70亿、40亿、50亿，假设银行只有100亿供放贷，如果借不到企业最大需求的钱，钱将不会归还，怎么才能合理的放贷？</p>
+<table>
+<thead>
+<tr>
+<th>公司</th>
+<th>最大需求</th>
+<th>已借走</th>
+<th>最多还借</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>B</td>
+<td>70</td>
+<td>20</td>
+<td>50</td>
+</tr>
+<tr>
+<td>A</td>
+<td>40</td>
+<td>10</td>
+<td>30</td>
+</tr>
+<tr>
+<td>T</td>
+<td>50</td>
+<td>30</td>
+<td>20</td>
+</tr>
+</tbody>
+</table>
+<p>此时公司B、A、T已经从银行借走60亿，银行还剩40亿。此时银行可放贷金额组合：</p>
+<ul>
+<li>借给公司B10亿、公司A10亿、公司T20亿，等待公司T还钱再将10亿借给公司A，等待公司A还钱，再将钱借给公司B；</li>
+<li>借给公司T20亿，等公司T还钱再将钱借给公司A，等待公司A还钱再将钱借给公司B；</li>
+<li>借给公司A10亿，等待公司A还钱再将钱借给公司T，公司T还钱再将钱借给公司B；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Banker</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="p">;</span><span class="w">  </span><span class="c1">// 系统可用资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="p">;</span><span class="w">  </span><span class="c1">// 每个进程的最大资源需求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">allocation</span><span class="p">;</span><span class="w"> </span><span class="c1">// 每个进程当前已分配的资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">need</span><span class="p">;</span><span class="w">      </span><span class="c1">// 每个进程剩余的资源需求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Banker</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">available</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">maximum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">numProcesses</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">numResources</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">allocation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">numProcesses</span><span class="o">][</span><span class="n">numResources</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">need</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">numProcesses</span><span class="o">][</span><span class="n">numResources</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">numProcesses</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">numResources</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">need</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// 初始时，Need等于Maximum</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 请求资源的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">requestResources</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isRequestValid</span><span class="p">(</span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="n">request</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 请求不合法，拒绝请求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 试探性分配</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">allocation</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 安全性检查</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">safe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">isSafeState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">safe</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果不安全，恢复试探性分配前的状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">allocation</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">safe</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isRequestValid</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">request</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 请求超出需求或可用资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isSafeState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">work</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">finish</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">allocation</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">found</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">allocation</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">finish</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">canProceed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">work</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">need</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">work</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">canProceed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">canProceed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">work</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">work</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">allocation</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">finish</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">found</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">found</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">finish</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">f</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 存在未完成的进程，系统不安全</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w"> </span><span class="c1">// 所有进程都完成，系统安全</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>调用示例</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BankerExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Banker</span><span class="w"> </span><span class="n">banker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Banker</span><span class="p">(</span><span class="n">available</span><span class="p">,</span><span class="w"> </span><span class="n">maximum</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">request1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 1 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">request2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 2 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">request3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 3 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用-trylock-进行超时锁定">使用 tryLock 进行超时锁定</h4>
+<p>使用 <code>java.util.concurrent.locks.ReentrantLock</code> 的 <code>tryLock</code>方法可以尝试获取锁，并设置超时时间，避免长时间等待造成的死锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kn">import</span><span class="w"> </span><span class="nn">java.util.concurrent.locks.Lock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kn">import</span><span class="w"> </span><span class="nn">java.util.concurrent.locks.ReentrantLock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kn">import</span><span class="w"> </span><span class="nn">java.util.concurrent.TimeUnit</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Process</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Process</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock1</span><span class="p">.</span><span class="na">tryLock</span><span class="p">(</span><span class="n">50</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock2</span><span class="p">.</span><span class="na">tryLock</span><span class="p">(</span><span class="n">50</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired both locks&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="c1">// 模拟处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">lock2</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">lock1</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 等待一段时间再重试</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">50</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TryLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">,</span><span class="w"> </span><span class="n">lock1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="内存泄露">内存泄露</h2>
+<p>Java虚拟机是使用引用计数法和可达性分析来判断对象是否可回收，本质是判断一个对象是否还被引用，如果没有引用则回收。
+内存泄露是指，程序中己动态分配的堆内存由于某种原因程序未释放或无法释放，造成系统内存的浪费，导致程序运行速度减慢甚至系统崩溃等严重后果。
+简单来说，就是应该被垃圾回收的对象没有回收掉，导致占用的内存越来越多，最终导致内存溢出。</p>
+<p>内存泄露主要原因：</p>
+<ul>
+<li>在内存中加载过大的数据，例如从数据库取出过多数据；</li>
+<li>资源未关闭造成的内存泄漏；</li>
+<li>变量不合理的作用域，使用完毕，如果没有及时的赋值为null，则会造成内存泄露；</li>
+<li>长生命周期的对象中引用短生命周期对象，很可能会出现内存泄露；</li>
+</ul>
+<p>举个例子，创建的连接不再使用时，需要调用 close 方法关闭连接，只有连接被关闭后，GC 才会回收对应的对象（Connection，Statement，ResultSet，Session）。忘记关闭这些资源会导致持续占有内存，无法被 GC 回收。
+这样就会导致内存泄露，最终导致内存溢出。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MemoryLeak</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">try</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Class</span><span class="p">.</span><span class="na">forName</span><span class="p">(</span><span class="s">&#34;com.mysql.jdbc.Driver&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="n">DriverManager</span><span class="p">.</span><span class="na">getConnection</span><span class="p">(</span><span class="s">&#34;url&#34;</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Statement</span><span class="w"> </span><span class="n">stmt</span><span class="w"> </span><span class="o">=</span><span class="n">conn</span><span class="p">.</span><span class="na">createStatement</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">ResultSet</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">=</span><span class="n">stmt</span><span class="p">.</span><span class="na">executeQuery</span><span class="p">(</span><span class="s">&#34;....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">){</span><span class="c1">//异常日志</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 1．关闭结果集 Statement</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 2．关闭声明的对象 ResultSet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 3．关闭连接 Connection</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="排查过程-2">排查过程</h3>
+<p>根据运维之前收集到的内存数据、GC 日志尝试判断哪里出现了问题。
+结果发现老年代的内存使用就算是发生 GC 也一直居高不下，而且随着时间推移也越来越高。</p>
+<p><img alt="内存泄漏问题-01" src="/iblog/posts/annex/images/essays/%E5%86%85%E5%AD%98%E6%B3%84%E6%BC%8F%E9%97%AE%E9%A2%98-01.png"></p>
+<p>使用<code>jstat -gc &lt;vmid&gt;</code> 查看GC垃圾回收统计信息，看Full GC后堆空间使用内存还持续增长，且有增长到Xmx设定值的趋势，基本可以肯定存在内存泄露。
+如果当前完全垃圾回收后内存增长到一个值之后，又能回落，总体上处于一个动态平衡，那么内存泄漏基本可以排除；也可以隔断时间抽取老年代占用内存情况，如果老年代占用情况持续上升也很有可能存在内存泄露的情况。</p>
+<h3 id="解决方案-2">解决方案</h3>
+<ol>
+<li>内存泄漏的主要表象就是内存不足，所以首先要看一下JVM启动参数中内存空间分配是否过小，如果是这种问题调整该参数即可；</li>
+<li>确定是否新部署或有新变更，首先需要确认是否在最近进行了新的部署或有其他相关的变更，例如代码更新、配置修改等。这些变更可能导致应用出现性能问题，特别是在高负载情况下；</li>
+<li>内存泄漏解决方案，最经典的就是用MAT工具分析dump文件，但如果dump文件巨大就不建议这样，可以使用其他方案，例如：重启、本地复现、<code>jmap -histo:live &lt;pid&gt;</code>在线进行分析等其他方案解决。</li>
+</ol>
+<p>使用MAT定位内存泄漏思路：</p>
+<ol>
+<li>打开MAT中histogram，找到堆内存中占用最大的对象，内存泄漏很有可能就是由大对象导致的；
+<img alt="MAT-01" src="/iblog/posts/annex/images/essays/MAT-01.png"></li>
+<li>由大对象找被哪些线程引用，查看内存占用最大的线程；
+<img alt="MAT-02" src="/iblog/posts/annex/images/essays/MAT-02.png">
+<img alt="MAT-03" src="/iblog/posts/annex/images/essays/MAT-03.png"></li>
+<li>从线程中的堆栈信息找到项目中自定义的包和对象，从而可定位到具体的代码；
+<img alt="MAT-04" src="/iblog/posts/annex/images/essays/MAT-04.png">
+<img alt="MAT-05" src="/iblog/posts/annex/images/essays/MAT-05.png"></li>
+</ol>
+<h2 id="jvm参数调优">JVM参数调优</h2>
+<p>JVM优化是到最后不得已才采用的手段，对JVM内存的系统级的调优主要的目的是减少GC的频率和Full GC的次数。
+JVM参数说明：https://www.oracle.com/java/technologies/javase/vmoptions-jsp.html</p>
+<p>理想的情况下，一个Java程序使用JVM的默认设置也可以运行得很好，所以一般来说，没有必要设置任何JVM参数。然而，由于一些性能问题，我们需要设置合理的JVM参数。</p>
+<p>可以通过<code>java -XX:+PrintFlagsInitial</code> 命令查看JVM所有参数。</p>
+<p>常用参数：</p>
+<table>
+<thead>
+<tr>
+<th>参数</th>
+<th>含义</th>
+<th>描述</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>-Xms</td>
+<td>堆初始值</td>
+<td>Xmx和Xms设置为老年代存活对象的3-4倍，即FullGC之后的老年代内存占用的3-4倍</td>
+</tr>
+<tr>
+<td>-Xmx</td>
+<td>堆最大值</td>
+<td>为了防止自动扩容降低性能，建议将-Xms和-Xmx的值设置为相同值</td>
+</tr>
+<tr>
+<td>-XX:MaxHeapFreeRatio</td>
+<td>最大堆内存使用率</td>
+<td>默认70，当超过该比例会进行扩容堆，Xms=Xmx时该参数无效</td>
+</tr>
+<tr>
+<td>-XX:MinHeapFreeRatio</td>
+<td>最小堆内存使用率</td>
+<td>默认40，当低于该比例会缩减堆，Xms=Xmx时该参数无效</td>
+</tr>
+<tr>
+<td>-Xmn</td>
+<td>年轻代内存最大值</td>
+<td>年轻代设置的越大，老年代区域就会减少。一般不允许年轻代比老年代还大，因为要考虑GC时最坏情况，所有对象都晋升到老年代。建议设置为老年代存活对象的1-1.5倍，最大可以设置为-Xmx/2 。考虑性能，一般会通过参数 -XX:NewSize 设置年轻代初始大小。如果知道了年轻代初始分配的对象大小，可以节省新生代自动扩展的消耗。</td>
+</tr>
+<tr>
+<td>-XX:SurvivorRatio</td>
+<td>年轻代中两个Survivor区和Eden区大小比率</td>
+<td>例如： -XX:SurvivorRatio=10 表示伊甸园区是幸存者其中一个区大小的10倍，所以,伊甸园区占新生代大小的10/12, 幸存区From和幸存区To 每个占新生代的1/12</td>
+</tr>
+<tr>
+<td>-XX:NewRatio</td>
+<td>年轻生代和老年代的比率</td>
+<td>例如：-XX:NewRatio=3 指定老年代/新生代为3/1. 老年代占堆大小的 3/4 ，新生代占 1/4 。如果针对新生代,同时定义绝对值和相对值,绝对值将起作用，建议将年轻代的大小为整个堆的3/8左右。</td>
+</tr>
+<tr>
+<td>-XX:+HeapDumpOnOutOfMemoryError</td>
+<td>让JVM在发生内存溢出时自动的生成堆内存快照</td>
+<td>可以通过-XX:HeapDumpPath=path参数将生成的快照放到指定路径下</td>
+</tr>
+<tr>
+<td>-XX:OnOutOfMemoryError</td>
+<td>当内存溢发生时可以执行一些指令</td>
+<td>比如发个E-mail通知管理员或者执行一些清理工作，执行脚本</td>
+</tr>
+<tr>
+<td>-XX:ThreadStackSize</td>
+<td>每个线程栈最大值</td>
+<td>栈设置太大，会导致线程创建减少，栈设置小，会导致深入不够，深度的递归会导致栈溢出，建议栈深度设置在3000-5000k。</td>
+</tr>
+<tr>
+<td>-XX:MetaspaceSize</td>
+<td>初始化的元空间大小</td>
+<td>如果元空间大小达到了这个值，就会触发Full GC为了避免频繁的Full GC，建议将- XX：MetaspaceSize设置较大值。如果释放了空间之后，元空间还是不足，那么就会自动增加MetaspaceSize的大小</td>
+</tr>
+<tr>
+<td>-XX:MaxMetaspaceSize</td>
+<td>元空间最大值</td>
+<td>默认情况下，元空间最大的大小是系统内存的大小，元空间一直扩大，虚拟机可能会消耗完所有的可用系统内存。</td>
+</tr>
+</tbody>
+</table>
+<p>示例参数：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"># 必备
+</span></span><span class="line"><span class="cl">-XX:+PrintGCDetails 
+</span></span><span class="line"><span class="cl">-XX:+PrintGCDateStamps 
+</span></span><span class="line"><span class="cl">-XX:+PrintTenuringDistribution 
+</span></span><span class="line"><span class="cl">-XX:+PrintHeapAtGC 
+</span></span><span class="line"><span class="cl">-XX:+PrintReferenceGC 
+</span></span><span class="line"><span class="cl">-XX:+PrintGCApplicationStoppedTime
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"># 可选
+</span></span><span class="line"><span class="cl">-XX:+PrintSafepointStatistics 
+</span></span><span class="line"><span class="cl">-XX:PrintSafepointStatisticsCount=1
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"># GC日志输出的文件路径
+</span></span><span class="line"><span class="cl">-Xloggc:/path/to/gc-%t.log
+</span></span><span class="line"><span class="cl"># 开启日志文件分割
+</span></span><span class="line"><span class="cl">-XX:+UseGCLogFileRotation 
+</span></span><span class="line"><span class="cl"># 最多分割几个文件，超过之后从头文件开始写
+</span></span><span class="line"><span class="cl">-XX:NumberOfGCLogFiles=14
+</span></span><span class="line"><span class="cl"># 每个文件上限大小，超过就触发分割
+</span></span><span class="line"><span class="cl">-XX:GCLogFileSize=100M
+</span></span></code></pre></div><p>何时调优：</p>
+<ol>
+<li>Full GC 次数频繁；</li>
+<li>GC 停顿时间过长；</li>
+<li>应用出现OutOfMemory 等内存异常；</li>
+<li>堆内存持续上涨达到设置的最大内存值；</li>
+</ol>
+<p>调优原则：</p>
+<ol>
+<li>多数导致GC问题的Java应用，都不是因为我们参数设置错误，而是代码问题；</li>
+<li>在实际使用中，分析GC情况优化代码比优化JVM参数更好；</li>
+<li>减少创建对象的数量、减少使用全局变量和大对象；</li>
+</ol>
+<p>调优思路：</p>
+<ol>
+<li>分析GC日志及dump文件，判断是否需要优化，确定瓶颈问题点。如果各项参数设置合理，系统没有超时日志出现，GC频率不高，GC耗时不高，那么没有必要进行GC优化，如果GC时间超过1-3秒，或者频繁GC，则必须优化；</li>
+<li>确定JVM调优目标。如果内存分配过大或过小，或者采用的GC收集器比较慢，则应该优先调整这些参数，并且先找1台或几台机器进行测试，然后比较优化过的机器和没有优化的机器的性能对比，并有针对性的做出最后选择；</li>
+<li>不断的分析和调整，直到找到合适的JVM参数配置；</li>
+</ol>
+<h2 id="线上接口慢">线上接口慢</h2>
+<h3 id="定位问题">定位问题</h3>
+<p>首先要定位是哪里慢，定位接口哪一个环节比较慢，性能瓶颈在哪里，可以使用应用性能监控工具(APM)定位问题。常见工具: skywalking、pinpoint、cat、zipkin。</p>
+<p>如果应用程序没有接入APM，可以在生产环境装一下arthas，利用trace接口方法和火焰图，大概能分析是那一块比较慢，定位能力稍微有点粗糙，亦可以利用程序中的告警日志定位问题。</p>
+<h3 id="解决方案-3">解决方案</h3>
+<p>如果已经定位到具体是哪里的问题了，那么就可以进行解决，如果是最新的功能引起的，那么最快的办法就是回退版本。
+以下是几种常见接口慢的情况。</p>
+<h4 id="数据库慢sql">数据库慢sql</h4>
+<p>如果是数据库sql慢，可以使用执行计划去分析一下，常见sql慢的几种情况：</p>
+<ul>
+<li>锁表；先把锁表的sqlkill一波，在分析具体原因；</li>
+<li>未加索引；添加索引，有可能会锁表，引发一系列问题，需要综合评估；</li>
+<li>索引失效；分析索引失效原因，如：索引列区分度（值大都相同）很低、索引列大量空值、对所索引列加方法转换等；</li>
+<li>小表驱动大表；在连接查询时尽量过滤数据，使用小表驱动大表，使笛卡尔积尽量小一些；</li>
+<li>sql太复杂；join超过3张表或者子查询比较多，建议拆分为多个sql，接口间相互调用；比如先从某个著接口查询某个表数据，然后关联字段作为条件从另一个表查询，进行内存拼接；</li>
+<li>返回的数据量数据太多；当超过数据库一定限制的时候返回大量数据就会很慢，可以使用分页多批次完成，针对访问量不多的接口可使用多线程批量查询；</li>
+<li>单表数据量太大；（mysql超500w较慢）如果单表数据量较大，考虑在数据库设计做文章，如：分片分库、利用es存储等；</li>
+</ul>
+<h4 id="调用第三方接口慢">调用第三方接口慢</h4>
+<ul>
+<li>设置合理的超时时间；调用第三方接口一定要设置合理的超时时间，在设置时一定要大于调用接口的平均相应时间；</li>
+<li>第三方接口大量超时；可以集成sentinel或hystrix限流熔断框架，防止第三方接口拖垮自己的接口（兜底逻辑）；</li>
+<li>事务型操作根据实际情况决定是否采用补偿机制（本地消息表）；比如新增、修改等操作要考虑对方接口是否支持幂等，防止超发；</li>
+<li>循环调用，改为单次批量调用，减少IO损耗；如：调用根据id查询单条数据的接口，可优化为批量查询接口；</li>
+<li>缓存查询结果；考虑当前查询结果是否能做缓存，如用户信息等短时间内不会变化的信息，根据业务形态来决定；</li>
+</ul>
+<h4 id="中间件慢">中间件慢</h4>
+<ul>
+<li>redis慢：是否有大key、热key，可接入hotkeys监控；针对热key可以使用本地缓存来抗，针对大key可以将其拆分，采用set结构的sismember等方法</li>
+<li>kafka：生产端慢：可以使用堵塞队列接收，批量丢消息；消费端慢：消费端慢会造成消息积压，可以扩分区、增加消费节点、增加消费线程，用数据机构接受批量写入库；</li>
+</ul>
+<h4 id="程序逻辑慢">程序逻辑慢</h4>
+<ul>
+<li>非法校验逻辑前置；避免无用数据穿透小号系统资源，减少无效调用；</li>
+<li>循环调用改为单次批量调用；在查询数据库或调用第三方接口，能批量就批量，数据在内存组装处理；</li>
+<li>同步调用改为异步调用；在接口没有相互依赖的关系的时候可以将其优化为异步查询；</li>
+<li>非核心逻辑剥离；将接口的大事务拆分为小事务，一些非核心逻辑可以异步处理，可以使用mq异步解耦；</li>
+<li>线程池合理设置参数；不要使用JDK默认参数，如果在高并发的情况下容易OOM，线程池满了以后要重写拒绝策略，考虑告警加数据持久化处理；</li>
+<li>锁合理设置；本地读写锁设计使用不合理，要控制锁的力度，尽量小一些；分布式锁合理使用防止热key；</li>
+<li>优化GC参数；考虑GC是否频繁，调整GC算法，新生代老年代比例，根据长时间观察可以设置出来；</li>
+<li>只打印必要日志；当并发量比较高的时候打印日志也会损耗性能，所以日志应加上开关能不打就不打；</li>
+</ul>
+<h4 id="架构优化">架构优化</h4>
+<ul>
+<li>高并发读逻辑走redis，尽可能不要穿透到DB；redis查询不到也不要查DB，可通过定时任务，MQ写入redis。尽量不要把风险给DB，DB如果挂了整个应用就用不了了；</li>
+<li>设计写逻辑数据，尽量异步、批量处理、分库分表提升写入性能；</li>
+<li>接口接入限流熔断兜底；</li>
+<li>接入监控告警；error日志告警、接口慢查询或者不可用或限流熔断告警、DB告警、中间件告警、应用系统告警等；</li>
+<li>接口需要加动态配置开关；能够快速切断流量或降级某些非核心服务调用；</li>
+<li>设计程序自愈能力；比如如果数据有问题，用配置好的程序逻辑自动去修复；</li>
+</ul>
+<h2 id="transactional">@Transactional</h2>
+<p><code>@Transactional</code>是开发过程中使用比较频繁的注解，但是使用不当也会导致事务失效甚至导致一些其他问题，下面是使用<code>@Transactional</code>遇到的几种问题。</p>
+<h3 id="transactional失效情况">@Transactional失效情况</h3>
+<ol>
+<li>如果某个方法是非public的，那么<code>@Transactional</code>就会失效。因为事务的底层是利用<code>cglib</code>代理实现，<code>cglib</code>是基于父子类来实现的，子类是不能重载父类的private方法，所以无法很好利用代理，这种情况下会导致@Transactional失效；</li>
+<li>使用的数据库引擎不支持事务。因为Spring的事务调用的也是数据库事务的API，如果数据库都不支持事务，那么<code>@Transactional</code>注解也就失效了；</li>
+<li>添加了<code>@Transactional</code>注解的方法不能在同一个类中调用，否则会使事务失效。这是因为Spring AOP通过代理来管理事务，自调用不会经过代理；</li>
+<li><code>@Transactional</code> 注解属性 <code>propagation</code> 设置错误，若是错误的配置以下三种 <code>propagation</code>，事务将不会发生回滚：
+<ul>
+<li><code>TransactionDefinition.PROPAGATION_SUPPORTS</code>：如果当前存在事务，则加入该事务；如果当前没有事务，则以非事务的方式继续运行。</li>
+<li><code>TransactionDefinition.PROPAGATION_NOT_SUPPORTED</code>：以非事务方式运行，如果当前存在事务，则把当前事务挂起。</li>
+<li><code>TransactionDefinition.PROPAGATION_NEVER</code>：以非事务方式运行，如果当前存在事务，则抛出异常。</li>
+</ul>
+</li>
+<li><code>@Transactional</code>注解属性<code>rollbackFor</code>设置错误，<code>rollbackFor</code>可以指定能够触发事务回滚的异常类型。默认情况下，Spring仅在抛出未检查异常（继承自<code>RuntimeException</code>）时回滚事务。对于受检异常（继承自 <code>Exception</code>），事务不会回滚，除非明确配置了<code>rollbackFor</code>属性；</li>
+<li>异常被捕获了，导致<code>@Transactional</code>失效。当事务方法中抛出一个异常后，应该是需要表示当前事务需要<code>rollback</code>，如果在事务方法中手动捕获了该异常，那么事务方法则会认为当前事务应该正常提交，此时就会出现事务方法中明明有报错信息表示当前事务需要回滚，但是事务方法认为是正常，出现了前后不一致，也是因为这样就会抛出<code>UnexpectedRollbackException</code>异常；</li>
+</ol>
+<p>我们在使用<code>@Transactional</code>时，要避免出现上述情况，以确保 <code>@Transactional</code> 注解正确生效，从而实现事务管理的可靠性和一致性。</p>
+<h3 id="transactional遇到锁">@Transactional遇到锁</h3>
+<p>看到这么一段代码，原来当Transactional碰到锁，有个大坑，觉得很有意思，于是便记录下来。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ServiceOne</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 设置一把可重入的公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Transactional</span><span class="p">(</span><span class="n">rollbackFor</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Exception</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Result</span><span class="w">  </span><span class="nf">func</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">seckillId</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">userId</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行数据库操作——查询商品库存数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果 库存数量 满足要求 执行数据库操作——减少库存数量——模拟卖出货物操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>func</code>方法是原子操作，所以使用事务，为了解决并发访问的问题，用<code>lock</code>把整个代码包裹了起来，这么使用锁和事务，是会发生超卖问题的。</p>
+<p>在使用MySQL数据库的可重复读隔离机制，如果是高并发的情况下，假设真的就有多个线程同时调用<code>func</code>方法。
+要保证一定不能出现超卖的情况，那么就需要事务的开启与提交能完整的包裹在<code>lock</code>与<code>unlock</code>之间。</p>
+<p>为什么要保证事务的开启与提交，完整的包裹在<code>lock</code>与<code>unlock</code>之间呢？</p>
+<p>举个例子，假设现在库存就只有一个了，这个时候 A，B 两个线程来请求下单。A 请求先拿到锁，然后查询出库存为一，可以下单，走了下单流程，把库存减为 0 了。
+但是由于 A 先执行了 <code>unlock</code> 操作，而未提交事务，先释放了锁。B 线程看到后马上就冲过来拿到了锁，并执行了查询库存的操作。
+这个时候 A 线程还没来得及提交事务，所以 B 读取到的库存还是 1，如果程序没有做好控制，也走了下单流程，此时就造成了超卖。</p>
+<p>那怎么保证事务的开启与提交，完整的包裹在<code>lock</code>与<code>unlock</code>之间呢？</p>
+<p>先来了解一下事务的启动和结束时机，这里直接说结论。
+事务的启动时机，在执行到它们之后的第一个操作数据库表的语句，事务才算是真正启动。在上述示例代码中第一个SQL是在加锁之后执行的，所以先加锁再开启事务。
+事务的提交是在目标方法执行之后。具体代码可以参考：<code>TransactionAspectSupport.invokeWithTransaction</code>方法，从其中可以看出，<code>invocation.proceedWithInvocation</code> 是在<code>commitTransactionAfterReturning</code>前面的。</p>
+<p>所以怎样保证呢？对于声明式事务，解决办法是把锁加在方法外面。如果一定需要加在里面，也可以使用编程式事务。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">seckillId</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">userId</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">DefaultTransactionDefinition</span><span class="w"> </span><span class="n">definition</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultTransactionDefinition</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">definition</span><span class="p">.</span><span class="na">setIsolationLevel</span><span class="p">(</span><span class="n">TransactionDefinition</span><span class="p">.</span><span class="na">ISOLATION_REPEATABLE_READ</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">TransactionStatus</span><span class="w"> </span><span class="n">status</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">transactionManager</span><span class="p">.</span><span class="na">getTransaction</span><span class="p">(</span><span class="n">definition</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="c1">// 执行数据库操作——查询商品库存数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="c1">// 如果 库存数量 满足要求 执行数据库操作——减少库存数量——模拟卖出货物操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">transactionManager</span><span class="p">.</span><span class="na">commit</span><span class="p">(</span><span class="n">status</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">transactionManager</span><span class="p">.</span><span class="na">rollback</span><span class="p">(</span><span class="n">status</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ServiceOne</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 设置一把可重入的公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ServiceTwo</span><span class="w"> </span><span class="n">serviceTwo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Result</span><span class="w">  </span><span class="nf">func</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">seckillId</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">userId</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">serviceTwo</span><span class="p">.</span><span class="na">sellProduct</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ServiceTwo</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="nd">@Transactional</span><span class="p">(</span><span class="n">rollbackFor</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Exception</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sellProduct</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 执行数据库操作——查询商品库存数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 如果 库存数量 满足要求 执行数据库操作——减少库存数量——模拟卖出货物操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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\ No newline at end of file
diff --git a/blog-site/public/posts/codeguide/java-bugs/index.html b/blog-site/public/posts/codeguide/java-bugs/index.html
new file mode 100644
index 00000000..32749f19
--- /dev/null
+++ b/blog-site/public/posts/codeguide/java-bugs/index.html
@@ -0,0 +1,383 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
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+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>如何减少及解决bug ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="bug的起源: 1945年，一只小飞蛾钻进了计算机电路里，导致系统无法工作，一位名叫格蕾丝·赫柏的人把飞蛾拍死在工作日志上，写道：就是这个 bug(虫子)，害我们今" />
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+                        <h2 id="post_single_title">如何减少及解决bug</h2>
+                        <span id="post_page_title_date" class="date">2023.03.10</span>
+                        
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+                    <div class="post_content markdown"><blockquote>
+<p>bug的起源:
+1945年，一只小飞蛾钻进了计算机电路里，导致系统无法工作，一位名叫格蕾丝·赫柏的人把飞蛾拍死在工作日志上，写道：就是这个 bug(虫子)，害我们今天的工作无法完成——于是，bug一词成了电脑系统程序的专业术语，形容那些系统中的缺陷或问题。</p>
+</blockquote>
+<p>bug一词，是指“故障”、“缺陷”。了解软件开发的朋友都非常熟悉，程序员和测试人员更不用说，在工作中会常遇到。 作为一名开发人员，项目出现bug是避免不了的。无论你是一名初入职场的小白，还是拥有经验丰富的大佬，只要经常写代码，梳理业务逻辑，很难免不出bug。正所谓常在河边走，哪能不湿鞋。记得以前经常听人说，如果你没有把系统搞宕机过，就不是一名合格的CTO，成为一名出色的开发人员，经验都是一个一个积累起来的。
+所谓的bug指的是生产环境发现的问题;那么只要线上不发现问题，那就不是bug。之所以这么讲是因为一旦影响程序的正常使用便会影响公司的利益，公司利益被影响你自己的利益也会被影响;所以为了自己写程序的时候尽量多测试，将可能会应对到的情况想得全一点，减少bug的出现。</p>
+<p>程序员能为了减少bug的出现能做的可以从代码方面下手:</p>
+<ul>
+<li>在正式开发前，做好准备工作，先梳理一下业务逻辑，根据业务场景可以使用什么设计模式，是否需要缓存，列一下需要用到的框架等，尽量考虑的全面一些，考虑一下不同的情况;</li>
+<li>在编写代码的时候需要注意以下几点，供参考：
+<ul>
+<li>在关键的地方写注释，标注一些关键的信息;</li>
+<li>增加校验;如: 调用第三方程序或者使用一些中间件的时候，拿到结果不要着急使用，先做校验，这样可以很大程度上避免NPE的出现;</li>
+<li>当在程序某个功能下加一个非堵塞性功能的时候，需要考虑是否会影响到主流程的使用，有时候可能不经意的一个问题会将它的影响无限放大，随之而来的就是用户投诉，老板亏钱;</li>
+<li>当编写代码的时候尽量写一些简洁，清晰的代码，比如一个方法实现的功能较多，应把它拆开。如果代码变得易于维护起来那么bug的数量也会大大降低;</li>
+<li>尽量编写一些能测试的代码，将一个方法的职责做到最小，一个方法就干一件事情;</li>
+<li>当开发功能完成之后不要着急测试，先自己审查一下代码，确认哪些地方可以进行优化，之后再调试功能进行单元测试;</li>
+</ul>
+</li>
+<li>当开发完成之后一定要进行单元测试，这可以大大降低bug的数量; 测试的时候需要模拟线上的环境数据来测试新增或修复的功能，否则即使改完功能之后可能会由于请求次数或数据量巨大问题导致功能不能使用。</li>
+</ul>
+<p>除此之外，一方面可以借助一些工具来进行bug的规避，比如sonar，可以发现一些潜在的错误和问题。另一方面我们要不断学习和提高自己的编程技能，以提高代码质量和减少错误的发生。</p>
+<p>尽管这样bug这种东西还是不可避免的，我们只能减少bug而不能消除bug，没有人保证自己的程序一定是没有问题的。减少bug的出现只能多测多验证，哪怕单元测试通过都不能非常有效减少bug，因为受到写单元测试的人的思维角度限制，导致单元测试的片面性。</p>
+<p>关于bug的种类，最容易出现的bug是逻辑上的bug，如复杂庞大一点软件如果不是所有地方都熟悉就写代码是比较容易遗漏一些特殊情况的。除了逻辑上的bug外在开发中还有框架中存在的bug，但是这种bug是我们避免不了的。如2021年爆发的log4j堪称史诗级的bug。
+没什么好的办法可以提前避免掉，就多用一些稳定的框架吧，有apache就用apache，没有就优先使用fork，start高的，从概率上减少。</p>
+<p>一个人的力量毕竟有限必要的时候可以叫上同事，进行code review。</p>
+<p>因为bug是不可避免的，所以解决bug能力就显得尤为重要，程序员归根到底拼的是解决问题的能力。</p>
+<p>bug的解决思路:</p>
+<ul>
+<li>确认bug的存在，包括复现bug的步骤和现象;</li>
+<li>分析bug的根本原因，找到导致bug的代码或逻辑，一般通过日志查看一些栈的信息;</li>
+<li>修复bug的代码或逻辑，并重新测试确认修复成功;</li>
+<li>编写针对bug的单元测试，验证bug是否修复;</li>
+<li>记录bug修复的过程和结果，以备将来参考和验证;</li>
+</ul>
+<p>亲自复现问题，关注第一现场，确定是必现还是偶现; 区分是人的问题还是环境的问题；如果是人的问题，那是配置参数的问题还是代码逻辑的问题。如果是配置参数的问题，则通过对比正常运行的配置参数发现问题。
+如果是代码逻辑的问题，则通过commit的历史二分查找缩小出现问题的逻辑范围; 如果是机器的问题，确定是单机问题还是集群问题; 如果是单机问题，则替换机器，如果是集群问题则考虑升级硬件设备。</p>
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+    <footer class="footer">
+    <div id="footer_powered_by" class="powered_by">
+        <a href="https://varkai.com">Designed by VarKai,</a>
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+    </div>
+
+    <div id="footer_slogan" class="footer_slogan">
+        <span>from 2021</span>
+    </div>
+</footer>
+    <script src="http://localhost:1313/iblog/js/jquery-3.5.1.min.js"></script>
+<link href="http://localhost:1313/iblog/css/fancybox.min.css" rel="stylesheet">
+<script src="http://localhost:1313/iblog/js/fancybox.min.js"></script>
+<script src="http://localhost:1313/iblog/js/darkmode.js"></script>
+<script src="http://localhost:1313/iblog/js/zozo.js"></script>
+<script src="//cdn1.lncld.net/static/js/3.0.4/av-min.js"></script>
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+<script src="http://localhost:1313/iblog/js/html2canvas.js"></script>
+<script src="http://localhost:1313/iblog/js/utils.js"></script>
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+<script src="http://localhost:1313/iblog/js/fastsearch.js"></script>
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+
+<script>
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+</html>
\ No newline at end of file
diff --git a/blog-site/public/posts/codeguide/java-design/index.html b/blog-site/public/posts/codeguide/java-design/index.html
new file mode 100644
index 00000000..e7a3de36
--- /dev/null
+++ b/blog-site/public/posts/codeguide/java-design/index.html
@@ -0,0 +1,598 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>如何做好程序设计功能 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="功能设计流程图 与外部系统交互、本系统模块之间流程，比较好用的画圈软件draw .io或在线的process on 数据库设计 从DDD角度界限上下文、ER图、评审表结构设" />
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+
+    
+    
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+
+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
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+            
+        <ul class="nav">
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+            
+            <li class="nav-item">
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+                    功能设计流程图
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e6%8d%ae%e5%ba%93%e8%ae%be%e8%ae%a1">
+                    数据库设计
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+            </li>
+            
+            
+        </ul>
+        
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+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%ad%98%e8%ae%be%e8%ae%a1">
+                    缓存设计
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#job%e8%ae%be%e8%ae%a1">
+                    job设计
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        
+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%a5%e5%8f%a3%e8%ae%be%e8%ae%a1">
+                    接口设计
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%9b%91%e6%8e%a7%e8%ae%be%e8%ae%a1">
+                    监控设计
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%a2%84%e6%a1%88%e8%ae%be%e8%ae%a1">
+                    预案设计
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
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+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
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+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
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+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
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+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
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+                
+                
+                <span id="sys_function" class="sys_function display_none">
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+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">如何做好程序设计功能</h2>
+                        <span id="post_page_title_date" class="date">2022.08.02</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="功能设计流程图">功能设计流程图</h2>
+<p>与外部系统交互、本系统模块之间流程，比较好用的画圈软件draw .io或在线的process on</p>
+<h2 id="数据库设计">数据库设计</h2>
+<p>从DDD角度界限上下文、ER图、评审表结构设计是否合理，表的关联关系是否合理、是否创建索引、是否大数据量表考虑放到分片库以及分片字段设计</p>
+<h2 id="缓存设计">缓存设计</h2>
+<ul>
+<li>缓存结构是否合理 redis结构选择(string、hash、 list、set)：
+<ul>
+<li>对于C端高并发接口，hash结构要慎重用，key不能用固定的key，防止key倾 斜，可以采用string结构，value尽可能压缩下，比如 {&ldquo;groupId:&rdquo;:&ldquo;536363737&rdquo;， &ldquo;groupId&rdquo;:&ldquo;989898989&rdquo;}改为&quot;536363737#989898989&quot;，大大节省redis空间。</li>
+<li>对于数据量很大，单条valve报文很大的业务，如果经常判断某个值是否存在，可以考虑采用set结构，利用sismember方法，时间复杂度O(1)</li>
+</ul>
+</li>
+<li>缓存过期时间是否合理：不能怕脑袋胡乱给一个时间，如果存放的数量，过期时间一定要给短一些，比如2日分钟或半小时，否则增长很长，打爆redis</li>
+<li>缓存是否设计考虑预热和重建机制</li>
+<li>缓存中尽可能不能使用delete命令；delete会阻塞redis，特别是存放数量很大的hash、set、list， 容易阻塞redis，引1发事故，替换方案：expire -1</li>
+<li>是否是否设计二级缓存；本地缓存+分布式缓存，实现方式caffine或quavatredis，对于数据量不大热点数据（一般1W条以下，单条报文10kb以下，比如网点数据、航线数据)可以放本地缓存，这些热点数据查询非常频繁，容易造成redis倾斜，本地缓存可以抗这种高井发流量.</li>
+<li>防穿透处理
+<ul>
+<li>提供c端的接口，查询不到数据，尽可能不要穿透到数据库，防止打爆数据库，查不到一定记得打印告營日志，及时人工千预</li>
+<li>提前将数据预热到缓存中(系统启动预热或者运营后台有手动刷新缓存按钮或者有个job刷缓存)</li>
+</ul>
+</li>
+</ul>
+<h2 id="job设计">job设计</h2>
+<ul>
+<li>job逻辑要考虑幂等设计</li>
+<li>job逻辑尽可能轻量级，不要太重，导致执行逻辑很久(如果确实逻辑比较复杂，可以分拆job或者从代码层面优化，例如：分批井行处理、减少单次处理数据〕</li>
+<li>构建数据到缓存类似的job，尽可能选择时间在晚上12点以后，尽量不要白天进行，因为白天流量很大，重建缓存容易引起接口抖动</li>
+<li>对于定时执行的job，设计执行时间的时候，要慎重考虑线上整个job执行的时间，根据这个时间配置cron表达式，不要拍脑袋随意设置，</li>
+<li>不然本次job没执行完，下一次job执行的时候容易错过。</li>
+<li>对于大表数据（百万、千万甚至亿级），可以利用xxjob、saturn等分布式调度框架的分片处理能力，并行刷数据，提供处理速度。</li>
+</ul>
+<h2 id="接口设计">接口设计</h2>
+<ul>
+<li>高并发接口必须在测试环境压测，清楚的知道接口支持的QPS，另外根据压测报告给出的优化建议，及时调整线上的配置、代码优化。</li>
+<li>提供给C端的接口，要清楚曝光位省、然后根据接口可能预计调用的流量、压测的接口最大支持的QPS，决定是否扩容、是否需要限流及兜底逻镇、是否熔断</li>
+<li>程序中涉及的异常信息，及时配置错误监控告警，遇事做到心中有数。</li>
+<li>对于业务关键位置，及时打印info级别的业务追踪日志，如果是高并发接口，要做好开关，能秒级关闭，因为打印日志也特别耗性能。</li>
+<li>程序设计方面，高井发接口，尽可能使用缓存、能异步就异步 （一般用mq，不要用多线程异步）、 尽可能采用无锁设计防止线程Lock CPU冲高，批量写库</li>
+<li>接口前置逻铜提前，尽早过滤掉不合规運银，缩短接口整个调用链路时长，提升接口整体吞吐量。</li>
+<li>接口要考虑无状态设计、昇等设计(考虑分布式锁唯—key)、安全设计(接口方法签名、是否接第三方防刷服务判断是否黑产用户）
+<blockquote>
+<p>无状态服务：客户端的每次请求必须具备自描述信息，通过这些信息识别客户端身份。服务端不保存任何客户端请求者信息
+有状态服务: 即服务端需要记录每次会话的客户端信息，从而识别客户端身份，根据用户身份进行请求的处理，典型的设计如 tomcat 中的 session</p>
+</blockquote>
+</li>
+<li>对第三方服务做到零信任，考虑降级、熔断，与业务方确认好兜底逻辑处理。</li>
+<li>工具类尽可能使用apache、google等出的、 一些github小众的开源框架很多在高井发场最有bug和性能瓶颈。</li>
+<li>接口的时间复杂度，部分在设计的时候尽可能保证是0 (1），例如调用第三方接口，for循环调用的，是否可以提到缩环外，传多个id批量调用一次，时间复杂度从0（n）降为0(1)</li>
+</ul>
+<h2 id="监控设计">监控设计</h2>
+<ul>
+<li>核心接西做好监控，例如：调用量上涨/下跌80%、接口健康度监控 （5分钟error超过100次、5分钟接口超过1s 100日次、5分钟不可用次数超过1000次）</li>
+<li>应用监控，例如：应用cpu、内存层、gc、繁忙线程数、数据库连接池连接数监控告警</li>
+<li>中间件监控，例如：redis可用性、cpu-内存-流量-大key-热key-慢查询监控、kafka可用性-消息积压情况-丢失率监控告警</li>
+<li>数据库监控，例如：mysql cpu、慢sql监控告警</li>
+<li>业务监控，例如：发券量暴涨或暴跌、活动注册人数同比或环比异常</li>
+</ul>
+<h2 id="预案设计">预案设计</h2>
+<p>设计预案减少损失</p>
+<ul>
+<li>设计全局开关（系统接近不可用，通过配置中心全局开关快速切断接口流量，保证系統可用）</li>
+<li>遇到系统故障，非核心功能通过配置中心开关下线，保证整体服务可用</li>
+<li>应用能自动扩容（这里就要求应用做到无状态设计，比如：我们之间有一些应用有调用加密机，但是新应用节点需要申请白名单，这种设计方式就没法自动扩容</li>
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+    <footer class="footer">
+    <div id="footer_powered_by" class="powered_by">
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+
+    <div id="footer_slogan" class="footer_slogan">
+        <span>from 2021</span>
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+<script src="http://localhost:1313/iblog/js/fancybox.min.js"></script>
+<script src="http://localhost:1313/iblog/js/darkmode.js"></script>
+<script src="http://localhost:1313/iblog/js/zozo.js"></script>
+<script src="//cdn1.lncld.net/static/js/3.0.4/av-min.js"></script>
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+<script src="http://localhost:1313/iblog/js/html2canvas.js"></script>
+<script src="http://localhost:1313/iblog/js/utils.js"></script>
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+<script src="http://localhost:1313/iblog/js/fastsearch.js"></script>
+<script src="http://localhost:1313/iblog/js/fuse.js"></script>
+
+
+<script>
+    new Darkmode({
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+        bottom: 'unset', 
+        
+        time: '0.15s', 
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\ No newline at end of file
diff --git a/blog-site/public/posts/detailed/cas-detail/index.html b/blog-site/public/posts/detailed/cas-detail/index.html
new file mode 100644
index 00000000..3b19e64f
--- /dev/null
+++ b/blog-site/public/posts/detailed/cas-detail/index.html
@@ -0,0 +1,832 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>CAS详解 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="CAS CAS全称为Compare and Swap被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
+    
+
+	
+
+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cas">
+                    CAS
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e7%a4%ba%e4%be%8b">
+                    使用示例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#unsafe">
+                    Unsafe
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86">
+                    实现原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cas%e9%97%ae%e9%a2%98">
+                    CAS问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
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+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
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+                        <h2 id="post_single_title">CAS详解</h2>
+                        <span id="post_page_title_date" class="date">2020.04.04</span>
+                        
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+                    <div class="post_content markdown"><h2 id="cas">CAS</h2>
+<p>CAS全称为<code>Compare and Swap</code>被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更新为新值。
+CAS操作是原子的，这意味着在多个线程同时执行CAS操作时，不会发生竞争条件。</p>
+<h3 id="使用示例">使用示例</h3>
+<p><code>java.util.concurrent.atomic</code>并发包下的所有原子类都是基于CAS来实现的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">atomicInteger</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">result</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;更新成功，当前值：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;更新失败，当前值：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>CAS一些常见使用场景：</p>
+<ul>
+<li>使用CAS实现线程安全的计数器，避免传统锁的开销。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">oldValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">counter</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">counter</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">oldValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">newValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>使用CAS来实现无锁队列、栈等数据结构。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASQueue</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">enqueue</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">dequeue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentHead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentHead</span><span class="p">,</span><span class="w"> </span><span class="n">nextNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在数据库中，CAS可以用于实现乐观锁机制，避免长时间持有锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">OptimisticLocking</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">version</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">updateWithOptimisticLock</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedVersion</span><span class="p">,</span><span class="w"> </span><span class="n">Runnable</span><span class="w"> </span><span class="n">updateTask</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">currentVersion</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentVersion</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedVersion</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">updateTask</span><span class="p">.</span><span class="na">run</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentVersion</span><span class="p">,</span><span class="w"> </span><span class="n">currentVersion</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getVersion</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OptimisticLocking</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">OptimisticLocking</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">updateTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Performing update&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">version</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">getVersion</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">success</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">updateWithOptimisticLock</span><span class="p">(</span><span class="n">version</span><span class="p">,</span><span class="w"> </span><span class="n">updateTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">success</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Update successful.&#34;</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Update failed.&#34;</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在实现线程池时，CAS可以用于安全地管理线程状态和任务队列。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASThreadPool</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">submitTask</span><span class="p">(</span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Runnable</span><span class="w"> </span><span class="nf">getTask</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentHead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentHead</span><span class="p">,</span><span class="w"> </span><span class="n">nextNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="unsafe">Unsafe</h3>
+<p><code>Unsafe</code>是CAS的核心类，Java无法直接访问底层操作系统，而是通过<code>native</code>方法来访问。不过尽管如此，JVM还是开了一个后门，JDK中有一个类<code>Unsafe</code>，它提供了硬件级别的原子操作。</p>
+<p><code>Unsafe</code>类位于<code>sun.misc</code>包中，它提供了访问底层操作系统的特定功能，如直接内存访问、CAS 操作等。
+由于其提供了直接操作内存的能力，使用不当可能导致内存泄漏、数据损坏等问题，应谨慎使用。
+<code>Unsafe</code>类包含了许多不安全的操作，所以它并不是Java标准的一部分，而且在Java9开始已经标记为受限制的API。</p>
+<p>Java中CAS操作的执行依赖于<code>Unsafe</code>类的方法，<code>Unsafe</code>类中的所有方法都是<code>native</code>修饰的，也就是说<code>Unsafe</code>类中的方法都直接调用操作系统底层资源执行相应任务。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">UnsafeExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Unsafe</span><span class="w"> </span><span class="n">unsafe</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Field</span><span class="w"> </span><span class="n">field</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Unsafe</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;theUnsafe&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">field</span><span class="p">.</span><span class="na">setAccessible</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">unsafe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Unsafe</span><span class="p">)</span><span class="w"> </span><span class="n">field</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">valueOffset</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">objectFieldOffset</span><span class="p">(</span><span class="n">UnsafeExample</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;value&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">current</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">unsafe</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="实现原理">实现原理</h3>
+<p>以<code>AtomicInteger</code>原子整型类为例，来看一下CAS实现原理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">().</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">compareAndSet
+</span></span><span class="line"><span class="cl">    --&gt; unsafe.compareAndSwapInt
+</span></span><span class="line"><span class="cl">    ---&gt; unsafe.compareAndSwapInt
+</span></span><span class="line"><span class="cl">    --&gt; (C++) cmpxchg
+</span></span></code></pre></div><p><code>AtomicInteger</code>内部方法都是基于<code>Unsafe</code>类实现的。</p>
+<blockquote>
+<p><code>Unsafe</code>是CAS的核心类，Java无法直接访问底层操作系统，而是通过<code>native</code>方法来访问。不过尽管如此，JVM还是开了一个后门，JDK中有一个类<code>Unsafe</code>，它提供了硬件级别的原子操作。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// setup to use Unsafe.compareAndSwapInt for updates</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Unsafe</span><span class="w"> </span><span class="n">unsafe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Unsafe</span><span class="p">.</span><span class="na">getUnsafe</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">valueOffset</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">objectFieldOffset</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">(</span><span class="n">AtomicInteger</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;value&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="n">ex</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSet</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expect</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">update</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">expect</span><span class="p">,</span><span class="w"> </span><span class="n">update</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>compareAndSwapInt</code>方法参数：</p>
+<ul>
+<li><code>this</code>：<code>Unsafe</code>对象本身，需要通过这个类来获取 <code>value</code> 的内存偏移地址；</li>
+<li><code>valueOffset</code>： <code>valueOffset</code> 表示的是变量值在内存中的偏移地址，因为 <code>Unsafe</code> 就是根据内存偏移地址获取数据的原值的。</li>
+<li><code>expect</code>：当前预期的值；</li>
+<li><code>update</code>：要设置的新值；</li>
+</ul>
+<p>继续向底层深入，就会看到<code>Unsafe</code>类中的一些其他方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Unsafe</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapObject</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapLong</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>对应查看<code>openjdk</code>的<code>hotspot</code>源码，<code>src/share/vm/prims/unsafe.cpp</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">#define FN_PTR(f) CAST_FROM_FN_PTR(void*, &amp;f)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapObject&#34;, CC&#34;(&#34;OBJ&#34;J&#34;OBJ&#34;&#34;OBJ&#34;)Z&#34;,  FN_PTR(Unsafe_CompareAndSwapObject)},
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapInt&#34;,  CC&#34;(&#34;OBJ&#34;J&#34;&#34;I&#34;&#34;I&#34;&#34;)Z&#34;,      FN_PTR(Unsafe_CompareAndSwapInt)},
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapLong&#34;, CC&#34;(&#34;OBJ&#34;J&#34;&#34;J&#34;&#34;J&#34;&#34;)Z&#34;,      FN_PTR(Unsafe_CompareAndSwapLong)},
+</span></span></code></pre></div><p>最终在<code>hotspot</code>源码实现<code>/src/share/vm/runtime/Atomic.cpp</code>中都会调用统一的<code>cmpxchg</code>函数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-cpp" data-lang="cpp"><span class="line"><span class="cl"><span class="n">jbyte</span> <span class="n">Atomic</span><span class="o">::</span><span class="n">cmpxchg</span><span class="p">(</span><span class="n">jbyte</span> <span class="n">exchange_value</span><span class="p">,</span> <span class="k">volatile</span> <span class="n">jbyte</span><span class="o">*</span><span class="n">dest</span><span class="p">,</span> <span class="n">jbyte</span> <span class="n">compare_value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">     <span class="n">assert</span> <span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="n">jbyte</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span><span class="p">,</span><span class="s">&#34;assumption.&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="n">uintptr_t</span> <span class="n">dest_addr</span> <span class="o">=</span> <span class="p">(</span><span class="n">uintptr_t</span><span class="p">)</span> <span class="n">dest</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">uintptr_t</span> <span class="n">offset</span> <span class="o">=</span> <span class="n">dest_addr</span> <span class="o">%</span> <span class="k">sizeof</span><span class="p">(</span><span class="n">jint</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="k">volatile</span> <span class="n">jint</span><span class="o">*</span><span class="n">dest_int</span> <span class="o">=</span> <span class="p">(</span> <span class="k">volatile</span> <span class="n">jint</span><span class="o">*</span><span class="p">)(</span><span class="n">dest_addr</span> <span class="o">-</span> <span class="n">offset</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 对象当前值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jint</span> <span class="n">cur</span> <span class="o">=</span> <span class="o">*</span><span class="n">dest_int</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 当前值cur的地址
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jbyte</span> <span class="o">*</span> <span class="n">cur_as_bytes</span> <span class="o">=</span> <span class="p">(</span><span class="n">jbyte</span> <span class="o">*</span><span class="p">)</span> <span class="p">(</span> <span class="o">&amp;</span> <span class="n">cur</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// new_val地址
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jint</span> <span class="n">new_val</span> <span class="o">=</span> <span class="n">cur</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">jbyte</span> <span class="o">*</span> <span class="n">new_val_as_bytes</span> <span class="o">=</span> <span class="p">(</span><span class="n">jbyte</span> <span class="o">*</span><span class="p">)</span> <span class="p">(</span> <span class="o">&amp;</span> <span class="n">new_val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">      <span class="c1">// new_val存exchange_value，后面修改则直接从new_val中取值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">new_val_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">=</span> <span class="n">exchange_value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 比较当前值与期望值，如果相同则更新，不同则直接返回
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="k">while</span> <span class="p">(</span><span class="n">cur_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">==</span> <span class="n">compare_value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="c1">// 调用汇编指令cmpxchg执行CAS操作，期望值为cur，更新值为new_val
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>         <span class="n">jint</span> <span class="n">res</span> <span class="o">=</span> <span class="n">cmpxchg</span><span class="p">(</span><span class="n">new_val</span><span class="p">,</span> <span class="n">dest_int</span><span class="p">,</span> <span class="n">cur</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">         <span class="k">if</span> <span class="p">(</span><span class="n">res</span> <span class="o">==</span> <span class="n">cur</span><span class="p">)</span> <span class="k">break</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">cur</span> <span class="o">=</span> <span class="n">res</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">new_val</span> <span class="o">=</span> <span class="n">cur</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">new_val_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">=</span> <span class="n">exchange_value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="p">}</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 返回当前值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="k">return</span> <span class="n">cur_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">];</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>从上述源码可以看出CAS操作通过CPU提供的原子指令<code>cmpxchg</code>来实现无锁操作，这个指令会保证在多个处理器同时访问和修改数据时的正确性。</p>
+<p>CPU处理器速度远远大于在主内存中的速度，为了加快访问速度，现代CPU引入了多级缓存，如L1、L2、L3 级别的缓存，这些缓存离CPU越近就越快。
+这些缓存存储了频繁使用的数据，但在多处理器环境中，缓存的一致性成为了下一个问题。
+当CPU中某个处理器对缓存中的共享变量进行了操作后，其他处理器会有个嗅探机制。即将其他处理器共享变量的缓存失效，当其他线程读取时会重新从主内存中读取最新的数据，这是基于<code>MESI</code>缓存一致性协议来实现的。</p>
+<p>在多线程环境中，CAS就是比较当前线程工作内存中的值和主内存中的值，如果相同则执行规定操作，否则继续比较，直到主内存和当前线程工作内存中的值一致为止。
+每个CPU核心都有自己的缓存，用于存储频繁访问的数据。当一个线程在某个CPU核心上修改了共享变量的值时，其他CPU核心上缓存中的该变量会被标记为无效，这样其他线程再访问该变量时就会重新从主内存中获取最新值，从而保证了数据的一致性。
+CAS操作通过CPU提供的原子指令<code>cmpxchg</code>来比较和交换变量的值，它的原子性和线程安全性依赖于CPU的硬件支持和缓存一致性协议的保障。</p>
+<p><img alt="CPU多级缓存" src="/iblog/posts/annex/images/essays/CPU%E5%A4%9A%E7%BA%A7%E7%BC%93%E5%AD%98.jpg"></p>
+<p>所以当执行CAS方法时，读取变量当前的值，并与预期值进行比较。如果变量的当前值等于预期值，则将其更新为新值。如果变量的当前值不等于预期值，则不执行更新操作。
+注意CAS操作是原子的，即整个过程不会被其他线程打断。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="cas问题">CAS问题</h3>
+<ul>
+<li>循环时间长开销：CAS操作在失败时会进行自旋重试，即反复尝试CAS操作直到成功或达到一定的重试次数。自旋次数过多可能会影响性能，因此在使用CAS时需要权衡自旋次数和性能之间的关系。
+例如<code>getAndAddInt</code>方法执行，如果CAS失败会一直会进行尝试，如果CAS长时间不成功，可能会给CPU带来很大的开销。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>原子性问题：CAS操作本身是原子的，即在执行过程中不会被中断。但需要注意的是，CAS操作是针对单个变量的原子操作，而对于判断某个变量的值并根据结果进行另外的操作，需要额外的控制确保整体的原子性。
+这个时候就可以用锁来保证原子性，但是Java从1.5开始JDK提供了<code>AtomicReference</code>类来保证引用对象之间的原子性，可以把多个变量放在一个对象里来进行CAS操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AtomicReferenceSimpleExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DataObject</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">var2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="nf">DataObject</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">var2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 AtomicReference 实例，并初始化为一个 DataObject 对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">DataObject</span><span class="o">&gt;</span><span class="w"> </span><span class="n">atomicRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">DataObject</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Initial&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行 CAS 操作，修改 DataObject 对象的属性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">updateAndGet</span><span class="p">(</span><span class="n">data</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="p">.</span><span class="na">setVar1</span><span class="p">(</span><span class="n">data</span><span class="p">.</span><span class="na">getVar1</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="p">.</span><span class="na">setVar2</span><span class="p">(</span><span class="s">&#34;Updated&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取修改后的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DataObject</span><span class="w"> </span><span class="n">updatedObject</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Updated var1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">updatedObject</span><span class="p">.</span><span class="na">getVar1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Updated var2: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">updatedObject</span><span class="p">.</span><span class="na">getVar2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>ABA问题：ABA问题指的是，在CAS操作过程中，如果一个变量的值从A变成了B，然后再变回A，那么CAS操作会错误地认为变量的值未改变过。
+比如，线程1从内存位置V取出A，线程2同时也从内存取出A，并且线程2进行一些操作将值改为B，然后线程2又将V位置数据改成A，这时候线程1进行CAS操作发现内存中的值依然时A，然后线程1操作成功。尽管线程1的CAS操作成功，但是不代表这个过程没有问题。
+简而言之就是只比较结果，不比较过程。解决ABA问题的常见方法是使用版本号或者标记来跟踪变量的变化。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ABASolutionWithVersion</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始值为100，初始版本号为0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicStampedReference</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">atomicRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicStampedReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">100</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">stampHolder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// 用于获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w"> </span><span class="c1">// 期望值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">200</span><span class="p">;</span><span class="w"> </span><span class="c1">// 新值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟一个线程进行 ABA 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">getStamp</span><span class="p">();</span><span class="w"> </span><span class="c1">// 获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// 修改值和版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 再次修改回原值和新版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 其他线程进行 CAS 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">getStamp</span><span class="p">();</span><span class="w"> </span><span class="c1">// 获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;CAS Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出CAS操作结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
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+        <ul class="nav">
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+                <a class="nav-link text-left" href="#%e6%a0%88%e5%ae%9e%e7%8e%b0%e5%90%8e%e7%bc%80%e8%a1%a8%e8%be%be%e5%bc%8f">
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+        
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+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+                    二叉树的删除
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+                    B树
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#b%e6%a0%91-1">
+                    B&#43;树
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#b%e6%a0%91-2">
+                    B*树
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9b%be">
+                    图
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ae%97%e6%b3%95">
+                    算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ae%97%e6%b3%95%e5%a4%8d%e6%9d%82%e5%ba%a6">
+                    算法复杂度
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%97%b6%e9%97%b4%e5%a4%8d%e6%9d%82%e5%ba%a6">
+                    时间复杂度
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%a9%ba%e9%97%b4%e5%a4%8d%e6%9d%82%e5%ba%a6">
+                    空间复杂度
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%92%e5%bd%92">
+                    递归
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%b7%e5%ae%ab%e5%9b%9e%e6%ba%af">
+                    迷宫回溯
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%ab%e7%9a%87%e5%90%8e%e9%97%ae%e9%a2%98">
+                    八皇后问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e5%ba%8f%e7%ae%97%e6%b3%95">
+                    排序算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%92%e6%b3%a1%e6%8e%92%e5%ba%8f">
+                    冒泡排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%89%e6%8b%a9%e6%8e%92%e5%ba%8f">
+                    选择排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8f%92%e5%85%a5%e6%8e%92%e5%ba%8f">
+                    插入排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%8c%e5%b0%94%e6%8e%92%e5%ba%8f">
+                    希尔排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bf%ab%e9%80%9f%e6%8e%92%e5%ba%8f">
+                    快速排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bd%92%e5%b9%b6%e6%8e%92%e5%ba%8f">
+                    归并排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e6%95%b0%e6%8e%92%e5%ba%8f">
+                    基数排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a0%86%e6%8e%92%e5%ba%8f">
+                    堆排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9f%a5%e6%89%be%e7%ae%97%e6%b3%95">
+                    查找算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e6%80%a7%e6%9f%a5%e6%89%be">
+                    线性查找
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%8c%e5%88%86%e6%9f%a5%e6%89%be">
+                    二分查找
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8f%92%e5%80%bc%e6%9f%a5%e6%89%be">
+                    插值查找
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%90%e6%b3%a2%e9%82%a3%e5%a5%91%e6%9f%a5%e6%89%be">
+                    斐波那契查找
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%93%88%e5%a4%ab%e6%9b%bc%e7%bc%96%e7%a0%81">
+                    哈夫曼编码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e6%b2%bb%e7%ae%97%e6%b3%95">
+                    分治算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8a%a8%e6%80%81%e8%a7%84%e5%88%92%e7%ae%97%e6%b3%95">
+                    动态规划算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#kmp%e7%ae%97%e6%b3%95">
+                    KMP算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b4%aa%e5%bf%83%e7%ae%97%e6%b3%95">
+                    贪心算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%99%ae%e9%87%8c%e5%a7%86%e7%ae%97%e6%b3%95">
+                    普里姆算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%8b%e9%b2%81%e6%96%af%e5%8d%a1%e5%b0%94%e7%ae%97%e6%b3%95">
+                    克鲁斯卡尔算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%aa%e6%9d%b0%e6%96%af%e7%89%b9%e6%8b%89%e7%ae%97%e6%b3%95">
+                    迪杰斯特拉算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%97%e6%b4%9b%e4%bc%8a%e5%be%b7%e7%ae%97%e6%b3%95">
+                    弗洛伊德算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%a9%ac%e8%b8%8f%e6%a3%8b%e7%9b%98%e7%ae%97%e6%b3%95">
+                    马踏棋盘算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
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+                        <h2 id="post_single_title">数据结构与算法详解</h2>
+                        <span id="post_page_title_date" class="date">2021.12.10</span>
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+                    <div class="post_content markdown"><h2 id="数据结构">数据结构</h2>
+<p>数据结构是一门研究组织数据方式的学科，有了编程语言也就有了数据结构，学好数据结构可以编写出更有效率的代码。数据结构是算法的基础，想要学好算法，就必须把数据结构学到位。</p>
+<p>数据结构包括：线性结构、非线性结构。</p>
+<p>线性结构作为最常用的数据结构，其特点是数据元素之间存在一对一的线性存储关系。线性结构有两种不同的存储结构，即顺序存储和链式存储。顺序存储的线性表被称为顺序表，顺序表中存储元素的地址是连续的；链式存储的线性表被称为链表，链表中存储元素的地址不一定是连续的，元素结点中存放数据元素以及相邻元素地址信息。</p>
+<p>常见的线性结构有：数组、链表、队列、栈；常见非线性结构有：多维数组、广义表、树结构、图结构。</p>
+<h3 id="稀疏数组">稀疏数组</h3>
+<p>使用稀疏数组可以用来压缩数据。稀疏数组的第一行依次记录原数组一共有几行几列，有多少个不为零的值，之后的每行记录原数组中不为零的值所在的行数、列数以及数组中元素该值。如图所示：</p>
+<p><img alt="数据结构与算法-001" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-001.png"></p>
+<p>二维数组转稀疏数组</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">TwoDimensionArrayDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 将二维数组转换为稀疏数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="nf">twoDimensionArrayToSparseArray</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">array</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 记录棋盘中有效值的数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">sum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">column</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ints</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">array</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">column</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ints</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">item</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">ints</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">item</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">sum</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 创建稀疏数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">sparseArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">3</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">row</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">column</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sum</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 给稀疏数组赋值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">array</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">array</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">array</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">count</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">count</span><span class="o">][</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">j</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">count</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;稀疏数组====》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">sparseArray</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%d\t%d\t%d\t\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">1</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">sparseArray</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>稀疏数组转二维数组</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">TwoDimensionArrayDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 稀疏数组转二维数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="nf">sparseArrayToTwoDimensionArray</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">sparseArray</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">toTwoDimensionArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">0</span><span class="o">]][</span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">1</span><span class="o">]]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 给二维数组赋值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">sparseArray</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">toTwoDimensionArray</span><span class="o">[</span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">0</span><span class="o">]][</span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">1</span><span class="o">]]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;二维数组====》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">toTwoDimensionArray</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">row</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%d\t&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">data</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">toTwoDimensionArray</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="队列">队列</h3>
+<p>队列是一个有序列表，可以使用数组或链表来实现。队列遵循先入先出的原则。即，先存入队列的数据，要先取出。后存入的要后取出。</p>
+<p>使用数组模拟队列示意图：</p>
+<p><img alt="数据结构与算法-002" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-002.png"></p>
+<p>数组模拟单向队列</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayQueue</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 队列容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存队列中的数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 头部指针</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">front</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 尾部指针</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="nf">ArrayQueue</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">capacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">capacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">capacity</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">front</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">rear</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isFull</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">capacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isFull</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列已经满了，不能在继续添加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[++</span><span class="n">rear</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">get</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列为空，不能获取元素&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">arr</span><span class="o">[++</span><span class="n">front</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示队列的所有数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">show</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列空的，没有数据~~&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始遍历队列：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;arr[%d]=%d\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示队列的头数据， 注意不是取出数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">peek</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;队列空的，没有数据~~&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">front</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>数组模拟环形队列</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kd">class</span> <span class="nc">CircleArrayQueue</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 队列容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存队列中的数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 头部指针</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">front</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 尾部指针</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="nf">CircleArrayQueue</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">capacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">capacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">capacity</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isFull</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 此处+1 是因为存储元素从0算起</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">rear</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="w">  </span><span class="o">==</span><span class="w"> </span><span class="n">front</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isFull</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列已经满了，不能在继续添加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">rear</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">rear</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">rear</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">get</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列为空，不能获取元素&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">front</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">front</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">front</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示队列的所有数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">show</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列空的，没有数据~~&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始遍历队列：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">((</span><span class="n">rear</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">capacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">front</span><span class="p">)</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">);</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;arr[%d]=%d\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示队列的头数据， 注意不是取出数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">peek</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;队列空的，没有数据~~&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">front</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="链表">链表</h3>
+<p>链表属于线性结构，存储空间不连续。</p>
+<p>链表特点：</p>
+<ul>
+<li>链表是以节点的方式来存储，是链式存储；data 域存放数据，next 域指向下一个节点；</li>
+<li>链表分带头节点的链表和没有头节点的链表，根据实际的需求来确定；</li>
+</ul>
+<p><img alt="数据结构与算法-003" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-003.png"></p>
+<h4 id="单向链表">单向链表</h4>
+<p>操作单向链表：对于插入、删除操作，只能定位至待操作节点的前一个节点，如果定位至当前节点，那么其上一个节点的信息便会丢失。</p>
+<p>单向链表，链表的增、删、查、改</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">SingleLinkedList</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 头结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">headNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 指向下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 退出循环意味着tmpNode.next == null 即找到最后一个结点了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 顺序添加</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addByOrder</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将新插入的结点num跟链表中已经存在的num进行比较，如果 &lt; 链表中的结点 则说明找到了该位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果num相同则不能添加</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">flag</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;需要添加的结点编号：%d已经存在了&#34;</span><span class="p">,</span><span class="n">node</span><span class="p">.</span><span class="na">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历除了头结点外的所有结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;链表为空！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">tmpNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 指向下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;num=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>反转单向链表</p>
+<p><img alt="数据结构与算法-004" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-004.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">LinkedListDemo</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 反转链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">reserve</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">head</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Node</span><span class="w"> </span><span class="n">reserve</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Node</span><span class="w"> </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 遍历链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 遍历原来的链表，每遍历一个节点，就将其取出，并放在新的链表reverseHead 的最前端</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">cur</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存当前结点的下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cur</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将cur的下一个节点指向新的链表的最前端（覆盖掉）保证将最新的结点放到reseve的最前面</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cur</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reserve</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将cur 连接到新的链表上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">reserve</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cur</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将之前保存好的结点赋值给当前结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>利用栈逆序打印单向链表</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">LinkedListDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">reservePrint</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">head</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">nodes</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">tmp</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 从stack中取出结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">nodes</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">nodes</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="双向链表">双向链表</h4>
+<p>对比单向链表：</p>
+<ul>
+<li>单向链表，查找的方向只能是一个方向，而双向链表可以向前或者向后查找；</li>
+<li>单向链表不能自我删除，需要靠辅助节点，而双向链表，则可以自我删除；</li>
+</ul>
+<p><img alt="数据结构与算法-005" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-005.png"></p>
+<p>双向链表，增、删、改、查</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">DoubleLinkedList</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 头结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">headNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">getHeadNode</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">headNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 指向下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 退出循环意味着tmpNode.next == null 即找到最后一个结点了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">node</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 双向链表修改</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">headNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmp</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 双向链表删除</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;链表为空，无法删除！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">num</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmp</span><span class="p">.</span><span class="na">prev</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 最后一个结点的next 为null null.pre会出现空指针异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">prev</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历除了头结点外的所有结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;链表为空！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">tmpNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 指向下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">prev</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;num=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="约瑟夫问题">约瑟夫问题</h4>
+<blockquote>
+<p>约瑟夫问题为：设编号为 1，2，…n的n个人围坐一圈，约定编号为 k（1&lt;=k&lt;=n） 的人从 1 开始报数,数到 m 的那个人出列，它的下一位又从 1 开始报数，数到 m 的那个人又出列， 依次类推，直到所有人出列为止，由此产生一个出队编号的序列。</p>
+</blockquote>
+<p>用一个不带头结点的循环链表来处理约瑟夫问题：先构成一个有 n 个结点的单循环链表，然后由 k 结点起从 1 开始计数，计到 m 时，对应结点从链表中删除，然后再从被删除结点的下一个结点又从 1 开始计数，直到最后一个结点从链表中删除算法结束。</p>
+<p><img alt="数据结构与算法-006" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-006.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">JoesphSingletonLinkedList</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 向单向链表添加数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">nums</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nums</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;nums的值不正确&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">nums</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">first</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">cur</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">node</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历单向循环链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;当前结点为：%d\n&#34;</span><span class="p">,</span><span class="n">tmp</span><span class="p">.</span><span class="na">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">first</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 约瑟夫问题</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">joseph</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">startNum</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">countNum</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">sum</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">startNum</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">sum</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">startNum</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">countNum</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;输入的参数不正确！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建辅助指针，将该指针指向 first 的前一个</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">helper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">first</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">helper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将first 和 help指针循环 （startNum - 1）次；因为从startNum开始，需要减一</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">startNum</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">helper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当环形链表中只存在一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">first</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">helper</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 因为是环形链表，所以需要循环挨个出链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">countNum</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">helper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当前 first 就是出圈的结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;当前出队列的结点编号为：%d\n&#34;</span><span class="p">,</span><span class="n">first</span><span class="p">.</span><span class="na">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;最后的结点为：%d\n&#34;</span><span class="p">,</span><span class="n">first</span><span class="p">.</span><span class="na">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;num=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="栈">栈</h3>
+<p>栈的英文为stack，是一个先入后出(FILO-First In Last Out)的有序列表，最先放入栈中元素在栈底，最后放入的元素在栈顶，而删除元素刚好相反，最后放入的元素最先删除，最先放入的元素最后删除。</p>
+<p>栈是限制线性表中元素的插入和删除只能在线性表的同一端进行的一种特殊线性表。允许插入和删除的一端，为变化的一端，称为栈顶(Top)，另一端为固定的一端，称为栈底(Bottom)。</p>
+<p>下图是出栈和入栈</p>
+<p><img alt="数据结构与算法-007" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-007.png"></p>
+<p>栈的应用场景：</p>
+<ul>
+<li>子程序的调用： 在跳往子程序前， 会先将下个指令的地址存到堆栈中， 直到子程序执行完后再将地址取出， 以回到原来的程序中；</li>
+<li>处理递归调用： 和子程序的调用类似， 只是除了储存下一个指令的地址外， 也将参数、 区域变量等数据存入栈中；</li>
+<li>表达式的转换：中缀表达式转后缀表达式与求值；</li>
+<li>二叉树的遍历；</li>
+<li>图形的深度优先(depth 一 first)搜索法；</li>
+</ul>
+<p>数组模拟栈</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">ArrayStack</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">top</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">stack</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ArrayStack</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[</span><span class="n">size</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">top</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isFull</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">top</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">top</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 入栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">push</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isFull</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;栈已经满了，不能继续添加！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">top</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">stack</span><span class="o">[</span><span class="n">top</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 出栈操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">pop</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;栈已经为空，不能继续pop&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">T</span><span class="w"> </span><span class="n">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="p">)</span><span class="k">this</span><span class="p">.</span><span class="na">stack</span><span class="o">[</span><span class="n">top</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">top</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">val</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;栈为空不能继续遍历！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;遍历栈==》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">top</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&gt;=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">--</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">stack</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="栈实现中缀表达式">栈实现中缀表达式</h4>
+<p><img alt="数据结构与算法-008" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-008.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">CalcInfixExpressions</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calcInfixExpressions</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">expression</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 定义变量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">chars</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">expression</span><span class="p">.</span><span class="na">toCharArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">chars</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">numStack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">Character</span><span class="o">&gt;</span><span class="w"> </span><span class="n">oprStack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">chars</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断字符是否为数字,如果是数字就放入数栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Character</span><span class="p">.</span><span class="na">isDigit</span><span class="p">(</span><span class="n">ch</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 接收多位数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ch</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 从当前字符开始遍历，如果下一位字符不是数字，则将该数字压入栈中并退出循环，如果是数字，则需要拼接起来</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Character</span><span class="p">.</span><span class="na">isDigit</span><span class="p">(</span><span class="n">expression</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">String</span><span class="w"> </span><span class="n">strNum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">expression</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">parseInt</span><span class="p">(</span><span class="n">strNum</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">j</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">num</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">48</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">numStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 非数字，即运算符,如果为空直接加入栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oprStack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">oprStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">ch</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果运算符栈不为空，需要比较运算符的优先级，如果当前运算符的优先级 &lt;= 栈顶的运算符的优先级，需要计算在压入栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oprPriority</span><span class="p">(</span><span class="n">oprStack</span><span class="p">.</span><span class="na">peek</span><span class="p">())</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">oprPriority</span><span class="p">(</span><span class="n">ch</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">numStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">calc</span><span class="p">(</span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="w"> </span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="w"> </span><span class="n">oprStack</span><span class="p">.</span><span class="na">pop</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将字符压入操作符栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oprStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">ch</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将处理好的数据按照顺序弹出，进行计算，得到数栈中最后一个数就是最终的结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">oprStack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">numStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">calc</span><span class="p">(</span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="w"> </span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="w"> </span><span class="n">oprStack</span><span class="p">.</span><span class="na">pop</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取字符的优先级</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">oprPriority</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ch</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">&#39;*&#39;</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">&#39;/&#39;</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ch</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calc</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num1</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">num2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">num1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;*&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">num2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;/&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">num1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="栈实现后缀表达式">栈实现后缀表达式</h4>
+<p>后缀表达式又称逆波兰表达式，与前缀表达式相似，只是运算符位于操作数之后。例如： (3+4)×5-6 对应的后缀表达式就是 3 4 + 5 × 6 –</p>
+<p>思路：从左至右扫描表达式，遇到数字时，将数字压入堆栈，遇到运算符时，弹出栈顶的两个数，用运算符对它们做相应的计算（次顶元素 和 栈顶元素），并将结果入栈；重复上述过程直到表达式最右端，最后运算得出的值即为表达式的结果。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">PolandNotation</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算后缀表达式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calcSuffixExceptions</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">suffixExpres</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">chars</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">suffixExpres</span><span class="p">.</span><span class="na">toCharArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">chars</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">suffixExpres</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">Character</span><span class="p">.</span><span class="na">isDigit</span><span class="p">(</span><span class="n">ch</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">calc</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="n">ch</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">res</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">ch</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">48</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calc</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num1</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">num2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">num1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;*&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">num2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;/&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">num1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">default</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;运算符有误&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="中缀表达式转后缀表达式">中缀表达式转后缀表达式</h4>
+<p><img alt="数据结构与算法-009" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-009.png"></p>
+<p>中缀表达式转后缀表达式代码实现</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">InfixToPolandNotation</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 根据ASCII 判断是否为数字</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isNumber</span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">&gt;=</span><span class="n">48</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">57</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取字符的优先级</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">oprPriority</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">opr</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;*&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">opr</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">opr</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;+&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">opr</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;-&#34;</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将中缀表达式字符串转成中缀表达式集合</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">toInfixExceptionList</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">number</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="w"> </span><span class="n">c</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">length</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isNumber</span><span class="p">((</span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">index</span><span class="p">)))){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">c</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">isNumber</span><span class="p">((</span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">index</span><span class="p">)))){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">number</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">number</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">list</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将中缀表达式转为后缀表达式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">infixExpressionToSuffixExpress</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">finalList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">item</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果是数字或者为（ 将该值压入栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">item</span><span class="p">.</span><span class="na">matches</span><span class="p">(</span><span class="s">&#34;\\d+&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">finalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">item</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;(&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果是 ）则将 ()中间的数重新压入list中，最后将 ） 移除掉</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">item</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;)&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">().</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;(&#34;</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">finalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 如果不是 ）则判断运算符的优先级，如果符号栈栈顶的优先级 &gt;= 当前的优先级，则将该运算符加入数字栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">oprPriority</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">oprPriority</span><span class="p">(</span><span class="n">item</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">finalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将operStack中剩余的运算符依次弹出并加入tempList</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">finalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">finalList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>完整逆波兰表达式代码，支持小数、支持消除空格</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReversePolishMultiCalc</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">	 </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 匹配 + - * / ( ) 运算符
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">SYMBOL</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;\\+|-|\\*|/|\\(|\\)&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">LEFT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;(&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">RIGHT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;)&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">ADD</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;+&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">MINUS</span><span class="o">=</span><span class="w"> </span><span class="s">&#34;-&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">TIMES</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;*&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">DIVISION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 加減 + -
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">LEVEL_01</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 乘除 * /
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">LEVEL_02</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 括号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">synchronizedList</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 去除所有空白符
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">replaceAllBlank</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// \\s+ 匹配任何空白字符，包括空格、制表符、换页符等等, 等价于[ \f\n\r\t\v]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">replaceAll</span><span class="p">(</span><span class="s">&#34;\\s+&#34;</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 判断是不是数字 int double long float
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isNumber</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Pattern</span><span class="w"> </span><span class="n">pattern</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern</span><span class="p">.</span><span class="na">compile</span><span class="p">(</span><span class="s">&#34;^[-\\+]?[.\\d]*$&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">pattern</span><span class="p">.</span><span class="na">matcher</span><span class="p">(</span><span class="n">s</span><span class="p">).</span><span class="na">matches</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 判断是不是运算符
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isSymbol</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">matches</span><span class="p">(</span><span class="n">SYMBOL</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 匹配运算等级
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calcLevel</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="s">&#34;+&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;-&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">LEVEL_01</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="s">&#34;*&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;/&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">LEVEL_02</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 匹配
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">doMatch</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">trim</span><span class="p">()))</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;data is empty&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="o">!</span><span class="n">isNumber</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">0</span><span class="p">)</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">))</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;data illeagle,start not with a number&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">replaceAllBlank</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">each</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">isSymbol</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">each</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">//栈为空，(操作符，或者 操作符优先级大于栈顶优先级 &amp;&amp; 操作符优先级不是( )的优先级 及是 ) 不能直接入栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">LEFT</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="o">||</span><span class="w"> </span><span class="p">((</span><span class="n">calcLevel</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">()))</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">each</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="w"> </span><span class="o">!</span><span class="n">stack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">//栈非空，操作符优先级小于等于栈顶优先级时出栈入列，直到栈为空，或者遇到了(，最后操作符入栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">stack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())</span><span class="w"> </span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="p">(</span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">data</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">each</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="n">RIGHT</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">each</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// ) 操作符，依次出栈入列直到空栈或者遇到了第一个)操作符，此时)出栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">stack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="p">(</span><span class="n">LEVEL_HIGH</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">data</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">;</span><span class="w">    </span><span class="c1">//前一个运算符的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="o">-</span><span class="n">1</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">isSymbol</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">)</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">)</span><span class="w"> </span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">each</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">start</span><span class="p">,</span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">start</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="p">(</span><span class="n">isNumber</span><span class="p">(</span><span class="n">each</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">data</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">each</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;data not match number&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//如果栈里还有元素，此时元素需要依次出栈入列，可以想象栈里剩下栈顶为/，栈底为+，应该依次出栈入列，可以直接翻转整个stack 添加到队列</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Collections</span><span class="p">.</span><span class="na">reverse</span><span class="p">(</span><span class="n">stack</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">data</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">stack</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">data</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 算出结果
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Double</span><span class="w"> </span><span class="nf">doCalc</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Double</span><span class="w"> </span><span class="n">d</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0d</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="n">list</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">d</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">d</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">isSymbol</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">))){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Double</span><span class="w"> </span><span class="n">d1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">doTheMath</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">),</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">),</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list1</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list1</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">i</span><span class="o">-</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list1</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">i</span><span class="o">-</span><span class="n">2</span><span class="p">,</span><span class="n">d1</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list1</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">subList</span><span class="p">(</span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">doCalc</span><span class="p">(</span><span class="n">list1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">d</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 运算
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s1
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s2
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param symbol
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Double</span><span class="w"> </span><span class="nf">doTheMath</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s1</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">s2</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">symbol</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Double</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">symbol</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">ADD</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">MINUS</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s1</span><span class="p">)</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">TIMES</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s1</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">DIVISION</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s1</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">default</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//String math = &#34;9+(3-1)*3+10/2&#34;;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">math</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;12.8 + (2 - 3.55)*4+10/5.0&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">doCalc</span><span class="p">(</span><span class="n">doMatch</span><span class="p">(</span><span class="n">math</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="哈希表">哈希表</h3>
+<p>哈希表也叫散列表，是根据关键码值(Key value)而直接进行访问的数据结构。</p>
+<p>它通过把关键码值映射到表中一个位置来访问记录，以加快查找的速度。这个映射函数叫做散列函数，存放记录的数组叫做散列表。</p>
+<p>手写模拟哈希表</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HashTableDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashTab</span><span class="w"> </span><span class="n">hashTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashTab</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;zs&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;lx&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;ex&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;as&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;we&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;添加元素后===》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">hashTab</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;删除后===》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">hashTab</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HashTab</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">NodeList</span><span class="o">[]</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">HashTab</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NodeList</span><span class="o">[</span><span class="n">size</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">nodes</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NodeList</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">put</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 放入hash表的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">nodes</span><span class="o">[</span><span class="n">getPosition</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">id</span><span class="p">)</span><span class="o">]</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">nodes</span><span class="o">[</span><span class="n">getPosition</span><span class="p">(</span><span class="n">id</span><span class="p">)</span><span class="o">]</span><span class="p">.</span><span class="na">delete</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getPosition</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;HashTab{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;nodes=\n&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;}&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">NodeList</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 头结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 头结点不要动，将添加的结点放到链表的最后一个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 当下一个结点等于null时，找到最后一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 展示当前链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前链表为空&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 辅助结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">tmp</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 根据ID删除链表中的某个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">delete</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前链表为空&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断删除的是否是头结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">preNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">curNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">preNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">curNode</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">curNode</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">preNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">curNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;删除成功，删除的是: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">curNode</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;,&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">curNode</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">curNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">preNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">preNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">curNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">curNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;删除失败，节点不存在&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;NodeList{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;head=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;}\n&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;id=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, next=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;}&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="二叉树">二叉树</h3>
+<blockquote>
+<p>二叉树（Binary tree）是树形结构的一个重要类型。许多实际问题抽象出来的数据结构往往是二叉树形式，即使是一般的树也能简单地转换为二叉树，而且二叉树的存储结构及其算法都较为简单，因此二叉树显得特别重要。二叉树特点是每个结点最多只能有两棵子树，且有左右之分。</p>
+</blockquote>
+<p>二叉树是n个有限元素的集合，该集合或者为空、或者由一个称为根的元素及两个不相交的、被分别称为左子树和右子树的二叉树组成，是有序树。当集合为空时，称该二叉树为空二叉树。在二叉树中，一个元素也称作一个结点。</p>
+<p>如果该二叉树的所有叶子节点都在最后一层，并且结点总数为 2^n -1， n 为层数，则称为满二叉树。</p>
+<p>如果该二叉树的所有叶子节点都在最后一层或者倒数第二层，而且最后一层的叶子节点在左边连续，倒数第二层的叶子节点在右边连续，我们称为完全二叉树。</p>
+<blockquote>
+<p>PS: 二叉树中结点等价于节点</p>
+</blockquote>
+<p><img alt="数据结构与算法-022" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-022.png"></p>
+<h4 id="二叉树的遍历及查找">二叉树的遍历及查找</h4>
+<p>对于二叉树来讲最主要、最基本的运算是遍历。遍历二叉树 是指以一定的次序访问二叉树中的每个结点。所谓访问结点是指对结点进行各种操作的简称。</p>
+<p>例如，查询结点数据域的内容，或输出它的值，或找出结点位置，或是执行对结点的其他操作。遍历二叉树的过程实质是把二叉树的结点进行线性排列的过程。</p>
+<p>二叉树的遍历方法：</p>
+<ul>
+<li>前序遍历：先访问根结点，然后前序遍历左子树，在前序遍历右子树；</li>
+<li>中序遍历：中序遍历根结点的左子树，然后访问根结点，最后遍历右子树；</li>
+<li>后序遍历：后序遍历左子树，然后后序遍历右子树，最后访问根结点；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BinaryTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="s">&#34;zs&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="s">&#34;ls&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="s">&#34;ww&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="s">&#34;zq&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">5</span><span class="p">,</span><span class="s">&#34;111&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">root</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">binaryTreeObj2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">root</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">binaryTreeObj3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTreeObj3</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">binaryTreeObj4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTreeObj3</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">binaryTreeObj5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTree</span><span class="w"> </span><span class="n">binaryTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTree</span><span class="p">.</span><span class="na">setRoot</span><span class="p">(</span><span class="n">root</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTree</span><span class="p">.</span><span class="na">preOrderShow</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">binaryTree</span><span class="p">.</span><span class="na">preOrderSearch</span><span class="p">(</span><span class="n">11</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;没有找到该结点～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;找到当前结点：id: %d, name: %s&#34;</span><span class="p">,</span><span class="n">binaryTreeObj</span><span class="p">.</span><span class="na">getId</span><span class="p">(),</span><span class="n">binaryTreeObj</span><span class="p">.</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BinaryTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRoot</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preOrderShow</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postOrderShow</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">postOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">midOrderShow</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">midOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">preOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">preOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">infixOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">infixOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">postOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">postOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BinaryTreeObj</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">BinaryTreeObj</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setLeft</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">left</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRight</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 前序遍历：根结点 =》 左结点 =》 右结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preOrder</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 后序遍历： 左结点 =》 右结点 =》 根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postOrder</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">postOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">postOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历： 左结点 =》 根结点 =》 右结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">midOrder</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">midOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">midOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 前序查找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">preOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">preOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">preOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序查找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">infixOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">infixOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">infixOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 后序查找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">postOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">postOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">postOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;BinaryTreeObj{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;id=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="二叉树的删除">二叉树的删除</h4>
+<p><img alt="数据结构与算法-023" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-023.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BinaryTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">del</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">getId</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">delNo</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BinaryTreeObj</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 根据ID删除结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">delNo</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 找到当前结点的左子树结点是否为指定结点，如果是则将其置空</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 与上面同理删除右子树结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前左结点或右结点 不是要删除的结点 则进行递归删除</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">delNo</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">delNo</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="顺序存储二叉树">顺序存储二叉树</h4>
+<p>二叉树的顺序存储，指的是使用顺序表（数组）存储二叉树。</p>
+<p>需要注意的是，顺序存储只适用于完全二叉树。换句话说，只有完全二叉树才可以使用顺序表存储。因此，如果我们想顺序存储普通二叉树，需要提前将普通二叉树转化为完全二叉树。</p>
+<blockquote>
+<p>顺序存储二叉树应用实例：八大排序算法中的堆排序，就会使用到顺序存储二叉树。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrBinaryTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrBinaryTree</span><span class="w"> </span><span class="n">arrBinaryTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrBinaryTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arrBinaryTree</span><span class="p">.</span><span class="na">setArrayTree</span><span class="p">(</span><span class="n">arr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arrBinaryTree</span><span class="p">.</span><span class="na">preArrBinaryTree</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ArrBinaryTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setArrayTree</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preArrBinaryTree</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">nextLeftIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">nextRightIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nextLeftIndex</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">preArrBinaryTree</span><span class="p">(</span><span class="n">nextLeftIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nextRightIndex</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">preArrBinaryTree</span><span class="p">(</span><span class="n">nextRightIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="线索化二叉树">线索化二叉树</h4>
+<p>n 个结点的二叉链表中含有 n+1【公式 2n-(n-1)=n+1】个空指针域。利用二叉链表中的空指针域，存放指向该结点在 <strong>某种遍历次序</strong> 下的<strong>前驱</strong>和<strong>后继</strong>结点的指针，这种附加的指针称为&quot;线索&quot;。这种加上了线索的二叉链表称为线索链表，相应的二叉树称为线索二叉树。</p>
+<p>根据线索性质的不同，线索二叉树可分为前序线索二叉树、中序线索二叉树和后序线索二叉树三种。</p>
+<p>如图，按照前序遍历可以得到数组 {1, 2, 4, 5, 3, 6} 其中</p>
+<ul>
+<li>【2】的前驱结点为【1】，后继结点为【4】</li>
+<li>【6】的前驱结点为【3】，后继结点为 null</li>
+</ul>
+<p><img alt="数据结构与算法-024" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-024.png"></p>
+<p>中序线索化二叉树示意图</p>
+<p><img alt="数据结构与算法-025" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-025.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ThreadedBinaryTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="s">&#34;zs&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="s">&#34;ls&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="s">&#34;ww&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="s">&#34;zq&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">5</span><span class="p">,</span><span class="s">&#34;111&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">root</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">binaryTreeObj2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">root</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">binaryTreeObj3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTreeObj3</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">binaryTreeObj4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTreeObj3</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">binaryTreeObj5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 中序线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ThreadedBinaryTree</span><span class="w"> </span><span class="n">threadedBinaryTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadedBinaryTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threadedBinaryTree</span><span class="p">.</span><span class="na">infixThreadedBinaryTree</span><span class="p">(</span><span class="n">root</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历中序线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threadedBinaryTree</span><span class="p">.</span><span class="na">forEachInfixThreadedBinaryTree</span><span class="p">(</span><span class="n">root</span><span class="p">);</span><span class="w"> </span><span class="c1">// 2,1,4,3,5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ThreadedBinaryTree</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">pre</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixThreadedBinaryTree</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 左递归线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">infixThreadedBinaryTree</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getLeft</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线索化核心代码 将左结点线索化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getLeft</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">pre</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">setLeftType</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将右结点线索化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pre</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">pre</span><span class="p">.</span><span class="na">getRight</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">pre</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">pre</span><span class="p">.</span><span class="na">setRightType</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使辅助结点指针指向当前结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pre</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 右递归线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">infixThreadedBinaryTree</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getRight</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历中序线索二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">forEachInfixThreadedBinaryTree</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 用辅助结点保存根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 向左子树遍历,直到找到 leftType=1 的结点，等于1代表该结点为前驱结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getLeftType</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">getLeft</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 向右子树遍历，直到找到 rightType=0 的结点， 等于0代表该结点为右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getRightType</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">getRight</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// node 结点向右边找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">getRight</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BinaryTreeObj</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果leftType == 0 表示指向的是左子树, 如果 1 则表示指向前驱结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果rightType == 0 表示指向是右子树, 如果 1 表示指向后继结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">leftType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rightType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">BinaryTreeObj</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">getLeft</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">getRight</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setLeft</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">left</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRight</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setLeftType</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">leftType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">leftType</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leftType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRightType</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">rightType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">rightType</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rightType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getLeftType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">leftType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getRightType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">rightType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="哈夫曼树">哈夫曼树</h3>
+<p>哈夫曼树重要概念：</p>
+<ul>
+<li>路径和路径长度：在一棵树中，从一个结点往下可以达到的孩子或孙子结点之间的通路，称为路径。通路中分支的数目称为路径长度。若规定根结点的层数为 1，则从根结点到第 L 层结点的路径长度为 L-1；</li>
+<li>结点的权及带权路径长度：若将树中结点赋给一个有着某种含义的数值，则这个数值称为该结点的权。结点的带权路径长度为：从根结点到该结点之间的路径长度与该结点的权的乘积；</li>
+<li>树的带权路径长度：树的带权路径长度规定为所有叶子结点的带权路径长度之和，记为WPL(weighted path length) ，权值越大的结点离根结点越近的二叉树才是最优二叉树。WPL 最小的就是赫夫曼树；</li>
+</ul>
+<p>给定n个权值作为n个叶子结点，构造一棵二叉树，若该树的带权路径长度(wpl)达到最小，称这样的二叉树为最优二叉树，称为哈夫曼树，有些资料也译为赫夫曼树。</p>
+<p><img alt="数据结构与算法-028" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-028.png"></p>
+<p>WPL最小的就是哈夫曼树，如上图，中间的树就是哈夫曼树。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HuffmanTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HuffmanTree</span><span class="w"> </span><span class="n">huffmanTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanTree</span><span class="p">.</span><span class="na">buildHuffmanTree</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">13</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">29</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;前序遍历huffman树：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">huffmanTree</span><span class="p">.</span><span class="na">preOrder</span><span class="p">(</span><span class="n">root</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HuffmanTree</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preOrder</span><span class="p">(</span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">root</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">root</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="nf">buildHuffmanTree</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">HuffmanTreeNode</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanTreeNode</span><span class="p">(</span><span class="n">value</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果集合中的元素大于1则继续循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从大到小进行排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Collections</span><span class="p">.</span><span class="na">sort</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取集合中两个较小的元素进行构建 huffman 树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">leftNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">rightNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">parentNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanTreeNode</span><span class="p">(</span><span class="n">leftNode</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">rightNode</span><span class="p">.</span><span class="na">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leftNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rightNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 构建后将 leftNode， rightNode 移除集合；将parentNode加入集合；然后重新排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">leftNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">rightNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">parentNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HuffmanTreeNode</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Comparable</span><span class="o">&lt;</span><span class="n">HuffmanTreeNode</span><span class="o">&gt;</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">HuffmanTreeNode</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preOrder</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">compareTo</span><span class="p">(</span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">o</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 从小到大排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">o</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;HuffmanTreeNode{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;value=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="二叉排序树">二叉排序树</h3>
+<p>二叉排序树（Binary Sort Tree），又称二叉查找树（Binary Search Tree），亦称二叉搜索树。是数据结构中的一类。在一般情况下，查询效率比链表结构要高。</p>
+<p>对于二叉排序树的任何一个非叶子节点，要求左子节点的值比当前节点的值小，右子节点的值比当前节点的值大。如果有相同的值，可以将该节点放在左子节点或右子节点，二叉排序树的中序遍历为有序数列。</p>
+<p><img alt="数据结构与算法-030" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-030.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BinarySortTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRoot</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查找结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">search</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查找当前结点的父结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">searchParentNode</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">searchParentNode</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 删除结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">delNode</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果删除的结点是根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">targetNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取当前结点的父结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">parentNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">searchParentNode</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除的结点是叶子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断是左结点还是右结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除的结点有两个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从右子树找到最小的值并删除，将该值赋值给targetNode</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">targetNode</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">delRightTreeMin</span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除只有一颗子树的结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">parentNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当前结点存在左子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">parentNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当前结点存在右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">delRightTreeMin</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">target</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 循环的查找左子节点，就会找到最小值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">target</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">target</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 此时 target就指向了最小结点 删除最小结点（该节点肯定是左叶子节点）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">delNode</span><span class="p">(</span><span class="n">target</span><span class="p">.</span><span class="na">val</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">target</span><span class="p">.</span><span class="na">val</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">val</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">val</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">val</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查找结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">search</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">search</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查找当前结点的父结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">searchParentNode</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">searchParentNode</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">searchParentNode</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前待插入结点的值小于当前结点，将其插入在左子树中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将当前结点插入右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;val=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">val</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="平衡二叉树">平衡二叉树</h3>
+<p>二叉搜索树一定程度上可以提高搜索效率，但是当序列构造二叉搜索树，可能会将二叉树退化成单链表，从而降低搜索效率。</p>
+<p>平衡二叉树也叫平衡二叉搜索树（Self-balancing binary search tree）又被称为AVL树，可以保证查询效率较高。</p>
+<p>平衡二叉树的特点：</p>
+<ul>
+<li>平衡二叉树一定是二叉排序；</li>
+<li>是一棵空树或它的左右两个子树的高度差的绝对值不超过1，并且左右两个子树都是一棵平衡二叉树；</li>
+</ul>
+<p><img alt="数据结构与算法-031" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-031.gif"></p>
+<p>将有序二叉树变为平衡二叉树代码</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AVLTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AVLTree</span><span class="w"> </span><span class="n">avlTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AVLTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">11</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">avlTree</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前树高度：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">avlTree</span><span class="p">.</span><span class="na">height</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前根结点：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">avlTree</span><span class="p">.</span><span class="na">getRoot</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前左子树高度：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">avlTree</span><span class="p">.</span><span class="na">getRoot</span><span class="p">().</span><span class="na">leftHeight</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前右子树高度：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">avlTree</span><span class="p">.</span><span class="na">getRoot</span><span class="p">().</span><span class="na">rightHeight</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">AVLTree</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRoot</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">getRoot</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">height</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">height</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前左子树的高度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">leftHeight</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">height</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前结点右子树的高度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">rightHeight</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">height</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前结点的高度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">height</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">height</span><span class="p">()),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">height</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">leftRote</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个新结点，并设置值等于当前结点的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使新结点的左结点指向当前结点的左结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 新结点的右结点指向当前结点的右结点的左结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使当前结点的值指向新结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使当前结点的右结点指向当前结点的右结点的右结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使当前结点的左结点指向新结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 右旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">rightRote</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前待插入结点的值小于当前结点，将其插入在左子树中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将当前结点插入右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果左子树的高度-右子树的高度 &gt; 1 进行右旋转 反之进行左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">leftHeight</span><span class="p">()</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">rightHeight</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果当前结点的左子树的右子树的高度&gt;当前结点左子树的左子树的高度 则进行左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">rightHeight</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">leftHeight</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 对当前结点的左结点进行左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">leftRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 对当前结点右旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">rightRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">rightRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">rightHeight</span><span class="p">()</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">leftHeight</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">leftHeight</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">rightHeight</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 对当前结点的右结点进行右旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">rightRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 对当前结点进行左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">leftRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">leftRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;value=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="多路查找树">多路查找树</h3>
+<p>在二叉树中，每个节点有数据项，最多有两个子节点。如果允许每个节点可以有更多的数据项和更多的子节点，就是多叉树（multiway tree）。多叉树通过重新组织节点，减少树的高度，能对二叉树进行优化。典型的多叉树有：2-3树、2-3-4树、红黑树和B树。</p>
+<p>多叉树的前提是有序二叉树。</p>
+<h4 id="2-3树">2-3树</h4>
+<p>2-3树是由二节点和三节点构成的树，是最简单的B树结构，2-3树的所有叶子节点都在同一层(只要是B树都满足这个条件)。</p>
+<ul>
+<li>有两个子节点的节点叫二节点，二节点要么没有子节点，要么有两个子节点；</li>
+<li>有三个子节点的节点叫三节点，三节点要么没有子节点，要么有三个子节点；</li>
+</ul>
+<p><img alt="数据结构与算法-032" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-032.png"></p>
+<p>2-3-4树，与2-3树类似。</p>
+<p><img alt="数据结构与算法-033" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-033.png"></p>
+<h4 id="b树">B树</h4>
+<p>B-tree 树即 B 树，B 即 Balanced ，平衡的意思。 B树通过重新组织节点，降低树的高度，并且减少i/o读写次数来提升效率。</p>
+<p>文件系统及数据库系统的设计者利用了磁盘预读原理，将一个节点的大小设为等于一个页(页的大小通常为4k)，这样每个节点只需要一次I/O就可以完全载入。</p>
+<blockquote>
+<p>B树的阶（度）：节点的最多子节点个数。比如2-3树的阶是3，2-3-4树的阶是4。</p>
+</blockquote>
+<p>B树的搜索，从根结点开始，对结点内的关键字（有序）序列进行二分查找，如果命中则结束，否则进入查询关键字所属范围的儿子结点；重复，直到所对应的儿子指针为空，或已经是叶子结点。</p>
+<p>B树的关键字集合分布在整颗树中，即叶子节点和非叶子节点都存放数据，搜索有可能在非叶子结点结束，其搜索性能等价于在关键字全集内做一次二分查找。</p>
+<p><img alt="数据结构与算法-034" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-034.png"></p>
+<h4 id="b树-1">B+树</h4>
+<p>B+树是B树的变体，也是一种多路搜索树。</p>
+<p>B+树的搜索与B树也基本相同，区别是B+树只有达到叶子结点才命中（B树可以在非叶子结点命中），其性能也等价于在关键字全集做一次二分查找。</p>
+<p>B+树所有关键字都出现在叶子结点的链表中（即数据只能在叶子节点【也叫稠密索引】），且链表中的关键字(数据)恰好是有序的。所以不可能在非叶子结点命中。</p>
+<p>B+树的所有叶结点构成一个有序链表，可以按照关键码排序的次序遍历全部记录， B+树更适合文件索引系统，B树和B+树各有自己的应用场景，不能说B+树完全比B树好，反之亦然。</p>
+<p><img alt="数据结构与算法-035" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-035.png"></p>
+<h4 id="b树-2">B*树</h4>
+<p>B* 树是B+树的变体，在B+树的非根和非叶子结点再增加指向兄弟的指针。</p>
+<p><img alt="数据结构与算法-036" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-036.png"></p>
+<h3 id="图">图</h3>
+<p>图是一种数据结构，其中结点可以具有零个或多个相邻元素。两个结点之间的连接称为边。结点也可以称为顶点。</p>
+<p>如果给图的每条边规定一个方向，那么得到的图称为有向图。在有向图中，与一个节点相关联的边有出边和入边之分。相反，边没有方向的图称为无向图。</p>
+<p><img alt="数据结构与算法-037" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-037.png"></p>
+<p>可用二维数组表示图（邻接矩阵）；或链表表示（邻接表）。</p>
+<p><img alt="数据结构与算法-038" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-038.png"></p>
+<p><img alt="数据结构与算法-039" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-039.png"></p>
+<p>用java模拟图，包括图的深度遍历，广度遍历。</p>
+<p><img alt="数据结构与算法-040" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-040.gif"></p>
+<p><img alt="数据结构与算法-041" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-041.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GraphDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">vertexes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;A&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;B&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;D&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;E&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertexes</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Graph</span><span class="w"> </span><span class="n">graph</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Graph</span><span class="p">(</span><span class="n">n</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">vertexes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">graph</span><span class="p">.</span><span class="na">addVertex</span><span class="p">(</span><span class="n">vertex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// A-B</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// A-C</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// B-C</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// B-D</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// B-E</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 展示图转换的矩阵</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">showEdges</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 图的深度遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">dfs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 图的广度遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">bfs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Graph</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 保存顶点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">vertexList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 保存边的数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">sideNums</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 保存图的矩阵</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">edges</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">isVisited</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="nf">Graph</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">vertexList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">n</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">edges</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">n</span><span class="o">][</span><span class="n">n</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sideNums</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取第一个结点的下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getFirstNeighbor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">index</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取当前结点的下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getNextNeighbor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">index</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 图的深度遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dfs</span><span class="p">(</span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">getVertexValByIndex</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将当前遍历后的顶点标记为true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">isVisited</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前结点的下一个结点的索引位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">firstNeighborIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getFirstNeighbor</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果 ！= -1 代表当前结点没有找到下一个结点，需要向下移动</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">firstNeighborIndex</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 判断该结点是否被遍历过</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isVisited</span><span class="o">[</span><span class="n">firstNeighborIndex</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dfs</span><span class="p">(</span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="n">firstNeighborIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 当前结点向后移动，否则是死循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">firstNeighborIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNextNeighbor</span><span class="p">(</span><span class="n">firstNeighborIndex</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dfs</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">isVisited</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">getVertexCount</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isVisited</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dfs</span><span class="p">(</span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 一个结点的广度优先遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">bfs</span><span class="p">(</span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 队列头结点下标索引</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">headIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 相邻结点下标索引</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">neighborIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">LinkedList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">queue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">getVertexValByIndex</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">isVisited</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">queue</span><span class="p">.</span><span class="na">addLast</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果队列不等于空 则需要遍历循环查找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">queue</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">headIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">queue</span><span class="p">.</span><span class="na">removeFirst</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 得到第一个邻接结点的下标</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">neighborIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getFirstNeighbor</span><span class="p">(</span><span class="n">headIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">neighborIndex</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 是否访问过</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isVisited</span><span class="o">[</span><span class="n">neighborIndex</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">getVertexValByIndex</span><span class="p">(</span><span class="n">neighborIndex</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">isVisited</span><span class="o">[</span><span class="n">neighborIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">queue</span><span class="p">.</span><span class="na">addLast</span><span class="p">(</span><span class="n">neighborIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// neighborIndex 向下找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">neighborIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNextNeighbor</span><span class="p">(</span><span class="n">headIndex</span><span class="p">,</span><span class="w"> </span><span class="n">neighborIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 广度优先遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">bfs</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">isVisited</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">getVertexCount</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isVisited</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bfs</span><span class="p">(</span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 添加顶点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addVertex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">vertex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">vertexList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">vertex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 添加边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addEdge</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">vertex1</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">vertex2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">edges</span><span class="o">[</span><span class="n">vertex1</span><span class="o">][</span><span class="n">vertex2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">edges</span><span class="o">[</span><span class="n">vertex2</span><span class="o">][</span><span class="n">vertex1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sideNums</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取边的数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getSideNums</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">sideNums</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 遍历矩阵</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showEdges</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">edge</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">edges</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">edge</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取顶点数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getVertexCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取边之间的权值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getVertexWeight</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">vertex1</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">vertex2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">vertex1</span><span class="o">][</span><span class="n">vertex2</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 根据下标获取结点的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getVertexValByIndex</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">vertexList</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="算法">算法</h2>
+<p>英文对应的单词是Algorithm，它的本意为：解决问题的方法，所以算法的直接理解就是解决问题的方法。在计算机领域定义的话就是：一系列解决问题的、清晰、可执行的计算机指令。</p>
+<p>一个算法的优劣可以用空间复杂度与时间复杂度来衡量。</p>
+<h3 id="算法复杂度">算法复杂度</h3>
+<h4 id="时间复杂度">时间复杂度</h4>
+<p>度量一个算法执行时间的两种方法：</p>
+<ul>
+<li>
+<p>事后统计法：即直接运行程序，统计需要的时间和空间。但是，这种方法有两个问题：</p>
+<ol>
+<li>结果非常依赖于测试环境。比如，用i3和用i8运行程序所需的时间是不同的;</li>
+<li>结果受测试规模的影响特别大。比如，对有序数组进行排序的时间比对逆序数组排序的时间短；对于小规模数据而言，插入排序所需时间比快速排序要短;</li>
+</ol>
+<p>所以，就需要有一种不用具体测试数据，也能估计算法执行效率的方法，就是算法复杂度分析，包括时间、空间复杂度分析。</p>
+</li>
+<li>
+<p>事前估算法：通过分析某个算法的时间复杂度来判断那个算法更优;</p>
+</li>
+</ul>
+<p>一般情况下，算法中的基本操作语句的重复执行次数是问题规模 n 的某个函数， 用<code>T(n)</code>表示，若有某个辅助函数<code>f(n)</code>，使得当 n 趋近于无穷大时，<code>T(n)/f(n)</code>的极限值为不等于零的常数，则称<code>f(n)</code>是<code>T(n)</code>的同数量级函数。记作 <code>T(n)=Ｏ(f(n))</code>， 称<code>Ｏ(f(n))</code>为算法的渐进时间复杂度，简称时间复杂度。</p>
+<p>例如，T(n) = n + 1 与 T(n) = n 就是同数量级函数，因为 n+1/n 的极限值为不等于零的常数。
+T(n) 不同，但时间复杂度可能相同: T(n)=n²+7n+6 与 T(n)=3n²+2n+2 它们的 T(n) 不同， 但时间复杂度相同，都为 O(n²)。</p>
+<p>计算时间复杂度的方法：</p>
+<ul>
+<li>用常数 1 代替运行时间中的所有加法常数： T(n)=n²+7n+6 =&gt; T(n)=n²+7n+1</li>
+<li>修改后的运行次数函数中，只保留最高阶项： T(n)=n²+7n+1 =&gt; T(n) = n²</li>
+<li>去除最高阶项的系数：T(n) = n² =&gt; T(n) = n² =&gt; O(n²)</li>
+</ul>
+<hr>
+<p><strong>时间频度</strong></p>
+<p>一个算法花费的时间与算法中的语句的执行次数成正比例,哪个算法执行次数多,他花费的时间就多.一个算法中的语句执行次数称为语句频度或时间频度.记为T(n)。</p>
+<p>随着时间的推移，一些复杂度花费时间无限接近：</p>
+<ol>
+<li>忽略常数项:</li>
+</ol>
+<ul>
+<li>2n+20 和 2n 随着 n 变大，执行曲线无限接近,20 可以忽略</li>
+<li>3n+10 和 3n 随着 n 变大，执行曲线无限接近,10 可以忽略</li>
+</ul>
+<ol start="2">
+<li>忽略低次项:</li>
+</ol>
+<ul>
+<li>2n²+3n+10 和 2n² 随着 n 变大, 执行曲线无限接近,可以忽略 3n+10</li>
+<li>n²+5n+20 和 n² 随着 n 变大,执行曲线无限接近,可以忽略 5n+20</li>
+</ul>
+<ol start="3">
+<li>忽略系数:</li>
+</ol>
+<ul>
+<li>随着 n 值变大， 5n²+7n 和 3n² + 2n ，执行曲线重合, 说明这种情况下, 5 和 3 可以忽略</li>
+<li>对于 n^3+5n 和 6n^3+4n，执行曲线分离，不能忽略系数，说明多少次方是关键</li>
+</ul>
+<hr>
+<p><strong>常见的时间复杂度</strong></p>
+<ul>
+<li>
+<p>常数阶 O(1): 无论代码执行了多少行，只要是没有循环等复杂结构，这个代码的时间复杂度就都是O(1)；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">int i = 1;
+</span></span><span class="line"><span class="cl">int j = 2;
+</span></span><span class="line"><span class="cl">++i;
+</span></span><span class="line"><span class="cl">j++;
+</span></span><span class="line"><span class="cl">int m = i + j;
+</span></span></code></pre></div></li>
+<li>
+<p>对数阶 O(log2n)</p>
+<p><img alt="数据结构与算法-012" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-012.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">int i = 1;
+</span></span><span class="line"><span class="cl">while(i&lt;n){
+</span></span><span class="line"><span class="cl">    i = i*2;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>线性阶 O(n): 它消耗的时间是随着n的变化而变化的,与n成正比或反比；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(int i=1; i&lt;=n; ++i){
+</span></span><span class="line"><span class="cl">    j = i;
+</span></span><span class="line"><span class="cl">    j++;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>线性对数阶 O(nlog2n): 将时间复杂度为O(logn)的代码循环n遍，那么它的时间复杂度就是 n * O(logN)，也就是了O(nlogN);</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(int m=1; m&lt;=n; ++m){
+</span></span><span class="line"><span class="cl">    int i = 1;
+</span></span><span class="line"><span class="cl">    while(i&lt;n){
+</span></span><span class="line"><span class="cl">        i = i*2;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>平方阶 O(n^2): 如果把 O(n) 的代码再嵌套循环一遍，它的时间复杂度就是 O(n²)，这段代码其实就是嵌套了2层n循环，它的时间复杂度就是 <code>O(n*n)</code>，即 O(n²) 如果将其中一层循环的n改成m，那它的时间复杂度就变成了 <code>O(m*n)</code>;</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(int i=1; i&lt;=n; ++i){
+</span></span><span class="line"><span class="cl">    for(int j=1; j&lt;=n; ++j){
+</span></span><span class="line"><span class="cl">        j=i;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>立方阶 O(n^3)</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(int i=1; i&lt;=n; ++i){
+</span></span><span class="line"><span class="cl">    for(int j=1; j&lt;=n; ++j){
+</span></span><span class="line"><span class="cl">        for(int x=1; x&lt;=n; ++x){
+</span></span><span class="line"><span class="cl">            int m = 0;
+</span></span><span class="line"><span class="cl">            i = x+j;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>k 次方阶 O(n^k)</p>
+</li>
+<li>
+<p>指数阶 O(2^n)</p>
+</li>
+</ul>
+<p>常见的算法时间复杂度由小到大依次为：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Ο (1)＜Ο (log2n)＜Ο (n)＜Ο (nlog2n)＜Ο (n2)＜Ο (n3)＜ Ο (nk) ＜ Ο (2n)
+</span></span></code></pre></div><p>随着问题规模 n 的不断增大，上述时间复杂度不断增大，算法的执行效率越低。</p>
+<h4 id="空间复杂度">空间复杂度</h4>
+<p>类似于时间复杂度的讨论，一个算法的空间复杂度(Space Complexity)定义为该算法所耗费的存储空间，它也是问题规模 n 的函数。</p>
+<p>空间复杂度全称为渐进空间复杂度，是对一个算法在运行过程中临时占用存储空间大小的量度。 有的算法需要占用的临时工作单元数与解决问题的规模 n 有关， 它随着 n 的增大而增大， 当 n 较大时， 将占用较多的存储单元， 例如快速排序和归并排序算法, 基数排序就属于这种情况
+在做算法分析时， 主要讨论的是时间复杂度。 从用户使用体验上看， 更看重的程序执行的速度。 一些缓存产品(redis, memcache)和算法(基数排序)本质就是用空间换时间</p>
+<p>空间复杂度较为简单，常见的空间复杂度为 O(1)，O(n) 和 O(n ^ 2)。</p>
+<h3 id="递归">递归</h3>
+<p>递归就是方法自己调用自己，每次调用时传入不同的变量，递归有助于编程者解决复杂的问题，同时可以让代码变得简洁。</p>
+<p><strong>递归能解决什么问题？</strong></p>
+<ul>
+<li>各种数学问题如: 8 皇后问题，汉诺塔，阶乘问题，迷宫问题，球和篮子的问题(google 编程大赛)；</li>
+<li>各种算法中也会使用到递归， 比如快排， 归并排序， 二分查找， 分治算法等；</li>
+<li>用栈解决的问题，使用递归替换代码更佳简洁；</li>
+</ul>
+<p>使用递归遵守的规则：</p>
+<ul>
+<li>执行一个方法时，就创建一个新的受保护的独立空间(一个线程有自己独立的一个栈空间，每个方法调用对应着一个栈帧)；</li>
+<li>方法的局部变量是独立的，不会相互影响；</li>
+<li>如果方法中使用的是引用类型变量，就会共享该引用类型的数据，比如数组；</li>
+<li>递归必须向退出递归的条件逼近，否则就是无限递归，出现 StackOverflowError；</li>
+<li>当一个方法执行完毕，或者遇到return，就会返回，遵守谁调用，就将结果返回给谁，同时当方法执行完毕或者返回时，该方法也就执行完毕；</li>
+</ul>
+<h4 id="迷宫回溯">迷宫回溯</h4>
+<p>迷宫回溯问题，寻找最短路径可以通过改变策略，将每个策略都经过的路保存在集合中，最后看哪个集合最小即最小路径。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Mazeback</span><span class="w"> </span><span class="n">mazeback</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Mazeback</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mazeback</span><span class="p">.</span><span class="na">createMap</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mazeback</span><span class="p">.</span><span class="na">list</span><span class="p">(</span><span class="n">map</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;自动寻找路线：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mazeback</span><span class="p">.</span><span class="na">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mazeback</span><span class="p">.</span><span class="na">list</span><span class="p">(</span><span class="n">map</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Mazeback</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 创建地图</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="nf">createMap</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 地图</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">7</span><span class="o">][</span><span class="n">8</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">7</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">7</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">6</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="o">[</span><span class="n">3</span><span class="o">][</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="o">[</span><span class="n">3</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">map</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历地图</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">map</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">map</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">map</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 寻找路径</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 1：墙；2：通路，3：死路</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">setWay</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">column</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="o">[</span><span class="n">5</span><span class="o">][</span><span class="n">6</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 先假设是通路</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 寻找路径顺序：下，右，上，左</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 当标记为3时，说明是死路走不通</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">map</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="八皇后问题">八皇后问题</h4>
+<p>八皇后问题，是一个古老而著名的问题，是回溯算法的典型案例。该问题是国际西洋棋棋手马克斯·贝瑟尔于1848 年提出：在 8 × 8 格的国际象棋上摆放八个皇后，使其不能互相攻击， 即： 任意两个皇后都不能处于同一行、同一列或同一斜线上，问有多少种摆法。</p>
+<blockquote>
+<p>八皇后问题共92中解法</p>
+</blockquote>
+<p><img alt="数据结构与算法-010" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-010.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EightQueens</span><span class="w"> </span><span class="n">eightQueens</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EightQueens</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">eightQueens</span><span class="p">.</span><span class="na">exec</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">EightQueens</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">max</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">EightQueens</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">8</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">max</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 算法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">position</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前位置等于max说明解法成立，需要回溯</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">position</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">max</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">print</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">max</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">check</span><span class="p">(</span><span class="n">position</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">exec</span><span class="p">(</span><span class="n">position</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 判断皇后位置是否冲突</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">check</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">position</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">position</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断是否在同一列或在同一斜线上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">abs</span><span class="p">(</span><span class="n">position</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">abs</span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 打印数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">print</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="排序算法">排序算法</h3>
+<p>排序也称排序算法，是将一组数据，依指定的顺序进行排列的过程。</p>
+<p>排序算法分类：</p>
+<ul>
+<li>内部排序：指将需要处理的所有数据都加载到内部存储器(内存)中进行排序；</li>
+<li>外部排序法：数据量过大，无法全部加载到内存中，需要借助外部存储(文件等)进行排序；</li>
+</ul>
+<p><img alt="数据结构与算法-011" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-011.png"></p>
+<p>常见内排序算法复杂度比较</p>
+<p><img alt="数据结构与算法-013" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-013.png"></p>
+<p>名词解释：</p>
+<ul>
+<li>n：数据规模</li>
+<li>k：&ldquo;桶&quot;的个数</li>
+<li>In-place：占用常数内存，不占用额外内存</li>
+<li>Out-place：占用额外内存</li>
+<li>稳定性：排序后两个相等键值的顺序和排序之前它们的顺序相同，不稳定性则相反</li>
+<li>时间复杂度：一个算法执行所耗费的时间</li>
+<li>空间复杂度：运行完一个程序所需内存的大小</li>
+</ul>
+<h4 id="冒泡排序">冒泡排序</h4>
+<p>冒泡排序的基本思想是：通过对待排序序列从前向后（从下标较小的元素开始），依次比较相邻元素的值，若发现逆序（当前值大于比较的值）则交换，使值较大的元素逐渐从前移向后部，就像水底下的气泡一样逐渐向上冒。</p>
+<p><img alt="数据结构与算法-014" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-014.gif"></p>
+<p>优化：因为排序的过程中， 各元素不断接近自己的位置，如果一趟比较下来没有进行过交换，就说明序列有序，因此要在排序过程中设置一个标志 flag 判断元素是否进行过交换。 从而减少不必要的比较。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BubbleSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="n">len</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将当前值与next值进行比较，如果当前值大于next值则交换两者之间的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">1</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 加入标志为进行判断，如果整个循环下啦都没有交换位置，说明该数组是有序的，所以直接退出循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">flag</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="选择排序">选择排序</h4>
+<p>选择式排序也属于内部排序法，是从欲排序的数据中，按指定的规则选出某一元素，再依规定交换位置后达到排序的目的。</p>
+<p>首先在未排序序列中找到最小元素，存放到排序序列的起始位置，然后，再从剩余未排序元素中继续寻找最小元素，然后放到排序序列末尾。以此类推，直到所有元素均排序完毕。</p>
+<p><img alt="数据结构与算法-015" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-015.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">SelectSorting</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 如果next值大于当前值，则记录该值和该值的位置，等全部比较完毕后，将最大的一个与数据的末尾进行替换</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">j</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将每次循环中的最小的值，调整到最前面</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">min</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">i</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">min</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">data</span><span class="o">[</span><span class="n">min</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="插入排序">插入排序</h4>
+<p>插入排序（Insertion Sorting） 的基本思想是：把 n 个待排序的元素看成为一个有序表和一个无序表;</p>
+<p>开始时有序表中只包含一个元素，无序表中包含有 n-1 个元素，排序过程中每次从无序表中取出第一个元素，把它的排序码依次与有序表元素的排序码进行比较， 将它插入到有序表中的适当位置，使之成为新的有序表。</p>
+<p>对于未排序数据，在已排序序列中从后向前扫描，找到相应位置并插入。插入排序在实现上，通常在从后向前扫描过程中，需要反复把已排序元素逐步向后挪位，为最新元素提供插入空间。</p>
+<p><img alt="数据结构与算法-016" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-016.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">InsertSorting</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果当前要插入的值 data[i] &gt; 有序队列中最后一个，则将其直接插入到最后一个</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果当前位置的值【tmp】小于 上一个位置的值【data[index]】说明当前值需要插入到有序队列中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">index</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="希尔排序">希尔排序</h4>
+<p>希尔排序是希尔（Donald Shell） 于1959年提出的一种排序算法。希尔排序也是一种插入排序，它是简单插入排序经过改进之后的一个更高效的版本，也称为缩小增量排序。</p>
+<p>希尔排序按照增量将数组进行分组，对每组使用直接插入排序算法排序；随着增量逐渐减少，每组包含的关键词越来越多，当增量减至1时，整个文件恰被分成一组，算法便终止。</p>
+<p><img alt="数据结构与算法-017" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-017.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">ShellSorting</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 希尔排序，交换法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sortSwap</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数据分组，分组数量：data.length/2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;&gt;=</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">gap</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 遍历每组中的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">gap</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">gap</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 将每组中的元素进行排序（交换元素）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">gap</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">gap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">gap</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 插入法，融入 插入排序 思想</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数据分组，分组数量：data.length/2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;&gt;=</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">gap</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 如果当前位置的值【tmp】小于 上一个位置的值【data[index]】说明当前值需要插入到有序队列中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">gap</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">gap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">index</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">gap</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="快速排序">快速排序</h4>
+<p>快速排序是由东尼·霍尔所发展的一种排序算法。在平均状况下，排序n个项目要 Ο(nlogn) 次比较。在最坏状况下则需要 Ο(n2) 次比较，但这种状况并不常见。事实上，快速排序通常明显比其他 Ο(nlogn) 算法更快，因为它的内部循环可以在大部分的架构上很有效率地被实现出来。</p>
+<p>快速排序又是一种分而治之思想在排序算法上的典型应用。本质上来看，快速排序应该算是在冒泡排序基础上的递归分治法。快速排序思路：</p>
+<ul>
+<li>选定pivot基准数</li>
+<li>将大于pivot基准数放在基准数右边</li>
+<li>将小于pivot基准数放在基准数左边</li>
+</ul>
+<p><img alt="数据结构与算法-018" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-018.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">QuickSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果开始的位置大于等于结束的位置则不用进行比较直接退出</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">l</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">r</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">l</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">r</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 基准数值，将小于该数值的放在该数字的左边，大于该数值的放在右边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">pivot</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从右向左开始比较，如果此数大于等于基准数则将right索引向前移动，否则，将该值覆盖到对应的 data[left] 中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">right</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">pivot</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">--</span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">right</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从左向右开始比较，如果此数小于等于基准数则将left索引向后移动，否则，将该值覆盖到对应的 data[right] 中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">pivot</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">++</span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="o">[</span><span class="n">right</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 此时left与right指向重合的位置为基准所在的位置，需要将该位置覆盖掉为基准的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pivot</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 递归排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sort</span><span class="p">(</span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n">left</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sort</span><span class="p">(</span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="n">r</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w"> 
+</span></span></span></code></pre></div><h4 id="归并排序">归并排序</h4>
+<p>归并排序是利用归并的思想实现的排序方法， 该算法采用经典的分治（divide-and-conquer）策略；分治法将问题分成一些小的问题然后递归求解， 而治的阶段则将分的阶段得到的各答案&quot;修补&quot;在一起，即分而治之。</p>
+<p>归并排序算法思路：采用分治算法思想，首先将序列使用递归进行拆分，然后进行合并；合并思路，将两个有序队列中的元素分别按顺序进行比较，将结果保存在一个临时数组中，最后将临时数组合并到最后的队列中。</p>
+<p><img alt="数据结构与算法-019" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-019.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MergeSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 递归拆分算法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 分别向左向右递归</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">divide</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="p">,</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">divide</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 拆分一次合并一次</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">merge</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 合并算法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">merge</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">leftIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">start</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">rightIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmpArrIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断是否超出范围</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">leftIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">rightIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将两组数据进行比较，按照从小到大的顺序将两组数据填入 tmpArr 中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">leftIndex</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">rightIndex</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">leftIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">++</span><span class="n">leftIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">rightIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">++</span><span class="n">rightIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpArrIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断两组数据是否还有剩余，如果有剩余数据，则直接将数据追加到 tmpArr 数组后边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">leftIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">mid</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">leftIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">leftIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpArrIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">rightIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">rightIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">rightIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpArrIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将两组数据进行合并</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tmpArrIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmpLeftIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leftIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpLeftIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">tmpLeftIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpLeftIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpArrIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="基数排序">基数排序</h4>
+<p>基数排序是 1887 年赫尔曼·何乐礼发明的。基数排序属于“分配式排序”，又称“桶子法”或 bin sort，顾名思义，它是通过键值的各个位的值，将要排序的元素分配至某些“桶”中，达到排序的作用,基数排序法是属于稳定性的排序， 基数排序法的是效率高的稳定性排序法。</p>
+<p>基数排序是桶排序的扩展，它是这样实现的： 将所有待比较数值统一为同样的数位长度，数位较短的数前面补零；然后， 从最低位开始， 依次进行一次排序。这样从最低位排序一直到最高位排序完成以后, 数列就变成一个有序序列。</p>
+<p><img alt="数据结构与算法-020" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-020.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BucketSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 求数组中最大数的长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">maxNum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">maxNum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">maxNum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">maxNumLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">maxNum</span><span class="p">).</span><span class="na">length</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 桶，用于保存数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">buckets</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">][</span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存放每个桶的保存数据的索引</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">bucketElementIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数组中的元素 按照 个、十、百、千 …… 的顺序依次放入桶中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">maxNumLen</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">*=</span><span class="w"> </span><span class="n">10</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 遍历二维数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 计算放入的桶的下标</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">buckets</span><span class="o">[</span><span class="n">index</span><span class="o">][</span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">index</span><span class="o">]]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">index</span><span class="o">]++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从桶中依次取出元素并放入原数组中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">bucketElementIndex</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">f</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 判断桶中是否保存数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">f</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">f</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="n">h</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">arr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buckets</span><span class="o">[</span><span class="n">f</span><span class="o">][</span><span class="n">h</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">f</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="堆排序">堆排序</h4>
+<p>堆排序是利用堆这种数据结构而设计的一种排序算法，堆排序是一种选择排序，它的最坏、最好、平均时间复杂度均为O(nlogn)，它也是不稳定排序。</p>
+<p>堆排序的基本思想是：将待排序序列构造成一个大顶堆，此时，整个序列的最大值就是堆顶的根节点。将其与末尾元素进行交换，此时末尾就为最大值。然后将剩余n-1个元素重新构造成一个堆，这样会得到n个元素的次小值。如此反复执行，便能得到一个有序序列了。</p>
+<blockquote>
+<p>大顶堆：每个节点的值都大于或等于其子节点的值，在堆排序算法中用于升序排列；
+小顶堆：每个节点的值都小于或等于其子节点的值，在堆排序算法中用于降序排列；</p>
+</blockquote>
+<p><img alt="数据结构与算法-027" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-027.png"></p>
+<p><img alt="数据结构与算法-026" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-026.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">HeapSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 计算树中的叶子结点位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">leafNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 构建大顶堆，此处需要注意 i &gt;= 0 需要算根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leafNode</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">--</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">buildMaxHeap</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 构建大顶堆后，将根元素与树中的最后一个进行交换，再循环构建大顶堆</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">--</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">buildMaxHeap</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 堆排序核心代码 构建大顶堆
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param arr 需要调整的数组
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param i   非叶子结点的索引位置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param len 每次调整的长度
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">buildMaxHeap</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存非叶子结点的位置如果该结点的值小于子结点的值，则需要进行交换</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 从上至下，从左至右 遍历. 从第一个左子结点开始遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果左子结点 &lt; 右结点，则需要将 n 指向右结点，即后移</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">n</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">n</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当前非叶子结点 &lt; 当前子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">n</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">tmp</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将当前非叶子结点指向叶子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">n</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将i指向当前叶子结点，待最后将其变为 非叶子结点的值 即tmp的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 与前面互相呼应</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="查找算法">查找算法</h3>
+<h4 id="线性查找">线性查找</h4>
+<p>线性查找又称顺序查找，是一种最简单的查找方法，它的基本思想是从第一个记录开始，逐个比较记录的关键字，直到和给定的K值相等，则查找成功；若比较结果与文件中n个记录的关键字都不等，则查找失败。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">LinearSearch</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="二分查找">二分查找</h4>
+<p>二分查找也称折半查找，它是一种效率较高的查找方法。但是，折半查找要求线性表必须采用顺序存储结构，而且表中元素按关键字有序排列。</p>
+<p><strong>二分查找算法的前提，数组必须是有序数组，如果没有有序列表，请使用<a href="/iblog/posts/essays/data-structures-algorithms/#%E6%8E%92%E5%BA%8F%E7%AE%97%E6%B3%95">排序算法</a>对列表进行排序。</strong></p>
+<p>递归实现二分查找</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BinarySearch</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 使用二分查找时，arr必须为有序列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 在 {@param arr} 中 没有查到 {@param value}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">end</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">start</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取中间值，用于分割列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">midVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果 查找的值&lt; 中间值，说明该值可能在mid的左边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">midVal</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 相反如果 查找的值 &gt; 中间值，说明该值可能在mid的右边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">midVal</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用递归不停的向下细分，当 value == arr[mid] 时 返回该值，说明此时已经找到了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>非递归实现二分查找</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BinarySearchDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">10</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BinarySearch</span><span class="p">().</span><span class="na">search</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BinarySearch</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 使用二分查找时，arr必须为有序列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">mid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果目标值小于中间值则向左边找，反之向右边找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="插值查找">插值查找</h4>
+<p>插值查找算法类似于二分查找，与二分查找不同的是插值查找每次从自适应 mid 处开始查找，而不是像二分查找那样每次都从中间开始找。</p>
+<p><img alt="数据结构与算法-021" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-021.png"></p>
+<p>注意：对于数据量较大，关键字分布比较均匀（最好是线性分布）的查找表来说，采用插值查找，速度较快；对于关键字分布不均匀的情况下，该方法不一定比二分查找要好。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">InsertValueSearch</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 与二分查找基本相同，只是查找 mid 值发生了变动</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 在 {@param arr} 中 没有查到 {@param value}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">end</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">start</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">start</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">end</span><span class="o">]</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">start</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p">(</span><span class="n">end</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">start</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">midVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">midVal</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">midVal</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="斐波那契查找">斐波那契查找</h4>
+<p>斐波那契查找是基于【黄金分割】的二分查找。即在斐波那契队列中，将二分查找中的分割点替换为黄金分割点，来查找。</p>
+<blockquote>
+<p>黄金分割是指将整体一分为二，较大部分与整体部分的比值等于较小部分与较大部分的比值，其 比值 约为 0.618。这个比例被公认为是最能引起美感的 比例，因此被称为黄金分割。</p>
+</blockquote>
+<p>斐波那契查找特点：</p>
+<ul>
+<li>平均性能「斐波那契查找」好于「二分查找」；</li>
+<li>「斐波那契查找」计算 mid 的时候 使用加减法而不是除法，会微弱提升效率；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">FibonacciSearch</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// lookupTable,需要传入斐波那契数列,例如：{1,1,2,3,5,8,13,21,34,55};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">lookupTable</span><span class="p">,</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">f</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">low</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">high</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lookupTable</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// k 是 Fibonacci 分割数组下标</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">middle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="o">[</span><span class="n">k</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">high</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">k</span><span class="w"> </span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//利用 java 工具类构造 f[k] 长度的查找表，解决原有查找表元素不够的问题</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">temp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">lookupTable</span><span class="p">,</span><span class="n">f</span><span class="o">[</span><span class="n">k</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">low</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">high</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">middle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">low</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">f</span><span class="o">[</span><span class="n">k</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">lookupTable</span><span class="o">[</span><span class="n">middle</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">high</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">middle</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">k</span><span class="w"> </span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">lookupTable</span><span class="o">[</span><span class="n">middle</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">low</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">middle</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">k</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">middle</span><span class="p">,</span><span class="n">high</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="哈夫曼编码">哈夫曼编码</h3>
+<p>赫夫曼编码也翻译为哈夫曼编码(Huffman Coding)，又称霍夫曼编码，是一种编码方式，属于一种程序算法。</p>
+<p>哈夫曼编码是哈夫曼树在电讯通信中的经典的应用之一。哈夫曼编码广泛地用于数据文件压缩。其压缩率通常在20%～90%之间。哈夫曼码是可变字长编码的一种。Huffman于1952年提出一种编码方法，称之为最佳编码。</p>
+<blockquote>
+<p>定长编码与变长编码，以字符串like like为例：</p>
+<ul>
+<li>定长编码：</li>
+</ul>
+<ol>
+<li>将上述字符串转换对应的ASCII： 108 105 107 101 32 108 105 107 101</li>
+<li>ASCII转换为二进制：01101100 01101001 01101011 01100101 00100000 01101100 01101001 01101011 01100101
+<br></li>
+</ol>
+<ul>
+<li>变长编码：</li>
+</ul>
+<ol>
+<li>统计上述字符串出现的各字符出现的次数：l：2 i：2 k：2 e：2 ：1</li>
+<li>按照各个字符出现的次数进行编码，原则是出现次数越多的，则编码越小：0=l 1=i 10=k 11=e 100=</li>
+<li>最终转换为变长编码为：011011100011011</li>
+</ol>
+</blockquote>
+<p>上述的变长编码 011011100011011 在解码的时候会出现多意现象，比如当匹配到数字1，是把1解成i还是按照10来进行解码。因为这种现象的存在，所以在进行变长编码时，编码要符合前缀编码。</p>
+<blockquote>
+<p>字符的编码都不能是其他字符编码的前缀，符合此要求的编码叫做前缀编码， 即不能匹配到重复的编码。</p>
+</blockquote>
+<p>构建哈夫曼编码思路：</p>
+<ol>
+<li>统计字节数组中各个数据的权重,即字符出现的次数；</li>
+<li>将统计好的字符出现的次数，<a href="/iblog/posts/essays/data-structures-algorithms/#%E5%93%88%E5%A4%AB%E6%9B%BC%E6%A0%91">构建成哈夫曼树</a>；</li>
+<li>根据上面创建的哈夫曼树获得每个数值对应的可变长编码值，规定结点的左边为0 ，右边为1；</li>
+<li>以每个数值新的编码重新对字符数组进行编码，即可得到赫夫曼编码后的值；</li>
+</ol>
+<p>假如一段信息里只有A，B，C，D，E，F这6个字符，他们出现的次数依次是2次，3次，7次，9次，18次，25次，最终构建成哈夫曼编树为下图所示：</p>
+<p><img alt="数据结构与算法-029" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-029.png"></p>
+<p>得到哈夫曼编码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">A=11100 B=11101 C=1111 D=110 E=10 F=0
+</span></span></code></pre></div><p>利用哈夫曼编码，压缩解压文件：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HuffmanCodeTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 测试压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">srcFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/Desktop/1.png&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">dstFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/Desktop/1.zip&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">zipFile</span><span class="p">(</span><span class="n">srcFile</span><span class="p">,</span><span class="w"> </span><span class="n">dstFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;压缩文件成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 测试解压文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">srcFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/Desktop/1.zip&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dstFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/Desktop/1copy.png&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">unZipFile</span><span class="p">(</span><span class="n">srcFile</span><span class="p">,</span><span class="w"> </span><span class="n">dstFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;解压成功!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将一个文件进行压缩</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">zipFile</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">srcFile</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">dstFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建输出流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OutputStream</span><span class="w"> </span><span class="n">os</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建文件的输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FileInputStream</span><span class="w"> </span><span class="n">is</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建文件的输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">is</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">srcFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建一个和源文件大小一样的byte[]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">is</span><span class="p">.</span><span class="na">available</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 读取文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">is</span><span class="p">.</span><span class="na">read</span><span class="p">(</span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanCode</span><span class="w"> </span><span class="n">huffmanCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 直接对源文件压缩</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanCode</span><span class="p">.</span><span class="na">encode</span><span class="p">(</span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建文件的输出流, 存放压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">os</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="n">dstFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建一个和文件输出流关联的ObjectOutputStream</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="n">os</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 把 赫夫曼编码后的字节数组写入压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">huffmanBytes</span><span class="p">);</span><span class="w"> </span><span class="c1">// 我们是把</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 这里我们以对象流的方式写入 赫夫曼编码，是为了以后我们恢复源文件时使用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 注意一定要把赫夫曼编码 写入压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">huffmanCode</span><span class="p">.</span><span class="na">getHuffmanCodes</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// TODO: handle exception</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">is</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">oos</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">os</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// TODO: handle exception</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 完成对压缩文件的解压</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unZipFile</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">zipFile</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">dstFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 定义文件输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">InputStream</span><span class="w"> </span><span class="n">is</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 定义一个对象输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 定义文件的输出流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OutputStream</span><span class="w"> </span><span class="n">os</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建文件输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">is</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">zipFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建一个和 is关联的对象输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ois</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="n">is</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 读取byte数组 huffmanBytes</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 读取赫夫曼编码表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanCode</span><span class="w"> </span><span class="n">huffmanCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 解码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanCode</span><span class="p">.</span><span class="na">decode</span><span class="p">(</span><span class="n">huffmanCodes</span><span class="p">,</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将bytes 数组写入到目标文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">os</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="n">dstFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 写数据到 dstFile 文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">os</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="n">bytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// TODO: handle exception</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">os</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">ois</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">is</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// TODO: handle exception</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e2</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HuffmanCode</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getHuffmanCodes</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 生成 huffman 编码 压缩</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="nf">encode</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildHuffmanNodes</span><span class="p">(</span><span class="n">bytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">huffmanTreeRoot</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildHuffmanTree</span><span class="p">(</span><span class="n">nodes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">huffmanTreeRoot</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">zip</span><span class="p">(</span><span class="n">bytes</span><span class="p">,</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将 huffman编码 解码 解压缩</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="nf">decode</span><span class="p">(</span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">,</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">stringBuilder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将byte数组转成二进制的字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">strToAppend</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">byteToBitString</span><span class="p">(</span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断是不是最后一个字节</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isLastByte</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isLastByte</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 得到最后一个字节的有效位数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">byte</span><span class="w"> </span><span class="n">validBits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="o">[</span><span class="n">huffmanBytes</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">strToAppend</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">strToAppend</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">validBits</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">strToAppend</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 把字符串按照指定的赫夫曼编码进行解码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 把赫夫曼编码表进行调换，因为反向查询 a-&gt;100 100-&gt;a</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Byte</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">huffmanCodes</span><span class="p">.</span><span class="na">forEach</span><span class="p">((</span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建要给集合，存放byte</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Byte</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// i 可以理解成就是索引,扫描 stringBuilder</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 递增的取出 key</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">String</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">count</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">b</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 没有匹配到</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 匹配到</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">i</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">IntStream</span><span class="p">.</span><span class="na">range</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">.</span><span class="na">length</span><span class="p">).</span><span class="na">forEach</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">b</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算字符串中每个字符出现的次数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">buildHuffmanNodes</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 利用map记录集合中元素出现的次数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">counts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">counts</span><span class="p">.</span><span class="na">merge</span><span class="p">(</span><span class="n">b</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">::</span><span class="n">sum</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 把每一个键值对转成一个Node 对象，并加入到nodes集合</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">counts</span><span class="p">.</span><span class="na">forEach</span><span class="p">((</span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构建Huffman树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">buildHuffmanTree</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">nodes</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 排序, 从小到大</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Collections</span><span class="p">.</span><span class="na">sort</span><span class="p">(</span><span class="n">nodes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 取出第一颗最小的二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">leftNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 取出第二颗最小的二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">rightNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建一颗新的二叉树,它的根节点 没有data, 只有权值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">parent</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">leftNode</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">rightNode</span><span class="p">.</span><span class="na">weight</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">parent</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leftNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">parent</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rightNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将已经处理的两颗二叉树从nodes删除</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">nodes</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">leftNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">nodes</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">rightNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将新的二叉树，加入到nodes</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">nodes</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">parent</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// nodes 最后的结点，就是赫夫曼树的根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 重载 getCodes</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理root的左子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">root</span><span class="p">.</span><span class="na">left</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;0&#34;</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理root的右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">root</span><span class="p">.</span><span class="na">right</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取huffman编码表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">code</span><span class="p">,</span><span class="w"> </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">curNodeCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">(</span><span class="n">stringBuilder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">curNodeCode</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">code</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断当前node 是叶子结点还是非叶子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">data</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// 非叶子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 向左递归</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">left</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;0&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">curNodeCode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 向右递归</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">right</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">curNodeCode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 表示找到某个叶子结点的最后</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">huffmanCodes</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">data</span><span class="p">,</span><span class="w"> </span><span class="n">curNodeCode</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 压缩传入字节（将传入字符串转成字节类型）将待压缩字节转换为字节数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="nf">zip</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">,</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 利用 huffmanCodes 将 bytes 转成 赫夫曼编码对应的字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">stringBuilder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历bytes 数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">huffmanCodes</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">b</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 统计返回 byte[] huffmanCodeBytes 长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 等同于 int len = (stringBuilder.length() + 7) / 8;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="w"> </span><span class="n">countToEight</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">countToEight</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">3</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 后面补零</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">countToEight</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">8</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="s">&#34;0&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建 存储压缩后的 byte数组，huffmanCodeBytes[len]记录赫夫曼编码最后一个字节的有效位数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">huffmanCodeBytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">len</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">huffmanCodeBytes</span><span class="o">[</span><span class="n">len</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">countToEight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 因为是每8位对应一个byte,所以步长 +8</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">8</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">strByte</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">strByte</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">8</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将strByte 转成一个byte,放入到 huffmanCodeBytes</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">huffmanCodeBytes</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">parseInt</span><span class="p">(</span><span class="n">strByte</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">huffmanCodeBytes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将 byte 转换为对应的字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">byteToBitString</span><span class="p">(</span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">temp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果是正数我们需要将高位补零</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">temp</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">0x100</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 转换为二进制字符串，正数：高位补 0 即可，然后截取低八位即可；负数直接截取低八位即可</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 负数在计算机内存储的是补码，补码转原码：先 -1 ，再取反</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">binaryStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">toBinaryString</span><span class="p">(</span><span class="n">temp</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">binaryStr</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">binaryStr</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">8</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Comparable</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Byte</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="n">Byte</span><span class="w"> </span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">compareTo</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">o</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 从小到大排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">o</span><span class="p">.</span><span class="na">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node [data = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; weight=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">weight</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;]&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="分治算法">分治算法</h3>
+<p>分治法是一种很重要的算法。字面上的解释是“分而治之”，就是把一个复杂的问题分成两个或更多的相同或相似的子问题，再把子问题分成更小的子问题……直到最后子问题可以简单的直接求解，原问题的解即子问题的解的合并。这个技巧是很多高效算法的基础，如排序算法(快速排序，归并排序)，傅立叶变换(快速傅立叶变换)……</p>
+<p>分治法的设计思想是：将一个难以直接解决的大问题，分割成一些规模较小的相同问题，以便各个击破，分而治之。</p>
+<p>使用分治算饭解决汉诺塔问题</p>
+<blockquote>
+<p>汉诺塔（又称河内塔）问题是源于印度一个古老传说的益智玩具。大梵天创造世界的时候做了三根金刚石柱子，在一根柱子上从下往上按照大小顺序摞着64片黄金圆盘。大梵天命令婆罗门把圆盘从下面开始按大小顺序重新摆放在另一根柱子上。并且规定，在小圆盘上不能放大圆盘，在三根柱子之间一次只能移动一个圆盘。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HanoiTowerDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HanoiTower</span><span class="w"> </span><span class="n">hanoiTower</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HanoiTower</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hanoiTower</span><span class="p">.</span><span class="na">hanoiTower</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HanoiTower</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">hanoiTower</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">b</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">c</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将a塔上面除了底盘外的所有盘移动到b塔</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hanoiTower</span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">c</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将a塔遗留的底盘移动到c塔</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将b塔上面的所有盘移动到c塔</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hanoiTower</span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="动态规划算法">动态规划算法</h3>
+<p>动态规划(Dynamic Programming)算法的核心思想是：将大问题划分为小问题进行解决，从而一步步获取最优解的处理算法。</p>
+<p>动态规划算法与分治算法类似，其基本思想也是将待求解问题分解成若干个子问题，先求解子问题，然后从这些子问题的解得到原问题的解。与分治法不同的是，适合于用动态规划求解的问题，经分解得到子问题往往不是互相独立的。 ( 即下一个子阶段的求解是建立在上一个子阶段的解的基础上，进行进一步的求解 )</p>
+<p>关于动态规划最经典的问题当属背包问题。</p>
+<blockquote>
+<p>背包问题主要是指一个给定容量的背包、若干具有一定价值和重量的物品，如何选择物品放入背包使物品的价值最大。其中又分01背包和完全背包(完全背包指的是：每种物品都有无限件可用)这里的问题属于01背包，即每个物品最多放一个。而无限背包可以转化为01背包。</p>
+<table>
+<thead>
+<tr>
+<th>物品</th>
+<th>重量</th>
+<th>价格</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>吉他(G)</td>
+<td>1</td>
+<td>1500</td>
+</tr>
+<tr>
+<td>音响(S)</td>
+<td>4</td>
+<td>3000</td>
+</tr>
+<tr>
+<td>电脑(L)</td>
+<td>3</td>
+<td>2000</td>
+</tr>
+</tbody>
+</table>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">KnapsackProblemDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">KnapsackProblem</span><span class="w"> </span><span class="n">knapsackProblem</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">KnapsackProblem</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">knapsackProblem</span><span class="p">.</span><span class="na">knapsackProblem</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">KnapsackProblem</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">knapsackProblem</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 物品的重量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">w</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 物品的价值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1500</span><span class="p">,</span><span class="w"> </span><span class="n">3000</span><span class="p">,</span><span class="w"> </span><span class="n">2000</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 背包的容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 物品的个数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">val</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 物品规划表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">m</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将v[][] 第一列和第一行重置为0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">v</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">v</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理 生成物品价格表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">v</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">v</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 如果当前商品的重量 是否能写入当前表格中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">w</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">val</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">j</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">w</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理完后 v[][] 表中数值最大的就是最后的结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ints</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">v</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">ints</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">anInt</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">ints</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">anInt</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">max</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">anInt</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">max</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="kmp算法">KMP算法</h3>
+<blockquote>
+<p>KMP算法是一种改进的字符串匹配算法，由D.E.Knuth，J.H.Morris和V.R.Pratt提出的，因此人们称它为克努特—莫里斯—普拉特操作（简称KMP算法）。KMP算法的核心是利用匹配失败后的信息，尽量减少模式串与主串的匹配次数以达到快速匹配的目的。具体实现就是通过一个next()函数实现，函数本身包含了模式串的局部匹配信息。KMP算法的时间复杂度O(m+n)。</p>
+</blockquote>
+<ul>
+<li>
+<p>常规算法匹配字符串</p>
+<p><img alt="数据结构与算法-042" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-042.gif"></p>
+<p>从主串的起始位置（或指定位置）开始与模式串的第一个字符比较，若相等，则继续逐个比较后续字符；否则从主串的下一个字符再重新和模式串的字符比较。依次类推，直到模式串成功匹配，返回主串中第一次出现模式串字符的位置，或者模式串匹配不成功，这里约定返回-1。</p>
+</li>
+<li>
+<p>KMP算法匹配字符串</p>
+<p><img alt="数据结构与算法-043" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-043.gif"></p>
+<p>主要就是改进了暴力匹配中i回溯的操作，KMP算法中当一趟匹配过程中出现字符比较不等时，不直接回溯i，而是利用已经得到的“部分匹配”的结果将模式串向右移动（j-next[j-1]）的距离。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">KMPDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">KMP</span><span class="w"> </span><span class="n">kmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">KMP</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;BBC ABCDAB ABCDABCDABDE&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;ABCDABD&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">kmp</span><span class="p">.</span><span class="na">getMatchTab</span><span class="p">(</span><span class="n">str2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">next</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">kmp</span><span class="p">.</span><span class="na">kmpSearch</span><span class="p">(</span><span class="n">str1</span><span class="p">,</span><span class="w"> </span><span class="n">str2</span><span class="p">,</span><span class="w"> </span><span class="n">next</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">KMP</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取KMP 部分匹配表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="nf">getMatchTab</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">dest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">dest</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 部分匹配表第一个值始终为0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">result</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">result</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// KMP 核心（特点，公式）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">j</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">dest</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">dest</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">j</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">result</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">dest</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">dest</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">j</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">result</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">j</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * KMP查找算法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param str1 原字符串
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param str2 子字符串
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param next 部分匹配表
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 匹配到字符串的第一个索引位置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">kmpSearch</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">next</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">str1</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">j</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">str1</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">str2</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">j</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">str1</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str2</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">j</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">j</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">j</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str2</span><span class="p">.</span><span class="na">length</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="贪心算法">贪心算法</h3>
+<p>贪心算法又称贪婪算法，是指在对问题进行求解时，在每一步选择中都采取最好或者最优(即最有利)的选择，从而希望能够导致结果是最好或者最优的算法。贪婪算法所得到的结果不一定是最优的结果(有时候会是最优解)，但是都是相对近似(接近)最优解的结果。</p>
+<p>举例，假设存在下面需要付费的广播台，以及广播台信号可以覆盖的地区。 如何选择最少的广播台，让所有的地区都可以接收到信号。</p>
+<table>
+<thead>
+<tr>
+<th>广播台</th>
+<th>覆盖地区</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>K1</td>
+<td>“北京”, “上海”, “天津”</td>
+</tr>
+<tr>
+<td>K2</td>
+<td>“广州”, “北京”, “深圳”</td>
+</tr>
+<tr>
+<td>K3</td>
+<td>“成都”, “上海”, “杭州”</td>
+</tr>
+<tr>
+<td>K4</td>
+<td>“上海”, “天津”</td>
+</tr>
+<tr>
+<td>K5</td>
+<td>“杭州”, “大连”</td>
+</tr>
+</tbody>
+</table>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GreedyAlgorithmDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">broadcasts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;北京&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;上海&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;天津&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet2</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;广州&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet2</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;北京&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet2</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;深圳&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet3</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;成都&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet3</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;上海&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet3</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;杭州&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet4</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;上海&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet4</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;天津&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet5</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;杭州&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet5</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;大连&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K1&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K2&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K3&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K4&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K5&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// allAreas 存放所有的地区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allAreas</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Map</span><span class="p">.</span><span class="na">Entry</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">broadcast</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">entrySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">allAreas</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">broadcast</span><span class="p">.</span><span class="na">getValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">GreedyAlgorithm</span><span class="p">().</span><span class="na">getRadioByGreedyAlgorithm</span><span class="p">(</span><span class="n">allAreas</span><span class="p">,</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">GreedyAlgorithm</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getRadioByGreedyAlgorithm</span><span class="p">(</span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allAreas</span><span class="p">,</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存放选择的电台</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">selects</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存放每次选择最优的电台</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">maxKey</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 临时集合 从 broadcasts 中选出能覆盖的电台，即存放 allAreas 与 broadcasts 的交集</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">tmpSet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">allAreas</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 每次需要清空</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">maxKey</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">keySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpSet</span><span class="p">.</span><span class="na">clear</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpSet</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">broadcasts</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 计算覆盖的电台 并赋值给tmpSet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpSet</span><span class="p">.</span><span class="na">retainAll</span><span class="p">(</span><span class="n">allAreas</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 此处进行比较 体现贪心算法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmpSet</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">maxKey</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">tmpSet</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">maxKey</span><span class="p">).</span><span class="na">size</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">maxKey</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 每进行一次循环最后需要移除选中的maxKey对应的电台城市</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">maxKey</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">selects</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">maxKey</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">allAreas</span><span class="p">.</span><span class="na">removeAll</span><span class="p">(</span><span class="n">broadcasts</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">maxKey</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">selects</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="普里姆算法">普里姆算法</h3>
+<p>普里姆算法（Prim算法），图论中的一种算法，可在加权连通图里搜索<strong>最小生成树</strong>。意即由此算法搜索到的边子集所构成的树中，不但包括了连通图里的所有顶点，且其所有边的权值之和亦为最小。</p>
+<blockquote>
+<p>最小生成树：给定一个带权的无向连通图，如何选取一棵生成树，使树上所有边上权的总和为最小，这叫最小生成树。简称MST。
+求最小生成树的算法主要是普里姆算法和克鲁斯卡尔算法。</p>
+<ul>
+<li>普里姆算法：O(n^2),适合稠密图（边多的图）</li>
+<li>克鲁斯卡尔算法:O,适合稀疏图（边少的图）</li>
+</ul>
+</blockquote>
+<p>普利姆(Prim)算法求最小生成树，也就是在包含n个顶点的连通图中，找出只有(n-1)条边包含所有n个顶点的连通子图，也就是所谓的极小连通子图。</p>
+<p><img alt="数据结构与算法-044" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-044.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class PrimAlgorithmDemo {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        char[] data = new char[]{&#39;A&#39;, &#39;B&#39;, &#39;C&#39;, &#39;D&#39;, &#39;E&#39;, &#39;F&#39;, &#39;G&#39;};
+</span></span><span class="line"><span class="cl">        int vertex = data.length;
+</span></span><span class="line"><span class="cl">        //邻接矩阵的关系使用二维数组表示,10000这个大数，表示两个点不联通
+</span></span><span class="line"><span class="cl">        int[][] weight = new int[][]{
+</span></span><span class="line"><span class="cl">                {10000, 5, 7, 10000, 10000, 10000, 2},
+</span></span><span class="line"><span class="cl">                {5, 10000, 10000, 9, 10000, 10000, 3},
+</span></span><span class="line"><span class="cl">                {7, 10000, 10000, 10000, 8, 10000, 10000},
+</span></span><span class="line"><span class="cl">                {10000, 9, 10000, 10000, 10000, 4, 10000},
+</span></span><span class="line"><span class="cl">                {10000, 10000, 8, 10000, 10000, 5, 4},
+</span></span><span class="line"><span class="cl">                {10000, 10000, 10000, 4, 5, 10000, 6},
+</span></span><span class="line"><span class="cl">                {2, 3, 10000, 10000, 4, 6, 10000}
+</span></span><span class="line"><span class="cl">        };
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        MGraph graph = new MGraph(vertex);
+</span></span><span class="line"><span class="cl">        PrimAlgorithm minTree = new PrimAlgorithm();
+</span></span><span class="line"><span class="cl">        graph.create(graph, vertex, data, weight);
+</span></span><span class="line"><span class="cl">        graph.show(graph);
+</span></span><span class="line"><span class="cl">        minTree.prim(graph, 0);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">class PrimAlgorithm {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    /**
+</span></span><span class="line"><span class="cl">     * 最小生成树问题 prim算法
+</span></span><span class="line"><span class="cl">     *
+</span></span><span class="line"><span class="cl">     * @param graph  图对象
+</span></span><span class="line"><span class="cl">     * @param vertex 开始的顶点
+</span></span><span class="line"><span class="cl">     */
+</span></span><span class="line"><span class="cl">    public void prim(MGraph graph, int vertex) {
+</span></span><span class="line"><span class="cl">        int i = 0, j = 0;
+</span></span><span class="line"><span class="cl">        int row = -1, column = -1;
+</span></span><span class="line"><span class="cl">        // 存放已经访问过的顶点
+</span></span><span class="line"><span class="cl">        int[] visited = new int[graph.vertex];
+</span></span><span class="line"><span class="cl">        // 用1表示两点之间已经连接， 0表示未连接
+</span></span><span class="line"><span class="cl">        visited[vertex] = 1;
+</span></span><span class="line"><span class="cl">        int minWeight = 10000;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        for (int k = 1; k &lt; graph.vertex; k++){
+</span></span><span class="line"><span class="cl">            // 比较两点之间的权值，每次都获取最小的权值
+</span></span><span class="line"><span class="cl">            for (i = 0; i &lt; graph.vertex; i++) {
+</span></span><span class="line"><span class="cl">                for(j = 0; j &lt; graph.vertex; j++){
+</span></span><span class="line"><span class="cl">                    if (visited[i] == 1 &amp;&amp; visited[j] == 0 &amp;&amp; graph.weight[i][j] &lt; minWeight){
+</span></span><span class="line"><span class="cl">                        minWeight = graph.weight[i][j];
+</span></span><span class="line"><span class="cl">                        row = i;
+</span></span><span class="line"><span class="cl">                        column = j;
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;边&lt;&#34; + graph.data[row] + &#34;,&#34; + graph.data[column] + &#34;&gt; 权值:&#34; + minWeight);
+</span></span><span class="line"><span class="cl">            // 将顶点标记为已经访问过
+</span></span><span class="line"><span class="cl">            visited[column] = 1;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 每次比较完后需要将minWeight重置
+</span></span><span class="line"><span class="cl">            minWeight = 10000;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">class MGraph {
+</span></span><span class="line"><span class="cl">    int vertex;
+</span></span><span class="line"><span class="cl">    char[] data;
+</span></span><span class="line"><span class="cl">    int[][] weight;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public MGraph(int vertex) {
+</span></span><span class="line"><span class="cl">        this.vertex = vertex;
+</span></span><span class="line"><span class="cl">        data = new char[vertex];
+</span></span><span class="line"><span class="cl">        weight = new int[vertex][vertex];
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    /**
+</span></span><span class="line"><span class="cl">     * 创建图的邻接矩阵
+</span></span><span class="line"><span class="cl">     *
+</span></span><span class="line"><span class="cl">     * @param graph  图对象
+</span></span><span class="line"><span class="cl">     * @param vertex 图对应的顶点个数
+</span></span><span class="line"><span class="cl">     * @param data   图的各个顶点的值
+</span></span><span class="line"><span class="cl">     * @param weight 图的邻接矩阵
+</span></span><span class="line"><span class="cl">     */
+</span></span><span class="line"><span class="cl">    public void create(MGraph graph, int vertex, char[] data, int[][] weight) {
+</span></span><span class="line"><span class="cl">        int i, j;
+</span></span><span class="line"><span class="cl">        for (i = 0; i &lt; vertex; i++) {
+</span></span><span class="line"><span class="cl">            graph.data[i] = data[i];
+</span></span><span class="line"><span class="cl">            for (j = 0; j &lt; vertex; j++) {
+</span></span><span class="line"><span class="cl">                graph.weight[i][j] = weight[i][j];
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 显示图的邻接矩阵
+</span></span><span class="line"><span class="cl">    public void show(MGraph graph) {
+</span></span><span class="line"><span class="cl">        for (int[] link : graph.weight) {
+</span></span><span class="line"><span class="cl">            System.out.println(Arrays.toString(link));
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="克鲁斯卡尔算法">克鲁斯卡尔算法</h3>
+<p>克鲁斯卡尔算法是求连通网的最小生成树的另一种方法。基本思想是， 将所有边按照权值的大小进行升序排序，然后从小到大一一判断，条件为：如果这个边不会与之前选择的所有边组成回路，就可以作为最小生成树的一部分；反之，舍去。 直到具有 n 个顶点的连通网筛选出来 n-1（n为顶点个数） 条边为止。</p>
+<blockquote>
+<p>判断是否构成回路: 当每次需要将一条边添加到最小生成树时，判断该边的两个顶点终点是否相同，相同就会构成回路。</p>
+<p>关于终点的说明：就是将所有顶点按照从小到大的顺序排列好之后；某个顶点的终点就是与它连通的最大顶点。 就是将所有顶点按照从小到大的顺序排列好之后；某个顶点的终点就是与它连通的最大顶点。</p>
+<p>举例</p>
+<ul>
+<li>首先ABCDEFG这7个顶点，在顶点集合中是按照顺序存放的；</li>
+<li>第一次选择的是EF，毫无疑问这一条边的终点是F；</li>
+<li>第二次选择的CD的终点D；</li>
+<li>第三次选择的DE，终点是F，因为此时D和E相连，D又和F相连，所以D的终点是F。而且，因为C和D是相连的，D和E相连，E和F也是相连的，所以C的终点此时变成了F。也就是说，当选择了EF、CD、DE这三条边后，C、D、E的终点都是F。当然F的终点也是F，因为F还没和后面的哪个顶点连接。</li>
+<li>本来接下来应该选择CE的，但是由于C和E的终点都是F，所以就会形成回路；</li>
+</ul>
+</blockquote>
+<p><img alt="数据结构与算法-045" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-045.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">KruskalCaseDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//使用 INF 表示两个顶点不能连通</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">INF</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertexs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;D&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;E&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;F&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;G&#39;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">matrix</span><span class="o">[][]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*A*//*B*//*C*//*D*//*E*//*F*//*G*/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*A*/</span><span class="w"> </span><span class="p">{</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">12</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">16</span><span class="p">,</span><span class="w"> </span><span class="n">14</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*B*/</span><span class="w"> </span><span class="p">{</span><span class="n">12</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*C*/</span><span class="w"> </span><span class="p">{</span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*D*/</span><span class="w"> </span><span class="p">{</span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*E*/</span><span class="w"> </span><span class="p">{</span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*F*/</span><span class="w"> </span><span class="p">{</span><span class="n">16</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*G*/</span><span class="w"> </span><span class="p">{</span><span class="n">14</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">}};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">KruskalCase</span><span class="w"> </span><span class="n">kruskalCase</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">KruskalCase</span><span class="p">(</span><span class="n">vertexs</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">kruskalCase</span><span class="p">.</span><span class="na">print</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">kruskalCase</span><span class="p">.</span><span class="na">kruskal</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">KruskalCase</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//使用 INF 表示两个顶点不能连通</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">INF</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">edgeNum</span><span class="p">;</span><span class="w"> </span><span class="c1">//边的个数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertexs</span><span class="p">;</span><span class="w"> </span><span class="c1">//顶点数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="p">;</span><span class="w"> </span><span class="c1">//邻接矩阵</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构造器</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">KruskalCase</span><span class="p">(</span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertexs</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始化顶点数和边的个数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">vlen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始化顶点, 复制拷贝的方式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">vertexs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">char</span><span class="o">[</span><span class="n">vlen</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">vertexs</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertexs</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始化边, 使用的是复制拷贝的方式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">matrix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">vlen</span><span class="o">][</span><span class="n">vlen</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vlen</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vlen</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 统计边的条数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vlen</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vlen</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">INF</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">edgeNum</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">print</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;邻接矩阵为: \n&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%12d&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能：对边进行排序处理, 冒泡排序
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param edges 边的集合
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sortEdges</span><span class="p">(</span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="n">edges</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">edges</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">edges</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">.</span><span class="na">weight</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">EdgeData</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param ch 顶点的值，比如&#39;A&#39;,&#39;B&#39;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回ch顶点对应的下标，如果找不到，返回-1
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getPosition</span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">vertexs</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 找不到,返回-1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 获取图中边，放到EData[] 数组中，后面我们需要遍历该数组
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 是通过matrix 邻接矩阵来获取
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * EData[] 形式 [[&#39;A&#39;,&#39;B&#39;, 12], [&#39;B&#39;,&#39;F&#39;,7], .....]
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="nf">getEdges</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="n">edges</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EdgeData</span><span class="o">[</span><span class="n">edgeNum</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">INF</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">edges</span><span class="o">[</span><span class="n">index</span><span class="o">++]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EdgeData</span><span class="p">(</span><span class="n">vertexs</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">vertexs</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">edges</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 获取下标为i的顶点的终点, 用于后面判断两个顶点的终点是否相同
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param ends ： 数组就是记录了各个顶点对应的终点是哪个,ends 数组是在遍历过程中，逐步形成
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param i    : 表示传入的顶点对应的下标
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回的就是 下标为i的这个顶点对应的终点的下标, 一会回头还有来理解
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getEnd</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ends</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// i = 4 [0,0,0,0,5,0,0,0,0,0,0,0]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">ends</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ends</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">kruskal</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 用于保存&#34;已有最小生成树&#34; 中的每个顶点在最小生成树中的终点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ends</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建结果数组, 保存最后的最小生成树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="n">rets</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EdgeData</span><span class="o">[</span><span class="n">edgeNum</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取图中 所有的边的集合 ， 一共有12边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="n">edges</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getEdges</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 按照边的权值大小进行排序(从小到大)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sortEdges</span><span class="p">(</span><span class="n">edges</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历edges 数组，将边添加到最小生成树中时，判断是准备加入的边否形成了回路，如果没有，就加入 rets, 否则不能加入</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">edgeNum</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取到第i条边的第一个顶点(起点)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">point1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getPosition</span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">.</span><span class="na">start</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取到第i条边的第2个顶点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">point2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getPosition</span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">.</span><span class="na">end</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取p1这个顶点在已有最小生成树中的终点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">endPointOfPoint1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getEnd</span><span class="p">(</span><span class="n">ends</span><span class="p">,</span><span class="w"> </span><span class="n">point1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取p2这个顶点在已有最小生成树中的终点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">endPointOfPoint2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getEnd</span><span class="p">(</span><span class="n">ends</span><span class="p">,</span><span class="w"> </span><span class="n">point2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 克鲁斯卡尔核心点：判断是否构成回路</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">endPointOfPoint1</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">endPointOfPoint2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 假设没有构成回路</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将该边上终点上的值赋值给起点位置的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">ends</span><span class="o">[</span><span class="n">endPointOfPoint1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">endPointOfPoint2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将该边保存起来</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">rets</span><span class="o">[</span><span class="n">index</span><span class="o">++]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;最小生成树为&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">rets</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">EdgeData</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">char</span><span class="w"> </span><span class="n">start</span><span class="p">;</span><span class="w"> </span><span class="c1">// 边的一个点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">char</span><span class="w"> </span><span class="n">end</span><span class="p">;</span><span class="w"> </span><span class="c1">// 边的另外一个点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w"> </span><span class="c1">// 边的权值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">EdgeData</span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">start</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">end</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">end</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 重写toString, 便于输出边信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;EData [&lt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&gt;= &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">weight</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;]&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="迪杰斯特拉算法">迪杰斯特拉算法</h3>
+<p>迪杰斯特拉算法是典型最短路径算法，用于计算一个结点到其他结点的最短路径。迪杰斯特拉算法是基于贪心思想，从起始位置触发，每次寻找与起点位置距离且未访问过的顶点，以该顶点作为中间结点，更新从起点到其他顶点的距离，直到全部顶点都作为了中间结点，并完成了路径更新，算法结束。 它的主要特点是以起始点为中心向外层层扩展，即图的广度优先搜索思想，直到扩展到终点为止。</p>
+<p>视频讲解：<a href="https://www.bilibili.com/video/BV1uX4y137Hf">bilibili</a></p>
+<p><img alt="数据结构与算法-046" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-046.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DijkstraAlgorithmDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;D&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;E&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;F&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;G&#39;</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="o">][</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 表示不可以连接</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">65535</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">3</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">4</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">6</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Graph</span><span class="w"> </span><span class="n">graph</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Graph</span><span class="p">(</span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">graph</span><span class="p">.</span><span class="na">showGraph</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">graph</span><span class="p">.</span><span class="na">dsj</span><span class="p">(</span><span class="n">6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Graph</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">VisitedVertex</span><span class="w"> </span><span class="n">vv</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构造器</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Graph</span><span class="p">(</span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">matrix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">matrix</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 显示结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showDijkstra</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vv</span><span class="p">.</span><span class="na">showArrays</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 显示图</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showGraph</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">link</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">matrix</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">link</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%8d&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 迪杰斯特拉算法实现
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index 表示出发顶点对应的下标
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dsj</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vv</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">VisitedVertex</span><span class="p">(</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">update</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vv</span><span class="p">.</span><span class="na">showArrays</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vv</span><span class="p">.</span><span class="na">findNextStartPoint</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">update</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">vv</span><span class="p">.</span><span class="na">showArrays</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 更新index下标顶点到周围顶点的距离和周围顶点的前驱顶点,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 根据遍历我们的邻接矩阵的 matrix[index]行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// len 含义是 : 出发顶点到index顶点的距离 + 从index顶点到j顶点的距离的和</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vv</span><span class="p">.</span><span class="na">getDis</span><span class="p">(</span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">index</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果j顶点没有被访问过，并且 len 小于出发顶点到j顶点的距离，就需要更新</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">vv</span><span class="p">.</span><span class="na">isVisited</span><span class="p">(</span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vv</span><span class="p">.</span><span class="na">getDis</span><span class="p">(</span><span class="n">j</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">vv</span><span class="p">.</span><span class="na">updatePre</span><span class="p">(</span><span class="n">j</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">vv</span><span class="p">.</span><span class="na">updateDis</span><span class="p">(</span><span class="n">j</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">VisitedVertex</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">alreadyArr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">preVisited</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">dis</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param length :表示顶点的个数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index: 出发顶点对应的下标, 比如G顶点，下标就是6
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">VisitedVertex</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">alreadyArr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">preVisited</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dis</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始化 dis数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Arrays</span><span class="p">.</span><span class="na">fill</span><span class="p">(</span><span class="n">dis</span><span class="p">,</span><span class="w"> </span><span class="n">65535</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dis</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">alreadyArr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 判断index顶点是否被访问过
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 如果访问过，就返回true, 否则访问false
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isVisited</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alreadyArr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 更新出发顶点到index顶点的距离
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">updateDis</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dis</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 更新pre这个顶点的前驱顶点为index顶点
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">updatePre</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">pre</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">preVisited</span><span class="o">[</span><span class="n">pre</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能:返回出发顶点到index顶点的距离
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getDis</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 继续选择并返回新的访问顶点， 比如这里的G 完后，就是 A点作为新的访问顶点(注意不是出发顶点)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">findNextStartPoint</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">65535</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">alreadyArr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alreadyArr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">min</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 更新 index 顶点被访问过</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alreadyArr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//显示最后的结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showArrays</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;核心数组的值如下：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">alreadyArr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">dis</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">preVisited</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;D&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;E&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;F&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;G&#39;</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">dis</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">65535</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">vertex</span><span class="o">[</span><span class="n">count</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;(&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;) &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;N &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="弗洛伊德算法">弗洛伊德算法</h3>
+<p>弗洛伊德算法又称为插点法，是一种利用动态规划的思想寻找给定的加权图中多源点之间最短路径的算法，与迪杰斯特拉算法类似。</p>
+<blockquote>
+<p>迪杰斯特拉算法对比弗洛伊德算法：
+迪杰斯特拉算法通过选定的被访问顶点，求出从出发访问顶点到其他顶点的最短路径；弗洛伊德算法中每一个顶点都是出发访问点，所以需要将每一个顶点看做被访问顶点，求出从每一个顶点到其他顶点的最短路径。</p>
+<ul>
+<li>弗洛伊德算法计算图中各个顶点之间的最短路径</li>
+<li>迪杰斯特拉算法用于计算图中某一个顶点到其他顶点的最短路径</li>
+</ul>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FloydAlgorithmDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;D&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;E&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;F&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;G&#39;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="o">][</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">65535</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">3</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">4</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">6</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FloydGraph</span><span class="w"> </span><span class="n">graph</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FloydGraph</span><span class="p">(</span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">graph</span><span class="p">.</span><span class="na">floyd</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">graph</span><span class="p">.</span><span class="na">show</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">FloydGraph</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">pre</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">dis</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">FloydGraph</span><span class="p">(</span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">dis</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dis</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dis</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">pre</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">length</span><span class="o">][</span><span class="n">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Arrays</span><span class="p">.</span><span class="na">fill</span><span class="p">(</span><span class="n">pre</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">show</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">k</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 先将pre数组输出的一行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">vertex</span><span class="o">[</span><span class="n">pre</span><span class="o">[</span><span class="n">k</span><span class="o">][</span><span class="n">i</span><span class="o">]]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 输出dis数组的一行数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;(&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">vertex</span><span class="o">[</span><span class="n">k</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;到&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">vertex</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;的最短路径是&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">k</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;) &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">floyd</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">m</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">a</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">b</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">a</span><span class="o">][</span><span class="n">m</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">m</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">len</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">a</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">dis</span><span class="o">[</span><span class="n">a</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">pre</span><span class="o">[</span><span class="n">a</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pre</span><span class="o">[</span><span class="n">m</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="马踏棋盘算法">马踏棋盘算法</h3>
+<p>马踏棋盘算法也被称为骑士周游问题。将马随机放在国际象棋的8×8棋盘0～7的某个方格中，马按走棋规则(马走日字)进行移动。要求每个方格只进入一次，走遍棋盘上全部64个方格。</p>
+<p>马踏棋盘问题实际上是图的深度优先搜索(DFS)的应用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HouseChessBoardDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HouseChessBoard</span><span class="w"> </span><span class="n">houseChessBoard</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HouseChessBoard</span><span class="p">(</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">houseChessBoard</span><span class="p">.</span><span class="na">showChessBoard</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HouseChessBoard</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 表示棋盘的列
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 表示棋盘的行
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 创建一个数组，标记棋盘的各个位置是否被访问过，true表示已经访问过
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">visited</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 使用一个属性，标记是否棋盘的所有位置都被访问 如果为true,表示成功
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">finished</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">chessboard</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">HouseChessBoard</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">y</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">column</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">visited</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">x</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">y</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">chessboard</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">x</span><span class="o">][</span><span class="n">y</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">traversalChess</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">chessboard</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="o">-</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="o">-</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showChessBoard</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ints</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">chessboard</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">anInt</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">ints</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">anInt</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">traversalChess</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">chessboard</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">column</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">step</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">chessboard</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">step</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将当前位置标记为已经访问过</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">visited</span><span class="o">[</span><span class="n">row</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取当前位置的下一个可走通的位置的集合</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextPos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNext</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">column</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sort</span><span class="p">(</span><span class="n">nextPos</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">nextPos</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取当前可走通的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Point</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nextPos</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断当前该点是否被访问过,如果没有被访问过则继续向下访问</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">visited</span><span class="o">[</span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">traversalChess</span><span class="p">(</span><span class="n">chessboard</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="p">,</span><span class="w"> </span><span class="n">step</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 当遍历完可走的位置集合后，如果发现该路不通，则进行回溯，否则标记为完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">step</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">y</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="o">!</span><span class="n">finished</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">chessboard</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">visited</span><span class="o">[</span><span class="n">row</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">finished</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将可走通路根据回溯次数进行从小到大排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="w"> </span><span class="n">points</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">points</span><span class="p">.</span><span class="na">sort</span><span class="p">((</span><span class="n">o1</span><span class="p">,</span><span class="w"> </span><span class="n">o2</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">next1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNext</span><span class="p">(</span><span class="n">o1</span><span class="p">).</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">next2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNext</span><span class="p">(</span><span class="n">o2</span><span class="p">).</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">next1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">next2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取下一个可走的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getNext</span><span class="p">(</span><span class="n">Point</span><span class="w"> </span><span class="n">current</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="w"> </span><span class="n">ps</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Point</span><span class="w"> </span><span class="n">p1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 表示马儿可以走5这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走6这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走7这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走0这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走1这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">y</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走2这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">y</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走3这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">y</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走4这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">y</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ps</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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+            "tv_色": "61822c7e9aae5da76475e7892534545336b23a6f.png",
+            "tv_调侃": "4bc022533ef31544ca0d72c12c808cf4a1cce3e3.png",
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+    </a>
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+    <footer class="footer">
+    <div id="footer_powered_by" class="powered_by">
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+    
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+
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+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/blog-site/public/posts/detailed/distributed-id/index.html b/blog-site/public/posts/detailed/distributed-id/index.html
new file mode 100644
index 00000000..19f4f75d
--- /dev/null
+++ b/blog-site/public/posts/detailed/distributed-id/index.html
@@ -0,0 +1,560 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>分布式ID详解 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="分布式ID 在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。 但随着数据日渐增长，主从同步也扛不住了，" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
+    
+
+	
+
+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8fid">
+                    分布式ID
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a9%e7%94%a8%e6%95%b0%e6%8d%ae%e5%ba%93%e8%87%aa%e5%a2%9eid">
+                    利用数据库自增id
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a9%e7%94%a8redis%e8%87%aa%e5%a2%9e">
+                    利用Redis自增
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a9%e7%94%a8uuid%e4%bd%9c%e4%b8%ba%e4%b8%bb%e9%94%ae">
+                    利用UUID作为主键
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a9%e7%94%a8%e7%b3%bb%e7%bb%9f%e5%bd%93%e5%89%8d%e6%97%b6%e9%97%b4">
+                    利用系统当前时间
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9b%aa%e8%8a%b1%e7%ae%97%e6%b3%95">
+                    雪花算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
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+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
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+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
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+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                        <h2 id="post_single_title">分布式ID详解</h2>
+                        <span id="post_page_title_date" class="date">2023.03.13</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
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+                    <div class="post_content markdown"><h2 id="分布式id">分布式ID</h2>
+<p>在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。
+但随着数据日渐增长，主从同步也扛不住了，就需要对数据库进行分库分表。在分库之后， 数据遍布在不同服务器上的数据库，数据库的自增主键已经没办法满足生成的主键唯一了，这个时候就需要生成分布式 ID了。</p>
+<p>分布式ID一般都需要满足这些条件：</p>
+<ul>
+<li>全局唯一：必须保证ID是全局性唯一的，基本要求；</li>
+<li>高性能：高可用低延时，ID生成响应要块，否则反倒会成为业务瓶颈；</li>
+<li>高可用：100%的可用性是骗人的，但是也要无限接近于100%的可用性；</li>
+<li>趋势递增：如果要把 ID 存放在数据库的话，ID 的有序性可以提升数据库写入速度。并且，很多时候 ，我们还很有可能会直接通过 ID 来进行排序；</li>
+<li>安全：ID 中不包含敏感信息；</li>
+</ul>
+<p>常见分布式ID解决方案如下：</p>
+<h3 id="利用数据库自增id">利用数据库自增id</h3>
+<p>往一个库的一个表里插入一条没什么业务含义的数据，获取一个数据库自增的一个 id，拿到这个 id 之后再往对应的分库分表里去写入。缺点是高并发存在瓶颈；优点是简单方便；适用于并发不高，但是数据量太大导致的分库分表扩容，可能每秒最高并发最多就几百，那么就走单独的一个库和表生成自增主键即可。</p>
+<h3 id="利用redis自增">利用Redis自增</h3>
+<p>基于对数据库自增的改进，原理就是利用redis的incr命令实现ID的原子性自增。不依赖于数据库，灵活方便，且性能优于数据库，但是如果系统中没有Redis，还需要引入新的组件，会增加系统复杂度。</p>
+<h3 id="利用uuid作为主键">利用UUID作为主键</h3>
+<p>UUID一般不会作为主键使用，因为UUID 太长了、占用空间大，作为主键性能太差了，且UUID 不具有有序性，会导致 B+ 树索引在写的时候有过多的随机写操作，总之就是无序的性能开销大；适合于随机生成个什么文件名、编号之类的。</p>
+<h3 id="利用系统当前时间">利用系统当前时间</h3>
+<p>一般如果用这个方案，是将当前时间跟很多其他的业务字段拼接起来，作为一个 id，如果业务上你觉得可以接受，那么也是可以的。你可以将别的业务字段值跟当前时间拼接起来，组成一个全局唯一的编号。</p>
+<h3 id="雪花算法">雪花算法</h3>
+<p>算法思路是是把一个 64 位的 long 型的 id，1 个 bit 是不用的，用其中的 41 bits 作为毫秒数，用 10 bits 作为工作机器 id，12 bits 作为序列号。</p>
+<ul>
+<li>1 bit：不用，为啥呢？因为二进制里第一个 bit 为如果是 1，那么都是负数，但是我们生成的 id 都是正数，所以第一个 bit 统一都是 0；</li>
+<li>41 bits：表示的是时间戳，单位是毫秒。41 bits 可以表示的数字多达 2^41 - 1 ，也就是可以标识 2^41 - 1 个毫秒值，换算成年就是表示 69 年的时间；</li>
+<li>10 bits：记录工作机器 id，代表的是这个服务最多可以部署在 2^10 台机器上，也就是 1024 台机器。但是 10 bits 里 5 个 bits 代表机房 id，5 个 bits 代表机器 id。意思就是最多代表 2^5 个机房（32 个机房），每个机房里可以代表 2^5 个机器（32 台机器）；</li>
+<li>12 bits：这个是用来记录同一个毫秒内产生的不同 id，12 bits 可以代表的最大正整数是 2^12 - 1 = 4096 ，也就是说可以用这个 12 bits 代表的数字来区分同一个毫秒内的 4096 个不同的 id；</li>
+</ul>
+<p>雪花算法相对来说还是比较靠谱的，毫秒数在高位，自增序列在低位，整个ID都是趋势递增的。不依赖数据库等第三方系统，以服务的方式部署，稳定性更高，生成ID的性能也是非常高的，能达到百万计QPS。但是雪花算法强依赖时钟，如果机器上时钟回拨，会导致发号重复或者服务会处于不可用状态。</p>
+<p>为了规避雪花算法的缺点，一些国内的大厂做了改进，像美团的<a href="https://github.com/Meituan-Dianping/Leaf">Leaf</a>，百度的<a href="https://github.com/baidu/uid-generator">uid-generator</a>，都是基于雪花算法来实现的。</p>
+<p>所以你要真是搞分布式 id 生成，如果是高并发啥的，那么用这个应该性能比较好，一般每秒几万并发的场景，也足够用了。</p>
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diff --git a/blog-site/public/posts/detailed/distributed-lock/index.html b/blog-site/public/posts/detailed/distributed-lock/index.html
new file mode 100644
index 00000000..5bf1b650
--- /dev/null
+++ b/blog-site/public/posts/detailed/distributed-lock/index.html
@@ -0,0 +1,1027 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>分布式锁详解 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="概述 在代码里面我们常用ReetrantLock、synchronized保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。 类似这样： public" />
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+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%bf%b0">
+                    概述
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e4%ba%8eredis%e7%9a%84%e5%88%86%e5%b8%83%e5%bc%8f%e9%94%81">
+                    基于Redis的分布式锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e5%88%86%e5%b8%83%e5%bc%8f%e9%94%81%e6%bc%94%e8%bf%9b">
+                    Redis分布式锁演进
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%b8%80">
+                    方式一
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%ba%8c">
+                    方式二
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%b8%89">
+                    方式三
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e5%9b%9b">
+                    方式四
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%ba%94">
+                    方式五
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e5%85%ad">
+                    方式六
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%b8%83">
+                    方式七
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e4%ba%8ezookeeper%e7%9a%84%e5%88%86%e5%b8%83%e5%bc%8f%e9%94%81">
+                    基于Zookeeper的分布式锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
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+                    <a id="export_markdown" title="导出markdown" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                </a>
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+            </div>
+
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+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
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+        </div>
+    </div>
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+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">分布式锁详解</h2>
+                        <span id="post_page_title_date" class="date">2024.05.25</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概述">概述</h2>
+<p>在代码里面我们常用<code>ReetrantLock、synchronized</code>保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。</p>
+<p>类似这样：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MainTest {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    private static final  ReentrantLock lock = new ReentrantLock();
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        lock.lock();
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;hello world&#34;);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            lock.unlock();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>但是，当项目采用分布式部署方式之后，再使用<code>ReetrantLock、synchronized</code>就不能保证数据的准确性，可能会出现严重bug。
+<img alt="Redis详解-010" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-010.png"></p>
+<p>举个例子，当很多个请求过来的时候，会先经过<code>Nginx</code>,然后<code>Nginx</code>再根据算法分发请求，到哪些服务器的程序上。
+此时商品的库存为一件，有两个请求，到达不同服务器上的不同程序的相同代码，先后执行了查询SQL，查出来的数据是相同的，然后依次执行库存减一操作，此时库存会变成-1件。这就造成了超卖问题。</p>
+<h2 id="基于redis的分布式锁">基于Redis的分布式锁</h2>
+<p>针对超卖问题，我们可以使用Redis分布式锁来解决。</p>
+<h3 id="redis分布式锁演进">Redis分布式锁演进</h3>
+<h4 id="方式一">方式一</h4>
+<p>使用Redis，<code>setnx</code>：</p>
+<blockquote>
+<p>SETNX 是SET IF NOT EXISTS的简写.日常命令格式是SETNX key value，如果 key不存在，则SETNX成功返回1，如果这个key已经存在了，则返回0。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value);
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>需要注意的是<code>redisTemplate.delete()</code>方法要加在<code>finally</code>中是为了程序出现异常不释放锁。</p>
+<p>但是这种写法会有一个问题，如果Redis服务器宕机了，或Redis服务被其他人kill掉了，此时恰好没有执行<code>finally</code>中的代码，就会造成Redis中永远都会存在这把锁，不会释放。</p>
+<h4 id="方式二">方式二</h4>
+<p>针对上面Redis宕机的问题，我们可以对这个key加一个过期时间，来解决：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {   
+</span></span><span class="line"><span class="cl">            // 加锁
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value);
+</span></span><span class="line"><span class="cl">            // 设置过期时间，假设为10s
+</span></span><span class="line"><span class="cl">            redisTemplate.expire(REDIS_LOCK,10, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>上面的代码虽然解决了Redis宕机的问题，但是也带来了一个新的问题：设置过期时间和加锁并不再一行，即是非原子操作。</p>
+<p>举个例子，如果执行完<code>setnx</code>加锁，正要执行<code>expire</code>设置过期时间时，进程要重启维护了，那么这个锁就“长生不老”了，别的线程永远获取不到锁了。</p>
+<h4 id="方式三">方式三</h4>
+<p>针对上面加锁和设置过期时间的问题，我们可以使用Redis提供的一个方法，使其具备原子性：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value, 10, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>加过期时间释放锁的这种方式会带来另一个问题，某个线程加锁，然后执行业务代码，业务代码执行的时间超过了限定时间，此时Redis会释放锁，然后第二个请求就进来了，此时第一个线程业务代码执行完毕，执行释放锁步骤。这就造成误删除其他线程的锁。</p>
+<p>简单说就是，张冠李戴，当前线程删除了其他线程的锁。</p>
+<h4 id="方式四">方式四</h4>
+<p>针对方式三带来的问题，需要加一个判断，来避免误删除其他线程的锁：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value, 10, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            // 判断是否是当前线程，如果是当前线程则允许释放锁
+</span></span><span class="line"><span class="cl">            if (redisTemplate.opsForvalue().get(REDIS_LOCK).equalsIgnoreCase(value)){
+</span></span><span class="line"><span class="cl">                redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>实际上这种方式判断和删除的操作不是原子的，不是原子性的就会出现问题。即该锁没有保存持有者的唯一标识，可能被别的客户端解锁。</p>
+<h4 id="方式五">方式五</h4>
+<p>针对方式四的问题，Redis官网有推荐的解决方法，即，使用<a href="http://www.redis.cn/commands/set">Lua脚本</a>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">if redis.call(&#39;setnx&#39;,KEYS[1],ARGV[1]) == 1 then
+</span></span><span class="line"><span class="cl">   redis.call(&#39;expire&#39;,KEYS[1],ARGV[2])
+</span></span><span class="line"><span class="cl">else
+</span></span><span class="line"><span class="cl">   return 0
+</span></span><span class="line"><span class="cl">end;
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value, 10, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            // 伪代码
+</span></span><span class="line"><span class="cl">            JRedis = jedis = JRedisUtils.getJRedis();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            String lua_scripts =
+</span></span><span class="line"><span class="cl">                    &#34;if redis.call(&#39;setnx&#39;,KEYS[1],ARGV[1]) == 1 then\n&#34; +
+</span></span><span class="line"><span class="cl">                    &#34;   redis.call(&#39;expire&#39;,KEYS[1],ARGV[2])\n&#34; +
+</span></span><span class="line"><span class="cl">                    &#34;else\n&#34; +
+</span></span><span class="line"><span class="cl">                    &#34;   return 0\n&#34; +
+</span></span><span class="line"><span class="cl">                    &#34;end;&#34;;
+</span></span><span class="line"><span class="cl">            Object result = jedis.eval(lua_scripts, Collections.singletonList(REDIS_LOCK), Collections.singletonList(value))
+</span></span><span class="line"><span class="cl">            if (result.equals(&#34;1&#34;)) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;删除key成功&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">                    
+</span></span><span class="line"><span class="cl">            if (jedis != null) {
+</span></span><span class="line"><span class="cl">                jedis.close();
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (redisTemplate.opsForvalue().get(REDIS_LOCK).equalsIgnoreCase(value)){
+</span></span><span class="line"><span class="cl">                redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>除了用这中方式，也可以用Redis事务来处理方式四带来的问题。</p>
+<p>对于上面的解决方法，其实并没有真正的解决缓存续期的问题，还是会带来能存在锁过期释放，业务没执行完的问题。</p>
+<h4 id="方式六">方式六</h4>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.cnblogs.com/yunlongn/p/14609443.html">https://www.cnblogs.com/yunlongn/p/14609443.html</a></li>
+</ul>
+<p>针对缓存续期的问题，我们可以开一个守护线程，每隔一段时间检查锁是否还存在，存在则对锁的过期时间延长，防止锁过期提前释放。</p>
+<p><code>Redisson</code>框架解决了这个问题：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedissonClient redisson;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        RLock lock = redisson.getLock(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            lock.lock(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            lock.unlock();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p><code>Redisson</code>大致工作原理：只要线程一加锁成功，就会启动一个<code>watch dog</code>看门狗，它是一个后台线程，会每隔10秒检查一下，如果线程一还持有锁，那么就会不断的延长锁key的生存时间。
+因此，<code>Redisson</code>解决了锁过期释放，业务没执行完问题。</p>
+<p><img alt="Redis详解-011" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-011.png"></p>
+<p>看似完美的解决方案，但是在高并发下可能也会出现下面的异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Caused by: java.lang.IllegalMonitorStateException: attempt to unlock lock, not locked by current thread by node id: 32caba49-5799-491b-aa7b-47d789dbca93 thread-id: 1
+</span></span></code></pre></div><p>异常出现的原因，加锁和解锁的线程不是同一个。</p>
+<h4 id="方式七">方式七</h4>
+<p>针对上面的异常，需要判断当前线程是否持有锁，如果还持有，则释放，如果未持有，则说明已被释放:</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedissonClient redisson;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">         RLock lock = redisson.getLock(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            lock.lock(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            // 查询当前线程是否持有此锁
+</span></span><span class="line"><span class="cl">            if (lock.isLocked() &amp;&amp; lock.isHeldByCurrentThread()) {
+</span></span><span class="line"><span class="cl">                lock.unlock();
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>这样写，程序的健壮性会更好，代码会更加严谨。</p>
+<h2 id="基于zookeeper的分布式锁">基于Zookeeper的分布式锁</h2>
+<p>Redis 实现分布式锁性能较高，ZooKeeper 实现分布式锁可靠性更高。实际项目中，我们应该根据业务的具体需求来选择。</p>
+<p>ZooKeeper 分布式锁是基于 临时顺序节点 和 Watcher（事件监听器） 实现的。</p>
+<p>获取锁：</p>
+<ol>
+<li>首先我们要有一个持久节点/locks，客户端获取锁就是在locks下创建临时顺序节点。</li>
+<li>假设客户端 1 创建了/locks/lock1节点，创建成功之后，会判断 lock1是否是 /locks 下最小的子节点。</li>
+<li>如果 lock1是最小的子节点，则获取锁成功。否则，获取锁失败。</li>
+<li>如果获取锁失败，则说明有其他的客户端已经成功获取锁。客户端 1 并不会不停地循环去尝试加锁，而是在前一个节点比如/locks/lock0上注册一个事件监听器。
+这个监听器的作用是当前一个节点释放锁之后通知客户端 1（避免无效自旋），这样客户端 1 就加锁成功了。</li>
+</ol>
+<p>释放锁：</p>
+<ol>
+<li>成功获取锁的客户端在执行完业务流程之后，会将对应的子节点删除。</li>
+<li>成功获取锁的客户端在出现故障之后，对应的子节点由于是临时顺序节点，也会被自动删除，避免了锁无法被释放。</li>
+<li>我们前面说的事件监听器其实监听的就是这个子节点删除事件，子节点删除就意味着锁被释放。</li>
+</ol>
+<p>实际项目中，推荐使用 Curator 来实现 ZooKeeper 分布式锁。
+Curator 是 Netflix 公司开源的一套 ZooKeeper Java 客户端框架，相比于 ZooKeeper 自带的客户端 zookeeper 来说，Curator 的封装更加完善，各种 API 都可以比较方便地使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">CuratorFramework</span><span class="w"> </span><span class="n">client</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ZKUtils</span><span class="p">.</span><span class="na">getClient</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">client</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 分布式可重入排它锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">InterProcessLock</span><span class="w"> </span><span class="n">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InterProcessMutex</span><span class="p">(</span><span class="n">client</span><span class="p">,</span><span class="w"> </span><span class="n">lockPath1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 分布式不可重入排它锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">InterProcessLock</span><span class="w"> </span><span class="n">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InterProcessSemaphoreMutex</span><span class="p">(</span><span class="n">client</span><span class="p">,</span><span class="w"> </span><span class="n">lockPath2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 将多个锁作为一个整体</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">InterProcessMultiLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InterProcessMultiLock</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">lock</span><span class="p">.</span><span class="na">acquire</span><span class="p">(</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">SECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalStateException</span><span class="p">(</span><span class="s">&#34;不能获取多锁&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;已获取多锁&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;是否有第一个锁: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">lock1</span><span class="p">.</span><span class="na">isAcquiredInThisProcess</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;是否有第二个锁: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">lock2</span><span class="p">.</span><span class="na">isAcquiredInThisProcess</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 资源操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">resource</span><span class="p">.</span><span class="na">use</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;释放多个锁&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">lock</span><span class="p">.</span><span class="na">release</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;是否有第一个锁: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">lock1</span><span class="p">.</span><span class="na">isAcquiredInThisProcess</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;是否有第二个锁: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">lock2</span><span class="p">.</span><span class="na">isAcquiredInThisProcess</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">client</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>如果对性能要求比较高的话，建议使用 Redis 实现分布式锁（优先选择 Redisson 提供的现成的分布式锁，而不是自己实现）。
+如果对可靠性要求比较高的话，建议使用 ZooKeeper 实现分布式锁（推荐基于 Curator 框架实现）。不过，现在很多项目都不会用到 ZooKeeper，如果单纯是因为分布式锁而引入 ZooKeeper 的话，那是不太可取的，不建议这样做，为了一个小小的功能增加了系统的复杂度。</p>
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diff --git a/blog-site/public/posts/detailed/elasticsearch/index.html b/blog-site/public/posts/detailed/elasticsearch/index.html
new file mode 100644
index 00000000..575e3d28
--- /dev/null
+++ b/blog-site/public/posts/detailed/elasticsearch/index.html
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+    <meta name="viewport" content="width=device-width, initial-scale=1" />
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+	<title>Elasticsearch详解 ｜ 脚踏实地</title>
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+    <meta name="description" content="概览 Elasticsearch，简称为 ES， ES是一个开源的高扩展的分布式全文搜索引擎， 是整个 ElasticStack 技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可" />
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+                </a>
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+                <a class="nav-link text-left" href="#%e9%9b%86%e7%be%a4%e6%9e%b6%e6%9e%84">
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+                <a class="nav-link text-left" href="#%e6%90%ad%e5%bb%ba%e9%9b%86%e7%be%a4">
+                    搭建集群
+                </a>
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+                <a class="nav-link text-left" href="#%e6%95%85%e9%9a%9c%e8%bd%ac%e7%a7%bb">
+                    故障转移
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+                <a class="nav-link text-left" href="#%e5%86%99%e6%95%b0%e6%8d%ae%e6%b5%81%e7%a8%8b">
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+                <a class="nav-link text-left" href="#%e8%af%bb%e6%95%b0%e6%8d%ae%e6%b5%81%e7%a8%8b">
+                    读数据流程
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+            
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+                <a class="nav-link text-left" href="#%e6%90%9c%e7%b4%a2%e6%95%b0%e6%8d%ae%e8%bf%87%e7%a8%8b">
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+                <a class="nav-link text-left" href="#%e6%9b%b4%e6%96%b0%e6%b5%81%e7%a8%8b">
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8e%9f%e7%90%86">
+                    原理
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%80%92%e6%8e%92%e7%b4%a2%e5%bc%95">
+                    倒排索引
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+                <a class="nav-link text-left" href="#%e5%88%86%e6%9e%90%e5%99%a8">
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+                <a class="nav-link text-left" href="#%e6%96%87%e6%a1%a3%e6%90%9c%e7%b4%a2">
+                    文档搜索
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+            
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+        
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+            
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+                <a class="nav-link text-left" href="#%e8%bf%91%e5%ae%9e%e6%97%b6%e6%90%9c%e7%b4%a2">
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+        
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+        
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+            
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bc%98%e5%8c%96">
+                    优化
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+            </li>
+            
+            
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+        
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+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
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+            
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+                <a class="nav-link text-left" href="#%e5%90%88%e7%90%86%e8%ae%be%e7%bd%ae%e5%88%86%e7%89%87%e6%95%b0">
+                    合理设置分片数
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+            
+            
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+        
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+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%87%e4%bb%b6%e7%bc%93%e5%86%b2%e5%8c%bahttpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance">
+                    文件缓冲区
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e6%8d%ae%e9%a2%84%e7%83%adhttpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance">
+                    数据预热
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%b7%e7%83%ad%e5%88%86%e7%a6%bbhttpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance">
+                    冷热分离
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+            
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#document%e6%a8%a1%e5%9e%8b%e8%ae%be%e8%ae%a1httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance">
+                    document模型设计
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+            
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+        </ul>
+        
+        </ul>
+        
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+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
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+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
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+                        <svg t="1689071509720" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="4564" width="16" height="16"><path d="M909.132886 0.037506h-184.960611a33.909445 33.909445 0 0 0-32.368107 33.909445 33.909445 33.909445 0 0 0 33.909445 33.395666h158.244078l-200.373995 199.346437a33.395666 33.395666 0 0 0 0 47.781491 31.854327 31.854327 0 0 0 23.633856 9.76181 33.909445 33.909445 0 0 0 24.147635-9.76181l198.832657-199.346437V272.340628a33.909445 33.909445 0 0 0 69.874009 0V88.921355A88.37007 88.37007 0 0 0 909.132886 0.037506zM216.558153 347.866211a107.37991 107.37991 0 1 0 107.37991-107.379911 107.89369 107.89369 0 0 0-107.37991 107.379911z m154.133843 0a51.377948 51.377948 0 0 1-97.618101 0 51.377948 51.377948 0 1 1 97.618101 0z" p-id="4565" fill="#424242"></path><path d="M963.079731 437.777619a34.423225 34.423225 0 0 0-33.909446 33.909445v265.110209a1811.07265 1811.07265 0 0 0-137.692899-193.181082 106.352351 106.352351 0 0 0-78.60826-36.478343 123.820854 123.820854 0 0 0-82.204716 35.964563l-3.596456 3.082677-188.557068 176.74014c-11.816928-13.358266-47.781491-51.377948-82.204716-87.856291a83.232275 83.232275 0 0 0-85.801172-21.578738 105.324792 105.324792 0 0 0-38.019681 19.52362l-141.289356 121.765736V89.948914a22.092517 22.092517 0 0 1 22.606297-22.606297h417.702713a33.395666 33.395666 0 0 0 33.395666-33.909445 33.395666 33.395666 0 0 0-33.395666-33.395666H113.802258A89.911408 89.911408 0 0 0 23.89085 89.948914v844.139678a89.911408 89.911408 0 0 0 89.911408 89.911408h793.27551a89.911408 89.911408 0 0 0 89.397629-89.911408v-462.401528a33.909445 33.909445 0 0 0-33.395666-33.909445z m-33.909446 496.310973a22.606297 22.606297 0 0 1-22.092517 22.606297H113.802258a22.606297 22.606297 0 0 1-22.606297-22.606297v-88.37007l183.933052-160.812976a43.157476 43.157476 0 0 1 15.413385-7.192912 15.927164 15.927164 0 0 1 17.982281 5.137794c37.505902 36.478343 78.60826 83.232275 82.718496 87.856291a61.653537 61.653537 0 0 0 42.643696 22.092517 62.681096 62.681096 0 0 0 51.377948-20.037399c8.220472-8.220472 134.610223-125.875971 194.208641-181.877935a57.029522 57.029522 0 0 1 34.423225-16.440943 45.212594 45.212594 0 0 1 29.79921 15.927164 2954.231982 2954.231982 0 0 1 186.501949 256.889738z" p-id="4566" fill="#424242"></path></svg>
+                    </a>
+                    <a id="export_markdown" title="导出markdown" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_doc" title="导出文档" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1689246982401" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="6825" width="16" height="16"><path d="M270.76864 608.32h180.8a31.68 31.68 0 0 0 0-62.976H270.76864a31.68 31.68 0 0 0 0 62.976zM271.34464 458.56h457.92a33.472 33.472 0 0 0 31.552-34.752 33.28 33.28 0 0 0-31.552-34.624H271.34464a34.816 34.816 0 0 0 0 69.376zM271.34464 293.504h457.92a33.344 33.344 0 0 0 31.552-34.688 33.216 33.216 0 0 0-31.552-34.624H271.34464a33.28 33.28 0 0 0-31.616 34.624 33.28 33.28 0 0 0 31.616 34.688z" p-id="6826" fill="#424242"></path><path d="M869.87264 0H153.77664A70.4 70.4 0 0 0 84.65664 70.912V953.6A69.952 69.952 0 0 0 153.77664 1024h370.048a32 32 0 0 0 0-63.68H147.12064V64h729.6v468.672a31.296 31.296 0 1 0 62.528 0V70.912A70.4 70.4 0 0 0 869.87264 0z" p-id="6827" fill="#424242"></path><path d="M482.16064 730.624h337.664L715.82464 625.216a28.864 28.864 0 0 1-7.936-28.736 29.184 29.184 0 0 1 20.608-21.184 29.632 29.632 0 0 1 29.12 8.128l174.784 177.216-174.784 176.96a29.184 29.184 0 0 1-49.728-13.312 29.248 29.248 0 0 1 8-28.8l103.936-105.344H482.16064a29.696 29.696 0 0 1-29.504-29.76 29.632 29.632 0 0 1 29.504-29.76z" p-id="6828" fill="#424242"></path></svg>
+                    </a>
+                </span>
+                <a  id="icon_more" title="更多" >
+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
+                </a>
+                <a  id="icon_less" class="display_none">
+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Elasticsearch详解</h2>
+                        <span id="post_page_title_date" class="date">2023.02.14</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>Elasticsearch，简称为 ES， ES是一个开源的高扩展的分布式全文搜索引擎， 是整个 ElasticStack 技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可以扩展到上百台服务器，处理 PB 级别的数据。</p>
+<blockquote>
+<p>Elastic Stack, 包括 Elasticsearch、 Kibana、 Beats 和 Logstash（也称为 ELK Stack）。能够安全可靠地获取任何来源、任何格式的数据，然后实时地对数据进行搜索、分析和可视化。</p>
+</blockquote>
+<p>Elasticsearch 是面向文档型数据库，一条数据在这里就是一个文档。 Elasticsearch 里存储文档数据和关系型数据库 MySQL 存储数据的概念进行一个类比,如图:
+<img alt="Elasticsearch详解-01" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-01.png"></p>
+<p>ES 里的 Index 可以看做一个库，而 Types 相当于表， Documents 则相当于表的行。这里 Types 的概念已经被逐渐弱化， Elasticsearch 6.X 中，一个 index 下已经只能包含一个type， Elasticsearch 7.X 中, Type 的概念已经被删除了。</p>
+<p>官网下载地址: <a href="https://www.elastic.co/cn/downloads/past-releases">https://www.elastic.co/cn/downloads/past-releases</a></p>
+<h2 id="使用">使用</h2>
+<h3 id="与es交互">与ES交互</h3>
+<h4 id="索引创建">索引创建</h4>
+<p>发送put请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname
+</span></span></span></code></pre></div><h4 id="索引查询">索引查询</h4>
+<p>发送get请求,查询单条</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname
+</span></span></span></code></pre></div><p>查询所有索引,发送get请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_cat/indices
+</span></span></span></code></pre></div><h4 id="索引删除">索引删除</h4>
+<p>发送delete请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname
+</span></span></span></code></pre></div><h4 id="文档创建修改">文档创建修改</h4>
+<p>发送post请求,第一次为创建,再一次发送为修改</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_docname/idstr
+</span></span></span></code></pre></div><p>请求参数</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-json" data-lang="json"><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;title&#34;</span><span class="p">:</span><span class="s2">&#34;华为手机&#34;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;category&#34;</span><span class="p">:</span><span class="s2">&#34;小米&#34;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;images&#34;</span><span class="p">:</span><span class="s2">&#34;http://www.gulixueyuan.com/xm.jpg&#34;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;price&#34;</span><span class="p">:</span><span class="mf">3999.00</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h4 id="文档局部修改">文档局部修改</h4>
+<p>发送post请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_update/idstr
+</span></span></span></code></pre></div><p>请求参数</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-json" data-lang="json"><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;doc&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;title&#34;</span><span class="p">:</span><span class="s2">&#34;小米手机&#34;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;category&#34;</span><span class="p">:</span><span class="s2">&#34;小米&#34;</span>
+</span></span><span class="line"><span class="cl">  <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h4 id="文档查询">文档查询</h4>
+<p>发送get请求,查询单条</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_docname/idstr
+</span></span></span></code></pre></div><h4 id="文档删除">文档删除</h4>
+<p>发送delete请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_docname/idstr
+</span></span></span></code></pre></div><h4 id="全查询">全查询</h4>
+<p>发送get请求,能看到全部数据</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_search
+</span></span></span></code></pre></div><p>url带参查询,发get请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_search?q=category:小米
+</span></span></span></code></pre></div><p>请求体带参查询,发送get请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_search
+</span></span></span></code></pre></div><p>查询category是华为和小米的,price大于2000,只显示title,显示第一页,每页显示两个,根据price降序</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-json" data-lang="json"><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;query&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;bool&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="nt">&#34;should&#34;</span><span class="p">:</span> <span class="p">[{</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&#34;match&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">          <span class="nt">&#34;category&#34;</span><span class="p">:</span> <span class="s2">&#34;小米&#34;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">      <span class="p">},</span>
+</span></span><span class="line"><span class="cl">        <span class="p">{</span>
+</span></span><span class="line"><span class="cl">          <span class="nt">&#34;match&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&#34;category&#34;</span><span class="p">:</span> <span class="s2">&#34;华为&#34;</span>
+</span></span><span class="line"><span class="cl">          <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}]</span>
+</span></span><span class="line"><span class="cl">    <span class="p">},</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;filter&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="nt">&#34;range&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&#34;price&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">          <span class="nt">&#34;gt&#34;</span><span class="p">:</span> <span class="mi">2000</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">      <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">  <span class="p">},</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;_source&#34;</span><span class="p">:</span> <span class="p">[</span><span class="s2">&#34;title&#34;</span><span class="p">],</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;from&#34;</span><span class="p">:</span> <span class="mi">0</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;size&#34;</span><span class="p">:</span> <span class="mi">2</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;sort&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;price&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="nt">&#34;order&#34;</span><span class="p">:</span> <span class="s2">&#34;desc&#34;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">  <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h3 id="整合springboot">整合SpringBoot</h3>
+<h4 id="pom依赖">pom依赖</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-xml" data-lang="xml"><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.elasticsearch.client<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>elasticsearch-rest-high-level-client<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>7.5.2<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.elasticsearch.client<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>elasticsearch-rest-client<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>7.5.2<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.elasticsearch<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>elasticsearch<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>7.5.2<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;exclusions&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;exclusion&gt;</span>
+</span></span><span class="line"><span class="cl">                <span class="nt">&lt;groupId&gt;</span>org.elasticsearch.client<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">                <span class="nt">&lt;artifactId&gt;</span>elasticsearch-rest-client<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;/exclusion&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;exclusion&gt;</span>
+</span></span><span class="line"><span class="cl">                <span class="nt">&lt;groupId&gt;</span>org.elasticsearch<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">                <span class="nt">&lt;artifactId&gt;</span>elasticsearch<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;/exclusion&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/exclusions&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span></code></pre></div><h4 id="applicationyml">application.yml</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="nt">demo</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">data</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">elasticsearch</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="nt">cluster-name</span><span class="p">:</span><span class="w"> </span><span class="l">elasticsearch</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="nt">cluster-nodes</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="m">127.0.0.1</span><span class="p">:</span><span class="m">1001</span><span class="p">,</span><span class="m">127.0.0.1</span><span class="p">:</span><span class="m">1002</span><span class="p">,</span><span class="m">127.0.0.1</span><span class="p">:</span><span class="m">1003</span><span class="p">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="nt">index</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nt">number-of-replicas</span><span class="p">:</span><span class="w"> </span><span class="m">0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nt">number-of-shards</span><span class="p">:</span><span class="w"> </span><span class="m">3</span><span class="w">
+</span></span></span></code></pre></div><h4 id="elasticsearchautoconfiguration">ElasticsearchAutoConfiguration</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * ElasticsearchAutoConfiguration
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 22:59
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="p">(</span><span class="n">onConstructor_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nd">@Autowired</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@EnableConfigurationProperties</span><span class="p">(</span><span class="n">ElasticsearchProperties</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ElasticsearchAutoConfiguration</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ElasticsearchProperties</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">HttpHost</span><span class="o">&gt;</span><span class="w"> </span><span class="n">httpHosts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@ConditionalOnMissingBean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">RestHighLevelClient</span><span class="w"> </span><span class="nf">restHighLevelClient</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">clusterNodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getClusterNodes</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">clusterNodes</span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">parts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StringUtils</span><span class="p">.</span><span class="na">split</span><span class="p">(</span><span class="n">node</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Assert</span><span class="p">.</span><span class="na">notNull</span><span class="p">(</span><span class="n">parts</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Must defined&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Assert</span><span class="p">.</span><span class="na">state</span><span class="p">(</span><span class="n">parts</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Must be defined as &#39;host:port&#39;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">httpHosts</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HttpHost</span><span class="p">(</span><span class="n">parts</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">parseInt</span><span class="p">(</span><span class="n">parts</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="p">),</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getSchema</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalStateException</span><span class="p">(</span><span class="s">&#34;Invalid ES nodes &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;property &#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&#39;&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RestClientBuilder</span><span class="w"> </span><span class="n">builder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestClient</span><span class="p">.</span><span class="na">builder</span><span class="p">(</span><span class="n">httpHosts</span><span class="p">.</span><span class="na">toArray</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HttpHost</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">getRestHighLevelClient</span><span class="p">(</span><span class="n">builder</span><span class="p">,</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * get restHistLevelClient
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param builder                 RestClientBuilder
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param elasticsearchProperties elasticsearch default properties
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@link org.elasticsearch.client.RestHighLevelClient}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">RestHighLevelClient</span><span class="w"> </span><span class="nf">getRestHighLevelClient</span><span class="p">(</span><span class="n">RestClientBuilder</span><span class="w"> </span><span class="n">builder</span><span class="p">,</span><span class="w"> </span><span class="n">ElasticsearchProperties</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Callback used the default {@link RequestConfig} being set to the {@link CloseableHttpClient}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">setRequestConfigCallback</span><span class="p">(</span><span class="n">requestConfigBuilder</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">requestConfigBuilder</span><span class="p">.</span><span class="na">setConnectTimeout</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getConnectTimeout</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">requestConfigBuilder</span><span class="p">.</span><span class="na">setSocketTimeout</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getSocketTimeout</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">requestConfigBuilder</span><span class="p">.</span><span class="na">setConnectionRequestTimeout</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getConnectionRequestTimeout</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">requestConfigBuilder</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Callback used to customize the {@link CloseableHttpClient} instance used by a {@link RestClient} instance.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">setHttpClientConfigCallback</span><span class="p">(</span><span class="n">httpClientBuilder</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">httpClientBuilder</span><span class="p">.</span><span class="na">setMaxConnTotal</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getMaxConnectTotal</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">httpClientBuilder</span><span class="p">.</span><span class="na">setMaxConnPerRoute</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getMaxConnectPerRoute</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">httpClientBuilder</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Callback used the basic credential auth</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ElasticsearchProperties</span><span class="p">.</span><span class="na">Account</span><span class="w"> </span><span class="n">account</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getAccount</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">(</span><span class="n">account</span><span class="p">.</span><span class="na">getUsername</span><span class="p">())</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="o">!</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">(</span><span class="n">account</span><span class="p">.</span><span class="na">getUsername</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">final</span><span class="w"> </span><span class="n">CredentialsProvider</span><span class="w"> </span><span class="n">credentialsProvider</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BasicCredentialsProvider</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">credentialsProvider</span><span class="p">.</span><span class="na">setCredentials</span><span class="p">(</span><span class="n">AuthScope</span><span class="p">.</span><span class="na">ANY</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">UsernamePasswordCredentials</span><span class="p">(</span><span class="n">account</span><span class="p">.</span><span class="na">getUsername</span><span class="p">(),</span><span class="w"> </span><span class="n">account</span><span class="p">.</span><span class="na">getPassword</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RestHighLevelClient</span><span class="p">(</span><span class="n">builder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="elasticsearchproperties">ElasticsearchProperties</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * ElasticsearchProperties
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 22:58
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Builder</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@NoArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@ConfigurationProperties</span><span class="p">(</span><span class="n">prefix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;demo.data.elasticsearch&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ElasticsearchProperties</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 请求协议
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">schema</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;http&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 集群名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">clusterName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;elasticsearch&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 集群节点
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@NotNull</span><span class="p">(</span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;集群节点不允许为空&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">clusterNodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 连接超时时间(毫秒)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">connectTimeout</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * socket 超时时间
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">socketTimeout</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">30000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 连接请求超时时间
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">connectionRequestTimeout</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">500</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 每个路由的最大连接数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">maxConnectPerRoute</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 最大连接总数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">maxConnectTotal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">30</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 索引配置信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Index</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Index</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 认证账户
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Account</span><span class="w"> </span><span class="n">account</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Account</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 索引配置信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Index</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 分片数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">numberOfShards</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 副本数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">numberOfReplicas</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 认证账户
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Account</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 认证用户
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 认证密码
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">password</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="elasticsearchconstant">ElasticsearchConstant</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * ElasticsearchConstant
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 23:03
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">ElasticsearchConstant</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 索引名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">INDEX_NAME</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;person&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文档名称(字段名称)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_1&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_2&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_3&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_4&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_5&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 高亮标签
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">TAG_HIGH_LIGHT_START</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;&lt;label style=&#39;color:red&#39;&gt;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">TAG_HIGH_LIGHT_END</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;&lt;/label&gt;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="person">Person</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Person
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 23:04
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Builder</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@NoArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Person</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">serialVersionUID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">8510634155374943623L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 主键
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 名字
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 国家
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">country</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 年龄
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 生日
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="n">birthday</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 介绍
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">remark</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="searchpagehelper">SearchPageHelper</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @author: whitepure
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @date: 2023/1/6 11:25
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @description: SearchPageHelper
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SearchPageHelper</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">current</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">pageSize</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">total</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">records</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="personservice">PersonService</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * PersonService
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 23:07
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PersonService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * create Index
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">createIndex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * delete Index
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteIndex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * insert document source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param list  data source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">insert</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * update document source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param list  data source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * delete document source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param person delete data source and allow null object
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">delete</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="nd">@Nullable</span><span class="w"> </span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * search all doc records
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return person list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">searchList</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 分页查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param searchRequest search condition
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return search list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SearchPageHelper</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">searchPage</span><span class="p">(</span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="baseelasticsearchservice">BaseElasticsearchService</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * BaseElasticsearchService
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version 1.0v
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-16 15:44
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BaseElasticsearchService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Resource</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">RestHighLevelClient</span><span class="w"> </span><span class="n">client</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Resource</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ElasticsearchProperties</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">RequestOptions</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RequestOptions</span><span class="p">.</span><span class="na">Builder</span><span class="w"> </span><span class="n">builder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RequestOptions</span><span class="p">.</span><span class="na">DEFAULT</span><span class="p">.</span><span class="na">toBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 默认缓冲限制为100MB，此处修改为30MB。</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">setHttpAsyncResponseConsumerFactory</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HttpAsyncResponseConsumerFactory</span><span class="p">.</span><span class="na">HeapBufferedResponseConsumerFactory</span><span class="p">(</span><span class="n">30</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1024</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1024</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">COMMON_OPTIONS</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">builder</span><span class="p">.</span><span class="na">build</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * create elasticsearch index (asyc)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">createIndexRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">CreateIndexRequest</span><span class="w"> </span><span class="n">request</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CreateIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// Settings for this index</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">request</span><span class="p">.</span><span class="na">settings</span><span class="p">(</span><span class="n">Settings</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;index.number_of_shards&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getIndex</span><span class="p">().</span><span class="na">getNumberOfShards</span><span class="p">()).</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;index.number_of_replicas&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getIndex</span><span class="p">().</span><span class="na">getNumberOfReplicas</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">CreateIndexResponse</span><span class="w"> </span><span class="n">createIndexResponse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">client</span><span class="p">.</span><span class="na">indices</span><span class="p">().</span><span class="na">create</span><span class="p">(</span><span class="n">request</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34; whether all of the nodes have acknowledged the request : {}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">createIndexResponse</span><span class="p">.</span><span class="na">isAcknowledged</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34; Indicates whether the requisite number of shard copies were started for each shard in the index before timing out :{}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">createIndexResponse</span><span class="p">.</span><span class="na">isShardsAcknowledged</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;创建索引 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 失败&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * delete elasticsearch index
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteIndexRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DeleteIndexRequest</span><span class="w"> </span><span class="n">deleteIndexRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildDeleteIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">client</span><span class="p">.</span><span class="na">indices</span><span class="p">().</span><span class="na">delete</span><span class="p">(</span><span class="n">deleteIndexRequest</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;删除索引 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 失败&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * build DeleteIndexRequest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">DeleteIndexRequest</span><span class="w"> </span><span class="nf">buildDeleteIndexRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DeleteIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * build IndexRequest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index  elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param id     request object id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param object request object
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@link org.elasticsearch.action.index.IndexRequest}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">IndexRequest</span><span class="w"> </span><span class="nf">buildIndexRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">object</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">id</span><span class="p">).</span><span class="na">source</span><span class="p">(</span><span class="n">BeanUtil</span><span class="p">.</span><span class="na">beanToMap</span><span class="p">(</span><span class="n">object</span><span class="p">),</span><span class="w"> </span><span class="n">XContentType</span><span class="p">.</span><span class="na">JSON</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * exec updateRequest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index  elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param id     Document id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param object request object
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">updateRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">object</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">UpdateRequest</span><span class="w"> </span><span class="n">updateRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">UpdateRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">id</span><span class="p">).</span><span class="na">doc</span><span class="p">(</span><span class="n">BeanUtil</span><span class="p">.</span><span class="na">beanToMap</span><span class="p">(</span><span class="n">object</span><span class="p">),</span><span class="w"> </span><span class="n">XContentType</span><span class="p">.</span><span class="na">JSON</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">client</span><span class="p">.</span><span class="na">update</span><span class="p">(</span><span class="n">updateRequest</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;更新索引 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 数据 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">object</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 失败&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * exec deleteRequest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param id    Document id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">DeleteRequest</span><span class="w"> </span><span class="n">deleteRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DeleteRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">client</span><span class="p">.</span><span class="na">delete</span><span class="p">(</span><span class="n">deleteRequest</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;删除索引 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 数据id {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 失败&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 查询全部
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param indices elasticsearch 索引名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@link SearchResponse}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">SearchResponse</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="n">String</span><span class="p">...</span><span class="w"> </span><span class="n">indices</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SearchRequest</span><span class="p">(</span><span class="n">indices</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchSourceBuilder</span><span class="w"> </span><span class="n">searchSourceBuilder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SearchSourceBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">searchSourceBuilder</span><span class="p">.</span><span class="na">query</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">matchAllQuery</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">searchRequest</span><span class="p">.</span><span class="na">source</span><span class="p">(</span><span class="n">searchSourceBuilder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 查询全部
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param searchRequest 查询条件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@link SearchResponse}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">SearchResponse</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchResponse</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">searchResponse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">client</span><span class="p">.</span><span class="na">search</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">org</span><span class="p">.</span><span class="na">elasticsearch</span><span class="p">.</span><span class="na">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;查询索引 %s 失败&#34;</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">,</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">stream</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">.</span><span class="na">indices</span><span class="p">()).</span><span class="na">toArray</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="personserviceimpl">PersonServiceImpl</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * PersonServiceImpl
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 23:08
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PersonServiceImpl</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">BaseElasticsearchService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PersonService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">createIndex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">createIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteIndex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">deleteIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">insert</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">IndexRequest</span><span class="w"> </span><span class="n">request</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">person</span><span class="p">.</span><span class="na">getId</span><span class="p">()),</span><span class="w"> </span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">client</span><span class="p">.</span><span class="na">index</span><span class="p">(</span><span class="n">request</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">person</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">updateRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">person</span><span class="p">.</span><span class="na">getId</span><span class="p">()),</span><span class="w"> </span><span class="n">person</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">delete</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ObjectUtils</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">(</span><span class="n">person</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果person 对象为空，则删除全量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">searchList</span><span class="p">(</span><span class="n">index</span><span class="p">).</span><span class="na">forEach</span><span class="p">(</span><span class="n">p</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">deleteRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">p</span><span class="p">.</span><span class="na">getId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">deleteRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">person</span><span class="p">.</span><span class="na">getId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">searchList</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">toSearchList</span><span class="p">(</span><span class="n">search</span><span class="p">(</span><span class="n">index</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">SearchPageHelper</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">searchPage</span><span class="p">(</span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchResponse</span><span class="w"> </span><span class="n">searchResponse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TotalHits</span><span class="w"> </span><span class="n">totalHits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">.</span><span class="na">getHits</span><span class="p">().</span><span class="na">getTotalHits</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SearchPageHelper</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setTotal</span><span class="p">(</span><span class="n">totalHits</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">totalHits</span><span class="p">.</span><span class="na">value</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setRecords</span><span class="p">(</span><span class="n">toSearchList</span><span class="p">(</span><span class="n">searchResponse</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setPageSize</span><span class="p">(</span><span class="n">20L</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">toSearchList</span><span class="p">(</span><span class="n">SearchResponse</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchHit</span><span class="o">[]</span><span class="w"> </span><span class="n">hits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">.</span><span class="na">getHits</span><span class="p">().</span><span class="na">getHits</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">searchList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Arrays</span><span class="p">.</span><span class="na">stream</span><span class="p">(</span><span class="n">hits</span><span class="p">).</span><span class="na">forEach</span><span class="p">(</span><span class="n">hit</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="o">&gt;</span><span class="w"> </span><span class="n">sourceAsMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hit</span><span class="p">.</span><span class="na">getSourceAsMap</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 处理高亮数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">HighlightField</span><span class="o">&gt;</span><span class="w"> </span><span class="n">highlightFields</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hit</span><span class="p">.</span><span class="na">getHighlightFields</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">highlightFields</span><span class="p">.</span><span class="na">forEach</span><span class="p">((</span><span class="n">k</span><span class="p">,</span><span class="w"> </span><span class="n">v</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">v</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">v</span><span class="p">.</span><span class="na">getFragments</span><span class="p">().</span><span class="na">length</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">sourceAsMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">k</span><span class="p">,</span><span class="w"> </span><span class="n">StrUtil</span><span class="p">.</span><span class="na">strip</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">v</span><span class="p">.</span><span class="na">getFragments</span><span class="p">()),</span><span class="w"> </span><span class="s">&#34;[]&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Person</span><span class="w"> </span><span class="n">search</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeanUtil</span><span class="p">.</span><span class="na">mapToBean</span><span class="p">(</span><span class="n">sourceAsMap</span><span class="p">,</span><span class="w"> </span><span class="n">Person</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">searchList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">search</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">searchList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="elasticsearchapplicationtests">ElasticsearchApplicationTests</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@RunWith</span><span class="p">(</span><span class="n">SpringRunner</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@SpringBootTest</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ElasticsearchApplicationTests</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PersonService</span><span class="w"> </span><span class="n">personService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试删除索引
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteIndexTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">deleteIndex</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试创建索引
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">createIndexTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">createIndex</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试新增
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">insertTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">age</span><span class="p">(</span><span class="n">11</span><span class="p">).</span><span class="na">birthday</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">()).</span><span class="na">country</span><span class="p">(</span><span class="s">&#34;CN&#34;</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">1L</span><span class="p">).</span><span class="na">name</span><span class="p">(</span><span class="s">&#34;哈哈&#34;</span><span class="p">).</span><span class="na">remark</span><span class="p">(</span><span class="s">&#34;test1&#34;</span><span class="p">).</span><span class="na">build</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">age</span><span class="p">(</span><span class="n">22</span><span class="p">).</span><span class="na">birthday</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">()).</span><span class="na">country</span><span class="p">(</span><span class="s">&#34;US&#34;</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">2L</span><span class="p">).</span><span class="na">name</span><span class="p">(</span><span class="s">&#34;hiahia&#34;</span><span class="p">).</span><span class="na">remark</span><span class="p">(</span><span class="s">&#34;test2&#34;</span><span class="p">).</span><span class="na">build</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">age</span><span class="p">(</span><span class="n">33</span><span class="p">).</span><span class="na">birthday</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">()).</span><span class="na">country</span><span class="p">(</span><span class="s">&#34;ID&#34;</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">3L</span><span class="p">).</span><span class="na">name</span><span class="p">(</span><span class="s">&#34;呵呵&#34;</span><span class="p">).</span><span class="na">remark</span><span class="p">(</span><span class="s">&#34;test3&#34;</span><span class="p">).</span><span class="na">build</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">insert</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试更新
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">updateTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">age</span><span class="p">(</span><span class="n">33</span><span class="p">).</span><span class="na">birthday</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">()).</span><span class="na">country</span><span class="p">(</span><span class="s">&#34;ID_update&#34;</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">3L</span><span class="p">).</span><span class="na">name</span><span class="p">(</span><span class="s">&#34;呵呵update&#34;</span><span class="p">).</span><span class="na">remark</span><span class="p">(</span><span class="s">&#34;test3_update&#34;</span><span class="p">).</span><span class="na">build</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">update</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试删除
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">delete</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">id</span><span class="p">(</span><span class="n">1L</span><span class="p">).</span><span class="na">build</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">searchListTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">personList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">personService</span><span class="p">.</span><span class="na">searchList</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">personList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试分页查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">searchPageTest</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">pageSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">maxCurrent</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">500</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 此处最大页数设置为500 为es浅分页; 如需深度分页需更换分页方法并移除此条件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">current</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">maxCurrent</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 构造查询条件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SearchRequest</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">searchRequest</span><span class="p">.</span><span class="na">source</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">SearchSourceBuilder</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">trackTotalHits</span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 查询条件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">query</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">boolQuery</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// and</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">.</span><span class="na">must</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">termQuery</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_2</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// or</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">.</span><span class="na">must</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">boolQuery</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">.</span><span class="na">should</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">matchQuery</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">.</span><span class="na">should</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">matchQuery</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">.</span><span class="na">should</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">matchQuery</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 分页</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">from</span><span class="p">((</span><span class="n">current</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">pageSize</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">size</span><span class="p">(</span><span class="n">pageSize</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 相关度排序: SortBuilders.scoreSort()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">sort</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 字段排序 可根据时间</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">SortBuilders</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">.</span><span class="na">fieldSort</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_2</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">.</span><span class="na">order</span><span class="p">(</span><span class="n">SortOrder</span><span class="p">.</span><span class="na">DESC</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 高亮字段</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">highlighter</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HighlightBuilder</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">requireFieldMatch</span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">preTags</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">TAG_HIGH_LIGHT_START</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">field</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_1</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">field</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_2</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">field</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_3</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">postTags</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">TAG_HIGH_LIGHT_END</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchPageHelper</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">personSearchPageHelper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">personService</span><span class="p">.</span><span class="na">searchPage</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">personSearchPageHelper</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="集群架构">集群架构</h2>
+<p>一个运行中的 Elasticsearch 实例称为一个节点，而集群是由一个或者多个拥有相同 cluster.name 配置的节点组成， 它们共同承担数据和负载的压力。 当有节点加入集群中或者从集群中移除节点时，集群将会重新平均分布所有的数据。</p>
+<p>当一个节点被选举成为主节点时， 它将负责管理集群范围内的所有变更，例如增加、 删除索引，或者增加、删除节点等。 而主节点并不需要涉及到文档级别的变更和搜索等操作，所以当集群只拥有一个主节点的情况下，即使流量的增加它也不会成为瓶颈。 任何节点都可以成为主节点。我们的示例集群就只有一个节点，所以它同时也成为了主节点。</p>
+<p>作为用户，我们可以将请求发送到集群中的任何节点 ，包括主节点。 每个节点都知道任意文档所处的位置，并且能够将我们的请求直接转发到存储我们所需文档的节点。 无论我们将请求发送到哪个节点，它都能负责从各个包含我们所需文档的节点收集回数据，并将最终结果返回给客户端。</p>
+<h3 id="搭建集群">搭建集群</h3>
+<ol>
+<li>
+<p>创建 elasticsearch-cluster 文件夹，在内部复制三个 elasticsearch 服务。
+<img alt="Elasticsearch详解-02" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-02.png"></p>
+</li>
+<li>
+<p>修改节点配置; config/elasticsearch.yml 文件</p>
+<ul>
+<li>node-1001 节点
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="c">#集群名称，节点之间要保持一致</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">cluster.name</span><span class="p">:</span><span class="w"> </span><span class="l">my-elasticsearch</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#节点名称，集群内要唯一</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.name</span><span class="p">:</span><span class="w"> </span><span class="l">node-1001</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.master</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.data</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#ip 地址</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">network.host</span><span class="p">:</span><span class="w"> </span><span class="l">localhost</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#http 端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.port</span><span class="p">:</span><span class="w"> </span><span class="m">1001</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#tcp 监听端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">transport.tcp.port</span><span class="p">:</span><span class="w"> </span><span class="m">9301</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#discovery.seed_hosts: [&#34;localhost:9301&#34;, &#34;localhost:9302&#34;,&#34;localhost:9303&#34;]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#discovery.zen.fd.ping_timeout: 1m</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#discovery.zen.fd.ping_retries: 5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#集群内的可以被选为主节点的节点列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#cluster.initial_master_nodes: [&#34;node-1&#34;, &#34;node-2&#34;,&#34;node-3&#34;]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#跨域配置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#action.destructive_requires_name: true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.cors.enabled</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.cors.allow-origin</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;*&#34;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>node-1002 节点
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="w"> </span><span class="c">#集群名称，节点之间要保持一致</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">cluster.name</span><span class="p">:</span><span class="w"> </span><span class="l">my-elasticsearch</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#节点名称，集群内要唯一</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">node.name</span><span class="p">:</span><span class="w"> </span><span class="l">node-1002</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">node.master</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">node.data</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#ip 地址</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">network.host</span><span class="p">:</span><span class="w"> </span><span class="l">localhost</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#http 端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">http.port</span><span class="p">:</span><span class="w"> </span><span class="m">1002</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#tcp 监听端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">transport.tcp.port</span><span class="p">:</span><span class="w"> </span><span class="m">9302</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">discovery.seed_hosts</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="s2">&#34;localhost:9301&#34;</span><span class="p">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">discovery.zen.fd.ping_timeout</span><span class="p">:</span><span class="w"> </span><span class="l">1m</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">discovery.zen.fd.ping_retries</span><span class="p">:</span><span class="w"> </span><span class="m">5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#集群内的可以被选为主节点的节点列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#cluster.initial_master_nodes: [&#34;node-1&#34;, &#34;node-2&#34;,&#34;node-3&#34;]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#跨域配置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#action.destructive_requires_name: true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">http.cors.enabled</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">http.cors.allow-origin</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;*&#34;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>node-1003 节点
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="c">#集群名称，节点之间要保持一致</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">cluster.name</span><span class="p">:</span><span class="w"> </span><span class="l">my-elasticsearch</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#节点名称，集群内要唯一</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.name</span><span class="p">:</span><span class="w"> </span><span class="l">node-1003</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.master</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.data</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#ip 地址</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">network.host</span><span class="p">:</span><span class="w"> </span><span class="l">localhost</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#http 端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.port</span><span class="p">:</span><span class="w"> </span><span class="m">1003</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#tcp 监听端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">transport.tcp.port</span><span class="p">:</span><span class="w"> </span><span class="m">9303</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#候选主节点的地址，在开启服务后可以被选为主节点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">discovery.seed_hosts</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="s2">&#34;localhost:9301&#34;</span><span class="p">,</span><span class="w"> </span><span class="s2">&#34;localhost:9302&#34;</span><span class="p">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">discovery.zen.fd.ping_timeout</span><span class="p">:</span><span class="w"> </span><span class="l">1m</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">discovery.zen.fd.ping_retries</span><span class="p">:</span><span class="w"> </span><span class="m">5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#集群内的可以被选为主节点的节点列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#cluster.initial_master_nodes: [&#34;node-1&#34;, &#34;node-2&#34;,&#34;node-3&#34;]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#跨域配置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#action.destructive_requires_name: true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.cors.enabled</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.cors.allow-origin</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;*&#34;</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+</li>
+<li>
+<p>启动集群; 点击 bin\elasticsearch.bat
+<img alt="Elasticsearch详解-03" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-03.png"></p>
+</li>
+</ol>
+<p>如果启动不起来可能原因是分配内存不足，需要修改 config\jvm.options 文件中的内存属性</p>
+<p>启动之后使用ES可视化工具查看,可使用<a href="https://github.com/mobz/elasticsearch-head">elasticsearch-head</a>,<a href="https://gitee.com/farmerx/ElasticHD">ElasticHD</a></p>
+<h3 id="分布式架构原理">分布式架构原理</h3>
+<p>ElasticSearch 设计的理念就是分布式搜索引擎，底层其实还是基于 lucene 的。核心思想就是在多台机器上启动多个 ES 进程实例，组成了一个 ES 集群。</p>
+<p>ES分布式架构实际上就是对index的拆分,将index拆分成多个分片(shard),将分片分别放到不同的ES上实现集群部署.</p>
+<p><img alt="Elasticsearch详解-05" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-05.png"></p>
+<p>分片优点:</p>
+<ul>
+<li>支持横向扩展: 比如你数据量是 3T，3 个 shard，每个 shard 就 1T 的数据，若现在数据量增加到 4T,怎么扩展，很简单，重新建一个有 4 个 shard 的索引，将数据导进去;</li>
+<li>提高性能: 数据分布在多个 shard，即多台服务器上，所有的操作，都会在多台机器上并行分布式执行，提高了吞吐量和性能;</li>
+</ul>
+<p>分片的数据实际上是有多个备份存在的,会存在一个主分片,还有几个副本分片. 当写入数据的时候先写入主分片,然后并行将数据同步到副本分片上;当读数据的时候会获取到所有分片,负载均衡轮询读取.</p>
+<p>当某个节点宕机了,还有其他分片副本保存在其他的机器上,从而实现了高可用. 如果是非主节点宕机了，那么会由主节点，让那个宕机节点上的主分片的数据转移到其他机器上的副本数据。接着你要是修复了那个宕机机器，重启了之后，主节点会控制将缺失的副本数据分配过去，同步后续修改的数据之类的，让集群恢复正常. 如果是主节点宕机,那么会重新选举一个节点为主节点.</p>
+<h3 id="故障转移">故障转移</h3>
+<p>在一个网络环境里，失败随时都可能发生，在某个分片/节点不知怎么的就处于离线状态，或者由于任何原因消失了，这种情况下，有一个故障转移机制是非常有用并且是强烈推荐的。为此目的，Elasticsearch 允许你创建分片的一份或多份拷贝，这些拷贝叫做复制分片。</p>
+<p>当集群中只有一个节点在运行时，意味着会有一个单点故障问题——没有冗余。 幸运的是，我们只需再启动一个节点即可防止数据丢失。当你在同一台机器上启动了第二个节点时，只要它和第一个节点有同样的 cluster.name 配置，它就会自动发现集群并加入到其中。</p>
+<p>ES最好部署3个以上的节点，并且配置仲裁数大于一半节点，防止master选举的脑裂问题。</p>
+<ul>
+<li>当一个节点掉线，如果该节点是master节点，则通过比较node ID，选择较小ID的节点为master；</li>
+<li>然后由master节点决定分片如何重新分配。同理，新加入节点也是由master决定如何分配分片；</li>
+</ul>
+<blockquote>
+<p>关于master的选举:
+主要是由ZenDiscovery模块负责,包含Ping(节点之间通过这个RPC来发现彼此)和Unicast（单播模块包含-一个主机列表以控制哪些节点需要ping通）这两部分.
+首先对所有可以成为master的节点(可以配置)根据nodeId排序,每次选举每个节点都把自己所知道节点排一次序,然后选出第一个,暂且认为它是master节点
+如果对某个节点的投票数达到一定的值（可以成为master节点数n/2+1）并且该节点自己也选举自己,那这个节点就是master。否则重新选举一直到满足上述条件</p>
+</blockquote>
+<blockquote>
+<p>ES在主节点上产生分歧，产生多个主节点，从而使集群分裂，使得集群处于异常状态。这个现象叫做脑裂。脑裂问题其实就是同一个集群的不同节点对于整个集群的状态有不同的理解，导致操作错乱，类似于精神分裂。</p>
+</blockquote>
+<h3 id="分片控制">分片控制</h3>
+<p>当写入一个文档的时候，文档会被存储到一个主分片中。 Elasticsearch 集群如何知道一个文档应该存放到哪个分片中呢？</p>
+<p>Elasticsearch 集群路由计算公式:</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">shard = hash(routing) % number_of_primary_shards
+</span></span></code></pre></div><p>routing 是一个可变值，默认是文档的 _id ，也可以设置成一个自定义的值。 routing 通过hash 函数生成一个数字，然后这个数字再除以 number_of_primary_shards （主分片的数量）后得到余数 。这个分布在 0 到 number_of_primary_shards-1 之间的余数，就是我们所寻求的文档所在分片的位置。</p>
+<p>这也就是创建索引的时候主分片的数量永远也不会改变的原因,如果数量变化了,那么所有之前路由的值都会无效,文档也再也找不到了.</p>
+<p>用户可以访问任何一个节点获取数据,因为存放的规则一致(副本和主分片存放的数据一致),这个节点称之为协调节点.如果当前节点访问量较大可能被转到其他节点上,所以当发送请求的时候,为了扩展负载,更好的做法是轮询集群中所有的节点.</p>
+<h3 id="写数据流程">写数据流程</h3>
+<p><img alt="Elasticsearch详解-06" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-06.png"></p>
+<ol>
+<li>客户端请请求任意集群节点(协调节点);</li>
+<li>协调节点将请求转换到指定节点(路由计算);</li>
+<li>主分片需要将数据保存;</li>
+<li>主分片将保存数据的请求发送到各个副本;</li>
+<li>各个副本保存后,进行响应;</li>
+<li>主分片进行响应;</li>
+<li>客户端获取响应;</li>
+</ol>
+<p>在客户端收到成功响应时，文档变更已经在主分片和所有副本分片执行完成，变更是安全的。有一些可选的请求参数允许您影响这个过程，可能以数据安全为代价提升性能。</p>
+<p>设置 consistency 参数值会影响写入操作.consistency 参数的值可以设为:</p>
+<ul>
+<li>one ：只要主分片状态 ok 就允许执行写操作;</li>
+<li>all：必须要主分片和所有副本分片的状态没问题才允许执行写操作;</li>
+<li>quorum：默认值为quorum , 即大多数的分片副本状态没问题就允许执行写操作;</li>
+</ul>
+<p>当consistency值设置为quorum时,如果没有足够的副本分片Elasticsearch 会等待.默认情况下,它最多等待 1 分钟,可以使用timeout参数使它更早终止.</p>
+<h3 id="读数据流程">读数据流程</h3>
+<ol>
+<li>客户端发送查询请求到协调节点;</li>
+<li>协调节点计算数据所在的分片及全部的副本位置,为了能负载均衡要轮询所有的分片;</li>
+<li>将请求转发给具体的节点;</li>
+<li>节点返回查询结果,将结果返回给客户端;</li>
+</ol>
+<p>在处理读取请求时，协调结点在每次请求的时候都会通过轮询所有的副本分片来达到负载均衡。在文档被检索时，已经保存的数据可能已经存在于主分片上但是还没有复制到副本分片。 在这种情况下，副本分片可能会报告文档不存在，但是主分片可能成功返回文档。 一旦索引请求成功返回给用户，文档在主分片和副本分片都是可用的。</p>
+<h3 id="搜索数据过程">搜索数据过程</h3>
+<ol>
+<li>客户端发送请求到一个协调节点;</li>
+<li>协调节点计算数据所在的分片及全部的副本位置;</li>
+<li>每个分片将自己的搜索结果（其实就是一些 doc id ）返回给协调节点，由协调节点进行数据的合并、排序、分页等操作，产出最终结果;</li>
+<li>接着由协调节点根据 doc id 去各个节点上拉取实际的 document 数据，最终返回给客户端;</li>
+</ol>
+<h3 id="更新流程">更新流程</h3>
+<ol>
+<li>客户端向某一节点发送更新请求;</li>
+<li>将请求转发到主分片所在的节点;</li>
+<li>从主分片检索文档，修改_source字段中的JSON，并且尝试重新索引主分片的文档。如果文档已经被另一个进程修改,它会重试步骤3 ,超过retry_on_conflict次后放弃;</li>
+<li>如果主节点成功地更新文档，它将新版本的文档并行转发到副本分片，重新建立索引。一旦所有副本分片都返回成功，主节点向协调节点也返回成功，协调节点向客户端返回成功;</li>
+</ol>
+<p>在步骤4中,主分片把更改转发到副本分片时， 它不会转发更新请求。 相反，它转发完整文档的新版本。请记住，这些更改将会异步转发到副本分片，并且不能保证它们以发送它们相同的顺序到达。 如果 Elasticsearch 仅转发更改请求，则可能以错误的顺序应用更改，导致得到损坏的文档。</p>
+<h2 id="原理">原理</h2>
+<p>分片是Elasticsearch最小的工作单元。传统的数据库每个字段存储单个值，但这对全文检索并不够。文本字段中的每个单词需要被搜索，对数据库意味着需要单个字段有索引多值的能力。最好的支持是一个字段多个值需求的数据结构是倒排索引。</p>
+<h3 id="倒排索引">倒排索引</h3>
+<p>Elasticsearch 使用一种称为 倒排索引 的结构，它适用于快速的全文搜索。一个倒排索引由文档中所有不重复词的列表构成，对于其中每个词，有一个包含它的文档列表。 倒排索引（Inverted Index）也叫反向索引，有反向索引必有正向索引。通俗地来讲，正向索引是通过key找value，反向索引则是通过value找key。</p>
+<p>倒排索引示例:</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">| value    | key               |  
+</span></span><span class="line"><span class="cl">|----------|-------------------|   
+</span></span><span class="line"><span class="cl">| my name is zhangsan   | 1001 |  
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">| key     | value|
+</span></span><span class="line"><span class="cl">|---------|------|
+</span></span><span class="line"><span class="cl">| name    | 1001 |
+</span></span><span class="line"><span class="cl">| zhang   | 1001 |
+</span></span><span class="line"><span class="cl">| zhangsan| 1001 |
+</span></span></code></pre></div><p>倒排索引搜索过程: 查询单词是否在词典中,如果不在搜索结束,如果在词典中需要查询单词在倒排列表中的指针,获取单词对应的文档ID,根据文档ID查询时哪一条数据</p>
+<p>词条: 索引中最小的存储和查询单元
+词典: 词条的集合;一般用hash表或B+tree存储
+倒排表: 记录了出现过某个单词的所有文档的文档列表及单词在该文档中出现的位置信息,每条记录称为一个倒排项.根据倒排列表,即可获知哪些文档包含某个单词.</p>
+<h3 id="分析器">分析器</h3>
+<p>倒排索引总是和分词分不开的,中文分词和英文分词是不一样的,所以就需要分析器.</p>
+<p>分析器的主要功能是将一块文本分成适合于倒排索引的独立词条,分析器组成:</p>
+<ul>
+<li>字符过滤器: 在分词前整理字符串,一个字符过滤器可以用来去掉 HTML,或者将 &amp; 转化成 and;</li>
+<li>分词器: 字符串被分词器分为单个的词条,一个简单的分词器遇到空格和标点的时候,可能会将文本拆分成词条;</li>
+<li>词单元过滤器: 按顺序通过每个过滤器,这个过程可能会改变词条（例如，小写化Quick ），删除词条（例如， 像 a， and， the 等无用词），或者增加词条（例如，像jump和leap这种同义词）;</li>
+</ul>
+<p>Elasticsearch附带了可以直接使用的预包装的分析器:</p>
+<ul>
+<li>标准分析器: 默认使用的分析器。它是分析各种语言文本最常用的选择。它根据Unicode 联盟定义的单词边界划分文本。删除绝大部分标点;</li>
+<li>简单分析器: 在任何不是字母的地方分隔文本，将词条小写;</li>
+<li>空格分析器: 在空格的地方划分文本;</li>
+<li>语言分析器: 考虑指定语言的特点,根据语法进行分词; 例如，英语分析器附带了一组英语无用词（常用单词，例如and或者the ,它们对相关性没有多少影响），它们会被删除;</li>
+</ul>
+<p>常用中文分词器: <a href="https://github.com/medcl/elasticsearch-analysis-ik/releases/tag/v7.8.0">ik分词器</a>, 将解压后的后的文件夹放入 ES 根目录下的 plugins 目录下，重启 ES 即可使用.</p>
+<h3 id="文档搜索">文档搜索</h3>
+<p>早期的全文检索会为整个文档集合建立一个很大的倒排索引并将其写入到磁盘。 被写入的索引不可变化,一旦新的索引就绪，旧的就会被其替换.如果你需要让一个新的文档可被搜索，你需要重建整个索引。这要么对一个索引所能包含的数据量造成了很大的限制，要么对索引可被更新的频率造成了很大的限制。</p>
+<p>如何在保留不变性的前提下实现倒排索引的更新?</p>
+<p>用更多的索引。通过增加新的补充索引来反映新的修改，而不是直接重写整个倒排索引。每一个倒排索引都会被轮流查询到,从最早的开始查询完后再对结果进行合并。</p>
+<p>当一个文档被删除时，它实际上只是在文件中被标记删除。一个被标记删除的文档仍然可以被查询匹配到，但它会在最终结果被返回前从结果集中过滤掉。 文档更新也是类似的操作方式:当一个文档被更新时，旧版本文档被标记删除，文档的新版本被索引到一个新的段中。可能两个版本的文档都会被一个查询匹配到，但被删除的那个旧版本文档在结果集返回前就已经被移除。
+当一个查询被触发，所有已知的段按顺序被查询。词项统计会对所有段的结果进行聚合,此时会将标记删除的数据真正的删除.</p>
+<h3 id="近实时搜索">近实时搜索</h3>
+<p>Elasticsearch 的主要功能就是搜索,但是Elasticsearch的搜索功能不是实时的,而是近实时的,主要原因在于ES搜索是分段搜索.</p>
+<p>ES中的每一段就是一个倒排索引,最新的数据更新会体现在最新的段中,而最新的段落盘之后ES才能进行搜索,所以磁盘性能极大影响了ES软件的搜索.ES的主要作用就是快速准确的获取想要的数据,所以降低处理数据的延迟就显得尤为重要.</p>
+<p>ES近实时搜索实现:
+<img alt="Elasticsearch详解-04" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-04.png"></p>
+<ol>
+<li>一个文档被索引之后，就会被添加到内存缓冲区，并且追加到了 translog 事务日志中;(先写入索引中,再写入到日志中,目的防止数据丢失,类似数据库中的事务日志)</li>
+<li>将内存缓冲区中的分片刷新到磁盘中(refresh);此时缓冲区的数据可被搜索,当完全将数据写入磁盘会清空缓冲区中的数据;</li>
+<li>随着不断的刷写,磁盘中的文件会越来越多,此时需要文件段合并;当一个新的索引文件产生之后,文件的更新,删除便会体现出,此时在合并文件的时候便会真正的将数据删除;小的段被合并到大的段，然后这些大的段再被合并到更大的段;</li>
+</ol>
+<h2 id="优化">优化</h2>
+<p>Elasticsearch 在数据量很大的情况下（数十亿级别）如何提高查询效率？</p>
+<h3 id="合理设置分片数">合理设置分片数</h3>
+<p>分片和副本的设计为 ES 提供了支持分布式和故障转移的特性，但并不意味着分片和副本是可以无限分配的。而且索引的分片完成分配后由于索引的路由机制，我们是不能重新修改分片数的.否则将无法找到对应的数据.</p>
+<ul>
+<li>控制每个分片占用的硬盘容量不超过 ES 的最大 JVM 的堆空间设置，因此，如果索引的总容量在 500G 左右，那分片大小在 16 个左右即可;</li>
+<li>考虑一下 node 数量，一般一个节点有时候就是一台物理机，如果分片数过多，大大超过了节点数，很可能会导致一个节点上存在多个分片，一旦该节点故障，即使保持了 1 个以上的副本，同样有可能会导致数据丢失，集群无法恢复。所以， 一般都设置分片数不超过节点数的 3 倍;</li>
+<li>主分片，副本和节点最大数之间数量，我们分配的时候可以参考： 节点数&lt;=主分片数 *（副本数+1）;</li>
+</ul>
+<h3 id="文件缓冲区httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance"><a href="https://doocs.github.io/advanced-java/#/docs/high-concurrency/es-optimizing-query-performance">文件缓冲区</a></h3>
+<p>往 ES 里写的数据，实际上都写到磁盘文件里去了，查询的时候，操作系统会将磁盘文件里的数据自动缓存到 filesystem cache 里面去;ES 的搜索引擎严重依赖于底层的 filesystem cache ，你如果给 filesystem cache 更多的内存，尽量让内存可以容纳所有的 idx segment file  索引数据文件，那么你搜索的时候就基本都是走内存的，性能会非常高。</p>
+<blockquote>
+<p>案例: 某个公司 ES 节点有 3 台机器，每台机器看起来内存很多，64G，总内存就是 64 * 3 = 192G 。每台机器给 ES jvm heap 是 32G ，那么剩下来留给 filesystem cache 的就是每台机器才 32G ，总共集群里给 filesystem cache 的就是 32 * 3 = 96G 内存。而此时，整个磁盘上索引数据文件，在 3 台机器上一共占用了 1T 的磁盘容量，ES 数据量是 1T ，那么每台机器的数据量是 300G 。这样性能好吗？ filesystem cache 的内存才 100G，十分之一的数据可以放内存，其他的都在磁盘，然后你执行搜索操作，大部分操作都是走磁盘，性能肯定差。</p>
+</blockquote>
+<p>归根结底，你要让 ES 性能要好，最佳的情况下，就是你的机器的内存，至少可以容纳你的总数据量的一半。</p>
+<p>根据生产环境实践经验，最佳的情况下，是仅仅在 ES 中就存少量的数据，就是你要用来搜索的那些索引，如果内存留给 filesystem cache 的是 100G，那么你就将索引数据控制在 100G 以内，这样的话，你的数据几乎全部走内存来搜索，性能非常之高，一般可以在 1 秒以内。</p>
+<p>比如说你现在有一行数据。 id,name,age &hellip;. 30 个字段。但是你现在搜索，只需要根据 id,name,age 三个字段来搜索。如果你傻乎乎往 ES 里写入一行数据所有的字段，就会导致说 90% 的数据是不用来搜索的，结果硬是占据了 ES 机器上的 filesystem cache 的空间，单条数据的数据量越大，就会导致 filesystem cahce 能缓存的数据就越少。其实，仅仅写入 ES 中要用来检索的少数几个字段就可以了，比如说就写入 ES id,name,age 三个字段，然后你可以把其他的字段数据存在 mysql/hbase 里，我们一般是建议用 ES + hbase 这么一个架构。</p>
+<p>写入 ES 的数据最好小于等于，或者是略微大于 ES 的 filesystem cache 的内存容量。然后你从 ES 检索可能就花费 20ms，然后再根据 ES 返回的 id 去 hbase 里查询，查 20 条数据，可能也就耗费个 30ms，可能你原来那么玩儿，1T 数据都放 es，会每次查询都是 5~10s，现在可能性能就会很高，每次查询就是 50ms。</p>
+<h3 id="数据预热httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance"><a href="https://doocs.github.io/advanced-java/#/docs/high-concurrency/es-optimizing-query-performance">数据预热</a></h3>
+<p>假如说，哪怕是你就按照上述的方案去做了，ES 集群中每个机器写入的数据量还是超过了 filesystem cache 一倍，比如说你写入一台机器 60G 数据，结果 filesystem cache 就 30G，还是有 30G 数据留在了磁盘上。</p>
+<p>其实可以做数据预热。</p>
+<p>举个例子，拿微博来说，你可以把一些大 V，平时看的人很多的数据，你自己提前后台搞个系统，每隔一会儿，自己的后台系统去搜索一下热数据，刷到 filesystem cache 里去，后面用户实际上来看这个热数据的时候，他们就是直接从内存里搜索了，很快。</p>
+<p>或者是电商，你可以将平时查看最多的一些商品，比如说 iphone 8，热数据提前后台搞个程序，每隔 1 分钟自己主动访问一次，刷到 filesystem cache 里去。</p>
+<p>对于那些你觉得比较热的、经常会有人访问的数据，最好做一个专门的缓存预热子系统，就是对热数据每隔一段时间，就提前访问一下，让数据进入 filesystem cache 里面去。这样下次别人访问的时候，性能一定会好很多。</p>
+<h3 id="冷热分离httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance"><a href="https://doocs.github.io/advanced-java/#/docs/high-concurrency/es-optimizing-query-performance">冷热分离</a></h3>
+<p>ES 可以做类似于 mysql 的水平拆分，就是说将大量的访问很少、频率很低的数据，单独写一个索引，然后将访问很频繁的热数据单独写一个索引。最好是将冷数据写入一个索引中，然后热数据写入另外一个索引中，这样可以确保热数据在被预热之后，尽量都让他们留在 filesystem os cache 里，别让冷数据给冲刷掉。</p>
+<p>假设你有 6 台机器，2 个索引，一个放冷数据，一个放热数据，每个索引 3 个 shard。3 台机器放热数据 index，另外 3 台机器放冷数据 index。然后这样的话，你大量的时间是在访问热数据 index，热数据可能就占总数据量的 10%，此时数据量很少，几乎全都保留在 filesystem cache 里面了，就可以确保热数据的访问性能是很高的。但是对于冷数据而言，是在别的 index 里的，跟热数据 index 不在相同的机器上，大家互相之间都没什么联系了。如果有人访问冷数据，可能大量数据是在磁盘上的，此时性能差点，就 10% 的人去访问冷数据，90% 的人在访问热数据，也无所谓了。</p>
+<h3 id="document模型设计httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance"><a href="https://doocs.github.io/advanced-java/#/docs/high-concurrency/es-optimizing-query-performance">document模型设计</a></h3>
+<p>对于 MySQL，我们经常有一些复杂的关联查询。在 ES 里该怎么玩儿，ES 里面的复杂的关联查询尽量别用，一旦用了性能一般都不太好。</p>
+<p>最好是先在 Java 系统里就完成关联，将关联好的数据直接写入 ES 中。搜索的时候，就不需要利用 ES 的搜索语法来完成 join 之类的关联搜索了。</p>
+<p>document 模型设计是非常重要的，很多操作，不要在搜索的时候才想去执行各种复杂的乱七八糟的操作。ES 能支持的操作就那么多，不要考虑用 ES 做一些它不好操作的事情。如果真的有那种操作，尽量在 document 模型设计的时候，写入的时候就完成。另外对于一些太复杂的操作，比如 join/nested/parent-child 搜索都要尽量避免，性能都很差的。</p>
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diff --git a/blog-site/public/posts/detailed/java-arraylist/index.html b/blog-site/public/posts/detailed/java-arraylist/index.html
new file mode 100644
index 00000000..df6168a9
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@@ -0,0 +1,874 @@
+<!DOCTYPE html>
+<html lang="zh" >
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+                        <h2 id="post_single_title">ArrayList详解</h2>
+                        <span id="post_page_title_date" class="date">2024.06.26</span>
+                        
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+                    <div class="post_content markdown"><h2 id="arraylist">ArrayList</h2>
+<p>在<code>List</code>接口实现类中，最常用的就是<code>ArrayList</code>，<code>ArrayList</code>类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删除元素。
+<code>ArrayList</code>继承了<code>AbstractList</code>，并实现了<code>List</code>、<code>RandomAccess</code>，<code>Cloneable</code>接口：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">RandomAccess</span><span class="p">,</span><span class="n">Cloneable</span><span class="p">,</span><span class="n">Serializable</span><span class="p">{}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="randomaccess">RandomAccess</h3>
+<p><code>Random</code>是随机的意思，<code>Access</code>是访问的意思，合起来<code>RandomAccess</code>就是随机访问的意思。
+<code>RandomAccess</code>接口是一个标记接口，用来标记实现的<code>List</code>集合具备快速随机访问的能力。
+所有的<code>List</code>实现都支持随机访问的，只是基于基本结构的不同，实现的速度不同罢了。</p>
+<p>当一个<code>List</code>拥有快速访问功能时，其遍历方法采用随机访问速度最快，而没有快速随机访问的<code>List</code>采用顺序访问的速度最快。
+如果集合中的数据量过大需要遍历时，此时需要格外注意，因为不同的遍历方式会影响很大，可以使用<code>instanceof</code>关键字来判断该类有没有<code>RandomAccess</code>标记：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 假设 list 数据量非常大,推荐写法
+</span></span><span class="line"><span class="cl">List&lt;Object&gt; list = ...;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">if(list instanceof RandomAccess){
+</span></span><span class="line"><span class="cl">    // 随机访问
+</span></span><span class="line"><span class="cl">    for (int i = 0;i&lt; list.size();i++) {
+</span></span><span class="line"><span class="cl">        System.out.println(list.get(i));
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}else {
+</span></span><span class="line"><span class="cl">    // 顺序访问
+</span></span><span class="line"><span class="cl">    for(Object obj: list) {
+</span></span><span class="line"><span class="cl">        System.out.println(obj);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在<code>List</code>中<code>ArrayList</code>被<code>RandomAccess</code>接口标记，而<code>LinkedList</code>没有被<code>RandomAccess</code>接口标记，所以<code>ArrayList</code>适合随机访问，而<code>LinkedList</code>适合顺序访问。</p>
+<h3 id="cloneable">Cloneable</h3>
+<p><code>Cloneable</code>接口是Java开发中常用的一个接口，它是一个标记接口。
+如果一个想要拷贝一个对象，就需要重写<code>Object</code>中的<code>clone</code>方法并让其实现<code>Cloneable</code>接口。如果只重写<code>clone</code>方法，不实现<code>Cloneable</code>接口就会报<code>CloneNotSupportedException</code>异常。</p>
+<p><code>clone</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>应当注意的是，<code>clone()</code>方法并不是<code>Cloneable</code>接口的方法，而是<code>Object</code>的一个<code>protected</code>方法。
+<code>Cloneable</code>接口只是规定，如果一个类没有实现<code>Cloneable</code>接口又调用了<code>clone</code>方法，就会抛出<code>CloneNotSupportedException</code>。
+换言之，<code>clone</code>方法规定了想要拷贝对象，就需要实现<code>Cloneable</code>方法，<code>clone</code>方法让<code>Cloneable</code>接口变得有意义。</p>
+<p>拷贝分为浅拷贝与深拷贝：</p>
+<ul>
+<li>浅拷贝：被复制对象的所有值属性都含有与原来对象的相同，而所有的对象引用属性仍然指向原来的对象；</li>
+<li>深拷贝：在浅拷贝的基础上，所有引用其他对象的变量也进行了<code>clone</code>，并指向被复制过的新对象；</li>
+</ul>
+<p>如果一个被复制的属性都是基本类型，那么只需要实现当前类的<code>Cloneable</code>机制就可以了，此为浅拷贝。
+如果被复制对象的属性包含其他实体类对象引用，那么这些实体类对象都需要实现<code>Cloneable</code>接口并覆盖<code>clone</code>方法。
+<code>ArrayList</code>中<code>clone</code>方法可以创建一个浅拷贝。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// ArrayList类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">transient</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elementData</span><span class="p">;</span><span class="w">     
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Returns a shallow copy of this &lt;tt&gt;ArrayList&lt;/tt&gt; instance.  (The
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * elements themselves are not copied.)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return a clone of this &lt;tt&gt;ArrayList&lt;/tt&gt; instance
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 调用Object类的clone方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ArrayList</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">ArrayList</span><span class="o">&lt;?&gt;</span><span class="p">)</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将集合中的元素进行拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="p">.</span><span class="na">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="p">.</span><span class="na">modCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">v</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// this shouldn&#39;t happen, since we are Cloneable</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InternalError</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// Arrays类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Arrays</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="nf">copyOf</span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newLength</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">copyOf</span><span class="p">(</span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="n">newLength</span><span class="p">,</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">getClass</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="p">,</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="nf">copyOf</span><span class="p">(</span><span class="n">U</span><span class="o">[]</span><span class="w"> </span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newLength</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">T</span><span class="o">[]&gt;</span><span class="w"> </span><span class="n">newType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">copy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">((</span><span class="n">Object</span><span class="p">)</span><span class="n">newType</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p">(</span><span class="n">Object</span><span class="p">)</span><span class="n">Object</span><span class="o">[]</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">?</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="o">[</span><span class="n">newLength</span><span class="o">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">Array</span><span class="p">.</span><span class="na">newInstance</span><span class="p">(</span><span class="n">newType</span><span class="p">.</span><span class="na">getComponentType</span><span class="p">(),</span><span class="w"> </span><span class="n">newLength</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">copy</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">original</span><span class="p">.</span><span class="na">length</span><span class="p">,</span><span class="w"> </span><span class="n">newLength</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">copy</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>ArrayList</code>中核心方法最终调用<code>Arrays.copyOf</code>方法，其中调用<code>Arrays.newInstance</code>方法或者创建一个新数组，<code>Arrays.newInstance</code>方法作用，是创建具有指定组件类型和长度的新数组。
+所以不论怎样都会创建一个<code>Object</code>数组。最后使用<code>System.arraycopy</code>方法将之前的旧数组中的元素拷贝到新创建的数组中，然后赋值给<code>ArrayList.elementData</code>对象并返回。</p>
+<p>如果需要深拷贝，即复制对象及其引用的所有对象，需要手动实现拷贝逻辑，通常涉及遍历列表并复制每个元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Item</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Item</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayListCopy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建并初始化一个ArrayList</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Item</span><span class="o">&gt;</span><span class="w"> </span><span class="n">originalList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;C&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 深拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Item</span><span class="o">&gt;</span><span class="w"> </span><span class="n">deepCopy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Item</span><span class="w"> </span><span class="n">item</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">originalList</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">deepCopy</span><span class="p">.</span><span class="na">add</span><span class="p">((</span><span class="n">Item</span><span class="p">)</span><span class="w"> </span><span class="n">item</span><span class="p">.</span><span class="na">clone</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 修改原始列表的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">).</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Z&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Original List: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">originalList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Deep Copy: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">deepCopy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="arraylist扩容">ArrayList扩容</h3>
+<p>因为<code>ArrayList</code>底层使用数组保存数据的，而数组一旦被创建就不能改变大小，但是<code>ArrayList</code>的长度是可以改变的，所以可以通过<code>ArrayList</code>类中的<code>add</code>方法找到数组扩容方法。
+<code>add</code>方法调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">add 
+</span></span><span class="line"><span class="cl">    -&gt; ensureCapacityInternal()
+</span></span><span class="line"><span class="cl">    -&gt; calculateCapacity()
+</span></span><span class="line"><span class="cl">    -&gt; ensureExplicitCapacity()
+</span></span><span class="line"><span class="cl">    -&gt; grow()
+</span></span></code></pre></div><p>通过<code>add</code>方法，最终找到了<code>grow</code>方法，也就是扩容的核心方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">grow</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">minCapacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// overflow-conscious code</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elementData</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">minCapacity</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">minCapacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">MAX_ARRAY_SIZE</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hugeCapacity</span><span class="p">(</span><span class="n">minCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// minCapacity is usually close to size, so this is a win:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>ArrayList</code>如果没有指定容量创建数组，默认会创建一个长度为10的数组用来保存元素，之后通过<code>grow</code>方法中的这段代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p><code>&gt;&gt;</code>右移几位就是相当于除以2的几次幂，所以每次扩容都是原容量的1.5倍。最后通过<code>Arrays.copyOf</code>方法将之前的数组中元素，全部移到新创建的数组上。</p>
+<p>由于频繁的扩容数组会对性能产生影响，如果在<code>ArrayList</code>中要存储很大的数据，需要在<code>ArrayList</code>的有参构造中指定数组的长度，来减少扩容的次数。
+需要注意的是创建指定长度的<code>ArrayList</code>，在没有<code>add</code>之前<code>ArrayList</code>中的数组已经初始化了，但是<code>List</code>的大小没变，因为<code>List</code>的大小是由<code>size</code>决定的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="p">(</span><span class="n">1000000</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><h3 id="arraylist与linkedlist">ArrayList与LinkedList</h3>
+<p><code>ArrayList</code>与<code>LinkedList</code>性能比较是一道经典的面试题，先说答案<code>ArrayList</code>查找快，增删慢，而<code>LinkedList</code>增删快，查找慢。
+造成这种原因是因为底层的数据结构不一样。<code>ArrayList</code>底层是数组，而数组的中的元素内存分配都是连续的，并且数组中的元素只能存放一种，这就造成了数组中的元素地址是有规律的，数组中查找元素快速的原因正是利用了这一特点。
+查询方式为: 首地址＋(元素类型长度*下标)。例如：<code>new int arr[5]; arr</code>数组的地址假设为<code>0x1000</code>，那么<code>arr[3]</code>地址可看作为 <code>0x1000 + (3 * 4)</code>，3为数组下标，4为int元素类型长度。</p>
+<p>而<code>LinkedList</code>在Java中的底层结构是对象，每一个对象结点中都保存了下一个结点的位置形成的链表结构，由于<code>LinkedList</code>元素的地址是不连续的，所以没办法按照数组那样去查找，所以就比较慢。</p>
+<p>由于数组一旦分配了大小就不能改变，所以<code>ArrayList</code>在进行添加操作时会创建新的数组，如果要添加到<code>ArrayList</code>中的指定的位置，是通过<code>System.arraycopy</code>方法将数组进行复制，新的数组会将待插入的指定位置空余出来，最后在将元素添加到集合中。
+在进行删除操作时是通过<code>System.arraycopy</code>方法，将待删除元素后面剩余元素复制到待删除元素的位置。当<code>ArrayList</code>里有大量数据时，这时候去频繁插入或删除元素会触发底层数组频繁拷贝，所以效率不高，还会造成内存空间的浪费。</p>
+<p><code>LinkedList</code>在进行添加，删除操作时，会用二分查找法找到将要添加或删除的元素，之后再设置对象的下一个结点来进行添加或删除操作，所以增加删除的效率高。</p>
+<blockquote>
+<p>二分查找法：也称为折半查找法，是一种适用于大量数据查找的方法，但是要求数据必须的排好序的，每次以中间的值进行比较，根据比较的结果可以直接舍去一半的值，直至全部找完（可能会找不到）或者找到数据为止。
+此处LinkedList会比较查找的元素是距离头结点比较近，还是尾结点比较近，距离哪边较近则从哪边开始查找。</p>
+</blockquote>
+<p><code>ArrayList</code>获取元素效率非常的高，时间复杂度是<code>O(1)</code>，而查找、插入和删除元素效率似乎不太高，时间复杂度为<code>O(n)</code>。
+<code>LinkedList</code>与<code>ArrayList</code>相反，获取第几个元素依次遍历复杂度<code>O(n)</code>，添加到末尾复杂度<code>O(1)</code>，添加到指定位置复杂度<code>O(n)</code>，删除元素直接指针指向操作复杂度<code>O(1)</code>。</p>
+<p>注意，<code>ArrayList</code>的增删不一定比<code>LinkedList</code>效率低，但是<code>ArrayList</code>查找效率一定比<code>LinkedList</code>高。
+如果在靠近末尾的地方插入，那么<code>ArrayList</code>只需要移动较少的数据，而<code>LinkedList</code>则需要一直查找到列表尾部，反而耗费较多时间，这时<code>ArrayList</code>就比<code>LinkedList</code>要快。</p>
+<p>所以在实际开发中，<code>ArrayList</code>适用于需要快速随机访问和较少插入删除操作的场景，而<code>LinkedList</code>适用于频繁插入删除操作和需要实现队列或双端队列的场景。</p>
+<h3 id="线程安全">线程安全</h3>
+<p>众所周知，<code>ArrayList</code>是线程不安全的，因为它不保证在多线程环境下的同步操作，当多个线程同时访问和修改同一个<code>ArrayList</code>对象时可能会导致数据不一致或抛出异常。
+多线程下抛出<code>ConcurrentModificationException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果没有报错，需要多试几次</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrayList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">arrayList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">arrayList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>出现该异常的原因是集合中的<code>fail-fast</code>机制。在查看源码的时候，发现调用<code>remove</code>方法时，会执行<code>checkForComodification</code>方法。
+若<code>modCount</code>不等于<code>expectedModCount</code>，则抛出<code>ConcurrentModificationException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkForComodification</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那为什么会抛出<code>ConcurrentModificationException</code>异常呢？
+在调用<code>add</code>方法时，会修改<code>modCount++</code>。一个线程调用<code>add</code>方法，一个线程调用<code>next</code>遍历方法，都共同读取<code>modCount</code>变量的值。
+因为是多线程操作，<code>expectedModCount</code>、<code>modCount</code>变量为公共的，所以很容易出现<code>modCount != expectedModCount</code>，所以便抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 添加元素到指定的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">element</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IndexOutOfBoundsException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;Index: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Size: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 修改modCount</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ensureCapacity</span><span class="p">(</span><span class="n">size</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">  </span><span class="c1">// Increments modCount!!</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">element</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">size</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>因此，在多线程环境中使用<code>ArrayList</code>时，需要手动同步操作，或者使用线程安全的集合类。保证<code>ArrayList</code>线程安全有以下几种方法：</p>
+<ol>
+<li>可以使用 <code>Vector</code> 来代替 <code>ArrayList</code>。<code>Vector</code>是线程安全的<code>ArrayList</code>，但是由于底层是加了<code>synchronized</code>，性能略差不推荐使用；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List list = new Vector();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+<li>使用<code>Collections.synchronizedArrayList()</code> 来创建 <code>ArrayList</code>。使用<code>Collections</code>工具类来创建<code>ArrayList</code>的思路是，在<code>ArrayList</code>的外边套了一个<code>synchronized</code>外壳，来保证<code>ArrayList</code>线程安全；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List list = Collections.synchronizedArrayList();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+<li>使用<code>CopyOnWriteArrayList()</code>来保证 <code>ArrayList</code> 线程安全。<code>CopyWriteArrayList</code>字面意思就是在写的时候复制，主要思想就是读写分离的思想。
+<code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>，所以保证了某个线程在写的时候不会被打断；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">CopyOnWriteArrayList&lt;String&gt; list = new CopyOnWriteArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+</ol>
+<p>其中比较推荐的解决方案是使用<code>CopyOnWriteArrayList</code>。
+<code>CopyWriteArrayList</code>字面意思就是在写的时候复制，思想就是读写分离的思想。它的基本原理是每次修改操作都会创建该列表的一个新副本，因此读操作不需要加锁，可以并发执行。
+以下是<code>CopyOnWriteArrayList</code>的<code>add()</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The array, accessed only via getArray/setArray. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The lock protecting all mutators */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Gets the array.  Non-private so as to also be accessible
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * from CopyOnWriteArraySet class.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="nf">getArray</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Appends the specified element to the end of this list.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param e element to be appended to this list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@code true}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">lock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elements</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">newElements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elements</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newElements</span><span class="o">[</span><span class="n">len</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setArray</span><span class="p">(</span><span class="n">newElements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>保证了某个线程在写的时候不会被打断。
+可以看到源码开始先是复制了一份数组，同一时刻只有一个线程写，其余的线程会读。在复制的数组上边进行写操作，写好以后在返回<code>true</code>。
+这样就把读写进行了分离，写好以后因为<code>array</code>加了<code>volatile</code>修饰，所以该数组是对于其他的线程是可见的，就会读取到最新的值。
+由于每次写操作都会创建一个数组的新副本，所以写操作的开销较大。但是读取操作非常高效且不需要加锁，因此适用于读操作远多于写操作的场景，例如缓存、白名单等。</p>
+<h3 id="arraylist安全删除">ArrayList安全删除</h3>
+<p>在<code>ArrayList</code>中删除元素时，&ldquo;安全删除&rdquo; 指的是在删除元素过程中避免出现异常或错误，并确保集合的结构和元素的状态保持一致。
+在使用增强型<code>for-each</code>循环遍历<code>ArrayList</code>时，如果尝试删除元素，会抛出<code>ConcurrentModificationException</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayListError</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;C&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;D&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">element</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">element</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">element</span><span class="p">);</span><span class="w"> </span><span class="c1">// 这会抛出 ConcurrentModificationException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在前面讲过<code>add</code>方法，会操作<code>modCount</code>变量的值，在查看源码的时候，发现调用<code>remove</code>方法时，也会操作<code>modCount</code>变量的值。
+当调用<code>remove</code>方法时执行了<code>modCount++</code>，此时<code>modCount</code>变成了<code>N+1</code>。然后接着再循环中遍历调用<code>next</code>方法，调用<code>checkForComodification</code>比较<code>expectedModCount</code>和<code>modCount</code>的大小，此时<code>modCount != expectedModCount</code>，便抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkForComodification</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c1">// 删除指定位置的元素 </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RangeCheck</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 修改modCount</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">modCount</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">E</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">E</span><span class="p">)</span><span class="w"> </span><span class="n">elementData</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">numMoved</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">numMoved</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">numMoved</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="o">[--</span><span class="n">size</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="c1">// Let gc do its work</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">oldValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>安全删除的关键在于，确保在遍历和删除操作中不会同时对集合的结构造成不一致性，从而导致程序运行时出现异常或者结果不符合预期。</p>
+<p>最经典的解决方案是使用<code>Iterator</code>遍历集合，在遍历过程中删除元素。在使用迭代器遍历<code>ArrayList</code>时，迭代器会维护一个<code>expectedModCount</code>，它记录了迭代开始时的<code>modCount</code>。
+每次调用迭代器的<code>next</code>方法时，都会检查当前的<code>modCount</code>是否与<code>expectedModCount</code>相等，如果不相等就抛出<code>ConcurrentModificationException</code>异常。使用迭代器的<code>remove()</code>方法能够确保在删除元素时，同步更新，从而避免异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ArrayList&lt;String&gt; list = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 添加元素到列表中
+</span></span><span class="line"><span class="cl">Iterator&lt;String&gt; iterator = list.iterator();
+</span></span><span class="line"><span class="cl">while (iterator.hasNext()) {
+</span></span><span class="line"><span class="cl">    String element = iterator.next();
+</span></span><span class="line"><span class="cl">    if (/* 满足删除条件 */) {
+</span></span><span class="line"><span class="cl">        iterator.remove(); // 使用迭代器的 remove 方法安全删除元素
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></div>
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\ No newline at end of file
diff --git a/blog-site/public/posts/detailed/java-hashmap/index.html b/blog-site/public/posts/detailed/java-hashmap/index.html
new file mode 100644
index 00000000..4e5f5426
--- /dev/null
+++ b/blog-site/public/posts/detailed/java-hashmap/index.html
@@ -0,0 +1,1060 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>HashMap详解 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+
+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap">
+                    HashMap
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e7%bb%93%e6%9e%84">
+                    HashMap结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hash%e5%86%b2%e7%aa%81">
+                    Hash冲突
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e5%ae%b9%e9%87%8f">
+                    HashMap容量
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e6%89%a9%e5%ae%b9">
+                    HashMap扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#17%e6%89%a9%e5%ae%b9">
+                    1.7扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#18%e6%89%a9%e5%ae%b9">
+                    1.8扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e8%80%83%e6%96%87%e7%ab%a0">
+                    参考文章
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
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+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
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+                
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+                    <i class="ri-rss-fill"></i>
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+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                        <h2 id="post_single_title">HashMap详解</h2>
+                        <span id="post_page_title_date" class="date">2021.05.03</span>
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+                    <div class="post_content markdown"><h2 id="hashmap">HashMap</h2>
+<p><code>HashMap</code>是一个散列表，它存储的内容是键值对(<code>key-value</code>)映射。
+<code>HashMap</code>实现了<code>Map</code>接口，根据键的<code>HashCode</code>值存储数据，具有很快的访问速度，最多允许一条记录的键为<code>null</code>，不支持线程同步。<code>HashMap</code>是无序的，即不会记录插入的顺序。</p>
+<p>相关操作：</p>
+<ul>
+<li>存储：通过<code>key</code>的<code>hashcode</code>方法找到在<code>hashMap</code>存储的位置，如果该位置有元素则通过<code>equals</code>方法进行比较，如果<code>equals</code>返回值为<code>true</code>，则覆盖<code>value</code>；
+如果<code>equals</code>返回值为<code>false</code>则在该数组元素的头部追加该元素，形成一个链表结构；</li>
+<li>读取：通过<code>key</code>的<code>hashcode</code>方法获取元素存在该数组的位置，然后通过<code>equals</code>拿到该值；</li>
+</ul>
+<p>总的来说<code>hashMap</code>底层将<code>key-value</code>当成一个整体来处，<code>hashMap</code>底层采用一个<code>Entry</code>数组保存所有的键值对。
+当存储一个<code>entry</code>对象时，会根据<code>key</code>的<code>hashCode</code>来决定存放在数组中的位置，再根据<code>equals</code>方法来确定在链表中的位置，读取一个<code>entry</code>对象。
+<code>equals</code>和<code>hashCode</code>在<code>hashMap</code>中就像一个坐标一样，来定位<code>hashMap</code>中的值。</p>
+<h3 id="hashmap结构">HashMap结构</h3>
+<p><img alt="HashMap结构" src="/iblog/posts/annex/images/essays/HashMap%E7%BB%93%E6%9E%84.png"></p>
+<p>在JDK1.7及之前结构为<code>数组+单向链表</code>，JDK1.8及之后结构为<code>数组 + 单向链表/红黑树</code>。
+在JDK1.8时，如果存储<code>Map</code>中数组元素对应的索引的每个链表超过8，就将单向链表转化为红黑树，当红黑树的节点少于6个的时候又开始使用链表。</p>
+<p>那么为什么要使用红黑树？
+当有发生大量的<code>hash</code>冲突时，因为链表遍历效率很慢，为了提升查询的效率，所以使用了红黑树的数据结构。</p>
+<p>为什么不一开始就用红黑树代替链表结构？</p>
+<blockquote>
+<p>Because TreeNodes are about twice the size of regular nodes, we use them only when bins contain enough nodes to warrant use  (see TREEIFY_THRESHOLD).
+And when they become too small (due to removal or resizing) they are converted back to plain bins.</p>
+</blockquote>
+<p>这是JDK文档注释，大意为：单个<code>TreeNode</code>需要占用的空间大约是普通<code>Node</code>的两倍，所以只有当包含足够多的<code>Nodes</code>时才会转成<code>TreeNodes</code>，而是否足够多就是由<code>TREEIFY_THRESHOLD</code>的值(默认值8)决定的。
+而当桶中节点数由于移除或者<code>resize</code>变少后，又会变回普通的链表的形式，以便节省空间，这个阈值是<code>UNTREEIFY_THRESHOLD</code>(默认值6)。</p>
+<p>为什么树化阈值要设置为8？
+如果<code>hashCode</code>分布良好，也就是<code>hash</code>计算的结果离散好的话，那么红黑树这种形式是很少会被用到的，因为各个值都均匀分布，很少出现链表很长的情况。
+在理想情况下，链表长度符合泊松分布，各个长度的命中概率依次递减，当长度为8的时候，概率仅为0.00000006。
+这是一个小于千万分之一的概率，通常我们的<code>Map</code>里面是不会存储这么多的数据的，所以通常情况下，并不会发生从链表向红黑树的转换。</p>
+<p><code>HashMap</code>是通过<code>hash</code>算法来判断对象应该放在哪个桶里面的。JDK并不能阻止我们用户实现自己的哈希算法，如果我们故意把哈希算法变得不均匀，那么每次存放对象很容易造成<code>hash</code>冲突。
+链表长度超过8就转为红黑树的设计，更多的是为了防止用户自己实现了不好的哈希算法时导致链表过长，从而导致查询效率低，而此时转为红黑树更多的是一种保底策略，用来保证极端情况下查询的效率。
+红黑树的引入保证了在大量<code>hash</code>冲突的情况下，<code>HashMap</code>还具有良好的查询性能。</p>
+<p>那么在JDK1.8引入红黑树后，如果单链表节点个数超过8个是否一定会树化？
+这是不一定的，在进行树化之前会进行判断<code>(n = tab.length) &lt; MIN_TREEIFY_CAPACITY)</code>是否需要扩容，如果表中数组元素小于这个阈值（默认是64），就会进行扩容。
+因为扩容不仅能增加表中的容量，还能缩短单链表的节点数，从而更长远的解决链表遍历慢问题。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Replaces all linked nodes in bin at index for given hash unless
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * table is too small, in which case resizes instead.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">treeifyBin</span><span class="p">(</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tab</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MIN_TREEIFY_CAPACITY</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">tl</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">replacementTreeNode</span><span class="p">(</span><span class="n">e</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tl</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">hd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">p</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tl</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tl</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">tab</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hd</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">hd</span><span class="p">.</span><span class="na">treeify</span><span class="p">(</span><span class="n">tab</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hash冲突">Hash冲突</h3>
+<p>在<code>HashMap</code>中，哈希冲突，也叫<code>Hash</code>碰撞，是指两个不同的键通过同一散列函数计算得到的哈希值相同，从而映射到同一个桶中。
+当插入<code>HashMap</code>中元素的<code>key</code>出现重复时，这个时候就发生了<code>Hash</code>冲突了。哈希冲突是哈希表必须处理的问题。</p>
+<p>链地址法是处理哈希冲突的常见方法之一，它在每个桶中使用一个链表来存储所有映射到该桶的键值对。具体插入步骤：</p>
+<ol>
+<li>计算键的哈希值并确定其在数组中的位置；</li>
+<li>如果桶为空，直接将键值对存储在该桶中；</li>
+<li>如果桶不为空，则遍历桶中的链表，检查是否存在相同的键；</li>
+</ol>
+<ul>
+<li>如果存在相同的键，更新对应的值；</li>
+<li>如果不存在相同的键，将新的键值对添加到链表的末尾；</li>
+</ul>
+<p>在Java8及更高版本中，为了提高性能，当单个桶中的链表长度超过一定阈值（默认是 8）时，会将链表转换为红黑树。
+这种方法在大量冲突的情况下提供了更高效的查找和插入性能。具体插入步骤：</p>
+<ol>
+<li>计算键的哈希值确定存储位置；</li>
+<li>如果存储位置为空，则直接插入新键值对；</li>
+<li>如果存储位置已有节点，当链表长度超过阈值（默认为 8），将链表转换为红黑树，否则继续用链表存储；</li>
+<li>如果当前结点为红黑树结点，则根据节点的哈希值和键值比较，找到合适的插入位置；插入后，根据红黑树的性质进行调整，保持平衡；</li>
+<li>当桶中元素数量减少到一定阈值以下时（默认是 6），会将红黑树转换回链表，以减少内存开销；</li>
+</ol>
+<h3 id="hashmap容量">HashMap容量</h3>
+<p><code>HashMap</code>在创建时需要指定初始容量，如果不指定默认是16。初始容量指的是<code>HashMap</code>中桶的数量，即存储键值对的数组大小。
+如果能预估要存储的键值对数量，可以在创建<code>HashMap</code>时指定初始容量，以避免频繁的扩容操作。</p>
+<p>如果指定容量大小为10，那么实际大小是多少？
+先说答案，实际大小是16，其容量为不小于指定容量的2的N次方。</p>
+<p>为什么容量始终是2的N次方？
+为了减少<code>Hash</code>碰撞，尽量使<code>Hash</code>算法的结果均匀分布。</p>
+<p>当使用<code>put</code>方法时，到底存入<code>HashMap</code>的哪个数组中？
+这是通过<code>hash</code>算法决定的，如果某一个数组中的链表过长旧会影响查询的效率。为了避免出现<code>hash</code>碰撞，让<code>hash</code>尽可能的散列分布，就需要在<code>hash</code>算法上做文章。</p>
+<p>JDK1.7通过逻辑与运算，判断这个元素该进入哪个数组。在下面的代码中<code>length</code>的长度始终为不小于指定容量的2的N次方。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">indexFor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">h</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为了更好的理解这个方法，举个例子，假设<code>h=2</code>或<code>h=3</code>，<code>length=15</code>，执行<code>indexFor</code>方法，最终逻辑与运算后的结果是一致的，因为最终结果是一致的所以就导致了<code>hash</code>碰撞。
+这种问题多了以后会造成容器中的元素分布不均匀，都分配在同一个数组上，在查询的时候就减慢了查询的效率，另一方面也造成空间的浪费。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">-- 2转换为2进制与15-1进行&amp;运算
+</span></span><span class="line"><span class="cl">  0000 0010
+</span></span><span class="line"><span class="cl">&amp; 0000 1110 
+</span></span><span class="line"><span class="cl">———————————— 
+</span></span><span class="line"><span class="cl">  0000 1110
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 3转换为2进制与15-1进行&amp;运算
+</span></span><span class="line"><span class="cl">  0000 0011
+</span></span><span class="line"><span class="cl">&amp; 0000 1110 
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0000 1110
+</span></span></code></pre></div><p>为了避免上面<code>length=15</code>这类问题出现，所以集合的容量采用必须是2的N次幂这种方式。
+因为2的N次幂的结果减一转换为二进制后都是以<code>...1111</code>结尾的，所以在进行逻辑与运算时碰撞几率小。</p>
+<p>在JDK1.8中，在<code>putVal</code>方法中通过<code>i = (n - 1) &amp; hash</code>来计算key的散列地址：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">putVal</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">onlyIfAbsent</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">evict</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 此处省略了代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// i = (n - 1) &amp; hash]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 省略了代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这里的&quot;&amp;&ldquo;等同于&rdquo;%&quot;，但是&quot;%&ldquo;运算的速度并没有&rdquo;&amp;&ldquo;的操作速度快。
+&ldquo;&amp;&ldquo;操作能代替&rdquo;%&ldquo;运算，但必须满足一定的条件，即<code>a%b=a&amp;(b-1)</code>仅当b是2的n次方的时候才成立。</p>
+<p>容器容量怎么保持始终为2的N次方？
+<code>HashMap</code>的<code>tableSizeFor</code>方法做了处理，能保证永远都是2的N次幂。
+如果用户指定了初始容量，那么<code>HashMap</code>会计算出比该数大的第一个2的幂作为初始容量。另外就是在扩容的时候，也是进行成倍的扩容，即4变成8、8变成16。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Returns a power of two size for the given target capacity.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">tableSizeFor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">cap</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 假设n=17</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = 00010001 - 00010000 = 00010000 = 16</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cap</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00010000 | 00001000) = 00011000 = 24</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011000 | 00000110) = 00011110 = 30</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011110 | 00000001) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011111 | 00000000) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">8</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011111 | 00000000) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">16</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = 00011111 = 31，MAXIMUM_CAPACITY：Integer的最大长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// (31 &lt; 0) ? 1 : (31 &gt;= Integer的最大长度) ? Integer的最大长度 : 31 + 1 ;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 即最终返回 32 = 2 的 (n=5)次方</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>发现上面在进行<code>&gt;&gt;&gt;</code>操作时会将<code>cap</code>变量的二进制值变为最高位后边全是1，即<code>00010001 -&gt; 00011111</code>，所以这个算法就导致了任意传入一个数值，会将该数字变为它的2倍减1，因为任何尾数全为1的在加1都为2的倍数。
+至于开头减1，是因为如果给定的n已经是2的次幂，但是不进行减1操作的话，那么得到的值就是大于给定值的最小2的次幂值，例如，传入4就会返回8。
+这里面最大右移到16位，因为最大值是32个1，这是int类型存储变量的最大值，在往后就没意义了。</p>
+<p><code>HashMap</code>默认初始化容量为什么是16？
+这个问题没有找到相关解释。我推断这应该就是个经验值，既然一定要设置一个默认的<code>2^n</code>作为初始值，那么就需要在效率和内存使用上做一个权衡。
+这个值既不能太小，也不能太大，太小了就有可能频繁发生扩容，影响效率；太大了又浪费空间，不划算。所以16就作为一个经验值被采用了。</p>
+<p>关于默认容量的定义，故意把16写成<code>1 &lt;&lt; 4</code>这种形式，就是提醒开发者，这个地方要是2的次幂，与上面呼应。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * The default initial capacity - MUST be a power of two.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w"> </span><span class="c1">// aka 16</span><span class="w">
+</span></span></span></code></pre></div><p>那么<code>HashMap</code>初始化容量设置多少合适？
+当我们使用<code>HashMap(int initialCapacity)</code>来初始化容量的时候，<code>HashMap</code>并不会使用我们传进来的<code>initialCapacity</code>直接作为初始容量。
+JDK会默认帮我们计算一个相对合理的值当做初始容量，所谓合理值，其实是找到第一个比用户传入的值大的2的幂。
+如果创建<code>HashMap</code>初始化容量设置为7，那么<code>HashMap</code>通过计算会创建一个初始化为8的<code>HashMap</code>。当<code>HashMap</code>中的元素到<code>0.75 * 8 = 6</code>就会进行<strong>扩容</strong>，这明显是我们不希望看到的。</p>
+<blockquote>
+<p>负载因子，表示HashMap满的程度，默认值为0.75f，也就是说默认情况下，当HashMap中元素个数达到了容量的3/4的时候就会进行自动扩容；</p>
+</blockquote>
+<p>设置多少合适，可以参考JDK8中<code>putAll</code>方法中的实现：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">(int) ((float) expectedSize / 0.75F + 1.0F);
+</span></span></code></pre></div><p>通过<code>expectedSize/0.75F+1.0F</code>计算，将初始化容量设置为7带入，得到<code>7/0.75+1=10</code>，10经过JDK处理之后，会被设置成16，这就大大的减少了扩容的几率。
+当我们明确知道<code>HashMap</code>中元素的个数的时候，把默认容量设置成<code>expectedSize/0.75F+1.0F</code> 是一个在性能上相对好的选择，但同时也会牺牲些内存。</p>
+<p>这个算法在<code>guava</code>中也有实现，开发的时候，可以直接通过<code>Maps</code>类创建一个<code>HashMap</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Maps</span><span class="p">.</span><span class="na">newHashMapWithExpectedSize</span><span class="p">(</span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">newHashMapWithExpectedSize</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedSize</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="p">(</span><span class="n">capacity</span><span class="p">(</span><span class="n">expectedSize</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">capacity</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedSize</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">expectedSize</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">3</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CollectPreconditions</span><span class="p">.</span><span class="na">checkNonnegative</span><span class="p">(</span><span class="n">expectedSize</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;expectedSize&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">expectedSize</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">expectedSize</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1073741824</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)((</span><span class="kt">float</span><span class="p">)</span><span class="n">expectedSize</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">75F</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">.</span><span class="na">0F</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">2147483647</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hashmap扩容">HashMap扩容</h3>
+<p>随着<code>HashMap</code>中的元素增加，<code>Hash</code>碰撞导致获取元素方法的效率就会越来越低。为了保证获取元素方法的效率，所以针对<code>HashMap</code>中的数组进行扩容。
+扩容数组的方式只能再去开辟一个新的数组，并把之前的元素转移到新数组上。</p>
+<p><code>HashMap</code>的容量是有上限的，必须小于<code>1&lt;&lt;30</code>，即<code>1073741824</code>。如果容量超出了这个数，则不再增长，且阈值会被设置为<code>Integer.MAX_VALUE</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// Java8
+</span></span><span class="line"><span class="cl">if (oldCap &gt;= MAXIMUM_CAPACITY) {
+</span></span><span class="line"><span class="cl">    threshold = Integer.MAX_VALUE;
+</span></span><span class="line"><span class="cl">    return oldTab;
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// Java7
+</span></span><span class="line"><span class="cl">if (oldCapacity == MAXIMUM_CAPACITY) { 
+</span></span><span class="line"><span class="cl">    threshold = Integer.MAX_VALUE;
+</span></span><span class="line"><span class="cl">    return;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在<code>HashMap</code>中有一个概念叫<code>loadFactor</code>，即负载因子，它表示<code>HashMap</code>满的程度，默认值为<code>0.75f</code>，也就是说默认情况下，当<code>HashMap</code>中元素个数达到了容量的3/4的时候就会进行自动扩容。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>为什么负载因子默认设置为0.75？</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * The load factor used when none specified in constructor.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">DEFAULT_LOAD_FACTOR</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">75f</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>在<a href="https://docs.oracle.com/javase/6/docs/api/java/util/HashMap.html">JDK的官方文档</a>中解释如下：</p>
+<blockquote>
+<p>As a general rule, the default load factor (.75) offers a good tradeoff between time and space costs.
+Higher values decrease the space overhead but increase the lookup cost (reflected in most of the operations of the HashMap class, including get and put).
+The expected number of entries in the map and its load factor should be taken into account when setting its initial capacity, so as to minimize the number of rehash operations.
+If the initial capacity is greater than the maximum number of entries divided by the load factor, no rehash operations will ever occur.</p>
+</blockquote>
+<p>文档大意：一般来说，默认的负载因子(0.75)在时间和空间成本之间提供了很好的权衡。
+更高的值减少了空间开销，但增加了查找成本(反映在<code>HashMap</code>类的大多数操作中，包括<code>get</code>和<code>put</code>)。
+在设置映射的初始容量时，应该考虑映射中预期的条目数及其负载因子，以便最小化重哈希操作的数量。如果初始容量大于最大条目数除以负载因子，则不会发生重新散列操作。</p>
+<p>负载因子和<code>HashMap</code>中的扩容有关，当<code>HashMap</code>中的元素大于临界值（<code>threshold = loadFactor * capacity</code>）就会扩容。
+所以负载因子的大小决定了什么时机扩容，扩容又影响到了hash碰撞的频率，所以设置一个合理的负载因子可以有效的避免<code>hash</code>碰撞。</p>
+<p>设置为0.75的其他解释：</p>
+<ul>
+<li>根据数学公式推算，这个值在<code>log(2)</code>的时候比较合理；</li>
+<li>为了提升扩容效率，<code>HashMap</code>的容量有一个固定的要求，那就是一定是2的幂。如果负载因子是3/4的话，那么和容量的乘积结果就可以是一个整数；</li>
+</ul>
+<h4 id="17扩容">1.7扩容</h4>
+<p>扩容步骤：</p>
+<ol>
+<li>当插入新的键值对使得元素数量超过阈值时，<code>HashMap</code>会进行扩容；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">addEntry</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">bucketIndex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//size：The number of key-value mappings contained in this map.  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//threshold：The next size value at which to resize (capacity * load factor)  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//数组扩容条件：1.已经存在的key-value mappings的个数大于等于阈值  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//             2.底层数组的bucketIndex坐标处不等于null  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="kc">null</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">table</span><span class="o">[</span><span class="n">bucketIndex</span><span class="o">]</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">(</span><span class="n">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">table</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="c1">//扩容之后，数组长度变了  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hash</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kc">null</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">hash</span><span class="p">(</span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="c1">//为什么要再次计算一下hash值呢？  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bucketIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">indexFor</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">table</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="c1">//扩容之后，数组长度变了，在数组的下标跟数组长度有关，得重算。  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">createEntry</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="n">bucketIndex</span><span class="p">);</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w"> 
+</span></span></span></code></pre></div></li>
+<li>创建一个新的数组，新的容量是原来的两倍，新阈值=新容量*负载因子；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">resize</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">   </span><span class="c1">//传入新的容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">oldTable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">    </span><span class="c1">//引用扩容前的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldTable</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  </span><span class="c1">//扩容前的数组大小如果已经达到最大(2^30)了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w"> </span><span class="c1">//修改阈值为int的最大值(2^31-1)，这样以后就不会扩容了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">newTable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Entry</span><span class="o">[</span><span class="n">newCapacity</span><span class="o">]</span><span class="p">;</span><span class="w">  </span><span class="c1">//初始化一个新的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">transfer</span><span class="p">(</span><span class="n">newTable</span><span class="p">);</span><span class="w">                         </span><span class="c1">//！！将数据转移到新的Entry数组里</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">table</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="p">;</span><span class="w">                           </span><span class="c1">//HashMap的table属性引用新的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">);</span><span class="c1">//修改阈值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>将旧表中的所有元素重新计算哈希值，并放入新表中：通过<code>transfer</code>方法将旧数组上的元素转移到扩容后的新数组上。遍历旧表中的每个桶，对于每个桶中的每个节点，重新计算它们在新表中的索引位置，将节点放入新表的相应位置；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">transfer</span><span class="p">(</span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">newTable</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">src</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">                   </span><span class="c1">//src引用了旧的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">src</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">//遍历旧的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">src</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">             </span><span class="c1">//取得旧Entry数组的每个元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">src</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="c1">//释放旧Entry数组的对象引用（for循环后，旧的Entry数组不再引用任何对象）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">indexFor</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="p">,</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">);</span><span class="w"> </span><span class="c1">//！！重新计算每个元素在数组中的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">//标记[1]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">newTable</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">      </span><span class="c1">//将元素放在数组上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">             </span><span class="c1">//访问下一个Entry链上的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>将旧表引用指向新表；</li>
+</ol>
+<h4 id="18扩容">1.8扩容</h4>
+<p>Java1.8的<code>HashMap</code>扩容原理与1.7类似，但有一些重要改进。
+在1.8时做了一些优化，文档注释写的很清楚：&ldquo;元素的位置要么是在原位置，要么是在原位置再移动<strong>2次幂的位置</strong>&quot;。也就是对比1.7的迁移到新的数组上省去了重新计算<code>hash</code>值的时间。</p>
+<p>这里的&quot;2次幂的位置&quot;是指长度为原来数组元素两倍的位置。
+假设旧容量是16，那么其二进制表示是<code>10000</code>，扩容后的新容量是32，其二进制表示是<code>100000</code>。<code>HashMap</code>通过<code>h &amp; (length - 1)</code>计算索引。
+在扩容之前，容量为16，根据公式<code>hash &amp; (oldCapacity - 1)</code>计算，因为<code>oldCapacity - 1</code>的二进制是<code>0000 1111</code>，那么计算索引时使用的是哈希值的低四位。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">扩容之前的位置：
+</span></span><span class="line"><span class="cl">  0101 0101
+</span></span><span class="line"><span class="cl">&amp; 0000 1111
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0000 0101
+</span></span></code></pre></div><p>扩容后，新的索引还是通过<code>hash &amp; (newCapacity - 1)</code>计算的，若容量为32，因为<code>newCapacity - 1</code>的二进制是<code>0001 1111</code>，那么计算索引时使用的是哈希值的低五位。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">扩容之后的位置：
+</span></span><span class="line"><span class="cl">  0101 0101
+</span></span><span class="line"><span class="cl">&amp; 0001 1111
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0001 0101
+</span></span></code></pre></div><p>扩容后，新的索引位置只受到哈希值高位的影响，所以叫高位优化。
+高位优化的关键在于，如果一个哈希值在旧容量下的索引是<code>index</code>，那么在新容量下，这个哈希值要么在<code>index</code>位置，要么在<code>index + oldCapacity</code>位置。
+例如上面的例子，容量为16，扩容之前的位置为<code>0000 0101</code>即5，扩容之后的位置为<code>0001 0101</code>即21（16+5）。
+通过这种高位优化技术，Java1.8中的<code>HashMap</code>在扩容时无需重新计算所有元素的哈希值，只需根据哈希值的高位来判断元素的新位置，所以提高了扩容的效率。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Initializes or doubles table size.  If null, allocates in
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * accord with initial capacity target held in field threshold.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Otherwise, because we are using power-of-two expansion, the
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * elements from each bin must either stay at same index, or move
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * with a power of two offset in the new table.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return the table
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="nf">resize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">oldTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">oldTab</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">oldTab</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">threshold</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newCap</span><span class="p">,</span><span class="w"> </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">oldTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCap</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                     </span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldThr</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// double threshold</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldThr</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="c1">// initial capacity was placed in threshold</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldThr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">               </span><span class="c1">// zero initial threshold signifies using defaults</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)(</span><span class="n">DEFAULT_LOAD_FACTOR</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newThr</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">float</span><span class="w"> </span><span class="n">ft</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="n">newCap</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">newCap</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">ft</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">?</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                      </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">ft</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newThr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">({</span><span class="s">&#34;rawtypes&#34;</span><span class="p">,</span><span class="s">&#34;unchecked&#34;</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">newTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">[</span><span class="n">newCap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">table</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldTab</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">oldCap</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">oldTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 单个节点，直接移动到新表中的新位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">newTab</span><span class="o">[</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">newCap</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 红黑树节点，处理红黑树的拆分逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">((</span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">e</span><span class="p">).</span><span class="na">split</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">newTab</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="p">,</span><span class="w"> </span><span class="n">oldCap</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// preserve order</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 处理链表节点，使用高位优化技术重新分配节点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">loHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">loTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hiHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">hiTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                           </span><span class="c1">// 判断节点在新表中的位置，高位优化的关键</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">oldCap</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                               </span><span class="c1">// 保持在原位置（低位链表）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">loHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">loTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">loTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                               </span><span class="c1">// 移动到新位置（高位链表）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">hiTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">hiHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">hiTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">hiTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 将低位链表和高位链表分别放入新表中的相应位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loTail</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">loTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">newTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">loHead</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">hiTail</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">hiTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">newTab</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">oldCap</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hiHead</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">newTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="线程安全">线程安全</h3>
+<p><code>HashMap</code>是线程不安全的集合类。因为<code>HashMap</code>中的方法大多没有同步，这意味着如果一个线程在遍历<code>HashMap</code>的同时，另一个线程修改了<code>HashMap</code>，例如添加或删除元素，可能会导致<code>ConcurrentModificationException</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="n">Object</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">(),</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">map</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>更严重的是，当多个线程中的<code>HashMap</code>同时扩容时，再使用<code>put</code>方法添加元素，如果<code>hash</code>值相同，可能出现同时在同一数组下用链表表示，造成闭环，导致在<code>get</code>时会出现死循环，CPU飙升到100%。</p>
+<p>在大多数并发场景中，推荐使用<code>ConcurrentHashMap</code>，因为它设计用于高并发环境，并且在大多数情况下性能优于使用同步包装或手动同步的<code>HashMap</code>。
+<code>ConcurrentHashMap</code>是Java中的一种线程安全的哈希表实现，用来替代传统的<code>HashMap</code>，来解决在多线程环境中并发修改带来的问题。
+与<code>Hashtable</code>不同，<code>ConcurrentHashMap</code>不对整个表进行全局加锁。相反它只对具体操作涉及的部分进行加锁，减少了线程之间的竞争。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConcurrentHashMapExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ConcurrentHashMap</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentHashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;One&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Two&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Value for key 1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">keySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Key: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Value: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="参考文章">参考文章</h2>
+<ul>
+<li><a href="https://blog.csdn.net/u010841296/article/details/82832166">https://blog.csdn.net/u010841296/article/details/82832166</a></li>
+<li><a href="https://blog.csdn.net/Elliot_Elliot/article/details/115610387">https://blog.csdn.net/Elliot_Elliot/article/details/115610387</a></li>
+<li><a href="https://blog.csdn.net/pange1991/article/details/82347284">https://blog.csdn.net/pange1991/article/details/82347284</a></li>
+<li><a href="https://blog.csdn.net/xiewenfeng520/article/details/107119970">https://blog.csdn.net/xiewenfeng520/article/details/107119970</a></li>
+<li><a href="https://zhuanlan.zhihu.com/p/114363420">https://zhuanlan.zhihu.com/p/114363420</a></li>
+<li><a href="https://www.yuque.com/renyong-jmovm/kb/vso1h5">https://www.yuque.com/renyong-jmovm/kb/vso1h5</a></li>
+<li><a href="https://juejin.cn/post/6844903554264596487">https://juejin.cn/post/6844903554264596487</a></li>
+<li><a href="http://hollischuang.gitee.io/tobetopjavaer/#/basics/java-basic/hashmap-init-capacity">http://hollischuang.gitee.io/tobetopjavaer/#/basics/java-basic/hashmap-init-capacity</a></li>
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+    
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+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
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+                <a class="nav-link text-left" href="#%e5%b8%b8%e8%a7%81mq%e5%af%b9%e6%af%94">
+                    常见MQ对比
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+                <a class="nav-link text-left" href="#jms%e6%b6%88%e6%81%af%e6%a8%a1%e5%9e%8b">
+                    JMS消息模型
+                </a>
+            </li>
+            
+            
+        </ul>
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%82%b9%e5%af%b9%e7%82%b9%e6%a8%a1%e5%bc%8f">
+                    点对点模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%91%e5%b8%83%e8%ae%a2%e9%98%85%e6%a8%a1%e5%bc%8f">
+                    发布订阅模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#kafka">
+                    kafka
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e7%a1%80%e6%9e%b6%e6%9e%84">
+                    基础架构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%91%e5%b8%83%e8%ae%a2%e9%98%85%e5%b7%a5%e4%bd%9c%e6%b5%81%e7%a8%8b">
+                    发布订阅工作流程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85">
+                    生产者
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85%e6%96%87%e4%bb%b6%e5%ad%98%e5%82%a8">
+                    生产者文件存储
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85%e5%88%86%e5%8c%ba%e7%ad%96%e7%95%a5">
+                    生产者分区策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85%e6%95%b0%e6%8d%ae%e5%8f%af%e9%9d%a0%e6%80%a7%e4%bf%9d%e8%af%81">
+                    生产者数据可靠性保证
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85%e6%95%b0%e6%8d%ae%e4%b8%80%e8%87%b4%e6%80%a7%e4%bf%9d%e8%af%81">
+                    生产者数据一致性保证
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85ack%e6%9c%ba%e5%88%b6">
+                    生产者ack机制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#exactlyonce">
+                    ExactlyOnce
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85%e5%8f%91%e9%80%81%e6%b6%88%e6%81%af%e6%b5%81%e7%a8%8b">
+                    生产者发送消息流程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b6%88%e8%b4%b9%e8%80%85">
+                    消费者
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b6%88%e8%b4%b9%e8%80%85%e5%88%86%e5%8c%ba%e5%88%86%e9%85%8d%e7%ad%96%e7%95%a5">
+                    消费者分区分配策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b6%88%e8%b4%b9%e8%80%85%e6%b6%88%e8%b4%b9%e6%95%b0%e6%8d%ae%e9%97%ae%e9%a2%98">
+                    消费者消费数据问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#kafka%e4%ba%8b%e5%8a%a1">
+                    kafka事务
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b6%88%e6%81%af%e7%a7%af%e5%8e%8b">
+                    消息积压
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_pic" title="导出图片" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_markdown" title="导出markdown" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_doc" title="导出文档" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                        <h2 id="post_single_title">Kafka详解</h2>
+                        <span id="post_page_title_date" class="date">2021.10.19</span>
+                        
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+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>MQ 即 messagequeue 消息队列，是分布式系统的重要组件，主要解决异步消息，应用解耦，消峰等问题。从而实现高可用，高性能，可伸缩和最终一致性的架构。使用较多的MQ有：activeMQ，rabbitMQ，kafka，metaMQ。</p>
+<h2 id="mq优点">MQ优点</h2>
+<ul>
+<li><strong>异步消息处理</strong>：可以将一些非核心流程，如日志，短信，邮件等，通过MQ的方式异步去处理。这样做的好处是缩短主流程的响应时间，提升用户体验；</li>
+<li><strong>应用解耦合</strong>：商品服务和订单服务之间。用户下单后，订单服务会通知商品服务。不使用MQ的情况是订单服务调用商品服务的接口，这样订单服务和商品服务之间是耦合的；使用MQ，订单服务完成持久化处理，将消息写入MQ消息队列中，返回用户订单下单成功，商品服务来订阅这个下单的消息，采用拉或推的方式获得下单信息，商品服务根据商品下单信息进行商品库存信息修改，这样当下单时商品服务不可用时，也不影响正常下单，这就完成了订单服务和商品服务之间的解耦；</li>
+<li><strong>流量消峰</strong>：秒杀活动流量过大，导致流量暴增，最终可能导致应用挂掉。一般会在应用前端加入消息队列来控制活动人数，假如消息队列超过最大数量，应该直接抛弃用户请求或者跳转到错误页面。秒杀业务根据消息队列中的请求信息在做后续的业务处理。比如在抢购时，可能一下子过来了10万个请求，但MQ只接受前100个用户的请求，超过100个不接收了。这样就成功限制了用户请求；</li>
+</ul>
+<h2 id="mq缺点">MQ缺点</h2>
+<ul>
+<li>系统可用性降低: 系统引入的外部依赖越多，越容易挂掉;</li>
+<li>系统复杂度提高: 加个 MQ 进来，你怎么保证消息没有重复消费？怎么处理消息丢失的情况？怎么保证消息传递的顺序性？头大头大，问题一大堆，痛苦不已;</li>
+<li>一致性问题: A 系统处理完了直接返回成功了，人都以为你这个请求就成功了；但是问题是，要是 BCD 三个系统那里，BD 两个系统写库成功了，结果 C 系统写库失败了，你这数据就不一致了;</li>
+</ul>
+<h2 id="常见mq对比">常见MQ对比</h2>
+<table>
+<thead>
+<tr>
+<th>特性</th>
+<th>ActiveMQ</th>
+<th>RabbitMQ</th>
+<th>RocketMQ</th>
+<th>Kafka</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>单机吞吐量</td>
+<td>万级，比 RocketMQ、Kafka 低一个数量级</td>
+<td>同 ActiveMQ</td>
+<td>10 万级，支撑高吞吐</td>
+<td>10 万级，高吞吐，一般配合大数据类的系统来进行实时数据计算、日志采集等场景</td>
+</tr>
+<tr>
+<td>topic 数量对吞吐量的影响</td>
+<td></td>
+<td></td>
+<td>topic 可以达到几百/几千的级别，吞吐量会有较小幅度的下降，这是 RocketMQ 的一大优势，在同等机器下，可以支撑大量的 topic</td>
+<td>topic 从几十到几百个时候，吞吐量会大幅度下降，在同等机器下，Kafka 尽量保证 topic 数量不要过多，如果要支撑大规模的 topic，需要增加更多的机器资源</td>
+</tr>
+<tr>
+<td>时效性</td>
+<td>ms 级</td>
+<td>微秒级，这是 RabbitMQ 的一大特点，延迟最低</td>
+<td>ms 级</td>
+<td>延迟在 ms 级以内</td>
+</tr>
+<tr>
+<td>可用性</td>
+<td>高，基于主从架构实现高可用</td>
+<td>同 ActiveMQ</td>
+<td>非常高，分布式架构</td>
+<td>非常高，分布式，一个数据多个副本，少数机器宕机，不会丢失数据，不会导致不可用</td>
+</tr>
+<tr>
+<td>消息可靠性</td>
+<td>有较低的概率丢失数据</td>
+<td>基本不丢</td>
+<td>经过参数优化配置，可以做到 0 丢失</td>
+<td>同 RocketMQ</td>
+</tr>
+<tr>
+<td>功能支持</td>
+<td>MQ 领域的功能极其完备</td>
+<td>基于 erlang 开发，并发能力很强，性能极好，延时很低</td>
+<td>MQ 功能较为完善，还是分布式的，扩展性好</td>
+<td>功能较为简单，主要支持简单的 MQ 功能，在大数据领域的实时计算以及日志采集被大规模使用</td>
+</tr>
+</tbody>
+</table>
+<p>一般的业务系统要引入 MQ，最早大家都用 ActiveMQ，但是现在确实大家用的不多了，没经过大规模吞吐量场景的验证，社区也不是很活跃，所以大家还是算了吧，我个人不推荐用这个了。</p>
+<p>后来大家开始用 RabbitMQ，但是确实 erlang 语言阻止了大量的 Java 工程师去深入研究和掌控它，对公司而言，几乎处于不可控的状态，但是确实人家是开源的，比较稳定的支持，活跃度也高。</p>
+<p>不过现在确实越来越多的公司会去用 RocketMQ，确实很不错，毕竟是阿里出品，但社区可能有突然黄掉的风险,目前 RocketMQ 已捐给 Apache，但 GitHub 上的活跃度其实不算高,对自己公司技术实力有绝对自信的，推荐用 RocketMQ，否则回去老老实实用 RabbitMQ 吧，人家有活跃的开源社区，绝对不会黄。</p>
+<p>所以中小型公司，技术实力较为一般，技术挑战不是特别高，用 RabbitMQ 是不错的选择；大型公司，基础架构研发实力较强，用 RocketMQ 是很好的选择。</p>
+<p>如果是大数据领域的实时计算、日志采集等场景，用 Kafka 是业内标准的，绝对没问题，社区活跃度很高，绝对不会黄，何况几乎是全世界这个领域的事实性规范。</p>
+<h2 id="jms消息模型">JMS消息模型</h2>
+<p>JMS即JavaMessageService，Java消息服务应用程序接口，是一个Java平台中关于面向消息中间件的API，用于在两个应用程序之间，或分布式系统中发送消息，进行异步通信。</p>
+<p>JMS是基于JVM的消息代理规范，ActiveMQ、HornetMQ等是JMS的实现。</p>
+<p>Java消息服务是一个与具体平台无关的API，绝大多数MOM提供商都对JMS提供支持。我们可以简单的理解：两个应用程序之间需要进行通信，我们使用一个JMS服务，进行中间的转发，通过JMS的使用，我们可以解除两个程序之间的耦合。</p>
+<h3 id="点对点模式">点对点模式</h3>
+<p>消息发送者发送消息，消息代理将其放入消息队列中，消息接受者从队列中获取消息，消息读取后被移除消息队列。每个消息都被发送到一个特定的队列，接收者从队列中获取消息。队列保留着消息，直到它们被消费或超时。</p>
+<p><img alt="MQ详解-001" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-001.png"></p>
+<p>虽然可能有多个客户端在队列中侦听消息，但只有一个可以读取到消息，之后消息将不存在，其他消费者将无法读取。也就是说消息队列只有唯一一个发送者和<em>接受者</em>，但是并不能说只有一个<em>接收者</em>。</p>
+<p>特点：</p>
+<ul>
+<li>每个消息只有一个消费者，即消息一旦被消费，消息就不在消息队列中；</li>
+<li>发送者和接收者之间在时间上没有依赖性，也就是说当发送者发送了消息之后，不管接收者有没有正在运行，它不会影响到消息被发送到队列；</li>
+<li>接收者在成功接收消息之后需向队列应答成功；</li>
+</ul>
+<h3 id="发布订阅模式">发布订阅模式</h3>
+<p>发布者将消息发送到主题Topic中，多个订阅者订阅这个主题，订阅者不断的去轮询监听消息队列中的消息，那么就会在消息到达的同时接收消息。</p>
+<p><img alt="MQ详解-002" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-002.png"></p>
+<p>特点：</p>
+<ul>
+<li>每个消息可以有多个消费者，消费完消息之后消息不会清除；</li>
+<li>发布者和订阅者之间有时间上的依赖性：针对某个主题(Topic)的订阅者，它必须创建一个订阅之后，才能消费发布者的消息，而且为了消费消息，订阅者必须保持运行的状态。当然，为了缓和这种严格的时间相关性，JMS允许订阅者创建一个可持久化的订阅。这样即使订阅者没有运行，它也能接收到发布者的消息；</li>
+</ul>
+<h2 id="kafka">kafka</h2>
+<p>kafka是一个分布式的基于发布/订阅模式的消息队列，主要应用于大数据实时处理领域。</p>
+<h3 id="基础架构">基础架构</h3>
+<p><img alt="MQ详解-003" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-003.png"></p>
+<ul>
+<li>Producer：消息生产者，向kafka推送消息；</li>
+<li>Consumer：消息消费者，向kafka中broker获取消息的客户端；</li>
+<li>Topic：主题，可以理解为一个队列，生产者和消费者面向的都是一个topic；</li>
+<li>Broker：经纪人，一台kafka服务器就是一个broker。一个集群由多个broker组成。一个broker可以容纳多个topic；</li>
+<li>Partition：分区，为了实现扩展性，一个非常大的topic可以分布到多个服务器上，一个主题可以分为多个分区，每个分区是一个有序的队列；</li>
+<li>ConsumerGroup：消费者组，由多个消费者组成。消费者组内每个消费者负责消费不同分区的数据，一个分区只能由一个消费者组内的一个消费者消费；消费者组之间互不影响。所有的消费者都属于某个消费者组，即消费者组是逻辑上的一个订阅者；</li>
+<li>Replica：副本，为保证集群中的某个节点发生故障时，该节点上的分区数据不丢失，且kafka仍然能够继续工作，kafka提供了副本机制，一个topic的每个分区都有若干个副本，一个leader和若干个follower；</li>
+<li>Leader：每个分区多个副本的“主”，生产者发送数据的对象，以及消费者消费数据的对象都是leader。leader是针对topic的，而不是broker的，即不同的kafka服务区中会出现同一个leader；</li>
+<li>Follower：每个分区多个副本中的“从”，实时从leader中同步数据，保持和leader数据的同步。leader发生故障时，某个Follower会成为新的leader；</li>
+<li>Controller：Kafka 集群中有一个broker会被选举为Controller，负责管理集群broker的上下线，所有topic的分区副本分配和leader选举等工作，Controller的管理工作都是依赖于Zookeeper的；</li>
+</ul>
+<p>消费者组的作用为了提高消费能力，即提高并发。</p>
+<p>解耦合是消息队列作用之一，当消费者宕机后，再次启动的时候会继续消费消息，而不是从头消费消息。因为这个特性所以消费者会保存一些消费的进度信息，被称为offset，保存的位置在kafka0.9之前保存在zookpeer当中，在此之后保存在kafka本地。即最终kafka会将消息保存在本地磁盘中，默认保留168个小时，即7天。</p>
+<p>kafka中消息是以topic进行分类的，producer生产消息，consumer消费消息，都是面向topic的。topic是逻辑上的概念，而partition是物理上的概念，每个partition对应于一个log文件，该log文件中存储的就是producer生产的数据。</p>
+<p>Producer生产的数据会被不断追加到该log文件末端，且每条数据都有自己的offset。consumer组中的每个consumer，都会实时记录自己消费到了哪个offset，以便出错恢复时，从上次的位置继续消费。</p>
+<h3 id="发布订阅工作流程">发布订阅工作流程</h3>
+<p><img alt="MQ详解-004" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-004.png"></p>
+<ol>
+<li>生产者定期向主题发送消息；</li>
+<li>kafka代理将所有消息存储在为特定主题配置的分区中。它确保消息在分区之间平均共享。如果生产者发送了两个消息，并且有两个分区，kafka将在第一个分区中存储一个消息，在第二个分区中存储第二个消息；</li>
+<li>消费者订阅主题后，kafka将向消费者提供该主题的当前偏移量，并将偏移量保存在Zookeeper集合中；</li>
+<li>消费者将定期向kafka请求新消息,一旦kafka从生产者那里收到消息，它将把这些消息转发给消费者，消费者将收到消息并进行处理；</li>
+<li>消息处理后，消费者将向kafka代理发送确认；</li>
+<li>一旦kafka收到确认，它将偏移量更改为新值并在Zookeeper中对其进行更新。由于在Zookeeper中保留了偏移量，因此即使在服务器出现故障时，使用者也可以正确读取下一条消息；</li>
+<li>4、5、6步骤流程将重复进行，直到消费者停止请求为止；</li>
+</ol>
+<p>消费者可以选择随时倒退或跳至所需的主题偏移量并阅读所有后续消息。</p>
+<h3 id="生产者">生产者</h3>
+<h4 id="生产者文件存储">生产者文件存储</h4>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.jianshu.com/p/3e54a5a39683">https://www.jianshu.com/p/3e54a5a39683</a></li>
+</ul>
+<p><img alt="MQ详解-005" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-005.png"></p>
+<p>由于生产者生产的消息会不断追加到log文件末尾，为防止log文件过大导致数据定位效率低下，kafka采取了分片和索引机制，将每个partition分为多个segment。
+每个segment对应两个文件：“.index”文件和“.log”文件。这些文件位于一个文件夹下，该文件夹的命名规则为：topic名称+分区序号。例如，first这个topic有三个分区，则其对应的文件夹为 first-0,first-1,first-2。其中，每个segment中的日志数据文件大小均相等。</p>
+<blockquote>
+<p>该日志数据文件的大小可以通过在kafka Broker的config/server.properties配置文件的中的“log.segment.bytes”进行设置，默认为1G大小（1073741824字节），在顺序写入消息时如果超出该设定的阈值，将会创建一组新的日志数据和索引文件。</p>
+</blockquote>
+<p>“.index”文件存储大量的索引信息，“.log”文件存储大量的数据，索引文件中的元数据指向对应数据文件中message的物理偏移地址。其中文件的命名是以第一个数据的偏移量来命名的。</p>
+<p><strong>kafka如何通过index文件快速找到log文件中的数据？</strong></p>
+<p>根据指定的偏移量，使用二分法查询定位出该偏移量对应的消息所在的分段索引文件和日志数据文件。然后通过二分查找法，继续查找出小于等于指定偏移量的最大偏移量，同时也得出了对应的position即实际物理位置。</p>
+<p>根据该物理位置在分段的日志数据文件中顺序扫描查找偏移量与指定偏移量相等的消息。由于index文件中的每条对应log文件中存储内容大小都相同，所以想要找到指定的消息，只需要用index文件中的该条的大小加上该条的偏移量即可得出log文件中指定消息的位置。</p>
+<p><img alt="MQ详解-006" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-006.png"></p>
+<h4 id="生产者分区策略">生产者分区策略</h4>
+<p>分区的原因：</p>
+<ul>
+<li>方便在集群中扩展，每个Partition可以通过调整以适应它所在的机器，而一个topic又可以有多个Partition组成，因此整个集群就可以适应适合的数据了；</li>
+<li>可以提高并发，因为可以以Partition为单位读写了，每个partition在不同的服务区上；</li>
+</ul>
+<p><img alt="MQ详解-007" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-007.png"></p>
+<ul>
+<li>在指明partition的情况下，直接将指明的值直接作为partiton值；</li>
+<li>在没有指明partition值但有key的情况下，将key的hash 值与topic的partition数进行取余得到partition值；</li>
+<li>既没有partition值又没有key值的情况下，第一次调用时随机生成一个整数（后面每次调用在这个整数上自增），将这个值与topic可用的partition总数取余得到partition值，也就是常说的round-robin算法；</li>
+</ul>
+<h4 id="生产者数据可靠性保证">生产者数据可靠性保证</h4>
+<p>为保证 producer 发送的数据，能可靠的发送到指定的 topic，topic 的每个 partition 收到 producer 发送的数据后，都需要向 producer 发送 ack(acknowledgement 确认收到)，如果 producer 收到 ack，就会进行下一轮的发送，否则重新发送数据。</p>
+<p><img alt="MQ详解-008" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-008.png"></p>
+<table>
+<thead>
+<tr>
+<th>方案</th>
+<th>优点</th>
+<th>缺点</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>半数以上完成同步，就发 送 ack</td>
+<td>延迟低</td>
+<td>选举新的 leader 时，容忍 n 台 节点的故障，需要 2n+1 个副本</td>
+</tr>
+<tr>
+<td>全部完成同步，才发送ack</td>
+<td>选举新的 leader 时，容忍 n 台 节点的故障，需要 n+1 个副 本</td>
+<td>延迟高</td>
+</tr>
+</tbody>
+</table>
+<blockquote>
+<p>理解 2n+1：
+半数以上完成同步才可以发ACK，如果挂了n台有副本的服务器，那么就需要有另外n台正常发送（这样正常发送的刚好是总数（挂的和没挂的）的一半（n（挂的）+n（正常的）=2n））,因为是半数以上所以2n+1.(所以总数2n+1的时候最多只能容忍n台有故障)</p>
+<p>即，如果挂了n台有副本的服务器，那么存在副本的服务器的总和为 2n+1</p>
+</blockquote>
+<p>kafka选择了第二种方案，原因如下:
+1.同样为了容忍 n 台节点的故障，第一种方案需要 2n+1 个副本，而第二种方案只需要 n+1 个副本，而 kafka 的每个分区都有大量的数据，第一种方案会造成大量数据的冗余；
+2.虽然第二种方案的网络延迟会比较高，但网络延迟对 kafka 的影响较小；</p>
+<p>采用第二种方案之后，设想以下情景： leader 收到数据，所有 follower 都开始同步数据，但有一个 follower，因为某种故障，迟迟不能与 leader 进行同步，那 leader 就要一直等下去，直到它完成同步，才能发送 ack。这个问题怎么解决呢？</p>
+<p>Leader 维护了一个动态的 in-sync replica set 即ISR。</p>
+<p>当和 leader 保持同步的 follower 集合。当 ISR 中的 follower 完成数据的同步之后，就会给 leader 发送 ack。如果 follower长时间未向leader同步数据，则该follower将被踢出ISR，该时间阈值由replica.lag.time.max.ms参数设定。 Leader 发生故障之后，就会从 ISR 中选举新的 leader。</p>
+<blockquote>
+<p>kafka是通过消息条数差值(replica.lag.time.max.messages) 加 通信时间长短(同步时间replica.lag.time.max.ms) 两个条件来选副本进ISR，在高版本中不再关注副本的消息条数最大条件。</p>
+</blockquote>
+<p>为何会去掉消息条数差值参数？</p>
+<p>因为kafka一般是按batch批量发数据到leader, 如果批量条数12条，replica.lag.time.max.messages参数设置是10条，那么当一个批次消息发到kafka leader，此时，ISR中就要踢掉所有的follower，很快follower同步完所有数据后，follower又要被加入到ISR，而且要加入到zookeeper中频繁操作，所以去除掉该条件。</p>
+<h4 id="生产者数据一致性保证">生产者数据一致性保证</h4>
+<p><img alt="MQ详解-009" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-009.png"></p>
+<ul>
+<li>
+<p>LEO：（Log End offset）每个副本的最后一个offset；</p>
+</li>
+<li>
+<p>HW：（High Watermark）高水位，指的是消费者能见到的最大的 offset， ISR 队列中最小的 LEO；</p>
+</li>
+<li>
+<p>follower 故障：follower 发生故障后会被临时踢出 ISR，待该 follower 恢复后， follower 会读取本地磁盘记录的上次的 HW，并将 log 文件高于 HW 的部分截取掉，从 HW 开始向 leader 进行同步。等该 follower 的 LEO 大于等于该 Partition 的 HW，即 follower 追上 leader 之后，就可以重新加入 ISR 了。</p>
+</li>
+<li>
+<p>leader 故障：leader 发生故障之后，会从 ISR 中选出一个新的 leader，之后，为保证多个副本之间的数据一致性， 其余的 follower 会先将各自的 log 文件高于 HW 的部分截掉，然后从新的 leader同步数据；如果少于 leader 中的数据则会从 leader 中进行同步。</p>
+</li>
+</ul>
+<h4 id="生产者ack机制">生产者ack机制</h4>
+<p>对于某些不太重要的数据，对数据的可靠性要求不是很高，能够容忍数据的少量丢失，所以没必要等 ISR 中的 follower 全部接收成功。kafka为生产者提供了三种ack可靠性级别配置：</p>
+<ul>
+<li>0：producer 不等待 broker 的 ack，这一操作提供了一个最低的延迟，broker 一接收到还没有写入磁盘就已经返回，当 broker 故障时有可能丢失数据；</li>
+<li>1： producer 等待 broker 的 ack， partition 的 leader 落盘成功后返回 ack，如果在 follower同步成功之前 leader 故障，那么将会丢失数据；</li>
+<li>-1/all：producer 等待 broker 的 ack， ISR队列中 partition 的 leader 和 ISR 的follower 全部落盘成功后才返回 ack。但是如果在 follower 同步完成后，broker 发送 ack 之前， leader 发生故障，那么会造成数据重复；</li>
+</ul>
+<h4 id="exactlyonce">ExactlyOnce</h4>
+<p>将服务器的 ACK 级别设置为-1，可以保证 Producer 到 Server 之间不会丢失数据，即 At Least Once 语义，至少发送一次；相对的，将服务器 ACK 级别设置为 0，可以保证生产者每条消息只会被发送一次，即 At Most Once 语义，至多发送一次。</p>
+<p>至少发送一次可以保证数据不丢失，但是不能保证数据不重复；相对的，至多发送一次可以保证数据不重复，但是不能保证数据不丢失。 但是，对于一些非常重要的信息，比如说交易数据，下游数据消费者要求数据既不重复也不丢失，即 Exactly Once 语义，准确发送一次。</p>
+<p>在0.11 版本的 Kafka，引入了一项重大特性：幂等性。所谓的幂等性就是指生产者不论向 Server 发送多少次重复数据， Server 端都只会持久化一条。幂等性结合 At Least Once 语义，就构成了 Kafka 的 Exactly Once 语义。</p>
+<p>要启用幂等性，只需要将 Producer 的参数中 <code>enable.idempotence</code> 设置为 true 即可。</p>
+<p>Kafka的幂等性实现其实就是将原来下游需要做的去重放在了数据上游。开启幂等性的 Producer 在初始化的时候会被分配一个 PID，发往同一 Partition 的消息会附带 Sequence Number。而Broker 端会对&lt;PID, Partition, SeqNumber&gt;做缓存，当具有相同主键的消息提交时， Broker 只会持久化一条。但是 PID 重启就会变化，同时不同的 Partition 也具有不同主键，所以幂等性无法保证跨分区跨会话的 Exactly Once。</p>
+<h4 id="生产者发送消息流程">生产者发送消息流程</h4>
+<p>kafka的生产者发送消息采用的是异步发送的方式。在消息发送的过程中，涉及到了两个线程——main 线程和 Sender 线程，以及一个线程共享变量——RecordAccumulator。</p>
+<p><img alt="MQ详解-010" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-010.png"></p>
+<p>在生产者发送消息时，main线程将消息发送给 RecordAccumulator，当数据积累到 batch.size 之后，sender线程才会不断从 RecordAccumulator 中拉取消息发送到 kafka的broker；如果数据迟迟未达到 batch.size，sender 线程等待 linger.time 之后就会发送数据。</p>
+<h3 id="消费者">消费者</h3>
+<h4 id="消费者分区分配策略">消费者分区分配策略</h4>
+<p>一个消费者组中有多个消费者，一个主题有多个分区，所以必然会涉及到分区的分配问题，即确定哪个分区由哪个消费者来消费。</p>
+<p>消费分配策略：</p>
+<ul>
+<li>round-robin：会采用轮询的方式将当前所有的分区依次分配给所有的消费者；</li>
+<li>range：首先会计算每个消费者可以消费的分区个数，然后按照顺序将指定个数范围的分区分配给各个消费者；</li>
+<li>sticky：这种分区策略是最新版本中新增的一种策略，将现有的分区尽可能均衡的分配给各个消费者，存在此目的的原因在于Round-Robin和Range分配策略实际上都会导致某几个消费者承载过多的分区，从而导致消费压力不均衡；</li>
+</ul>
+<p>轮询就不必说了，就是把分区按照hash排序，然后分配。range按范围分配，先将所有的分区放到一起然后排序，按照平均分配的方式计算每个消费者会得到多少个分区，如果没有除尽，则会将多出来的分区依次计算到前面几个消费者。
+比如这里是三个分区和两个消费者，那么每个消费者至少会得到1个分区，而3除以2后还余1，那么就会将多余的部分依次算到前面几个消费者，也就是这里的1会分配给第一个消费者，</p>
+<p>如果按照Range分区方式进行分配，其本质上是依次遍历每个topic，然后将这些topic的分区按照其所订阅的消费者数量进行平均的范围分配。这种方式从计算原理上就会导致排序在前面的消费者分配到更多的分区，从而导致各个消费者的压力不均衡。</p>
+<h4 id="消费者消费数据问题">消费者消费数据问题</h4>
+<p>消费者在消费的时候，需要维护一个offset，用于记录消费的位置，当offset提交时会有两个问题：重复消费和漏消费：</p>
+<ul>
+<li>当提交的offset小于当前程序处理的最后一条消息的offset,会造成重复消费。情景：先消费，后提交offset,如果消费成功、提交失败，消费者下次获取的offset还是以前的，所以会造成重复消费。</li>
+<li>当提交的offset大于当前程序处理的最后一条消息的offset,会造成漏消费。情景：先提交offset，后消费,如果提交成功、消费失败，消费者下次获取的offset已经是新的，所以会造成漏消费。</li>
+</ul>
+<p>这里就需要注意offset的提交方式，offset默认是自动提交，当然这会造成消费的不准确。offset提交方式：</p>
+<ul>
+<li>异步提交当前offset；</li>
+<li>同步提交当前offset；</li>
+<li>同步和异步组合提交；</li>
+<li>提交指定的offset；</li>
+</ul>
+<p>建议将offset保存在数据库中，使当前业务与offset提交绑定起来，这样可以一定程度避免重复消费问题，重复消费的问题，一方面需要消息中间件来进行保证。另一方面需要自己的处理逻辑来保证消息的幂等性。</p>
+<h3 id="kafka事务">kafka事务</h3>
+<p>kafka从0.11版本开始引入了事务支持。事务可以保证kafka在<a href="/iblog/posts/detailed/java-mq/#exactlyonce">Exactly Once</a>语义的基础上，生产和消费可以跨分区和会话，要么全部成功，要么全部失败。</p>
+<ul>
+<li>生产者：为了实现跨分区跨会话的事务，需要引入一个全局唯一的事务ID，并将生产者获得的PID和事务ID绑定。这样当生产者重启后就可以通过正在进行的事务ID获得原来的PID，进而保证精准发送一次；</li>
+</ul>
+<blockquote>
+<p>为了管理 Transaction， Kafka 引入了一个新的组件 Transaction Coordinator。 Producer 就是通过和 Transaction Coordinator 交互获得 Transaction ID 对应的任务状态。 Transaction Coordinator 还负责将事务所有写入 Kafka 的一个内部 Topic，这样即使整个服务重启，由于事务状态得到保存，进行中的事务状态可以得到恢复，从而继续进行。</p>
+</blockquote>
+<ul>
+<li>消费者：对于消费者而言，事务的保证就会相对较弱，尤其时无法保证提交的信息被精确消费。这是由于消费者可以通过offset访问任意信息，而且不同的<a href="/iblog/posts/detailed/java-mq/#文件存储">Segment File</a>生命周期不同，同一事务的消息可能会出现重启后被删除的情况；</li>
+</ul>
+<h3 id="消息积压">消息积压</h3>
+<p>如果线上遇到大量消息积压,那就是线上故障了.最可能是消费者出现故障</p>
+<p>一般这个时候，只能临时紧急扩容了:</p>
+<ul>
+<li>先修复消费者的问题，确保其恢复消费速度，然后将现有消费者都停掉</li>
+<li>新建一个 topic，partition 是原来的 10 倍，临时建立好原先 10 倍的 queue 数量;</li>
+<li>然后写一个临时的分发数据的 consumer 程序，这个程序部署上去消费积压的数据，消费之后不做耗时的处理，直接均匀轮询写入临时建立好的 10 倍数量的 queue;</li>
+<li>接着临时征用 10 倍的机器来部署 consumer，每一批 consumer 消费一个临时 queue 的数据。这种做法相当于是临时将 queue 资源和 consumer 资源扩大 10 倍，以正常的 10 倍速度来消费数据;</li>
+<li>等快速消费完积压数据之后，得恢复原先部署的架构，重新用原先的 consumer 机器来消费消息;</li>
+</ul>
+<p>如果没有消费者没有出现问题,而出现了消费积压的情况可以参考以下思路:</p>
+<ul>
+<li>提高消费并行度</li>
+<li>批量方式消费</li>
+<li>跳过非重要方式消费</li>
+<li>优化消息消费业务处理过程,简化过程</li>
+</ul>
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diff --git a/blog-site/public/posts/detailed/java-netty/index.html b/blog-site/public/posts/detailed/java-netty/index.html
new file mode 100644
index 00000000..e52db582
--- /dev/null
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@@ -0,0 +1,1473 @@
+<!DOCTYPE html>
+<html lang="zh" >
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+	<title>Netty详解 ｜ 脚踏实地</title>
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+    <div class="post-password">
+        
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+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
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+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#netty">
+                    Netty
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%bf%b0">
+                    概述
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e6%a8%a1%e5%9e%8b%e6%bc%94%e5%8f%98">
+                    线程模型演变
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
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+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bc%a0%e7%bb%9f-io-%e6%a8%a1%e5%9e%8b">
+                    传统 IO 模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#reactor-%e6%a8%a1%e5%9e%8b">
+                    Reactor 模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#netty-%e6%a8%a1%e5%9e%8b">
+                    Netty 模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
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+        
+        
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+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ae%80%e5%8d%95%e4%bd%bf%e7%94%a8">
+                    简单使用
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%bb%e5%8a%a1%e9%98%9f%e5%88%97">
+                    任务队列
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%82%e6%ad%a5%e6%a8%a1%e5%9e%8b">
+                    异步模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#netty%e6%90%ad%e5%bb%bahttp%e6%9c%8d%e5%8a%a1">
+                    Netty搭建Http服务
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
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+        
+        
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+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
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+                    TCP粘包、拆包及解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
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+                        <h2 id="post_single_title">Netty详解</h2>
+                        <span id="post_page_title_date" class="date">2021.04.09</span>
+                        
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+                    <div class="post_content markdown"><h2 id="netty">Netty</h2>
+<p>参考文章：https://dongzl.github.io/netty-handbook/#/</p>
+<h3 id="概述">概述</h3>
+<blockquote>
+<p><a href="https://netty.io">Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers &amp; clients.</a></p>
+</blockquote>
+<ol>
+<li>Netty 是一个异步的、基于事件驱动的网络应用框架，用以快速开发高性能、高可靠性的网络 IO 程序。</li>
+<li>Netty 主要针对在 TCP 协议下，面向 Client 端的高并发应用，或者 Peer-to-Peer 场景下的大量数据持续传输的应用。</li>
+<li>Netty 本质是一个 NIO 框架，适用于服务器通讯相关的多种应用场景。</li>
+<li>Netty 是由 JBoss 提供的一个 Java 开源框架，现为 Github 上的独立项目。</li>
+</ol>
+<h3 id="线程模型演变">线程模型演变</h3>
+<p>目前存在的线程模型有：</p>
+<ul>
+<li>传统阻塞 I/O 服务模型</li>
+<li>Reactor 模式
+<ul>
+<li>单 Reactor 单线程</li>
+<li>单 Reactor 多线程</li>
+<li>主从 Reactor多线程</li>
+</ul>
+</li>
+</ul>
+<p>Netty 主要基于主从 Reactor 多线程模型做了一定的改进。</p>
+<h4 id="传统-io-模型">传统 IO 模型</h4>
+<p><img alt="传统IO模型" src="/iblog/posts/annex/images/essays/%E4%BC%A0%E7%BB%9FIO%E6%A8%A1%E5%9E%8B.png"></p>
+<p>采用阻塞 IO 模式获取输入的数据，每个连接都需要独立的线程完成数据的输入，业务处理，数据返回。
+当并发数很大，就会创建大量的线程，占用很大系统资源，连接创建后，如果当前线程暂时没有数据可读，该线程会阻塞在 read 操作，造成线程资源浪费。</p>
+<h4 id="reactor-模型">Reactor 模型</h4>
+<p>基于 I/O 复用模型，多个连接共用一个阻塞对象，应用程序只需要在一个阻塞对象等待，无需阻塞等待所有连接。 当某个连接有新的数据可以处理时，操作系统通知应用程序，线程从阻塞状态返回，开始进行业务处理。</p>
+<p><img alt="Reactor模式" src="/iblog/posts/annex/images/essays/Reactor%E6%A8%A1%E5%BC%8F.png"></p>
+<p>为了避免浪费可以创建一个线程池，当客户端发起请求时，通过<code>DispatcherHandler</code>进行分发请求处理到线程池，线程池中在使用具体的线程进行事件处理。 服务器端程序处理传入的多个请求,并将它们同步分派到相应的处理线程，因此 Reactor 模式也叫 Dispatcher 模式。</p>
+<p>Reactor 模式使用 IO 复用监听事件，收到事件后，分发给某个线程（进程），这点就是网络服务器高并发处理关键。</p>
+<h5 id="单-reactor-单线程">单 Reactor 单线程</h5>
+<p><img alt="单Reactor单线程" src="/iblog/posts/annex/images/essays/%E5%8D%95Reactor%E5%8D%95%E7%BA%BF%E7%A8%8B.png"></p>
+<p>步骤：</p>
+<ul>
+<li>Reactor 对象通过 Select 监控客户端请求事件，收到事件后通过 Dispatch 进行分发</li>
+<li>如果是建立连接请求事件，则由 Acceptor 通过 Accept 处理连接请求，然后创建一个 Handler 对象处理连接完成后的后续业务处理</li>
+<li>如果不是建立连接事件，则 Reactor 会分发调用连接对应的 Handler 来响应</li>
+<li>Handler 会完成 <code>Read → 业务处理 → Send</code> 的完整业务流程</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>性能问题，只有一个线程，无法完全发挥多核 CPU 的性能</li>
+<li>如果线程意外终止，或者进入死循环，会导致整个系统通信模块不可用，不能接收和处理外部消息</li>
+</ul>
+<p>优点：</p>
+<ul>
+<li>模型简单，没有多线程、进程通信、竞争的问题，全部都在一个线程中完成</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>客户端的数量有限，业务处理非常快速的情况</li>
+</ul>
+<h5 id="单-reactor-多线程">单 Reactor 多线程</h5>
+<p><img alt="单Reactor多线程" src="/iblog/posts/annex/images/essays/%E5%8D%95Reactor%E5%A4%9A%E7%BA%BF%E7%A8%8B.png"></p>
+<p>步骤：</p>
+<ul>
+<li>Reactor 对象通过对 select 监听请求事件，收到请求事件后交给 dispath 进行转发</li>
+<li>如果是建立连接请求，则通过 accept 处理连接请求，然后创建一个handler对象处理完成连接后的事件</li>
+<li>如果不是建立连接请求，则直接交给 handler 对象</li>
+<li>handler 只负责响应事件，不做具体的业务处理，通过 read 读取完后，分发给下面的 worker线程池中某个线程处理</li>
+<li>worker 线程负责处理具体业务，处理完成后会将具体的结果返回给 handler</li>
+<li>handler 线程通过send方法返回给客户端</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>多线程访问比较复杂，需要处理线程之间的竞争，资源共享</li>
+<li>Reactor 对象在处理所有事件的监听和响应都是单线程的，在高并发场景容易出现性能瓶颈</li>
+</ul>
+<p>优点：</p>
+<ul>
+<li>可以充分利用CPU资源</li>
+</ul>
+<h5 id="主从-reactor-多线程">主从 Reactor 多线程</h5>
+<p><img alt="主从Reactor线程" src="/iblog/posts/annex/images/essays/%E4%B8%BB%E4%BB%8EReactor%E7%BA%BF%E7%A8%8B.png"></p>
+<p>Reactor 主线程可以对应多个 Reactor 子线程，即 MainRecator 可以关联多个 SubReactor，从而解决了Reactor 在单线程中运行，高并发场景下容易成为性能瓶颈。
+步骤：</p>
+<ul>
+<li>Reactor 主线程 MainReactor 对象通过 select 监听连接事件，收到事件后，通过 Acceptor 处理连接事件</li>
+<li>当 Acceptor 处理连接事件后，MainReactor 将连接分配给 SubReactor</li>
+<li>SubReactor 将连接加入到连接队列进行监听，并创建 handler 进行各种事件处理</li>
+<li>当有新事件发生时，SubReactor 就会调用对应的 handler 处理</li>
+<li>handler 只负责响应事件，不做具体的业务处理，通过 read 读取完后，分发给下面的 worker线程池中某个线程处理</li>
+<li>worker 线程负责处理具体业务，处理完成后会将具体的结果返回给 handler</li>
+<li>handler 线程通过send方法返回给客户端</li>
+</ul>
+<p>优点：</p>
+<ul>
+<li>父线程与子线程的数据交互简单，Reactor 主线程只需要把新连接传给子线程，子线程无需返回数据</li>
+<li>父线程与子线程的数据交互简单职责明确，父线程只需要接收新连接，子线程完成后续的业务处理</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>编程复杂度较高</li>
+</ul>
+<p>这种模型在许多项目中广泛使用，包括 Nginx 主从 Reactor 多进程模型，Memcached 主从多线程，Netty 主从多线程模型的支持。</p>
+<h4 id="netty-模型">Netty 模型</h4>
+<p><img alt="Netty模型" src="/iblog/posts/annex/images/essays/Netty%E6%A8%A1%E5%9E%8B.png"></p>
+<p><img alt="netty结构" src="/iblog/posts/annex/images/essays/netty%E7%BB%93%E6%9E%84.png"></p>
+<ul>
+<li>Netty 抽象出两组线程池 <code>BossGroup</code> 专门负责接收客户端的连接，<code>WorkerGroup</code> 专门负责网络的读写；<code>BossGroup</code> 和 <code>WorkerGroup</code> 类型都是 <code>NioEventLoopGroup</code></li>
+<li><code>NioEventLoopGroup</code> 相当于一个事件循环组，这个组中含有多个事件循环，每一个事件循环是 <code>NioEventLoop</code>，每个 <code>NioEventLoop</code> 都有一个 <code>Selector</code>，用于监听绑定在其上的 <code>socket</code> 的网络通讯</li>
+<li><code>NioEventLoopGroup</code> 可指定多个 <code>NioEventLoop</code></li>
+<li>每个 <code>BossNioEventLoop</code> 循环执行的步骤
+<ul>
+<li>轮询 accept 事件</li>
+<li>处理 <code>accept</code> 事件，与 client 建立连接，生成 <code>NioSocketChannel</code>，并将其注册到某个 <code>workerNioEventLoop</code> 上的 <code>Selector</code></li>
+<li>处理任务队列的任务，即 <code>runAllTasks</code></li>
+</ul>
+</li>
+<li>每个 <code>WorkerNioEventLoop</code> 循环执行的步骤
+<ul>
+<li>轮询 <code>read，write</code> 事件</li>
+<li>处理 I/O 事件，即 <code>read，write</code> 事件，在对应 <code>NioSocketChannel</code> 处理</li>
+<li>处理任务队列的任务，即 <code>runAllTasks</code></li>
+</ul>
+</li>
+<li>每个 <code>WorkerNioEventLoop</code> 处理业务时，会使用 <code>pipeline</code>（管道），<code>pipeline</code> 中包含了 <code>channel</code>(通道)，即通过 <code>pipeline</code> 可以获取到对应通道，管道中维护了很多的处理器</li>
+</ul>
+<h3 id="简单使用">简单使用</h3>
+<p>1.<a href="https://netty.io/downloads.html">导入依赖</a></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">&lt;dependency&gt;
+</span></span><span class="line"><span class="cl">    &lt;groupId&gt;io.netty&lt;/groupId&gt;
+</span></span><span class="line"><span class="cl">    &lt;artifactId&gt;netty-all&lt;/artifactId&gt;
+</span></span><span class="line"><span class="cl">    &lt;version&gt;4.1.36.Final&lt;/version&gt;
+</span></span><span class="line"><span class="cl">&lt;/dependency&gt;
+</span></span><span class="line"><span class="cl">&lt;dependency&gt;
+</span></span><span class="line"><span class="cl">    &lt;groupId&gt;org.projectlombok&lt;/groupId&gt;
+</span></span><span class="line"><span class="cl">    &lt;artifactId&gt;lombok&lt;/artifactId&gt;
+</span></span><span class="line"><span class="cl">&lt;/dependency&gt;
+</span></span></code></pre></div><p>2.服务器端代码演示</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">/**
+</span></span><span class="line"><span class="cl"> * netty 服务端测试
+</span></span><span class="line"><span class="cl"> */
+</span></span><span class="line"><span class="cl">public class MainTestServer {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        // 启动器， 负责组装netty组件 启动服务器
+</span></span><span class="line"><span class="cl">        new ServerBootstrap()
+</span></span><span class="line"><span class="cl">                // BossEventLoop WorkEventLoop 每个 EventLoop 就是 一个选择器 + 一个线程
+</span></span><span class="line"><span class="cl">                .group(new NioEventLoopGroup())
+</span></span><span class="line"><span class="cl">                // 选择服务器 ServerSocketChannel 具体实现
+</span></span><span class="line"><span class="cl">                .channel(NioServerSocketChannel.class)
+</span></span><span class="line"><span class="cl">                // 决定了 workEventLoop 能做那些操作
+</span></span><span class="line"><span class="cl">                .childHandler(
+</span></span><span class="line"><span class="cl">                        // 建立连接后会被调用； 作用： 初始化 + 添加其他的 handler
+</span></span><span class="line"><span class="cl">                        new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">                    // 当客户端请求发过来时 才会调用
+</span></span><span class="line"><span class="cl">                    @Override 
+</span></span><span class="line"><span class="cl">                    protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(new StringDecoder());
+</span></span><span class="line"><span class="cl">                        // 自定义handler 
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(new ChannelInboundHandlerAdapter() {
+</span></span><span class="line"><span class="cl">                            @Override
+</span></span><span class="line"><span class="cl">                            public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
+</span></span><span class="line"><span class="cl">                                System.out.println(&#34;服务器端接收数据：&#34; + msg);
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">                        });
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                })
+</span></span><span class="line"><span class="cl">                // 绑定监听端口
+</span></span><span class="line"><span class="cl">                .bind(8090);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>3.客户端代码演示</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">/**
+</span></span><span class="line"><span class="cl"> * netty 客户端测试
+</span></span><span class="line"><span class="cl"> */
+</span></span><span class="line"><span class="cl">public class MainTestClient {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) throws InterruptedException {
+</span></span><span class="line"><span class="cl">        new Bootstrap()
+</span></span><span class="line"><span class="cl">                .group(new NioEventLoopGroup())
+</span></span><span class="line"><span class="cl">                .channel(NioSocketChannel.class)
+</span></span><span class="line"><span class="cl">                .handler(new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">                    // 初始化 在与服务器建立链接的时候 调用
+</span></span><span class="line"><span class="cl">                    @Override
+</span></span><span class="line"><span class="cl">                    protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                        // 添加编码器 只有当向服务端发送请求数据时 才会执行
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(new StringEncoder());
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                })
+</span></span><span class="line"><span class="cl">                .connect(new InetSocketAddress(&#34;127.0.0.1&#34;, 8090))
+</span></span><span class="line"><span class="cl">                //阻塞方法，直到与服务器端连接建立
+</span></span><span class="line"><span class="cl">                .sync()
+</span></span><span class="line"><span class="cl">                .channel()
+</span></span><span class="line"><span class="cl">                // 向服务器端发送数据
+</span></span><span class="line"><span class="cl">                .writeAndFlush(&#34;hello word&#34;);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="任务队列">任务队列</h3>
+<ul>
+<li>用户程序自定义的普通任务</li>
+<li>用户自定义定时任务</li>
+<li>非当前 Reactor 线程调用 Channel 的各种方法 例如在推送系统的业务线程里面，根据用户的标识，找到对应的 Channel 引用，然后调用 Write 类方法向该用户推送消息，就会进入到这种场景。
+最终的 Write 会提交到任务队列中后被异步消费</li>
+</ul>
+<p>客户端</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">/**
+</span></span><span class="line"><span class="cl"> * netty 客户端测试
+</span></span><span class="line"><span class="cl"> */
+</span></span><span class="line"><span class="cl">public class MainTestClient {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) throws InterruptedException {
+</span></span><span class="line"><span class="cl">        new Bootstrap()
+</span></span><span class="line"><span class="cl">                .group(new NioEventLoopGroup())
+</span></span><span class="line"><span class="cl">                .channel(NioSocketChannel.class)
+</span></span><span class="line"><span class="cl">                .handler(new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                    // 初始化 在与服务器建立链接的时候 调用
+</span></span><span class="line"><span class="cl">                    @Override
+</span></span><span class="line"><span class="cl">                    protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                        // 添加编码器 只有当向服务端发送请求数据时 才会执行
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(&#34;decoder&#34;, new StringDecoder());
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(&#34;encoder&#34;, new StringEncoder());
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(new ChannelInboundHandlerAdapter(){
+</span></span><span class="line"><span class="cl">                            @Override
+</span></span><span class="line"><span class="cl">                            public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
+</span></span><span class="line"><span class="cl">                                System.out.println(&#34;服务端响应数据：&#34; + msg);
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                            @Override
+</span></span><span class="line"><span class="cl">                            public void channelActive(ChannelHandlerContext ctx) throws Exception {
+</span></span><span class="line"><span class="cl">                                System.out.println(&#34;客户端Active .....&#34;);
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                            /**
+</span></span><span class="line"><span class="cl">                             * 客户端异常时触发
+</span></span><span class="line"><span class="cl">                             */
+</span></span><span class="line"><span class="cl">                            @Override
+</span></span><span class="line"><span class="cl">                            public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
+</span></span><span class="line"><span class="cl">                                cause.printStackTrace();
+</span></span><span class="line"><span class="cl">                                ctx.close();
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                        });
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                })
+</span></span><span class="line"><span class="cl">                .connect(new InetSocketAddress(&#34;127.0.0.1&#34;, 8090))
+</span></span><span class="line"><span class="cl">                //阻塞方法，直到与服务器端连接建立
+</span></span><span class="line"><span class="cl">                .sync()
+</span></span><span class="line"><span class="cl">                .channel()
+</span></span><span class="line"><span class="cl">                // 向服务器端发送数据
+</span></span><span class="line"><span class="cl">                .writeAndFlush(&#34;hello word&#34;);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>服务端</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">/**
+</span></span><span class="line"><span class="cl"> * netty 服务端测试
+</span></span><span class="line"><span class="cl"> */
+</span></span><span class="line"><span class="cl">public class MainTestServer {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        //new 一个主线程组
+</span></span><span class="line"><span class="cl">        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
+</span></span><span class="line"><span class="cl">        //new 一个工作线程组
+</span></span><span class="line"><span class="cl">        EventLoopGroup workGroup = new NioEventLoopGroup(200);
+</span></span><span class="line"><span class="cl">        // 启动器， 负责组装netty组件 启动服务器
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            ServerBootstrap serverBootstrap = new ServerBootstrap()
+</span></span><span class="line"><span class="cl">                    // BossEventLoop WorkEventLoop 每个 EventLoop 就是 一个选择器 + 一个线程
+</span></span><span class="line"><span class="cl">                    .group(bossGroup, workGroup)
+</span></span><span class="line"><span class="cl">                    // 选择服务器 ServerSocketChannel 具体实现
+</span></span><span class="line"><span class="cl">                    .channel(NioServerSocketChannel.class)
+</span></span><span class="line"><span class="cl">                    //设置队列大小
+</span></span><span class="line"><span class="cl">                    .option(ChannelOption.SO_BACKLOG, 1024)
+</span></span><span class="line"><span class="cl">                    // 两小时内没有数据的通信时,TCP会自动发送一个活动探测数据报文
+</span></span><span class="line"><span class="cl">                    .childOption(ChannelOption.SO_KEEPALIVE, true)
+</span></span><span class="line"><span class="cl">                    // 决定了 workEventLoop 能做那些操作
+</span></span><span class="line"><span class="cl">                    .childHandler(
+</span></span><span class="line"><span class="cl">                            // 建立连接后会被调用； 作用： 初始化 + 添加其他的 handler
+</span></span><span class="line"><span class="cl">                            new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">                                // 当客户端请求发过来时 才会调用
+</span></span><span class="line"><span class="cl">                                @Override
+</span></span><span class="line"><span class="cl">                                protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(&#34;decoder&#34;, new StringDecoder(CharsetUtil.UTF_8));
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(&#34;encoder&#34;, new StringEncoder(CharsetUtil.UTF_8));
+</span></span><span class="line"><span class="cl">                                    // 自定义handler
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(new ChannelInboundHandlerAdapter() {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                        /**
+</span></span><span class="line"><span class="cl">                                         * 客户端连接会触发
+</span></span><span class="line"><span class="cl">                                         */
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
+</span></span><span class="line"><span class="cl">                                            System.out.println(&#34;服务端 Active......&#34;);
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                        /**
+</span></span><span class="line"><span class="cl">                                         * 客户端发消息会触发
+</span></span><span class="line"><span class="cl">                                         */
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
+</span></span><span class="line"><span class="cl">                                            System.out.println(&#34;服务器收到消息: &#34; + msg.toString());
+</span></span><span class="line"><span class="cl">                                            // 比如这里我们有一个非常耗时长的业务-&gt; 应该一步执行 -&gt; 提交该对应的channel
+</span></span><span class="line"><span class="cl">                                            // 将任务放在 taskQueue 中
+</span></span><span class="line"><span class="cl">                                            ctx.channel().eventLoop().execute(() -&gt; {
+</span></span><span class="line"><span class="cl">                                                try {
+</span></span><span class="line"><span class="cl">                                                    Thread.sleep(10 * 1000);
+</span></span><span class="line"><span class="cl">                                                    ctx.writeAndFlush(&#34;业务1处理完成&#34;);
+</span></span><span class="line"><span class="cl">                                                } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">                                                    e.printStackTrace();
+</span></span><span class="line"><span class="cl">                                                }
+</span></span><span class="line"><span class="cl">                                            });
+</span></span><span class="line"><span class="cl">                                            // 放在TaskQueue 中的任务是由一个线程来进行处理的 所以执行完上一个任务才会执行下一个任务 时间是累加的
+</span></span><span class="line"><span class="cl">                                            ctx.channel().eventLoop().execute(() -&gt; {
+</span></span><span class="line"><span class="cl">                                                try {
+</span></span><span class="line"><span class="cl">                                                    Thread.sleep(20 * 1000);
+</span></span><span class="line"><span class="cl">                                                    ctx.writeAndFlush(&#34;业务2处理完成&#34;);
+</span></span><span class="line"><span class="cl">                                                } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">                                                    e.printStackTrace();
+</span></span><span class="line"><span class="cl">                                                }
+</span></span><span class="line"><span class="cl">                                            });
+</span></span><span class="line"><span class="cl">                                             // 用户自定义定时任务 -》 该任务是提交到 scheduleTaskQueue中
+</span></span><span class="line"><span class="cl">                                        
+</span></span><span class="line"><span class="cl">                                            ctx.channel().eventLoop().schedule(new Runnable() {
+</span></span><span class="line"><span class="cl">                                                @Override
+</span></span><span class="line"><span class="cl">                                                public void run() {
+</span></span><span class="line"><span class="cl">                                    
+</span></span><span class="line"><span class="cl">                                                    try {
+</span></span><span class="line"><span class="cl">                                                        Thread.sleep(5 * 1000);
+</span></span><span class="line"><span class="cl">                                                        ctx.writeAndFlush(Unpooled.copiedBuffer(&#34;hello, 客户端~(&gt;^ω^&lt;)喵4&#34;, CharsetUtil.UTF_8));
+</span></span><span class="line"><span class="cl">                                                        System.out.println(&#34;channel code=&#34; + ctx.channel().hashCode());
+</span></span><span class="line"><span class="cl">                                                    } catch (Exception ex) {
+</span></span><span class="line"><span class="cl">                                                        System.out.println(&#34;发生异常&#34; + ex.getMessage());
+</span></span><span class="line"><span class="cl">                                                    }
+</span></span><span class="line"><span class="cl">                                                }
+</span></span><span class="line"><span class="cl">                                            }, 5, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                        /**
+</span></span><span class="line"><span class="cl">                                         * 给客户端发送消息
+</span></span><span class="line"><span class="cl">                                         */
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
+</span></span><span class="line"><span class="cl">                                            ctx.writeAndFlush(&#34;over&#34;);
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                        /**
+</span></span><span class="line"><span class="cl">                                         * 发生异常触发
+</span></span><span class="line"><span class="cl">                                         */
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
+</span></span><span class="line"><span class="cl">                                            cause.printStackTrace();
+</span></span><span class="line"><span class="cl">                                            ctx.close();
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                    });
+</span></span><span class="line"><span class="cl">                                }
+</span></span><span class="line"><span class="cl">                            });
+</span></span><span class="line"><span class="cl">                    // 绑定监听端口
+</span></span><span class="line"><span class="cl">            ChannelFuture future = serverBootstrap.bind(8090).sync();
+</span></span><span class="line"><span class="cl">            // 对关闭通道进行监听
+</span></span><span class="line"><span class="cl">            future.channel().closeFuture().sync();
+</span></span><span class="line"><span class="cl">        } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        } finally {
+</span></span><span class="line"><span class="cl">            //关闭主线程组
+</span></span><span class="line"><span class="cl">            bossGroup.shutdownGracefully();
+</span></span><span class="line"><span class="cl">            //关闭工作线程组
+</span></span><span class="line"><span class="cl">            workGroup.shutdownGracefully();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="异步模型">异步模型</h3>
+<p>异步的概念和同步相对。当一个异步过程调用发出后，调用者不能立刻得到结果。实际处理这个调用的组件在完成后，通过状态、通知和回调来通知调用者。</p>
+<p><code>Netty</code> 中的 I/O 操作是异步的，包括 <code>Bind、Write、Connect</code> 等操作会简单的返回一个 <code>ChannelFuture</code>。 调用者并不能立刻获得结果，而是通过 <code>Future-Listener</code> 机制，用户可以方便的主动获取或者通过通知机制获得 IO 操作结果。</p>
+<p>当 <code>Future</code> 对象刚刚创建时，处于非完成状态，调用者可以通过返回的 <code>ChannelFuture</code> 来获取操作执行的状态，注册监听函数来执行完成后的操作。</p>
+<p>常见有如下操作：</p>
+<ul>
+<li>通过 <code>isDone</code> 方法来判断当前操作是否完成；</li>
+<li>通过 <code>isSuccess</code> 方法来判断已完成的当前操作是否成功；</li>
+<li>通过 <code>getCause</code> 方法来获取已完成的当前操作失败的原因；</li>
+<li>通过 <code>isCancelled</code> 方法来判断已完成的当前操作是否被取消；</li>
+<li>通过 <code>addListener</code> 方法来注册监听器，当操作已完成（isDone方法返回完成），将会通知指定的监听器；如果 <code>Future</code> 对象已完成，则通知指定的监听器</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">//绑定一个端口并且同步,生成了一个ChannelFuture对象
+</span></span><span class="line"><span class="cl">//启动服务器(并绑定端口)
+</span></span><span class="line"><span class="cl">ChannelFuture cf = bootstrap.bind(6668).sync();
+</span></span><span class="line"><span class="cl">//给cf注册监听器，监控我们关心的事件
+</span></span><span class="line"><span class="cl">cf.addListener(new ChannelFutureListener() {
+</span></span><span class="line"><span class="cl">   @Override
+</span></span><span class="line"><span class="cl">   public void operationComplete (ChannelFuture future) throws Exception {
+</span></span><span class="line"><span class="cl">      if (cf.isSuccess()) {
+</span></span><span class="line"><span class="cl">         System.out.println(&#34;监听端口6668成功&#34;);
+</span></span><span class="line"><span class="cl">      } else {
+</span></span><span class="line"><span class="cl">         System.out.println(&#34;监听端口6668失败&#34;);
+</span></span><span class="line"><span class="cl">      }
+</span></span><span class="line"><span class="cl">   }
+</span></span><span class="line"><span class="cl">});
+</span></span></code></pre></div><h3 id="netty搭建http服务">Netty搭建Http服务</h3>
+<p>服务端</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MainTestServer {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        //new 一个主线程组
+</span></span><span class="line"><span class="cl">        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
+</span></span><span class="line"><span class="cl">        //new 一个工作线程组
+</span></span><span class="line"><span class="cl">        EventLoopGroup workGroup = new NioEventLoopGroup(200);
+</span></span><span class="line"><span class="cl">        // 启动器， 负责组装netty组件 启动服务器
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            ServerBootstrap serverBootstrap = new ServerBootstrap()
+</span></span><span class="line"><span class="cl">                    // BossEventLoop WorkEventLoop 每个 EventLoop 就是 一个选择器 + 一个线程
+</span></span><span class="line"><span class="cl">                    .group(bossGroup, workGroup)
+</span></span><span class="line"><span class="cl">                    // 选择服务器 ServerSocketChannel 具体实现
+</span></span><span class="line"><span class="cl">                    .channel(NioServerSocketChannel.class)
+</span></span><span class="line"><span class="cl">                    //设置队列大小
+</span></span><span class="line"><span class="cl">                    .option(ChannelOption.SO_BACKLOG, 1024)
+</span></span><span class="line"><span class="cl">                    // 两小时内没有数据的通信时,TCP会自动发送一个活动探测数据报文
+</span></span><span class="line"><span class="cl">                    .childOption(ChannelOption.SO_KEEPALIVE, true)
+</span></span><span class="line"><span class="cl">                    // 决定了 workEventLoop 能做那些操作
+</span></span><span class="line"><span class="cl">                    .childHandler(
+</span></span><span class="line"><span class="cl">                            // 建立连接后会被调用； 作用： 初始化 + 添加其他的 handler
+</span></span><span class="line"><span class="cl">                            new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">                                // 当客户端请求发过来时 才会调用
+</span></span><span class="line"><span class="cl">                                @Override
+</span></span><span class="line"><span class="cl">                                protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(&#34;MyHttpServerCodec&#34;, new HttpServerCodec());
+</span></span><span class="line"><span class="cl">                                    // 自定义handler
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(new SimpleChannelInboundHandler&lt;HttpObject&gt;() {
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {
+</span></span><span class="line"><span class="cl">                                            System.out.println(&#34;对应的channel=&#34; + ctx.channel() + &#34; pipeline=&#34; + ctx.pipeline() + &#34; 通过pipeline获取channel&#34; + ctx.pipeline().channel());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                            System.out.println(&#34;当前ctx的handler=&#34; + ctx.handler());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                            //判断 msg 是不是 httprequest请求
+</span></span><span class="line"><span class="cl">                                            if (msg instanceof HttpRequest) {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                System.out.println(&#34;ctx 类型=&#34; + ctx.getClass());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                System.out.println(&#34;pipeline hashcode&#34; + ctx.pipeline().hashCode() + &#34; TestHttpServerHandler hash=&#34; + this.hashCode());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                System.out.println(&#34;msg 类型=&#34; + msg.getClass());
+</span></span><span class="line"><span class="cl">                                                System.out.println(&#34;客户端地址&#34; + ctx.channel().remoteAddress());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                //获取到
+</span></span><span class="line"><span class="cl">                                                HttpRequest httpRequest = (HttpRequest) msg;
+</span></span><span class="line"><span class="cl">                                                //获取uri, 过滤指定的资源
+</span></span><span class="line"><span class="cl">                                                URI uri = new URI(httpRequest.uri());
+</span></span><span class="line"><span class="cl">                                                if (&#34;/favicon.ico&#34;.equals(uri.getPath())) {
+</span></span><span class="line"><span class="cl">                                                    System.out.println(&#34;请求了 favicon.ico, 不做响应&#34;);
+</span></span><span class="line"><span class="cl">                                                    return;
+</span></span><span class="line"><span class="cl">                                                }
+</span></span><span class="line"><span class="cl">                                                //回复信息给浏览器 [http协议]
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                ByteBuf content = Unpooled.copiedBuffer(&#34;hello, 我是服务器&#34;, CharsetUtil.UTF_8);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                //构造一个http的相应，即 httpresponse
+</span></span><span class="line"><span class="cl">                                                FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, content);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                response.headers().set(HttpHeaderNames.CONTENT_TYPE, &#34;text/plain&#34;);
+</span></span><span class="line"><span class="cl">                                                response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.readableBytes());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                //将构建好 response返回
+</span></span><span class="line"><span class="cl">                                                ctx.writeAndFlush(response);
+</span></span><span class="line"><span class="cl">                                            }
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">                                    });
+</span></span><span class="line"><span class="cl">                                }
+</span></span><span class="line"><span class="cl">                            });
+</span></span><span class="line"><span class="cl">                    // 绑定监听端口
+</span></span><span class="line"><span class="cl">            ChannelFuture future = serverBootstrap.bind(8090).sync();
+</span></span><span class="line"><span class="cl">            future.addListener( future1 -&gt; {
+</span></span><span class="line"><span class="cl">                if (future.isSuccess()) {
+</span></span><span class="line"><span class="cl">                    System.out.println(&#34;监听端口8090成功&#34;);
+</span></span><span class="line"><span class="cl">                }else{
+</span></span><span class="line"><span class="cl">                    System.out.println(&#34;监听端口8090失败&#34;);
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            });
+</span></span><span class="line"><span class="cl">            // 对关闭通道进行监听
+</span></span><span class="line"><span class="cl">            future.channel().closeFuture().sync();
+</span></span><span class="line"><span class="cl">        } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        } finally {
+</span></span><span class="line"><span class="cl">            //关闭主线程组
+</span></span><span class="line"><span class="cl">            bossGroup.shutdownGracefully();
+</span></span><span class="line"><span class="cl">            //关闭工作线程组
+</span></span><span class="line"><span class="cl">            workGroup.shutdownGracefully();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="tcp粘包拆包及解决方案">TCP粘包、拆包及解决方案</h3>
+<p>TCP 是面向连接的，面向流的，提供高可靠性服务。收发两端（客户端和服务器端）都要有一一成对的 socket，因此，发送端为了将多个发给接收端的包，更有效的发给对方，使用了优化方法（Nagle 算法），将多次间隔较小且数据量小的数据，合并成一个大的数据块，然后进行封包。这样做虽然提高了效率，但是接收端就难于分辨出完整的数据包了，由于 TCP 无消息保护边界,需要在接收端处理消息边界问题，也就是我们所说的粘包、拆包问题。</p>
+<p>拆包和粘包是在socket编程中经常出现的情况，在socket通讯过程中，如果通讯的一端一次性连续发送多条数据包，tcp协议会将多个数据包打包成一个tcp报文发送出去，这就是所谓的粘包。而如果通讯的一端发送的数据包超过一次tcp报文所能传输的最大值时，就会将一个数据包拆成多个最大tcp长度的tcp报文分开传输，这就叫做拆包。</p>
+<p>对于粘包的情况，要对粘在一起的包进行拆包。对于拆包的情况，要对被拆开的包进行粘包，即将一个被拆开的完整应用包再组合成一个完整包。比较通用的做法就是每次发送一个应用数据包前在前面加上四个字节的包长度值，指明这个应用包的真实长度。</p>
+<p>使用netty解决拆包、粘包问题代码示例：</p>
+<p>客户端代码</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="err">@</span><span class="n">SpringBootApplication</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyClientApplication</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="ne">String</span><span class="p">[]</span> <span class="n">args</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">SpringApplication</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">NettyClientApplication</span><span class="o">.</span><span class="k">class</span><span class="p">,</span> <span class="n">args</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Component</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">StartNetty</span> <span class="n">implements</span> <span class="n">CommandLineRunner</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="n">final</span> <span class="n">NettyClient</span> <span class="n">nettyClient</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">StartNetty</span><span class="p">(</span><span class="n">NettyClient</span> <span class="n">nettyClient</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">nettyClient</span> <span class="o">=</span> <span class="n">nettyClient</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">run</span><span class="p">(</span><span class="ne">String</span><span class="o">...</span> <span class="n">args</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;启动netty客户端 ...&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">nettyClient</span><span class="o">.</span><span class="n">start</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Component</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyClient</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="n">Netty客户端启动</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">start</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">EventLoopGroup</span> <span class="n">group</span> <span class="o">=</span> <span class="n">new</span> <span class="n">NioEventLoopGroup</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Bootstrap</span> <span class="n">bootstrap</span> <span class="o">=</span> <span class="n">new</span> <span class="n">Bootstrap</span><span class="p">()</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">group</span><span class="p">(</span><span class="n">group</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">//</span><span class="err">该参数的作用就是禁止使用</span><span class="n">Nagle算法</span><span class="err">，使用于小数据即时传输</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">option</span><span class="p">(</span><span class="n">ChannelOption</span><span class="o">.</span><span class="n">TCP_NODELAY</span><span class="p">,</span> <span class="bp">true</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">channel</span><span class="p">(</span><span class="n">NioSocketChannel</span><span class="o">.</span><span class="k">class</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">handler</span><span class="p">(</span><span class="n">new</span> <span class="n">NettyClientInitializer</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">try</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">ChannelFuture</span> <span class="n">future</span> <span class="o">=</span> <span class="n">bootstrap</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">&#34;127.0.0.1&#34;</span><span class="p">,</span> <span class="mi">9000</span><span class="p">)</span><span class="o">.</span><span class="n">sync</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">            <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;客户端成功....&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span><span class="err">发送消息</span>
+</span></span><span class="line"><span class="cl">            <span class="n">future</span><span class="o">.</span><span class="n">channel</span><span class="p">()</span><span class="o">.</span><span class="n">writeAndFlush</span><span class="p">(</span><span class="s2">&#34;客户端请求数据&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span> <span class="err">等待连接被关闭</span>
+</span></span><span class="line"><span class="cl">            <span class="n">future</span><span class="o">.</span><span class="n">channel</span><span class="p">()</span><span class="o">.</span><span class="n">closeFuture</span><span class="p">()</span><span class="o">.</span><span class="n">sync</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="n">catch</span> <span class="p">(</span><span class="n">InterruptedException</span> <span class="n">e</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">e</span><span class="o">.</span><span class="n">printStackTrace</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="n">finally</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">group</span><span class="o">.</span><span class="n">shutdownGracefully</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyClientInitializer</span> <span class="k">extends</span> <span class="n">ChannelInitializer</span><span class="o">&lt;</span><span class="n">SocketChannel</span><span class="o">&gt;</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">initChannel</span><span class="p">(</span><span class="n">SocketChannel</span> <span class="n">socketChannel</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="s2">&#34;decoder&#34;</span><span class="p">,</span> <span class="n">new</span> <span class="n">MyMessageDecoder</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="s2">&#34;encoder&#34;</span><span class="p">,</span> <span class="n">new</span> <span class="n">MyMessageEncoder</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="n">new</span> <span class="n">NettyClientHandler</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyClientHandler</span> <span class="k">extends</span> <span class="n">ChannelInboundHandlerAdapter</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelActive</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;客户端Active .....&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span> <span class="err">模拟</span><span class="n">tcp粘包</span>
+</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="p">(</span><span class="ne">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="mi">5</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="ne">String</span> <span class="n">mes</span> <span class="o">=</span> <span class="s2">&#34;今天天气冷，吃火锅&#34;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span> <span class="o">=</span> <span class="n">mes</span><span class="o">.</span><span class="n">getBytes</span><span class="p">(</span><span class="n">Charset</span><span class="o">.</span><span class="n">forName</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">            <span class="ne">int</span> <span class="n">length</span> <span class="o">=</span> <span class="n">mes</span><span class="o">.</span><span class="n">getBytes</span><span class="p">(</span><span class="n">Charset</span><span class="o">.</span><span class="n">forName</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">))</span><span class="o">.</span><span class="n">length</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="o">//</span>  <span class="err">解决</span><span class="n">tcp粘包问题</span>
+</span></span><span class="line"><span class="cl">            <span class="n">MessageProtocol</span> <span class="n">messageProtocol</span> <span class="o">=</span> <span class="n">new</span> <span class="n">MessageProtocol</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">            <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setLen</span><span class="p">(</span><span class="n">length</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setContent</span><span class="p">(</span><span class="n">content</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="n">ctx</span><span class="o">.</span><span class="n">writeAndFlush</span><span class="p">(</span><span class="n">messageProtocol</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">收到服务端的消息</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelRead</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="ne">Object</span> <span class="n">msg</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;客户端收到消息: {}&#34;</span><span class="p">,</span> <span class="n">msg</span><span class="o">.</span><span class="n">toString</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">MessageProtocol</span> <span class="n">mp</span> <span class="o">=</span> <span class="p">(</span><span class="n">MessageProtocol</span><span class="p">)</span><span class="n">msg</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">int</span> <span class="n">len</span> <span class="o">=</span> <span class="n">mp</span><span class="o">.</span><span class="n">getLen</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span> <span class="o">=</span> <span class="n">mp</span><span class="o">.</span><span class="n">getContent</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;客户端接收到消息如下&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;长度=&#34;</span> <span class="o">+</span> <span class="n">len</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;内容=&#34;</span> <span class="o">+</span> <span class="n">new</span> <span class="ne">String</span><span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">StandardCharsets</span><span class="o">.</span><span class="n">UTF_8</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">客户端异常时触发</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">exceptionCaught</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">Throwable</span> <span class="n">cause</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">cause</span><span class="o">.</span><span class="n">printStackTrace</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ctx</span><span class="o">.</span><span class="n">close</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>服务端代码</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="err">@</span><span class="n">SpringBootApplication</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyServerApplication</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="ne">String</span><span class="p">[]</span> <span class="n">args</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">SpringApplication</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">NettyServerApplication</span><span class="o">.</span><span class="k">class</span><span class="p">,</span> <span class="n">args</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Component</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">StartNetty</span> <span class="n">implements</span> <span class="n">CommandLineRunner</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="n">final</span> <span class="n">NettyServer</span> <span class="n">nettyServer</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">StartNetty</span><span class="p">(</span><span class="n">NettyServer</span> <span class="n">nettyServer</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">nettyServer</span> <span class="o">=</span> <span class="n">nettyServer</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">启动</span><span class="n">netty</span> <span class="err">让</span><span class="n">netty随着项目一起启动</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">run</span><span class="p">(</span><span class="ne">String</span><span class="o">...</span> <span class="n">args</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;netty 服务端启动 ...&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">nettyServer</span><span class="o">.</span><span class="n">start</span><span class="p">(</span><span class="n">new</span> <span class="n">InetSocketAddress</span><span class="p">(</span><span class="s2">&#34;127.0.0.1&#34;</span><span class="p">,</span> <span class="mi">9000</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Component</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyServer</span>  <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="n">Netty服务启动</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">start</span><span class="p">(</span><span class="n">InetSocketAddress</span> <span class="n">socketAddress</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="n">new</span> <span class="err">一个主线程组</span>
+</span></span><span class="line"><span class="cl">        <span class="n">EventLoopGroup</span> <span class="n">bossGroup</span> <span class="o">=</span> <span class="n">new</span> <span class="n">NioEventLoopGroup</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="n">new</span> <span class="err">一个工作线程组</span>
+</span></span><span class="line"><span class="cl">        <span class="n">EventLoopGroup</span> <span class="n">workGroup</span> <span class="o">=</span> <span class="n">new</span> <span class="n">NioEventLoopGroup</span><span class="p">(</span><span class="mi">200</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">ServerBootstrap</span> <span class="n">bootstrap</span> <span class="o">=</span> <span class="n">new</span> <span class="n">ServerBootstrap</span><span class="p">()</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">group</span><span class="p">(</span><span class="n">bossGroup</span><span class="p">,</span> <span class="n">workGroup</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">channel</span><span class="p">(</span><span class="n">NioServerSocketChannel</span><span class="o">.</span><span class="k">class</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">childHandler</span><span class="p">(</span><span class="n">new</span> <span class="n">ServerChannelInitializer</span><span class="p">())</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">localAddress</span><span class="p">(</span><span class="n">socketAddress</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">//</span><span class="err">设置队列大小</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">option</span><span class="p">(</span><span class="n">ChannelOption</span><span class="o">.</span><span class="n">SO_BACKLOG</span><span class="p">,</span> <span class="mi">1024</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">//</span> <span class="err">两小时内没有数据的通信时</span><span class="p">,</span><span class="n">TCP会自动发送一个活动探测数据报文</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">childOption</span><span class="p">(</span><span class="n">ChannelOption</span><span class="o">.</span><span class="n">SO_KEEPALIVE</span><span class="p">,</span> <span class="bp">true</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">绑定端口</span><span class="p">,</span><span class="err">开始接收进来的连接</span>
+</span></span><span class="line"><span class="cl">        <span class="n">try</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span> <span class="err">绑定端口</span> <span class="err">生成一个</span><span class="n">ChannelFuture</span> <span class="err">对象</span> <span class="err">启动服务器</span>
+</span></span><span class="line"><span class="cl">            <span class="n">ChannelFuture</span> <span class="n">future</span> <span class="o">=</span> <span class="n">bootstrap</span><span class="o">.</span><span class="n">bind</span><span class="p">(</span><span class="n">socketAddress</span><span class="p">)</span><span class="o">.</span><span class="n">sync</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">            <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;服务器启动开始监听端口: {}&#34;</span><span class="p">,</span> <span class="n">socketAddress</span><span class="o">.</span><span class="n">getPort</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span> <span class="err">对关闭通道进行监听</span>
+</span></span><span class="line"><span class="cl">            <span class="n">future</span><span class="o">.</span><span class="n">channel</span><span class="p">()</span><span class="o">.</span><span class="n">closeFuture</span><span class="p">()</span><span class="o">.</span><span class="n">sync</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="n">catch</span> <span class="p">(</span><span class="n">InterruptedException</span> <span class="n">e</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">e</span><span class="o">.</span><span class="n">printStackTrace</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="n">finally</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span><span class="err">关闭主线程组</span>
+</span></span><span class="line"><span class="cl">            <span class="n">bossGroup</span><span class="o">.</span><span class="n">shutdownGracefully</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span><span class="err">关闭工作线程组</span>
+</span></span><span class="line"><span class="cl">            <span class="n">workGroup</span><span class="o">.</span><span class="n">shutdownGracefully</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">ServerChannelInitializer</span> <span class="k">extends</span> <span class="n">ChannelInitializer</span><span class="o">&lt;</span><span class="n">SocketChannel</span><span class="o">&gt;</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">initChannel</span><span class="p">(</span><span class="n">SocketChannel</span> <span class="n">socketChannel</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="s2">&#34;decoder&#34;</span><span class="p">,</span> <span class="n">new</span> <span class="n">MyMessageDecoder</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="s2">&#34;encoder&#34;</span><span class="p">,</span> <span class="n">new</span> <span class="n">MyMessageEncoder</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="n">new</span> <span class="n">NettyServerHandler</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyServerHandler</span> <span class="k">extends</span> <span class="n">ChannelInboundHandlerAdapter</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">客户端连接会触发</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelActive</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;服务端 Active......&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">客户端发消息会触发</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelRead</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="ne">Object</span> <span class="n">msg</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;服务器收到消息: {}&#34;</span><span class="p">,</span> <span class="n">msg</span><span class="o">.</span><span class="n">toString</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">MessageProtocol</span> <span class="n">mp</span> <span class="o">=</span> <span class="p">(</span><span class="n">MessageProtocol</span><span class="p">)</span><span class="n">msg</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">int</span> <span class="n">len</span> <span class="o">=</span> <span class="n">mp</span><span class="o">.</span><span class="n">getLen</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span> <span class="o">=</span> <span class="n">mp</span><span class="o">.</span><span class="n">getContent</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;服务器接收到信息如下&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;长度=&#34;</span> <span class="o">+</span> <span class="n">len</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;内容=&#34;</span> <span class="o">+</span> <span class="n">new</span> <span class="ne">String</span><span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">Charset</span><span class="o">.</span><span class="n">forName</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">)));</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">回复消息</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">String</span> <span class="n">responseContent</span> <span class="o">=</span> <span class="n">UUID</span><span class="o">.</span><span class="n">randomUUID</span><span class="p">()</span><span class="o">.</span><span class="n">toString</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">int</span> <span class="n">responseLen</span> <span class="o">=</span> <span class="n">responseContent</span><span class="o">.</span><span class="n">getBytes</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">)</span><span class="o">.</span><span class="n">length</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">byte</span><span class="p">[]</span> <span class="n">responseContent2</span> <span class="o">=</span> <span class="n">responseContent</span><span class="o">.</span><span class="n">getBytes</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">构建一个协议包</span>
+</span></span><span class="line"><span class="cl">        <span class="n">MessageProtocol</span> <span class="n">messageProtocol</span> <span class="o">=</span> <span class="n">new</span> <span class="n">MessageProtocol</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setLen</span><span class="p">(</span><span class="n">responseLen</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setContent</span><span class="p">(</span><span class="n">responseContent2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">ctx</span><span class="o">.</span><span class="n">writeAndFlush</span><span class="p">(</span><span class="n">messageProtocol</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">给客户端发送消息</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelReadComplete</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ctx</span><span class="o">.</span><span class="n">writeAndFlush</span><span class="p">(</span><span class="s2">&#34;hello client&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">发生异常触发</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">exceptionCaught</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">Throwable</span> <span class="n">cause</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">cause</span><span class="o">.</span><span class="n">printStackTrace</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ctx</span><span class="o">.</span><span class="n">close</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>公共代码部分</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MessageProtocol</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="ne">int</span> <span class="n">len</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="ne">int</span> <span class="n">getLen</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">len</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">setLen</span><span class="p">(</span><span class="ne">int</span> <span class="n">len</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">len</span> <span class="o">=</span> <span class="n">len</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">byte</span><span class="p">[]</span> <span class="n">getContent</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">content</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">setContent</span><span class="p">(</span><span class="n">byte</span><span class="p">[]</span> <span class="n">content</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">content</span> <span class="o">=</span> <span class="n">content</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="ne">String</span> <span class="n">toString</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="s2">&#34;MessageProtocol{&#34;</span> <span class="o">+</span>
+</span></span><span class="line"><span class="cl">                <span class="s2">&#34;len=&#34;</span> <span class="o">+</span> <span class="n">len</span> <span class="o">+</span>
+</span></span><span class="line"><span class="cl">                <span class="s2">&#34;, content=&#34;</span> <span class="o">+</span> <span class="n">new</span> <span class="ne">String</span><span class="p">(</span><span class="n">content</span><span class="p">)</span> <span class="o">+</span>
+</span></span><span class="line"><span class="cl">                <span class="s1">&#39;}&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MyMessageDecoder</span> <span class="k">extends</span> <span class="n">ReplayingDecoder</span><span class="o">&lt;</span><span class="n">Void</span><span class="o">&gt;</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">decode</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">ByteBuf</span> <span class="ow">in</span><span class="p">,</span> <span class="n">List</span><span class="o">&lt;</span><span class="ne">Object</span><span class="o">&gt;</span> <span class="n">out</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">需要将得到二进制字节码</span><span class="o">-&gt;</span> <span class="n">MessageProtocol</span> <span class="err">数据包</span><span class="p">(</span><span class="err">对象</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">int</span> <span class="n">length</span> <span class="o">=</span> <span class="ow">in</span><span class="o">.</span><span class="n">readInt</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span> <span class="o">=</span> <span class="n">new</span> <span class="n">byte</span><span class="p">[</span><span class="n">length</span><span class="p">];</span>
+</span></span><span class="line"><span class="cl">        <span class="ow">in</span><span class="o">.</span><span class="n">readBytes</span><span class="p">(</span><span class="n">content</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">封装成</span> <span class="n">MessageProtocol</span> <span class="err">对象，放入</span> <span class="n">out</span><span class="err">，</span> <span class="err">传递下一个</span><span class="n">handler业务处理</span>
+</span></span><span class="line"><span class="cl">        <span class="n">MessageProtocol</span> <span class="n">messageProtocol</span> <span class="o">=</span> <span class="n">new</span> <span class="n">MessageProtocol</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setLen</span><span class="p">(</span><span class="n">length</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setContent</span><span class="p">(</span><span class="n">content</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">out</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">messageProtocol</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MyMessageEncoder</span> <span class="k">extends</span> <span class="n">MessageToByteEncoder</span><span class="o">&lt;</span><span class="n">MessageProtocol</span><span class="o">&gt;</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">encode</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">MessageProtocol</span> <span class="n">msg</span><span class="p">,</span> <span class="n">ByteBuf</span> <span class="n">out</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;MyMessageEncoder encode 方法被调用&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">out</span><span class="o">.</span><span class="n">writeInt</span><span class="p">(</span><span class="n">msg</span><span class="o">.</span><span class="n">getLen</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">out</span><span class="o">.</span><span class="n">writeBytes</span><span class="p">(</span><span class="n">msg</span><span class="o">.</span><span class="n">getContent</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div></div>
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+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#geospatial">
+                    Geospatial
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e5%8f%91%e5%b8%83%e4%b8%8e%e8%ae%a2%e9%98%85">
+                    Redis发布与订阅
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e4%ba%8b%e5%8a%a1">
+                    Redis事务
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e4%ba%8b%e5%8a%a1%e7%89%b9%e6%80%a7">
+                    Redis事务特性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%8b%e5%8a%a1%e5%86%b2%e7%aa%81">
+                    事务冲突
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%82%b2%e8%a7%82%e9%94%81">
+                    悲观锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b9%90%e8%a7%82%e9%94%81">
+                    乐观锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e4%b8%8e%e7%bc%93%e5%ad%98">
+                    Redis与缓存
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%ad%98%e7%a9%bf%e9%80%8f">
+                    缓存穿透
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%ad%98%e5%87%bb%e7%a9%bf">
+                    缓存击穿
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%ad%98%e9%9b%aa%e5%b4%a9">
+                    缓存雪崩
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e9%83%a8%e7%bd%b2%e7%ad%96%e7%95%a5">
+                    Redis部署策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e4%b8%bb%e4%bb%8e%e5%a4%8d%e5%88%b6">
+                    Redis主从复制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%90%ad%e5%bb%ba%e4%b8%bb%e4%bb%8e%e5%a4%8d%e5%88%b6">
+                    搭建主从复制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%bb%e4%bb%8e%e5%a4%8d%e5%88%b6%e8%bf%87%e7%a8%8b">
+                    主从复制过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%80%e4%b8%bb%e4%ba%8c%e4%bb%86">
+                    一主二仆
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%96%aa%e7%81%ab%e7%9b%b8%e4%bc%a0">
+                    薪火相传
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%ae%a2%e4%b8%ba%e4%b8%bb">
+                    反客为主
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e5%93%a8%e5%85%b5%e6%a8%a1%e5%bc%8f">
+                    Redis哨兵模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%90%ad%e5%bb%ba%e5%93%a8%e5%85%b5%e6%a8%a1%e5%bc%8f">
+                    搭建哨兵模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%8d%e5%88%b6%e5%bb%b6%e6%97%b6">
+                    复制延时
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%89%e4%b8%be%e6%9c%ba%e5%88%b6">
+                    选举机制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e9%9b%86%e7%be%a4">
+                    Redis集群
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e9%9b%86%e7%be%a4%e6%95%b0%e6%8d%ae%e5%88%86%e7%89%87">
+                    Redis集群数据分片
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%90%ad%e5%bb%baredis%e9%9b%86%e7%be%a4">
+                    搭建Redis集群
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%93%8d%e4%bd%9credis%e9%9b%86%e7%be%a4">
+                    操作Redis集群
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e5%86%85%e5%ad%98%e6%b7%98%e6%b1%b0%e7%ad%96%e7%95%a5">
+                    Redis内存淘汰策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a0%e9%99%a4%e7%ad%96%e7%95%a5">
+                    删除策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b7%98%e6%b1%b0%e7%ad%96%e7%95%a5">
+                    淘汰策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#lru%e7%ae%97%e6%b3%95%e5%8f%8a%e5%ae%9e%e7%8e%b0">
+                    LRU算法及实现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%b8%80">
+                    方式一
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%ba%8c">
+                    方式二
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e6%8c%81%e4%b9%85%e5%8c%96">
+                    Redis持久化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#rdb%e6%8c%81%e4%b9%85%e5%8c%96">
+                    RDB持久化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%9b%b8%e5%85%b3%e9%85%8d%e7%bd%ae">
+                    相关配置
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%89%a7%e8%a1%8c%e8%bf%87%e7%a8%8b">
+                    执行过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#aof%e6%8c%81%e4%b9%85%e5%8c%96">
+                    AOF持久化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%9b%b8%e5%85%b3%e9%85%8d%e7%bd%ae-1">
+                    相关配置
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%89%a7%e8%a1%8c%e8%bf%87%e7%a8%8b-1">
+                    执行过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+                    对比及使用
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+        
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+                    Redis大key问题
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+            </li>
+            
+            
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+        
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+                    Redis数据库双写一致性问题
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+            
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+        
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+        
+        </ul>
+        
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+        
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+                </a>
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+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
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+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Redis详解</h2>
+                        <span id="post_page_title_date" class="date">2021.06.17</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="redis概述">Redis概述</h2>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.runoob.com/redis/redis-intro.html">https://www.runoob.com/redis/redis-intro.html</a></li>
+<li><a href="https://www.redis.com.cn/redis-interview-questions.html">https://www.redis.com.cn/redis-interview-questions.html</a></li>
+</ul>
+<h3 id="什么是redis">什么是Redis</h3>
+<p>Redis(<strong>Remote Dictionary Server</strong>) Redis 是一个开源的使用 ANSI C 语言编写、遵守 BSD 协议、支持网络、可基于内存亦可持久化的日志型、Key-Value 数据库，并提供多种语言的 API 的<strong>非关系型数据库</strong>。</p>
+<p><strong>简而言之，Redis是一个可基于内存亦可持久化的日志型、Key-Value非关系型数据库。</strong></p>
+<h3 id="非关系型数据库">非关系型数据库</h3>
+<p>非关系型数据库，简称NoSql，是Not Only SQL 的缩写，是对不同于传统的关系型数据库的数据库管理系统的统称，泛指非关系型的数据库。
+NoSql 不依赖业务逻辑方式存储，而以简单的key-value模式存储。因此大大的增加了数据库的扩展能力。</p>
+<p>NoSql特点:</p>
+<ul>
+<li>不遵循SQL标准;</li>
+<li>不支持ACID;</li>
+<li>远超于SQL的性能;</li>
+</ul>
+<p>NoSql适用场景:</p>
+<ul>
+<li>对数据高并发的读写;</li>
+<li>海量数据的读写;</li>
+<li>对数据高可扩展性的;</li>
+</ul>
+<p>NoSql不适用场景:</p>
+<ul>
+<li>需要事务支持;</li>
+<li>基于sql的结构化查询存储，处理复杂的关系,需要及时查询;</li>
+<li>用不着sql的和用了sql也不行的情况，请考虑用NoSql；</li>
+</ul>
+<p>传统数据库遵循 ACID 规则。而 Nosql 一般为分布式,而分布式一般遵循 <a href="/iblog/posts/essays/java-transaction/#cap%E7%90%86%E8%AE%BA">CAP</a> 定理。</p>
+<h3 id="redis相关知识">Redis相关知识</h3>
+<p>Redis 默认16个数据库，类似数组下标从0开始，初始默认使用0号库。可使用命令 <code>select  &lt;dbid&gt;</code>来切换数据库。如: <code>select 8</code> 。</p>
+<p>Redis是单线程+<a href="/iblog/posts/rookie/rookie-io/#reactor-%E6%A8%A1%E5%9E%8B">多路IO复用技术</a></p>
+<p><strong>多路复用：</strong>
+指使用一个线程来检查多个文件描述符（Socket）的就绪状态，比如调用select和poll函数，传入多个文件描述符，如果有一个文件描述符就绪，则返回，否则阻塞直到超时。得到就绪状态后进行真正的操作可以在同一个线程里执行，也可以启动线程执行，比如使用线程池。</p>
+<p><strong>Redis与原子性：</strong>
+所谓原子操作是指不会被线程调度机制打断的操作；这种操作一旦开始，就一直运行到结束，中间不会有任何 context switch （切换到另一个线程）。
+在单线程中，能够在单条指令中完成的操作都可以认为是&quot;原子操作&quot;，因为中断只能发生于指令之间；在多线程中，不能被其它进程或线程打断的操作就叫原子操作；
+<strong>Redis命令的原子性主要得益于Redis的单线程机制。</strong></p>
+<p>Redis使用场景：</p>
+<ul>
+<li>配合关系型数据库做高速缓存
+<ul>
+<li>高频次，热门访问的数据，放入Redis中可降低数据库IO</li>
+<li>分布式架构，做session共享</li>
+</ul>
+</li>
+<li>多样的数据结构存储持久化数据
+<ul>
+<li>利用zset排序，做排行榜功能、大数据去重；</li>
+<li>利用Redis key的实效性数据，如将手机验证码放入Redis；</li>
+<li>发布订阅消息系统，构建队列；</li>
+<li>利用Redis的原子性来做计数器、秒杀等；</li>
+</ul>
+</li>
+</ul>
+<p>Redis特点：</p>
+<ul>
+<li>Redis 支持数据的持久化，可以将内存中的数据保存在磁盘中，重启的时候可以再次加载进行使用;</li>
+<li>Redis 支持数据的备份，即master-slave模式的数据备份;</li>
+<li>Redis 可以存储键与不同数据结构类型之间的映射:</li>
+</ul>
+<p>Redis优点：</p>
+<ul>
+<li>性能极高 – 因为是纯内存操作，Redis能读的速度是110000次/s,写的速度是81000次/s；</li>
+<li>丰富的特性 – Redis还支持 publish/subscribe, 通知, key 过期等等特性；</li>
+<li>丰富的数据类型 – Redis支持二进制案例的 Strings, Lists, Hashes, Sets 及 Ordered Sets 数据类型操作；</li>
+<li>原子 – Redis的所有操作都是原子性的，意思就是要么成功执行要么失败完全不执行。单个操作是原子性的。多个操作也支持事务，即原子性，通过MULTI和EXEC指令包起来；</li>
+</ul>
+<p>Redis缺点：</p>
+<ul>
+<li>Redis 的主要缺点是数据库容量受到物理内存的限制，不能用作海量数据的高性能读写，因此Redis适合的场景主要局限在较小数据量的高性能操作和运算上。</li>
+</ul>
+<h3 id="redis基础命令">Redis基础命令</h3>
+<blockquote>
+<p>如果你使用docker可以先启动Redis容器再用<code>docker exec -it &lt;容器ID&gt; redis-cli</code>命令进入redis客户端。</p>
+</blockquote>
+<p>基础命令：</p>
+<ul>
+<li>查看当前库所有key：<code>keys *</code></li>
+<li>判断某个key是否存在：<code>exists &lt;key&gt;</code></li>
+<li>查看key是什么类型：<code>type &lt;key&gt;</code></li>
+<li>删除指定的key数据：<code>del &lt;key&gt;</code></li>
+<li>根据value选择非阻塞删除,异步删除：<code>unlink &lt;key&gt;</code></li>
+<li>为给定的key设置过期时间：<code>expire key &lt;time&gt;</code></li>
+<li>查看还有多少秒过期，-1表示永不过期，-2表示已过期：<code>ttl &lt;key&gt;</code></li>
+<li>切换数据库：<code>select &lt;dbid&gt;</code></li>
+<li>查看当前数据库的key的数量：<code>dbsize</code></li>
+<li><strong>清空当前库(慎用)：<code>flushdb</code></strong></li>
+<li><strong>清空全部库(慎用)：<code>flushall</code></strong></li>
+</ul>
+<p>更多命令详见：</p>
+<ul>
+<li><a href="http://www.redis.cn/commands.html">http://www.redis.cn/commands.html</a></li>
+<li><a href="https://www.redis.com.cn/commands.html">https://www.redis.com.cn/commands.html</a></li>
+</ul>
+<h3 id="redis数据类型">Redis数据类型</h3>
+<p>Redis 可以存储键和不同类型的值之间的映射。键的类型只能为字符串，值常见有五种数据类型：字符串、列表、集合、散列表、有序集合，Redis后续的更新中又新添加了位图、地理位置等数据类型。</p>
+<table>
+<thead>
+<tr>
+<th>名称</th>
+<th>使用场景</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#string">string-字符串</a></td>
+<td>作为常规的key-value缓存应用</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#hash">hash-哈希</a></td>
+<td>主要用来存储对象信息</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#list">list-列表</a></td>
+<td>缓存一些列表数据：关注列表、粉丝列表等</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#set">set-集合</a></td>
+<td>去重；提供了求交集、并集、差集等操作，可以用来做共同关注、共同好友</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#zset">sorted set-有序集合</a></td>
+<td>用来做排行榜</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#bitmaps">bitmaps-位图</a></td>
+<td>可以用来统计状态，如日活是否浏览过某个东西</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#hyperloglog">hyperloglog-基数统计</a></td>
+<td>用来做统计独立IP数、搜索记录数</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#geospatial">geospatial-地理位置</a></td>
+<td>可以用来做附近的人、地图的一些推送接口</td>
+</tr>
+</tbody>
+</table>
+<h4 id="string">String</h4>
+<p>String是Redis最基本的类型，一个key对应一个value。String类型是二进制安全的。意味着Redis的string可以包含任何数据。比如jpg图片或者序列化的对象。String类型是Redis最基本的数据类型，一个Redis中字符串value最多可以是512M。</p>
+<p><img alt="Redis详解-001" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-001.png"></p>
+<p>String的数据结构为简单动态字符串(Simple Dynamic String,缩写SDS)。是可以修改的字符串，内部结构实现上类似于Java的ArrayList，采用预分配冗余空间的方式来减少内存的频繁分配.</p>
+<p>如图中所示,内部为当前字符串实际分配的空间capacity一般要高于实际字符串长度len。当字符串长度小于1M时，扩容都是加倍现有的空间，如果超过1M，扩容时一次只会多扩1M的空间。需要注意的是字符串最大长度为512M。</p>
+<p>常用命令：</p>
+<ul>
+<li>添加键值对：<code>set &lt;key&gt; &lt;value&gt;</code></li>
+<li>查询对应键值：<code>get &lt;key&gt;</code></li>
+<li>将给定的<value>追加到原值的末尾：<code>append &lt;key&gt; &lt;value&gt;</code></li>
+<li>获得值的长度：<code>strlen &lt;key&gt;</code></li>
+<li>只有在<key>不存在时设置<key>的值：<code>setnx &lt;key&gt; &lt;value&gt;</code></li>
+<li>将<key>中储存的数字值增1,只能对数字值操作，如果为空，新增值为1：<code>incr &lt;key&gt;</code></li>
+<li>将<key>中储存的数字值减1,只能对数字值操作，如果为空，新增值为-1：<code>decr &lt;key&gt;</code></li>
+<li>将<key>中储存的数字值增减，自定义步长：<code>incrby/decrby &lt;key&gt;&lt;步长&gt;</code></li>
+</ul>
+<h4 id="list">List</h4>
+<p>Redis列表是简单的字符串列表，按照插入顺序排序。你可以添加一个元素到列表的头部（左边）或者尾部（右边）,单键多值。它的底层实际是个双向链表，对两端的操作性能很高，通过索引下标的操作中间的节点性能会较差。</p>
+<p><img alt="Redis详解-002" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-002.png"></p>
+<p>List的数据结构为快速链表quickList。首先在列表元素较少的情况下会使用一块连续的内存存储，这个结构是ziplist，也即是压缩列表。它将所有的元素紧挨着一起存储，分配的是一块连续的内存。当数据量比较多的时候才会改成quicklist。</p>
+<p>常用命令：</p>
+<ul>
+<li>从左边/右边插入一个或多个值：<code>lpush/rpush &lt;key&gt;&lt;value1&gt;&lt;value2&gt;&lt;value3&gt;</code></li>
+<li>从左边/右边吐出一个值：<code>lpop/rpop &lt;key&gt;</code></li>
+<li>从<key1>列表右边吐出一个值，插到<key2>列表左边：<code>rpoplpush &lt;key1&gt;&lt;key2&gt;</code></li>
+<li>按照索引下标获得元素，从左到右，<code>0 -1</code>表示获取所有：<code>lrange &lt;key&gt;&lt;start&gt;&lt;stop&gt;</code></li>
+<li>获得列表长度：<code>llen &lt;key&gt;</code></li>
+<li>在<value>的后面插入<newvalue>插入值：<code>linsert &lt;key&gt; before &lt;value&gt;&lt;newvalue&gt;</code></li>
+<li>从左边删除n个<value>：<code>lrem &lt;key&gt;&lt;n&gt;&lt;value&gt;</code></li>
+<li>将列表key下标为<index>的值替换成value：<code>lset &lt;key&gt;&lt;index&gt;&lt;value&gt;</code></li>
+</ul>
+<h4 id="set">Set</h4>
+<p>Redis set对外提供的功能与list类似是一个列表的功能，特殊之处在于set是可以<strong>自动去重的</strong>，当你需要存储一个列表数据，又不希望出现重复数据时，set是一个很好的选择，并且set提供了判断某个成员是否在一个set集合内的重要接口，这个也是list所不能提供的。</p>
+<p>Redis的Set是string类型的无序集合。它底层其实是一个value为null的hash表，所以添加，删除，查找的复杂度都是O(1)。</p>
+<blockquote>
+<p>复杂度O(1)：数据增加，查找数据的时间不变。</p>
+</blockquote>
+<p>Set数据结构是dict字典，字典是用哈希表实现的。在Java中HashSet的内部实现使用的是HashMap，只不过所有的value都指向同一个对象。Redis的set结构也是一样，它的内部也使用hash结构，所有的value都指向同一个内部值。</p>
+<p>常用命令：</p>
+<ul>
+<li>将一个或多个元素加入到集合key中，已经存在的元素将被忽略：<code>sadd &lt;key&gt;&lt;value1&gt;&lt;value2&gt;</code></li>
+<li>取出该集合的所有值：<code>smembers &lt;key&gt;</code></li>
+<li>判断集合<key>是否为含有该<value>值，有1，没有0：<code>sismember &lt;key&gt;&lt;value&gt;</code></li>
+<li>返回该集合的元素个数：<code>scard&lt;key&gt;</code></li>
+<li>删除集合中的某个元素：<code>srem &lt;key&gt;&lt;value1&gt;&lt;value2&gt;</code></li>
+<li>随机从该集合中吐出一个值，可指定key，会从集合中删除：<code>spop &lt;key&gt;</code></li>
+<li>随机从该集合中取出n个值，不会从集合中删除：<code>srandmember &lt;key&gt;&lt;n&gt;</code></li>
+<li>把集合中一个值从一个集合移动到另一个集合：<code>smove &lt;source Key&gt;&lt;destination Key&gt;&lt;value&gt;</code></li>
+<li>返回两个集合的交集元素：<code>sinter &lt;key1&gt;&lt;key2&gt;</code></li>
+<li>返回两个集合的并集元素：<code>sunion &lt;key1&gt;&lt;key2&gt;</code></li>
+<li>返回两个集合的差集元素(key1中的，不包含key2中的)：<code>sdiff &lt;key1&gt;&lt;key2&gt;</code></li>
+</ul>
+<h4 id="hash">Hash</h4>
+<p>Redis hash 是一个键值对集合。Redis hash是一个string类型的field和value的映射表，hash特别适合用于存储对象。类似Java里面的Map&lt;String,Object&gt;。</p>
+<p>Hash类型对应的数据结构是两种：ziplist（压缩列表），hashtable（哈希表）。当field-value长度较短且个数较少时，使用ziplist，否则使用hashtable。</p>
+<p>常用命令：</p>
+<ul>
+<li>给<key>集合中的<field>键赋值<value>：<code>hset &lt;key&gt;&lt;field&gt;&lt;value&gt;</code></li>
+<li>从<key1>集合<field>取出 value：<code>hget &lt;key1&gt;&lt;field&gt;</code></li>
+<li>批量设置hash的值：<code>hmset &lt;key1&gt;&lt;field1&gt;&lt;value1&gt;&lt;field2&gt;&lt;value2&gt;...</code></li>
+<li>查看哈希表<key>中，给定域<field>是否存在：<code>hexists&lt;key1&gt;&lt;field&gt;</code></li>
+<li>列出该hash集合的所有<field>：<code>hkeys &lt;key&gt;</code></li>
+<li>列出该hash集合的所有<value>：<code>hvals &lt;key&gt;</code></li>
+<li>为哈希表<key>中的域<field>的值加上增量1：<code>hincrby &lt;key&gt;&lt;field&gt;&lt;increment&gt;</code></li>
+<li>将哈希表<key>中的域<field> 的值设置为<value>,当且仅当域<field>不存在：<code>hsetnx &lt;key&gt;&lt;field&gt;&lt;value&gt;</code></li>
+</ul>
+<h4 id="zset">ZSet</h4>
+<p>sorted set 有序集合也称为 zset，Redis有序集合zset与普通集合set非常相似，是一个没有重复元素的字符串集合。不同之处是有序集合的每个成员都关联了一个评分（score）,这个评分被用来按照从最低分到最高分的方式排序集合中的成员。集合的成员是唯一的，但是评分可以是重复了 。</p>
+<p>因为元素是有序的, 所以你也可以很快的根据评分（score）或者次序（position）来获取一个范围的元素。
+访问有序集合的中间元素也是非常快的,因此你能够使用有序集合作为一个没有重复成员的智能列表。</p>
+<p>SortedSet(zset)是Redis提供的一个非常特别的数据结构，一方面它等价于Java的数据结构Map&lt;String, Double&gt;，可以给每一个元素value赋予一个权重score，另一方面它又类似于TreeSet，内部的元素会按照权重score进行排序，可以得到每个元素的名次，还可以通过score的范围来获取元素的列表。</p>
+<p>zset底层使用了两个数据结构:</p>
+<ul>
+<li>hash，hash的作用就是关联元素value和权重score，保障元素value的唯一性，可以通过元素value找到相应的score值;</li>
+<li>跳跃表，跳跃表的目的在于给元素value排序，根据score的范围获取元素列表;</li>
+</ul>
+<blockquote>
+<p>跳跃表：<br>
+有序集合在生活中比较常见，例如根据成绩对学生排名，根据得分对玩家排名等。对于有序集合的底层实现，可以用数组、平衡树、链表等。数组不便元素的插入、删除；平衡树或红黑树虽然效率高但结构复杂；链表查询需要遍历所有效率低。Redis采用的是跳跃表。跳跃表效率堪比红黑树，实现远比红黑树简单。
+<br>
+举例：对比有序链表和跳跃表，从链表中查询出51</p>
+<p>有序链表: 查找值为51的元素，需要从第一个元素开始依次查找、比较才能找到;共需要6次比较。
+<img alt="Redis详解-003" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-003.png"></p>
+<p>跳跃表:从第2层开始，1节点比51节点小，向后比较；21节点比51节点小，继续向后比较，后面就是NULL了，所以从21节点向下到第1层；在第1层，41节点比51节点小，继续向后，61节点比51节点大，所以从41向下；在第0层，51节点为要查找的节点，节点被找到，共查找4次。
+<img alt="Redis详解-004" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-004.png"></p>
+<p>可以看出跳跃表比有序链表效率要高。</p>
+</blockquote>
+<p>常用命令：</p>
+<ul>
+<li>将一个或多个元素及其score值加入到有序集key当中：<code>zadd  &lt;key&gt;&lt;score1&gt;&lt;value1&gt;&lt;score2&gt;&lt;value2&gt;...</code></li>
+<li>返回有序集 key 中，下标在<start><stop>之间的元素,带withscores，可以让分数一起和值返回到结果集：<code>zrange &lt;key&gt;&lt;start&gt;&lt;stop&gt; [WITHSCORES]</code></li>
+<li>返回有序集 key 中，所有 score 值介于 min 和 max 之间(包括等于 min 或 max )的成员;有序集成员按 score 值递增(从小到大)次序排列：<code>zrangebyscore key minmax [withscores] [limit offset count]</code></li>
+<li>为元素的 score 加上增量：<code>zincrby &lt;key&gt;&lt;increment&gt;&lt;value&gt;</code></li>
+<li>删除该集合下，指定值的元素：<code>zrem &lt;key&gt;&lt;value&gt;</code></li>
+<li>统计该集合，分数区间内的元素个数：<code>zcount &lt;key&gt;&lt;min&gt;&lt;max&gt;</code></li>
+<li>返回该值在集合中的排名，从0开始：<code>zrank &lt;key&gt;&lt;value&gt;</code></li>
+</ul>
+<h4 id="bitmaps">Bitmaps</h4>
+<p>Bitmaps 并不是一种数据结构，实际上它就是字符串，但是可以对字符串的位进行操作。</p>
+<blockquote>
+<p>bit（位）简介：<br>
+现代计算机用二进制（位） 作为信息的基础单位， 1个字节等于8位， 例如“abc”字符串是由3个字节组成， 但实际在计算机存储时将其用二进制表示， “abc”分别对应的ASCII码分别是97、 98、 99， 对应的二进制分别是01100001、 01100010和01100011。</p>
+</blockquote>
+<p>Bitmaps单独提供了一套命令， 所以在Redis中使用Bitmaps和使用字符串的方法不太相同。 可以把Bitmaps想象成一个以位为单位的数组， 数组的每个单元只能存储0和1， 数组的下标在Bitmaps中叫做偏移量。</p>
+<p><img alt="Redis详解-009" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-009.png"></p>
+<p>常用命令：</p>
+<ul>
+<li>设置Bitmaps中某个偏移量的值(0或1),offset偏移量从0开始：<code>setbit &lt;key&gt;&lt;offset&gt;&lt;value&gt;</code></li>
+<li>获取Bitmaps中某个偏移量的值,获取键的第offset位的值,offset偏移量从0开始，不存在则返回0：<code>getbit &lt;key&gt;&lt;offset&gt;</code></li>
+<li>统计字符串从start字节到end字节bit值为1的数量：<code>bitcount &lt;key&gt;[start end]</code></li>
+</ul>
+<p>虽然使用位操作能够极大提高内存使用效率，但也并非总是如此，合理地使用操作位能才能够有效地提高内存使用率和开发效率。</p>
+<p>假设网站有1亿用户， 每天独立访问的用户有5千万， 如果每天用集合类型和Bitmaps分别存储活跃用户可以得到表：</p>
+<p>Set和Bitmaps存储一天活跃用户对比：</p>
+<blockquote>
+<ul>
+<li><strong>Set每个用户id占用空间</strong>：假设用户id用的是long存储占8字节，所以Set用户id占用空间是8*8bit=64bit。</li>
+<li><strong>Bitmaps需要存储的用户量</strong>：因为Bitmaps 并不是一种数据结构，实际上是字符串，所以在存储的时候需要存储全部的用户，此处为1亿。</li>
+</ul>
+</blockquote>
+<table>
+<thead>
+<tr>
+<th>数据类型</th>
+<th>每个用户id占用空间</th>
+<th>需要存储的用户量</th>
+<th>全部内存量</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>Set</td>
+<td>64bit</td>
+<td>50000000</td>
+<td>64位*50000000 = 400MB</td>
+</tr>
+<tr>
+<td>Bitmaps</td>
+<td>1bit</td>
+<td>100000000</td>
+<td>1位*100000000 = 12.5MB</td>
+</tr>
+</tbody>
+</table>
+<p>但Bitmaps并不是万金油，假如该网站每天的独立访问用户很少，例如只有10万，这时候使用Bitmaps就不太合适了，两者的对比如下表所示：</p>
+<table>
+<thead>
+<tr>
+<th>数据类型</th>
+<th>每个用户id占用空间</th>
+<th>需要存储的用户量</th>
+<th>全部内存量</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>Set</td>
+<td>64位</td>
+<td>100000</td>
+<td>64位*100000 = 800KB</td>
+</tr>
+<tr>
+<td>Bitmaps</td>
+<td>1位</td>
+<td>100000000</td>
+<td>1位*100000000 = 12.5MB</td>
+</tr>
+</tbody>
+</table>
+<h4 id="hyperloglog">HyperLogLog</h4>
+<p>Redis 在 2.8.9 版本添加了 HyperLogLog 结构。Redis HyperLogLog 是用来做<strong>基数</strong>统计的算法，HyperLogLog 的优点是，在输入元素的数量或者体积非常非常大时，计算基数所需的空间总是固定的、并且是很小的。</p>
+<blockquote>
+<p>HyperLogLog中的基数：比如数据集 {1, 3, 5, 7, 5, 7, 8}， 那么这个数据集的基数集为 {1, 3, 5 ,7, 8}, 不重复元素为5个，5就是基数。 基数估计就是在误差可接受的范围内，快速计算基数。</p>
+</blockquote>
+<p>在 Redis 里面，每个 HyperLogLog 键只需要花费 12 KB 内存，就可以计算接近 2^64 个不同元素的基数。这和计算基数时，元素越多耗费内存就越多的集合形成鲜明对比。</p>
+<p>但是，因为 HyperLogLog 只会根据输入元素来计算基数，而不会储存输入元素本身，所以 HyperLogLog 不能像集合那样，返回输入的各个元素。</p>
+<p>常用命令：</p>
+<ul>
+<li>添加指定元素到 HyperLogLog 中,估计的近似基数发生变化，则返回1，否则返回0：<code>pfadd &lt;key&gt;&lt; element&gt; [element ...]</code></li>
+<li>计算<key>的近似基数：<code>pfcount&lt;key&gt; [key ...]</code></li>
+<li>将一个或多个<key>合并后的结果存储在另一个<key>中：<code>pfmerge &lt;destkey&gt;&lt;sourcekey&gt; [sourcekey ...]</code></li>
+</ul>
+<h4 id="geospatial">Geospatial</h4>
+<p>GEO，Geographic，地理信息的缩写。该类型，就是元素的2维坐标，在地图上就是经纬度。redis基于该类型，提供了经纬度设置、查询、范围查询、距离查询、经纬度Hash等常见操作。</p>
+<p>常用命令：</p>
+<ul>
+<li>添加地理位置，key名称、经度、纬度、名称：<code>geoadd &lt;key&gt;&lt; longitude&gt;&lt;latitude&gt;&lt;member&gt; [longitude latitude member...]</code></li>
+</ul>
+<blockquote>
+<p>两极无法直接添加，一般会下载城市数据，直接通过 Java 程序一次性导入。有效的经度从 -180 度到 180 度。有效的纬度从 -85.05112878 度到 85.05112878 度。当坐标位置超出指定范围时，该命令将会返回一个错误。已经添加的数据，是无法再次往里面添加的。</p>
+</blockquote>
+<ul>
+<li>获得指定地区的坐标值：<code>geopos  &lt;key&gt;&lt;member&gt; [member...]</code></li>
+<li>获取两个位置之间的直线距离,默认单位，米、km表示单位为千米、mi表示单位为英里、ft表示单位为英尺。：<code>geodist &lt;key&gt;&lt;member1&gt;&lt;member2&gt;  [m|km|ft|mi ]</code></li>
+<li>以给定的经纬度为中心，找出某一半径内的元素：<code>georadius &lt;key&gt;&lt;longitude&gt;&lt;latitude&gt;&lt;radius&gt;&lt;m|km|ft|mi&gt; [withcoord]</code></li>
+</ul>
+<h2 id="redis发布与订阅">Redis发布与订阅</h2>
+<p>Redis 发布订阅 (pub/sub) 是一种消息通信模式：发送者 (pub) 发送消息，订阅者 (sub) 接收消息。Redis 客户端可以订阅任意数量的频道。</p>
+<p>客户端可以订阅频道：</p>
+<p><img alt="Redis详解-005" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-005.png"></p>
+<p>给这个频道发布消息后，消息就会发送给订阅的客户端：</p>
+<p><img alt="Redis详解-006" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-006.png"></p>
+<p><strong>实现Redis发布订阅模式：</strong></p>
+<ol>
+<li>
+<p>打开两个Redis客户端;</p>
+</li>
+<li>
+<p>在其中一个客户端输入：<code>subscribe &lt;channel&gt;</code>,channel为订阅的频道名称：
+<img alt="Redis详解-008" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-008.png"></p>
+</li>
+<li>
+<p>在另外一个客户端输入：<code>publish &lt;channel&gt; &lt;message&gt;</code>,channel为订阅的频道名称,message为推送的消息，返回的1是订阅者数量：
+<img alt="Redis详解-007" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-007.png"></p>
+</li>
+</ol>
+<h2 id="redis事务">Redis事务</h2>
+<p>Redis事务是一个单独的隔离操作：事务中的所有命令都会序列化、按顺序地执行。事务在执行的过程中，不会被其他客户端发送来的命令请求所打断。</p>
+<p>Redis事务的主要作用就是<strong>串联多个命令防止别的命令插队</strong>。</p>
+<p>Redis事务操作相关命令：Multi、Exec、discard</p>
+<p><img alt="Redis详解-014" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-014.png"></p>
+<p>从输入Multi命令开始，输入的命令都会依次进入命令队列中，但不会执行，直到输入Exec后，Redis会将之前的命令队列中的命令依次执行。组队的过程中可以通过discard来放弃组队。
+可以将exec命令理解为提交操作，discard理解为回滚操作。</p>
+<p>multi，exec组队成功，提交成功举例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">127.0.0.1:6379&gt; multi
+</span></span><span class="line"><span class="cl">OK
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k1 v1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k2 v2
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k3 v3
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; exec
+</span></span><span class="line"><span class="cl">1) OK
+</span></span><span class="line"><span class="cl">2) OK
+</span></span><span class="line"><span class="cl">3) OK
+</span></span></code></pre></div><p>multi，discard组队失败举例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">127.0.0.1:6379&gt; multi
+</span></span><span class="line"><span class="cl">OK
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k1 v1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k2 v2
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k3 v3
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; discard
+</span></span><span class="line"><span class="cl">OK
+</span></span></code></pre></div><p>如果在组队过程中执行某个命令失败了，则认为组队失败整个队列都会被取消：</p>
+<p><img alt="Redis详解-015" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-015.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">127.0.0.1:6379&gt; multi
+</span></span><span class="line"><span class="cl">OK
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k1 v1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k2
+</span></span><span class="line"><span class="cl">(error) ERR wrong number of arguments for &#39;set&#39; command
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; exec
+</span></span><span class="line"><span class="cl">(error) EXECABORT Transaction discarded because of previous errors.
+</span></span></code></pre></div><p>如果执行阶段某个命令出了错，则只有报错的命令不会被执行，而其他的命令都会执行且不会回滚：</p>
+<p><img alt="Redis详解-016" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-016.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">127.0.0.1:6379&gt; multi 
+</span></span><span class="line"><span class="cl">OK
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k1 v1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; incr k1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k2 v2
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; exec
+</span></span><span class="line"><span class="cl">1) OK
+</span></span><span class="line"><span class="cl">2) (error) ERR value is not an integer or out of range
+</span></span><span class="line"><span class="cl">3) OK
+</span></span></code></pre></div><h3 id="redis事务特性">Redis事务特性</h3>
+<ul>
+<li>单独的隔离操作：事务中的所有命令都会序列化、按顺序地执行。事务在执行的过程中，不会被其他客户端发送来的命令请求所打断。</li>
+<li>没有隔离级别的概念：队列中的命令没有提交之前都不会实际被执行，因为事务提交前任何指令都不会被实际执行</li>
+<li>不保证原子性：事务中如果有一条命令执行失败，其后的命令仍然会被执行，没有回滚</li>
+</ul>
+<h3 id="事务冲突">事务冲突</h3>
+<p><strong>为什么要使用事务？</strong></p>
+<p>想想一个场景：有很多人有你的账户,同时去参加抢购。一个请求想给金额减8000、一个请求想给金额减5000、一个请求想给金额减1000。</p>
+<p>如果不加事务，有可能一个线程在减8000后，还没有写入数据库，此时另一个线程执行减5000操作写入数据库，然后再将减8000的操作写入数据库，就会造成数据异常。针对于高并发这种情况下我们就需要用事务来控制，可以用加锁来处理。</p>
+<p>在Redis中可以使用<a href="/iblog/posts/rookie/rookie-multi-thread/#%E6%82%B2%E8%A7%82%E9%94%81%E4%B8%8E%E4%B9%90%E8%A7%82%E9%94%81">悲观锁、乐观锁</a>的思想来处理。</p>
+<h4 id="悲观锁">悲观锁</h4>
+<p><img alt="Redis详解-017" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-017.png"></p>
+<p>悲观锁(Pessimistic Lock), 顾名思义，就是很悲观，每次去拿数据的时候都认为别人会修改，所以每次在拿数据的时候都会上锁，这样别人想拿这个数据就会block直到它拿到锁。传统的关系型数据库里边就用到了很多这种锁机制，比如行锁，表锁等，读锁，写锁等，都是在做操作之前先上锁。</p>
+<p>悲观锁实现：在Redis中没有悲观锁，但是可以通过调用lua脚本来实现。</p>
+<blockquote>
+<p>Lua 是一个小巧的脚本语言，Lua脚本可以很容易的被C/C++ 代码调用，也可以反过来调用C/C++的函数，Lua并没有提供强大的库，一个完整的Lua解释器不过200k，所以Lua不适合作为开发独立应用程序的语言，而是作为嵌入式脚本语言。
+很多应用程序、游戏使用LUA作为自己的嵌入式脚本语言，以此来实现可配置性、可扩展性。</p>
+</blockquote>
+<p>LUA脚本在Redis中的优势：</p>
+<ul>
+<li>将复杂的或者多步的redis操作，写为一个脚本，一次提交给redis执行，减少反复连接redis的次数。提升性能。</li>
+<li>LUA脚本是类似redis事务，有一定的原子性，不会被其他命令插队，可以完成一些redis事务性的操作。</li>
+</ul>
+<h4 id="乐观锁">乐观锁</h4>
+<p><img alt="Redis详解-018" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-018.png"></p>
+<p>乐观锁(Optimistic Lock), 顾名思义，就是很乐观，每次去拿数据的时候都认为别人不会修改，所以不会上锁，但是在更新的时候会判断一下在此期间别人有没有去更新这个数据，可以使用版本号等机制。乐观锁适用于多读的应用类型，这样可以提高吞吐量。Redis就是利用这种check-and-set机制实现事务的。</p>
+<p>乐观锁实现：在Redis中如果涉及到了操作数据需要用事务控制的情况可以用 WATCH key &hellip; 命令来监控,可以监控多个key。如果在事务执行之前这个key被其他命令所改动，那么事务将被打断。</p>
+<p><img alt="Redis详解-019" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-019.gif"></p>
+<p>UNWATCH 取消 WATCH 命令对所有 key 的监视。如果在执行 WATCH 命令之后，EXEC 命令或DISCARD命令先被执行了的话，那么就不需要再执行UNWATCH了。</p>
+<h2 id="redis与缓存">Redis与缓存</h2>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://cloud.tencent.com/developer/article/1847904">https://cloud.tencent.com/developer/article/1847904</a></li>
+<li><a href="https://blog.csdn.net/qq_27391133/article/details/80364658">https://blog.csdn.net/qq_27391133/article/details/80364658</a></li>
+</ul>
+<p>因为Redis操作的是纯内存所以性能极高，常用来做缓存，来存放一些热点数据。</p>
+<p>用户第一次访问数据库中的某些数据。整个过程会比较慢，因为是从硬盘上读取的。如果将该用户访问的数据存在数缓存中，这样下一次再访问这些数据的时候就可以直接从缓存中获取了。操作缓存就是直接操作内存，所以速度相当快，但随之而来的也会存在一些问题。</p>
+<h3 id="缓存穿透">缓存穿透</h3>
+<p><img alt="Redis详解-027" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-027.png"></p>
+<p>Redis中的key对应的数据在数据源并不存在，每次针对此key的请求从缓存获取不到，请求都会压到数据源，从而可能压垮数据源。简单理解为,避开缓存,疯狂请求数据库里没有的数据.从而造成服务器宕机。</p>
+<p><strong>解决方法</strong></p>
+<ul>
+<li>对空值缓存：如果一个查询返回的数据为空，不管是数据是否不存在，我们仍然把这个空结果进行缓存，设置空结果的过期时间会很短，最长不超过五分钟；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private RedisTemplate&lt;Long, String&gt; redisTemplate;
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private TestMapper testMapper;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public Test findById(Long id) {
+</span></span><span class="line"><span class="cl">        String testStr = redisTemplate.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">        //判断缓存是否存在，是否为空对象
+</span></span><span class="line"><span class="cl">        if (StringUtils.isEmpty(testStr)) {
+</span></span><span class="line"><span class="cl">            // 这里的锁，使用的时候注意锁的力度，这里建议换成分布式锁，这里做演示
+</span></span><span class="line"><span class="cl">            synchronized (TestServiceImpl.class){
+</span></span><span class="line"><span class="cl">                testStr = redisTemplate.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">                if (StringUtils.isEmpty(testStr)) {
+</span></span><span class="line"><span class="cl">                    Test test = testMapper.findById(id);
+</span></span><span class="line"><span class="cl">                    if(test == null){
+</span></span><span class="line"><span class="cl">                        //构建一个空对象
+</span></span><span class="line"><span class="cl">                        test= new Test();
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                    testStr = JSON.toJSONString(test);
+</span></span><span class="line"><span class="cl">                    // 存入Redis中，下次再次访问就不访问数据库
+</span></span><span class="line"><span class="cl">                    redisTemplate.opsForValue().set(id, testStr);
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        Test test = JSON.parseObject(testStr, Test.class);
+</span></span><span class="line"><span class="cl">        //空对象处理
+</span></span><span class="line"><span class="cl">        if(test.getId() == null){
+</span></span><span class="line"><span class="cl">            return null;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        return JSON.parseObject(testStr, Test.class);
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><ul>
+<li>设置可访问的白名单：使用bitmaps类型定义一个可以访问的名单，名单id作为bitmaps的偏移量，每次访问和bitmap里面的id进行比较，如果访问id不在bitmaps里面，进行拦截，不允许访问。</li>
+<li>使用布隆过滤器：布隆过滤器（Bloom Filter）是1970年由布隆提出的。它实际上是一个很长的二进制向量(位图)和一系列随机映射函数（哈希函数）。布隆过滤器可以用于检索一个元素是否在一个集合中。它的优点是空间效率和查询时间都远远超过一般的算法，缺点是有一定的误识别率和删除困难。将所有可能存在的数据哈希到一个足够大的bitmaps中，一个一定不存在的数据会被 这个bitmaps拦截掉，从而避免了对底层存储系统的查询压力。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private TestMapper testMapper;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private RedisTemplate&lt;Long, String&gt; redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    private static BloomFilter&lt;Long&gt; bloomFilter = BloomFilter.create(Funnels.longFunnel(), 1000000000L);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public Test findById(Long id) {
+</span></span><span class="line"><span class="cl">        String testStr = redisTemplate.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">        if (StringUtils.isEmpty(testStr)) {
+</span></span><span class="line"><span class="cl">            //校验是否在布隆过滤器中
+</span></span><span class="line"><span class="cl">            if(bloomFilter.mightContain(id)){
+</span></span><span class="line"><span class="cl">                return null;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            // 这里的锁，使用的时候注意锁的力度，这里建议换成分布式锁，这里做演示
+</span></span><span class="line"><span class="cl">            synchronized (TestServiceImpl.class){
+</span></span><span class="line"><span class="cl">                testStr = redisTemplate.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">                if (StringUtils.isEmpty(testStr) ) {
+</span></span><span class="line"><span class="cl">                    if(bloomFilter.mightContain(id)){
+</span></span><span class="line"><span class="cl">                        return null;
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                    Test test = testMapper.findById(id);
+</span></span><span class="line"><span class="cl">                    if(test == null){
+</span></span><span class="line"><span class="cl">                        //放入布隆过滤器中
+</span></span><span class="line"><span class="cl">                        bloomFilter.put(id);
+</span></span><span class="line"><span class="cl">                        return null;
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                    testStr = JSON.toJSONString(test);
+</span></span><span class="line"><span class="cl">                    redisTemplate.opsForValue().set(id, testStr);
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        return JSON.parseObject(testStr, Test.class);
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><h3 id="缓存击穿">缓存击穿</h3>
+<p><img alt="Redis详解-028" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-028.png"></p>
+<p>key对应的数据存在，但在redis中过期，此时若有大量并发请求过来，这些请求发现缓存过期一般都会从后端数据库加载数据并回设到缓存，大并发集中对这一个点进行访问，当这个key在失效的瞬间，持续的大并发就穿破缓存，直接请求数据库，就像在一个屏障上凿开了一个洞。这个时候大并发的请求可能会瞬间把后端数据源压垮。</p>
+<p><strong>解决方法</strong></p>
+<ul>
+<li>预先设置热门数据：在redis高峰访问之前，把一些热门数据提前存入到redis里面，加大这些热门数据key的时长；</li>
+<li>实时调整：现场监控哪些数据热门，实时调整key的过期时长；</li>
+<li>使用锁：在缓存失效的时候判断拿出来的值为空，先使用缓存工具的某些带成功操作返回值的操作,去set一个mutex key,而不是立即去访问数据源；当操作返回成功时，再进行访问数据库的操作，并回设缓存,最后删除mutex key；当操作返回失败，证明有线程在访问数据源，当前线程睡眠一段时间再重试整个get缓存的方法；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private RedisTemplate&lt;String,Long&gt; template;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private TestMapper testMapper;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> public Long findById(Long id){
+</span></span><span class="line"><span class="cl">     Long value = template.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">     
+</span></span><span class="line"><span class="cl">     if (StringUtils.isEmpty(value)){
+</span></span><span class="line"><span class="cl">         String key = id + &#34;:nx&#34;;
+</span></span><span class="line"><span class="cl">         // 使用 redis setnx 命令如果设置为 1 则代表成功
+</span></span><span class="line"><span class="cl">         if (template.opsForValue().setIfAbsent(key, 1L, 3 * 60, TimeUnit.SECONDS)){
+</span></span><span class="line"><span class="cl">             value = testMapper.findById(id);
+</span></span><span class="line"><span class="cl">             template.opsForValue().set(id.toString(),value,30 * 60);
+</span></span><span class="line"><span class="cl">             template.delete(key);
+</span></span><span class="line"><span class="cl">         }else {
+</span></span><span class="line"><span class="cl">             try {
+</span></span><span class="line"><span class="cl">                 // 睡眠50ms后重试
+</span></span><span class="line"><span class="cl">                 Thread.sleep(50);
+</span></span><span class="line"><span class="cl">                 value = template.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">             } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">                 Thread.interrupted();
+</span></span><span class="line"><span class="cl">             }
+</span></span><span class="line"><span class="cl">         }
+</span></span><span class="line"><span class="cl">         return value;
+</span></span><span class="line"><span class="cl">     }else {
+</span></span><span class="line"><span class="cl">         return value;
+</span></span><span class="line"><span class="cl">     }
+</span></span><span class="line"><span class="cl"> }
+</span></span></code></pre></div><h3 id="缓存雪崩">缓存雪崩</h3>
+<p><img alt="Redis详解-029" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-029.png"></p>
+<p>key对应的数据存在，但在redis中过期，此时若有大量并发请求过来，这些请求发现缓存过期一般都会从后端数据源加载数据并回设到缓存，这个时候大并发的请求可能会瞬间把后端数据源压垮，简单理解为,在某一个时间段,缓存key大面积失效,集中过期.可能会导致服务器宕机。</p>
+<p><strong>解决方法</strong></p>
+<ul>
+<li>构建多级缓存架构：nginx缓存 + redis缓存 + 其他缓存等；</li>
+<li>使用锁或队列：限流降级,在同一时间段,只允许某个线程访问，性能较差；</li>
+<li>设置缓存key永不过期，异步更新；虽然这种方式不会堵塞线程，但是不保证数据一致性，代码复杂度较大，容易堆积垃圾数据；</li>
+<li>将缓存失效时间分散开：比如我们可以在原有的失效时间基础上增加一个随机值，比如1-5分钟随机，这样每一个缓存的过期时间的重复率就会降低，就很难引发集体失效的事件；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private RedisTemplate&lt;String,Long&gt; template;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public void setKeys(){
+</span></span><span class="line"><span class="cl">        template.opsForValue().set(&#34;k1&#34;,1L,30 * 60 + (new Random().nextInt(9999)));
+</span></span><span class="line"><span class="cl">        template.opsForValue().set(&#34;k2&#34;,2L,30 * 60 + (new Random().nextInt(9999)));
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><h2 id="redis部署策略">Redis部署策略</h2>
+<h3 id="redis主从复制">Redis主从复制</h3>
+<p><img alt="Redis详解-022" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-022.png"></p>
+<p>主从复制，是指将一台Redis服务器的数据，复制到其他的Redis服务器。前者称为主节点(master)，后者称为从节点(slave)；数据的复制是单向的，只能由主节点到从节点。Master以写为主，Slave以读为主。</p>
+<p>主从复制的作用：</p>
+<ul>
+<li>读写分离，性能扩展</li>
+<li>负载均衡</li>
+<li>容灾快速恢复</li>
+</ul>
+<h4 id="搭建主从复制">搭建主从复制</h4>
+<ol>
+<li>至少启动三个redis服务器，并分别连接其客户端；</li>
+<li>在客户端使用命令<code>info replication</code> 查看主从相关信息；</li>
+<li>选定从服务器，并在其客户端执行<code>slaveof &lt;ip&gt; &lt;port&gt;</code>命令将该服务器设置为从服务器；</li>
+<li>在客户端使用命令<code>info replication</code> 查看主从相关信息，查看是否生效；</li>
+<li>在主从服务器上测试读写；</li>
+</ol>
+<h4 id="主从复制过程">主从复制过程</h4>
+<p><img alt="Redis详解-023" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-023.png"></p>
+<ol>
+<li>当从服务器连接到主服务器后，从服务器会向主服务器发送同步数据请求；</li>
+<li>主服务器接收到从服务器发送过来的请求，首先会把主服务器数据进行持久化，变为rdb文件，把rdb文件发送到从服务器，从服务器拿到rdb文件进行读取；</li>
+<li>每次主服务器进行写操作后，会向从服务器进行数据同步；</li>
+</ol>
+<p>全量复制：用于初次复制或其他无法进行部分复制的情况，将主节点中的所有数据都发送给从节点，是一个非常重型的操作。</p>
+<p>部分复制：用于网络中断等情况后的复制，只将中断期间主节点执行的写命令发送给从节点，与全量复制相比更加高效。需要注意的是，如果网络中断时间过长，导致主节点没有能够完整地保存中断期间执行的写命令，则无法进行部分复制，仍使用全量复制。</p>
+<h3 id="一主二仆">一主二仆</h3>
+<p><img alt="Redis详解-024" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-024.png"></p>
+<p>特点：</p>
+<ul>
+<li>当主服务挂掉之后，从服务器不会上位；</li>
+<li>当从服务器挂掉之后，主服务器再次写入数据，此时从服务器再次启动，数据与主服务器保持一致；</li>
+<li>从服务器不能执行写操作；</li>
+</ul>
+<h3 id="薪火相传">薪火相传</h3>
+<p><img alt="Redis详解-025" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-025.png"></p>
+<p>特点：</p>
+<ul>
+<li>当主服务挂掉之后，从服务器不会上位；</li>
+<li>上一个slaver可以是下一个slaver的master，可以有效减轻master的写压力,去中心化降低风险；</li>
+<li>一旦某个slave宕机，后面的slave都没法备份，主机挂了，从机还是从机，都无法写数据了；</li>
+</ul>
+<p>可以使用命令<code>slaveof &lt;ip&gt; &lt;port&gt;</code>将该服务器设置为某服务器的从机。</p>
+<h3 id="反客为主">反客为主</h3>
+<p>当一个master宕机后，后面的slave可以立刻升为master，其后面的slave不用做任何修改，手动执行命令<code>slaveof  no one</code> 将从机变为主机。可以使用哨兵模式让&quot;反客为主&quot;模式变为自动。</p>
+<h3 id="redis哨兵模式">Redis哨兵模式</h3>
+<p><img alt="Redis详解-026" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-026.png"></p>
+<p>反客为主的自动版，能够后台监控主机是否故障，如果故障了根据投票数自动将从库转换为主库。当主机挂掉，从机选举中产生新的主机,当之前的主机再次启动，会变为从机。</p>
+<h4 id="搭建哨兵模式">搭建哨兵模式</h4>
+<ol>
+<li>搭建<a href="/iblog/posts/detailed/java-redis/#搭建主从复制">主从模式</a></li>
+<li>新建哨兵配置<code>sentinel.conf</code>文件：</li>
+</ol>
+<blockquote>
+<ul>
+<li>sentinel：哨兵模式</li>
+<li>monitor：监控</li>
+<li>mymaster：主服务器别名</li>
+<li>127.0.0.1 6379：ip端口</li>
+<li>1：至少有多少个哨兵同意迁移的数量
+<br>
+sentinel monitor mymaster 127.0.0.1 6379 1</li>
+</ul>
+</blockquote>
+<ol start="3">
+<li>执行<code>redis-sentinel ./sentinel.conf</code>启动哨兵</li>
+</ol>
+<h4 id="复制延时">复制延时</h4>
+<p>由于所有的写操作都是先在Master上操作，然后同步更新到Slave上，所以从Master同步到Slave机器有一定的延迟，当系统很繁忙的时候，延迟问题会更加严重，Slave机器数量的增加也会使这个问题更加严重。</p>
+<h4 id="选举机制">选举机制</h4>
+<ol>
+<li>优先选择优先级靠前的；
+<blockquote>
+<p>优先级在redis.conf中默认：slave-priority 100，值越小优先级越高。</p>
+</blockquote>
+</li>
+<li>选择偏移量最大的;
+<blockquote>
+<p>偏移量是指获得原主机数据最全的。</p>
+</blockquote>
+</li>
+<li>选择runid最小的服务；
+<blockquote>
+<p>每个redis实例启动后都会随机生成一个40位的runid,这里也就是随机选择。</p>
+</blockquote>
+</li>
+</ol>
+<h3 id="redis集群">Redis集群</h3>
+<p>Redis 集群是 Redis 提供的分布式数据库方案，集群通过分片来实现数据共享，并提供复制和故障转移。</p>
+<p>Redis集群模式是哨兵模式的一种拓展，在没有Redis 集群的时候，人们使用哨兵模式，所有的数据都存在 master 上面，master 的压力越来越大，垂直扩容再多的 salve 已经不能分担 master 的压力的，因为所有的写操作集中都集中在 master 上。所以人们就想到了水平扩容，就是搭建多个 master 节点。客户端进行分片，手动的控制访问其中某个节点。但是这几个节点之间的数据是不共享的。并且如果增加一个节点，需要手动的将数据进行迁移，维护起来很麻烦。
+另外，主从模式，薪火相传模式，主机宕机，导致ip地址发生变化，应用程序中配置需要修改对应的主机地址、端口等信息。所以才产生了 Redis 集群。</p>
+<p>Redis集群是无中心化集群，即每个结点都是入口。Redis 集群通过分区来提供一定程度的可用性;即使集群中有一部分节点失效或者无法进行通讯，集群也可以继续处理命令请求。</p>
+<p>Redis集群故障恢复：</p>
+<ul>
+<li>如果主节点挂掉后，从结点会上位，主节点恢复后，变为从结点；</li>
+<li>如果某一段插槽的主从节点都宕掉，redis服务是否能运行，这个与redis.conf中的参数<code>cluster-require-full-coverage</code>相关；如果为yes则可以继续使用，为no，那么，该插槽数据全都不能使用，也无法存储；</li>
+</ul>
+<p>Redis集群优点：</p>
+<ul>
+<li>实现扩容；</li>
+<li>分摊服务器压力；</li>
+<li>无中心配置相对简单；</li>
+</ul>
+<p>Redis集群缺点：</p>
+<ul>
+<li>多键操作是不被支持、多键的Redis事务是不被支持、lua脚本不被支持；</li>
+<li>由于集群方案出现较晚，很多公司已经采用了其他的集群方案，而代理或者客户端分片的方案想要迁移至redis cluster，需要整体迁移而不是逐步过渡，复杂度较大；</li>
+</ul>
+<h4 id="redis集群数据分片">Redis集群数据分片</h4>
+<p>Redis 集群没有使用一致性hash, 而是引入了 哈希槽的概念. Redis cluster 有固定的 16384 个 hash slot，对每个 key 计算 CRC16 值，然后对 16384 取模，可以获取来决定放置哪个槽.</p>
+<p>集群的每个节点负责一部分hash槽,举个例子,比如当前集群有3个节点,那么:</p>
+<ul>
+<li>节点 A 包含 0 到 5500号哈希槽.</li>
+<li>节点 B 包含5501 到 11000 号哈希槽.</li>
+<li>节点 C 包含11001 到 16384号哈希槽.</li>
+</ul>
+<p>这种结构很容易添加或者删除节点. 比如如果我想新添加个节点D, 我需要从节点 A, B, C中得部分槽到D上. 如果我想移除节点A,需要将A中的槽移到B和C节点上,然后将没有任何槽的A节点从集群中移除即可. 由于从一个节点将哈希槽移动到另一个节点并不会停止服务,所以无论添加删除或者改变某个节点的哈希槽的数量都不会造成集群不可用的状态.</p>
+<h4 id="搭建redis集群">搭建Redis集群</h4>
+<ol>
+<li>修改<code>redis.conf</code>配置文件，修改前建议备份，修改之后启动redis服务；
+<blockquote>
+<p>redis.conf:
+// 引入原始配置文件
+include /home/bigdata/redis.conf
+// 端口
+port 6379
+// pid文件名称
+pidfile &ldquo;/var/run/redis_6379.pid&rdquo;
+// rdb文件名称
+dbfilename &ldquo;dump6379.rdb&rdquo;
+// 日志文件
+logfile &ldquo;/home/bigdata/redis_cluster/redis_err_6379.log&rdquo;
+// 启用集群模式
+cluster-enabled yes
+// 设定节点配置文件名，启动后会自动生成
+cluster-config-file nodes-6379.conf
+// 设定节点失联时间，超过该时间（毫秒），集群自动进行主从切换
+cluster-node-timeout 15000</p>
+</blockquote>
+</li>
+<li>确保所有redis实例启动后,<code>nodes-xxxx.conf</code>文件都正常生成；</li>
+<li><code>cd /opt/redis-6.2.1/src</code>进入redis的src目录，执行：
+<blockquote>
+<p>此处不要用127.0.0.1,请用真实IP地址
+redis-cli &ndash;cluster create &ndash;cluster-replicas 1 192.168.11.101:6379 192.168.11.101:6380 192.168.11.101:6381 192.168.11.101:6389 192.168.11.101:6390 192.168.11.101:6391</p>
+</blockquote>
+</li>
+<li>使用命令<code>redis-cli -c -p&lt;port&gt;</code>登陆redis集群；</li>
+<li>在客户端使用命令<code>cluster nodes</code>查看集群信息；</li>
+</ol>
+<h4 id="操作redis集群">操作Redis集群</h4>
+<ul>
+<li>执行写入一个键值操作：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">set k1 v1
+</span></span><span class="line"><span class="cl">-&gt;Redirected to slot [12706] located at 192.168.137.3:6381
+</span></span><span class="line"><span class="cl">OK
+</span></span></code></pre></div><blockquote>
+<p>这里的slot是插槽：
+一个 Redis 集群包含 16384 个插槽（hash slot），数据库中的每个键都属于这 16384 个插槽的其中一个；集群使用公式 CRC16(key) % 16384 来计算键 key 属于哪个槽， 其中 CRC16(key) 语句用于计算键 key 的 CRC16 校验和。集群中的每个节点负责处理一部分插槽。
+在redis客户端每次录入、查询键值，redis都会计算出该key应该送往的插槽。</p>
+<p>举个例子，如果一个集群可以有主节点，其中：节点 A 负责处理 0 号至 5460 号插槽;节点 B 负责处理 5461 号至 10922 号插槽;节点 C 负责处理 10923 号至 16383 号插槽。</p>
+</blockquote>
+</li>
+<li>执行写入多个键值操作：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">mset k1 v1 k2 v2 k3 v3
+</span></span><span class="line"><span class="cl">(error) CORSSSLOT Keys in request don&#39;t hash to the same slot 
+</span></span></code></pre></div>不在一个slot下的键值，是不能使用mget,mset等多键操作,但是可以可以通过{}来定义组的概念，从而使key中{}内相同内容的键值对放到一个slot中去：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">mset k1{cust} v1 k2{cust} v2 k3{cust} v3
+</span></span></code></pre></div></li>
+<li>查询集群中的值：
+<ul>
+<li>查询count个slot槽中的键：<code>cluster getkeysinslot &lt;slot&gt; &lt;count&gt;</code></li>
+<li>计算key的插槽值：<code>cluster keyslot &lt;key&gt;</code></li>
+<li>计算插槽值有几个key：<code>cluster countkeysinslot &lt;slot&gt;</code></li>
+</ul>
+</li>
+</ul>
+<h2 id="redis内存淘汰策略">Redis内存淘汰策略</h2>
+<p>长期把Redis做缓存用，总有一天Redis内存总会满的。有没有相关这个问题，Redis内存满了会怎么样？</p>
+<p>在<code>redis.conf</code>中把Redis内存设置为1个字节，做一个测试：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">// 默认单位就是字节
+</span></span><span class="line"><span class="cl">maxmemory 1 
+</span></span></code></pre></div><p>设置完之后重启为了确保测试的准确性，重启一下Redis，之后在用下面的命令，向Redis中存入键值对,模拟Redis打满的情况：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">set k1 v1
+</span></span></code></pre></div><p>执行完后会看到下面的信息：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">(error) OOM command not allowed when used memory &gt; &#39;maxmemory&#39;.
+</span></span></code></pre></div><p>大意：OOM，当当前内存大于最大内存时，这个命令不允许被执行。</p>
+<p>是的，Redis也会出现OOM，正因如此，我们才要避免这种情况发生，正常情况下，不考虑极端业务，Redis不是MySql数据库，不能什么都往里边写，一般情况下Redis只存放热点数据。</p>
+<p>Redis默认最大内存是全部的内存，我们在实际配置的时候，一般配实际服务器内存的3/4也就足够了。</p>
+<h3 id="删除策略">删除策略</h3>
+<p>正因为Redis内存打满后报OOM，为了避免出现该情况所以要设置Redis的删除策略。思考一个问题，一个键到了过期时间之后是不是马上就从内存中被删除的？</p>
+<p>当然不是的，那过期之后到底什么时候被删除？是个什么操作？</p>
+<p>Redis提供了三种删除策略：</p>
+<ol>
+<li>定时删除：创建一个定时器，定时随机的对key执行删除操作；</li>
+<li>惰性删除：类似与懒加载，每次只有用到key的时候才会检查，该key是否已经过期，如果过期进行删除操作；</li>
+<li>定期删除：每隔一段时间，就会检查删除掉过期的key；</li>
+</ol>
+<p>定时删除，即用时间换空间；它对于内存来说是友好的，定时清理出干净的空间，但是对于CPU来说并不是友好的，程序需要维护一个定时器，这就会占用CPU资源。</p>
+<p>惰性的删除，即用空间换时间；它对于CPU来说是友好的，CPU不需要维护其它额外的操作，但是对于内存来说是不友好的，因为要是有些key一直没有被访问到，就会一直占用着内存。</p>
+<p>定期删除，是上面两种方案的折中方案，它每隔一段时间删除过期的key，也就是根据具体的业务，合理的取一个时间定期的删除key。</p>
+<p>若果在数据量很大的情况下，定时删除时，key从来没有被检查到过；惰性删除时，key从来没有被使用过，这样就会造成内存泄漏，大量的key堆积在内存中，导致Redis内存空间紧张。</p>
+<p>所以我们必须有一个兜底方案，即Redis的内存淘汰策略。</p>
+<h3 id="淘汰策略">淘汰策略</h3>
+<p>在 <code>Redis 4.0</code> 版本之前有 6 种策略，4.0 增加了 2种，主要新增了 <code>LFU</code> 算法。下图为 <code>Redis 6.2.0</code> 版本的配置文件：</p>
+<p><img alt="Redis详解-012" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-012.png"></p>
+<p>淘汰策略默认,使用<code>noeviction</code>，意思是不再驱逐的，即等着内存被打满。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">The default is:
+</span></span><span class="line"><span class="cl">maxmemory-policy noeviction
+</span></span></code></pre></div><table>
+<thead>
+<tr>
+<th>策略名称</th>
+<th>描述</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td><code>noeviction</code>(默认策略)</td>
+<td>不会驱逐任何key，即内存满了就报错。</td>
+</tr>
+<tr>
+<td><code>allkeys-lru</code></td>
+<td>所有key都是使用<strong>LRU算法</strong>进行淘汰。</td>
+</tr>
+<tr>
+<td><code>volatile-lru</code></td>
+<td>所有<strong>设置了过期时间的key使用LRU算法</strong>进行淘汰。</td>
+</tr>
+<tr>
+<td><code>allkeys-random</code></td>
+<td>所有的key使用<strong>随机淘汰</strong>的方式进行淘汰。</td>
+</tr>
+<tr>
+<td><code>volatile-random</code></td>
+<td>所有<strong>设置了过期时间的key使用随机淘汰</strong>的方式进行淘汰。</td>
+</tr>
+<tr>
+<td><code>volatile-ttl</code></td>
+<td>所有设置了过期时间的key<strong>根据过期时间进行淘汰，越早过期就越快被淘汰</strong>。</td>
+</tr>
+</tbody>
+</table>
+<p>假如在Redis中的数据有一部分是热点数据，而剩下的数据是冷门数据，或者我们不太清楚我们应用的缓存访问分布状况，这时可以使用<code>allkeys-lru</code>。</p>
+<p>可以在<code>redis.conf</code>配置文件中配置:</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">maxmemory-policy allkeys-lru   // 淘汰策略名字
+</span></span></code></pre></div><p>当然也可以动态的配置，在Redis运行时修改：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">// 设置内存淘汰策略
+</span></span><span class="line"><span class="cl">config set maxmemory-policy allkeys-lru
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 查看内存淘汰策略
+</span></span><span class="line"><span class="cl">config get maxmemory-policy
+</span></span></code></pre></div><h3 id="lru算法及实现">LRU算法及实现</h3>
+<p>LRU是，<code>Least Recently Used</code>的缩写，即最近最少使用，是一种常用的页面置换算法。</p>
+<blockquote>
+<p>页面置换算法：
+进程运行时，若其访问的页面不在内存而需将其调入，但内存已无空闲空间时，就需要从内存中调出一页程序或数据，送入磁盘的对换区，其中选择调出页面的算法就称为页面置换算法。</p>
+</blockquote>
+<p>这个算法的思想就是： 如果一个数据在最近一段时间没有被访问到，那么在将来它被访问的可能性也很小。所以，当指定的空间已存满数据时，应当把最久没有被访问到的数据淘汰。</p>
+<p>明白了思想之后，要实现LRU算法，首先要确定数据结构，再确定实现思路。如果对算法有要求，查询和插入的时间复杂度都是<code>O(1)</code>，可以选用链表+哈希的结构来存储：</p>
+<p><img alt="Redis详解-013" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-013.png"></p>
+<h4 id="方式一">方式一</h4>
+<p>链表+哈希，我们不难想到JDK中的<code>LinkedHashMap</code>,在<code>LinkedHashMap</code>文档注释中找到关于LRU算法的相关描述：</p>
+<blockquote>
+<p>A special {@link #LinkedHashMap(int,float,boolean) constructor} is provided to create a linked hash map whose order of iteration is the order  in which its entries were last accessed,from least-recently accessed to most-recently (<i>access-order</i>).  This kind of map is well-suited to building LRU caches.</p>
+</blockquote>
+<p>大意：<code>{@link #LinkedHashMap(int,float,boolean)}</code>提供了一个特殊的构造器来创建一个链表散列映射，其迭代顺序为其条目最后访问的顺序，从最近最少访问到最近最近(<code>access-order</code>)。这种映射非常适合构建LRU缓存。</p>
+<p>参照<code>LinkedHashMap</code>实现LRU算法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MainTest</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="ne">String</span><span class="p">[]</span> <span class="n">args</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">LRUDemo</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="ne">String</span><span class="o">&gt;</span> <span class="n">list0</span> <span class="o">=</span> <span class="n">new</span> <span class="n">LRUDemo</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="bp">true</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;-------------accessOrder等于true-------------&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">context</span><span class="p">(</span><span class="n">list0</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;-------------accessOrder等于false-------------&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">LRUDemo</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="ne">String</span><span class="o">&gt;</span> <span class="n">list1</span> <span class="o">=</span> <span class="n">new</span> <span class="n">LRUDemo</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="bp">false</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">context</span><span class="p">(</span><span class="n">list1</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">context</span><span class="p">(</span><span class="n">LRUDemo</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="ne">String</span><span class="o">&gt;</span> <span class="n">list</span><span class="p">){</span>
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="s2">&#34;a&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="s2">&#34;b&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s2">&#34;c&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="s2">&#34;d&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s2">&#34;123&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s2">&#34;1234&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s2">&#34;12345&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span><span class="s2">&#34;123456&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="k">class</span> <span class="n">LRUDemo</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span> <span class="k">extends</span> <span class="n">LinkedHashMap</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="ne">int</span> <span class="n">capacity</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">LRUDemo</span><span class="p">(</span><span class="ne">int</span> <span class="n">capacity</span><span class="p">,</span> <span class="n">boolean</span> <span class="n">accessOrder</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="n">accessOrder</span> <span class="n">the</span> <span class="n">ordering</span> <span class="n">mode</span> <span class="o">-</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="o">&lt;</span><span class="n">tt</span><span class="o">&gt;</span><span class="bp">true</span><span class="o">&lt;/</span><span class="n">tt</span><span class="o">&gt;</span> <span class="k">for</span> <span class="n">access</span><span class="o">-</span><span class="n">order</span> <span class="err">存取顺序</span><span class="p">:</span><span class="err">如果存贮集合中有相同的元素，再次插入时先删除在插入</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="o">&lt;</span><span class="n">tt</span><span class="o">&gt;</span><span class="bp">false</span><span class="o">&lt;/</span><span class="n">tt</span><span class="o">&gt;</span> <span class="k">for</span> <span class="n">insertion</span><span class="o">-</span><span class="n">order</span> <span class="err">插入顺序：不会因为集合中有相同元素，再次插入该元素就会打乱位置</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">        <span class="n">super</span><span class="p">(</span><span class="n">capacity</span><span class="p">,</span><span class="mf">0.75</span><span class="n">f</span><span class="p">,</span><span class="n">accessOrder</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">capacity</span> <span class="o">=</span> <span class="n">capacity</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">boolean</span> <span class="n">removeEldestEntry</span><span class="p">(</span><span class="n">Map</span><span class="o">.</span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span> <span class="n">V</span><span class="o">&gt;</span> <span class="n">eldest</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">super</span><span class="o">.</span><span class="n">size</span><span class="p">()</span> <span class="o">&gt;</span> <span class="n">capacity</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h4 id="方式二">方式二</h4>
+<p>除了可以参照<code>LinkedHashMap</code>，也可以自己手动实现：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MainTest {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        LRUDemo&lt;Integer,String&gt; list0 = new LRUDemo&lt;&gt;(3);
+</span></span><span class="line"><span class="cl">        context(list0);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void context(LRUDemo&lt;Integer,String&gt; list){
+</span></span><span class="line"><span class="cl">        list.put(1,&#34;a&#34;);
+</span></span><span class="line"><span class="cl">        list.put(2,&#34;b&#34;);
+</span></span><span class="line"><span class="cl">        list.put(3,&#34;c&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(4,&#34;d&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">        System.out.println();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(3,&#34;123&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(3,&#34;1234&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(3,&#34;12345&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">        System.out.println();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(5,&#34;123456&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">class LRUDemo&lt;K, V&gt; {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    static class Node&lt;K,V&gt;{
+</span></span><span class="line"><span class="cl">        K key;
+</span></span><span class="line"><span class="cl">        V value;
+</span></span><span class="line"><span class="cl">        Node&lt;K,V&gt; prev;
+</span></span><span class="line"><span class="cl">        Node&lt;K, V&gt; next;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public Node(){
+</span></span><span class="line"><span class="cl">            prev = next = null;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public Node(K key,V value){
+</span></span><span class="line"><span class="cl">            this.key = key;
+</span></span><span class="line"><span class="cl">            this.value = value;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    static class DoubleLinkedList&lt;K,V&gt;{
+</span></span><span class="line"><span class="cl">        Node&lt;K,V&gt; head;
+</span></span><span class="line"><span class="cl">        Node&lt;K, V&gt; tail;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public DoubleLinkedList(){
+</span></span><span class="line"><span class="cl">            head = new Node&lt;&gt;();
+</span></span><span class="line"><span class="cl">            tail = new Node&lt;&gt;();
+</span></span><span class="line"><span class="cl">            
+</span></span><span class="line"><span class="cl">            // 如果变成尾插法，需要调换头、尾指针的指向
+</span></span><span class="line"><span class="cl">            head.next = tail;
+</span></span><span class="line"><span class="cl">            tail.prev = head;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public void putHead(Node&lt;K, V&gt; node){
+</span></span><span class="line"><span class="cl">            node.next = head.next;
+</span></span><span class="line"><span class="cl">            node.prev = head; // 将新结点插到头部
+</span></span><span class="line"><span class="cl">            head.next.prev = node;
+</span></span><span class="line"><span class="cl">            head.next = node;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public void remove(Node&lt;K, V&gt; node){
+</span></span><span class="line"><span class="cl">            node.prev.next = node.next;
+</span></span><span class="line"><span class="cl">            node.next.prev = node.prev;
+</span></span><span class="line"><span class="cl">            node.prev = node.next = null;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public Node&lt;K,V&gt; getLastNode(){
+</span></span><span class="line"><span class="cl">            return tail.prev;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    private int capacity;
+</span></span><span class="line"><span class="cl">    private Map&lt;K, Node&lt;K,V&gt;&gt; map;
+</span></span><span class="line"><span class="cl">    private DoubleLinkedList&lt;K,V&gt; doubleLinkedList;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public Map&lt;K, Node&lt;K, V&gt;&gt; getMap() {
+</span></span><span class="line"><span class="cl">        return map;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public LRUDemo(int capacity){
+</span></span><span class="line"><span class="cl">        this.capacity = capacity;
+</span></span><span class="line"><span class="cl">        this.map = new HashMap&lt;&gt;();
+</span></span><span class="line"><span class="cl">        doubleLinkedList = new DoubleLinkedList&lt;&gt;();
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public void put(K key,V val){
+</span></span><span class="line"><span class="cl">        if (key == null || val == null){
+</span></span><span class="line"><span class="cl">            return;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        // 如果集合中key已经存在，则先删除
+</span></span><span class="line"><span class="cl">        if (map.containsKey(key)){
+</span></span><span class="line"><span class="cl">            Node&lt;K, V&gt; node = map.get(key);
+</span></span><span class="line"><span class="cl">            node.value = val;
+</span></span><span class="line"><span class="cl">            map.put(key,node);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 刷新node
+</span></span><span class="line"><span class="cl">            doubleLinkedList.remove(node);
+</span></span><span class="line"><span class="cl">            doubleLinkedList.putHead(node);
+</span></span><span class="line"><span class="cl">        }else {
+</span></span><span class="line"><span class="cl">            // 删除最少使用的key
+</span></span><span class="line"><span class="cl">            if (map.size() == capacity){
+</span></span><span class="line"><span class="cl">                Node&lt;K, V&gt; lastNode = doubleLinkedList.getLastNode();
+</span></span><span class="line"><span class="cl">                doubleLinkedList.remove(lastNode);
+</span></span><span class="line"><span class="cl">                map.remove(lastNode.key);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            Node&lt;K, V&gt; newNode = new Node&lt;&gt;(key,val);
+</span></span><span class="line"><span class="cl">            map.put(key,newNode);
+</span></span><span class="line"><span class="cl">            doubleLinkedList.putHead(newNode);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public V get(K key){
+</span></span><span class="line"><span class="cl">        if (!map.containsKey(key)){
+</span></span><span class="line"><span class="cl">            return null;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        Node&lt;K, V&gt; node = map.get(key);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        // 刷新结点位置，将该key移动到队列头部
+</span></span><span class="line"><span class="cl">        doubleLinkedList.remove(node);
+</span></span><span class="line"><span class="cl">        doubleLinkedList.putHead(node);
+</span></span><span class="line"><span class="cl">        return node.value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h2 id="redis持久化">Redis持久化</h2>
+<p><strong>什么是Redis持久化？</strong> 持久化就是把内存的数据写到磁盘中去，防止服务宕机了内存数据丢失。Redis 提供了两种持久化方式:RDB（默认） 和AOF。</p>
+<ul>
+<li>RDB，简而言之，就是在指定的时间间隔内，将 redis 存储的数据生成快照并存储到磁盘等介质上；</li>
+<li>AOF，则是换了一个角度来实现持久化，那就是将 redis 执行过的所有写指令记录下来，在下次 redis 重新启动时，只要把这些写指令从前到后再重复执行一遍，就可以实现数据恢复了；</li>
+</ul>
+<p>其实 RDB 和 AOF 两种方式也可以同时使用，在这种情况下，则会<strong>优先采用 AOF 方式来进行数据恢复</strong>，这是因为 AOF 方式的数据恢复完整度更高。如果你没有数据持久化的需求，也完全可以关闭 RDB 和 AOF 方式，这样的话，redis 将变成一个纯内存数据库，就像 <code>memcache</code> 一样。</p>
+<h3 id="rdb持久化">RDB持久化</h3>
+<p>RDB （Redis DataBase）方式，是将 redis 某一时刻的数据持久化到磁盘中，是一种快照式的持久化方法。</p>
+<h4 id="相关配置">相关配置</h4>
+<ul>
+<li>在redis.conf中配置文件名称,默认是dump.rdb：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">dbfilename dump.rdb
+</span></span></code></pre></div></li>
+<li>rdb文件的保存路径，也可以修改。默认为Redis启动时命令行所在的目录下：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">dir ./
+</span></span></code></pre></div></li>
+<li>默认的快照配置：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">save 3600 1
+</span></span><span class="line"><span class="cl">save 30 10
+</span></span><span class="line"><span class="cl">save 60 10000
+</span></span></code></pre></div></li>
+<li>当Redis无法写入磁盘的话，直接关掉Redis的写操作,默认yes：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">stop-writes-on-bgsave-error yes
+</span></span></code></pre></div></li>
+<li>对于存储到磁盘中的快照，可以设置是否进行压缩存储。如果是的话，redis会采用LZF算法进行压缩：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">rdbcompression yes
+</span></span></code></pre></div></li>
+<li>检查数据完整性,在存储快照后，还可以让redis使用CRC64算法来进行数据校验，但是这样做会增加大约10%的性能消耗，如果希望获取到最大的性能提升，可以关闭此功能，推荐yes：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">rdbchecksum yes
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="执行过程">执行过程</h4>
+<p>redis 在进行数据持久化的过程中，会先将数据写入到一个临时文件中，待持久化过程都结束了，才会用这个临时文件替换上次持久化好的文件。正是这种特性，让我们可以随时来进行备份，因为快照文件总是完整可用的。对于 RDB 方式，redis 会单独创建（fork）一个子进程来进行持久化，而主进程是不会进行任何 IO 操作的，这样就确保了 redis 极高的性能。</p>
+<blockquote>
+<p>fork：</p>
+<ul>
+<li>在Linux程序中，fork()会产生一个和父进程完全相同的子进程，但子进程在此后多会exec系统调用，出于效率考虑，Linux中引入了“写时复制技术”；</li>
+<li>一般情况父进程和子进程会共用同一段物理内存，只有进程空间的各段的内容要发生变化时，才会将父进程的内容复制一份给子进程；</li>
+</ul>
+</blockquote>
+<p><img alt="Redis详解-020" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-020.png"></p>
+<p>如果需要进行大规模数据的恢复，且对于数据恢复的完整性不是非常敏感，那 RDB 方式要比 AOF 方式更加的高效。虽然 RDB 有不少优点，但它的缺点也是不容忽视的：丢失数据风险较大，fork进程在保存rdb文件时会先复制旧文件，如果文件较大则耗时较多。如果你对数据的完整性非常敏感，那么 RDB 方式就不太适合你，因为即使你每 5 分钟都持久化一次，当 redis 故障时，仍然会有近 5 分钟的数据丢失。所以，redis 还提供了另一种持久化方式，那就是 AOF。</p>
+<h3 id="aof持久化">AOF持久化</h3>
+<p>AOF，英文是 Append Only File，即只允许追加不允许改写的文件。如前面介绍的，AOF 方式是<strong>将执行过的写指令记录下来</strong>，在数据恢复时按照从前到后的顺序再将指令都执行一遍。</p>
+<h4 id="相关配置-1">相关配置</h4>
+<ul>
+<li>
+<p>在redis中AOF默认时不开启的：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendonly no
+</span></span></code></pre></div></li>
+<li>
+<p>AOF文件名称,文件路径与rdb保持一致：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendfilename &#34;appendonly.aof&#34;
+</span></span></code></pre></div></li>
+<li>
+<p>AOF同步频率设置：默认的 AOF 持久化策略是每秒钟 fsync 一次（fsync 是指把缓存中的写指令记录到磁盘中），因为在这种情况下，redis 仍然可以保持很好的处理性能，即使 redis 故障，也只会丢失最近 1 秒钟的数据。</p>
+<ol>
+<li>始终同步，每次Redis的写入都会立刻记入日志；性能较差但数据完整性比较好：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendfsync always
+</span></span></code></pre></div><ol start="2">
+<li>每秒同步，每秒记入日志一次，如果宕机，本秒的数据可能丢失：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendfsync everysec
+</span></span></code></pre></div><ol start="3">
+<li>redis不主动进行同步，把同步时机交给操作系统：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendfsync no
+</span></span></code></pre></div></li>
+<li>
+<p>Rewrite压缩：AOF采用文件追加方式，文件会越来越大为避免出现此种情况，新增了重写机制,当AOF文件的大小超过所设定的阈值时，Redis就会启动AOF文件的内容压缩，只保留可以恢复数据的最小指令集。举个例子或许更形象，假如我们调用了 100 次 INCR 指令，在 AOF 文件中就要存储 100 条指令，但这明显是很低效的，完全可以把这 100 条指令合并成一条 SET 指令，这就是重写机制的原理。在进行 AOF 重写时，仍然是采用先写临时文件，全部完成后再替换的流程，所以断电、磁盘满等问题都不会影响 AOF 文件的可用性。</p>
+<ol>
+<li>设置重写的基准值，文件达到100%时开始重写：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">auto-aof-rewrite-percentage
+</span></span></code></pre></div><ol start="2">
+<li>设置重写的基准值，最小文件64MB。达到这个值开始重写：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">auto-aof-rewrite-min-size
+</span></span></code></pre></div><blockquote>
+<p>例如：文件达到70MB开始重写，降到50MB，下次什么时候开始重写？
+系统载入时或者上次重写完毕时，Redis会记录此时AOF大小，设为base_size,如果Redis的AOF文件当前大小&gt;= base_size +base_size*100% (默认)且当前大小&gt;=64mb(默认)的情况下，Redis会对AOF进行重写。</p>
+<p>当前base_size为50MB，根据公式：base_size +base_size*100% = 100MB</p>
+</blockquote>
+</li>
+<li>
+<p>如果在追加日志时，恰好遇到磁盘空间满或断电等情况导致日志写入不完整，也没有关系，可以进行恢复：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">redis-check-aof --fix AOP文件名称
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="执行过程-1">执行过程</h4>
+<p><img alt="Redis详解-021" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-021.png"></p>
+<ul>
+<li>客户端的请求写命令会被append追加到AOF缓冲区内；</li>
+<li>AOF缓冲区根据AOF持久化策略[always,everysec,no]将操作sync同步到磁盘的AOF文件中；</li>
+<li>AOF文件大小超过重写策略或手动重写时，会对AOF文件rewrite重写，压缩AOF文件容量；</li>
+<li>Redis服务重启时，会重新load加载AOF文件中的写操作达到数据恢复的目的；</li>
+</ul>
+<p>AOF 方式的一个好处，我们通过一个“场景再现”来说明。某同学在操作 redis 时，不小心执行了 FLUSHALL，导致 redis 内存中的数据全部被清空了，这是很悲剧的事情。不过这也不是世界末日，只要 redis 配置了 AOF 持久化方式，且 AOF 文件还没有被重写（rewrite），我们就可以用最快的速度暂停 redis 并编辑 AOF 文件，将最后一行的 FLUSHALL 命令删除，然后重启 redis，就可以恢复 redis 的所有数据到 FLUSHALL 之前的状态了。这就是 AOF 持久化方式的好处之一。但是如果 AOF 文件已经被重写了，那就无法通过这种方法来恢复数据了。</p>
+<p>虽然优点多多，但 AOF 方式也同样存在缺陷，比如在同样数据规模的情况下，AOF 文件要比 RDB 文件的体积大。而且 AOF 方式的恢复速度也要慢于 RDB 方式。</p>
+<h3 id="对比及使用">对比及使用</h3>
+<p>官方推荐两个都启用，如果对数据不敏感，可以选单独用RDB，如果对数据不敏感，可以选单独用RDB，如果只是做纯内存缓存，可以都不用。</p>
+<table>
+<thead>
+<tr>
+<th></th>
+<th>RDB</th>
+<th>AOF</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>定义</td>
+<td>在指定的时间间隔能对你的数据进行快照存储</td>
+<td>记录每次对服务器的写操作,当服务器重启的时候会重新执行这些命令来恢复原始的数据,AOF命令以redis协议追加保存每次写的操作到文件末尾</td>
+</tr>
+<tr>
+<td>优先级</td>
+<td>低</td>
+<td>高</td>
+</tr>
+<tr>
+<td>数据完整性</td>
+<td>易丢失</td>
+<td>不易丢失</td>
+</tr>
+<tr>
+<td>恢复数据速度</td>
+<td>较快</td>
+<td>较慢</td>
+</tr>
+<tr>
+<td>数据文件损坏</td>
+<td>不能修复</td>
+<td>可使用命令进行修复</td>
+</tr>
+<tr>
+<td>数据文件大小</td>
+<td>较小</td>
+<td>较大，但是可压缩</td>
+</tr>
+</tbody>
+</table>
+<h2 id="redis大key问题">Redis大key问题</h2>
+<p>所谓的大key问题是某个key的value比较大，所以本质上是大value问题.因为key往往是程序可以自行设置的，value往往不受程序控制，因此可能导致value很大。</p>
+<p>因为Redis是单线程的,单线程中请求任务的处理是串行的，前面完不成，后面处理不了，同时也导致分布式架构中内存数据和CPU的不平衡.所以大key问题最典型的就是阻塞线程，并发量下降，导致客户端超时，服务端业务成功率下降。</p>
+<p>大key问题一般是由于业务方案设计不合理,没有预见value的动态增长问题产生的.一直往value塞数据，没有删除机制，迟早要爆炸或数据没有合理做分片，将大key变成小key. 在线上一般通过集成<a href="https://www.redis.com.cn/clients.html">Redis可视化工具</a>,来发现和定位大key问题.</p>
+<p>解决大key问题,根据大key的实际用途可以分为两种情况：可删除和不可删除。如果发现某些大key并非热key就可以在DB中查询使用，则可以在Redis中删掉.</p>
+<ul>
+<li>
+<p>删除</p>
+<ol>
+<li>当Redis版本大于4.0时，可使用UNLINK命令安全地删除大Key，该命令能够以非阻塞的方式，逐步地清理传入的Key。</li>
+<li>当Redis版本小于4.0时，避免使用阻塞式命令KEYS，而是建议通过SCAN命令执行增量迭代扫描key，然后判断进行删除。</li>
+</ol>
+</li>
+<li>
+<p>不可删除</p>
+<ol>
+<li>当value是string时，比较难拆分，则使用序列化、压缩算法将key的大小控制在合理范围内，但是序列化和反序列化都会带来更多时间上的消耗。</li>
+<li>当value是string，压缩之后仍然是大key，则需要进行拆分，一个大key分为不同的部分，记录每个部分的key，使用 multi get 等操作实现事务读取。</li>
+</ol>
+</li>
+</ul>
+<h2 id="redis数据库双写一致性问题">Redis数据库双写一致性问题</h2>
+<p>你只要用缓存，就可能会涉及到缓存与数据库双存储双写，你只要是双写，就一定会有数据一致性的问题.</p>
+<p>一般来说，如果允许缓存可以稍微的跟数据库偶尔有不一致的情况，也就是说如果你的系统不是严格要求 “缓存+数据库” 必须保持一致性的话，最好不要做这个方案，即：读请求和写请求串行化，串到一个内存队列里去。</p>
+<p>串行化可以保证一定不会出现不一致的情况，但是它也会导致系统的吞吐量大幅度降低，用比正常情况下多几倍的机器去支撑线上的一个请求。</p>
+<p>最经典的Redis使用方案:</p>
+<ul>
+<li>读的时候，先读缓存，缓存没有的话，就读数据库，然后取出数据后放入缓存，同时返回响应;</li>
+<li>更新的时候，先更新数据库，然后再删除缓存;</li>
+</ul>
+<h3 id="场景1">场景1</h3>
+<p>先更新数据库，再删除缓存。如果删除缓存失败了，那么会导致数据库中是新数据，缓存中是旧数据，数据就出现了不一致</p>
+<p>解决思路:</p>
+<ul>
+<li>先删除缓存，再更新数据库。如果数据库更新失败了，那么数据库中是旧数据，缓存中是空的，那么数据不会不一致。因为读的时候缓存没有，所以去读了数据库中的旧数据，然后更新到缓存中。(删除缓存失败会导致程序运行终止的情况下)</li>
+<li>延时双删。依旧是先更新数据库，再删除缓存，唯一不同的是，我们把这个删除的动作，在不久之后再执行一次，比如 5s 之后。
+<blockquote>
+<p>延迟双删的主要思路为异步重试,一般会把重试的步骤放在MQ中进行不断尝试</p>
+</blockquote>
+</li>
+<li>订阅数据库变更日志。 我们可以通过工具（canal）订阅这个日志，拿到具体操作的数据，然后再根据这条数据，去删除对应的缓存。</li>
+</ul>
+<h3 id="场景2">场景2</h3>
+<p>并发,数据发生了变更，先删除了缓存，然后要去修改数据库，此时还没修改。一个请求过来，去读缓存，发现缓存空了，去查询数据库，查到了修改前的旧数据，放到了缓存中。随后数据变更的程序完成了数据库的修改</p>
+<blockquote>
+<p>这种场景一般只会在数据在并发的进行读写的时候，才可能会出现这种问题,如果说你的并发量很低的话，特别是读并发很低，每天访问量就 1 万次，那么很少的情况下，会出现刚才描述的那种不一致的场景</p>
+</blockquote>
+<p>解决思路: 当第二个请求进来的时候,第一个请求删除了缓存,正要去修改数据库,此时把第二个请求加入到一个队列中,让其等待第一个请求执行完毕,在从队列中获取第二个请求,让其执行.</p>
+<p>该解决方案，最大的风险点在于说，可能数据更新很频繁，导致队列中积压了大量更新操作在里面，然后读请求会发生大量的超时，最后导致大量的请求直接走数据库。 如果一个内存队列中可能积压的更新操作特别多，那么你就要加机器，让每个机器上部署的服务实例处理更少的数据，那么每个内存队列中积压的更新操作就会越少.</p>
+<p>粗略测算,如果一秒有 500 的写操作，如果分成 5 个时间片，每 200ms 就 100 个写操作，放到 20 个内存队列中，每个内存队列，可能就积压 5 个写操作。每个写操作性能测试后，一般是在 20ms 左右就完成，那么针对每个内存队列的数据的读请求，也就最多 hang 一会儿，200ms 以内肯定能返回了.</p>
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diff --git a/blog-site/public/posts/detailed/java-small-service/index.html b/blog-site/public/posts/detailed/java-small-service/index.html
new file mode 100644
index 00000000..0cbabbaa
--- /dev/null
+++ b/blog-site/public/posts/detailed/java-small-service/index.html
@@ -0,0 +1,1436 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>微服务治理详解 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="什么是微服务架构 In short， the microservice architectural style is an approach to developing a single application as a suite of small services， each running in its own process and communicating with lightweight mechanisms， often an HTTP resource API。 These services are built around business capabilities and independently deployable" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+	
+
+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af%e5%be%ae%e6%9c%8d%e5%8a%a1%e6%9e%b6%e6%9e%84">
+                    什么是微服务架构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ba%e4%bb%80%e4%b9%88%e8%a6%81%e4%bd%bf%e7%94%a8%e5%be%ae%e6%9c%8d%e5%8a%a1">
+                    为什么要使用微服务
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%8e%e5%8d%95%e4%bd%93%e6%9e%b6%e6%9e%84%e8%bf%81%e7%a7%bb%e5%88%b0%e5%be%ae%e6%9c%8d%e5%8a%a1%e6%9e%b6%e6%9e%84">
+                    从单体架构迁移到微服务架构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e6%b2%bb%e7%90%86">
+                    服务治理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e6%b2%bb%e7%90%86%e6%b2%bb%e7%9a%84%e6%98%af%e4%bb%80%e4%b9%88">
+                    服务治理治的是什么
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e6%b3%a8%e5%86%8c%e5%8f%91%e7%8e%b0">
+                    服务注册发现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e7%86%94%e6%96%ad%e9%99%8d%e7%ba%a7">
+                    服务熔断降级
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e7%bd%91%e5%85%b3">
+                    服务网关
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e8%b0%83%e7%94%a8">
+                    服务调用
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e8%b4%9f%e8%bd%bd">
+                    服务负载
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e9%85%8d%e7%bd%ae%e4%b8%ad%e5%bf%83">
+                    服务配置中心
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#springcloud%e4%bd%93%e7%b3%bb">
+                    SpringCloud体系
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#eureka">
+                    Eureka
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hystrix">
+                    Hystrix
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#spring-cloud-gateway">
+                    Spring Cloud Gateway
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#openfeign">
+                    OpenFeign
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#ribbon">
+                    Ribbon
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#springcloud-config">
+                    SpringCloud Config
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#springboot">
+                    SpringBoot
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#dubbo%e4%bd%93%e7%b3%bb">
+                    Dubbo体系
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#zookeeper">
+                    ZooKeeper
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#springcloud-alibaba%e4%bd%93%e7%b3%bb">
+                    SpringCloud Alibaba体系
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#nacos">
+                    Nacos
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#sentinel">
+                    Sentinel
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
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+            <div class="my_socials">
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+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
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+                        <h2 id="post_single_title">微服务治理详解</h2>
+                        <span id="post_page_title_date" class="date">2021.06.21</span>
+                        
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+                    <div class="post_content markdown"><h2 id="什么是微服务架构">什么是微服务架构</h2>
+<blockquote>
+<p>In short， the microservice architectural style is an approach to developing a single application as a suite of small services，
+each running in its own process and communicating with lightweight mechanisms， often an HTTP resource API。
+These services are built around business capabilities and independently deployable by fully automated deployment machinery。
+There is a bare minimum of centralized management of these services， which may be written in different programming languages and use different data storage technologies。 ——<a href="https://martinfowler.com/articles/microservices.html">James Lewis and Martin Fowler (2014)</a></p>
+</blockquote>
+<p>大意：简而言之，微服务体系结构风格是一种将单个应用程序开发为一套小型服务的方法，每个服务运行在自己的进程中，并与轻量级机制(通常是HTTP资源API)通信。
+这些服务是围绕业务功能构建的，可以通过全自动部署机制进行独立部署。对这些服务的集中管理是最低限度的，这些服务可能用不同的编程语言编写，并使用不同的数据存储技术。</p>
+<p>微服务是一种架构风格，将服务围绕业务功能拆分，一个应用拆分为一组小型服务，每个服务运行在自己的进程内，也就是可独立部署和升级，服务之间使用轻量级HTTP交互，可以由全自动部署机制独立部署，去中心化，服务自治。服务可以使用不同的语言、不同的存储技术。</p>
+<h2 id="为什么要使用微服务">为什么要使用微服务</h2>
+<p>说起微服务就不得不说微服务之前的单体应用，有对比才能看的出微服务对比之前的单体应用到底强在哪？为什么我们要抛弃单体应用？</p>
+<ul>
+<li>单体应用往往所有的功能打包在一个包里，包含了 DO/DAO，Service，UI等所有逻辑，如果要修改一部分代码就需要全部重新部署，所以改动影响大，风险高。微服务模式弥补了这个缺陷，它将应用合理的拆分，实现敏捷开发和快速部署。</li>
+<li>单体应用只能通过在负载均衡器后面放置整个应用程序的多个实例来进行水平扩展，如果想要扩展特定的程序，显然是不行的，则需要使用到微服务模式实现。</li>
+<li>因为单体应用所有的功能全部都达到一个包里面，所以耦合性比较强，对于程序员来说代码维护会收到影响，出现了什么问题也不太方便进行排查。</li>
+<li>如果没有正确的设计，单体应用的一部分失败可能会级联并导致整个系统崩溃。而这种情况可以使用微服务的熔断、降级的思想来解决。</li>
+</ul>
+<p>微服务虽然好处多多，但是缺点就是服务众多，不好管理，这也就是为什么要治理微服务，治理成本高，不利于维护系统，项目成本会升高，所以项目架构设计时应综合考量。</p>
+<p>建议设计的原则是业务驱动、设计保障、演进式迭代、保守治疗的方式。搞不清楚，有争议的地方先尽量不要拆，如果确实要拆，要经过业务分析后慎重设计，把真正相对独立的部分拆分出来，可以借鉴 <strong>DDD</strong> 的方式。拆了以后要观察微服务的接口是否稳定，针对业务需求的变更微服务的模块是否可以保持相对稳定，是否可以独立演进。</p>
+<blockquote>
+<p>DDD: Domain-driven design的简称，译为领域驱动设计，是一种通过将实现连接到持续进化的模型来满足复杂需求的软件开发方法。
+<br>
+核心思想：DDD其实是面向对象方法论的一个升华。无外乎是通过划分领域（聚合根、实体、值对象）、领域行为封装到领域对象（充血模式）、内外交互封装到防腐层、职责封装到对应的模块和分层，从而实现了高内聚低耦合。
+链接：<a href="https://blog.csdn.net/qq_31960623/article/details/119840131">https://blog.csdn.net/qq_31960623/article/details/119840131</a></p>
+</blockquote>
+<h2 id="从单体架构迁移到微服务架构">从单体架构迁移到微服务架构</h2>
+<p>重写代码，但是不要大规模重写代码，重写代码听起来很好但风险较大，如果大规模重写代码可能会导致程序出现各种各样的bug;(当你承担重建一套全新基于微服务的应用程序不需要使用时候，可以采用重写这种方法)</p>
+<p>逐步迁移单体应用的功能，独立出来形成新的微服务，同时需要与旧的单体应用集成，这可以保证系统的正常运行，单体式应用在整个架构中比例逐渐下降直到消失或者成为微服务架构一部分;</p>
+<p>虽然在逐步的迁移功能，但是也会有源源不断的需求需要开发，此时该停止让单体式应用继续变大，也就是说当开发新功能时不应该为旧单体应用添加新代码，应该是将新功能开发成独立微服务;</p>
+<p>一个巨大的复杂单体应用由成十上百个模块构成，每个都是被抽取对象。决定第一个被抽取模块一般都是挑战，一般最好是从最容易抽取的模块开始，这会让开发者积累足够经验，这些经验可以为后续模块化工作带来巨大好处。</p>
+<p>转换模块成为微服务一般很耗费时间，一般可以根据获益程度来排序，一般从经常变化模块开始会获益最大。一旦转换一个模块为微服务，就可以将其开发部署成独立模块，从而加速开发进程。比如，抽取一些消耗内存资源较大的代码，将其弄成一个服务，然后可以将其部署在大内存主机上。同样的，将对计算资源很敏感的算法应用抽取出来也是非常有益的，这种服务可以被部署在有很多 CPU 的主机上。
+有三种策略可以考虑：将新功能以微服务方式实现；将表现层与业务数据访问层分离；将现存模块抽取变成微服务。</p>
+<p>首先要将抽离的相关功能,封装成相关几个方法,几个类,几个包中;定义好模块和单体应用之间的几个大概的接口,从程序内部开始调用; 一旦完成相关的接口,也就将此模块转换成独立微服务。为了实现，必须写代码使得单体应用和微服务之间通过使用进程间通信机制的API来交换信息;服务和单体应用整合的API代码就成为了容灾层;</p>
+<p>然后,将抽离的功能,转化为独立的服务进行部署,将其整合成一个微服务基础框架; 每抽取一个服务，就朝着微服务方向前进一步，随着时间推移，单体应用将会越来越简单，用户就可以增加更多独立的微服务。</p>
+<h2 id="服务治理">服务治理</h2>
+<h3 id="服务治理治的是什么">服务治理治的是什么</h3>
+<p>摘自《微服务设计》:</p>
+<blockquote>
+<p>在进行城市交通规划之前首先要做的第一个事情是收集信息，要能够知道这个城市发生了什么，所以在各个路口需要安装采集探头，记录车来车往的信息。有了信息以后就需要对信息进行分析了，那么就需要可视化的图形界面，能够一眼就看出什么地方出了问题，通往哪个工厂的路坏了。发现了问题就要解决问题了，限制一下拥堵路段的流量，把去往一个公园的车辆导向到另外一个类似的公园。最后，如果把城市作为一个国家来考虑，那么每个进入这个城市的车辆都需要进行检查，看看有没有携带违禁品，最后给这些不熟悉道路的外地车规划路线。通过上面这个思考的过程，我们发现要对一个城市进行治理的时候，第一要采集信息，然后要能够对采集的信息进行监控和分析，最后根据分析的结果采取对应的治理策略。另外从整体安全的角度考虑还需要一个守门人</p>
+</blockquote>
+<p>我们也用同样的思路来思考服务治理，网关就是整个整体的守门人，日志采集，追踪工具，服务注册发现都是用来采集信息的，然后需要监控平台来展现这些采集的信息，并进行监控和分析。
+最后根据分析的结果采取治理策略，有的服务快撑不住了要限流，有的服务坏了要熔断，并且还能够及时的调整这些服务的配置。</p>
+<p><img alt="分布式架构-011" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-011.png"></p>
+<h3 id="服务注册发现">服务注册发现</h3>
+<p>服务注册与发现是微服务架构中的核心概念。在微服务架构中，服务数量众多，服务间通信变得尤为重要。为了实现动态的服务间通信，每个服务都需要将自己的信息注册到注册中心，以便其他服务能够发现并调用。</p>
+<ul>
+<li>服务注册：服务提供者在启动时将自己的信息（如IP地址、端口号等）注册到注册中心。</li>
+<li>服务发现：服务消费者从注册中心查询所需服务的地址信息，实现动态调用。</li>
+</ul>
+<p>当服务器启动的时候，会把当前自己服务器的信息，比如：服务地址通讯地址等，以别名方式注册到注册中心上。另一方消费者服务提供者，以该别名的方式去注册中心上获取到实际的服务通讯地址，然后再实现本地RPC调用。
+RPC远程调用框架核心设计思想在于注册中心，因为使用注册中心管理每个服务与服务之间的一个依赖关系。在任何RPC远程框架中，都会有一个注册中心存放服务地址相关信息。</p>
+<h3 id="服务熔断降级">服务熔断降级</h3>
+<p>由于分布式架构中应用程序依赖关系可能非常多，每个依赖关系在某些时候将不可避免地失败，针对服务调用失败，为了缩小调用失败的影响，引入了服务熔断降级的思想。</p>
+<p>多个微服务之间调用的时候，假设微服务A调用微服务B和微服务C，微服务B和微服务C又调用其它的微服务，这就是所谓的“扇出”。如果扇出的链路上某个微服务的调用响应时间过长或者不可用，对微服务A的调用就会占用越来越多的系统资源，进而引起系统崩溃，所谓的“雪崩效应”。</p>
+<ul>
+<li>服务熔断：熔断机制是应对雪崩效应的一种微服务链路保护机制，当链路的某个微服务不可用或者响应时间太长时，将快速的返回设置好的提示信息。</li>
+<li>服务降级：服务降级一般是指在服务器压力剧增的时候，根据实际业务使用情况以及流量，对一些服务和页面有策略的不处理或者用一种简单的方式进行处理，从而释放服务器资源的资源以保证核心业务的正常高效运行。</li>
+</ul>
+<p>服务熔断是应对系统服务雪崩的一种保险措施，给出的一种特殊降级措施。而服务降级则是更加宽泛的概念，主要是对系统整体资源的合理分配以应对压力。服务熔断可看作特殊降级。</p>
+<h3 id="服务网关">服务网关</h3>
+<p>微服务背景下，一个系统被拆分为多个服务，但是像安全认证、流量控制、日志、监控等功能是每个服务都需要的，没有网关的话，我们就需要在每个服务中单独实现，这使得我们做了很多重复的事情并且没有一个全局的视图来统一管理这些功能。</p>
+<p><img alt="分布式架构-005" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-005.png"></p>
+<p>网关的角色是作为一个 API 架构，用来保护、增强和控制对于 API 服务的访问。API 网关是一个处于应用程序或服务（提供 REST API 接口服务）之前的系统，用来管理授权、访问控制和流量限制等，这样 REST API 接口服务就被 API 网关保护起来，对所有的调用者透明。
+因此，隐藏在 API 网关后面的业务系统就可以专注于创建和管理服务，而不用去处理这些策略性的基础设施。</p>
+<p>网关作用：</p>
+<ul>
+<li>作为所有API接口服务的请求接入点；</li>
+<li>作为所有后端业务服务的聚合点；</li>
+<li>实现安全、验证、路由、过滤、流量等策略；</li>
+<li>对所有API服务和策略进行统一管理；</li>
+</ul>
+<h3 id="服务调用">服务调用</h3>
+<p>服务调用可以说是微服务中最关键的，如果没有服务调用不会出现熔断降级、也不会出现服务负载、服务注册，分布式的服务治理可以说是围绕服务调用展开的。</p>
+<p>常见的服务之间的调用方式有两种：</p>
+<ul>
+<li>RPC远程过程调用：定义数据式，基于原生TCP通信，速度快，效率高。早期的wedservice，现在热门的dubbo，都是RPC的典型代表；</li>
+<li>Http：http其实是一种网络传输协议，基于TCP，规定了数据传输的格式。现在客户端浏览器与服务器端通信基本都是采用HTTP协议，也可以用来进行远程服务调用。缺点是消息封装臃肿，优势是对服务的提供和调用方没有任何技术限定，自由灵活，更符合为服务理念；</li>
+</ul>
+<p>现在热门的Rest风格，就可以通过HTTP协议来实现，如果公司全部采用Java技术栈，那么使用Dubbo作为微服务框架是一个不错的选择；如果公司的技术栈多样化，而且你更青睐Spring家族，那么SpringCloud搭建微服务是不二之选。</p>
+<h3 id="服务负载">服务负载</h3>
+<blockquote>
+<p>负载均衡，英文名称为Load Balance，其含义就是指将工作任务进行平衡、分摊到多个操作单元上进行运行，例如FTP服务器、Web服务器、企业核心应用服务器和其它主要任务服务器等，从而协同完成工作任务。</p>
+</blockquote>
+<p>当前服务与服务之间进行相互调用时，在分布式架构下应用都是集群部署，所以这个时候就需要进行服务负载，即将收到的请求分摊到对应的服务器上，从而达到系统的高可用。</p>
+<p>常见负载均衡算法：</p>
+<ul>
+<li>随机分配：随机选择一台服务器来分配任务。它保证了请求的分散性达到了均衡的目的。同时它是没有状态的不需要维持上次的选择状态和均衡因子。但是随着任务量的增大，它的效果趋向轮询后也会具有轮询算法的部分缺点；</li>
+<li>轮询分配：将任务分配给此时具有最小连接数的节点，因此它是动态负载均衡算法。一个节点收到一个任务后连接数就会加1，当节点故障时就将节点权值设置为0，不再给节点分配任务；</li>
+<li>最小连接分配：将任务分配给此时具有最小连接数的节点，因此它是动态负载均衡算法。一个节点收到一个任务后连接数就会加1，当节点故障时就将节点权值设置为0，不再给节点分配任务；</li>
+<li>hash分配：对请求中的关键信息进行hash计算，hash值相同的请求分配到同一台服务器，具体原理可查看HashMap分配原理；</li>
+<li>根据性能分配：根据服务器的响应时间来进行任务分配，优先将新任务分配给响应最快的服务器；</li>
+</ul>
+<h3 id="服务配置中心">服务配置中心</h3>
+<p>在分布式微服务意味着要将单体应用中的业务拆分成一个个子服务，每个服务的粒度相对较小，因此系统中会出现大量的服务。由于每个服务都需要必要的配置信息才能运行，所以一套集中式的、动态的配置管理设施是必不可少的。</p>
+<p>配置中心应运而生。配置中心，顾名思义，就是来统一管理项目中所有配置的系统。对于单机版，我们称之为配置文件；对于分布式集群系统，我们称之为配置中心。</p>
+<p>配置中心作用：</p>
+<ul>
+<li>统一管理不同环境、不同集群的配置；</li>
+<li>将配置与应用分离、解耦合；</li>
+<li>版本发布管理；</li>
+</ul>
+<h2 id="springcloud体系">SpringCloud体系</h2>
+<p>随着微服务模式的使用，服务之间的调用带来的问题有很多，例如：数据一致性、网络波动、缓存、事务等问题，针对这一系列的问题就要有对应的框架来解决，目前主流一站式微服务解决方案有<code>Spring Cloud</code>、<code>Spring Cloud Alibaba</code>。</p>
+<p><code>Spring Cloud</code>它并不是一个框架，而是很多个框架。它是分布式微服务架构的一站式解决方案，是多种微服务架构落地技术的集合体，俗称微服务全家桶。</p>
+<p><img alt="分布式架构-001" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-001.png"></p>
+<p><img alt="分布式架构-010" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-010.png"></p>
+<h3 id="eureka">Eureka</h3>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.jianshu.com/p/cb7fa0aa47a8">https://www.jianshu.com/p/cb7fa0aa47a8</a></li>
+</ul>
+<blockquote>
+<p>Eureka is a REST (Representational State Transfer) based service that is primarily used in the AWS cloud for locating services for the purpose of load balancing and failover of middle-tier servers。 We call this service， the Eureka Server。 Eureka also comes with a Java-based client component，the Eureka Client， which makes interactions with the service much easier。 The client also has a built-in load balancer that does basic round-robin load balancing。 &mdash;<a href="https://github.com/Netflix/eureka">https://github.com/Netflix/eureka</a></p>
+</blockquote>
+<p>大意：Eureka是一个REST (Representational State Transfer)服务，它主要用于AWS云，用于定位服务，以实现中间层服务器的负载平衡和故障转移，我们称此服务为Eureka服务器。Eureka也有一个基于java的客户端组件，Eureka客户端，这使得与服务的交互更加容易，同时客户端也有一个内置的负载平衡器，它执行基本的循环负载均衡。</p>
+<p>Eureka采用了Client / Server 的设计架构，提供了完整的服务注册和服务发现，可以和 Spring Cloud 无缝集成。Eureka Sever作为服务注册功能的服务器，它是服务注册中心。而系统中的其他微服务，使用Eureka的客户端连接到 Eureka Server并维持心跳连接。这样系统的维护人员就可以通过Eureka Server来监控系统中各个微服务是否正常运行。</p>
+<p><img alt="分布式架构-002" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-002.png"></p>
+<ul>
+<li>Eureka Server 提供服务注册服务；各个微服务节点通过配置启动后，会在EurekaServer中进行注册，这样EurekaServer中的服务注册表中将会存储所有可用服务节点的信息，服务节点的信息可以在界面中直观看到。</li>
+<li>Eureka Client 通过注册中心进行访问；它是一个Java客户端，用于简化Eureka Server的交互，客户端同时也具备一个内置的使用轮询负载算法的负载均衡器。在应用启动后，将会向Eureka Server发送心跳默认周期为30秒。如果Eureka Server在多个心跳周期内没有接收到某个节点的心跳，Eureka Server将会从服务注册表中把这个服务节点移除，默认90秒。
+<ul>
+<li>Service Provider：服务提供方，将自身服务注册到Eureka，从而使服务消费方能够找到；</li>
+<li>Service Consumer：服务消费方，从Eureka获取注册服务列表，从而能够消费服务；</li>
+</ul>
+</li>
+</ul>
+<p><strong>Eureka的自我保护机制：</strong></p>
+<p>默认情况下，如果Eureka Server在一定时间内（默认90秒）没有接收到某个微服务实例的心跳，Eureka Server将会移除该实例。但是当网络分区故障发生时，微服务与Eureka Server之间无法正常通信，而微服务本身是正常运行的，此时不应该移除这个微服务，所以引入了自我保护机制。</p>
+<blockquote>
+<p>自我保护模式正是一种针对网络异常波动的安全保护措施，使用自我保护模式能使Eureka集群更加的健壮、稳定的运行。</p>
+</blockquote>
+<p>如果在15分钟内超过85%的客户端节点都没有正常的心跳，那么Eureka就认为客户端与注册中心出现了网络故障，Eureka Server自动进入自我保护机制：</p>
+<ul>
+<li>Eureka Server不再从注册列表中移除因为长时间没收到心跳而应该过期的服务；</li>
+<li>Eureka Server仍然能够接受新服务的注册和查询请求，但是不会被同步到其它节点上，保证当前节点依然可用；</li>
+<li>当网络稳定时，当前Eureka Server新的注册信息会被同步到其它节点中；</li>
+</ul>
+<p>简而言之，某时刻某一个微服务不可用了，Eureka不会立刻清理，依旧会对该微服务的信息进行保存。所以Eureka属于<a href="https://blog.csdn.net/white_pure/article/details/119806058">AP</a>。</p>
+<h3 id="hystrix">Hystrix</h3>
+<p>当微服务系统的一个服务出现故障时，故障会沿着服务的调用链路在系统中疯狂蔓延，最终导致整个微服务系统的瘫痪，这就是“雪崩效应”。为了防止此类事件的发生，微服务架构引入了“断路器”的一系列服务容错和保护机制。</p>
+<blockquote>
+<p>&ldquo;断路器”本身是一种开关装置，当某个服务单元发生故障之后，通过断路器的故障监控（类似熔断保险丝)，向调用方返回一个符合预期的、可处理的备选响应（FallBack)，而不是长时间的等待或者抛出调用方无法处理的异常，这样就保证了服务调用方的线程不会被长时间、不必要地占用，从而避免了故障在分布式系统中的蔓延，乃至雪崩。</p>
+</blockquote>
+<p>&ldquo;断路器&quot;思想：<a href="https://martinfowler.com/bliki/CircuitBreaker.html">https://martinfowler.com/bliki/CircuitBreaker.html</a></p>
+<p>Spring Cloud Hystrix 是基于 Netflix 公司的开源组件 Hystrix 实现的，它提供了熔断器功能，能够有效地阻止分布式微服务系统中出现联动故障，以提高微服务系统的弹性。Spring Cloud Hystrix 具有服务降级、服务熔断、线程隔离、请求缓存、请求合并以及实时故障监控等强大功能。</p>
+<p>熔断机制是为了应对雪崩效应而出现的一种微服务链路保护机制。</p>
+<p>当微服务系统中的某个微服务不可用或响应时间太长时，为了保护系统的整体可用性，熔断器会暂时切断请求对该服务的调用，并快速返回一个友好的错误响应。这种熔断状态不是永久的，在经历了一定的时间后，熔断器会再次检测该微服务是否恢复正常，若服务恢复正常则恢复其调用链路。</p>
+<p><img alt="分布式架构-003" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-003.png"></p>
+<p>在熔断机制中涉及了三种熔断状态：</p>
+<ul>
+<li>熔断打开：请求不再进行调用当前服务，内部定时一般为MTTR(平均故障处理时间)，当打开时长达到所设的时长则进入半熔断状态；</li>
+<li>熔断半开：部分请求根据规则调用当前服务，如果请求成功且符合规则则认为当前服务恢复正常，关闭熔断；</li>
+<li>熔断关闭：熔断关闭不会对服务进行熔断；</li>
+</ul>
+<p>Hystrix 实现服务熔断的步骤如下：</p>
+<ol>
+<li>当服务的调用出错率达到或超过 Hystix 规定的比率（默认为 50%）后，熔断器进入熔断开启状态。</li>
+<li>熔断器进入熔断开启状态后，Hystrix 会启动一个休眠时间窗，在这个时间窗内，该服务的降级逻辑会临时充当业务主逻辑，而原来的业务主逻辑不可用。</li>
+<li>当有请求再次调用该服务时，会直接调用降级逻辑快速地返回失败响应，以避免系统雪崩。</li>
+<li>当休眠时间窗到期后，Hystrix 会进入半熔断转态，允许部分请求对服务原来的主业务逻辑进行调用，并监控其调用成功率。</li>
+<li>如果调用成功率达到预期，则说明服务已恢复正常，Hystrix 进入熔断关闭状态，服务原来的主业务逻辑恢复；否则 Hystrix 重新进入熔断开启状态，休眠时间窗口重新计时，继续重复第 2 到第 5 步。</li>
+</ol>
+<p><strong><a href="https://github.com/Netflix/Hystrix/wiki/How-it-Works#Flow">Hystrix工作流程</a>：</strong></p>
+<p><img alt="分布式架构-004" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-004.png"></p>
+<ol>
+<li>创建<code>HystrixCommand</code>或<code>HystrixObserableCommand</code>对象。</li>
+<li>命令执行:
+<ul>
+<li>其中<code>HystrixCommand</code>实现了下面前两种执行方式:
+<ul>
+<li><code>execute</code>：同步执行，从依赖的服务返回一个单一的结果对象或是在发生错误的时候抛出异常。</li>
+<li><code>queue</code>：异步执行，直接返回一个Future对象，其中包含了服务执行结束时要返回的单一结果对象。</li>
+</ul>
+</li>
+<li><code>HystrixObservableCommand</code>实现了后两种执行方式：
+<ul>
+<li><code>obseve()</code>：返回Observable对象，它代表了操作的多个结果，它是一个Hot Observable，不论“事件源”是否有“订阅者”，都会在创建后对事件进行发布，所以对于Hot Observable的每一个“订阅者”都有可能是从“事件源”的中途开始的，并可能只是看到了整个操作的局部过程。</li>
+<li><code>toObservable()</code>：同样会返回Observable对象，也代表了操作的多个结果，但它返回的是一个Cold Observable，没有“订间者”的时候并不会发布事件，而是进行等待，直到有“订阅者&quot;之后才发布事件，所以对于Cold Observable 的订阅者，它可以保证从一开始看到整个操作的全部过程。</li>
+</ul>
+</li>
+</ul>
+</li>
+<li>判断当前命令的请求缓存功能是被启用的，并且该命令缓存命中，那么缓存的结果会立即以Observable对象的形式返回。</li>
+<li>检查断路器是否为打开状态。如果断路器是打开的，那么Hystrix不会执行命令，而是转接到fallback处理逻辑(第8步)；如果断路器是关闭的，检查是否有可用资源来执行命令(第5步)。</li>
+<li>判断线程池/请求队列信号量是否占满。如果命令依赖服务的专有线程地和请求队列，或者信号量已经被占满，那么Hystrix也不会执行命令，而是转接到fallback处理理辑(第8步) 。</li>
+<li>Hystrix会根据我们编写的方法来决定采取什么样的方式去请求依赖服务:
+<ul>
+<li><code>HystrixCommand.run()</code>：返回一个单一的结果，或者抛出异常。</li>
+<li><code>HystrixObservableCommand.construct()</code>：返回一个Observable对象来发射多个结果，或通过onError发送错误通知。</li>
+</ul>
+</li>
+<li>Hystrix会将“成功”、“失败”、“拒绝”、“超时” 等信息报告给断路器，而断路器会维护一组计数器来统计这些数据。断路器会使用这些统计数据来决定是否要将断路器打开，来对某个依赖服务的请求进行&quot;熔断/短路&rdquo;。</li>
+<li>当命令执行失败的时候，Hystrix会进入fallback尝试回退处理，我们通常也称波操作为“服务降级”。而能够引起服务降级处理的情况有下面几种：
+<ul>
+<li>第4步∶当前命令处于“熔断/短路”状态，断路器是打开的时候。</li>
+<li>第5步∶当前命令的线程池、请求队列或者信号量被占满的时候。</li>
+<li>第6步∶<code>HystrixObsevableCommand.construct()</code>或<code>HytrixCommand.run()</code>抛出异常的时候。</li>
+</ul>
+</li>
+<li>当Hystrix命令执行成功之后，它会将处理结果直接返回或是以Observable的形式返回给调用方。</li>
+</ol>
+<h3 id="spring-cloud-gateway">Spring Cloud Gateway</h3>
+<p>Spring Cloud Gateway 属于 Spring Cloud 生态系统中的网关，其诞生的目标是为了替代老牌网关 Zuul。准确点来说，应该是 Zuul 1.x。Spring Cloud Gateway 起步要比 Zuul 2.x 更早。
+为了提升网关的性能，Spring Cloud Gateway 基于 Spring WebFlux 。Spring WebFlux 使用 Reactor 库来实现响应式编程模型，底层基于 Netty 实现同步非阻塞的 I/O。</p>
+<p><img alt="分布式架构-012" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-012.png"></p>
+<p>核心组件：</p>
+<ul>
+<li>Route - 路由是构建网关的基本模块，它由ID，目标URI，一系列的断言和过滤器组成，如断言为true则匹配该路由；</li>
+<li>Predicate - 断言参考的是Java8的<code>java.util.function。Predicate</code>，开发人员可以匹配HTTP请求中的所有内容，例如请求头或请求参数，如果请求与断言相匹配则进行路由；</li>
+<li>Filter - 过滤指的是Spring框架中GatewayFilter的实例，使用过滤器，可以在请求被路由前或者之后对请求进行修改；</li>
+</ul>
+<p><a href="https://spring.io/blog/2022/08/26/creating-a-custom-spring-cloud-gateway-filter">工作流程</a>：
+<img alt="分布式架构-013" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-013.png"></p>
+<ul>
+<li>路由判断：客户端的请求到达网关后，先经过 Gateway Handler Mapping 处理，这里面会做断言（Predicate）判断，看下符合哪个路由规则，这个路由映射后端的某个服务。</li>
+<li>请求过滤：然后请求到达 Gateway Web Handler，这里面有很多过滤器，组成过滤器链（Filter Chain），这些过滤器可以对请求进行拦截和修改，比如添加请求头、参数校验等等，有点像净化污水。然后将请求转发到实际的后端服务。这些过滤器逻辑上可以称作 Pre-Filters，Pre 可以理解为“在&hellip;之前”。</li>
+<li>服务处理：后端服务会对请求进行处理。</li>
+<li>响应过滤：后端处理完结果后，返回给 Gateway 的过滤器再次做处理，逻辑上可以称作 Post-Filters，Post 可以理解为“在&hellip;之后”。</li>
+<li>响应返回：响应经过过滤处理后，返回给客户端。</li>
+</ul>
+<p>客户端的请求先通过匹配规则找到合适的路由，就能映射到具体的服务。然后请求经过过滤器处理后转发给具体的服务，服务处理后，再次经过过滤器处理，最后返回给客户端。</p>
+<p>对于公司业务以 Java 为主要开发语言的情况下，Spring Cloud Gateway 通常是个不错的选择，其优点有：简单易用、成熟稳定、与 Spring Cloud 生态系统兼容、Spring 社区成熟等等。
+不过，Spring Cloud Gateway 也有一些局限性和不足之处， 一般还需要结合其他网关一起使用比如 OpenResty。
+并且，其性能相比较于 Kong 和 APISIX，还是差一些。如果对性能要求比较高的话，Spring Cloud Gateway 不是一个好的选择。</p>
+<h3 id="openfeign">OpenFeign</h3>
+<blockquote>
+<p>Feign is a declarative web service client。 It makes writing web service clients easier。 To use Feign create an interface and annotate it。 It has pluggable annotation support including Feign annotations and JAX-RS annotations。 Feign also supports pluggable encoders and decoders。 Spring Cloud adds support for Spring MVC annotations and for using the same HttpMessageConverters used by default in Spring Web。 Spring Cloud integrates Ribbon and Eureka， as well as Spring Cloud LoadBalancer to provide a load-balanced http client when using Feign。</p>
+</blockquote>
+<p>大意：Feign是一个声明式WebService客户端。使用Feign能让编写Web Service客户端更加简单。它的使用方法是定义一个服务接口然后在上面添加注解。Feign也支持可拔插式的编码器和解码器。Spring Cloud对Feign进行了封装，使其支持了Spring MVC标准注解和HttpMessageConverters。Feign可以与Eureka和Ribbon组合使用以支持负载均衡。</p>
+<p>Feign和OpenFeign:</p>
+<ul>
+<li>Feign是Spring Cloud组件中的一个轻量级RESTful的HTTP服务客户端Feign内置了Ribbon，用来做客户端负载均衡，去调用服务注册中心的服务。Feign的使用方式是:使用Feign的注解定义接口，调用这个接口，就可以调用服务注册中心的服务；</li>
+<li>OpenFeign是Spring Cloud在Feign的基础上支持了SpringMVC的注解，如@RequesMapping等等。OpenFeign的@Feignclient可以解析SpringMVc的@RequestMapping注解下的接口，并通过动态代理的方式产生实现类，实现类中做负载均衡并调用其他服务；</li>
+</ul>
+<p>通过使用<code>OpenFeign</code>可以使代码变得更加简洁，减轻程序员负担：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> // 伪代码
+</span></span><span class="line"><span class="cl"> @Component
+</span></span><span class="line"><span class="cl"> // 括号中，为在注册中心注册的服务名称
+</span></span><span class="line"><span class="cl"> @FeignClient(&#34;CLOUD-PAYMENT-SERVICE&#34;)
+</span></span><span class="line"><span class="cl"> public interface PaymentFeignService {
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">     @GetMapping(&#34;/payment/get/{id}&#34;)
+</span></span><span class="line"><span class="cl">     CommonResult&lt;Payment&gt; getPayment(@PathVariable(&#34;id&#34;) Long id);
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">     @PostMapping(&#34;/payment/timeout&#34;)
+</span></span><span class="line"><span class="cl">     String feignTimeoutTest();
+</span></span><span class="line"><span class="cl"> }
+</span></span></code></pre></div><p>openFeign工作原理：</p>
+<p><img alt="分布式架构-008" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-008.png"></p>
+<ol>
+<li>使用注解<code>@FeignClient</code>注册<code>FactoryBean</code>到IOC容器， 最终产生了一个虚假的实现类代理;</li>
+<li>使用Feign调用接口的地方，最终拿到的都是一个假的代理实现类；</li>
+<li>所有发生在代理实现类上的调用，都被转交给Feign框架，翻译成HTTP的形式发送出去，并得到返回结果，再翻译回接口定义的返回值形式；</li>
+</ol>
+<h3 id="ribbon">Ribbon</h3>
+<p>Spring Cloud Ribbon是基于Netflix Ribbon实现的一套客户端负载均衡的工具，是一个内置软件负载平衡器的进程间通信（远程过程调用）库。主要功能是提供客户端的软件负载均衡算法和服务调用。Ribbon客户端组件提供一系列完善的配置项，如连接超时、重试等。</p>
+<p>本地负载与服务端负载：</p>
+<ul>
+<li>Nginx是服务器负载均衡，客户端所有请求都会交给nginx，然后由nginx实现转发请求。即负载均衡是由服务端实现的；</li>
+<li>Ribbon是本地负载均衡，在调用微服务接口时候，会在注册中心上获取注册信息服务列表之后缓存到JVM本地，从而在本地实现RPC远程服务调用技术；</li>
+</ul>
+<p>Ribbon其实是一个软负载均衡的客户端组件，它可以和其他所需请求的客户端结合使用，例如与Eureka结合：</p>
+<p><img alt="分布式架构-007" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-007.png"></p>
+<p>消费方和服务方在注册中心注册服务，当消费方发起请求时，Ribbon会去注册中心寻找请求的服务名，即服务方集群，Ribbon默认负载算法会根据<code>接口第几次请求 % 服务器集群总数量</code>算出实际消费方服务器的位置，每次服务重启动后rest接口计数从1开始。</p>
+<p>模拟Ribbon默认负载均衡算法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public interface ILoadBalance {
+</span></span><span class="line"><span class="cl">    ServiceInstance instance(List&lt;ServiceInstance&gt; instances); 
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">@Component
+</span></span><span class="line"><span class="cl">public class MyLoadBalance implements ILoadBalance{
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    /**
+</span></span><span class="line"><span class="cl">     * 轮询索引
+</span></span><span class="line"><span class="cl">     */
+</span></span><span class="line"><span class="cl">    private final AtomicInteger index = new AtomicInteger(0);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    /**
+</span></span><span class="line"><span class="cl">     * 负载均衡算法：rest接口第几次请求数 % 服务器集群总数量 = 实际调用服务器位置下标，每次服务重启动后rest接口计数从1开始。
+</span></span><span class="line"><span class="cl">     * @param instances 服务器集群数量
+</span></span><span class="line"><span class="cl">     * @return 实际服务器的下标
+</span></span><span class="line"><span class="cl">     */
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public ServiceInstance instance(List&lt;ServiceInstance&gt; instances) {
+</span></span><span class="line"><span class="cl">        return instances.get(incrementAndGet() % instances.size());
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public final int incrementAndGet() {
+</span></span><span class="line"><span class="cl">        int current = 0;
+</span></span><span class="line"><span class="cl">        int next = 0;
+</span></span><span class="line"><span class="cl">        do {
+</span></span><span class="line"><span class="cl">            current = index.get();
+</span></span><span class="line"><span class="cl">            // 当最大数量超过 Integer。MAX_VALUE 归0
+</span></span><span class="line"><span class="cl">            next = current &gt;= 2147483647 ? 0 : current + 1;
+</span></span><span class="line"><span class="cl">        }while (!index.compareAndSet(current，next));
+</span></span><span class="line"><span class="cl">        return next;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private RestTemplate restTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private DiscoveryClient discoveryClient;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private ILoadBalance iLoadBalance;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> @GetMapping(&#34;/myLoadBalance&#34;)
+</span></span><span class="line"><span class="cl"> public String myLoadBalanceTest() {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     List&lt;ServiceInstance&gt; instances = discoveryClient.getInstances(&#34;CLOUD-PAYMENT-SERVICE&#34;);
+</span></span><span class="line"><span class="cl">     ServiceInstance instance = iLoadBalance.instance(instances);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     URI uri = instance.getUri();
+</span></span><span class="line"><span class="cl">     String finalUri = String.format(&#34;%s/%s&#34;， uri， PaymentConstant。PAYMENT_GETPORT_API);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     log.info(&#34;自定义负载均衡，请求地址：{}&#34;， finalUri);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     return restTemplate.getForObject(finalUri， String.class);
+</span></span><span class="line"><span class="cl"> }
+</span></span></code></pre></div><h3 id="springcloud-config">SpringCloud Config</h3>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.springcloud.cc/spring-cloud-config.html">https://www.springcloud.cc/spring-cloud-config.html</a></li>
+<li><a href="https://cloud.spring.io/spring-cloud-static/spring-cloud-config/2.2.1.RELEASE/reference/html">https://cloud.spring.io/spring-cloud-static/spring-cloud-config</a></li>
+</ul>
+<p>SpringCloud Config为微服务架构中的微服务提供集中化的外部配置支持，配置服务器为各个不同微服务应用的所有环境提供了一个中心化的外部配置。</p>
+<p><img alt="分布式架构-009" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-009.png"></p>
+<p><code>SpringCloud Config</code>是配置中心的一种，它分为服务端和客户端两部分：</p>
+<ul>
+<li>服务端也称为分布式配置中心，它是一个独立的微服务应用，用来连接配置服务器并为客户端提供获取配置信息，加密/解密信息等访问接口；Config-Server端集中式存储/管理配置文件，并对外提供接口方便Config-Client访问，接口使用HTTP的方式对外提供访问；</li>
+<li>客户端则是通过指定的配置中心来管理应用资源，以及与业务相关的配置内容，并在启动的时候从配置中心获取和加载配置信息配置服务器默认采用git来存储配置信息，这样就有助于对环境配置进行版本管理，并且可以通过git客户端工具来方便的管理和访问配置内容；</li>
+</ul>
+<p>使用<code>SpringCloud Config</code>非常简单，需要在服务端和客户端分别进行改造：</p>
+<ol>
+<li>引入依赖就不说了，首先将分布式中系统中的配置放到git或svn上，在服务端配置文件里配置好git或svn用户名密码、配置文件所在的分支及配置文件的目录，再将服务端启动类加上<code>@EnableConfigServer</code>注解，就大功告成了；</li>
+<li>放在git或svn上的配置文件名称要符合规则，才能通过配置中心访问得到该文件。一些常用的配置文件规则，其中，label：分支、profiles：环境(dev/test/prod)、application：服务名：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> ## http://127.0.0.1:3344/master/config-dev.yml
+</span></span><span class="line"><span class="cl"> 1. /{label}/{application}-{profile}.yml
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> ## http://127.0.0.1:3344/config-dev.yml
+</span></span><span class="line"><span class="cl"> 2. /{application}-{profile}.yml
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> ## http://127.0.0.1:3344/config/dev/master
+</span></span><span class="line"><span class="cl"> 3. /{application}/{profile}[/{label}]
+</span></span></code></pre></div></li>
+<li>在客户端也要引入依赖和进行相关配置：配置中心地址、分支名称、配置文件名称、环境，需要注意的是要将客户端模块下的<code>application.yml</code>文件改为<code>bootstrap.yml</code>，再将主启动类加上<code>@EnableEurekaClient</code>注解；
+<blockquote>
+<p>当配置客户端启动时，它绑定到配置服务器(通过spring.cloud.config.uri引导配置属性)，并使用远程属性源初始化Spring Environment。
+这种行为的最终结果是，所有想要使用Config Server的客户端应用程序都需要bootstrap.yml或一个环境变量</p>
+<p>applicaiton.yml是用户级的资源配置项，而bootstrap.yml是系统级的，优先级更加高，在加载配置时优先加载bootstrap.yml</p>
+</blockquote>
+</li>
+</ol>
+<p>当将<code>SpringCloud Config</code>客户端服务端都配置好之后，修改配置时会发现修改的配置文件不能实时生效；针对这个问题，可以将服务重启或者调用<code>actuator</code>的刷新接口使其生效，使用之前需要引入<code>actuator</code>的依赖：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> # 使用SpringCloud Config修改完配置后，调用刷新接口使客户端配置生效
+</span></span><span class="line"><span class="cl"> curl -X POST &#34;http://localhost:3355/actuator/refresh&#34;
+</span></span></code></pre></div><p>为了避免手动的调用刷新接口，可以使用<code>SpringCloud Bus</code>配合<code>SpringCloud Config</code>实现配置的动态刷新。</p>
+<h3 id="springboot">SpringBoot</h3>
+<p>长期以来Java的开发一直让人所诟病，项目开发复杂度极其高、项目的维护非常困难；即便使用了大量的开发框架，发现我们的开发也没少多少。为了解决让开发更佳简单，项目更容易管理，<code>SpringBoot</code>诞生了。
+<code>SpringBoot</code>是一个广泛用来构建Java微服务的框架，它基于Spring依赖注入框架来进行工作。</p>
+<p>官网地址：<a href="https://spring.io/projects/spring-boot">https://spring.io/projects/spring-boot</a></p>
+<blockquote>
+<p><code>SpringBoot</code>是由<code>Pivotal</code>团队提供的全新框架，其设计目的是用来简化新<code>Spring</code>应用的初始搭建以及开发过程。
+该框架使用了特定的方式来进行配置，从而使开发人员不再需要定义样板化的配置。<code>SpringBoot</code> 提供了一种新的编程范式，可以更加快速便捷地开发 <code>Spring</code> 项目，在开发过程当中可以专注于应用程序本身的功能开发，而无需在 <code>Spring</code> 配置上花太大的工夫。</p>
+</blockquote>
+<p><code>SpringBoot</code> 基于 <code>Sring4</code> 进行设计，继承了原有 <code>Spring</code> 框架的优秀基因。
+<code>SpringBoot</code> 准确的说并不是一个框架，而是一些类库的集合。
+<code>maven</code> 或者 <code>gradle</code> 项目导入相应依赖即可使用 <code>SpringBoot</code>，而无需自行管理这些类库的版本。</p>
+<p>特点：</p>
+<ul>
+<li>独立运行的 <code>Spring</code> 项目：
+<code>SpringBoot</code> 可以以 jar 包的形式独立运行，运行一个 <code>SpringBoot</code> 项目只需通过 <code>java–jar xx.jar</code> 来运行。</li>
+<li>内嵌 <code>Servlet</code> 容器：
+<code>SpringBoot</code> 可选择内嵌 <code>Tomcat</code>、<code>Jetty</code> 或者 <code>Undertow</code>，这样我们无须以 <code>war</code> 包形式部署项目。</li>
+<li>提供 <code>starter</code> 简化 <code>Maven</code> 配置：
+<code>Spring</code> 提供了一系列的 <code>starter</code> pom 来简化 <code>Maven</code> 的依赖加载，例如，当你使用了<code>spring-boot-starter-web</code> 时，会自动加入依赖包。</li>
+<li>自动配置 <code>Spring</code>：
+<code>SpringBoot</code> 会根据在类路径中的 jar 包、类，为 jar 包里的类自动配置 Bean，这样会极大地减少我们要使用的配置。当然，<code>SpringBoot</code> 只是考虑了大多数的开发场景，并不是所有的场景，若在实际开发中我们需要自动配置 <code>Bean</code>，而 <code>SpringBoot</code> 没有提供支持，则可以自定义自动配置。</li>
+<li>准生产的应用监控：
+<code>SpringBoot</code> 提供基于 <code>http、ssh、telnet</code> 对运行时的项目进行监控。</li>
+<li>无代码生成和 xml 配置：
+<code>SpringBoot</code> 的神奇的不是借助于代码生成来实现的，而是通过条件注解来实现的，这是 <code>Spring 4.x</code> 提供的新特性。<code>Spring 4.x</code> 提倡使用 Java 配置和注解配置组合，而 <code>SpringBoot</code> 不需要任何 xml 配置即可实现 <code>Spring</code> 的所有配置。</li>
+</ul>
+<h2 id="dubbo体系">Dubbo体系</h2>
+<p>Apache Dubbo 是一款易用、高性能的 WEB 和 RPC 框架，同时为构建企业级微服务提供服务发现、流量治理、可观测、认证鉴权等能力、工具与最佳实践。
+官网：<a href="https://cn.dubbo.apache.org/zh-cn/">https://cn.dubbo.apache.org/zh-cn/</a></p>
+<p>Dubbo 不光可以帮助我们调用远程服务，还提供了一些其他开箱即用的功能比如智能负载均衡。</p>
+<p>Dubbo工作原理:</p>
+<p>从下至上分为十层，各层均为单向依赖。左边淡蓝背景的为服务消费方使用的接口，右边淡绿色背景的为服务提供方使用的接口，位于中轴线上的为双方都用到的接口。</p>
+<p><img alt="分布式架构-014" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-014.png"></p>
+<ul>
+<li>config 配置层：Dubbo 相关的配置。支持代码配置，同时也支持基于 Spring 来做配置，以 ServiceConfig, ReferenceConfig 为中心</li>
+<li>proxy 服务代理层：调用远程方法像调用本地的方法一样简单的一个关键，真实调用过程依赖代理类，以 ServiceProxy 为中心。</li>
+<li>registry 注册中心层：封装服务地址的注册与发现。</li>
+<li>cluster 路由层：封装多个提供者的路由及负载均衡，并桥接注册中心，以 Invoker 为中心。</li>
+<li>monitor 监控层：RPC 调用次数和调用时间监控，以 Statistics 为中心。</li>
+<li>protocol 远程调用层：封装 RPC 调用，以 Invocation, Result 为中心。</li>
+<li>exchange 信息交换层：封装请求响应模式，同步转异步，以 Request, Response 为中心。</li>
+<li>transport 网络传输层：抽象 mina 和 netty 为统一接口，以 Message 为中心。</li>
+<li>serialize 数据序列化层：对需要在网络传输的数据进行序列化。</li>
+</ul>
+<h3 id="zookeeper">ZooKeeper</h3>
+<p>Dubbo是个微服务整体架构的框架，提供的功能包括服务注册发现，远程调用，监控等等，对标的项目大概是spring cloud。Dubbo的服务发现模块基于zookeeper实现。</p>
+<p>ZooKeeper 是一个开源的分布式协调服务，它的设计目标是将那些复杂且容易出错的分布式一致性服务封装起来，构成一个高效可靠的原语集，并以一系列简单易用的接口提供给用户使用。</p>
+<ul>
+<li>ZooKeeper 本身就是一个分布式程序（只要半数以上节点存活，ZooKeeper 就能正常服务）。</li>
+<li>为了保证高可用，最好是以集群形态来部署 ZooKeeper，这样只要集群中大部分机器是可用的（能够容忍一定的机器故障），那么 ZooKeeper 本身仍然是可用的。</li>
+<li>ZooKeeper 将数据保存在内存中，这也就保证了 高吞吐量和低延迟（但是内存限制了能够存储的容量不太大，此限制也是保持 znode 中存储的数据量较小的进一步原因）。</li>
+<li>ZooKeeper 是高性能的。 在“读”多于“写”的应用程序中尤其地明显，因为“写”会导致所有的服务器间同步状态。（“读”多于“写”是协调服务的典型场景。）ZooKeeper 有临时节点的概念。</li>
+<li>当创建临时节点的客户端会话一直保持活动，瞬时节点就一直存在。而当会话终结时，瞬时节点被删除。持久节点是指一旦这个 znode 被创建了，除非主动进行 znode 的移除操作，否则这个 znode 将一直保存在 ZooKeeper 上。</li>
+<li>ZooKeeper 底层其实只提供了两个功能：① 管理（存储、读取）用户程序提交的数据；② 为用户程序提供数据节点监听服务。</li>
+</ul>
+<h2 id="springcloud-alibaba体系">SpringCloud Alibaba体系</h2>
+<p>Spring Cloud Alibaba 致力于提供微服务开发的一站式解决方案。此项目包含开发分布式应用服务的必需组件，方便开发者通过 Spring Cloud 编程模型轻松使用这些组件来开发分布式应用服务。</p>
+<h3 id="nacos">Nacos</h3>
+<p>Nacos 是一个 Alibaba 开源的、易于构建云原生应用的动态服务发现、配置管理和服务管理平台。
+使用 Spring Cloud Alibaba Nacos Discovery，可基于 Spring Cloud 的编程模型快速接入 Nacos 服务注册功能。</p>
+<h3 id="sentinel">Sentinel</h3>
+<p>随着微服务的流行，服务和服务之间的稳定性变得越来越重要。 Sentinel 以流量为切入点，从流量控制、熔断降级、系统负载保护等多个维度保护服务的稳定性。</p>
+<p>Sentinel 具有以下特征:</p>
+<ul>
+<li>丰富的应用场景： Sentinel 承接了阿里巴巴近 10 年的双十一大促流量的核心场景，例如秒杀（即突发流量控制在系统容量可以承受的范围）、消息削峰填谷、实时熔断下游不可用应用等。</li>
+<li>完备的实时监控： Sentinel 同时提供实时的监控功能。您可以在控制台中看到接入应用的单台机器秒级数据，甚至 500 台以下规模的集群的汇总运行情况。</li>
+<li>广泛的开源生态： Sentinel 提供开箱即用的与其它开源框架/库的整合模块，例如与 Spring Cloud、Dubbo、gRPC 的整合。您只需要引入相应的依赖并进行简单的配置即可快速地接入 Sentinel。</li>
+<li>完善的 SPI 扩展点： Sentinel 提供简单易用、完善的 SPI 扩展点。您可以通过实现扩展点，快速的定制逻辑。例如定制规则管理、适配数据源等。</li>
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+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e7%a1%80%e6%a6%82%e5%bf%b5">
+                    基础概念
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af%e4%ba%8b%e5%8a%a1">
+                    什么是事务
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%ac%e5%9c%b0%e4%ba%8b%e5%8a%a1">
+                    本地事务
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1">
+                    分布式事务
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e4%ba%a7%e7%94%9f%e5%9c%ba%e6%99%af">
+                    分布式事务产生场景
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e5%9f%ba%e7%a1%80%e7%90%86%e8%ae%ba">
+                    分布式事务基础理论
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cap%e7%90%86%e8%ae%ba">
+                    CAP理论
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%90%86%e8%a7%a3cap">
+                    理解CAP
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cap%e7%bb%84%e5%90%88%e6%96%b9%e5%bc%8f">
+                    CAP组合方式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#base%e7%90%86%e8%ae%ba">
+                    BASE理论
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-2pc">
+                    分布式事务解决方案-2PC
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af2pc">
+                    什么是2PC
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#xa%e6%96%b9%e6%a1%88">
+                    XA方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#seata%e6%96%b9%e6%a1%88">
+                    Seata方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-tcc">
+                    分布式事务解决方案-TCC
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%aftcc">
+                    什么是TCC
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-1">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-%e5%8f%af%e9%9d%a0%e6%b6%88%e6%81%af%e6%9c%80%e7%bb%88%e4%b8%80%e8%87%b4%e6%80%a7">
+                    分布式事务解决方案-可靠消息最终一致性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af%e5%8f%af%e9%9d%a0%e6%b6%88%e6%81%af%e6%9c%80%e7%bb%88%e4%b8%80%e8%87%b4%e6%80%a7">
+                    什么是可靠消息最终一致性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-2">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%ac%e5%9c%b0%e6%b6%88%e6%81%af%e8%a1%a8%e6%96%b9%e6%a1%88">
+                    本地消息表方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#rocketmq%e4%ba%8b%e5%8a%a1%e6%b6%88%e6%81%af%e6%96%b9%e6%a1%88">
+                    RocketMQ事务消息方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-%e6%9c%80%e5%a4%a7%e5%8a%aa%e5%8a%9b%e9%80%9a%e7%9f%a5">
+                    分布式事务解决方案-最大努力通知
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af%e6%9c%80%e5%a4%a7%e5%8a%aa%e5%8a%9b%e9%80%9a%e7%9f%a5">
+                    什么是最大努力通知
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-3">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e6%a1%881">
+                    方案1
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e6%a1%882">
+                    方案2
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88%e5%af%b9%e6%af%94">
+                    分布式解决方案对比
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">分布式事务详解</h2>
+                        <span id="post_page_title_date" class="date">2021.08.02</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="基础概念">基础概念</h2>
+<h3 id="什么是事务">什么是事务</h3>
+<p>什么是事务？举个例子：你去超市买东西，&ldquo;一手交钱，一手交货&quot;就是一个事务的例子。
+交钱和交货必须同时成功，事务才算成功，其中有一个环节失败，事务将会撤销所有已成功的活动。</p>
+<p>所以事务可以看作是一次重大的活动，它由不同的小活动组成，这些活动要么全部成功，要么全部失败。</p>
+<h3 id="本地事务">本地事务</h3>
+<p>在计算机系统中，更多的是通过关系型数据库来控制事务，这是利用数据库本身的事务特性来实现的，因此叫做数据库事务。
+由于应用程序主要靠关系型数据库来控制事务，而数据库通常和应用在同一个服务器上，所以基于关系型数据库的事务又叫做本地事务。</p>
+<p>数据库事务的四大特性：ACID：</p>
+<ul>
+<li>A（Atomic）：原子性，构成事务的所有操作，要么都执行完，要么全不执行，不可能出现部分成功部分失败的情况。</li>
+<li>C（Consistency）：一致性，在事务执行前后，数据库的一致性约束没有被破坏。比如：张三向李四转100元，转账前和转账后的数据正确状态这叫一致性，如果出现张三转100元，李四账户没有增加100元这就出现了数据错误，就没有达到一致性。</li>
+<li>I（Isolation）：隔离性，数据库中事务都是并发的，隔离性是指并发的两个事务的执行互不干扰，一个事务不能看到其他事务运行过程的中间状态。通过配置事务的隔离级别可以避免脏读、重复读等问题。</li>
+<li>D（Durability）：持久性，事务执行完毕后，该事务对数据的更改会被持久化到数据库，且不会被回滚。</li>
+</ul>
+<p>数据库事务在实现时，会将一次事务涉及的所有操作全部纳入到一个不可分割的执行单元，该执行单元中的所有操作要么都成功，要么都失败，只要其中任一操作执行失败，都将会导致事务回滚。</p>
+<h3 id="分布式事务">分布式事务</h3>
+<p>随着互联网的发展，软件系统由原来的单体应用转变为分布式应用。分布式系统会把一个应用系统拆分为多个可独立部署的程序，因此需要服务与服务之间的远程协作才能完成事务操作，这种分布式系统环境下由不同服务之间通过网络协作完成的事务被称为分布式事务。
+例如：用户注册送积分事务、创建订单减少库存、银行转账事务。</p>
+<p>本地事务与分布式事务理解：</p>
+<p>1.本地事务：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">begin transation;
+</span></span><span class="line"><span class="cl">// 1.本地数据库操作：张三减少金额
+</span></span><span class="line"><span class="cl">// 2.本地数据库操作：李四增加金额
+</span></span><span class="line"><span class="cl">commit transation;
+</span></span></code></pre></div><p>2.分布式事务：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">begin transation;
+</span></span><span class="line"><span class="cl">// 1.本地数据库操作：张三减少金额
+</span></span><span class="line"><span class="cl">// 2.远程调用：李四增加金额
+</span></span><span class="line"><span class="cl">commit transation;
+</span></span></code></pre></div><p>在<code>2.分布式事务</code>中如果李四增加金额成功，但是由于网络原因，远程调用并没有返回，此时本地事务提交失败就会回滚张三减少金额的操作，此时张三李四的金额就不一致了。</p>
+<p>因此在分布式架构的基础上，传统数据库事务就无法使用了，张三和李四的账户不在同一个数据库中甚至不在一个系统中，实现转账事务需要通过远程调用，由于网络的问题就会导致分布式事务的问题。</p>
+<h3 id="分布式事务产生场景">分布式事务产生场景</h3>
+<ol>
+<li>
+<p>最典型的是微服务架构，微服务之间通过远程调用完成事务操作。比如：订单微服务和库存微服务，下单的同时订单微服务请求库存微服务减少库存。简而言之，就是跨JVM进程产生的分布式事务。</p>
+</li>
+<li>
+<p>单体系统访问多个数据库实例，就会产生分布式事务。比如：用户和订单信息分别存储在两个MySQL中，用户管理系统删除用户信息，需要分别删除用户信息及用户的订单信息，由于数据分布在不同的数据库，就需要通过不同的数据库连接去操作数据，此时产生分布式事务。</p>
+</li>
+<li>
+<p>多个微服务访问同一个数据库实例。比如：订单微服务和库存微服务即使访问同一个数据库也会产生分布式事务，原因是跨JVM进程，两个微服务持有了不同的数据库连接进行数据库操作，此时产生分布式事务。</p>
+</li>
+</ol>
+<h2 id="分布式事务基础理论">分布式事务基础理论</h2>
+<p>分布式事务之所以叫做分布式事务，是因为提供服务的各个结点分布在不同的机器上，相互之间通过网络交互。不能因为有网络问题就导致整个系统无法提供服务，网络因素成了分布式事务的考量标准之一。因此，分布式事务需要更进一步的理论支持。</p>
+<h3 id="cap理论">CAP理论</h3>
+<p>CAP是Consistency、Availability、Partition tolerance三个词语的缩写，分别表示一致性、可用性、分区容忍性。</p>
+<h4 id="理解cap">理解CAP</h4>
+<p>为了方便对CAP理论的理解，结合电商系统中的一些业务场景来理解CAP；如下图是商品信息管理的执行流程：</p>
+<p><img alt="分布式事务-001" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-001.png"></p>
+<p>整体执行流程：</p>
+<ul>
+<li>商品服务请求主数据库写入商品信息（增、删、改）</li>
+<li>主数据库向商品服务响应写入成功</li>
+<li>商品服务请求从数据库获取商品信息</li>
+</ul>
+<p><strong>C-Consistency：</strong>
+一致性是指写操作后的读操作可以读取到最新的数据状态，当数据分布在多个结点上，从任意结点读取到的数据都是最新状态。</p>
+<p>上图中，商品的信息的读写要满足一致性就是要实现如下目标：</p>
+<ul>
+<li>商品服务写入主数据库成功，则向从数据查询新数据也成功</li>
+<li>商品服务写入主数据库失败，则向从数据查询新数据也失败</li>
+</ul>
+<p>这里一致性指的就是主从数据库数据的一致性。</p>
+<p>如何实现一致性：</p>
+<ul>
+<li>写入主数据库后要将数据<strong>同步</strong>到从数据库</li>
+<li>写入主数据库后，在向从数据库同步期间要将从数据库数据锁定，待同步完成后在释放锁，以免在新数据写入成功之后，向从数据库查询到旧数据库的数据</li>
+</ul>
+<p>分布式系统一致性的特点：</p>
+<ul>
+<li>由于存在数据库同步的过程中，写操作的响应会有一定的延迟</li>
+<li>为了保证数据一致性会对资源暂时锁定，待数据同步完成后释放锁定的资源</li>
+</ul>
+<p><strong>A-Availability:</strong>
+可用性是指任何事务操作都可以获得响应结果，且不会出现响应超时或响应错误。</p>
+<p>上图中，商品信息的读取满足可用性就是要实现如下目标：</p>
+<ul>
+<li>从数据库接收到数据查询的请求则立即能够响应数据的查询结果</li>
+<li>从数据库不允许出现响应超时或响应错误的情况</li>
+</ul>
+<p>如何实现可用性：</p>
+<ul>
+<li>写入主数据库后要将数据数据同步到从数据库</li>
+<li>由于要保证从数据库的可用性，不可将从数据库中的资源进行锁定</li>
+<li>即使数据还没有从主数据库同步过来，从数据库也要返回查询的数据，哪怕是旧数据，如果连旧数据也没有则可以按照约定返回一个默认信息，但不能返回错误或超时</li>
+</ul>
+<p>分布式系统可用性的特点：</p>
+<ul>
+<li>所有请求都要有响应，且不会出现响应超时或响应错误</li>
+</ul>
+<p><strong>P-Partition tolerance:</strong>
+分布式系统的各个结点部署在不同的子网，这就是网络分区，不可避免的会出现由于网络问题而导致结点之间的通信失败，此时仍可以对外提供服务，这就是分区容忍性。</p>
+<p>上图中，商品信息的读写满足分区容忍性就是要实现如下目标：</p>
+<ul>
+<li>主数据库向从数据库同步数据失败，不影响读写操作</li>
+<li>其中一个结点挂掉不影响另外一个结点提供服务</li>
+</ul>
+<p>如何实现分区容忍性：</p>
+<ul>
+<li>尽量使用异步取代同步操作，例如使用异步的方法将数据从数据库同步到从数据库，这样的结点之间才能有效的解耦合</li>
+<li>添加从数据库结点，其中一个从数据结点挂掉其他从结点来提供服务</li>
+</ul>
+<p>分布式分区容忍性特点：</p>
+<ul>
+<li>分区容忍性是分布式系统具备的基本的能力</li>
+</ul>
+<h4 id="cap组合方式">CAP组合方式</h4>
+<p>在所有分布式事务场景中不会同时具备CAP三个特征，因为在具备了P的前提下C和A是不能共存的。</p>
+<p>例如，下图满足了P分区容忍性</p>
+<p><img alt="分布式事务-001" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-001.png"></p>
+<p>上图分区容忍性含义：</p>
+<ul>
+<li>主数据库通过网络向从数据库同步数据，可以认为是主从数据库部署在不同的网络分区，通过网络进行交互</li>
+<li>当主数据库和从数据库之间网络出现问题，不影响主数据库和从数据库对外提供服务</li>
+<li>其中一台结点挂掉后，不影响另外一个结点对外提供服务</li>
+</ul>
+<p>在分区容忍性存在的前提下，一致性和可用性存在矛盾：</p>
+<ul>
+<li>如果要实现 <strong>(C)一致性</strong> ,则必须保证数据一致性，在数据同步的时候防止向从数据库查询不一致的数据则需要将从数据库数据锁定，待同步完成后解锁，如果同步失败，从数据库必须要返回错误信息或者超时信息。</li>
+<li>如果要实现 <strong>(A)可用性</strong> 则必须保证数据可用性，即不管任何时候都可以向从数据库查询数据，且不会响应超时信息或错误信息。</li>
+</ul>
+<p>在分布式的环境下，一致性和可用性只能存在一种，即AP、CP。</p>
+<ul>
+<li>AP：放弃一致性，追求分区容忍性和可用性。这是很多分布式系统设计时的选择。</li>
+<li>CP：放弃可用性，追求一致性和分区容忍性。zookeeper就是一个追求强一致性的例子；例如，跨行转账，一次转账请求需要等待双方银行都完成整个事务才算完成。</li>
+</ul>
+<p>如果不在分布式的环境下，一致性和可用性其实是不矛盾的：</p>
+<ul>
+<li>CA：放弃分区容忍性，即不进行分区，不考虑网络结点不通畅或者结点挂掉的情况，则可以实现一致性和可用性。那么系统将不是一个标准的分布式系统，最常用的关系型数据库就满足了CA。</li>
+</ul>
+<p>CAP是一个已经被证实的理论：一个分布式系统最多只能同时满足一致性、可用性、分区容忍性中的两种。它可以作为我们进行架构设计、技术选型的考量标准。对于大型互联网应用场景来说，结点众多、部署分散，而且现在的集群规模越来越大，所以结点故障、网络故障是常态，而且要保证服务可用性达到N个9（99.99..%）,并要达到良好的响应性能来提高用户的体验，因此一般都会做出以下选择：保证可用性和分区容忍性即AP，舍弃C，强一致性，保证最终一致性。</p>
+<h3 id="base理论">BASE理论</h3>
+<blockquote>
+<p>理解强一致性与最终一致性：
+CAP理论说明一个分布式系统最多能同时满足一致性、可用性、分区容忍性这三项中的两项；其中AP在实际应用中比较多，AP舍弃一致性，保证可用性和分区容忍性，但是在实际生产中很多场景都要实现一致性，比如前边的例子，主数据库向从数据库同步数据，即使不要一致性，但是最终也要将数据同步成功来保证数据一致，这种一致性和CAP中的一致性不同，CAP中的一致性要求在任何时间查询每个结点数据都必须保证一致，它强调的是一致性；
+但是最终一致性是允许可以在一段时间内每个结点数据不一致，但是经过一段时间后每个结点的数据必须一致，它强调的是数据的最终一致性。</p>
+</blockquote>
+<p>BASE是Basically Available(基本可用)、Soft state(软状态)、Eventually consistent(最终一致性) 这三个短语的缩写。
+BASE理论是对于CAP中AP的一个扩展，通过牺牲强一致性来获得可用性，当出现故障允许的部分不可用但要保证核心功能可用，允许数据在一段时间内是不一致的，但最终达到一致的状态。满足BASE理论的事务，我们称之为柔性事务。</p>
+<ul>
+<li>基本可用：分布式系统出现故障时，允许损失部分可用的功能，保证核心功能可用。例如，电商网站交易付款出现问题，商品依然可以正常浏览。</li>
+<li>软状态：由于不要求强一致性，所以BASE允许系统中存在<strong>中间状态（软状态）</strong>，这个状态不影响系统的可用性。例如，订单的&quot;支付中、数据同步中&quot;等状态，待数据最终一致后状态改为&quot;成功&quot;状态。</li>
+<li>最终一致性：最终一致是指经过一段时间后，所有的结点数据将会达到一致。例如，订单的&quot;支付中&quot;状态，最终会变为&quot;支付成功&quot;或&quot;支付失败&rdquo;，使订单状态与交易结果达成一致，但需要一定的时间等待。</li>
+</ul>
+<h2 id="分布式事务解决方案-2pc">分布式事务解决方案-2PC</h2>
+<p>针对不同的分布式场景常见的解决方案有2PC、TCC、可靠消息最终一致性、最大努力通知这几种。</p>
+<h3 id="什么是2pc">什么是2PC</h3>
+<p>2PC即两阶段提交协议，是将整个事务流程分为两个阶段：准备阶段（Prepare）、提交阶段（Commit），2是指两个阶段，P是准备阶段，C是提交阶段。</p>
+<p>举例，张三，李四聚餐，饭店老板要求先买单才能出票。张三李四都不愿请客，只能AA。只有张三和李四都付款，老板才能出票安排就餐。</p>
+<ul>
+<li>准备阶段：老板要求张三付款，张三付款；老板要求李四付款，李四付款。</li>
+<li>提交阶段：老板出票，两人拿票纷纷入座就餐。</li>
+</ul>
+<p>例子中形成了一个事务，若张三或李四其中一人拒绝付款，或者钱不够，老板都不会出票，并且把已收的钱退回。</p>
+<p>整个事务过程由<strong>事务管理器</strong>和参与者组成，老板就是事务管理器，张三、李四就是事务参与者，事务管理器负责抉择整个分布式事务的提交和回滚，事务参与者负责自己的本地事务提交和回滚。</p>
+<p>在计算机中部分关系型数据库如oracle、mysql支持两阶段提交协议：</p>
+<ol>
+<li>准备阶段：事务管理器给每个参与者发送Prepare消息,每个数据库参与者执行本地事务，并写本地的Undo/Redo日志，此时事务还没有提交。</li>
+</ol>
+<blockquote>
+<p>Undo日志是记录修改前的数据，用于数据库回滚；Redo日志是记录修改后的数据，用于提交事务后写入数据文件。</p>
+</blockquote>
+<ol start="2">
+<li>提交阶段：如果事务管理器收到了参与者的执行失败或超时的消息，那么直接给每个参与者发送回滚消息；否则，发送提交消息。参与者根据事务管理器的指令执行提交或回滚的操作，并释放事务处理过程中使用的锁资源。</li>
+</ol>
+<blockquote>
+<p>注意：必须在最后释放锁资源</p>
+</blockquote>
+<p>成功情况：
+<img alt="分布式事务-002" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-002.png"></p>
+<p>失败情况：
+<img alt="分布式事务-003" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-003.png"></p>
+<h3 id="解决方案">解决方案</h3>
+<p>2PC具体解决方案.</p>
+<h4 id="xa方案">XA方案</h4>
+<p>2PC的传统方案是在数据库层面实现的,如:oracle、mysql都支持2PC协议，为了统一标准减少行业内不必要的对接成本，需要制定标准化的处理模型即接口标准，国际开放标准组织OpenGroup定义了分布式处理模型DTP(<code>Distributed Transaction Processing Reference Model</code>)。</p>
+<p>DTP模型定义如下角色：</p>
+<ul>
+<li>AP：<code>Application Program</code>即应用程序，可以理解为使用分布式事务的程序。</li>
+<li>RM：<code>Resource Manager</code>即资源管理器，可理解为事务的参与者，一般情况是指一个数据库实例，通过资源管理器对该数据库进行控制，资源管理器控制这分支事务。</li>
+<li>TM：<code>Transacition Manager</code>即事务管理器，负责协调事务和事务管理，它控制着全局的事务，管理事务的生命周期，并协调各个资源管理器。</li>
+</ul>
+<blockquote>
+<p>全局事务是指分布式处理事务环境中，需要操作多个数据库共同完成一个动作，这个工作即是一个全局事务。</p>
+</blockquote>
+<p>以新用户注册送积分为例：
+<img alt="分布式事务-004" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-004.png"></p>
+<p>执行流程如下：</p>
+<ol>
+<li>
+<p>应用程序持有数据库和积分库两个数据源。</p>
+</li>
+<li>
+<p>应用程序通过事务管理器通知用户库的资源管理器新增用户，同时也通知积分库的资源管理器为该用户增加积分，资源管理器此时并未提交事务，此时用户和积分资源锁定。</p>
+</li>
+<li>
+<p>事务管理器收到执行回复，只要有一方失败则分别向其他方发起事务回滚，回滚完毕，资源释放锁；或事务管理器收到执行回复，全部成功，此时向所有资源管理器发起提交事务，提交完毕，资源释放。</p>
+</li>
+</ol>
+<p><strong>DTP模型定义TM和RM之间通讯的接口规范叫XA，简单理解为数据库提供的2PC接口协议，基于数据库的XA协议来实现2PC又称为XA方案。</strong></p>
+<p>以上三个角色之间的交互方式如下：</p>
+<ul>
+<li>TM向AP提供程序编程接口，AP通过TM提交或回滚事务</li>
+<li>TM交易中间件通过XA接口来通知RM数据库事务的开始、结束以及提交、回滚等</li>
+</ul>
+<p>整个2PC的事务管理流程涉及到三个角色：AP、RM、TM。AP指的是使用2PC分布式事务的应用程序；RM指的是资源管理器，它控制这分支事务；TM指的是事务管理器，它控制着全局事务。</p>
+<p>在准备阶段RM执行实际的业务操作，但是不提交事务，资源锁定；在提交阶段TM会接受RM在准备阶段的执行回复，只要任何一个RM执行失败，TM会通知所有的RM进行回滚操作，否则TM将会通知RM提交事务。提交阶段结束释放资源。</p>
+<p>XA方案存在的问题：</p>
+<ul>
+<li>需要本地数据库支持XA协议</li>
+<li>资源锁需要等到准备阶段和提交阶段结束才释放，性能较差</li>
+</ul>
+<h4 id="seata方案">Seata方案</h4>
+<p>Seata是由阿里中间件团队发起的开源项目Fescar，后更名为Seata，它是一个开源的分布式事务框架。</p>
+<p>传统2PC的问题在Seata中的到了解决，它通过对本地关系型数据库的分支事务的协调来驱动完成全局事务，是工作在应用层的中间件。主要优点是性能较好，且不长时间占用连接资源，它以高效并对业务0入侵的方式解决微服务场景下面临的分布式事务问题，目前提供AT模式（即2PC）和TCC模式的分布式事务解决方案。</p>
+<p><strong>Seata的设计思想:</strong></p>
+<p>Seata的设计目标其一是对业务零侵入，因此从业务无侵入的2PC入手，在传统方案2PC的基础上演进，并解决2PC方案面临的问题。</p>
+<p>Seata把一个分布式的事务理解为一个包含了若干分支事务的全局事务。全局事务的职责是协调其下管辖的分支事务达成一致，要么一起成功提交事务，要么一起回滚失败。此外，通常分支事务本身就是一个关系型数据库的本地事务。</p>
+<p><img alt="分布式事务-005" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-005.png"></p>
+<p>与传统2PC的模型类似，Seata定义了3个组件来协调分布式事务的处理过程：</p>
+<p><img alt="分布式事务-006" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-006.png"></p>
+<ul>
+<li>TM：<code>Transaction Manager</code>事务管理器，需要嵌入（jar包）应用程序中工作，负责开启一个全局事务，并最终向TC发起全局提交或全局回滚的指令。</li>
+<li>RM：<code>Resource Manager</code>资源管理器，控制分支事务，负责分支事务注册，状态回报，并接收事务调节器的指令，驱动分支事务的提交和回滚。</li>
+<li>TC：<code>Transaction Coordinator</code>事务协调器，它是独立的中间件，需要独立运行部署，它维护全局事务的运行状态，接收TM指令发起全局事务的提交与回滚，负责与RM通信协调各个分支事务的提交回滚。</li>
+</ul>
+<p>以新用户注册送积分举例：
+<img alt="分布式事务-007" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-007.png"></p>
+<p>具体执行流程：</p>
+<ol>
+<li>用户服务器的事务管理器向事务协调器申请开启一个全局事务，全局事务的创建成功并生成一个全局唯一XID。</li>
+<li>用户服务器的资源管理器向事务协调器注册分支事务，该分支事务在用户服务执行新增用户逻辑，并将其纳入XID对应全局事务的管辖。</li>
+</ol>
+<blockquote>
+<p>注意：在执行注册分支事务的时候，这里事务已经提交了，提交后可以释放资源，从而提升程序性能。</p>
+</blockquote>
+<ol start="3">
+<li>用户服务器执行分支事务，向用户表插入一条记录。</li>
+<li>逻辑执行到远程分布式调用积分服务时，XID在微服务调用链路的上下文中传播。积分服务的资源管理器向事务协调器注册了分支事务，该分支事务执行增加积分的逻辑，并将其纳入XID对应的全局事务的管辖。</li>
+<li>积分服务执行分支事务，向积分记录表插入一条记录，执行完毕后，返回用户服务。</li>
+<li>用户服务分支事务执行完毕。</li>
+<li>事务管理器向事务协调器针对XID的全局提交或者回滚决策。</li>
+<li>事务协调器调度XID下管辖的全部分支事务完成提交或回滚的请求。</li>
+</ol>
+<p>Seata实现2PC与传统2PC的差别：</p>
+<ul>
+<li>
+<p>架构方面，传统2PC方案的RM实际上是在数据库层，RM本质上就是数据库自身，通过XA协议实现，而Seata的RM则是以jar包的形式作为中间件层部署在应用程序这一侧的。</p>
+</li>
+<li>
+<p>两阶段提交方面，传统2PC无论第二阶段的决策是commit还是rollback，事务性资源的锁都要保持到第二阶段才释放。而Seata的做法是在第一阶段就将本地事务提交，这样可以省去第二阶段持有锁的时间，提高整体效率。</p>
+</li>
+</ul>
+<p><strong>Seata原理简介:</strong></p>
+<blockquote>
+<p>两阶段提交协议的演变：</p>
+<ul>
+<li>一阶段：业务数据和回滚日志记录在同一个本地事务中提交，释放本地锁和连接资源。</li>
+<li>二阶段：
+<ul>
+<li>提交异步化，非常快速地完成。</li>
+<li>回滚通过一阶段的回滚日志进行反向补偿。</li>
+</ul>
+</li>
+</ul>
+</blockquote>
+<p>一阶段：seata会拦截,解析SQL语义,找到SQL要更新的数据,在业务员数据更新前,将其保存为before image,随后执行业务SQL,在业务数据更新后,将其保存为after image,插入UNDO LOG回滚日志；提交前，向 TC 注册分支生成行锁。
+随后本地事务提交，将本地事务提交的结果上报给 TC，由TC协调。</p>
+<p><img alt="分布式事务-008" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-008.png"></p>
+<p>二阶段-提交：执行提交操作，说明SQL执行顺利，因业务SQL在一阶段已经提交至数据库，所以Seata框架只需将一阶段保存的快照数据和行锁删掉，完成数据清理即可。</p>
+<p><img alt="分布式事务-009" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-009.png"></p>
+<p>二阶段-回滚：要执行回滚操作，说明SQL执行不顺利，Seata需要回滚一阶段已经执行的业务SQL还原数据。回滚方式是用before image还原数据，但是在还原前还要校验脏写，对比数据库当前业务数据和after image。
+对比数据库当前业务数据和after image。</p>
+<p><img alt="分布式事务-010" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-010.png"></p>
+<h2 id="分布式事务解决方案-tcc">分布式事务解决方案-TCC</h2>
+<p>针对不同的分布式场景常见的解决方案有2PC、TCC、可靠消息最终一致性、最大努力通知这几种。</p>
+<h3 id="什么是tcc">什么是TCC</h3>
+<p>TCC是Try、Confirm、Cancel三个词语的缩写，TCC要求每个分支事务实现三个操作：预处理Try、确认Confirm、撤销Cancel。
+Try操作做业务检查及资源预留，Confirm做业务确认操作，Cancel实现一个与Try相反的操作，即回滚操作。TM首先发起所有分支事务的try操作，任何一个分支事务的try操作执行失败，TM将会发起所有分支事务的Cancel操作，若try操作全部成功，TM将发起所有分支事务的Confirm操作，其中Confirm或Cancel操作失败，TM会重试。</p>
+<p><img alt="分布式事务-011" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-011.png"></p>
+<p>分布式事务执行失败情况：</p>
+<p><img alt="分布式事务-012" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-012.png"></p>
+<p>TCC的三个阶段：</p>
+<ul>
+<li>Try阶段是做业务检查一致性及资源预留，此阶段仅是一个初步操作，它和后续的Confirm一起才能真正的构成一个完整的业务逻辑；</li>
+<li>Confirm阶段是确认提交，Try阶段所有的分支事务执行成功后开始执行Confirm。通常情况下，采用TCC则认为Confirm阶段是不会出错的。即：只要Try成功，Confirm一定成功。若Confirm阶段真的出错了，需要引入重试机制或进行人工处理；</li>
+<li>Cancel阶段是在业务执行错误需要回滚的状态下，执行分支事务的业务取消了，预留资源释放。通常情况下，采用TCC则认为Cancel阶段也是一定成功的。如果Cancel阶段真的出错了，需要引入重试机制或进行人工处理；</li>
+</ul>
+<p>TM事务管理器：</p>
+<ul>
+<li>TM事务管理器可以实现为独立的服务，也可以让全局事务发起方充当TM的角色，TM独立出来是为了成为公用的组件，为了考虑系统结构和软件复用。</li>
+</ul>
+<p>TM发起全局事务时生成全局事务记录，全局事务ID贯穿整个分布式事务调用链，用来记录事务上下文，追踪和记录状态，由于Confirm和Cancel失败需要进行重试或人工处理，因此实现为幂等，幂等性是指同一个操作无论请求多少次，其结果都相同。</p>
+<h3 id="解决方案-1">解决方案</h3>
+<p>Hmily是一个高性能分布式事务TCC开源框架。基于Java语言来开发（JDK1.8），支持Dubbo，Spring Cloud等RPC框架进行分布式事务。
+目前支持以下特性：</p>
+<ul>
+<li>支持嵌套事务(Nested transaction support);</li>
+<li>采用disruptor框架进行事务日志的异步读写，与RPC框架的性能毫无差别;</li>
+<li>支持SpringBoot-starter 项目启动，使用简单;</li>
+<li>RPC框架支持 : dubbo,motan,springcloud;</li>
+<li>本地事务存储支持 : redis,mongodb,zookeeper,file,mysql;</li>
+<li>事务日志序列化支持：java，hessian，kryo，protostuff;</li>
+<li>采用Aspect AOP 切面思想与Spring无缝集成，天然支持集群;</li>
+<li>RPC事务恢复，超时异常恢复等;</li>
+</ul>
+<p>Hmily利用AOP对参与分布式事务的本地方法与远程方法进行拦截处理，通过多方拦截，事务参与者能透明的调用到另一方的Try、Confirm、Cancel方法；
+传递事务上下文；并记录事务日志，酌情进行补偿，重试等。</p>
+<p>Hmily是一个轻量级的TCC事务框架不需要部署独立的事务协调服务，但需要提供一个数据库来进行日志存储。</p>
+<p>Hmily实现的TCC服务与普通的服务一样，只需要暴露一个接口，也就是它的Try业务。Confirm/Cancel业务逻辑，只是因为全局事务提交/回滚的需要才提供的，因此Confirm/Cancel业务只需要被Hmily TCC事务框架发现即可，不需要被调用它的其他业务服务所感知。</p>
+<blockquote>
+<p>要实现TCC协议，必须要实现三个方法：Try、Confirm、Cancel，其中最关键的方法是Try方法，Try方法是一个事务的起点。三个方法会由不同的线程来分别调用。</p>
+</blockquote>
+<p><strong>TCC需要注意三种异常处理：空回滚、幂等、悬挂：</strong></p>
+<ol>
+<li>
+<p><strong>空回滚</strong>:在没有调用TCC资源Try方法的情况下,调用了二阶段的Cancel方法，Cancel方法需要识别出这是一个空回滚，然后直接返回成功。
+<br>
+出现原因是当一个分支事务所在的服务器宕机或网络异常，分支事务调用记录为失败,这个时候其实是没有执行Try阶段，当故障恢复后，分布式事务进行回滚则会调用二阶段的Cancel方法，从而形成空回滚。
+<br>
+解决思路关键就是要标识这个空回滚,就是要知道try阶段是否已经执行了，如果执行了那就是正常回滚；如果没执行,那就是空回滚。可以在try阶段执行完毕后向表里插入一条记录进行标识，如果记录存在则try阶段执行了，如果不存在try阶段则未执行。</p>
+</li>
+<li>
+<p><strong>幂等</strong>:为了保证TCC二阶段提交重试机制不会引发数据不一致，要求TCC二阶段Try、Confirm、Cancel接口保证幂等性，这样不会重复使用或示释放资源。如果幂等控制没有做好，很有可能导致数据不一致等严重问题。</p>
+</li>
+<li>
+<p><strong>悬挂</strong>:悬挂就是对于一个分布式事务,其二阶段Cancel接口对比Try接口先执行。</p>
+</li>
+</ol>
+<p>出现原因是在RPC调用分支事务时,先注册分支事务，在执行RPC调用,如果此时RPC调用的网络发生错误，RPC超时后，TM就会通知RM回滚该分布式事务，可能回滚完成后,RPC请求才到达，然后执行，而一个try方法预留的业务资源，只有该分布式事务才能使用，该分布式事务第一阶段预留的业务资源也就在也没有人能够处理，对于这种情况就称为悬挂，即业务资源预留后没办法处理。</p>
+<h2 id="分布式事务解决方案-可靠消息最终一致性">分布式事务解决方案-可靠消息最终一致性</h2>
+<p>针对不同的分布式场景常见的解决方案有2PC、TCC、可靠消息最终一致性、最大努力通知这几种。</p>
+<h3 id="什么是可靠消息最终一致性">什么是可靠消息最终一致性</h3>
+<p>可靠消息最终一致性是指当事务发起方执行完本地事务后并发出一条消息，事务参与方（消息消费者）一定能接收到消息并成功处理事务，此方案强调的是只要消息发给事务参与方最终事务要达到一致。</p>
+<p>此方案利用消息中间件完成，事务发起方将消息发送给消息中间件，事务参与方从消息中间件接收消息，事务发起方和消息中间件之间，事务参与方和消息中间件之间都是通过网络进行通信，由于网络通信的不稳定会导致分布式事务问题。</p>
+<p><img alt="分布式事务-013" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-013.png"></p>
+<p>因此可靠消息最终一致性方案要解决几个问题：</p>
+<ul>
+<li><strong>本地事务与消息发送的原子性</strong> 即：事务发起方在本地事务执行成功后消息必须发出去，否则就丢弃消息。即实现本地事务和消息发送的原子性，要么都成功，要么都失败。本地事务与消息发送的原子性问题是实现可靠消息最终一致性方案的关键。</li>
+<li><strong>事务参与方接收消息的可靠性</strong> 事务参与方必须能够从消息队列接收消息，如果接收消息失败可以重复接收消息。</li>
+<li><strong>消息重复消费问题</strong> 由于网络存在问题，若某一个消费结点超时但是消费成功，此时消息中间件会重复投递此消息，就导致了消息重复消费问题。要解决消息重复消费问题就要实现事务参与方的方法的幂等性。</li>
+</ul>
+<h3 id="解决方案-2">解决方案</h3>
+<h4 id="本地消息表方案">本地消息表方案</h4>
+<p>本地消息表该方案最初是eBay提出，此方案的核心是通过本地事务保证数据业务操作和消息的一致性，然后通过定时任务将消息发送至消息中间件，待确认消息发送给消费方成功后在将消息删除。</p>
+<p>以用户注册送积分举例：用户服务负责添加用户，积分服务负责添加积分</p>
+<p><img alt="分布式事务-014" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-014.png"></p>
+<p>执行流程：</p>
+<ul>
+<li>用户注册，用户服务在本地新增用户和增加积分消息日志。用户表和消息表本地事务保持一致，这种情况下本地数据库操作与存储积分消息日志处于同一个事务中，本地数据库操作记录与记录消息日志操作具备原子性。</li>
+</ul>
+<p><strong>如何保证将消息发送给消息队列？</strong></p>
+<ul>
+<li>当消息已经写入到消息日志中去后，可以启动独立的线程，定时对消息日志表中的消息进行扫描并发送至消息中间件，在消息中间件反馈发送成功后删除该消息日志，否则等待定时任务下一周期重试。</li>
+</ul>
+<p><strong>如何保证消费者一定能消费到消息？</strong></p>
+<ul>
+<li>可以使用MQ的ACK机制即消息确认机制，消费这监听MQ，如果消费者接收到消息并且业务处理完成后想MQ发送ACK，此时说明消费者正常消费消息完成，MQ将不再向消费者推送消息，否则生产者会不断重试向消费者发送消息。</li>
+</ul>
+<p>由于消息会重复投递，积分服务的增加积分操作功能要实现幂等性。</p>
+<h4 id="rocketmq事务消息方案">RocketMQ事务消息方案</h4>
+<p>RocketMQ是阿里巴巴的分布式消息中间件，于2012年开源并在2017年正式称为apache的项目。ApacheRocketMQ4.3之后的版本正式支持事务消息，并为分布式事务提供了便利性支持。</p>
+<p>RocketMQ事务消息设计则主要是为了解决生产者端的消息发送与本地事务执行的原子性问题，RockerMQ设计中broker与生产者端的双向通信能力，使得broker天生可以作为一个事务协调者存在；RockerMQ的高可用机制以及可靠消息设计原则则为事务消息在系统发生异常时依然能够保证达成事务的最终一致性。</p>
+<p><img alt="分布式事务-015" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-015.png"></p>
+<p>执行流程：</p>
+<ol>
+<li>MQ的发起方会向MQ发送一条消息，MQ发起方会监听MQ是否响应；</li>
+<li>MQ收到该消息会响应消息发起方，代表发送给MQ成功；但是此时MQ并未发送消息给消费者；</li>
+<li>MQ发起方开始执行本地事务，执行完本地事务后，给MQ发送commit消息，此时MQ将该消息更改为可消费状态，消费者可以消费该消息；如果消费者执行本地事务失败，给MQ发送rollback消息，MQ会将该消息丢弃；</li>
+<li>消费者方利用MQ的ACK机制来保证消息一定被消费到；</li>
+</ol>
+<p><strong>注意：发起方与MQ之间的网络出现问题，但此时MQ里的消息不会一直存着；MQ服务会定回查消费者方本地事务状态（实现MQ事务回查接口），如果事务已经提交了消费者仍然可以接收到该消息，如果没有提交MQ则丢弃该消息。</strong></p>
+<h2 id="分布式事务解决方案-最大努力通知">分布式事务解决方案-最大努力通知</h2>
+<p>针对不同的分布式场景常见的解决方案有2PC、TCC、可靠消息最终一致性、最大努力通知这几种。</p>
+<h3 id="什么是最大努力通知">什么是最大努力通知</h3>
+<p>顾名思义，发起通知方通过一定机制最大努力的将业务处理结果通知到接收方。</p>
+<p>举个例子：</p>
+<p><img alt="分布式事务-016" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-016.png"></p>
+<p>账户系统调用充值系统接口，充值系统完成处理后向账户账户接口发起充值结果通知，如果通知失败则充值充值系统则按策略进行重复通知；账户系统接收到充值系统的通知后修改充值状态。如果账户系统未接受到通知，账户系统会主动调用充值系统接口进行结果查询。</p>
+<p>最大努力通知特点：</p>
+<ul>
+<li>有一定的消息重复通知机制。因接收方可能没有收到通知，此时要有一定的机制对消息重复通知。</li>
+<li>消息校对机制。如果发起方尽最大努力也没有通知到接收方，或接收方消费消息后要再次消费，此时可由接收方主动向通知方查询处理结果来满足需求。</li>
+</ul>
+<p><strong>最大努力通知与可靠消息一致性不同点</strong></p>
+<ul>
+<li>解决方案思想不同：
+<ul>
+<li>可靠消息一致性，发起通知方需要保证将消息发送出去，并且将消息发送到接收方，消息的可靠性关键由发起方来保证。</li>
+<li>最大努力通知，发起通知尽最大努力的将业务处理结果通知接收方，但是消息可能接收不到，此时需要接收通知方主动调用发起方的查询业务处理结果接口，通知的可靠性关键在接收方。</li>
+</ul>
+</li>
+<li>业务场景不同：
+<ul>
+<li>可靠消息一致性关注的是交易过程事务的一致性，以异步的方式完成交易。</li>
+<li>最大努力通知关注的是交易后的通知事务，即将交易结果可靠的通知出去。</li>
+</ul>
+</li>
+<li>技术解决方向不同：
+<ul>
+<li>可靠消息一致性要解决消息从发出到接收的一致性，即发出消息并且被接收到。</li>
+<li>最大努力通知无法保证发出到接收的一致性，只提供消息接收的可靠性机制。消息接收可靠机制指，最大努力的将通知发送给接收方，当消息无法被接收方接收时，由接收方主动查询该消息。</li>
+</ul>
+</li>
+</ul>
+<h3 id="解决方案-3">解决方案</h3>
+<p>通过对最大努力通知的理解，采用MQ的ack机制可以实现最大努力通知。</p>
+<h4 id="方案1">方案1</h4>
+<p><img alt="分布式事务-017" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-017.png"></p>
+<p>执行流程：</p>
+<ul>
+<li>发起通知方将通知发送给MQ；</li>
+<li>接收方监听MQ；</li>
+<li>接收通知方接收消息，业务处理完成回应ack，接收方若没有回应ack则MQ重复通知；</li>
+<li>如果消息没有发送出去可由接收方主动请求发起方查询业务结果接口，通过该接口校对消息的一致性；</li>
+</ul>
+<p>方案1中接收通知方MQ接口，即接收通知方监听MQ，此方案主要应用于应用与内部应用之间的通知。</p>
+<h4 id="方案2">方案2</h4>
+<p><img alt="分布式事务-018" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-018.png"></p>
+<p>交互流程：</p>
+<ul>
+<li>发起通知方将消息通知给MQ。使用可靠消息一致方案中的事务消息保证本地事务与消息的原子性，最终将通知先发给MQ；</li>
+<li>通知程序监听MQ，接收MQ消息。通知程序如果没有回应ack则MQ会重复通知；</li>
+<li>通知程序通过互联网接口协议调用接收通知方接口，完成通知。通知程序调用接收方接口成功就表示通知成功，即MQ消费成功，MQ将不再向通知程序投递消息；</li>
+<li>接收通知方可通过消息校对接口来校对消息的一致性；</li>
+</ul>
+<p>方案2中由于通知程序与MQ接口，通知程序监听MQ，收到MQ消息后由通知程序通过互联网接口协议调用接收通知方。此方案主要应用于外部应用之间的通知。</p>
+<h2 id="分布式解决方案对比">分布式解决方案对比</h2>
+<p><strong>2PC</strong>最大的诟病是一个阻塞协议。RM在执行分支事务后需要等待MT决定，此时服务会堵塞并锁定资源，由于其堵塞机制和最差时间复杂度较高，因此这种设计不能适应随着事务涉及的服务数量增多而扩展的需要，很难用于并发较高以及事务生命周期较长的分布式服务中。</p>
+<p>如果拿<strong>TCC</strong>的事务处理流程与2PC做比较，2PC通常都是在跨库的DB层面，而TCC则在应用层面的处理，需要通过业务逻辑来实现。这种分布式事务的实现方式优势在于，可以让应用自己定义数据库操作的粒度，使得降低锁冲突、提高吞吐量。不足之处是对应用的侵入性非常强，业务逻辑的每个分支都要实现try、confirm、cancel三个操作；此外实现难度也比较大，需要按照网络状态、系统故障的等不同失败原因进行不同回滚策略。</p>
+<p><strong>可靠消息最终一致性</strong>适合执行周期长且实时性要求不高的业务场景。引入消息机制后，同步的事务操作变为基于消息执行的异步操作，避免了分布式事务中同步堵塞操作的影响，并实现了两个服务之间的解耦。</p>
+<p><strong>最大努力通知</strong>是分布式事务中要求最低的一种，适用于一些最终一致性时间敏感度低的业务；允许发起通知方处理失败，在接收通知方收到失败通知后积极进行失败处理，无论发起通知方如何处理结果都不会影响到接收方的后续处理；发起通知方需要提供查询执行情况的接口，用于接收通知方校对结果。</p>
+<table>
+<thead>
+<tr>
+<th></th>
+<th>2PC</th>
+<th>TCC</th>
+<th>可靠消息最终一致性</th>
+<th>最大努力通知</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>一致性</td>
+<td>强一致性</td>
+<td>最终一致性</td>
+<td>最终一致性</td>
+<td>最终一致性</td>
+</tr>
+<tr>
+<td>吞吐量</td>
+<td>低</td>
+<td>中</td>
+<td>高</td>
+<td>高</td>
+</tr>
+<tr>
+<td>实现复杂度</td>
+<td>易</td>
+<td>难</td>
+<td>中</td>
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+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#atomicity%e5%8e%9f%e5%ad%90%e6%80%a7">
+                    Atomicity原子性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#consistency%e4%b8%80%e8%87%b4%e6%80%a7">
+                    Consistency一致性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#isolation%e9%9a%94%e7%a6%bb%e6%80%a7">
+                    Isolation隔离性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#durability%e6%8c%81%e4%b9%85%e6%80%a7">
+                    Durability持久性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e4%b8%ad%e7%9a%84%e6%97%a5%e5%bf%97">
+                    MySQL中的日志
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mvcc%e5%b9%b6%e5%8f%91%e6%8e%a7%e5%88%b6%e6%9c%ba%e5%88%b6">
+                    MVCC并发控制机制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%93%8d%e4%bd%9c%e4%ba%8b%e7%89%a9">
+                    操作事物
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e7%b4%a2%e5%bc%95">
+                    MySQL索引
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e6%95%b0%e6%8d%ae%e7%bb%93%e6%9e%84">
+                    索引数据结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e7%9a%84%e5%ae%9e%e7%8e%b0">
+                    索引的实现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#myisam%e7%b4%a2%e5%bc%95%e7%9a%84%e5%ae%9e%e7%8e%b0">
+                    MyISAM索引的实现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#innodb%e7%b4%a2%e5%bc%95%e7%9a%84%e5%ae%9e%e7%8e%b0">
+                    InnoDB索引的实现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e7%9a%84%e4%bc%98%e7%bc%ba%e7%82%b9">
+                    索引的优缺点
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e5%88%86%e7%b1%bb">
+                    索引分类
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%93%8d%e4%bd%9c%e7%b4%a2%e5%bc%95">
+                    操作索引
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%80%e5%b7%a6%e5%89%8d%e7%bc%80%e5%8c%b9%e9%85%8d%e5%8e%9f%e5%88%99">
+                    最左前缀匹配原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e8%a6%86%e7%9b%96">
+                    索引覆盖
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e5%bb%ba%e7%ab%8b%e5%8e%9f%e5%88%99">
+                    索引建立原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%81%bf%e5%85%8d%e7%b4%a2%e5%bc%95%e5%a4%b1%e6%95%88%e5%8e%9f%e5%88%99">
+                    避免索引失效原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e6%89%a7%e8%a1%8c%e8%ae%a1%e5%88%92">
+                    MySQL执行计划
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#idtable">
+                    id、table
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#select_type">
+                    select_type
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#type">
+                    type
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#possible_keyskey">
+                    possible_keys、key
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#key_len">
+                    key_len
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#ref">
+                    ref
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#rows">
+                    rows
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#extra">
+                    Extra
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e4%bc%98%e5%8c%96">
+                    MySQL优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#sql%e6%89%a7%e8%a1%8c%e8%bf%87%e7%a8%8b">
+                    SQL执行过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bc%98%e5%8c%96%e6%80%9d%e8%b7%af">
+                    优化思路
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e6%9f%a5%e6%85%a2sql">
+                    排查慢SQL
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%85%a2sql%e6%97%a5%e5%bf%97%e8%ae%be%e7%bd%ae">
+                    慢SQL日志设置
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9f%a5%e7%9c%8b%e6%85%a2sql%e6%97%a5%e5%bf%97">
+                    查看慢SQL日志
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a8%a1%e6%8b%9f%e6%95%b0%e6%8d%ae%e5%b9%b6%e5%88%86%e6%9e%90sql">
+                    模拟数据并分析SQL
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%a8%e5%b1%80%e6%9f%a5%e8%af%a2%e6%97%a5%e5%bf%97">
+                    全局查询日志
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#sql%e4%bc%98%e5%8c%96%e6%96%b9%e6%b3%95">
+                    SQL优化方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#exist%e5%92%8cin%e9%80%89%e6%8b%a9">
+                    exist和in选择
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#order-by%e4%bc%98%e5%8c%96">
+                    order by优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#sql%e4%bc%98%e5%8c%96%e6%a1%88%e4%be%8b">
+                    SQL优化案例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8d%95%e8%a1%a8%e4%bc%98%e5%8c%96">
+                    单表优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%a4%e8%a1%a8%e4%bc%98%e5%8c%96">
+                    两表优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e9%94%81%e6%9c%ba%e5%88%b6">
+                    MySQL锁机制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a1%a8%e9%94%81">
+                    表锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a1%8c%e9%94%81">
+                    行锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%bb%e7%bb%93">
+                    总结
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%ba%93%e5%88%86%e8%a1%a8">
+                    分库分表
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8b%86%e5%88%86%e6%96%b9%e6%a1%88">
+                    拆分方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e6%8d%ae%e8%bf%81%e7%a7%bb%e6%96%b9%e6%a1%88">
+                    数据迁移方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e8%a7%81%e5%88%86%e5%ba%93%e5%88%86%e8%a1%a8%e4%b8%ad%e9%97%b4%e4%bb%b6">
+                    常见分库分表中间件
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e8%80%83%e9%93%be%e6%8e%a5">
+                    参考链接
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
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+                <a href="http://localhost:1313/iblog/about/">关于</a>
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+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
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+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
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+                    <a id="export_doc" title="导出文档" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1689246982401" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="6825" width="16" height="16"><path d="M270.76864 608.32h180.8a31.68 31.68 0 0 0 0-62.976H270.76864a31.68 31.68 0 0 0 0 62.976zM271.34464 458.56h457.92a33.472 33.472 0 0 0 31.552-34.752 33.28 33.28 0 0 0-31.552-34.624H271.34464a34.816 34.816 0 0 0 0 69.376zM271.34464 293.504h457.92a33.344 33.344 0 0 0 31.552-34.688 33.216 33.216 0 0 0-31.552-34.624H271.34464a33.28 33.28 0 0 0-31.616 34.624 33.28 33.28 0 0 0 31.616 34.688z" p-id="6826" fill="#424242"></path><path d="M869.87264 0H153.77664A70.4 70.4 0 0 0 84.65664 70.912V953.6A69.952 69.952 0 0 0 153.77664 1024h370.048a32 32 0 0 0 0-63.68H147.12064V64h729.6v468.672a31.296 31.296 0 1 0 62.528 0V70.912A70.4 70.4 0 0 0 869.87264 0z" p-id="6827" fill="#424242"></path><path d="M482.16064 730.624h337.664L715.82464 625.216a28.864 28.864 0 0 1-7.936-28.736 29.184 29.184 0 0 1 20.608-21.184 29.632 29.632 0 0 1 29.12 8.128l174.784 177.216-174.784 176.96a29.184 29.184 0 0 1-49.728-13.312 29.248 29.248 0 0 1 8-28.8l103.936-105.344H482.16064a29.696 29.696 0 0 1-29.504-29.76 29.632 29.632 0 0 1 29.504-29.76z" p-id="6828" fill="#424242"></path></svg>
+                    </a>
+                </span>
+                <a  id="icon_more" title="更多" >
+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
+                </a>
+                <a  id="icon_less" class="display_none">
+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">MySQL详解</h2>
+                        <span id="post_page_title_date" class="date">2024.05.30</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="mysql介绍">MySQL介绍</h2>
+<p>MySQL 是一种关系型数据库，主要用于持久化存储我们系统中的一些数据。</p>
+<p>MySQL 如此流行的原因，主要具有下面这些优点：</p>
+<ul>
+<li>成熟稳定，功能完善。</li>
+<li>开源免费。</li>
+<li>文档丰富，既有详细的官方文档，又有非常多优质文章可供参考学习。</li>
+<li>开箱即用，操作简单，维护成本低。</li>
+<li>兼容性好，支持常见的操作系统，支持多种开发语言。</li>
+<li>社区活跃，生态完善。</li>
+<li>事务支持优秀， InnoDB 存储引擎默认使用 REPEATABLE-READ 并不会有任何性能损失，并且，InnoDB 实现的 REPEATABLE-READ 隔离级别其实是可以解决幻读问题发生的。</li>
+<li>支持分库分表、读写分离、高可用。</li>
+</ul>
+<h2 id="mysql逻辑架构">MySQL逻辑架构</h2>
+<p>主要分为：连接层，服务层，引擎层，存储层。</p>
+<p>客户端执行一条select命令的流程如下：</p>
+<p><img alt="MySqlSQL优化及锁机制-001" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-001.png"></p>
+<ul>
+<li>连接层：最上层是一些客户端和连接服务，包含本地sock通信和大多数基于客户端/服务端工具实现的类似于tcplip的通信。主要完成一些类似于连接处理、授权认证、及相关的安全方案。在该层上引入了线程池的概念，为通过认证安全接入的客户端提供线程。同样在该层上可以实现基于SSL的安全链接。服务器也会为安全接入的每个客户端验证它所具有的操作权限。</li>
+<li>服务层：第二层架构主要完成大多少的核心服务功能，如SQL接口，并完成缓存的查询，SQL的分析和优化及部分内置函数的执行。所有跨存储引擎的功能也在这一层实现，如过程、函数等。在该层，服务器会解析查询并创建相应的内部解析树，并对其完成相应的优化如确定查询表的顺序是否利用索引等，最后生成相应的执行操作。如果是select语句，服务器还会查询内部的缓存。如果缓存空间足够大，这样在解决大量读操作的环境中能够很好的提升系统的性能。</li>
+<li>引擎层：存储引擎层，存储引擎真正的负责了MySQL中数据的存储和提取，服务器通过API与存储引擎进行通信。不同的存储引擎具有的功能不同这样我们可以根据自己的实际需要进行选取，后面介绍MyISAM和InnoDB。</li>
+<li>存储层：数据存储层，主要是将数据存储在运行于裸设备的文件系统之上，并完成与存储引擎的交互。</li>
+</ul>
+<p>详细一点：</p>
+<p><img alt="MySQL基础架构" src="/iblog/posts/annex/images/essays/MySQL%E5%9F%BA%E7%A1%80%E6%9E%B6%E6%9E%84.png"></p>
+<ul>
+<li>连接器： 登录 MySQL 的时候需要身份权限认证。</li>
+<li>查询缓存： 执行查询语句的时候，会先查询缓存，不过在MySQL 8.0 版本后移除。</li>
+<li>分析器： 没有命中缓存的话，SQL 语句就会经过分析器，分析器说白了就是要先看你的 SQL 语句要干嘛，再检查你的 SQL 语句语法是否正确。</li>
+<li>优化器： 按照 MySQL 认为最优的方案去执行。</li>
+<li>执行器： 执行语句，然后从存储引擎返回数据。执行语句之前会先判断是否有权限，如果没有权限的话，就会报错。</li>
+<li>插件式存储引擎：主要负责数据的存储和读取，采用的是插件式架构，支持 InnoDB、MyISAM、Memory 等多种存储引擎。</li>
+</ul>
+<h2 id="mysql存储引擎">MySQL存储引擎</h2>
+<p>MySQL 核心在于存储引擎，MySQL 5.5.5 之前，MyISAM 是 MySQL 的默认存储引擎。5.5.5 版本之后，InnoDB 是 MySQL 的默认存储引擎。</p>
+<p>可以使用<code>show engines;</code>来查看。</p>
+<p><img alt="MySQL存储引擎" src="/iblog/posts/annex/images/essays/MySQL%E5%AD%98%E5%82%A8%E5%BC%95%E6%93%8E.png"></p>
+<table>
+<thead>
+<tr>
+<th>特性</th>
+<th>InnoDB</th>
+<th>MyISAM</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>事务支持</td>
+<td>支持</td>
+<td>不支持</td>
+</tr>
+<tr>
+<td>锁类型</td>
+<td>行级锁</td>
+<td>表级锁</td>
+</tr>
+<tr>
+<td>外键支持</td>
+<td>支持</td>
+<td>不支持</td>
+</tr>
+<tr>
+<td>崩溃恢复</td>
+<td>支持</td>
+<td>不支持</td>
+</tr>
+<tr>
+<td>数据存储</td>
+<td>表和索引存储在表空间中</td>
+<td>数据和索引存储在不同文件中</td>
+</tr>
+<tr>
+<td>全文索引</td>
+<td>MySQL 5.6及以上版本支持</td>
+<td>支持</td>
+</tr>
+<tr>
+<td>适用场景</td>
+<td>高并发和事务性要求高的应用</td>
+<td>读操作多、写操作少的应用</td>
+</tr>
+<tr>
+<td>性能</td>
+<td>写性能较好，读性能较好</td>
+<td>读性能高，写性能相对较差</td>
+</tr>
+<tr>
+<td>数据完整性</td>
+<td>高</td>
+<td>低</td>
+</tr>
+</tbody>
+</table>
+<p>选择 InnoDB 还是 MyISAM 取决于具体的应用需求。InnoDB 适合需要高并发、高数据完整性和事务支持的应用，而 MyISAM 适合读操作多、数据一致性要求不高的应用。</p>
+<p>尽管 MyISAM 在特定场景下仍然有其应用价值，但随着 MySQL 版本的更新和 InnoDB 性能的不断提升，大多数新应用和系统都选择了 InnoDB 作为主要存储引擎。
+遗留系统可能继续使用 MyISAM，但在新开发中，使用 InnoDB 已成为主流和最佳实践。</p>
+<h2 id="mysql事务">MySQL事务</h2>
+<p>什么是事务？举个例子：你去超市买东西，&ldquo;一手交钱，一手交货&quot;就是一个事务的例子。
+交钱和交货必须同时成功，事务才算成功，其中有一个环节失败，事务将会撤销所有已成功的活动。</p>
+<p>所以事务可以看作是一次重大的活动，它由不同的小活动组成，这些活动要么全部成功，要么全部失败。</p>
+<p>所有的存储引擎中只有 <code>InnoDB</code>、<code>NDB</code> 是事务性存储引擎，也就是说只有 <code>InnoDB</code>、<code>NDB</code> 支持事务。</p>
+<h3 id="事物的实现">事物的实现</h3>
+<p>只要对数据库稍有了解的人都知道事务具有 ACID 四个基本属性，而我们不知道的可能就是数据库是如何实现这四个属性的。
+简单来说，事务是通过事务日志来实现的，事务日志包括：redo log和undo log，下面详细介绍。</p>
+<h4 id="atomicity原子性">Atomicity原子性</h4>
+<p>要么全部都执行，要都不执行，不可能出现部分成功部分失败的情况，这是对原子性最简单的描述。</p>
+<p>事务其实和一个操作没有什么太大的区别，它是一系列的数据库操作（可以理解为 SQL）的集合，如果事务不具备原子性，那么就没办法保证同一个事务中的所有操作都被执行或者未被执行了，整个数据库系统就既不可用也不可信。</p>
+<p>想要保证事务的原子性，就需要在异常发生时，对已经执行的操作进行回滚，而在 MySQL 中，恢复机制是通过回滚日志（undo log）实现的。
+为了能够在发生错误时撤销之前的全部操作，需要将之前的操作都记录下来的，所以所有事务进行的修改都会先记录到这个回滚日志中，然后再对数据库中的对应行进行操作。</p>
+<p>回滚日志中保存的是逻辑日志，当回滚日志被使用时，它只会按照日志逻辑地将数据库中的修改撤销，相当于每一条 INSERT 都对应了一条 DELETE，每一条 UPDATE 也都对应一条相反的 UPDATE 语句。</p>
+<h4 id="consistency一致性">Consistency一致性</h4>
+<p>数据库对于 ACID 中的一致性的定义是这样的：如果一个事务原子地在一个一致地数据库中独立运行，那么在它执行之后，数据库的状态一定是一致的。</p>
+<p>对于这个概念，它的第一层意思就是对于数据完整性的约束，包括主键约束、引用约束以及一些约束检查等等，在事务的执行的前后以及过程中，不会违背对数据完整性的约束，所有对数据库写入的操作都应该是合法的，并不能产生不合法的数据状态。
+第二层意思其实是指逻辑上的对于开发者的要求，我们要在代码中写出正确的事务逻辑，比如银行转账，事务中的逻辑不可能只扣钱或者只加钱，这是应用层面上对于数据库一致性的要求。</p>
+<p>数据库 ACID 中的一致性，对事务的要求不止包含对数据完整性以及合法性的检查，还包含应用层面逻辑的正确。</p>
+<h4 id="isolation隔离性">Isolation隔离性</h4>
+<p>当事务都只是串行执行的时候是不会发生问题的，然而在实际工作中，并行执行的事务才是常态，并行执行下，可能出现非常复杂的问题：</p>
+<p>当 Transaction1 在执行的过程中对 <code>id = 1</code> 的用户进行了读写，但是没有将修改的内容进行提交或者回滚，在这时 Transaction2 对同样的数据进行了读操作并提交了事务；也就是说 Transaction2 是依赖于 Transaction1 的，当 Transaction1 由于一些错误需要回滚时，因为要保证事务的原子性，需要对 Transaction2 进行回滚，但是由于我们已经提交了 Transaction2，所以我们已经没有办法进行回滚操作。
+这种现象称为不可恢复安排，这种情况是我们难以接受的，如果相关的事物都回滚，这会造成性能上的巨大损失。</p>
+<p>其实这里可以使用互斥锁来解决这个问题，比如在MySQL中，想要对读取的数据进行更新时需要使用<code>SELECT ... FOR UPDATE</code>尝试获取对应行的互斥锁，保证不同事务可以正常运行。</p>
+<p>当多个事务同时并发执行时，事务的隔离性可能就会被违反，虽然单个事务的执行可能没有任何错误，但是从总体来看就会造成数据库的一致性出现问题，而串行虽然能够允许开发者忽略并行造成的影响，能够很好地维护数据库的一致性，但是却会影响事务执行的性能。
+所以为数据库提供什么样的隔离性，也就决定了数据库的性能以及可以达到什么样的一致性。</p>
+<p>在SQL标准中定义了四种数据库的事务的隔离级别：</p>
+<ul>
+<li>RAED UNCOMMITED：使用查询语句不会加锁，可能会读到未提交的行（Dirty Read）；</li>
+<li>READ COMMITED：只对记录加记录锁，而不会在记录之间加间隙锁，所以允许新的记录插入到被锁定记录的附近，所以再多次使用查询语句时，可能得到不同的结果（Non-Repeatable Read）；</li>
+<li>REPEATABLE READ：多次读取同一范围的数据会返回第一次查询的快照，不会返回不同的数据行，但是可能发生幻读（Phantom Read）；</li>
+<li>SERIALIZABLE：InnoDB 隐式地将全部的查询语句加上共享锁，解决了幻读的问题。最高的隔离级别，完全服从 ACID 的隔离级别，所有的事务依次逐个执行，这样事务之间就完全不可能产生干扰；</li>
+</ul>
+<p>从 <code>RAED UNCOMMITED</code> 到 <code>SERIALIZABLE</code>，随着事务隔离级别变得越来越严格，每个事务的隔离级别其实都比上一级多解决了一个问题，但是数据库对于并发执行事务的性能也逐渐下降。</p>
+<table>
+<thead>
+<tr>
+<th>隔离级别</th>
+<th>脏读</th>
+<th>不可重复读</th>
+<th>幻读</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>READ-UNCOMMITTED</td>
+<td>√</td>
+<td>√</td>
+<td>√</td>
+</tr>
+<tr>
+<td>READ-COMMITTED</td>
+<td>×</td>
+<td>√</td>
+<td>√</td>
+</tr>
+<tr>
+<td>REPEATABLE-READ</td>
+<td>×</td>
+<td>×</td>
+<td>√</td>
+</tr>
+<tr>
+<td>SERIALIZABLE</td>
+<td>×</td>
+<td>×</td>
+<td>×</td>
+</tr>
+</tbody>
+</table>
+<p>数据库对于隔离级别的实现，就是使用并发控制机制对在同一时间执行的事务进行控制，限制不同的事务对于同一资源的访问和更新。</p>
+<p>锁是一种最为常见的并发控制机制，在一个事务中，并不会将整个数据库都加锁，而是只会锁住那些需要访问的数据，MySQL 和常见数据库中的锁都分为两种：读锁（共享锁）、写锁（互斥锁）。
+读锁保证了读操作可以并发执行，相互不会影响，而写锁保证了在更新数据库数据时，不会有其他的事务访问或者更改同一条记录造成不可预知的问题。</p>
+<p>除了锁，另一种实现事务隔离性的方式就是通过时间戳，但实际上就是一种乐观锁思想，PostgreSQL就是使用这种方式实现事务的数据库。
+乐观锁在读取数据时不进行加锁操作，它“乐观”地认为在此期间数据不会被其他事务修改。
+为了确保数据的一致性，在数据更新时验证数据的版本或者时间戳等标志信息，以此来判断数据是否被其他事务修改过。如果数据确实被修改过，则乐观锁的更新操作会失败，此时可以根据应用需求选择回滚事务。</p>
+<p>再有就是多版本快照隔离思想。通过维护多个版本的数据，数据库可以允许事务在数据被其他事务更新时，对旧版本的数据进行读取，很多数据库都对这一机制进行了实现，也就是 MVCC。
+MySQL 和 PostgreSQL 都对这一机制进行自己的实现。</p>
+<h4 id="durability持久性">Durability持久性</h4>
+<p>数据被写入到数据库中，那么数据一定是存储在磁盘上。事务的持久性就体现在，一旦事务被提交，那么数据一定会被写入到数据库中并持久存储起来。</p>
+<p>当事务已经被提交之后，就无法再次回滚了，唯一能够撤回已经提交的事务的方式就是创建一个相反的事务对原操作进行撤销，这也是事务持久性的体现之一。</p>
+<p>与原子性一样，事务的持久性也是通过日志来实现的，MySQL使用重做日志（redo log）实现事务的持久性。
+重做日志由两部分组成，一是内存中的重做日志缓冲区，因为它保存在内存中，所以它是易失的，另一个就是在磁盘上的重做日志文件，它是持久的。</p>
+<p>当我们在一个事务中尝试对数据进行修改时，首先会先将数据从磁盘读入内存，并更新内存中缓存的数据，然后生成一条重做日志并写入重做日志缓存。
+当事务真正提交时，MySQL会将重做日志缓存中的内容，刷新到重做日志文件，即将内存中的数据更新到磁盘上。</p>
+<p>在 InnoDB 中，重做日志都是以512字节的块的形式进行存储的，因为块的大小与磁盘扇区大小相同，所以重做日志的写入可以保证原子性，不会由于机器断电导致重做日志仅写入一半并留下脏数据。</p>
+<h3 id="mysql中的日志">MySQL中的日志</h3>
+<p>MySQL 日志 主要包括错误日志、查询日志、慢查询日志、事务日志、二进制日志几大类。
+其中，比较重要的还要属二进制日志 <code>binlog（归档日志）</code>和<code>redo log（重做|事物日志）</code>和 <code>undo log（回滚日志）</code>。</p>
+<p>简单来说，MySQL InnoDB 引擎使用 <code>redo log(重做日志)</code> 保证事务的持久性，使用 <code>undo log(回滚日志)</code> 来保证事务的原子性。
+MySQL的数据备份、主备、主主、主从都离不开 <code>binlog</code>，需要依靠 <code>binlog</code> 来同步数据，保证数据一致性。</p>
+<h3 id="mvcc并发控制机制">MVCC并发控制机制</h3>
+<p>MVCC 是一种并发控制机制，解决多个并发事务同时读写数据库产生的一些问题，用于保持数据的一致性和隔离性。</p>
+<p>它是通过在每个数据行上维护多个版本的数据来实现的。当一个事务要对数据库中的数据进行修改时，MVCC 会为该事务创建一个数据快照，而不是直接修改实际的数据行。
+读操作使用旧版本数据的快照，写操作创建新版本，并确保原版本仍可用。这样，不同的事务可以在一定程度上并发执行，而不会相互干扰。</p>
+<p>当一个事务执行读操作时，它会使用快照读取。因为是快照读取，因此其他并发事务对数据行的修改不会影响当前事务的读取操作。
+事务会查找符合条件的数据快照，并选择符合其事务开始时间的数据版本进行读取，读的是旧快照。
+如果某个数据快照有多个版本，事务会选择不晚于其开始时间的最新版本，确保事务只读取在它开始之前已经存在的数据。</p>
+<p>当一个事务执行写操作时，它会先生成一个新的数据版本快照。原始版本的数据仍然存在，供其他事务使用快照读取，这保证了其他事务不受当前事务的写操作影响。
+新版本的数据会带有当前事务的版本号，以便其他事务能够正确读取相应版本的数据。然后将修改后的数据写入新版本。</p>
+<p>当一个事务提交时，它所做的修改将成为数据库的最新版本，并且对其他事务可见。
+当一个事务回滚时，它所做的修改将被撤销，对其他事务不可见。</p>
+<p>为了防止数据库中的版本无限增长，MVCC会定期进行版本的回收。回收机制会删除已经不再需要的旧版本数据，从而释放空间。</p>
+<p>InnoDB对MVCC的实现主要是依赖于：隐藏字段、<code>Read View</code>、<code>undo log</code>。</p>
+<p>InnoDB 存储引擎为每行数据添加了三个隐藏字段:</p>
+<ul>
+<li><code>DB_TRX_ID（6字节）</code>：表示最后一次插入或更新该行的事务 id。此外，delete 操作在内部被视为更新，只不过会在记录头 Record header 中的 deleted_flag 字段将其标记为已删除；</li>
+<li><code>DB_ROLL_PTR（7字节）</code> 回滚指针，指向该行的 undo log 。如果该行未被更新，则为空；</li>
+<li><code>DB_ROW_ID（6字节）</code>：如果没有设置主键且该表没有唯一非空索引时，InnoDB 会使用该 id 来生成聚簇索引；</li>
+</ul>
+<p><code>Read View</code>主要是用来做可见性判断，里面保存了 “当前对本事务不可见的其他活跃事务”。</p>
+<p><code>undo log</code>作用是，当读取记录时，若该记录被其他事务占用或当前版本对该事务不可见，则可以通过 <code>undo log</code> 读取之前的版本数据，以此实现<strong>非锁定读</strong>。</p>
+<p>非锁定读是什么？</p>
+<p>在 InnoDB 存储引擎中，多版本控制就是对非锁定读的实现。
+如果读取的行正在执行 DELETE 或 UPDATE 操作，这时读取操作不会去等待行上锁的释放。相反地，InnoDB 存储引擎会去读取行的一个快照数据，对于这种读取历史数据的方式，我们叫它快照读，就是对非锁定读的实现。</p>
+<p>具体一点，在 <code>Repeatable Read</code> 和 <code>Read Committed</code> 两个隔离级别下，如果是执行普通的 select 语句，不包括 <code>select ... lock in share mode</code> ,<code>select ... for update</code>则会使用一致性非锁定读。</p>
+<h3 id="操作事物">操作事物</h3>
+<p>所有的存储引擎中只有 <code>InnoDB</code>、<code>NDB</code> 是事务性存储引擎，也就是说只有 <code>InnoDB</code>、<code>NDB</code> 支持事务。
+不支持的存储引擎，比如在MyISAM上操作事务，事务不会生效，SQL语句直接自动执行提交，所以回滚对于不支持事务的存储引擎是无效的。</p>
+<p>启动事务的方式：</p>
+<ul>
+<li><code>begin</code>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">mysql&gt; begin;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.00 sec)
+</span></span><span class="line"><span class="cl">mysql&gt; 事务操作SQL......
+</span></span></code></pre></div></li>
+<li><code>start transaction [修饰符]</code>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">修饰符：
+</span></span><span class="line"><span class="cl">1. read only //只读
+</span></span><span class="line"><span class="cl">2. read write //读写 默认
+</span></span><span class="line"><span class="cl">3. WITH CONSISTENT SNAPSHOT //一致性读
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 例如
+</span></span><span class="line"><span class="cl">mysql&gt; start transaction read only;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.00 sec)
+</span></span><span class="line"><span class="cl">mysql&gt; 事务操作SQL......
+</span></span></code></pre></div></li>
+</ul>
+<p>提交事物完整示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">mysql&gt; begin;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.01 sec)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; update account set balance=balance-20 where id = 1;
+</span></span><span class="line"><span class="cl">Query OK, 1 row affected (0.00 sec)
+</span></span><span class="line"><span class="cl">Rows matched: 1  Changed: 1  Warnings: 0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; update account set balance=balance+20 where id = 2;
+</span></span><span class="line"><span class="cl">Query OK, 1 row affected (0.00 sec)
+</span></span><span class="line"><span class="cl">Rows matched: 1  Changed: 1  Warnings: 0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; commit;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.01 sec)
+</span></span></code></pre></div><p>回滚事物完整示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">mysql&gt; begin;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.00 sec)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; update account set balance=balance-25 where id = 1;
+</span></span><span class="line"><span class="cl">Query OK, 1 row affected (0.00 sec)
+</span></span><span class="line"><span class="cl">Rows matched: 1  Changed: 1  Warnings: 0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; update account set balance=balance+25 where id = 2;
+</span></span><span class="line"><span class="cl">Query OK, 1 row affected (0.00 sec)
+</span></span><span class="line"><span class="cl">Rows matched: 1  Changed: 1  Warnings: 0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; rollback;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.00 sec)
+</span></span></code></pre></div><p>默认是事务自动提交的，每执行一条SQL就自动提交。
+此时需要操作事务，则需要显式开启（begin or start transaction）和提交（commit）或回滚（rollback）。
+如设置成OFF，则需要执行提交（commit）或回滚（rollback）操作时才会真正执行事务。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">--查看事务开启情况：
+</span></span><span class="line"><span class="cl">mysql&gt; SHOW VARIABLES LIKE &#39;autocommit&#39;;
+</span></span><span class="line"><span class="cl">+---------------+-------+
+</span></span><span class="line"><span class="cl">| Variable_name | Value |
+</span></span><span class="line"><span class="cl">+---------------+-------+
+</span></span><span class="line"><span class="cl">| autocommit | ON |
+</span></span><span class="line"><span class="cl">+---------------+-------+
+</span></span></code></pre></div><h2 id="mysql索引">MySQL索引</h2>
+<p>MySQL官方对索引的定义为：索引（Index）是帮助MySQL高效获取数据的数据结构。
+可以得到索引的本质：索引是数据结构。</p>
+<p>索引相当于一本书的目录或者字典。
+比如，要查“mysql”这个单词，我们肯定需要定位到m字母，然后从下往下找到y字母，再找到剩下的sql；如果没有索引，那么你可能需要逐个逐个寻找。
+可以简单理解为，索引维护的就是一组排好序的数据，通过这种有序的数据结构能快速的查找到想要的数据，索引这种数据结构就是以空间换取时间。</p>
+<p>我们平常所说的索引，如果没有特别指明，都是指B树结构组织的索引。当然，除了B+树这种类型的索引之外，还有哈稀索引等。</p>
+<h3 id="索引数据结构">索引数据结构</h3>
+<p>目前大部分数据库系统及文件系统都采用B-树或其变种B+树作为索引结构。</p>
+<p>为什么使用B-树、B+树？</p>
+<p>一般来说，索引本身也很大，不可能全部存储在内存中，因此索引往往以索引文件的形式存储的磁盘上。
+这样的话，索引查找过程中就要产生磁盘I/O消耗，相对于内存存取，I/O存取的消耗要高几个数量级，所以评价一个数据结构作为索引的优劣最重要的指标，就是在查找过程中磁盘I/O操作次数的渐进复杂度。
+换句话说，索引的结构组织要尽量减少查找过程中磁盘I/O的存取次数。</p>
+<p>B树即B-tree 树，B 即 Balanced 平衡的意思。B树通过重新组织节点，降低树的高度，并且减少IO读写次数来提升效率。
+文件系统及数据库系统的设计者，利用了<strong>磁盘预读原理</strong>，将一个节点的大小设为一个页，这样每个节点只需要一次IO就可以完全载入。</p>
+<p>磁盘预读原理是什么？</p>
+<p>主存即主存储器，是计算机中最重要的存储层次之一，它直接与CPU进行数据交换。主存的访问速度很快，但价格较高，且容量有限。主存用于存储当前正在被CPU处理的数据和程序代码。
+磁盘是计算机中重要的辅助存储设备之一，磁盘的容量较大，价格较低，但访问速度较慢。磁盘通常用于长期存储大量的数据和程序代码。</p>
+<p>在存储层次结构中，磁盘通常被用作主存的扩展。当主存空间不足时，操作系统会将一些不常用的数据和程序代码从主存中移到磁盘上，以释放主存空间。
+当这些数据和程序代码再次被需要时，操作系统会将其从磁盘中读取回主存。这就是所谓的磁盘缓存。</p>
+<p>在计算机中，磁盘的读写速度远低于主存和高速缓存，但它的容量较大，可以长期保存大量的数据和程序代码，因此为了提高效率，尽量减少磁盘I/O。
+为了达到这个目的，磁盘往往不是严格按需读取，而是每次都会预读，即使只需要一个字节，磁盘也会从这个位置开始，顺序向后读取一定长度的数据放入内存，这个过程是磁盘预读。
+磁盘预读的理论依据是<strong>局部性原理</strong>，即当一个数据被用到时，其附近的数据也通常会马上被使用。</p>
+<p>磁盘预读的长度一般为页的整倍数。页是计算机管理存储器的逻辑块，硬件及操作系统往往将主存和磁盘存储区分割为连续的大小相等的块，每个存储块称为一页（在许多操作系统中，页得大小通常为4k），主存和磁盘以页为单位交换数据。
+当程序要读取的数据不在主存中时，会触发一个缺页异常，此时系统会向磁盘发出读盘信号，磁盘会找到数据的起始位置并向后连续读取一页或几页载入内存中，然后异常返回，程序继续运行。</p>
+<h3 id="索引的实现">索引的实现</h3>
+<p>在MySQL中，索引属于存储引擎级别的概念，不同存储引擎对索引的实现方式是不同的，这里主要讨论MyISAM、InnoDB两个不同的存储引擎对索引实现方式。</p>
+<h4 id="myisam索引的实现">MyISAM索引的实现</h4>
+<p>在MyISAM引擎中，建立的索引文件和数据文件是分离的，B+Tree 叶节点存放的是数据记录的地址。</p>
+<p><img alt="MyISAM索引结构" src="/iblog/posts/annex/images/essays/MyISAM%E7%B4%A2%E5%BC%95%E7%BB%93%E6%9E%84.png"></p>
+<p>在索引检索的时候，首先按照 B+Tree 搜索算法搜索索引，如果指定的 Key 存在，则取出其叶子结点的值，然后以叶子结点的值为地址读取相应的数据记录。
+这种表示索引结构与数据行存储顺序无关的索引，叫做非聚集索引。</p>
+<p>MyISAM中的主索引和辅助索引在结构上是类似的，都是采用B-Tree结构。它们之间的主要区别在于，主索引要求索引列的值必须唯一，而辅助索引则可以包含重复值。
+但是无论主索引还是辅助索引，它们的叶子节点存储的都是指向数据行实际存储位置的指针，而不是数据本身。
+因此，当通过索引访问数据时，MyISAM 需要进行两次查找：首先在索引中找到对应记录的位置，然后根据该位置读取实际的数据行。</p>
+<h4 id="innodb索引的实现">InnoDB索引的实现</h4>
+<p>在InnoDB引擎中，其数据文件本身就是索引文件。</p>
+<p><img alt="Innodb索引结构" src="/iblog/posts/annex/images/essays/Innodb%E7%B4%A2%E5%BC%95%E7%BB%93%E6%9E%84.png"></p>
+<p>表数据文件本身就是按B+Tree组织的一个索引结构，这棵树的叶节点data域保存了完整的数据记录。这个索引的key是数据表的主键，因此InnoDB表数据文件本身就是<strong>主索引</strong>。
+索引的键值决定了表中数据的物理顺序，这种被称为聚簇索引或聚集索引。</p>
+<p>因为InnoDB的数据文件本身要按主键聚集，所以InnoDB要求表必须有主键，MyISAM可以没有。
+如果没有显式指定，则MySQL系统会自动选择一个可以唯一标识数据记录的列作为主键。
+如果不存在这种列，则MySQL自动为InnoDB表生成一个隐含字段作为主键，这个字段长度为6个字节，类型为长整形。</p>
+<p>与MyISAM索引的不同是，InnoDB的<strong>辅助索引</strong>data域，存储相应记录主键的值而不是地址。
+换句话说，辅助索引的叶节点存储的是主键值，加上一个指向主键的指针，而不是实际的数据行。
+这意味着，当通过辅助索引查询数据时，数据库首先通过辅助索引找到主键，然后用主键到聚簇索引中去查找对应的完整数据行，这个过程称为回表查询。</p>
+<p>知道了InnoDB的索引实现后，就很容易明白为什么不建议使用过长的字段作为主键，因为所有辅助索引都引用主索引，过长的主索引会令辅助索引变得过大。
+再例如，用非单调递增或递减的字段作为主键在InnoDB中也不是个好主意，因为InnoDB数据文件本身是一颗B+Tree，非单调的主键会造成在插入新记录时数据文件为了维持B+Tree的特性而频繁的分裂调整，十分低效，而使用自增字段作为主键则是一个很好的选择。</p>
+<p>主索引、辅助索引是什么？</p>
+<ul>
+<li>主索引通常是基于表的主键建立的索引，保证了索引列值的唯一性。在InnoDB存储引擎中，主索引实际上是一个聚簇索引，这意味着主键不仅提供唯一性约束，还决定了数据行的物理排列顺序。
+在MyISAM中，主索引通常是基于表的一个唯一键创建的，最常见的是基于主键。如果未明确定义主键，MyISAM 会尽可能选择一个唯一的非空索引作为主索引。</li>
+<li>辅助索引是相对于主索引而言，指除主索引之外的其他索引，可以是基于非主键列创建的索引，用于加速对这些列的查询。
+在InnoDB存储引擎中辅助索引的叶子结点存储的是主键值。在MyISAM中，叶子节点存储的是指向数据行实际存储位置的指针。</li>
+</ul>
+<h3 id="索引的优缺点">索引的优缺点</h3>
+<p>索引的优点：</p>
+<ul>
+<li>提高数据检索的效率，降低数据库的IO成本；</li>
+<li>降低数据排序的成本，降低了CPU的消耗；</li>
+</ul>
+<p>索引的缺点：</p>
+<ul>
+<li>索引本身很大，可以放在内存、硬盘中，通常为硬盘；</li>
+<li>索引虽然提高了查询的效率，但是会降低增删改的效率，当对表中的数据进行增删改的时候，如果数据有索引，那么索引也需要动态的修改，也就是会降低 SQL 执行效率；</li>
+</ul>
+<h3 id="索引分类">索引分类</h3>
+<p>按照应用维度划分：</p>
+<ul>
+<li>主键索引：属于唯一索引的一种，但是值不能为null；</li>
+<li>唯一索引：索引列的值必须唯一，但允许有空值；</li>
+<li>单值索引：即一个索引只包含单个列，一个表可以有多个单列索引；</li>
+<li>复合索引：一个索引包含多个列；</li>
+</ul>
+<p>按照底层存储方式角度划分：</p>
+<ul>
+<li>聚簇索引（聚集索引）：索引结构和数据一起存放的索引，InnoDB 中的主键索引就属于聚簇索引。</li>
+<li>非聚簇索引（非聚集索引）：索引结构和数据分开存放的索引，二级索引(辅助索引)就属于非聚簇索引。MySQL 的 MyISAM 引擎，不管主键还是非主键，使用的都是非聚簇索引。</li>
+</ul>
+<h3 id="操作索引">操作索引</h3>
+<p>创建索引：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> CREATE [UNIQUE] INDEX indexName ON mytable(columnName(length));
+</span></span><span class="line"><span class="cl"> ALTER mytable ADD [UNIQUE] INDEX [indexName] ON (columnName(length));
+</span></span></code></pre></div><p>删除索引：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> DROP INDEX [indexName] ON [tableName];
+</span></span></code></pre></div><p>修改索引：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">-- 该语句添加一个主键，这意味着索引值必须是唯一的，且不能为NULL
+</span></span><span class="line"><span class="cl"> ALTER TABLE [tableName] ADD PRIMARY KEY (column_list);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 这条语句创建索引的值必须是唯一的(除了NULL外，NULL可能会出现多次)
+</span></span><span class="line"><span class="cl"> ALTER TABLE [tableName] ADD UNIQUE [indexName] (column_list);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 添加普通索引，索引值可出现多次
+</span></span><span class="line"><span class="cl"> ALTER TABLE [tableName] ADD INDEX [indexName] (column_list);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 该语句指定了索引为FULLTEXT，用于全文索引
+</span></span><span class="line"><span class="cl"> ALTER TABLE [tableName] ADD FULLTEXT [indexName] (column_list);
+</span></span></code></pre></div><p>查看索引：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> SHOW INDEX FROM [tableName];
+</span></span></code></pre></div><h3 id="最左前缀匹配原则">最左前缀匹配原则</h3>
+<p>最左前缀匹配原则是指在使用复合索引，即包含多个列的索引时，MySQL优化器会尽可能地根据索引中的字段顺序，从左到右依次匹配查询条件中的字段。
+如果查询条件与索引中的最左侧字段相匹配，那么 MySQL 就会使用索引来过滤数据，这样可以提高查询效率。</p>
+<p>想要发挥最左前缀匹配的效果，你的查询条件应该至少从复合索引的第一列开始，并且尽可能地包含更多连续的索引列。
+如果查询条件没有从第一列开始或者跳过了中间的列，那么索引的部分或全部效果就可能没法用了。</p>
+<p>现在有一个students表，它有三个列(id, first_name, last_name)，并且针对这三个列创建了一个复合索引(id, first_name, last_name)。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-sql" data-lang="sql"><span class="line"><span class="cl"><span class="c1">-- 可以命中索引
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="k">select</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">from</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="k">where</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">first_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;lisa&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">last_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;liu&#39;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">-- 无法命中索引
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="k">select</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">from</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="k">where</span><span class="w"> </span><span class="n">first_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;lisa&#39;</span><span class="w">
+</span></span></span></code></pre></div><p>联合索引的最左匹配原则，在遇到范围查询（如 &gt;、&lt;）的时候，就会停止匹配，也就是范围查询的字段可以用到联合索引，但是在范围查询字段后面的字段无法用到联合索引。
+但是对于 &gt;=、&lt;=、BETWEEN、like 前缀匹配这四种范围查询，并不会停止匹配。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-sql" data-lang="sql"><span class="line"><span class="cl"><span class="c1">-- 可以命中 id、first_name列，没命中last_name 列
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="k">select</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">from</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="k">where</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;%123%&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">first_name</span><span class="w"> </span><span class="k">like</span><span class="w"> </span><span class="s1">&#39;%lisa%&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">last_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;liu&#39;</span><span class="w">
+</span></span></span></code></pre></div><h3 id="索引覆盖">索引覆盖</h3>
+<p>覆盖索引（Covering Index），一说为索引覆盖。如果一个索引包含或者说覆盖所有需要查询的字段的值，就称为索引覆盖。</p>
+<p>查询的数据列从索引文件中就能够取得，不必读取原数据、回表查询。
+MySQL可以利用索引返回select列表中的字段，而不用根据索引再次读取数据文件，换句话说查询到的列全部都在索引列中就是索引覆盖。</p>
+<p>如果要使用覆盖索引，一定要注意select列表中只取出需要的列，不可select*，因为如果将所有字段一起做索引会导致索引文件过大，查询性能下降。</p>
+<p>覆盖索引举例，(id, first_name, last_name)为一个复合索引。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-sql" data-lang="sql"><span class="line"><span class="cl"><span class="c1">--  覆盖索引，全部命中
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="k">select</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="n">first_name</span><span class="p">,</span><span class="n">last_name</span><span class="w"> </span><span class="k">from</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="k">where</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;%123%&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">first_name</span><span class="w"> </span><span class="k">like</span><span class="w"> </span><span class="s1">&#39;%lisa%&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">last_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;liu&#39;</span><span class="w">
+</span></span></span></code></pre></div><h3 id="索引建立原则">索引建立原则</h3>
+<p>既然索引可以加快查询速度，那么是不是只要是查询语句需要，就建上索引？
+答案肯定是不可以。索引虽然加快了查询速度，但索引也是有代价的：索引文件本身要消耗存储空间，同时索引会加重插入、删除和修改记录时的负担，另外MySQL在运行时也要消耗资源维护索引，因此索引并不是越多越好。</p>
+<p>以下是建立索引的一些原则：</p>
+<ul>
+<li>数据量很小则不适合建立：如果数据库的数据量不大，那么使用索引也不一定能够带来很大提升，所以没有必要建立索引；</li>
+<li>不要建立太多的索引：因为维护索引是需要耗费空间和性能的，MySQl会为了每一个索引维护一个B树，如果索引过多，这无疑是增加了MySQL的负担；</li>
+<li>频繁增删改的字段不要建立索引：如果某个字段频繁修改，那就意味着也需要修改索引，这必然影响MySQL的性能；</li>
+<li>为频繁查询的字段建立索引：建立索引要为经常作为查询条件的字段建立索引，这样能提高SQL的查询效率，与之相反的不要为很少使用的字段建立索引；</li>
+<li>避免为”大字段”建立索引：就是尽量使用字段长度小的字段作为索引；例如，要为<code>varchar(5)</code>和<code>varchar(200)</code>的字段建立索引，则优先考虑为<code>varchar(5)</code>的建立；如果非要为<code>varchar(200)</code>的字段建立索引那么可以这样：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">为</span><span class="n">varchar</span><span class="p">(</span><span class="mi">200</span><span class="p">)</span><span class="err">的字段建立索引，将其长度设置为</span> <span class="mi">20</span>  
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">index</span>  <span class="n">tbl_001</span> <span class="n">on</span> <span class="n">dual</span><span class="p">(</span><span class="n">address</span><span class="p">(</span><span class="mi">20</span><span class="p">));</span>
+</span></span></code></pre></div></li>
+<li>选择数据区分大的列建立索引：如果某个字段包含许多重复的数据则不适合建立索引。假设现在有一个”性别”字段，里面存放的数据的值要么是男，要么是女，这样的字段很不适合作为索引。
+因为如果值出现的几率几乎相等，那么无论搜索哪个值都可能得到一半的数据。在这些情况下，还不如不要索引，因为MySQL他还有一个查询优化器，查询优化器发现某个值出现在表的数据行中的百分比很高的时候，它一般会忽略索引，进行全表扫描。
+惯用的百分比界线是”30%”。匹配的数据量超过一定限制的时候查询器会放弃使用索引，这也是索引失效的场景之一。</li>
+</ul>
+<h3 id="避免索引失效原则">避免索引失效原则</h3>
+<p>建立索引之后还要保证索引生效，才能发挥索引的作用，以下是避免索引失效的原则：</p>
+<ul>
+<li>在使用复合索引时，不要跨列使用或无序使用，即最佳左前缀法则，否则索引失效；
+跨列使用指，where后边的字段和order by后边的字段拼接起来，看是否满足索引的顺序，如不满足则为跨列，会出现Using filsort。</li>
+<li>不要在索引上进行任何操作，例如：计算、函数运算、类型转换等，否则索引失效；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- age列为索引，但此时SQL语句age列存在计算，age索引列失效；
+</span></span><span class="line"><span class="cl"> select * from tbl_001 where age*3 = &#39;10&#39;;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- name为索引列，此时在该索引列上进行函数计算，name索引列失效；
+</span></span><span class="line"><span class="cl"> select * from tbl_001 tbl_001 left(name,4)=&#39;July&#39;; 
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- typeid为索引列，typeid为int类型，此时发生隐式类型转换，typeid索引列失效；
+</span></span><span class="line"><span class="cl"> select * from tbl_001 c typeid = &#39;1&#39;;
+</span></span></code></pre></div></li>
+<li>复合索引不能使用不等于（!=、&lt;&gt;）或is null、is not null，否则自身及右侧索引全部失效；
+大部分情况下如果复合索引使用上面的运算符索引会失效，但是MySQL在服务层存在SQL优化阶段，所以复合索引即使使用了不等于、is null、is not null等操作，还是可能会存在索引生效的情况。</li>
+<li>尽量使用覆盖索引，使用覆盖索引会提高系统性能；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name、tid、cid 为复合索引
+</span></span><span class="line"><span class="cl">  select name,tid,cid from tbl_001 where name = &#39;zs&#39;;
+</span></span></code></pre></div></li>
+<li>like尽量以常量开头，不要以%开头，否则索引失效；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name 为索引列，此处索引失效
+</span></span><span class="line"><span class="cl"> select * from tbl_002 where name like &#39;%x%&#39;;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 如果必须要使用%开头，可以使用覆盖索引挽救一下
+</span></span><span class="line"><span class="cl"> select name from tbl_002 where name like &#39;%x%&#39;;
+</span></span></code></pre></div></li>
+<li>不要使用or，否则索引失效；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- authorid、typeid为复合索引，此处or的左右两边索引全部失效
+</span></span><span class="line"><span class="cl"> select * from book_2021 where authorid = 1 or typeid = 1;
+</span></span></code></pre></div></li>
+<li>避免使用<code>*</code>，因为使用<code>*</code>之后MySQL还需要计算把<code>*</code>替换成对应的列；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">-- 不要使用*，把*替换成具体需要的列
+</span></span><span class="line"><span class="cl"> select * from book_2021;
+</span></span></code></pre></div></li>
+</ul>
+<h2 id="mysql执行计划">MySQL执行计划</h2>
+<p>执行计划 是指一条 SQL 语句在经过 MySQL 查询优化器 的优化后，具体的执行方式。
+使用explain关键字可以模拟优化器执行SQL查询语句，从而知道MySQL是如何处理你的SQL语句的，分析你的查询语句或是表结构的性能瓶颈。
+explain不止适用于select也适用于delete、insert、replace和update语句。</p>
+<p>当explain可解释语句一起使用时，MySQL会显示来自优化器的关于语句执行计划的信息，也就是说，MySQL解释了它将如何处理语句，包括有关表如何连接以及按顺序连接的信息。</p>
+<p>在MySQL中执行任意一条SQL前加上explain关键字，即可看到：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> +----+-------------+----------+------+---------------+------+---------+------+------+-------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table    | type | possible_keys | key  | key_len | ref  | rows | Extra |
+</span></span><span class="line"><span class="cl"> +----+-------------+----------+------+---------------+------+---------+------+------+-------+
+</span></span></code></pre></div><h3 id="idtable">id、table</h3>
+<p>table是显示这一行的数据是关于哪张表的。</p>
+<p>id是select查询的序列号，包含一组数字，表示查询中执行select子句或操作表的顺序。</p>
+<ul>
+<li>id值相同，执行顺序由上至下；</li>
+<li>id值不同，id值越大优先级越高，越先被执行；</li>
+</ul>
+<blockquote>
+<p>表的执行顺序与表中数据息息相关，举个例子：表A：3条数据 表B：4条数据 表C：6条数据</p>
+<p>假设在执行某条SQL的情况下表A、B、C的id值相同，假设执行顺序：表A、B、C。在给表B添加4条数据后，再次执行前面的这条SQL发现执行顺序变为：表A、C、B。
+<br>
+这是因为中间结果会影响表的执行顺序：
+3 * 4 * 2 = 12 * 2 = 24
+3 * 2 * 4 = 6 * 4 = 24
+虽然最后结果一样，但是中间过程不一样。中间过程越小占用的空间越小，所以在ID值相同的情况下数据小的表优先查询。</p>
+</blockquote>
+<h3 id="select_type">select_type</h3>
+<p>select_type是查询的类型，主要是用于区别普通查询、联合查询、子查询等的复杂查询。</p>
+<p>查询类型：</p>
+<ul>
+<li>PRIMARY：包含自查询的主查询，最外层部分；</li>
+<li>SUBQUERY：查询语句中包含了子查询，非最外层；</li>
+<li>SIMPLE：简单查询,即SQL中不包含子查询或者UNION查询；</li>
+<li>DERIVED：在查询过程中创建了临时表，例如SQL：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select name from (select * from table1) t1;
+</span></span></code></pre></div></li>
+<li>UNION：若第二个SELECT出现在UNION之后，则被标记为UNION；若UNION包含在FROM子句的子查询中外层SELECT将被标记为：DERIVED；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select name from (select * from table1 union select * from table2) t1;
+</span></span></code></pre></div></li>
+<li>UNION RESULT：从UNION表中的结果；</li>
+</ul>
+<h3 id="type">type</h3>
+<p>type是索引类型，是较为重要的一个指标，结果值从最好到最坏依次是：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="n">system</span> <span class="o">&gt;</span> <span class="k">const</span> <span class="o">&gt;</span> <span class="n">eq_ref</span> <span class="o">&gt;</span> <span class="n">ref</span> <span class="o">&gt;</span> <span class="n">fulltext</span> <span class="o">&gt;</span> <span class="n">ref_or_null</span> <span class="o">&gt;</span> <span class="n">index_merge</span> <span class="o">&gt;</span> <span class="n">unique_subquery</span> <span class="o">&gt;</span> <span class="n">index_subquery</span> <span class="o">&gt;</span> <span class="nb">range</span> <span class="o">&gt;</span> <span class="n">index</span> <span class="o">&gt;</span><span class="n">ALL</span>
+</span></span></code></pre></div><p>实际工作中可能用不到这么多，一般只要记住以下就行了：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="n">system</span> <span class="o">&gt;</span> <span class="k">const</span> <span class="o">&gt;</span> <span class="n">eq_ref</span> <span class="o">&gt;</span> <span class="n">ref</span> <span class="o">&gt;</span> <span class="nb">range</span> <span class="o">&gt;</span> <span class="n">index</span> <span class="o">&gt;</span> <span class="n">ALL</span>
+</span></span></code></pre></div><p>其中system、const只是理想情况，实际能达到ref、range。</p>
+<p>常见索引类型：</p>
+<ul>
+<li>system：表只有一行记录的系统表，或衍生表只有一行数据的主查询；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 衍生表：(select * from tbl_001) 只有一条记录；id为主键索引
+</span></span><span class="line"><span class="cl"> explain select * from (select * from tbl_001) where id = 1;
+</span></span></code></pre></div></li>
+<li>const：仅仅能查询到一条记录的SQL，并且用于主键索引或者唯一键索引；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- tbl_001表只有一条记录；id为主键索引或唯一键索引
+</span></span><span class="line"><span class="cl"> explain select * from tbl_001 where id = 1;
+</span></span></code></pre></div></li>
+<li>eq_ref：唯一性索引；对于每个索引键的查询，返回匹配唯一一行的数据,有且只有一个，不能多也不能为0；常见于主键或唯一索引扫描；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- tbl_001.tid为索引列；且tbl_001与tbl_002表中数据记录一一对应
+</span></span><span class="line"><span class="cl"> select * from tbl_001,tbl_002 where tbl_001.tid = tbl_002.id
+</span></span></code></pre></div></li>
+<li>ref：非唯一性索引；对于每个索引键的查询，返回多个匹配的所有行，包括0个；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name 为索引列；tbl_001 表中 name 值为 zs 的有多个
+</span></span><span class="line"><span class="cl"> explain select * from tbl_001 where name = &#39;zs&#39;;
+</span></span></code></pre></div></li>
+<li>range：检索指定范围的行，where后面是一个范围查询常见：between and、in、&gt;、&lt;=；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- tid 为索引列；
+</span></span><span class="line"><span class="cl"> explain select * from tbl_001 where tid &lt;=3;
+</span></span></code></pre></div></li>
+<li>index：查询全部索引中的数据；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name为索引列；
+</span></span><span class="line"><span class="cl"> explain select name from tbl_001;
+</span></span></code></pre></div></li>
+<li>all：查询全部表中的数据；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name不是索引列；
+</span></span><span class="line"><span class="cl"> explain select name from tbl_001;
+</span></span></code></pre></div></li>
+</ul>
+<h3 id="possible_keyskey">possible_keys、key</h3>
+<p>possible_keys是可能用到的索引，是一种预测,不准确；key是实际用到的索引，如果为null则没有用到索引。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name为索引列
+</span></span><span class="line"><span class="cl"> explain select name from tbl_001;
+</span></span><span class="line"><span class="cl"> +----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table   | type  | possible_keys | key      | key_len | ref  | rows | Extra       |
+</span></span><span class="line"><span class="cl"> +----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | tbl_001 | index | NULL          | idx_name | 83      | NULL |    4 | Using index |
+</span></span><span class="line"><span class="cl"> +----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+
+</span></span></code></pre></div><h3 id="key_len">key_len</h3>
+<p>key_len索引使用的长度，可通过索引列长度，例如：<code>name vachar(20)</code>，来判断复合索引到底有没有使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name为索引列</span><span class="err">；可以为</span><span class="n">null</span><span class="err">；</span><span class="n">varchar类型</span><span class="err">；</span><span class="n">utf8字符集</span><span class="err">；</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="n">name</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span>  <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>      <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">index</span> <span class="o">|</span> <span class="n">NULL</span>          <span class="o">|</span> <span class="n">idx_name</span> <span class="o">|</span> <span class="mi">63</span>      <span class="o">|</span> <span class="n">NULL</span> <span class="o">|</span>    <span class="mi">4</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+</span>
+</span></span></code></pre></div><p>其中，如果索引字段可以为null，MySQL会用一个字节进行标识；varchar为可变长度，MySQL用两个字节来标识。</p>
+<blockquote>
+<p>utf8：一个字符三个字节；
+gbk：一个字符两个字节；
+latin：一个字符一个字节；</p>
+</blockquote>
+<p>举例，字段<code>name vachar(20)</code>，不能为null，utf8编码，执行执行计划name列使用到了索引那么key_len等于<code>20*3+1+2=63</code>。</p>
+<h3 id="ref">ref</h3>
+<p>ref指明当前表所引用的字段。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">其中</span><span class="n">b</span><span class="o">.</span><span class="n">d可以为常量</span><span class="err">，常量用</span> <span class="k">const</span> <span class="err">标识</span>
+</span></span><span class="line"><span class="cl"> <span class="n">select</span> <span class="o">...</span> <span class="n">where</span> <span class="n">a</span><span class="o">.</span><span class="n">c</span> <span class="o">=</span> <span class="n">b</span><span class="o">.</span><span class="n">d</span><span class="p">;</span>  
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">tid</span> <span class="err">为索引列</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">t1</span><span class="p">,</span><span class="n">tbl_002</span> <span class="n">t2</span> <span class="n">where</span> <span class="n">t1</span><span class="o">.</span><span class="n">tid</span> <span class="o">=</span> <span class="n">t2</span><span class="o">.</span><span class="n">id</span> <span class="ow">and</span> <span class="n">t1</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+--------+------------------+----------+---------+-----------------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span> <span class="o">|</span> <span class="n">type</span>   <span class="o">|</span> <span class="n">possible_keys</span>    <span class="o">|</span> <span class="n">key</span>      <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>             <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+--------+------------------+----------+---------+-----------------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">t1</span>    <span class="o">|</span> <span class="n">ref</span>    <span class="o">|</span> <span class="n">idx_name</span><span class="p">,</span><span class="n">idx_tid</span> <span class="o">|</span> <span class="n">idx_name</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span>           <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">where</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">t2</span>    <span class="o">|</span> <span class="n">eq_ref</span> <span class="o">|</span> <span class="n">PRIMARY</span>          <span class="o">|</span> <span class="n">PRIMARY</span>  <span class="o">|</span> <span class="mi">4</span>       <span class="o">|</span> <span class="n">sql_demo</span><span class="o">.</span><span class="n">t1</span><span class="o">.</span><span class="n">tid</span> <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span> <span class="n">NULL</span>        <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+--------+------------------+----------+---------+-----------------+------+-------------+</span>
+</span></span></code></pre></div><h3 id="rows">rows</h3>
+<p>rows表示查询行数，实际通过索引查询到的个数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> mysql&gt; select * from tbl_001 t1,tbl_002 t2 where t1.tid = t2.id and t1.name = &#39;ls&#39;;
+</span></span><span class="line"><span class="cl"> +----+------+------+----+------+-------+-------+
+</span></span><span class="line"><span class="cl"> | id | name | tid  | id | name | name1 | name2 |
+</span></span><span class="line"><span class="cl"> +----+------+------+----+------+-------+-------+
+</span></span><span class="line"><span class="cl"> |  2 | ls   |    2 |  2 | ls   | ls1   | ls2   |
+</span></span><span class="line"><span class="cl"> |  4 | ls   |    1 |  1 | zs   | zs1   | zs2   |
+</span></span><span class="line"><span class="cl"> +----+------+------+----+------+-------+-------+
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> mysql&gt; explain select * from tbl_001 t1,tbl_002 t2 where t1.tid = t2.id and t1.name = &#39;ls&#39;;
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+-------+------------------+------------+---------+----------------+------+-------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table | type  | possible_keys    | key        | key_len | ref            | rows | Extra       |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+-------+------------------+------------+---------+----------------+------+-------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | t2    | index | PRIMARY          | index_name | 249     | NULL           |    2 | Using index |
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | t1    | ref   | idx_name,idx_tid | idx_tid    | 5       | sql_demo.t2.id |    1 | Using where |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+-------+------------------+------------+---------+----------------+------+-------------+
+</span></span></code></pre></div><h3 id="extra">Extra</h3>
+<p>Extra包含不适合在其他列中显示但十分重要的额外信息。</p>
+<p>常见值：</p>
+<ul>
+<li>Using filesort：文件内排序；出现这个值代表额外的一次排序（查询），性能消耗比较大，需要进行SQL优化。常见order by语句中；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span> <span class="err">为单值索引</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span> <span class="n">order</span> <span class="n">by</span> <span class="n">tid</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+----------+---------+-------+------+----------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>      <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>          <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+----------+---------+-------+------+----------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_name</span>      <span class="o">|</span> <span class="n">idx_name</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">filesort</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+----------+---------+-------+------+----------------+</span>
+</span></span></code></pre></div>对于单值索引来说，如果排序和查找的是同一个字段，则不会出现 Using filesort 反之则出现;一般通过where哪些字段就 orderby 哪些字段来避免。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span><span class="err">，</span><span class="n">tid</span> <span class="err">为复合索引</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span> <span class="n">order</span> <span class="n">by</span> <span class="n">tid</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+-----------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>       <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+-----------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_trans</span>     <span class="o">|</span> <span class="n">idx_trans</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+-----------+---------+-------+------+-------------+</span>
+</span></span></code></pre></div>对于复合索引来说要按照建立复合索引的顺序来使用，不要跨列或者无序使用。
+<blockquote>
+<p>跨列使用指，where后边的字段和order by后边的字段拼接起来，看是否满足索引的顺序，如不满足则为跨列，会出现Using filsort。</p>
+</blockquote>
+</li>
+<li>Using temporary：使了用临时表保存中间结果，MysQL在对查询结果排序时使用临时表。性能消耗也是很大的，一般出现这个词需要进行SQL优化。常见于分组查询group by语句；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span><span class="err">、</span><span class="n">tid</span><span class="err">、</span><span class="n">cid</span> <span class="err">为复合索引</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="n">name</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span> <span class="n">group</span> <span class="n">by</span> <span class="n">cid</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>     <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>                        <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_ntc</span>       <span class="o">|</span> <span class="n">idx_ntc</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>    <span class="mi">2</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span><span class="p">;</span> <span class="n">Using</span> <span class="n">temporary</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+------------------------------+</span>
+</span></span></code></pre></div>Using temporary出现的原因，已经有表了但是不使用，必须再来一张表。我们可以通过查询哪些列，就通过哪些列来分组来避免。</li>
+<li>Using index：出现这个值代表性能还是不错的；表示使用到了覆盖索引，不读取源文件，只从索引文件中获取数据，不需要回表查询。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span><span class="err">、</span><span class="n">tid</span><span class="err">、</span><span class="n">cid</span> <span class="err">为复合索引</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="n">name</span><span class="p">,</span><span class="n">tid</span><span class="p">,</span><span class="n">cid</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>     <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_ntc</span>       <span class="o">|</span> <span class="n">idx_ntc</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>    <span class="mi">2</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span></code></pre></div>如果用到了索引覆盖时，会对possible_key和key造成影响：
+<ul>
+<li>如果没有使用到where，则索引只出现在key中；</li>
+<li>如果有where，则索引出现在key和possible_key中；</li>
+</ul>
+</li>
+<li>Using where：出现这个值代表需要回表查询；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span> <span class="err">为单值索引，此时索引中不包含其他字段，想要查询其他字段就必须回表查询</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="n">name</span><span class="p">,</span><span class="n">tid</span><span class="p">,</span><span class="n">cid</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>     <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_name</span>      <span class="o">|</span> <span class="n">idx_name</span> <span class="o">|</span> <span class="mi">83</span>     <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>   <span class="mi">2</span>  <span class="o">|</span> <span class="n">Using</span> <span class="n">where</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span></code></pre></div></li>
+<li>Impossible WHERE：where语句永远为false，永远不成立；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select * from tbl_001 where name = &#39;zs&#39; and name = &#39;ls&#39;;
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------+---------------+------+---------+------+------+------------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra            |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------+---------------+------+---------+------+------+------------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | Impossible WHERE |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------+---------------+------+---------+------+------+------------------+
+</span></span></code></pre></div></li>
+</ul>
+<h2 id="mysql优化">MySQL优化</h2>
+<p>为什么要进行优化？</p>
+<ul>
+<li>SQL语句欠佳、执行过程耗时较长、索引失效；</li>
+<li>单库数据量越来越大，存储出现问题；</li>
+<li>在高并发场景下，大量请求阻塞；</li>
+</ul>
+<p>总之一句话，数据库出现性能瓶颈。</p>
+<h3 id="sql执行过程">SQL执行过程</h3>
+<p>想要进行SQL优化首先要弄懂SQL编写过程和SQL执行过程是存在区别的：</p>
+<ul>
+<li>SQL编写过程：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> select distinct .. from .. join .. on .. where .. group by .. having .. order by .. limit ..
+</span></span></code></pre></div></li>
+<li>SQL执行过程：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> from .. on .. join ..  where .. group by .. having .. select distinct .. order by .. limit ..
+</span></span></code></pre></div></li>
+</ul>
+<p>之所以SQL的编写过程会和执行过程有区别，是因为MySQL中有专门负责优化Select语句的优化器模块。</p>
+<blockquote>
+<p>MySQL Query Optimizer：MySQL查询优化器。主要功能:通过计算分析系统中收集到的统计信息，为客户端请求的Select提供MySQL认为最优的执行计划。</p>
+</blockquote>
+<p>当客户端向MySQL请求一条Select，命令解析器模块完成请求分类，区别出是Select并转发给MySQL Query Optimizer时，MySQL Query Optimizer首先会对整条Select进行优化，处理掉一些常量表达式的预算直接换算成常量值。
+并对Select中的查询条件进行简化和转换，如去掉一些无用或显而易见的条件、结构调整等。然后分析Select中的Hint信息，看显示Hint信息是否可以完全确定该Select的执行计划。如果没有Hint或Hint信息还不足以完全确定执行计划，则会读取所涉及对象的统计信息，根据Query进行写相应的计算分析，然后再得出最后的执行计划。</p>
+<blockquote>
+<p>Hint: 简单来说就是在某些特定的场景下人工协助MySQL优化器的工作，使其生成最优的执行计划。
+一般来说，优化器的执行计划都是最优化的，不过在某些特定场景下，执行计划可能不是最优化。</p>
+</blockquote>
+<h3 id="优化思路">优化思路</h3>
+<p>数据库性能优化方案很多，主要分为两大类：软件层面、硬件层面。</p>
+<p>软件层面包括：SQL 调优、表结构优化、读写分离、数据库集群、分库分表等；硬件层面主要是增加机器性能。下面是集中常见的优化思路：</p>
+<ol>
+<li>
+<p>SQL调优主要目的是尽可能的让那些慢 SQL 变快，手段其实也很简单就是让 SQL 执行尽量命中索引：</p>
+<ul>
+<li>避免在 where 子句中对字段进行 null 值判断，创建表默认值是 NULL。尽量使用 NOT NULL，或使用特殊值，如 0、-1</li>
+<li>避免在 where 子句中使用 != 或 &lt;&gt; 操作符， MySQL 只有对以下操作符才使用索引：&lt;、&lt;=、=、&gt;、&gt;=、BETWEEN、IN、非 % 开头的 LIKE</li>
+<li>避免在 where 子句中使用 or 来连接条件，可以使用 UNION 进行连接</li>
+<li>能用 union all 就不用 union，union 过滤重复数据要耗费更多的 CPU 资源</li>
+<li>避免全部 like 查询，如 &lsquo;%ConstXiong%&rsquo;</li>
+<li>避免在索引列上使用计算、函数</li>
+<li>in 和 not in 慎用，能用 between 不要用 in</li>
+<li>select 子句中避免使用 *</li>
+<li>根据 where 和 order by 使用比较频繁的字段创建索引，提高查询效率</li>
+<li>索引不宜过多，单表最好不要超过 6 个。索引过多会导致占用存储空间变大；insert、update 变慢</li>
+<li>删除未使用的索引</li>
+</ul>
+</li>
+<li>
+<p>如果是单表数据量太大，解决办法：</p>
+<ul>
+<li>分页查询(在索引上完成排序分页操作、借助主键进行关联)</li>
+<li>单表数据过大，进行分库分表</li>
+<li>考虑使用非关系型数据库提高查询效率</li>
+<li>全文索引场景较多，考虑使用 ElasticSearch、solr</li>
+</ul>
+</li>
+<li>
+<p>其他优化：</p>
+<ul>
+<li>数据库配置参数调整</li>
+<li>数据库表结构优化</li>
+<li>硬件优化，增加服务器数量，扩大服务器内存，CPU核数</li>
+</ul>
+</li>
+</ol>
+<h3 id="排查慢sql">排查慢SQL</h3>
+<p>想要优化SQL，首先要找到慢SQL，慢SQL日志超过响应时间的阈值默认10秒，便会记录该SQL。
+慢SQL日志默认是关闭的，建议在开发调优时打开，最终部署上线时关闭。</p>
+<h4 id="慢sql日志设置">慢SQL日志设置</h4>
+<p>通过SQL来查看记录慢SQL日志是否开启：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">查看变量</span> <span class="n">slow_query_log</span><span class="err">，记录慢查询日志默认关闭</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%s</span><span class="s1">low_query_log%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span>       <span class="o">|</span> <span class="n">Value</span>                                        <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">slow_query_log</span>      <span class="o">|</span> <span class="n">OFF</span>                                          <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">slow_query_log_file</span> <span class="o">|</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">mysql</span><span class="o">/</span><span class="n">data</span><span class="o">/</span><span class="n">MacBook</span><span class="o">-</span><span class="n">Pro</span><span class="o">-</span><span class="mi">2</span><span class="o">-</span><span class="n">slow</span><span class="o">.</span><span class="n">log</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span></code></pre></div><p>可以通过SQL来进行开启记录慢SQL日志：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">在内存中开启慢</span><span class="n">SQL记录日志</span><span class="err">；</span> <span class="err">此种方式在</span> <span class="n">mysql</span> <span class="err">服务重启后失效</span>
+</span></span><span class="line"><span class="cl"> <span class="n">set</span> <span class="n">global</span> <span class="n">slow_query_log</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">查看是否开启慢</span><span class="n">SQL日志记录</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%s</span><span class="s1">low_query_log%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span>       <span class="o">|</span> <span class="n">Value</span>                                        <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">slow_query_log</span>      <span class="o">|</span> <span class="n">ON</span>                                           <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">slow_query_log_file</span> <span class="o">|</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">mysql</span><span class="o">/</span><span class="n">data</span><span class="o">/</span><span class="n">MacBook</span><span class="o">-</span><span class="n">Pro</span><span class="o">-</span><span class="mi">2</span><span class="o">-</span><span class="n">slow</span><span class="o">.</span><span class="n">log</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 在MySQL my.cnf 配置文件中追加配置;重启MySQL服务后也生效，即永久开启
+</span></span><span class="line"><span class="cl"> slow_query_log=1
+</span></span><span class="line"><span class="cl"> slow_query_log_file=/usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span></code></pre></div><p>查看慢SQL记录日志阈值：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">查看慢</span><span class="n">SQL记录日志阈值</span><span class="err">，默认</span><span class="mi">10</span><span class="err">秒</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%lo</span><span class="s1">ng_query_time%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span>   <span class="o">|</span> <span class="n">Value</span>     <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">long_query_time</span> <span class="o">|</span> <span class="mf">10.000000</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span></code></pre></div><p>修改慢SQL记录日志阈值：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">在内存中修改设置慢查询</span><span class="n">SQL记录日志阈值为5秒</span><span class="err">；注意设置后不会立即生效，需要重新登陆</span><span class="n">mysql客户端才会生效</span>
+</span></span><span class="line"><span class="cl"> <span class="n">set</span> <span class="n">global</span> <span class="n">long_query_time</span> <span class="o">=</span> <span class="mi">5</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">设置之后重新登陆</span><span class="n">mysql使用命令查看慢SQL查询日志阈值</span> 
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%lo</span><span class="s1">ng_query_time%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span>   <span class="o">|</span> <span class="n">Value</span>     <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">long_query_time</span> <span class="o">|</span> <span class="mf">5.000000</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 在MySQL配置文件my.cnf中修改慢查询SQL记录日志阈值,设置为3秒
+</span></span><span class="line"><span class="cl"> long_query_time=3
+</span></span></code></pre></div><h4 id="查看慢sql日志">查看慢SQL日志</h4>
+<ul>
+<li>直接查看慢SQL日志；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl">  <span class="o">--</span> <span class="err">模拟慢查询</span><span class="n">SQL</span> 
+</span></span><span class="line"><span class="cl">  <span class="n">select</span> <span class="n">sleep</span><span class="p">(</span><span class="mi">5</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">  <span class="o">--</span> <span class="err">查看是否开启慢</span><span class="n">SQL日志记录</span>
+</span></span><span class="line"><span class="cl">  <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%s</span><span class="s1">low_query_log%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">  <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl">  <span class="o">|</span> <span class="n">Variable_name</span>       <span class="o">|</span> <span class="n">Value</span>                                        <span class="o">|</span>
+</span></span><span class="line"><span class="cl">  <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl">  <span class="o">|</span> <span class="n">slow_query_log</span>      <span class="o">|</span> <span class="n">ON</span>                                           <span class="o">|</span>
+</span></span><span class="line"><span class="cl">  <span class="o">|</span> <span class="n">slow_query_log_file</span> <span class="o">|</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">mysql</span><span class="o">/</span><span class="n">data</span><span class="o">/</span><span class="n">MacBook</span><span class="o">-</span><span class="n">Pro</span><span class="o">-</span><span class="mi">2</span><span class="o">-</span><span class="n">slow</span><span class="o">.</span><span class="n">log</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl">  <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span></code></pre></div>查看慢SQL日志记录<code>cat /usr/local/mysql/data/MacBook-Pro-2-slow.log</code>执行命令：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> MacBook-Pro-2:~ root# cat /usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span><span class="line"><span class="cl"> /usr/local/mysql/bin/mysqld, Version: 8.0.22 (MySQL Community Server - GPL). started with:
+</span></span><span class="line"><span class="cl"> Tcp port: 3306  Unix socket: /tmp/mysql.sock
+</span></span><span class="line"><span class="cl"> Time                 Id Command    Argument
+</span></span><span class="line"><span class="cl"> # Time: 2021-09-17T06:46:20.655775Z
+</span></span><span class="line"><span class="cl"> # User@Host: root[root] @ localhost []  Id:    15
+</span></span><span class="line"><span class="cl"> # Query_time: 4.003891  Lock_time: 0.000000 Rows_sent: 1  Rows_examined: 1
+</span></span><span class="line"><span class="cl"> use sql_demo;
+</span></span><span class="line"><span class="cl"> SET timestamp=1631861176;
+</span></span><span class="line"><span class="cl"> select sleep(4);
+</span></span></code></pre></div></li>
+<li>通过<code>mysqldumpslow</code>工具来查看,可以通过一些过滤条件快速找到需要定位的慢SQL；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> 语法：mysqldumpslow 各种参数 慢查询日志文件路径
+</span></span><span class="line"><span class="cl"> -s：排序方式
+</span></span><span class="line"><span class="cl"> -r：逆序反转
+</span></span><span class="line"><span class="cl"> -l：锁定时间，不要从总时间中减去锁定时间
+</span></span><span class="line"><span class="cl"> -g：在文件中查找考虑包含此字符串的
+</span></span><span class="line"><span class="cl"> 更多指令解析查看 mysqldumpslow --help
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 获取返回记录最多的3条SQL
+</span></span><span class="line"><span class="cl"> mysqldumpslow -s r -t 3 /usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 获取访问次数最多的3条SQL
+</span></span><span class="line"><span class="cl"> mysqldumpslow -s r -t 3 /usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 按照时间排序，前10条包含 left join 的查询SQL 
+</span></span><span class="line"><span class="cl"> mysqldumpslow -s t -t 10 -g &#34;left join&#34; /usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="模拟数据并分析sql">模拟数据并分析SQL</h4>
+<ul>
+<li>
+<p>模拟数据；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">创建表</span>
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">database</span> <span class="n">testdata</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="n">use</span> <span class="n">testdata</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">dept</span> 
+</span></span><span class="line"><span class="cl"> <span class="p">(</span>
+</span></span><span class="line"><span class="cl"> <span class="n">dno</span> <span class="ne">int</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="n">primary</span> <span class="n">key</span> <span class="n">default</span> <span class="mi">0</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">dname</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">loc</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">30</span><span class="p">)</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span>
+</span></span><span class="line"><span class="cl"> <span class="p">)</span> <span class="n">engine</span><span class="o">=</span><span class="n">innodb</span> <span class="n">default</span> <span class="n">charset</span><span class="o">=</span><span class="n">utf8</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">emp</span>
+</span></span><span class="line"><span class="cl"> <span class="p">(</span>
+</span></span><span class="line"><span class="cl"> <span class="n">eid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="n">primary</span> <span class="n">key</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">ename</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">job</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">deptno</span> <span class="ne">int</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">default</span> <span class="mi">0</span>
+</span></span><span class="line"><span class="cl"> <span class="p">)</span><span class="n">engine</span><span class="o">=</span><span class="n">innodb</span> <span class="n">default</span> <span class="n">charset</span><span class="o">=</span><span class="n">utf8</span><span class="p">;</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">创建存储过程：获取随机字符串</span>
+</span></span><span class="line"><span class="cl"> <span class="n">set</span> <span class="n">global</span> <span class="n">log_bin_trust_function_creators</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="n">use</span> <span class="n">testdata</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="n">delimiter</span> <span class="o">$</span>
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">function</span> <span class="n">randstring</span><span class="p">(</span><span class="n">n</span> <span class="ne">int</span><span class="p">)</span> <span class="n">returns</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">255</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl"> <span class="n">begin</span> 
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     <span class="n">declare</span> <span class="n">all_str</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">100</span><span class="p">)</span> <span class="n">default</span> <span class="s1">&#39;abcdefghijklmnopqrestuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">declare</span> <span class="n">return_str</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">255</span><span class="p">)</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">declare</span> <span class="n">i</span> <span class="ne">int</span> <span class="n">default</span> <span class="mi">0</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="k">while</span> <span class="n">i</span><span class="o">&lt;</span><span class="n">n</span>
+</span></span><span class="line"><span class="cl">     <span class="k">do</span>
+</span></span><span class="line"><span class="cl">         <span class="n">set</span> <span class="n">return_str</span><span class="o">=</span><span class="n">concat</span><span class="p">(</span><span class="n">return_str</span><span class="p">,</span> <span class="n">substring</span><span class="p">(</span><span class="n">all_str</span><span class="p">,</span> <span class="n">FLOOR</span><span class="p">(</span><span class="mi">1</span><span class="o">+</span><span class="n">rand</span><span class="p">()</span><span class="o">*</span><span class="mi">52</span><span class="p">),</span> <span class="mi">1</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">         <span class="n">set</span> <span class="n">i</span><span class="o">=</span><span class="n">i</span><span class="o">+</span><span class="mi">1</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">end</span> <span class="k">while</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="k">return</span> <span class="n">return_str</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="n">end</span> <span class="o">$</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 创建存储函数：插入随机整数
+</span></span><span class="line"><span class="cl"> use testdata;
+</span></span><span class="line"><span class="cl"> create function ran_num() returns int(5)
+</span></span><span class="line"><span class="cl"> begin 
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> declare i int default 0;
+</span></span><span class="line"><span class="cl"> set i=floor(rand()*100);
+</span></span><span class="line"><span class="cl"> return i;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> end$
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 创建存储过程：向emp表插入数据
+</span></span><span class="line"><span class="cl"> create procedure insert_emp(in eid_start int(10), in data_times int(10))
+</span></span><span class="line"><span class="cl"> begin 
+</span></span><span class="line"><span class="cl"> declare i int default 0;
+</span></span><span class="line"><span class="cl"> set autocommit =0;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> repeat 
+</span></span><span class="line"><span class="cl"> insert into emp values(eid_start+i, randstring(5), &#39;other&#39;, ran_num());
+</span></span><span class="line"><span class="cl"> set i=i+1;
+</span></span><span class="line"><span class="cl"> until i=data_times
+</span></span><span class="line"><span class="cl"> end repeat;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> commit;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> end $
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 创建存储过程：向dept表插入数据
+</span></span><span class="line"><span class="cl"> create procedure insert_dept(in dno_start int(10), in data_times int(10))
+</span></span><span class="line"><span class="cl"> begin 
+</span></span><span class="line"><span class="cl"> declare i int default 0;
+</span></span><span class="line"><span class="cl"> set autocommit =0;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> repeat 
+</span></span><span class="line"><span class="cl"> insert into dept values(dno_start+i, randstring(6), randstring(8));
+</span></span><span class="line"><span class="cl"> set i=i+1;
+</span></span><span class="line"><span class="cl"> until i=data_times
+</span></span><span class="line"><span class="cl"> end repeat;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> commit;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> end $
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 向emp、dept表中插入数据
+</span></span><span class="line"><span class="cl"> delimiter ;
+</span></span><span class="line"><span class="cl"> call insert_emp(1000, 800000);
+</span></span><span class="line"><span class="cl"> call insert_dept(10, 30);
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 验证插入数据量
+</span></span><span class="line"><span class="cl"> select count(1) from emp;
+</span></span></code></pre></div></li>
+<li>
+<p>使用<code>show profile</code>进行sql分析；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">查看</span> <span class="n">profiling</span> <span class="err">是否开启，默认是关闭的</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;profiling&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------+-------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span> <span class="o">|</span> <span class="n">Value</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------+-------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">profiling</span>     <span class="o">|</span> <span class="n">OFF</span>   <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------+-------+</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">如果没开启将其开启</span>
+</span></span><span class="line"><span class="cl"> <span class="n">set</span> <span class="n">profiling</span><span class="o">=</span><span class="n">on</span><span class="p">;</span>
+</span></span></code></pre></div></li>
+<li>
+<p>执行测试SQL，任意执行均可供之后SQL分析；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">select * from emp;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">select * from emp group by eid order by eid;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">select * from emp group by eid limit 150000;
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="o">--</span> <span class="err">执行命令，查看结果</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">profiles</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----------+------------+--------------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Query_ID</span> <span class="o">|</span> <span class="n">Duration</span>   <span class="o">|</span> <span class="n">Query</span>                                            <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----------+------------+--------------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">2</span> <span class="o">|</span> <span class="mf">0.00300900</span> <span class="o">|</span> <span class="n">show</span> <span class="n">tables</span>                                      <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">3</span> <span class="o">|</span> <span class="mf">0.01485700</span> <span class="o">|</span> <span class="n">desc</span> <span class="n">emp</span>                                         <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">4</span> <span class="o">|</span> <span class="mf">0.00191200</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">10</span> <span class="n">limit</span> <span class="mi">150000</span>   <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">5</span> <span class="o">|</span> <span class="mf">0.25516300</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span>                                <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">6</span> <span class="o">|</span> <span class="mf">0.00026400</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">10</span> <span class="n">limit</span> <span class="mi">150000</span>   <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">7</span> <span class="o">|</span> <span class="mf">0.00019600</span> <span class="o">|</span> <span class="n">select</span> <span class="n">eid</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">10</span> <span class="n">limit</span> <span class="mi">150000</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">8</span> <span class="o">|</span> <span class="mf">0.03907500</span> <span class="o">|</span> <span class="n">select</span> <span class="n">eid</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">limit</span> <span class="mi">150000</span>    <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">9</span> <span class="o">|</span> <span class="mf">0.06499100</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">limit</span> <span class="mi">150000</span>      <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">10</span> <span class="o">|</span> <span class="mf">0.00031500</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">20</span> <span class="n">order</span> <span class="n">by</span> <span class="mi">5</span>     <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">11</span> <span class="o">|</span> <span class="mf">0.00009100</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">20</span> <span class="n">order</span> <span class="n">by</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">12</span> <span class="o">|</span> <span class="mf">0.00012400</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">order</span> <span class="n">by</span>          <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">13</span> <span class="o">|</span> <span class="mf">0.25195300</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">order</span> <span class="n">by</span> <span class="n">eid</span>      <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">14</span> <span class="o">|</span> <span class="mf">0.00196200</span> <span class="o">|</span> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;profiling&#39;</span>                  <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">15</span> <span class="o">|</span> <span class="mf">0.26208900</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">order</span> <span class="n">by</span> <span class="n">eid</span>      <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----------+------------+--------------------------------------------------+</span>
+</span></span></code></pre></div></li>
+<li>
+<p>使用命令<code>show profile cpu,block io for query 上一步前面执行 show profiles 的 Query_ID ;</code>诊断SQL；</p>
+<blockquote>
+<p>参数备注，不区分大小写:
+all：显示所有的开销信息;
+block io：显示块lO相关开销;
+context switches：上下文切换相关开销;
+cpu：显示CPU相关开销信息;
+ipc：显示发送和接收相关开销信息;
+memory：显示内存相关开销信息;
+page faults：显示页面错误相关开销信息;
+source：显示和Source_function，Source_file，Source_line相关的开销信息;
+swaps：显示交换次数相关开销的信息;</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> show profile cpu,block io for query 3;
+</span></span><span class="line"><span class="cl"> +----------------------------+----------+----------+------------+--------------+---------------+
+</span></span><span class="line"><span class="cl"> | Status                     | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |
+</span></span><span class="line"><span class="cl"> +----------------------------+----------+----------+------------+--------------+---------------+
+</span></span><span class="line"><span class="cl"> | starting                   | 0.004292 | 0.000268 |   0.000941 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000026 | 0.000012 |   0.000013 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000007 | 0.000005 |   0.000003 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | Opening tables             | 0.003883 | 0.000865 |   0.000880 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | init                       | 0.000022 | 0.000013 |   0.000008 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | System lock                | 0.000013 | 0.000012 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | optimizing                 | 0.000994 | 0.000078 |   0.000155 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | statistics                 | 0.000233 | 0.000222 |   0.000011 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | preparing                  | 0.000046 | 0.000043 |   0.000003 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | Creating tmp table         | 0.000075 | 0.000073 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | executing                  | 0.001532 | 0.000141 |   0.000266 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000050 | 0.000044 |   0.000005 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000014 | 0.000012 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.001539 | 0.000102 |   0.000356 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000044 | 0.000037 |   0.000007 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000019 | 0.000016 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.001250 | 0.000089 |   0.000318 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | end                        | 0.000015 | 0.000007 |   0.000008 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | query end                  | 0.000006 | 0.000004 |   0.000001 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | waiting for handler commit | 0.000041 | 0.000040 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | removing tmp table         | 0.000012 | 0.000010 |   0.000001 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | waiting for handler commit | 0.000010 | 0.000009 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | closing tables             | 0.000019 | 0.000018 |   0.000001 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | freeing items              | 0.000648 | 0.000081 |   0.000152 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | cleaning up                | 0.000067 | 0.000047 |   0.000021 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> +----------------------------+----------+----------+------------+--------------+---------------+
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="全局查询日志">全局查询日志</h4>
+<p><strong>不要在生产环境开启这个功能。</strong></p>
+<p>在配置MySQL文件<code>my.cnf</code>设置全局查询日志：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="o">--</span> <span class="err">开启全局查询日志</span>
+</span></span><span class="line"><span class="cl"><span class="n">general_log</span><span class="o">=</span><span class="mi">1</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">记录日志文件的路径</span>
+</span></span><span class="line"><span class="cl"><span class="n">general_log_file</span><span class="o">=/</span><span class="n">path</span><span class="o">/</span><span class="n">logfile</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">设置输出格式为</span> <span class="n">FILE</span>
+</span></span><span class="line"><span class="cl"><span class="n">log_output</span><span class="o">=</span><span class="n">FILE</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">通过</span><span class="n">cat命令直接查看</span><span class="err">；如果为空则需要造数</span>
+</span></span><span class="line"><span class="cl"><span class="n">cat</span> <span class="o">/</span><span class="k">var</span><span class="o">/</span><span class="n">lib</span><span class="o">/</span><span class="n">mysql</span><span class="o">/</span><span class="n">bigdata01</span><span class="o">.</span><span class="n">log</span><span class="p">;</span>
+</span></span></code></pre></div><p>在mysql客户端设置全局查询日志：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="o">--</span> <span class="err">查看是否开启全局查询日志</span>
+</span></span><span class="line"><span class="cl"><span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%g</span><span class="s1">eneral_log%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">开启全局查询日志</span>
+</span></span><span class="line"><span class="cl"><span class="n">set</span> <span class="n">global</span> <span class="n">general_log</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">设置输出格式为</span> <span class="n">TABLE</span>
+</span></span><span class="line"><span class="cl"><span class="n">set</span> <span class="n">global</span> <span class="n">log_output</span><span class="o">=</span><span class="s1">&#39;TABLE&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">可在</span><span class="n">mysql库里的geneial_log表查看</span><span class="err">；如果为空则需要造数</span>
+</span></span><span class="line"><span class="cl"><span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">mysql</span><span class="o">.</span><span class="n">general_log</span><span class="p">;</span>
+</span></span></code></pre></div><h3 id="sql优化方法">SQL优化方法</h3>
+<p>对于后端程序员来说，想让SQL执行的更快，最主要的就是软件层面优化索引和分库分表。</p>
+<h4 id="exist和in选择">exist和in选择</h4>
+<p>两者可以互相替代，如果主查询的数据集大，使用in的效率高一点；如果子查询的数据集大，使用exist效率高一点；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 假设此处主查询数据集较大，使用in
+</span></span><span class="line"><span class="cl"> select * from tbl_001 where tid in (select id from tbl_001);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">  -- 假设此处子查询数据集较大，使用exist
+</span></span><span class="line"><span class="cl">  select tid from tbl_001 where exists (select * from tbl_001);
+</span></span></code></pre></div><blockquote>
+<p>exists语法：将主查询的结果，放到子查询结果中进行判断，看子查询中是否有数据，如果有数据则保留数据并返回；没有则返回空。</p>
+</blockquote>
+<h4 id="order-by优化">order by优化</h4>
+<p>order by 是比较常用的一个关键字，基本上查询出来的数据都要进行排序，否则就太乱了。使用order by的时候常常伴随着Using filesort的发生，Using filesort在底层有两种算法，根据IO的次数分为：</p>
+<ul>
+<li>双路排序：MySQL4.1之前默认使用双路排序；具体执行流程，双路排序需要扫描两次磁盘上的字段，首先扫描排序的字段对字段进行排序，然后扫描其他字段；</li>
+<li>单路排序：为了减少IO访问次数在MySQL4.1之后默认使用单路排序；读取一次获取全部的字段，在buffer中进行排序。但是此种方法存在隐患不一定是只读一次数据，如果数据量过大buffer放不下则再需要读取文件，可以通过调节buffer来进行缓解；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 设置读取文件缓冲区（buffer）的大小,单位字节
+</span></span><span class="line"><span class="cl"> set max_length_for_sort_data = 1024;
+</span></span></code></pre></div></li>
+</ul>
+<p>如果需要排序的列的总大小超过了设置的<code>max_length_for_sort_data</code>那么MySQL底层会自动从单路排序切换到双路排序。</p>
+<p>保证全部索引排序字段的一致性，都是升序或都是降序，不要部分升序部分降序。</p>
+<h3 id="sql优化案例">SQL优化案例</h3>
+<h4 id="单表优化">单表优化</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">准备测试表、测试数据</span>
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">book_2021</span><span class="p">(</span>
+</span></span><span class="line"><span class="cl">   <span class="n">bid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="n">primary</span> <span class="n">key</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">name</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">authorid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">publicid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">typeid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span>  
+</span></span><span class="line"><span class="cl"> <span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="s1">&#39;java&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="s1">&#39;php&#39;</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s1">&#39;c&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="s1">&#39;c#&#39;</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span><span class="s1">&#39;c++&#39;</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span></code></pre></div><p>需要优化的SQL：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- SQL原型，优化该SQL 
+</span></span><span class="line"><span class="cl"> select bid from book_2021 where typeid in(2,3) and authorid=1 order by typeid desc;
+</span></span></code></pre></div><p>执行计划分析该SQL,发现该SQL存在<code>Using filesort</code>,type为ALL，需要进行SQL优化。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select bid from book_2021 where typeid in(2,3) and authorid=1 order by typeid desc;
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------+---------------+------+---------+------+------+-----------------------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table     | type | possible_keys | key  | key_len | ref  | rows | Extra                       |
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------+---------------+------+---------+------+------+-----------------------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | book_2021 | ALL  | NULL          | NULL | NULL    | NULL |    5 | Using where; Using filesort |
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------+---------------+------+---------+------+------+-----------------------------+
+</span></span></code></pre></div><ol>
+<li>根据SQL的执行过程可知,建立索引的顺序为<code>typeid、authorid、bid</code>；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- sql执行顺序
+</span></span><span class="line"><span class="cl"> from .. on .. join ..  where .. group by .. having .. select distinct .. order by .. limit ..
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 建立索引
+</span></span><span class="line"><span class="cl"> alter table book_2021 add index idx_tab(typeid,authorid,bid);
+</span></span></code></pre></div></li>
+<li>使用in的时候使索引失效，如果in失效那么后面的索引也将会失效，所以将范围条件放到最后；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 优化后的SQL
+</span></span><span class="line"><span class="cl"> select bid from book_2021 where authorid=1 and typeid in(2,3) order by typeid desc;
+</span></span></code></pre></div>将旧索引删除，创建字段顺序对应的索引。
+<blockquote>
+<p>温馨提示：索引一旦升级优化，需要删除索引防止干扰</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 删除 idx_tab 索引
+</span></span><span class="line"><span class="cl"> drop index idx_tab on book_2021;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 给表 book_2021 添加索引 idx_atb
+</span></span><span class="line"><span class="cl"> alter table book_2021 add index idx_atb(authorid,typeid,bid);
+</span></span></code></pre></div></li>
+</ol>
+<p>最终优化后的SQL执行过程：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select bid from book_2021 where authorid=1 and typeid in(2,3) order by typeid desc;
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------------+-------+---------------+---------+---------+------+------+----------+-----------------------------------------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table     | partitions | type  | possible_keys | key     | key_len | ref  | rows | filtered | Extra                                         |
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------------+-------+---------------+---------+---------+------+------+----------+-----------------------------------------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | book_2021 | NULL       | range | idx_atb       | idx_atb | 8       | NULL |    3 |   100.00 | Using where; Backward index scan; Using index |
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------------+-------+---------------+---------+---------+------+------+----------+-----------------------------------------------+
+</span></span></code></pre></div><p>单表优化总结：</p>
+<ul>
+<li>最佳左前缀原则，保持索引的定义和使用顺序一致；</li>
+<li>索引需要逐步优化；</li>
+<li>将包含范围查询的条件放置到最后；</li>
+</ul>
+<h4 id="两表优化">两表优化</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">准备测试表、测试数据</span>
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">teacher2</span><span class="p">(</span>
+</span></span><span class="line"><span class="cl">   <span class="n">tid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="n">primary</span> <span class="n">key</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">cid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span>  
+</span></span><span class="line"><span class="cl"> <span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">teacher2</span> <span class="n">values</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">teacher2</span> <span class="n">values</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">teacher2</span> <span class="n">values</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">course2</span><span class="p">(</span>
+</span></span><span class="line"><span class="cl">   <span class="n">cid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">cname</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl"> <span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">course2</span> <span class="n">values</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="s1">&#39;java&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">course2</span> <span class="n">values</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="s1">&#39;phython&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">course2</span> <span class="n">values</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s1">&#39;kotlin&#39;</span><span class="p">);</span>
+</span></span></code></pre></div><p>需要优化的SQL：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- SQL原型，优化该SQL 
+</span></span><span class="line"><span class="cl"> select * from teacher2 t left outer join course2 c on t.cid = c.cid where c.cname = &#39;java&#39;;
+</span></span></code></pre></div><p>执行过程分析该SQL，发现进行了全表扫描。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select * from teacher2 t left outer join course2 c on t.cid = c.cid where c.cname = &#39;java&#39;;
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+--------------------------------------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra                                      |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+--------------------------------------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | c     | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    3 |    33.33 | Using where                                |
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | t     | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    3 |    33.33 | Using where; Using join buffer (hash join) |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+--------------------------------------------+
+</span></span></code></pre></div><p>优化思路为建立索引，在哪张表哪个字段建立索引？即<strong>小表驱动大表</strong>，索引应建立在经常使用的字段上，假设此时teacher表数据量少，那么应为<code>t.cid、c.name</code>字段加索引。</p>
+<p>什么是小表驱动大表？
+假设小表10条数据；大表300条数据；让大小表做嵌套循环，无论10是外层循环还是300是外层循环，结果都是3000次，但是为了减少表连接创建的次数，应该将10，即小表放在外层循环这样效率会更高。</p>
+<p>为什么这么做？
+现有两个表A与B ，表A有200条数据，表B有20万条数据。按照循环的概念举个例子：</p>
+<ul>
+<li>小表驱动大表：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(200条){
+</span></span><span class="line"><span class="cl">for(20万条){
+</span></span><span class="line"><span class="cl">...
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>大表驱动小表：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(20万条){
+</span></span><span class="line"><span class="cl">for(200条){
+</span></span><span class="line"><span class="cl">...
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+</ul>
+<p>如果小的循环在外层，对于表连接来说就只连接200次，如果大的循环在外层，则需要进行20万次表连接，从而浪费资源，增加消耗。
+小表驱动大表的主要目的是通过减少表连接创建的次数，加快查询速度。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 给表teacher2、course2 添加索引
+</span></span><span class="line"><span class="cl"> alter table teacher2 add index idx_teacher2_cid(cid);
+</span></span><span class="line"><span class="cl"> alter table course2 add index idx_course2_cname(cname);
+</span></span></code></pre></div><p>最终优化后的SQL：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">添加索引后</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">teacher2</span> <span class="n">t</span> <span class="n">left</span> <span class="n">outer</span> <span class="n">join</span> <span class="n">course2</span> <span class="n">c</span> <span class="n">on</span> <span class="n">t</span><span class="o">.</span><span class="n">cid</span> <span class="o">=</span> <span class="n">c</span><span class="o">.</span><span class="n">cid</span> <span class="n">where</span> <span class="n">c</span><span class="o">.</span><span class="n">cname</span> <span class="o">=</span> <span class="s1">&#39;java&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+------------+------+-------------------+-------------------+---------+----------------+------+----------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span> <span class="o">|</span> <span class="n">partitions</span> <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span>     <span class="o">|</span> <span class="n">key</span>               <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>            <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">filtered</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+------------+------+-------------------+-------------------+---------+----------------+------+----------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">c</span>     <span class="o">|</span> <span class="n">NULL</span>       <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_course2_cname</span> <span class="o">|</span> <span class="n">idx_course2_cname</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span>          <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span>   <span class="mf">100.00</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">where</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">t</span>     <span class="o">|</span> <span class="n">NULL</span>       <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_teacher2_cid</span>  <span class="o">|</span> <span class="n">idx_teacher2_cid</span>  <span class="o">|</span> <span class="mi">4</span>       <span class="o">|</span> <span class="n">sql_demo</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">cid</span> <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span>   <span class="mf">100.00</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+------------+------+-------------------+-------------------+---------+----------------+------+----------+-------------+</span>
+</span></span></code></pre></div><p>多表优化总结：</p>
+<ul>
+<li>小表驱动大表；</li>
+<li>索引建立在经常查询的字段上；</li>
+</ul>
+<h2 id="mysql锁机制">MySQL锁机制</h2>
+<p>在数据库中，除传统的计算资源（如CPU、RAM、I/O等）的争用以外，数据也是一种供许多用户共享的资源。如何保证数据并发访问的一致性、有效性是所有数据库必须解决的一个问题，锁冲突也是影响数据库并发访问性能的一个重要因素。从这个角度来说，锁对数据库而言显得尤其重要，也更加复杂。
+简而言之，锁机制是解决因资源共享，而造成的并发问题。</p>
+<p>MySQL中的锁按照对数据操作的类型分为：读锁即共享锁，写锁即互斥锁；按照操作粒度来分，分为表锁、行锁，页锁。</p>
+<ul>
+<li>读锁：对于同一个数据，多个读操作可以同时进行，互不干扰。</li>
+<li>写锁：如果当前写操作没有完毕，则无法进行其他的读操作、写操作。</li>
+<li>表锁：一次性对一张表整体加锁。MyISAM存储引擎偏向表锁，开销较小、加锁较快、无死锁、锁的范围较大，但是容易发生发生锁冲突，并发度低。</li>
+<li>行锁：一次性对一条数据加锁。InnoDB存储引擎偏向行锁，开销较大、加锁较慢、容易出现死锁、锁的范围较小，但是不易发生锁冲突，并发度高。</li>
+</ul>
+<h3 id="表锁">表锁</h3>
+<p>测试数据：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">mylock</span> <span class="p">(</span>
+</span></span><span class="line"><span class="cl">     <span class="n">id</span> <span class="ne">int</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">primary</span> <span class="n">key</span> <span class="n">auto_increment</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">     <span class="n">name</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span>
+</span></span><span class="line"><span class="cl"> <span class="p">)</span> <span class="n">engine</span> <span class="n">myisam</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;a&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;b&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;c&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;d&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;e&#39;</span><span class="p">);</span>
+</span></span></code></pre></div><p>常用命令：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 加锁
+</span></span><span class="line"><span class="cl"> lock table 表名1 read/write, 表名2 read/write, 其他;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> -- 解锁
+</span></span><span class="line"><span class="cl"> unlock tables;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 查看表上是否加锁；在In_use列，0代表没有加锁，1代表加锁
+</span></span><span class="line"><span class="cl"> show open tables;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> -- 分析表锁
+</span></span><span class="line"><span class="cl"> -- Table_locks_immediate：产生表级锁定的次数，表示可以立即获取锁的查询次数，每立即获取锁值加1
+</span></span><span class="line"><span class="cl"> -- Table_locks_waited：出现表级锁定争用而发生等待的次数(不能立即获取锁的次数，每等待一次锁值加1)，此值高则说明存在着较严重的表级锁争用情况
+</span></span><span class="line"><span class="cl"> show status like &#39;table_locks%&#39;;
+</span></span></code></pre></div><hr>
+<p>给表添加<strong>读锁</strong>及测试读操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-002" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-002.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-004" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-004.png"></p>
+<p>给表添加<strong>读锁</strong>及测试写操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-003" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-003.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-005" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-005.png"></p>
+<p>给某个表添加读锁之后，所有会话都能对这个表进行读操作，但是当前会话不能对该表进行写操作，对其他表进行读、写操作；其他会话能需要等持有锁的会话释放该表的锁后，才能进行写操作，期间将会一直处于等待状态，可以对其他表进行读写操作。</p>
+<hr>
+<p>给表添加<strong>写锁</strong>及测试读操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-006" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-006.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-007" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-007.png"></p>
+<p>给表添加<strong>写锁</strong>及测试写操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-008" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-008.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-009" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-009.png"></p>
+<p>给某个表添加写锁之后，当前会话可以对该表进行写操作、读操作，其他会话要想对该表进行读写操作需要等持有锁的会话释放锁，否则期间将会一直等待该锁释放；但是当前持有锁的会话是不能对其他表进行读写操作，其他会话能够对其他表进行读写操作。</p>
+<p>对于表锁MyISAM在执行查询语句前，会自动给涉及的所有表加读锁，在执行增删改操作前，会自动给涉及的表加写锁。</p>
+<ul>
+<li>对MyISAM表的读操作(加读锁)，不会阻塞其他进程对同一表的读请求，但会阻塞对同一表的写请求。只有当读锁释放后，才会执行其它进程的写操作。</li>
+<li>对MyISAM表的写操作(加写锁)，会阻塞其他进程对同一表的读和写操作，只有当写锁释放后，才会执行其它进程的读写操作。</li>
+</ul>
+<p>简而言之，就是读锁会阻塞写，但是不会堵塞读。而写锁则会把读和写都堵塞。</p>
+<h3 id="行锁">行锁</h3>
+<p>测试数据：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> CREATE TABLE test_innodb_lock (a INT(11),b VARCHAR(16))ENGINE=INNODB;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(1,&#39;b2&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(3,&#39;3&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(4, &#39;4000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(5,&#39;5000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(6, &#39;6000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(7,&#39;7000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(8, &#39;8000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(9,&#39;9000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(1,&#39;b1&#39;);
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> CREATE INDEX test_innodb_a_ind ON test_innodb_lock(a);
+</span></span><span class="line"><span class="cl"> CREATE INDEX test_innodb_lock_b_ind ON test_innodb_lock(b);
+</span></span><span class="line"><span class="cl"> 
+</span></span></code></pre></div><p>常用命令：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 分析行锁定：
+</span></span><span class="line"><span class="cl"> -- 尤其是当等待次数很高，而且每次等待时长也不小的时候，我们就需要分析系统中为什么会有如此多的等待，然后根据分析结果着手指定优化计划。
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_current_waits：当前正在等待锁定的数量；
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_time：从系统启动到现在锁定总时间长度；
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_time_avg：每次等待所花平均时间；
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_time_max：从系统启动到现在等待最常的一次所花的时间；
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_waits：系统启动后到现在总共等待的次数；
+</span></span><span class="line"><span class="cl"> -- show status like &#39;innodb_row_lock%&#39;;
+</span></span></code></pre></div><p>由于行锁与事务相关，所以在测试之前需要关闭MySQL的自动提交：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 关闭自动提交；0关闭，1打开
+</span></span><span class="line"><span class="cl"> set autocommit = 0;
+</span></span></code></pre></div><p>测试行锁读写操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-010" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-010.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-011" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-011.png"></p>
+<p>当前会话当关闭MySQL自动提交后，修改表中的某一行数据，未提交前其他会话是不可见该修改的数据的；如果当前会话和修改某一行数据其他会话也修改该行数据则其他会话会一直等待，直到持有锁的会话commit后才会执行。
+如果当前会话和其他会话操作同一张表的不同行数据时，则相互不影响。</p>
+<p><strong>使用行锁时注意，无索引行或索引失效都会导致行锁变为表锁。</strong></p>
+<p><strong>间隙锁：</strong></p>
+<p>当我们用范围条件而不是相等条件检索数据，并请求共享或排他锁时，InnoDB会给符合条件的已有数据记录的索引项加锁，对于键值在条件范围内但并不存在的记录，叫做“间隙”。
+InnoDB也会对这个“间隙”加锁，这种锁机制就是所谓的间隙锁。</p>
+<p>因为Query执行过程中通过过范围查找的话，他会锁定整个范围内所有的索引键值，即使这个键值并不存在。</p>
+<p>间隙锁有一个比较致命的弱点，就是当锁定一个范围键值之后，即使某些不存在的键值也会被无辜的锁定，而造成在锁定的时候无法插入锁定键值范围内的任何数据。在某些场景下这可能会对性能造成很大的危害。</p>
+<p>如何锁定一行？在查询语句使用<code>for update</code>关键字：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> select * from test_innodb_lock where a=8 for update;
+</span></span></code></pre></div><p><img alt="MySqlSQL优化及锁机制-012" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-012.png"></p>
+<p>Innodb存储引擎由于实现了行级锁定，虽然在锁定机制的实现方面所带来的性能损耗可能比表级锁定会要更高一些，但是在整体并发处理能力方面要远远优于MyISAM的表级锁定的。
+当系统并发量较高的时候，Innodb的整体性能和MyISAM相比就会有比较明显的优势了。
+但是，Innodb的行级锁定同样也有其脆弱的一面，当我们使用不当的时候，可能会让Innodb的整体性能表现不仅不能比MyISAM高，甚至可能会更差。</p>
+<h3 id="总结">总结</h3>
+<ul>
+<li>MySQL锁分为全局锁、表级锁以及行级锁，不同的存储引擎支持锁的粒度有所不同，MyISAM 只支持到表级锁，InnoDB 则可以支持到行级锁，锁的粒度决定了业务的并发度，因此更推荐使用InnoDB</li>
+<li>InnoDB默认最小加锁粒度为行级锁，并且锁是加在索引上，如果SQL语句未命中索引，则走聚簇索引的全表扫描，表上每条记录都会上锁，导致并发能力下降，增大死锁的概率，因此需要为表合理的添加索引，线上查询尽量命中索引</li>
+<li>行级锁默认加 next-key lock，而根据不同的索引也有不同的加锁规则，我们可以根据加锁规分析加锁区间</li>
+<li>尽可能让所有数据检索都通过索引来完成，避免无索引行锁升级为表锁</li>
+<li>合理设计索引，尽量缩小锁的范围</li>
+<li>尽可能较少检索条件，避免间隙锁</li>
+<li>尽量控制事务大小，减少锁定资源量和时间长度</li>
+<li>尽可能低级别事务隔离</li>
+</ul>
+<h2 id="分库分表">分库分表</h2>
+<p>当数据库存储出现瓶颈的时候，就需要进行分库分表了。
+假设你现在在一个小公司，注册用户就 20 万，每天活跃用户就 1 万，每天单表数据量就 1000，然后高峰期每秒钟并发请求最多就 10 个。
+随着公司业务发展，过了几年，注册用户数达到了 5000 万，每天活跃用户数 200 万，每天单表数据量 50 万条，数据库磁盘容量不断消耗掉，高峰期并发达到惊人的 5000~8000，这时候你会发现你得系统已经支撑不住了已经挂掉了。</p>
+<p>一句话概括，随着业务的发展，数据库会遇到瓶颈，单表得数据量太大，会极大影响你的 sql 执行的性能，到了后面你的 sql 可能就跑的很慢了。
+所以为了维持功能的正常使用不得不分库分表。</p>
+<ul>
+<li>分表：分表就是把一个表的数据放到多个表中，然后查询的时候你就查一个表。比如按照用户 id 来分表，将一个用户的数据就放在一个表中。
+然后操作的时候你对一个用户就操作那个表就好了。分表主要是为了减少单张表的大小，解决单表数据量带来的性能问题。当单表数据增量过快，业界流传是超过500万的数据量就要考虑分表了。
+当然500万只是一个经验值，大家可以根据实际情况做出决策。</li>
+<li>分库：一个库一般我们经验而言，最多支撑到并发 2000，超过这个数字就一定要扩容了，而且一个健康的单库并发值你最好保持在每秒 1000 左右，不要太大。
+那么你可以将一个库的数据拆分到多个库中，访问的时候就访问一个库好了。</li>
+</ul>
+<p>分库分表是两个事情，别搞混了，可能是光分库不分表，也可能是光分表不分库，都有可能，但不管怎样分库分表一定是为了支撑高并发、数据量大两个问题的。
+分库分表是能不分就不分，因为分库分表也会带来一些问题：</p>
+<ul>
+<li>跨库关联查询</li>
+<li>分布式事务</li>
+<li>排序、分页、函数计算问题</li>
+<li>分布式ID</li>
+<li>多数据源</li>
+</ul>
+<h3 id="拆分方案">拆分方案</h3>
+<p>怎么拆分？拆分方案一般分为两种，水平拆分，垂直拆分。</p>
+<p>水平拆分的意思，基于数据划分，表结构相同，数据不同。例如，现有一个业务表，新建业务表2，业务表与业务表2中字段一致，将ID为奇数的存储在业务表中，偶数的存放在业务表2中。
+就是把一个表的数据给弄到多个库的多个表里去，但是每个库的表结构都一样，只不过每个库表放的数据是不同的，所有库表的数据加起来就是全部数据。
+水平拆分的意义，就是将数据均匀放更多的库里，然后用多个库来扛更高的并发，还有就是用多个库的存储容量来进行扩容。</p>
+<p>垂直拆分的意思，基于表或字段划分，表结构不同。例如，将业务表中不常用的字段name和age存放到业务表2中。
+就是把一个有很多字段的表给拆分成多个表，或者是多个库上去。每个库表的结构都不一样，每个库表都包含部分字段。
+一般来说，会将较少的访问频率很高的字段放到一个表里去，然后将较多的访问频率很低的字段放到另外一个表里去。
+因为数据库是有缓存的，你访问频率高的行字段越少，就可以在缓存里缓存更多的行，性能就越好，这个一般在表层面做的较多一些。</p>
+<ul>
+<li>
+<p>在一个库内拆分多个表：先分库，将不同数据库中的表拆分为了多个子表，多个子表存在于同一数据库中；
+<img alt="MySqlSQL优化及锁机制-013" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-013.png"></p>
+</li>
+<li>
+<p>用多库拆分一个表，将一个数据库中的表拆分到多个数据库中；
+<img alt="MySqlSQL优化及锁机制-014" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-014.png"></p>
+</li>
+</ul>
+<p>在一个数据库中将一张表拆分为几个子表，在一定程度上可以解决单表查询性能的问题，但是也会遇到单数据库存储瓶颈这个问题，所以用的更多的还是将子表拆分到多个数据库中。</p>
+<p>除了垂直和水平拆分外，还有比较流行的分库分表方式，一种是按照range，即范围来分，就是每个库一段连续的数据，这个一般是按比如时间范围来的。
+但是这种一般较少用，因为很容易产生热点问题，大量的流量都打在最新的数据上了；另一种是按照某个字段的hash值，一下均匀分散。</p>
+<p>range：好处在于扩容的时候很简单，因为你只要预备好，给每个月都准备一个库就可以了，到了一个新的月份的时候，自然而然，就会写新的库了；
+缺点，但是大部分的请求，都是访问最新的数据。实际生产用 range，要看场景。</p>
+<p>hash：好处在于可以平均分配每个库的数据量和请求压力；
+坏处在于说扩容起来比较麻烦，会有一个数据迁移的过程，之前的数据需要重新计算 hash 值重新分配到不同的库或表。</p>
+<h3 id="数据迁移方案">数据迁移方案</h3>
+<p>现在有一个未分库分表的系统，未来要分库分表，如何设计才可以让系统从未分库分表动态切换到分库分表上？</p>
+<p>方案一：停机迁移</p>
+<ol>
+<li>网站或者 app 发布公告，例如，0 点到早上 6 点进行运维，无法访问；</li>
+<li>到时间将系统停掉，执行导数工具，将单库单表的数据读出来，写到分库分表里面去；</li>
+<li>导数完之后，需要改配置，验证一下数据；</li>
+</ol>
+<p>方案二：双写迁移</p>
+<ol>
+<li>在线上系统里面，之前所有写库的地方，增删改操作，除了对老库增删改，都加上对新库的增删改；</li>
+<li>重新部署系统，新数据库数据差太多，就写一个导数工具，跑起来读老库数据写新库，跑的时候要注意，老数据不要覆盖掉新数据；</li>
+<li>假设导完数据了，有可能数据还是存在不一致，那么就程序自动做一轮校验，比对新老库每个表的每条数据，就针对那些不一样的，从老库读数据再次写。
+反复循环，直到两个库每个表的数据都完全一致为止；</li>
+</ol>
+<h3 id="常见分库分表中间件">常见分库分表中间件</h3>
+<p><a href="https://github.com/alibaba/cobar/wiki">Cobar</a>：
+阿里 b2b 团队开发和开源的，属于 proxy 层方案，就是介于应用服务器和数据库服务器之间。应用程序通过 JDBC 驱动访问 Cobar 集群，Cobar 根据 SQL 和分库规则对 SQL 做分解，然后分发到 MySQL 集群不同的数据库实例上执行。早些年还可以用，但是最近几年都没更新了，基本没啥人用，差不多算是被抛弃的状态吧。而且不支持读写分离、存储过程、跨库 join 和分页等操作。</p>
+<p><a href="https://github.com/alibaba/tb_tddl">TDDL</a>：
+淘宝团队开发的，属于 client 层方案。支持基本的 crud 语法和读写分离，但不支持 join、多表查询等语法。目前使用的也不多，因为还依赖淘宝的 diamond 配置管理系统。</p>
+<p><a href="https://github.com/Qihoo360/Atlas">Atlas</a>：
+360 开源的，属于 proxy 层方案，以前是有一些公司在用的，但是确实有一个很大的问题就是社区最新的维护都在 5 年前了。所以，现在用的公司基本也很少了。</p>
+<p><a href="https://shardingsphere.apache.org/document/legacy/4.x/document/cn/overview">Sharding-jdbc</a>：
+当当开源的，属于 client 层方案，是 ShardingSphere 的 client 层方案， ShardingSphere 还提供 proxy 层的方案 Sharding-Proxy。确实之前用的还比较多一些，因为 SQL 语法支持也比较多，没有太多限制，而且截至 2019.4，已经推出到了 4.0.0-RC1 版本，支持分库分表、读写分离、分布式 id 生成、柔性事务（最大努力送达型事务、TCC 事务）。而且确实之前使用的公司会比较多一些（这个在官网有登记使用的公司，可以看到从 2017 年一直到现在，是有不少公司在用的），目前社区也还一直在开发和维护，还算是比较活跃，个人认为算是一个现在也可以选择的方案。</p>
+<p><a href="https://www.yuque.com/ccazhw/ml3nkf">Mycat</a>：
+基于 Cobar 改造的，属于 proxy 层方案，支持的功能非常完善，而且目前应该是非常火的而且不断流行的数据库中间件，社区很活跃，也有一些公司开始在用了。但是确实相比于 Sharding jdbc 来说，年轻一些，经历的锤炼少一些。</p>
+<p>综上，现在其实建议考量的，就是 Sharding-jdbc 和 Mycat，这两个都可以去考虑使用。无论分库还是分表，上面说的那些数据库中间件都是可以支持的。就是基本上那些中间件可以做到你分库分表之后，中间件可以根据你指定的某个字段值，比如说 userid，自动路由到对应的库上去，然后再自动路由到对应的表里去。</p>
+<p>Sharding-jdbc 这种 client 层方案的优点在于不用部署，运维成本低，不需要代理层的二次转发请求，性能很高，但是如果遇到升级啥的需要各个系统都重新升级版本再发布，各个系统都需要耦合 Sharding-jdbc 的依赖；</p>
+<p>Mycat 这种 proxy 层方案的缺点在于需要部署，自己运维一套中间件，运维成本高，但是好处在于对于各个项目是透明的，如果遇到升级之类的都是自己中间件那里搞就行了。</p>
+<p>通常来说，这两个方案其实都可以选用，但是建议中小型公司选用 Sharding-jdbc，client 层方案轻便，而且维护成本低，不需要额外增派人手，而且中小型公司系统复杂度会低一些，项目也没那么多；但是中大型公司最好还是选用 Mycat 这类 proxy 层方案，因为可能大公司系统和项目非常多，团队很大，人员充足，那么最好是专门弄个人来研究和维护 Mycat，然后大量项目直接透明使用即可。</p>
+<h2 id="参考链接">参考链接</h2>
+<ul>
+<li><a href="https://mp.weixin.qq.com/s/-Jipxjwe-jAax4hJSe-9Jg">https://mp.weixin.qq.com/s/-Jipxjwe-jAax4hJSe-9Jg</a></li>
+<li><a href="https://www.hollischuang.com/archives/6330">https://www.hollischuang.com/archives/6330</a></li>
+<li><a href="https://dev.mysql.com/doc/refman/8.0/en/using-explain.html">https://dev.mysql.com/doc/refman/8.0/en/using-explain.html</a></li>
+<li><a href="https://www.javanav.com/interview/7b1d6961b1e344fa9b6ea74819d4f417.html">https://www.javanav.com/interview/7b1d6961b1e344fa9b6ea74819d4f417.html</a></li>
+<li><a href="http://blog.chinaunix.net/uid-30272888-id-5602128.html">http://blog.chinaunix.net/uid-30272888-id-5602128.html</a></li>
+<li><a href="https://blog.codinglabs.org/articles/theory-of-mysql-index.html">https://blog.codinglabs.org/articles/theory-of-mysql-index.html</a></li>
+<li><a href="https://javaguide.cn/database/mysql/mysql-index.html">https://javaguide.cn/database/mysql/mysql-index.html</a></li>
+<li><a href="https://mp.weixin.qq.com/s/8qemhRg5MgXs1So5YCv0fQ">https://mp.weixin.qq.com/s/8qemhRg5MgXs1So5YCv0fQ</a></li>
+<li><a href="https://javaguide.cn/database/mysql/innodb-implementation-of-mvcc.html">https://javaguide.cn/database/mysql/innodb-implementation-of-mvcc.html</a></li>
+<li><a href="https://javabetter.cn/mysql/shiwu-shixian.html">https://javabetter.cn/mysql/shiwu-shixian.html</a></li>
+</ul>
+</div>
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+    <div id="footer_powered_by" class="powered_by">
+        <a href="https://varkai.com">Designed by VarKai,</a>
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+
+    <div id="footer_slogan" class="footer_slogan">
+        <span>from 2021</span>
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index 45508aa6..ff85cc84 100644
--- a/blog-site/public/posts/essays/data-structures-algorithms/index.html
+++ b/blog-site/public/posts/essays/data-structures-algorithms/index.html
@@ -8,7 +8,7 @@
 	
 	
 	
-	<title>数据结构与算法 ｜ 脚踏实地</title>
+	<title>数据结构与算法详解 ｜ 脚踏实地</title>
 	
     
     
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                 <div class="post animate__animated animate__fadeInDown">
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-                        <h2 id="post_single_title">数据结构与算法</h2>
+                        <h2 id="post_single_title">数据结构与算法详解</h2>
                         <span id="post_page_title_date" class="date">2021.12.10</span>
                         
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index 64207c76..df9bdbd6 100644
--- a/blog-site/public/posts/essays/nginx-start/index.html
+++ b/blog-site/public/posts/essays/nginx-start/index.html
@@ -8,7 +8,7 @@
 	
 	
 	
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                 <div class="post animate__animated animate__fadeInDown">
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-                        <h2 id="post_single_title">Nginx介绍</h2>
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index 06867cbe..fc51e4ba 100644
--- a/blog-site/public/posts/essays/pay-code/index.html
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index a2d3b515..1e20ba1d 100644
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+++ b/blog-site/public/posts/index.html
@@ -197,7 +197,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-arraylist/">ArrayList详解</a>
+                            <a href="/iblog/posts/detailed/java-arraylist/">ArrayList详解</a>
                             <div class="post_time"><span class="date">06-26</span></div>
                         </div>
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@@ -211,7 +211,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/sql-select-fast/">MySQL详解</a>
+                            <a href="/iblog/posts/detailed/sql-select-fast/">MySQL详解</a>
                             <div class="post_time"><span class="date">05-30</span></div>
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                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/distributed-lock/">分布式锁详解</a>
+                            <a href="/iblog/posts/detailed/distributed-lock/">分布式锁详解</a>
                             <div class="post_time"><span class="date">05-25</span></div>
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                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/distributed-id/">分布式ID</a>
+                            <a href="/iblog/posts/detailed/distributed-id/">分布式ID详解</a>
                             <div class="post_time"><span class="date">03-13</span></div>
                         </div>
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                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/elasticsearch/">Elasticsearch详解</a>
+                            <a href="/iblog/posts/detailed/elasticsearch/">Elasticsearch详解</a>
                             <div class="post_time"><span class="date">02-14</span></div>
                         </div>
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@@ -835,7 +835,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-mq/">MQ详解</a>
+                            <a href="/iblog/posts/detailed/java-mq/">MQ详解</a>
                             <div class="post_time"><span class="date">10-19</span></div>
                         </div>
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@@ -863,7 +863,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-transaction/">分布式事务详解</a>
+                            <a href="/iblog/posts/detailed/java-transaction/">分布式事务详解</a>
                             <div class="post_time"><span class="date">08-02</span></div>
                         </div>
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@@ -884,7 +884,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-redis/">Redis详解</a>
+                            <a href="/iblog/posts/detailed/java-redis/">Redis详解</a>
                             <div class="post_time"><span class="date">06-17</span></div>
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-                    <div class="listing_item">
-                        <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-hashmap/">HashMap详解</a>
-                            <div class="post_time"><span class="date">05-03</span></div>
-                        </div>
-                    </div>
-                    
                     <div class="listing_item">
                         <div class="listing_post">
                             <a href="/iblog/posts/jvm/jvm-about/">JVM中的一些概念</a>
@@ -968,7 +961,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-netty/">Netty详解</a>
+                            <a href="/iblog/posts/detailed/java-netty/">Netty详解</a>
                             <div class="post_time"><span class="date">04-09</span></div>
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-                    <div class="listing_item">
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-                            <div class="post_time"><span class="date">04-04</span></div>
-                        </div>
-                    </div>
-                    
                     <div class="listing_item">
                         <div class="listing_post">
                             <a href="/iblog/posts/spring/springboot-redis/">SpringBoot整合Redis</a>
@@ -1240,28 +1226,28 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/"></a>
+                            <a href="/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97/"></a>
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-                            <a href="/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/"></a>
+                            <a href="/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97/"></a>
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+                            <a href="/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/"></a>
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index e310a106..edb8a7e3 100644
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-      <guid>http://localhost:1313/iblog/posts/essays/java-arraylist/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-arraylist/</guid>
       <description>ArrayList 在List接口实现类中，最常用的就是ArrayList，ArrayList类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删</description>
     </item>
     <item>
@@ -59,9 +59,9 @@
     </item>
     <item>
       <title>MySQL详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/sql-select-fast/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/sql-select-fast/</link>
       <pubDate>Thu, 30 May 2024 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/sql-select-fast/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/sql-select-fast/</guid>
       <description>MySQL介绍 MySQL 是一种关系型数据库，主要用于持久化存储我们系统中的一些数据。 MySQL 如此流行的原因，主要具有下面这些优点： 成熟稳定，功能完善。 开源免费。 文档丰富，既有</description>
     </item>
     <item>
@@ -87,9 +87,9 @@
     </item>
     <item>
       <title>分布式锁详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/distributed-lock/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/distributed-lock/</link>
       <pubDate>Sat, 25 May 2024 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/distributed-lock/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/distributed-lock/</guid>
       <description>概述 在代码里面我们常用ReetrantLock、synchronized保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。 类似这样： public</description>
     </item>
     <item>
@@ -583,10 +583,10 @@
       <description>SpringMVC SpringWebMVC是建立在Servlet API上的原始Web框架，从一开始就包含在Spring框架中。正式名称 &amp;ldquo;Spring Web MVC &amp;ldquo;来自其源模块的名称（s</description>
     </item>
     <item>
-      <title>分布式ID</title>
-      <link>http://localhost:1313/iblog/posts/essays/distributed-id/</link>
+      <title>分布式ID详解</title>
+      <link>http://localhost:1313/iblog/posts/detailed/distributed-id/</link>
       <pubDate>Mon, 13 Mar 2023 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/distributed-id/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/distributed-id/</guid>
       <description>分布式ID 在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。 但随着数据日渐增长，主从同步也扛不住了，</description>
     </item>
     <item>
@@ -598,9 +598,9 @@
     </item>
     <item>
       <title>Elasticsearch详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/elasticsearch/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/elasticsearch/</link>
       <pubDate>Tue, 14 Feb 2023 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/elasticsearch/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/elasticsearch/</guid>
       <description>概览 Elasticsearch，简称为 ES， ES是一个开源的高扩展的分布式全文搜索引擎， 是整个 ElasticStack 技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可</description>
     </item>
     <item>
@@ -668,9 +668,9 @@
     </item>
     <item>
       <title>MQ详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-mq/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/java-mq/</link>
       <pubDate>Tue, 19 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-mq/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-mq/</guid>
       <description>概览 MQ 即 messagequeue 消息队列，是分布式系统的重要组件，主要解决异步消息，应用解耦，消峰等问题。从而实现高可用，高性能，可伸缩和最终一致性的架构。使用较多的MQ有：acti</description>
     </item>
     <item>
@@ -696,9 +696,9 @@
     </item>
     <item>
       <title>分布式事务详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-transaction/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/java-transaction/</link>
       <pubDate>Mon, 02 Aug 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-transaction/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-transaction/</guid>
       <description>基础概念 什么是事务 什么是事务？举个例子：你去超市买东西，&amp;ldquo;一手交钱，一手交货&amp;quot;就是一个事务的例子。 交钱和交货必须同时成功，事务才算成功，其</description>
     </item>
     <item>
@@ -717,9 +717,9 @@
     </item>
     <item>
       <title>Redis详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-redis/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/java-redis/</link>
       <pubDate>Thu, 17 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-redis/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-redis/</guid>
       <description>Redis概述 参考文章： https://www.runoob.com/redis/redis-intro.html https://www.redis.com.cn/redis-interview-questions.html 什么是Redis Redis(Remote Dictionary Server) Redis 是一个开源的使用 ANSI C 语言编写、遵守 BSD 协议、支持网络、可基于内存亦可持久化的日志型、Key-Value 数据库，</description>
     </item>
     <item>
@@ -743,13 +743,6 @@
       <guid>http://localhost:1313/iblog/posts/java/rookie-multi-thread/</guid>
       <description>线程与进程 进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。 线程是操作系统能够进行运算调度的最小单位。它被包</description>
     </item>
-    <item>
-      <title>HashMap详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-hashmap/</link>
-      <pubDate>Mon, 03 May 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-hashmap/</guid>
-      <description>HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问</description>
-    </item>
     <item>
       <title>JVM中的一些概念</title>
       <link>http://localhost:1313/iblog/posts/jvm/jvm-about/</link>
@@ -808,9 +801,9 @@
     </item>
     <item>
       <title>Netty详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/java-netty/</link>
+      <link>http://localhost:1313/iblog/posts/detailed/java-netty/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/java-netty/</guid>
+      <guid>http://localhost:1313/iblog/posts/detailed/java-netty/</guid>
       <description>Netty 参考文章：https://dongzl.github.io/netty-handbook/#/ 概述 Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers &amp;amp; clients. Netty 是一个异步的、基于事</description>
     </item>
     <item>
@@ -953,13 +946,6 @@
       <guid>http://localhost:1313/iblog/posts/essays/java-thread-collection/</guid>
       <description>Java中常用线程安全的集合 在多线程环境中，数据的一致性和线程的安全性是至关重要的。传统的集合类，如ArrayList、HashMap和HashSet，在并发访</description>
     </item>
-    <item>
-      <title>CAS详解</title>
-      <link>http://localhost:1313/iblog/posts/essays/cas-detail/</link>
-      <pubDate>Sat, 04 Apr 2020 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/essays/cas-detail/</guid>
-      <description>CAS CAS全称为Compare and Swap被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更</description>
-    </item>
     <item>
       <title>SpringBoot整合Redis</title>
       <link>http://localhost:1313/iblog/posts/spring/springboot-redis/</link>
@@ -1053,30 +1039,30 @@
     </item>
     <item>
       <title></title>
-      <link>http://localhost:1313/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>http://localhost:1313/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>http://localhost:1313/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>http://localhost:1313/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>http://localhost:1313/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>http://localhost:1313/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>http://localhost:1313/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>http://localhost:1313/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>http://localhost:1313/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>http://localhost:1313/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>http://localhost:1313/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>http://localhost:1313/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>http://localhost:1313/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
   </channel>
diff --git a/blog-site/public/posts/intro/docker-start/index.html b/blog-site/public/posts/intro/docker-start/index.html
new file mode 100644
index 00000000..0f05fca1
--- /dev/null
+++ b/blog-site/public/posts/intro/docker-start/index.html
@@ -0,0 +1,603 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Docker入门 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="概述 Docker属于Linux容器的一种封装，提供简单易用的容器使用接口。它是目前流行的Linux容器解决方案。Docker将应用程序与该程序的依赖，打包在一个" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
+    
+
+	
+
+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%bf%b0">
+                    概述
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#linux%e4%b8%8a%e5%ae%89%e8%a3%85">
+                    Linux上安装
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%85%8d%e7%bd%ae%e9%95%9c%e5%83%8f">
+                    配置镜像
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b7%a5%e4%bd%9c%e5%8e%9f%e7%90%86">
+                    工作原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e7%94%a8%e5%91%bd%e4%bb%a4">
+                    常用命令
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Docker入门</h2>
+                        <span id="post_page_title_date" class="date">2020.04.07</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
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+                    </div>
+                    <div class="post_content markdown"><h2 id="概述">概述</h2>
+<p><code>Docker</code>属于<code>Linux</code>容器的一种封装，提供简单易用的容器使用接口。它是目前流行的<code>Linux</code>容器解决方案。<code>Docker</code>将应用程序与该程序的依赖，打包在一个文件里面。运行这个文件，就会生成一个虚拟容器。
+程序在这个虚拟容器里运行，就好像在真实的物理机上运行一样。有了 <code>Docker</code>，就不用担心环境问题。总体来说<code>Docker</code>的接口相当简单，用户可以方便地创建和使用容器，把自己的应用放入容器。
+容器还可以进行版本管理、复制、分享、修改，就像管理普通的代码一样。</p>
+<p><code>Docker</code>可以提供一次性的环境。比如，本地测试他人的软件、持续集成的时候提供单元测试和构建的环境。
+还可以提供弹性的云服务，因为<code>Docker</code>容器可以随开随关，很适合动态扩容和缩容。
+<code>Docker</code>最常见的就是通过多个容器，组建微服务架构，一台机器可以跑多个服务，因此在本机就可以模拟出微服务架构。</p>
+<h2 id="linux上安装">Linux上安装</h2>
+<p>2017年的3月1号之后，<code>Docker</code>的版本命名开始发生变化，同时将CE版本和EE版本进行分开。</p>
+<ul>
+<li>Docker社区版（CE）：为了开发人员或小团队创建基于容器的应用,与团队成员分享和自动化的开发管道。<code>docker-ce</code>提供了简单的安装和快速的安装，以便可以立即开始开发。<code>docker-ce</code>集成和优化，基础设施。（免费）</li>
+<li>Docker企业版（EE）：专为企业的发展和IT团队建立谁。<code>docker-ee</code>为企业提供最安全的容器平台，以应用为中心的平台。（付费）</li>
+</ul>
+<p>以下是<code>CentOS</code>或<code>RHEL</code>上使用<code>yum</code>来安装<code>Docker</code>示例。</p>
+<ol>
+<li><code>Docker</code>依赖于系统的一些必要的工具，所以先安装依赖。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">yum install -y yum-utils device-mapper-persistent-data lvm2
+</span></span></code></pre></div></li>
+<li>通过使用<code>yum-config-manager</code>来设置<code>Docker</code>的稳定仓库。(在阿里云镜像站上面可以找到<code>docker-ce</code>的软件源，使用国内的源速度比较快)。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
+</span></span></code></pre></div></li>
+<li>安装<code>docker-ce</code>，社区版，免费。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">yum clean allyum makecache fastyum -y install docker-ce
+</span></span></code></pre></div></li>
+<li>启动服务。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl"> <span class="c1">#service 命令的用法</span>
+</span></span><span class="line"><span class="cl">$ sudo service docker start
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="c1">#systemctl 命令的用法</span>
+</span></span><span class="line"><span class="cl">$ sudo systemctl start docker
+</span></span></code></pre></div></li>
+<li>查看安装版。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker version
+</span></span></code></pre></div></li>
+<li><code>Docker</code>需要用户具有<code>sudo</code>权限，为了避免每次命令都输入<code>sudo</code>，可以把用户加入<code>Docker</code>用户组。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">sudo usermod -aG docker <span class="nv">$USER</span>
+</span></span></code></pre></div></li>
+</ol>
+<h2 id="配置镜像">配置镜像</h2>
+<p>由于网速原因，可以配置一下国内的镜像加速器：</p>
+<ul>
+<li>中科大镜像: <a href="https://docker.mirrors.ustc.edu.cn">https://docker.mirrors.ustc.edu.cn</a></li>
+<li>网易: <a href="https://hub-mirror.c.163.com">https://hub-mirror.c.163.com</a></li>
+<li>阿里云: <a href="https://<%E4%BD%A0%E7%9A%84ID>.mirror.aliyuncs.com">https://&lt;你的ID&gt;.mirror.aliyuncs.com</a></li>
+<li>七牛云加速器: <a href="https://reg-mirror.qiniu.com">https://reg-mirror.qiniu.com</a></li>
+</ul>
+<p>以阿里云获取镜像地址为例， <a href="https://cr.console.aliyun.com/cn-hangzhou/instances/mirrors">https://cr.console.aliyun.com/cn-hangzhou/instances/mirrors</a>登陆后，左侧菜单选中镜像加速器就可以看到你的专属地址了。
+<img alt="获取阿里云docker地址" src="/iblog/posts/annex/images/application/%E8%8E%B7%E5%8F%96%E9%98%BF%E9%87%8C%E4%BA%91docker%E5%9C%B0%E5%9D%80.jpg">
+配置<code>Docker</code>镜像地址，添加以下内容：
+<img alt="docker配置" src="/iblog/posts/annex/images/application/docker%E9%85%8D%E7%BD%AE.jpg"></p>
+<p>也可以创建或编辑<code>/etc/docker/daemon.json</code>文件，并添加以下内容：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">{
+</span></span><span class="line"><span class="cl">  &#34;debug&#34;: true,
+</span></span><span class="line"><span class="cl">  &#34;experimental&#34;: false,
+</span></span><span class="line"><span class="cl">  &#34;registry-mirrors&#34;: [
+</span></span><span class="line"><span class="cl">    &#34;https://docker.mirrors.ustc.edu.cn&#34;
+</span></span><span class="line"><span class="cl">  ]
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>配置文件修改后，需要重启<code>Docker</code>服务使其生效：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">sudo systemctl daemon-reload
+</span></span><span class="line"><span class="cl">sudo systemctl restart docker
+</span></span></code></pre></div><p>在终端执行<code>docker info</code>命令。
+<img alt="docker信息" src="/iblog/posts/annex/images/application/docker%E4%BF%A1%E6%81%AF.jpg"></p>
+<p>出现上图所示，<code>Docker</code>镜像加速器配置成功。</p>
+<h2 id="工作原理">工作原理</h2>
+<p><img alt="docker架构" src="/iblog/posts/annex/images/application/docker%E6%9E%B6%E6%9E%84.png"></p>
+<p><code>Docker</code>架构分为三部分，客户端、宿主机、注册中心。</p>
+<ol>
+<li><code>Docker</code>客户端是用户与<code>Docker</code>交互的接口。用户通过客户端输入命令（如 <code>docker run</code>），这些命令会发送到<code>Docker</code>守护进程来执行。</li>
+<li>宿主机运行<code>Docker</code>守护进程，管理容器的生命周期。宿主机负责从注册中心拉取镜像、创建和管理容器，以及处理与容器相关的所有任务。</li>
+<li><code>Docker</code>注册中心用于存储和分发<code>Docker</code>镜像。常见的公共注册中心是<code>Docker Hub</code>，但用户也可以设置私有的注册中心。注册中心存储镜像，供宿主机下载。</li>
+</ol>
+<p>例如，当输入<code>docker run mysql:5.6</code>命令，告诉<code>Docker</code>要运行一个MySQL 5.6版本的容器。
+<code>Docker</code>客户端将用户的命令发送给宿主机上的<code>Docker</code>守护进程。<code>Docker</code>守护进程首先会在本地检查是否存在<code>mysql:5.6</code>镜像。
+如果本地没有找到<code>mysql:5.6</code>镜像，守护进程会向注册中心请求下载这个镜像。如果本地已经有这个镜像，则跳过下载步骤。
+如果需要从注册中心下载镜像，守护进程会连接到<code>Docker</code>注册中心，并拉取<code>mysql:5.6</code>镜像。
+下载完成后，<code>Docker</code>守护进程会根据<code>mysql:5.6</code>镜像创建一个新的容器。最后<code>Docker</code>守护进程为容器分配资源，并启动容器。MySQL服务会在这个容器内运行起来。</p>
+<h2 id="常用命令">常用命令</h2>
+<ul>
+<li>查看当前运行的镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker ps
+</span></span></code></pre></div><ul>
+<li>查看所有镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker ps -a
+</span></span></code></pre></div><ul>
+<li>停止容器。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker stop 容器名称
+</span></span></code></pre></div><ul>
+<li>删除镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker rmi 镜像名称
+</span></span></code></pre></div><ul>
+<li>下载镜像，若不指定版本为最新版本。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker pull 镜像:版本
+</span></span></code></pre></div><ul>
+<li>查看当前本地仓库的镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker images
+</span></span></code></pre></div><ul>
+<li>查看远程仓库镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker search 镜像名
+</span></span></code></pre></div><p>以安装运行<code>nginx</code>为例。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">// docker run 包括下载镜像<span class="o">(</span>pull<span class="o">)</span>,创建容器<span class="o">(</span>create<span class="o">)</span>,运行容器<span class="o">(</span>start<span class="o">)</span> 可用dock -h查看帮助
+</span></span><span class="line"><span class="cl">// --rm 表明这是一个临时的容器,关闭的话会自动删除
+</span></span><span class="line"><span class="cl">// --name 容器名称
+</span></span><span class="line"><span class="cl">// -p 外部服务器端口映射docker容器端口
+</span></span><span class="line"><span class="cl">docker run --rm --name myNginx -p 80:80 nginx:版本
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 查看容器日志
+</span></span><span class="line"><span class="cl">docker logs myNginx
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 进入容器
+</span></span><span class="line"><span class="cl">docker <span class="nb">exec</span> -it myNginx bash
+</span></span></code></pre></div></div>
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+                <a class="nav-link text-left" href="#es6-es11httpswwwbilibilicomvideobv1uk411h7on">
+                    ES6-ES11
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#css%e9%a2%84%e5%a4%84%e7%90%86%e5%99%a8">
+                    CSS预处理器
+                </a>
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#nodehttpswwwbilibilicomvideobv1gm411w7ex">
+                    Node
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#promisehttpswwwbilibilicomvideobv1ga411x7z1">
+                    Promise
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#axioshttpswwwbilibilicomvideobv1wr4y1k7tq">
+                    Axios
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
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+        
+        
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+        
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b7%a5%e5%85%b7">
+                    工具
+                </a>
+            </li>
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+        </ul>
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%bb%e6%b5%81%e6%8a%80%e6%9c%af">
+                    主流技术
+                </a>
+            </li>
+            
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+        </ul>
+        
+        </ul>
+        
+        
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+                <a class="nav-link text-left" href="#%e9%9d%99%e6%80%81%e7%ab%99%e7%82%b9%e7%94%9f%e6%88%90%e5%99%a8">
+                    静态站点生成器
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+        
+        
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%a7%bb%e5%8a%a8%e7%ab%af">
+                    移动端
+                </a>
+            </li>
+            
+            
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+        
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+        
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+        
+        
+        
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+                <a class="nav-link text-left" href="#%e5%be%ae%e4%bf%a1%e5%b0%8f%e7%a8%8b%e5%ba%8fhttpswwwbilibilicomvideobv12k411a7a2">
+                    微信小程序
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+            
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#native-app">
+                    Native App
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+        
+        
+        
+        
+        
+        <ul class="nav">
+            
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+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%89%e5%8d%93%e5%8e%9f%e7%94%9fhttpswwwbilibilicomvideobv19u4y1r7zv">
+                    安卓原生
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+        
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+            
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+            
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#ios%e5%8e%9f%e7%94%9fhttpswwwbilibilicomvideobv1tt411a7xa">
+                    IOS原生
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
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+        
+        
+        
+        
+        
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+            
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+            
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%b8%bf%e8%92%99%e5%8e%9f%e7%94%9fhttpswwwbilibilicomvideobv1ti4y1s79b">
+                    鸿蒙原生
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
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+        
+        
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+        
+        
+        
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+        <ul class="nav">
+            
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+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#web-app">
+                    Web App
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hybird-app">
+                    Hybird App
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#uni-apphttpswwwbilibilicomvideobv1bj411w7px">
+                    Uni-App
+                </a>
+            </li>
+            
+            
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#taro">
+                    Taro
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+            </li>
+            
+            
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+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
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+            
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+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#react-nativehttpswwwbilibilicomvideobv1pt4y1n7bd">
+                    React Native
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
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+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#flutter">
+                    Flutter
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
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+        
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+        
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+        <ul class="nav">
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+            
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+                <a class="nav-link text-left" href="#%e6%80%a7%e8%83%bd%e4%bc%98%e5%8c%96%e5%92%8c%e7%9b%91%e6%8e%a7">
+                    性能优化和监控
+                </a>
+            </li>
+            
+            
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+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%a7%e8%83%bd%e4%bc%98%e5%8c%96%e6%a6%82%e8%a7%88httpswwwbilibilicomvideobv1kr4y1l7tk">
+                    性能优化概览
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b5%8f%e8%a7%88%e5%99%a8%e5%8f%8a%e5%b7%a5%e4%bd%9c%e6%96%b9%e5%bc%8fhttpswwwbilibilicomvideobv1x54y1b7re">
+                    浏览器及工作方式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#seohttpswwwbilibilicomvideobv1fe411j7ya">
+                    SEO
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b5%84%e6%ba%90%e7%ae%a1%e7%90%86">
+                    资源管理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_pic" title="导出图片" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1689071509720" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="4564" width="16" height="16"><path d="M909.132886 0.037506h-184.960611a33.909445 33.909445 0 0 0-32.368107 33.909445 33.909445 33.909445 0 0 0 33.909445 33.395666h158.244078l-200.373995 199.346437a33.395666 33.395666 0 0 0 0 47.781491 31.854327 31.854327 0 0 0 23.633856 9.76181 33.909445 33.909445 0 0 0 24.147635-9.76181l198.832657-199.346437V272.340628a33.909445 33.909445 0 0 0 69.874009 0V88.921355A88.37007 88.37007 0 0 0 909.132886 0.037506zM216.558153 347.866211a107.37991 107.37991 0 1 0 107.37991-107.379911 107.89369 107.89369 0 0 0-107.37991 107.379911z m154.133843 0a51.377948 51.377948 0 0 1-97.618101 0 51.377948 51.377948 0 1 1 97.618101 0z" p-id="4565" fill="#424242"></path><path d="M963.079731 437.777619a34.423225 34.423225 0 0 0-33.909446 33.909445v265.110209a1811.07265 1811.07265 0 0 0-137.692899-193.181082 106.352351 106.352351 0 0 0-78.60826-36.478343 123.820854 123.820854 0 0 0-82.204716 35.964563l-3.596456 3.082677-188.557068 176.74014c-11.816928-13.358266-47.781491-51.377948-82.204716-87.856291a83.232275 83.232275 0 0 0-85.801172-21.578738 105.324792 105.324792 0 0 0-38.019681 19.52362l-141.289356 121.765736V89.948914a22.092517 22.092517 0 0 1 22.606297-22.606297h417.702713a33.395666 33.395666 0 0 0 33.395666-33.909445 33.395666 33.395666 0 0 0-33.395666-33.395666H113.802258A89.911408 89.911408 0 0 0 23.89085 89.948914v844.139678a89.911408 89.911408 0 0 0 89.911408 89.911408h793.27551a89.911408 89.911408 0 0 0 89.397629-89.911408v-462.401528a33.909445 33.909445 0 0 0-33.395666-33.909445z m-33.909446 496.310973a22.606297 22.606297 0 0 1-22.092517 22.606297H113.802258a22.606297 22.606297 0 0 1-22.606297-22.606297v-88.37007l183.933052-160.812976a43.157476 43.157476 0 0 1 15.413385-7.192912 15.927164 15.927164 0 0 1 17.982281 5.137794c37.505902 36.478343 78.60826 83.232275 82.718496 87.856291a61.653537 61.653537 0 0 0 42.643696 22.092517 62.681096 62.681096 0 0 0 51.377948-20.037399c8.220472-8.220472 134.610223-125.875971 194.208641-181.877935a57.029522 57.029522 0 0 1 34.423225-16.440943 45.212594 45.212594 0 0 1 29.79921 15.927164 2954.231982 2954.231982 0 0 1 186.501949 256.889738z" p-id="4566" fill="#424242"></path></svg>
+                    </a>
+                    <a id="export_markdown" title="导出markdown" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_doc" title="导出文档" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1689246982401" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="6825" width="16" height="16"><path d="M270.76864 608.32h180.8a31.68 31.68 0 0 0 0-62.976H270.76864a31.68 31.68 0 0 0 0 62.976zM271.34464 458.56h457.92a33.472 33.472 0 0 0 31.552-34.752 33.28 33.28 0 0 0-31.552-34.624H271.34464a34.816 34.816 0 0 0 0 69.376zM271.34464 293.504h457.92a33.344 33.344 0 0 0 31.552-34.688 33.216 33.216 0 0 0-31.552-34.624H271.34464a33.28 33.28 0 0 0-31.616 34.624 33.28 33.28 0 0 0 31.616 34.688z" p-id="6826" fill="#424242"></path><path d="M869.87264 0H153.77664A70.4 70.4 0 0 0 84.65664 70.912V953.6A69.952 69.952 0 0 0 153.77664 1024h370.048a32 32 0 0 0 0-63.68H147.12064V64h729.6v468.672a31.296 31.296 0 1 0 62.528 0V70.912A70.4 70.4 0 0 0 869.87264 0z" p-id="6827" fill="#424242"></path><path d="M482.16064 730.624h337.664L715.82464 625.216a28.864 28.864 0 0 1-7.936-28.736 29.184 29.184 0 0 1 20.608-21.184 29.632 29.632 0 0 1 29.12 8.128l174.784 177.216-174.784 176.96a29.184 29.184 0 0 1-49.728-13.312 29.248 29.248 0 0 1 8-28.8l103.936-105.344H482.16064a29.696 29.696 0 0 1-29.504-29.76 29.632 29.632 0 0 1 29.504-29.76z" p-id="6828" fill="#424242"></path></svg>
+                    </a>
+                </span>
+                <a  id="icon_more" title="更多" >
+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
+                </a>
+                <a  id="icon_less" class="display_none">
+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">前端学习路线</h2>
+                        <span id="post_page_title_date" class="date">2024.02.29</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><p><a href="/iblog/posts/annex/xmind/%E5%89%8D%E7%AB%AF%E7%9F%A5%E8%AF%86%E7%82%B9.xmind"><img alt="前端知识点" src="/iblog/posts/annex/images/essays/%E5%89%8D%E7%AB%AF%E7%9F%A5%E8%AF%86%E7%82%B9.png"></a></p>
+<h2 id="基础知识">基础知识</h2>
+<h3 id="网络知识">网络知识</h3>
+<ol>
+<li><a href="https://www.bilibili.com/video/BV1js411g7Fw/">HTTP</a></li>
+<li><a href="https://www.bilibili.com/video/BV1GW411j7Ts/">DNS</a></li>
+<li><a href="https://www.bilibili.com/video/BV1zA411x7Pj/">域名</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Rt411u7k4/">云服务</a></li>
+<li>网络安全
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1Up4y1i7PG/">HTTPS</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Kt411E76z/">CORS</a></li>
+<li><a href="https://www.bilibili.com/video/BV1kh411W7Vv/">网络渗透</a></li>
+<li><a href="https://www.bilibili.com/video/BV1ey4y1V7Jj/">OWASP</a></li>
+</ul>
+</li>
+</ol>
+<h3 id="htmlhttpswwwbilibilicomvideobv1p84y1p7z5"><a href="https://www.bilibili.com/video/BV1p84y1P7Z5/">HTML</a></h3>
+<h3 id="csshttpswwwbilibilicomvideobv1p84y1p7z5"><a href="https://www.bilibili.com/video/BV1p84y1P7Z5/">CSS</a></h3>
+<h3 id="javascripthttpswwwbilibilicomvideobv1yw411t7gx"><a href="https://www.bilibili.com/video/BV1YW411T7GX/">JavaScript</a></h3>
+<h3 id="jqueryhttpswwwbilibilicomvideobv1ts411e7ag"><a href="https://www.bilibili.com/video/BV1ts411E7ag/">JQuery</a></h3>
+<h3 id="ajaxhttpswwwbilibilicomvideobv1wc4y1b78y"><a href="https://www.bilibili.com/video/BV1WC4y1b78y/">Ajax</a></h3>
+<h3 id="es6-es11httpswwwbilibilicomvideobv1uk411h7on"><a href="https://www.bilibili.com/video/BV1uK411H7on/">ES6-ES11</a></h3>
+<h3 id="综合应用httpswwwbilibilicomvideobv1ra411x7rx"><a href="https://www.bilibili.com/video/BV1ra411X7RX/">综合应用</a></h3>
+<hr>
+<h2 id="工程化体系">工程化体系</h2>
+<h3 id="代码规范httpswwwbilibilicomvideobv19p4y147jz"><a href="https://www.bilibili.com/video/BV19P4y147Jz/">代码规范</a></h3>
+<h3 id="css预处理器">CSS预处理器</h3>
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1YW411T7vd/">Less</a></li>
+<li><a href="https://www.bilibili.com/video/BV1RJ4113717/">Sass</a></li>
+<li>PostCSS</li>
+</ul>
+<h3 id="nodehttpswwwbilibilicomvideobv1gm411w7ex"><a href="https://www.bilibili.com/video/BV1gM411W7ex/">Node</a></h3>
+<h3 id="promisehttpswwwbilibilicomvideobv1ga411x7z1"><a href="https://www.bilibili.com/video/BV1GA411x7z1/">Promise</a></h3>
+<h3 id="axioshttpswwwbilibilicomvideobv1wr4y1k7tq"><a href="https://www.bilibili.com/video/BV1wr4y1K7tq/">Axios</a></h3>
+<h3 id="工具">工具</h3>
+<ol>
+<li>包管理工具
+<ul>
+<li><a href="https://www.imooc.com/learn/766">Yarn</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Dv411W7XP/">Npm</a></li>
+</ul>
+</li>
+<li>打包工具
+<ul>
+<li><a href="https://www.bilibili.com/video/BV14T4y1z7sw/">Webpack</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Pa4y147Kf/">Parcel</a></li>
+</ul>
+</li>
+<li>代码格式化工具
+<ul>
+<li><a href="https://space.bilibili.com/390120104/search/video?keyword=ESLint">ESLint</a></li>
+<li><a href="https://www.bilibili.com/video/BV183411r7YK/">Prettier</a></li>
+</ul>
+</li>
+<li>调试工具
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1KM4y1G7EF/">Chrome</a></li>
+<li><a href="https://www.cnblogs.com/Christeen/p/6612697.html">IETest</a></li>
+<li><a href="https://www.bilibili.com/video/BV1r34y1d7Kz/">Postman</a></li>
+</ul>
+</li>
+<li>版本管理工具
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1FE411P7B3/">Git</a></li>
+<li><a href="https://www.bilibili.com/video/BV11E411x7Uv/">GitLab</a></li>
+<li><a href="https://www.bilibili.com/video/BV1yo4y1d7UK/">GitHub</a></li>
+</ul>
+</li>
+<li>部署发布工具
+<ul>
+<li><a href="https://www.bilibili.com/video/BV12y4y1M7jU/">Jenkins</a></li>
+<li><a href="https://www.bilibili.com/video/BV1u14y1o7DW/">CICD</a></li>
+</ul>
+</li>
+</ol>
+<h3 id="主流技术">主流技术</h3>
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1Xy4y1v7S2/">TypeScript</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Zy4y1K7SH/">Vue</a></li>
+<li><a href="https://www.bilibili.com/video/BV1wy4y1D7JT/">React</a></li>
+<li><a href="https://www.bilibili.com/video/BV1ts411E7qg/">Angular</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Xh411V7b5/">综合应用</a></li>
+</ul>
+<hr>
+<h2 id="静态站点生成器">静态站点生成器</h2>
+<ul>
+<li><a href="https://www.bilibili.com/video/BV13441117KK/">Next</a></li>
+<li><a href="https://www.gatsbyjs.cn/">GatsbyJS</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Xt41117Kg/">Nuxt</a></li>
+<li><a href="https://www.bilibili.com/video/BV1vb411m7NY/">Vuepress</a></li>
+<li><a href="https://www.bilibili.com/video/BV1x64y117PX/">Hugo</a></li>
+</ul>
+<hr>
+<h2 id="移动端">移动端</h2>
+<h3 id="微信小程序httpswwwbilibilicomvideobv12k411a7a2"><a href="https://www.bilibili.com/video/BV12K411A7A2/">微信小程序</a></h3>
+<h3 id="native-app">Native App</h3>
+<p>原生APP开发模式</p>
+<p>优点:</p>
+<ol>
+<li>可轻易调用手机所有硬件实现功能</li>
+<li>速度更快、性能高、整体用户体验最好</li>
+<li>质量安全性很高</li>
+</ol>
+<p>缺点：</p>
+<ol>
+<li>开发周期长及维护成本高(比如ios和android需2端开发2个app)</li>
+<li>学习成本高(ios必须会swift，android必须会Java)</li>
+</ol>
+<h4 id="安卓原生httpswwwbilibilicomvideobv19u4y1r7zv"><a href="https://www.bilibili.com/video/BV19U4y1R7zV/">安卓原生</a></h4>
+<h4 id="ios原生httpswwwbilibilicomvideobv1tt411a7xa"><a href="https://www.bilibili.com/video/BV1Tt411a7Xa/">IOS原生</a></h4>
+<h4 id="鸿蒙原生httpswwwbilibilicomvideobv1ti4y1s79b"><a href="https://www.bilibili.com/video/BV1Ti4y1s79B/">鸿蒙原生</a></h4>
+<h3 id="web-app">Web App</h3>
+<p>HTML5 APP 框架开发模式，Web App即我们通常所说的H5 app，主要通过HTML，CSS，JS构建页面，然后发布到服务器，用户通过手机网络访问这些页面。类似微信公众号等。</p>
+<p>优点:</p>
+<ol>
+<li>项目独立，维护更容易，兼容多平台</li>
+<li>开发周期短，学习成本低</li>
+<li>更新发版更容易</li>
+</ol>
+<p>缺点：</p>
+<ol>
+<li>体验不好，对设备和网络要求高，经常卡顿，性能差</li>
+<li>无法调用系统硬件</li>
+</ol>
+<h3 id="hybird-app">Hybird App</h3>
+<p>混合模式移动应用，介于Web App、Native App这两者之间的app， Hybrid App主要以JS+Native两者相互调用为主，从开发层面现“一次开发，多处运行”的机制，成为真正适合跨平台的开发，是目前乃至未来发展的趋势。</p>
+<p>优点:</p>
+<ol>
+<li>维护容易，能调用部分系统硬件，兼容多平台</li>
+<li>开发周期短，学习成本低</li>
+</ol>
+<p>缺点：</p>
+<ol>
+<li>可能需要会原生开发以支持更多的硬件调用</li>
+<li>性能跟原生还是有差距，对设备有一定要求</li>
+</ol>
+<h4 id="uni-apphttpswwwbilibilicomvideobv1bj411w7px"><a href="https://www.bilibili.com/video/BV1BJ411W7pX/">Uni-App</a></h4>
+<h4 id="taro">Taro</h4>
+<h4 id="react-nativehttpswwwbilibilicomvideobv1pt4y1n7bd"><a href="https://www.bilibili.com/video/BV1Pt4y1n7bD/">React Native</a></h4>
+<h4 id="flutter">Flutter</h4>
+<ul>
+<li><a href="https://www.bilibili.com/video/BV15t411U7yf/">基础</a></li>
+<li><a href="https://www.bilibili.com/video/BV1kt411B7mu/">实战</a></li>
+</ul>
+<hr>
+<h2 id="性能优化和监控">性能优化和监控</h2>
+<h3 id="性能优化概览httpswwwbilibilicomvideobv1kr4y1l7tk"><a href="https://www.bilibili.com/video/BV1KR4y1L7TK/">性能优化概览</a></h3>
+<h3 id="浏览器及工作方式httpswwwbilibilicomvideobv1x54y1b7re"><a href="https://www.bilibili.com/video/BV1x54y1B7RE/">浏览器及工作方式</a></h3>
+<h3 id="seohttpswwwbilibilicomvideobv1fe411j7ya"><a href="https://www.bilibili.com/video/BV1fE411J7ya/">SEO</a></h3>
+<h3 id="资源管理">资源管理</h3>
+<ul>
+<li>延迟加载</li>
+<li>按需加载</li>
+<li>缓存复用</li>
+<li>CDN部署</li>
+<li>请求合并</li>
+<li>异步同步</li>
+</ul>
+</div>
+                    <div id="post_footer" class="post_footer">
+                        <div class="meta">
+                            
+                            <div id="post_footer_info" class="info">
+                                <span class="field tags">
+                                    <i class="ri-stack-line"></i>
+                                    
+                                        
+                                        <a href="http://localhost:1313/iblog/tags/%E5%AD%A6%E4%B9%A0%E8%B7%AF%E7%BA%BF/">学习路线</a>
+                                    
+                                        <a href="http://localhost:1313/iblog/tags/%E5%B0%B1%E4%B8%9A/">就业</a>
+                                    
+                                    
+                                </span>
+                            </div>
+                        </div>
+                    </div>
+                </div>
+                
+                
+                
+<div id="doc_comments" class="doc_comments">
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\ No newline at end of file
diff --git a/blog-site/public/posts/javabasics/rookie-datatype/index.html b/blog-site/public/posts/javabasics/rookie-datatype/index.html
new file mode 100644
index 00000000..1d01d727
--- /dev/null
+++ b/blog-site/public/posts/javabasics/rookie-datatype/index.html
@@ -0,0 +1,2434 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java数据类型 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="基本类型 Java语言提供了八种基本类型。六种数值类型（四个整数型，两个浮点型），一种字符类型，还有一种布尔型，俗称4类8种。 这里只介绍称4类8种，实际上，Jav" />
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+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e6%9c%ac%e7%b1%bb%e5%9e%8b">
+                    基本类型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e6%9c%ac%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2">
+                    基本类型转换
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%98%be%e5%bc%8f%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2">
+                    显式类型转换
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9a%90%e5%bc%8f%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2">
+                    隐式类型转换
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8c%85%e8%a3%85%e7%b1%bb%e5%9e%8b">
+                    包装类型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8b%86%e7%ae%b1%e4%b8%8e%e8%a3%85%e7%ae%b1">
+                    拆箱与装箱
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%ad%98%e6%b1%a0">
+                    缓存池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%95%e7%94%a8%e7%b1%bb%e5%9e%8b">
+                    引用类型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%95%e7%94%a8%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2">
+                    引用类型转换
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e8%b1%a1%e7%9a%84%e6%af%94%e8%be%83">
+                    对象的比较
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e9%87%8f">
+                    常量
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9a%e4%b9%89%e5%b8%b8%e9%87%8f">
+                    定义常量
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#class%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    Class常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%90%e8%a1%8c%e6%97%b6%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    运行时常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ba%e4%bb%80%e4%b9%88%e9%9c%80%e8%a6%81%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    为什么需要常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#string%e7%b1%bb%e5%9e%8b">
+                    String类型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ba%e4%bb%80%e4%b9%88jdk9%e6%94%b9%e5%8f%98%e4%ba%86%e5%ad%98%e5%82%a8%e7%bb%93%e6%9e%84">
+                    为什么JDK9改变了存储结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%8d%e5%8f%af%e5%8f%98%e6%80%a7">
+                    不可变性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#new-stringabc%e4%bc%9a%e5%88%9b%e5%bb%ba%e5%87%a0%e4%b8%aa%e5%af%b9%e8%b1%a1">
+                    new String(“abc”)会创建几个对象
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ad%97%e7%ac%a6%e4%b8%b2%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    字符串常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#intern%e6%96%b9%e6%b3%95">
+                    intern方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ad%97%e7%ac%a6%e4%b8%b2%e5%b8%b8%e9%87%8f%e6%b1%a0%e9%95%bf%e5%ba%a6">
+                    字符串常量池长度
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8">
+                    使用
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%9b%e5%bb%ba%e5%ad%97%e7%ac%a6%e4%b8%b2">
+                    创建字符串
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8b%bc%e6%8e%a5%e5%ad%97%e7%ac%a6%e4%b8%b2">
+                    拼接字符串
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8b%bc%e6%8e%a5%e5%8e%9f%e7%90%86">
+                    “&#43;”拼接原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#stringbuffer%e4%b8%8estringbuilder">
+                    StringBuffer与StringBuilder
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e7%94%a8%e6%96%b9%e6%b3%95">
+                    常用方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%95%bf%e5%ba%a6%e9%99%90%e5%88%b6">
+                    长度限制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#string%e7%b1%bb%e4%b8%8e%e7%bc%96%e7%a0%81">
+                    String类与编码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#unicode">
+                    Unicode
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%96%e7%a0%81%e4%b8%8e%e8%a7%a3%e7%a0%81">
+                    编码与解码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1688701481347" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3517" width="16" height="16"><path d="M425.610455 85.814544H149.05897A42.303635 42.303635 0 0 0 106.6274 128.075535V896.492068c0 23.326702 18.976933 42.26099 42.43157 42.26099h682.743143a42.559504 42.559504 0 0 0 42.431569-42.559504v-384.016365a42.644793 42.644793 0 0 1 85.289587 0v384.016365A127.849091 127.849091 0 0 1 831.802113 1024H149.05897A127.635867 127.635867 0 0 1 21.337813 896.449423V128.03289A127.593222 127.593222 0 0 1 149.101614 0.524957h276.466196a42.644793 42.644793 0 0 1 0 85.289587z m564.062683 158.08425l-170.579174 170.579173a42.644793 42.644793 0 1 1-60.299738-60.299738L856.578738 256.393718H618.364922a42.644793 42.644793 0 1 1 0-85.289587h238.213816l-97.784512-97.784511A42.644793 42.644793 0 1 1 819.093964 13.019882l170.579174 170.579174a42.644793 42.644793 0 0 1 0 60.299738zM149.272194 597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h51.514911c59.190973 0 107.891327 23.284057 107.976617 97.102195 0 71.003581-49.46796 102.347504-106.185536 102.347504h-31.343923v66.781747a32.282109 32.282109 0 0 1-64.606862 0V597.552066z m92.709781 100.215264c31.429213 0 46.568114-16.46089 46.568114-45.757863 0-30.064579-17.313786-40.512554-48.359196-40.512554h-26.311837v86.270417h28.145563z m232.414124-142.860058c81.878003 0 136.036891 43.710913 136.036891 147.67892S556.231457 853.420826 477.935617 853.420826h-38.16709a42.644793 42.644793 0 0 1-42.644794-42.644793v-213.223967a42.644793 42.644793 0 0 1 42.644794-42.644794h34.542282z m-4.008611 240.729859c43.32711 0 73.988717-22.047358 73.988717-93.050939 0-71.046226-30.704251-90.705476-73.988717-90.705476h-8.699538v183.79906h8.699538zM692.481573 853.420826a32.282109 32.282109 0 0 1-32.282109-32.282108V597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h99.063855a29.680776 29.680776 0 1 1 0 59.404197h-77.144431v65.374469h61.749661a29.894 29.894 0 1 1 0 59.788h-61.749661v81.66478a32.282109 32.282109 0 0 1-32.282108 32.282108z" fill="#5f5f5f" p-id="3518"></path></svg>
+                    </a>
+                    <a id="export_pic" title="导出图片" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                        <h2 id="post_single_title">Java数据类型</h2>
+                        <span id="post_page_title_date" class="date">2021.01.20</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
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+                    <div class="post_content markdown"><h2 id="基本类型">基本类型</h2>
+<p>Java语言提供了八种基本类型。六种数值类型（四个整数型，两个浮点型），一种字符类型，还有一种布尔型，俗称4类8种。
+这里只介绍称4类8种，实际上，Java中还存在另外一种基本类型 <code>void</code>，它也有对应的包装类<code>java.lang.Void</code>，不过我们无法直接对它们进行操作。</p>
+<table>
+<thead>
+<tr>
+<th>类型</th>
+<th>位数</th>
+<th>范围</th>
+<th>默认值</th>
+<th>示例</th>
+<th>备注</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>byte</td>
+<td>8</td>
+<td>-128 ~ 127</td>
+<td>0</td>
+<td><code>byte a = 100</code> <code>byte b = -50</code></td>
+<td>节省空间，常用于大型数组</td>
+</tr>
+<tr>
+<td>short</td>
+<td>16</td>
+<td>-2^15 ~ 2^15-1</td>
+<td>0</td>
+<td><code>short s = 1000</code> <code>short r = -20000</code></td>
+<td>节省空间，int变量占用空间的一半</td>
+</tr>
+<tr>
+<td>int</td>
+<td>32</td>
+<td>-2^31 ~ 2^31-1</td>
+<td>0</td>
+<td><code>int a = 100000</code> <code>int b = -200000</code></td>
+<td>默认的整型变量</td>
+</tr>
+<tr>
+<td>long</td>
+<td>64</td>
+<td>-2^63 ~ 2^63-1</td>
+<td>0L</td>
+<td><code>long a = 100000L</code> <code>long b = -200000L</code></td>
+<td>用于表示较大整数</td>
+</tr>
+<tr>
+<td>float</td>
+<td>32</td>
+<td>1.4E-45 ~ 3.4028235E38</td>
+<td>0.0f</td>
+<td><code>float f = 234.5f</code></td>
+<td>单精度浮点数，节省内存，不能表示精确值</td>
+</tr>
+<tr>
+<td>double</td>
+<td>64</td>
+<td>4.9E-324 ~ 1.7976931348623157E308</td>
+<td>0.0d</td>
+<td><code>double d = 123.4</code></td>
+<td>双精度浮点数，默认的浮点数类型，不能表示精确值</td>
+</tr>
+<tr>
+<td>char</td>
+<td>16</td>
+<td>\u0000 (0) ~ \uffff (65,535)</td>
+<td>\u0000</td>
+<td><code>char letter = 'A'</code></td>
+<td>存储单一的 Unicode 字符</td>
+</tr>
+<tr>
+<td>boolean</td>
+<td>~</td>
+<td>true, false</td>
+<td>false</td>
+<td><code>boolean one = true</code></td>
+<td>JVM 在编译时将 boolean 转换为 int，使用 1 表示 true，0 表示 false。</td>
+</tr>
+</tbody>
+</table>
+<p>一个byte(字节)等于8个bit(位)，bit是最小的单位，1b(字节)=8bit(位)。一般情况下，一个汉字是两个字节，英文与数字是一个字节。</p>
+<p><code>Float</code>和<code>Double</code>的最小值和最大值都是以科学记数法的形式输出的，结尾的&quot;E+数字&quot;表示E之前的数字要乘以10的多少次方，比如<code>3.14E3</code>就是<code>3.14 × 10^3</code>，<code>3.14E-3</code> 就是 <code>3.14 x 10^-3</code>。</p>
+<p>boolean 只有两个值，<code>true、false</code>，可以使用 1 bit 来存储，但是具体大小没有明确规定。
+JVM 会在编译时期将 boolean 类型的数据转换为 int，使用 1 来表示 true，0 表示 false。JVM 支持 boolean 数组，但是是通过读写 byte 数组来实现的。</p>
+<h3 id="基本类型转换">基本类型转换</h3>
+<p>在Java中，类型转换是将一种数据类型的值转换为另一种数据类型的过程。
+整型、常量、字符型数据可以混合运算。运算前，不同类型的数据先转化为同一类型，然后进行运算。</p>
+<p>基本类型的类型转换主要分为两类，隐式类型转换（自动类型转换）和显式类型转换（强制类型转换）。
+这些类型转换是为了处理不同数据类型之间的转换需求和类型匹配问题。</p>
+<p>基本数据类型转换时需注意：</p>
+<ul>
+<li>不能对boolean类型进行类型转换；</li>
+<li>不能把对象类型转换成不相关类的对象；</li>
+<li>在把容量大的类型转换为容量小的类型时必须使用强制类型转换；</li>
+<li>浮点数到整数的转换是通过舍弃小数得到，而不是四舍五入；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">(int)23.7 == 23;        
+</span></span><span class="line"><span class="cl">(int)-45.89f == -45
+</span></span></code></pre></div></li>
+<li>转换过程中可能导致溢出或损失精度，在运算时要避免该问题。例如：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">// 因为 byte 类型是 8 位，最大值为127，所以当 int 强制转换为 byte 类型时，值 128 时候就会导致溢出
+</span></span><span class="line"><span class="cl">int i =128;   
+</span></span><span class="line"><span class="cl">byte b = (byte)i;
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="显式类型转换">显式类型转换</h4>
+<p>显式类型转换也叫强制类型转换，显式类型转换在可能出现数据丢失或溢出的风险的情况下进行，需要使用强制类型转换运算符。
+基本类型的显式转换顺序：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">double -&gt; float -&gt; long -&gt; int -&gt; short -&gt; byte
+</span></span><span class="line"><span class="cl">double -&gt; float -&gt; long -&gt; int -&gt; char
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// double -&gt; float -&gt; long -&gt; int -&gt; short -&gt; byte</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">doubleValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">.</span><span class="na">04</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">float</span><span class="w"> </span><span class="n">floatValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="w"> </span><span class="n">doubleValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">longValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">long</span><span class="p">)</span><span class="w"> </span><span class="n">floatValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">intValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="n">longValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">short</span><span class="w"> </span><span class="n">shortValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">short</span><span class="p">)</span><span class="w"> </span><span class="n">intValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">byte</span><span class="w"> </span><span class="n">byteValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">shortValue</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// double -&gt; float -&gt; long -&gt; int -&gt; char</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">doubleVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">97</span><span class="p">.</span><span class="na">04</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">float</span><span class="w"> </span><span class="n">floatVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="w"> </span><span class="n">doubleVal</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">longVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">long</span><span class="p">)</span><span class="w"> </span><span class="n">floatVal</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">intVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="n">longVal</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">char</span><span class="w"> </span><span class="n">charValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">char</span><span class="p">)</span><span class="w"> </span><span class="n">intVal</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><h4 id="隐式类型转换">隐式类型转换</h4>
+<p>隐式类型转换是指编译器在编译时自动完成的类型转换，也称为自动类型转换。与显示类型转换相反，这种转换通常在没有数据丢失风险的情况下进行。
+Java 会自动将较小的基本数据类型转换为较大的基本数据类型，以避免数据丢失。转换顺序如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">byte -&gt; short -&gt; int -&gt; long -&gt; float -&gt; double
+</span></span><span class="line"><span class="cl">char -&gt; int -&gt; long -&gt; float -&gt; double
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// byte -&gt; short -&gt; int -&gt; long -&gt; float -&gt; double</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">byte</span><span class="w"> </span><span class="n">byteValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">42</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">short</span><span class="w"> </span><span class="n">shortValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">byteValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">intValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">shortValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">longValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">intValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">float</span><span class="w"> </span><span class="n">floatValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">longValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">doubleValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">floatValue</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// char -&gt; int -&gt; long -&gt; float -&gt; double</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">char</span><span class="w"> </span><span class="n">charValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">&#39;A&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">charToInt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">charValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">charToLong</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">charToInt</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">float</span><span class="w"> </span><span class="n">charToFloat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">charToLong</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">charToDouble</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">charToFloat</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>隐式类型转换还有一种比较特殊的情况，对于 += 运算符来说，如果左右两边的操作数类型不同，编译器会自动将右边操作数的类型转换为左边操作数的类型，然后执行加法操作和赋值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AdditionAssignment</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="w"> </span><span class="n">byteValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">byteValue</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="c1">// 等价于 byteValue = (byte)(byteValue + 5);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">intValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">longValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">200L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">intValue</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">longValue</span><span class="p">;</span><span class="w"> </span><span class="c1">// 等价于 intValue = (int)(intValue + longValue);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">float</span><span class="w"> </span><span class="n">floatValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">.</span><span class="na">5f</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">double</span><span class="w"> </span><span class="n">doubleValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">20</span><span class="p">.</span><span class="na">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">floatValue</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">doubleValue</span><span class="p">;</span><span class="w"> </span><span class="c1">// 等价于 floatValue = (float)(floatValue + doubleValue);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="包装类型">包装类型</h3>
+<table>
+<thead>
+<tr>
+<th>基本类型</th>
+<th>包装类型</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>byte</td>
+<td>Byte</td>
+</tr>
+<tr>
+<td>boolean</td>
+<td>Boolean</td>
+</tr>
+<tr>
+<td>short</td>
+<td>Short</td>
+</tr>
+<tr>
+<td>char</td>
+<td>Character</td>
+</tr>
+<tr>
+<td>int</td>
+<td>Integer</td>
+</tr>
+<tr>
+<td>long</td>
+<td>Long</td>
+</tr>
+<tr>
+<td>float</td>
+<td>Float</td>
+</tr>
+<tr>
+<td>double</td>
+<td>Double</td>
+</tr>
+</tbody>
+</table>
+<p>在这八个类名中，除了 <code>Integer</code> 和 <code>Character</code> 类以外，其它六个类的类名和基本数据类型一致，只是类名的第一个字母大写。
+其中<code>Integer、Long、Byte、Double、Float、Short</code>都是抽象类<code>Number</code>的子类。</p>
+<p>因为 Java 是一种面向对象语言，很多地方都需要使用对象而不是基本数据类型。
+比如在集合类中，我们是无法将<code> int 、double</code> 等类型放进去的，因为集合的容器要求元素是 <code>Object</code> 类型，所以才有了对应基本类型分包装类型。</p>
+<h4 id="拆箱与装箱">拆箱与装箱</h4>
+<p>基本类型都有对应的包装类型，基本类型与其对应的包装类型之间的赋值使用<strong>自动装箱与拆箱</strong>完成。以<code>Integer</code>转<code>int</code> 为例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Integer x = 2;     // 装箱 调用了 Integer.valueOf(2)
+</span></span><span class="line"><span class="cl">int y = x;         // 拆箱 调用了 X.intValue()
+</span></span></code></pre></div><ul>
+<li>自动装箱: 将基本数据类型自动转换成对应的包装类；</li>
+<li>自动拆箱：将包装类自动转换成对应的基本数据类型；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Integer i = 10;  //自动装箱
+</span></span><span class="line"><span class="cl">int b = i;     //自动拆箱
+</span></span></code></pre></div><p>为了探究自动拆箱、自动装箱的原理，将以下代码进行编译，查看<code>class</code>文件：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="n">args</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Integer</span><span class="w"> </span><span class="n">integer</span><span class="o">=</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">integer</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>反编译得到</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="n">args</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Integer</span><span class="w"> </span><span class="n">integer</span><span class="o">=</span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">integer</span><span class="p">.</span><span class="na">intValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>int</code>的自动装箱是通过<code>Integer.valueOf()</code>方法来实现的，<code>Integer</code>的自动拆箱都是通过 <code>integer.intValue</code>来实现的。</p>
+<p>其实自动装箱和自动拆箱是Java中的语法糖，用于简化基本数据类型和其对应包装类型之间的转换操作。
+当将基本数据类型赋值给对应的包装类型时，编译器会调用包装类型的<code>valueOf()</code>方法来创建一个包装对象，并将基本数据类型的值传递给这个方法。
+当需要使用包装类型对象中的值进行基本数据类型的操作时，编译器会自动调用包装类型对象的<code>xxxValue()</code>方法，将包装对象转换为对应的基本数据类型值。</p>
+<p>自动装箱和拆箱虽然方便，但是在使用的时候也需要注意一些问题：</p>
+<ul>
+<li>比较：包装对象的数值比较，不能简单的使用<code>==</code>，虽然 -128 到 127 之间的数字可以，但是这个范围之外还是需要使用 <code>equals</code>方法进行比较；</li>
+<li>NPE：因为有自动拆箱的机制，如果初始的包装类型对象为<code>null</code>，那么在自动拆箱的时候的就会报<code>NullPointerException</code>，在使用时需要格外注意；</li>
+<li>性能：频繁的装箱和拆箱操作可能会影响性能，因为涉及到对象的创建和销毁。如果一个for循环中有大量拆装箱操作，会浪费很多资源；</li>
+</ul>
+<h4 id="缓存池">缓存池</h4>
+<p>在Java中，对于某些包装类型的对象，存在一个缓存池，这是一种优化机制，可以减少频繁创建对象的开销，提升性能。</p>
+<p>基本类型对应的缓冲池如下：</p>
+<ul>
+<li><code>Boolean</code>类型的<code>true</code>和<code>false</code>值在静态初始化块中被缓存起来了；</li>
+<li><code>Byte</code>类型在 -128 到 127 之间的值会被缓存；</li>
+<li><code>Character</code>类型在 &lsquo;\u0000&rsquo; 到 &lsquo;\u007F&rsquo; 之间的值会被缓存；</li>
+<li><code>Short</code>、<code>Integer</code>和<code>Long</code>类型在范围 -128 到 127 之间的值会被缓存；</li>
+</ul>
+<p>在使用这些基本类型对应的包装类型时，如果该数值范围在缓冲池范围内，就可以直接使用缓冲池中的对象。两种浮点数类型的包装类<code>Float</code>，<code>Double</code>并没有实现常量池技术。</p>
+<p>在JDK 1.8所有的数值类缓冲池中，<code>Integer</code>的缓冲池<code>IntegerCache</code>很特殊，这个缓冲池的下界是-128，上界默认是127，但是这个上界是可调的，在启动JVM的时候，通过<code>-XX:AutoBoxCacheMax=&lt;size&gt;</code>来指定这个缓冲池的大小，该选项在 JVM 初始化的时候会设定一个名为<code>java.lang.IntegerCache.high</code>系统属性，然后 <code>IntegerCache</code>初始化的时候就会读取该系统属性来决定上界。</p>
+<p>使用<code>Integer.valueOf()</code>方法来创建<code>Integer</code>对象时，会优先从缓冲池中获取对象，如果缓冲池中不存在该值的对象，则会创建一个新的对象。
+<code>new Integer(123)</code>，这种方式会显式地创建一个新的<code>Integer</code>对象，每次调用<code>new Integer(123)</code>都会创建一个新的对象实例。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Integer</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">123</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Integer</span><span class="w"> </span><span class="n">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">123</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">y</span><span class="p">);</span><span class="w">    </span><span class="c1">// false 因为是两个不同的对象实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Integer</span><span class="w"> </span><span class="n">z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">123</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Integer</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">123</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">z</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">k</span><span class="p">);</span><span class="w">   </span><span class="c1">// true 因为返回的是同一个缓存池中的对象实例</span><span class="w">
+</span></span></span></code></pre></div><p><code>Integer.valueOf()</code>方法的实现比较简单，就是先判断值是否在缓存池中，如果在的话就直接返回缓存池的内容。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public static Integer valueOf(int i) {
+</span></span><span class="line"><span class="cl">    if (i &gt;= IntegerCache.low &amp;&amp; i &lt;= IntegerCache.high)
+</span></span><span class="line"><span class="cl">        return IntegerCache.cache[i + (-IntegerCache.low)];
+</span></span><span class="line"><span class="cl">    return new Integer(i);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在 Java 8 中，<code>Integer</code>缓存池的大小默认为 -128~127，在源码中也能看到具体的实现。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">low</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">128</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">high</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">cache</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// high value may be configured by property</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">127</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">integerCacheHighPropValue</span><span class="w"> </span><span class="o">=</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sun</span><span class="p">.</span><span class="na">misc</span><span class="p">.</span><span class="na">VM</span><span class="p">.</span><span class="na">getSavedProperty</span><span class="p">(</span><span class="s">&#34;java.lang.Integer.IntegerCache.high&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">integerCacheHighPropValue</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">parseInt</span><span class="p">(</span><span class="n">integerCacheHighPropValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">127</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// Maximum array size is Integer.MAX_VALUE</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="p">(</span><span class="o">-</span><span class="n">low</span><span class="p">)</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="p">(</span><span class="w"> </span><span class="n">NumberFormatException</span><span class="w"> </span><span class="n">nfe</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// If the property cannot be parsed into an int, ignore it.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">high</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">h</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">cache</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="o">[</span><span class="p">(</span><span class="n">high</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">low</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">low</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">cache</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">k</span><span class="o">++</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cache</span><span class="o">[</span><span class="n">k</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">j</span><span class="o">++</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// range [-128, 127] must be interned (JLS7 5.1.7)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">assert</span><span class="w"> </span><span class="n">IntegerCache</span><span class="p">.</span><span class="na">high</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">127</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>而编译器会在自动装箱过程会调用 <code>valueOf()</code>方法，因此多个值相同且值在缓存池范围内的<code>Integer</code>实例使用自动装箱来创建，那么就会引用相同的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Integer m = 123;
+</span></span><span class="line"><span class="cl">Integer n = 123;
+</span></span><span class="line"><span class="cl">System.out.println(m == n); // true
+</span></span></code></pre></div><p>所以<code>Integer</code>、<code>int </code>在 <code>-127~128</code>之间是不会创建新的对象的，即</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">12</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">12</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="o">==</span><span class="n">b</span><span class="p">);</span><span class="c1">//true</span><span class="w">
+</span></span></span></code></pre></div><h2 id="引用类型">引用类型</h2>
+<p>在Java中，引用类型是指除了基本数据类型之外的所有类型，它们都是通过指向一个对象(类似于C的指针)来访问和操作的，所以叫做引用类型。所有引用类型的默认值都是<code>null</code>。</p>
+<p>引用类型主要包括：</p>
+<ul>
+<li>类
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>数组类型
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>接口类型
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">interface</span> <span class="nc">MyInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>注解类型
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@interface</span><span class="w"> </span><span class="n">MyAnnotation</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 注解</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>枚举类型
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">enum</span><span class="w"> </span><span class="n">Day</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 枚举</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>与基本类型的区别：</p>
+<ol>
+<li>内存分配：基本数据类型在被创建时，在栈中直接划分一块内存，将数值直接存入栈中；引用数据类型在被创建时，先在堆中开辟内存创建存放值，然后引用到栈中的是在堆中的地址值；</li>
+<li>传递参数：基本数据类型是值传递，引用数据类型是引用传递；</li>
+<li>继承和多态：引用类型支持继承和多态特性，可以通过父类引用指向子类对象，实现代码的灵活性和扩展性；</li>
+<li>比较：引用类型的变量比较的是对象的引用，而不是对象的内容。使用 == 运算符比较引用类型变量时，比较的是它们在内存中的地址是否相同；</li>
+<li><code>null</code>值：引用类型的变量可以赋予<code>null</code>值，表示它不引用任何对象。使用未初始化的引用类型变量或将其设置为<code>null</code>可以避免空指针异常；</li>
+</ol>
+<p>需要注意的是<code>String</code>类是引用类型，不是基本类型。
+默认情况下，Java中的浮点数类型是<code>double</code>类型，如果你希望定义一个<code>float</code>类型的浮点数，需要在数值后面加上 F 或 f 后缀，例如<code>float f = 1.23f</code>。
+Java 中的浮点数类型 (<code>float</code>和<code>double</code>)是用来表示近似值的，而不是精确的数值。
+因此，在涉及到精确计算的场景中，尤其是涉及货币等需要精确表示的值时，应当使用<code>BigDecimal</code>类型来避免精度问题。</p>
+<h3 id="引用类型转换">引用类型转换</h3>
+<p>在Java中，引用类型的类型转换主要涉及向上转型和向下转型两种操作，引用类型的转换是基于继承关系和多态性，只有在存在父子类关系或者接口实现关系时才能进行。</p>
+<p>向上转型是指将一个子类的对象引用转换为其父类类型或者更高层次的类型。
+向上转型是安全的，这种转型是隐式的，编译器会自动进行处理，子类对象可以直接赋值给父类类型的引用变量。
+这种转型通常发生在子类对象需要作为父类对象使用的场景中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Dog</span><span class="w"> </span><span class="n">myDog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w"> </span><span class="c1">// 创建Dog对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">myAnimal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myDog</span><span class="p">;</span><span class="w"> </span><span class="c1">// 向上转型为Animal类型，隐式转型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>向下转型是指将一个父类类型或者更高层次的类型的对象引用转换为其子类类型。
+向下转型是需要显式指定的，并且需要进行类型检查（<code>instanceof</code>）以及类型转换（<code>cast</code>）操作。如果实际对象不是目标类型，会抛出<code>ClassCastException</code>异常。
+如果引用变量是<code>null</code>，无法进行任何类型转换操作。在转换之前，需要确保引用变量不为<code>null</code>，否则会导致<code>NPE</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">myAnimal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w"> </span><span class="c1">// 向上转型为Animal类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">myAnimal</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Dog</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Dog</span><span class="w"> </span><span class="n">myDog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Dog</span><span class="p">)</span><span class="w"> </span><span class="n">myAnimal</span><span class="p">;</span><span class="w"> </span><span class="c1">// 安全的向下转型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="对象的比较">对象的比较</h3>
+<p>在Java中，引用类型的比较涉及到比较对象的引用值，而不是对象的内容。这是因为在Java中，每个对象变量存储的是对象的引用地址，而不是对象本身。
+使用<code>==</code>操作符比较两个对象引用时，比较的是它们在内存中的地址是否相同，即是否引用同一个对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str2</span><span class="p">);</span><span class="w"> </span><span class="c1">// false，str1和str2引用不同的对象实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str3</span><span class="p">);</span><span class="w"> </span><span class="c1">// true，str1和str3引用同一个对象实例</span><span class="w">
+</span></span></span></code></pre></div><p>在比较两个对象是否相等时，使用最多的是<code>equals()</code>方法，它通常在类中被重写以实现特定的比较逻辑。
+默认情况下，<code>equals()</code>方法和<code>==</code>操作符行为一样，比较的是对象的引用，但是如果类中重写了<code>equals()</code>方法，那就不一定了。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str1</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">str2</span><span class="p">));</span><span class="w"> </span><span class="c1">// true，比较的是对象的内容</span><span class="w">
+</span></span></span></code></pre></div><p>上面的例子中，<code>str1.equals(str2)</code>返回<code>true</code>，因为<code>String</code>类重写了<code>equals()</code>方法，用来比较字符串的内容而不是引用值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// String类中的equals()方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">anObject</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">anObject</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">anObject</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">anotherString</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="p">)</span><span class="n">anObject</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">anotherString</span><span class="p">.</span><span class="na">value</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">char</span><span class="w"> </span><span class="n">v1</span><span class="o">[]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">char</span><span class="w"> </span><span class="n">v2</span><span class="o">[]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">anotherString</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="o">--</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">v1</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">v2</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">i</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="常量">常量</h2>
+<p>在Java中，常量指的是一种不可改变的量或者数值，其值在程序执行过程中不会发生变化。常量在Java中有两种主要的形式：</p>
+<ul>
+<li>字面常量：在计算机科学中，字面量是用于表达源代码中一个固定值的表示法。几乎所有计算机编程语言都具有对基本值的字面量表示，诸如：整数、浮点数以及字符串；而有很多也对布尔类型和字符类型的值也支持字面量表示，还有一些甚至对枚举类型的元素以及像数组、记录和对象等复合类型的值也支持字面量表示法；</li>
+<li><code>final</code>修饰的变量：Java常量简单理解为<code>final</code>修饰的变量。Java常量就是在程序运行过程中一直不会改变的量的量，<code>final</code>修饰的变量必须在声明时初始化，一旦初始化后，其值就不能再被修改；</li>
+</ul>
+<p>常量和数据类型之间有密切的关系，常量可以是任何数据类型的值，包括基本数据类型和引用类型，如对象或数组。
+常量的数据类型必须与其值的数据类型匹配，例如<code>final int MAX_SIZE = 100</code>中的常量<code>MAX_SIZE</code>是整数类型。</p>
+<p>为防止混淆和更好理解，将常量，变量和字面量用代码举例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">int a = 10; // a为变量，10为字面量
+</span></span><span class="line"><span class="cl">final int b = 10;  // b为常量，10为字面量
+</span></span><span class="line"><span class="cl">static c = &#34;Hello World&#34;;  // c为变量，HelloWorld为字面量
+</span></span></code></pre></div><ul>
+<li>常量：程序运行中，固定不变的量；</li>
+<li>变量：值可以修改的数据类型；</li>
+<li>字面量：字面量就是数据，是由字母、数字等构成的字符串或者数值，如30（整型）、3.15（浮点型）、“我是字符串”（字符串型）、‘中’（字符型）、true（布尔型）、false（布尔型）等，只能作为右值出现，如<code>int a = 10</code>，这里的a是左值，10为右值；</li>
+</ul>
+<h3 id="定义常量">定义常量</h3>
+<p>在 Java 中使用<code>final</code>关键字来修饰常量，声明方式和变量类似。
+要声明一个常量，第一需要制定数据类型，第二需要通过<code>final</code>关键字进行限定格式：<code>final 数据类型 常量名称[=值]</code>。</p>
+<p><code>final</code>关键字表示最终的，它可以修改很多元素：</p>
+<ul>
+<li>当<code>final</code>修饰变量就变成了常量；</li>
+<li>当<code>final</code>用于修饰方法时，表示该方法不能被子类重写；</li>
+<li>当<code>final</code>用于修饰类时，表示该类不能被继承；</li>
+</ul>
+<p>常量因为被<code>final</code>修饰一旦初始化后，其值就不能再被修改，所以在定义常量时就需要对该常量进行初始化。
+为了与变量区别，提高代码的可读性和可维护性，常量取名一般都用大写字符，单词之间使用下划线 <code>_</code>分隔，如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">final double PI = 3.1415927;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">public static final int MAX_VALUE = 100;
+</span></span></code></pre></div><p>常量可以根据它们的作用范围和声明位置将其归类。常量的类型包括静态常量、成员常量和局部常量。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class HelloWorld {
+</span></span><span class="line"><span class="cl">    // 静态常量
+</span></span><span class="line"><span class="cl">    public static final double PI = 3.14;
+</span></span><span class="line"><span class="cl">    // 声明成员常量
+</span></span><span class="line"><span class="cl">    final int y = 10;
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        // 声明局部常量
+</span></span><span class="line"><span class="cl">        final double x = 3.3;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="常量池">常量池</h3>
+<p>常量池是Java为了提高性能和减少内存开销而引入的一种机制，常量则是程序中不可改变的值，在程序中定义的不可变值，存储在栈、堆或常量池中。</p>
+<p>常量池、可以看做是一张表，虚拟机指令根据这张常量表找到要执行的类名、方法名、参数类型、字面量等类型。
+在Java中，大致上可以分为三种常量池，分别是字符串常量池、Class常量池(静态常量池)和运行时常量池。
+我们常说的常量池，指的是方法区中的运行时常量池。</p>
+<h4 id="class常量池">Class常量池</h4>
+<p>在Java中，每个编译后的<code>.class</code>文件中包含一个常量池，用于存储与类相关的各种常量，这个常量池被称为Class常量池，这些常量包括字面量和符号引用。</p>
+<p><code>class</code>文件，主要在平台无关性和网络移动性方面使Java更适合网络。
+它在平台无关性方面的任务，是为Java程序提供独立于底层主机平台的二进制形式的服务。
+二进制形式的服务会产生字节码，有了字节码，无论是哪种平台（如Windows、Linux等），只要安装了虚拟机，都可以直接运行字节码。
+目前Java虚拟机已经可以支持很多除Java语言以外的语言了，如Groovy、JRuby、Jython、Scala等。之所以可以支持，就是因为这些语言也可以被编译成字节码。
+而虚拟机并不关心字节码是有哪种语言编译而来的。</p>
+<p>来看一下字节码文件，将下面代码通过<code>javac</code>命令编译：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HelloWorld</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>生成<code>.class</code>文件.<code>vi</code>命令查看：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Êþº¾^@^@^@4^@^Q
+</span></span><span class="line"><span class="cl">^@^D^@^M^H^@^N^G^@^O^G^@^P^A^@^F&lt;init&gt;^A^@^C()V^A^@^DCode^A^@^OLineNumberTable^A^@^Dmain^A^@^V([Ljava/lang/String;)V^A^@
+</span></span><span class="line"><span class="cl">SourceFile^A^@^OHelloWorld.java^L^@^E^@^F^A^@^C123^A^@7com/example/springboot/example/security/util/HelloWorld^A^@^Pjava/lang/Object^@!^@^C^@^D^@^@^@^@^@^B^@^A^@^E^@^F^@^A^@^G^@^@^@^]^@^A^@^A^@^@^@^E*·^@^A±^@^@^@^A^@^H^@^@^@^F^@^A^@^@^@^C^@        ^@      ^@
+</span></span><span class="line"><span class="cl">^@^A^@^G^@^@^@ ^@^A^@^B^@^@^@^D^R^BL±^@^@^@^A^@^H^@^@^@
+</span></span><span class="line"><span class="cl">^@^B^@^@^@^E^@^C^@^F^@^A^@^K^@^@^@^B^@^L
+</span></span></code></pre></div><p>使用16进制打开<code>class</code>文件，即使用<code>vim xxx.class</code> ，然后在交互模式下，输入<code>%!xxd</code> ，即可得到：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">00000000: cafe babe 0000 0034 0011 0a00 0400 0d08  .......4........
+</span></span><span class="line"><span class="cl">00000010: 000e 0700 0f07 0010 0100 063c 696e 6974  ...........&lt;init
+</span></span><span class="line"><span class="cl">00000020: 3e01 0003 2829 5601 0004 436f 6465 0100  &gt;...()V...Code..
+</span></span><span class="line"><span class="cl">00000030: 0f4c 696e 654e 756d 6265 7254 6162 6c65  .LineNumberTable
+</span></span><span class="line"><span class="cl">00000040: 0100 046d 6169 6e01 0016 285b 4c6a 6176  ...main...([Ljav
+</span></span><span class="line"><span class="cl">00000050: 612f 6c61 6e67 2f53 7472 696e 673b 2956  a/lang/String;)V
+</span></span><span class="line"><span class="cl">00000060: 0100 0a53 6f75 7263 6546 696c 6501 000f  ...SourceFile...
+</span></span><span class="line"><span class="cl">00000070: 4865 6c6c 6f57 6f72 6c64 2e6a 6176 610c  HelloWorld.java.
+</span></span><span class="line"><span class="cl">00000080: 0005 0006 0100 0331 3233 0100 3763 6f6d  .......123..7com
+</span></span><span class="line"><span class="cl">00000090: 2f65 7861 6d70 6c65 2f73 7072 696e 6762  /example/springb
+</span></span><span class="line"><span class="cl">000000a0: 6f6f 742f 6578 616d 706c 652f 7365 6375  oot/example/secu
+</span></span><span class="line"><span class="cl">000000b0: 7269 7479 2f75 7469 6c2f 4865 6c6c 6f57  rity/util/HelloW
+</span></span><span class="line"><span class="cl">000000c0: 6f72 6c64 0100 106a 6176 612f 6c61 6e67  orld...java/lang
+</span></span></code></pre></div><p><code>HelloWorld.class</code>文件中的前八个字母是<code>cafe babe</code>，这就是<code>class</code>文件的魔数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">cafe babe   0000      0034        0011      0a00 0400 0d08
+</span></span><span class="line"><span class="cl">   魔数    此版本号   主版本号    常量池计数器      常量池计数区
+</span></span></code></pre></div><p>我们需要知道的是，每个<code>class</code>文件的前四个字节表示魔数，他的唯一作用是确定这个文件是否是一个能被虚拟机接受的<code>class</code>文件，紧接着魔数的4个字节后，第5个和第6个表示次版本号，第7、8表示主版本号。
+我生成的<code>class</code>文件的版本号是16进制<code>0034</code>，转化为10进制是52，这是Java8对应的版本。也就是说，这个版本的字节码，在JDK 1.8以下的版本中无法运行，在版本号后面的，就是Class常量池入口了。</p>
+<p>Class常量池中主要存放两大类常量，字面量和符号引用。</p>
+<ul>
+<li>符号引用：符号引用是编译原理中的概念，是相对于直接引用来说的，主要包括了以下三类常量：类和接口的全限定名、字段的名称和描述符、方法的名称和描述符。
+符号引用以一组符号来描述所引用的目标。符号引用可以是任何形式的字面量，只要使用时能无歧义地定位到目标即可，符号引用和虚拟机的布局无关；</li>
+<li>字面量：字面量是指在Java源代码中明确给出的常量值。由字母、数字等构成的字符串或者数值，如30（整型）、3.15（浮点型）、“我是字符串”（字符串型）、‘中’（字符型）、true（布尔型）、false（布尔型）等，只能作为右值出现，如<code>int a = 10</code>，这里的a是左值，10为右值；</li>
+</ul>
+<p>在编译的时候每个java类都会被编译成一个<code>class</code>文件，但在编译的时候虚拟机并不知道所引用类的地址，所以就用符号引用来代替，
+而在<strong>解析阶段</strong>就是为了把符号引用转化成为真正的地址的过程。</p>
+<blockquote>
+<p>解析阶段:
+Java类从加载到虚拟机内存中开始，到卸载出内存为止，它的整个生命周期包括：加载、 验证、 准备、 解析、 初始化、 卸载，总共七个阶段。其中验证、准备、解析统称为连接。
+而在解析阶段会有一步将常量池当中二进制数据（符号引用）转化为直接引用的过程。</p>
+</blockquote>
+<p>在Java编译阶段，由<code>.java</code>文件会生成<code>.class</code>文件。
+<code>class</code>文件中除了包含类的版本、字段、方法、接口等描述信息外，还有一项信息就是常量池，用于存放编译器生成的各种字面量和符号引用。
+由于不同的<code>class</code>文件中包含的常量的个数是不固定的，所以在<code>class</code>文件的常量池入口处设置两个字节的常量池容量计数器，记录了常量池中常量的个数。</p>
+<p>Class常量池可以理解为是Class文件中的资源仓库。
+Class常量池中保存了各种常量，而这些常量都是开发者定义出来，需要在程序的运行期使用的。
+Java代码在进行<code>javac</code>编译的时候，在<code>class</code>文件中不会保存各个方法、字段的最终内存布局信息，因此这些字段、方法的符号引用不经过运行期转换的话无法得到真正的内存入口地址，也就无法直接被虚拟机使用。
+当虚拟机运行时，需要从常量池获得对应的符号引用，再在类创建时或运行时解析、翻译到具体的内存地址之中。
+Class常量池是用来保存常量的一个媒介场所，并且是一个中间场所。在JVM真的运行时，需要把常量池中的常量加载到内存中。</p>
+<h4 id="运行时常量池">运行时常量池</h4>
+<p>运行时常量池是每一个类或接口的常量池的运行时表示形式。
+每一个运行时常量池都分配在Java虚拟机的方法区之中，在类和接口被加载到虚拟机后，对应的运行时常量池就被创建出来。
+当创建类或接口的运行时常量池时，如果构造运行时常量池所需的内存空间，超过了方法区所能提供的最大值，则JVM会抛<code>OutOfMemoryError</code>异常。</p>
+<p>简单说来就是JVM在完成类装载操作后，将<code>class</code>文件中的常量池载入到内存中，并保存在方法区中，我们常说的常量池，就是指方法区中的运行时常量池。
+根据JVM规范，JVM内存共分为虚拟机栈、堆、方法区、程序计数器、本地方法栈五个部分，运行时常量池存放在JVM内存模型中的方法区中。
+在不同版本的JDK中，运行时常量池所处的位置也不一样。以<code>HotSpot</code>为例，JDK1.7之前方法区位于永久代，由于一些原因在JDK1.8时彻底祛除了永久代，用元空间代替。</p>
+<p>运行时常量池内容包含了Class常量池中的常量和字符串常量池中的内容。
+它包含多种不同的常量，也包括编译期就已经明确的数值字面量、到运行期解析后才能够获得的方法或者字段引用。
+它扮演了类似传统语言中符号表的角色，不过它存储数据范围比通常意义上的符号表要更为广泛。</p>
+<p>保存在JVM方法区中的叫运行时常量池，在 class/字节码 文件中的叫Class常量池（静态常量池）。
+与类文件中的Class常量池不同的是，运行时常量池是在类加载到内存后动态生成的，相对于Class文件常量池的另一重要特征是具备动态性。
+运行时常量池的动态性体现在它不仅仅是简单地静态存储常量值，而是支持了Java程序在运行时动态加载类、操作字符串、实现动态代理和利用反射等高级特性。
+例如，反射机制可以通过运行时常量池中的符号引用动态加载类、获取和调用方法等。</p>
+<h4 id="为什么需要常量池">为什么需要常量池</h4>
+<p>一个Java源文件中的类、接口，编译后产生一个字节码文件。
+而Java中的字节码需要数据支持，通常这种数据会很大以至于不能直接存到字节码里，换另一种方式，可以存到常量池，这个字节码包含了指向常量池的引用，在动态链接的时候会用到运行时常量池。</p>
+<p>比如：如下的代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SimpleClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sayHello</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>虽然上述代码生成的class文件只有194字节，但是里面却使用了<code>String</code>、<code>System</code>、<code>PrintStream</code>及<code>Object</code>等结构。
+这里的代码量其实很少了，如果代码多的话，引用的结构将会更多，这样就体现出常量池的作用了。</p>
+<p>常量池是为了避免频繁的创建和销毁对象而影响系统性能，其实现了对象的共享，避免了相同内容的字符串的创建，节省了内存，省去了创建相同字符串的时间，同时提升了性能。</p>
+<h2 id="string类型">String类型</h2>
+<p>在Java编程中，字符串类型是一个极其基础和重要的类，字符串属于对象，并且由专门的<code>String</code>类来创建和管理，它被广泛用于表示和操作文本数据。</p>
+<p>由于 <code>String</code>被声明为 final，它是不可变的，即一旦创建，其值无法更改。这种设计不仅确保了字符串的安全性和稳定性，还优化了内存使用。
+<code>String</code>类还实现了<code>Serializable</code>接口，这意味着字符串可以被序列化，以便在不同的Java虚拟机之间传输。
+此外，<code>String</code>实现了<code>Comparable</code>接口，使得字符串对象可以进行自然排序。</p>
+<h3 id="为什么jdk9改变了存储结构">为什么JDK9改变了存储结构</h3>
+<p>在Java8中，<code>String</code>内部使用<code>char</code>数组存储数据。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">String</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">implements</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">Serializable</span><span class="p">,</span><span class="w"> </span><span class="n">Comparable</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">CharSequence</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The value is used for character storage. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">value</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在Java9之后，<code>String</code>类的实现改用<code>byte</code>数组存储字符串，同时使用 <code>oder</code>来标识使用了哪种编码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">String</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">implements</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">Serializable</span><span class="p">,</span><span class="w"> </span><span class="n">Comparable</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">CharSequence</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The value is used for character storage. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The identifier of the encoding used to encode the bytes in {@code value}. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">byte</span><span class="w"> </span><span class="n">coder</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><a href="http://openjdk.java.net/jeps/254">那么为什么要改变存储结构呢？</a>
+官方的解释：</p>
+<blockquote>
+<p>The current implementation of the String class stores characters in a char array, using two bytes (sixteen bits) for each character.
+Data gathered from many different applications indicates that strings are a major component of heap usage and,
+moreover, that most String objects contain only Latin-1 characters. Such characters require only one byte of storage,
+hence half of the space in the internal char arrays of such String objects is going unused.<br>
+We propose to change the internal representation of the String class from a UTF-16 char array to a byte array plus an encoding-flag field.
+The new String class will store characters encoded either as ISO-8859-1/Latin-1 (one byte per character),
+or as UTF-16 (two bytes per character), based upon the contents of the string.
+The encoding flag will indicate which encoding is used.</p>
+</blockquote>
+<p>文档大意：<code>String</code>类的当前实现将字符存储在<code>char</code>数组中，每个字符使用两个字节(16位)。
+从许多不同的应用程序收集的数据表明，字符串是堆使用的主要组成部分，而且大多数字符串对象只包含拉丁字符。
+这些字符只需要一个字节的存储空间，因此这些字符串对象的内部<code>char</code>数组中有一半的空间将不会使用。</p>
+<p>我们建议将<code>String</code>类的内部表示从<code>UTF-16</code>字符数组更改为一个字节数组加上一个编码标志字段。
+新的<code>String</code>类将根据字符串的内容存储编码为<code>ISO-8859-1/Latin-1</code>(每个字符一个字节)或<code>UTF-16</code>(每个字符两个字节)的字符。
+编码标志将指示所使用的编码。</p>
+<p>简单说来就是用<code>char</code>数组存，有些数据占不了两个字节，所以为了节约资源改成<code>byte</code>数组存放。
+如果存放的不是拉丁文则需要占两个字节，所以还需要加上编码标记。
+基于<code>String</code>的数据结构，<code>StringBuffer</code>和<code>StringBuilder</code>也同样做了修改。</p>
+<h3 id="不可变性">不可变性</h3>
+<p><code>String</code>类型具有不可变性，因为底层存储的value数组被声明为<code>final</code>，这意味着value数组初始化之后就不能再引用其它数组。
+<code>String</code>是Java中一个不可变的类，所以一旦一个string对象在内存中被创建出来，他就无法被修改。</p>
+<p>下面代码说明String是不可变的：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;good&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">char</span><span class="w"> </span><span class="o">[]</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="sc">&#39;t&#39;</span><span class="p">,</span><span class="sc">&#39;e&#39;</span><span class="p">,</span><span class="sc">&#39;s&#39;</span><span class="p">,</span><span class="sc">&#39;t&#39;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">change</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;test ok&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="w"> </span><span class="s">&#34;chanage方法里str=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">str</span><span class="p">);</span><span class="w"> </span><span class="c1">// chanage方法里str=test ok</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ch</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">&#39;b&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MainTest</span><span class="w"> </span><span class="n">ex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MainTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ex</span><span class="p">.</span><span class="na">change</span><span class="p">(</span><span class="n">ex</span><span class="p">.</span><span class="na">str</span><span class="p">,</span><span class="w"> </span><span class="n">ex</span><span class="p">.</span><span class="na">ch</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">ex</span><span class="p">.</span><span class="na">str</span><span class="p">);</span><span class="w"> </span><span class="c1">// good</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">ex</span><span class="p">.</span><span class="na">ch</span><span class="p">);</span><span class="c1">// best</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>String</code>类的所有方法都没有改变字符串本身的值，都是返回了一个新的对象，那么为什么要把<code>String</code>类设计成不可变的呢？</p>
+<ol>
+<li>字符串不可变的根本原因我认为应是出于对数据的安全性考虑。<code>String</code>经常作为参数，<code>String</code>不可变性可以保证参数不可变。
+实际项目中会用到，比如数据库连接串、账号、密码等字符串，只有不可变的连接串、用户名和密码才能保证安全性。</li>
+<li>线程安全。字符串在Java中的使用频率可谓高之又高，那在高并发的情况下不可变性也使得对字符串的读写操作不用考虑多线程竞争的情况。
+不可变的字符串在多线程环境中是安全的。由于<code>String</code>对象一旦创建就不能被修改，因此多个线程可以安全地共享相同的<code>String</code>实例，而不需要担心数据被修改。</li>
+<li><code>String</code>常量池的需要。字符串常量池的基础就是字符串的不可变性，如果字符串是可变的，那想一想，常量池就没必要存在了。
+如果一个<code>String</code> 对象已经被创建过了，那么就会从<code>String</code>常量池中取得引用。只有<code>String</code>是不可变的，才可能使用 字符串常量池。</li>
+<li>可以缓存<code>hash</code>值。因为<code>String</code>的<code>hash</code>值经常被使用，像<code>Set</code>、<code>Map</code>结构中的<code>key</code>值也需要用到<code>HashCode</code>来保证唯一性和一致性，因此不可变的<code>HashCode</code>才是安全可靠的。</li>
+</ol>
+<h3 id="new-stringabc会创建几个对象">new String(&ldquo;abc&rdquo;)会创建几个对象</h3>
+<p><code>new String(&quot;abc&quot;)</code>会创建几个对象？ 这是面试中经常问的一个问题，先说答案两个字符串对象，前提是<code>String</code>常量池中还没有 &ldquo;abc&rdquo; 字符串对象。
+第一个对象是&quot;abc&quot;，它属于字符串字面量，因此编译时期会在字符串常量池中创建一个字符串对象，指向这个 &ldquo;abc&rdquo; 字符串字面量，而使用<code>new</code>的方式会在堆中创建一个字符串对象。</p>
+<p>来证明一下，到底是不是创建了两个对象，先看一下JDK8 中<code>new String()</code>源代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Initializes a newly created {@code String} object so that it represents
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * the same sequence of characters as the argument; in other words, the
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * newly created string is a copy of the argument string. Unless an
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * explicit copy of {@code original} is needed, use of this constructor is
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * unnecessary since Strings are immutable.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">String</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">original</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">this</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">hash</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>文档注释大意：初始化新创建的<code>String</code>对象，使其表示与实参相同的字符序列，换句话说，新创建的字符串是实参字符串的副本。
+除非需要显式复制形参的值，否则没有必要使用这个构造函数，因为字符串是不可变的。</p>
+<p>用字节码看一下，创建一个测试类，其<code>main</code>方法中使用这种方式来创建字符串对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;abc&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>使用<code>javap -verbose</code>命令进行反编译，得到以下内容：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">Constant pool:
+</span></span><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">   #2 = Class              #18            // java/lang/String
+</span></span><span class="line"><span class="cl">   #3 = String             #19            // abc
+</span></span><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">  #18 = Utf8               java/lang/String
+</span></span><span class="line"><span class="cl">  #19 = Utf8               abc
+</span></span><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">  public static void main(java.lang.String[]);
+</span></span><span class="line"><span class="cl">    descriptor: ([Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">    flags: ACC_PUBLIC, ACC_STATIC
+</span></span><span class="line"><span class="cl">    Code:
+</span></span><span class="line"><span class="cl">      stack=3, locals=2, args_size=1
+</span></span><span class="line"><span class="cl">         0: new           #2                  // class java/lang/String
+</span></span><span class="line"><span class="cl">         3: dup
+</span></span><span class="line"><span class="cl">         4: ldc           #3                  // String abc
+</span></span><span class="line"><span class="cl">         6: invokespecial #4                  // Method java/lang/String.&#34;&lt;init&gt;&#34;:(Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">         9: astore_1
+</span></span><span class="line"><span class="cl">// ...
+</span></span></code></pre></div><p>在<code>Constant Pool</code>中，<code>#19</code>存储这字符串字面量<code>&quot;abc&quot;</code>，<code>#3</code>是<code>String Pool</code>的字符串对象，它指向<code>#19</code>这个字符串字面量。
+在<code>main</code>方法中，<code>0:</code>行使用<code>new #2</code>在堆中创建一个字符串对象，并且使用<code>ldc #3</code>将<code>String Pool</code>中的字符串对象作为<code>String</code>构造函数的参数。
+所以能看到使用<code>new String()</code>的方式创建字符串是创建两个对象。</p>
+<p>那么使用<code>new String(&quot;a&quot;) + new String(&quot;b&quot;)</code>会创建几个对象？会创建6个对象：</p>
+<ul>
+<li>对象1：因为存在用&quot;+&ldquo;连接，所以从字节码角度分析会产生<code>new StringBuilder()</code>对象；</li>
+<li>对象2：<code>new String(&quot;a&quot;)</code>会从堆空间创建一个对象；</li>
+<li>对象3：常量池的a；</li>
+<li>对象4：<code>new String(&quot;b&quot;)</code>会从堆空间创建一个对象；</li>
+<li>对象5：常量池的b；</li>
+<li>对象6：从字节码角度分析，通过<code>new StringBuilder().append()</code>添加完字符串后，会通过<code>StringBuilder.toString()</code>中会创建一个 <code>new String(&quot;ab&quot;)</code>，但是调用<code>toString()</code>方法，不会在常量池中生成ab字符串；</li>
+</ul>
+<h3 id="字符串常量池">字符串常量池</h3>
+<p>在JVM中，为了减少相同的字符串的重复创建，为了达到节省内存的目的，会单独开辟一块内存，用于保存字符串常量，这个内存区域被叫做字符串常量池。
+字符串常量池保存着所有字符串字面量，这些字面量在编译时期就被确定。</p>
+<p>字符串常量池不同版本JDK中位置是不一样的，Java6及以前，字符串常量池存放在永久代，Java7将字符串常量池的位置调整到Java堆内。
+那么字符串常量池为什么要调整位置？</p>
+<p>是为了优化内存管理和避免特定情况下的内存溢出问题。
+在早期的Java版本（如JDK 6及之前），字符串常量池通常是存放在永久代，GC对永久代的回收效率很低，只有在<code>Full GC</code>的时候才会触发，这就导致字符串常量池回收效率不高。
+而我们开发过程中，使用频率比较高，会有大量的字符串被创建，如果无法及时回收，容易导致永久代内存不足。所以JDK7之后将字符串常量池放到堆里，能及时回收内存，避免出现<code>OOM</code>错误。</p>
+<p>如何证明Java8中的字符串常量池方到了堆中？代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 虚拟机参数： -Xmx6m -Xms6m -XX:MetaspaceSize=10m -XX:MaxMetaspaceSize=10m</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">short</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">hashSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="o">++</span><span class="p">).</span><span class="na">intern</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>抛出异常证明Java8中的字符串常量池方到了堆中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Exception in thread &#34;main&#34; java.lang.OutOfMemoryError: Java heap space
+</span></span></code></pre></div><p>关于JDK1.6、JDK1.7字符串常量池，有一道相关的面试题。下列代码在JDK1.6、JDK1.7中执行结果不同：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w"> </span><span class="c1">// ==&gt; new String(&#34;11&#34;); 并不会在字符串常量池创建 &#34;11&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 在JDK7及之后，JVM为了节省空间进行优化，在字符串常量池中的对象只保存了堆中对象的地址，而并不是创建了一个真正的对象；</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// &#34;11&#34;不在字符串常量池中 ，把&#34;11&#34;放入字符串常量池中 因为堆中已经存在对象，JDK6在字符串池中保存的是一个真正的对象 JDK7保存的是一个引用地址</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s3</span><span class="p">.</span><span class="na">intern</span><span class="p">();</span><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取字符串常量池的引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;11&#34;</span><span class="p">;</span><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s3</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s4</span><span class="p">);</span><span class="w"> </span><span class="c1">// JDK1.6: false   JDK1.7: true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在JDK1.7及之后，<code>new String(&quot;1&quot;)</code>会在堆中创建一个对象并且会在字符串常量池中创建一个对象。
+因为在堆中已经创建了对象，JVM为了节省空间，在字符串常量池中的对象只保留了引用堆中对象的地址，而并不是创建了一个真正的对象，所以就会出现<code>true</code>的情况。
+JDK1.6创建对象被放在了永久区中的字符串常量池，而并非堆中，JVM无法对其进行优化，所以是<code>false</code>。</p>
+<p>JDK1.6中，将这个字符串对象尝试放入字符串常量池：</p>
+<ul>
+<li>如果串池中有，则并不会放入，并返回已有的串池中的对象的地址；</li>
+<li>如果没有，会把此<strong>对象复制一份，放入串池</strong>，并返回串池中的对象地址；</li>
+</ul>
+<p><img alt="JDK6字符串常量池案例解析" src="/iblog/posts/annex/images/essays/JDK6%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%B8%B8%E9%87%8F%E6%B1%A0%E6%A1%88%E4%BE%8B%E8%A7%A3%E6%9E%90.png"></p>
+<p>JDK1.7起，将这个字符串对象尝试放入字符串常量池：</p>
+<ul>
+<li>如果串池中有，则并不会放入，并返回已有的串池中的对象的地址；</li>
+<li>如果没有，则会把<strong>对象的引用地址复制一份，放入串池</strong>，并返回串池中的引用地址；</li>
+</ul>
+<p><img alt="JDK78字符串常量池案例解析" src="/iblog/posts/annex/images/essays/JDK78%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%B8%B8%E9%87%8F%E6%B1%A0%E6%A1%88%E4%BE%8B%E8%A7%A3%E6%9E%90.png"></p>
+<h4 id="intern方法">intern方法</h4>
+<p>在Java中，字符串常量池是由JVM自动管理的，开发者通常不需要显式地将字符串加入到字符串常量池中。
+Java中的字符串常量池有以下几种方式来存储字符串：</p>
+<ul>
+<li>直接量赋值: 当代码中直接使用双引号定义字符串时，例如 &ldquo;hello&rdquo;，这个字符串常量会自动被加入到字符串常量池中。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;hello&#34;</span><span class="p">;</span><span class="w"> </span><span class="c1">// &#34;hello&#34;会被加入字符串常量池</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;hel&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;lo&#34;</span><span class="p">;</span><span class="w"> </span><span class="c1">// 编译器会将&#34;hel&#34; + &#34;lo&#34;优化为&#34;hello&#34;，并将&#34;hello&#34;放入字符串常量池</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>调用String类的<code>intern()</code>方法：调用这个方法可以将字符串添加到字符串常量池中，并返回常量池中字符串的引用。
+如果字符串常量池中已经存在相同内容的字符串，则返回常量池中字符串的引用。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">).</span><span class="na">intern</span><span class="p">();</span><span class="w"> </span><span class="c1">// 将字符串&#34;hello&#34;添加到字符串常量池，并返回常量池中的引用</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>关于<code>intern</code>是一个<code>native</code>方法，调用的是底层C的方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="o">/**</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">Returns</span> <span class="n">a</span> <span class="n">canonical</span> <span class="n">representation</span> <span class="k">for</span> <span class="n">the</span> <span class="n">string</span> <span class="n">object</span><span class="o">.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">p</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">A</span> <span class="n">pool</span> <span class="n">of</span> <span class="n">strings</span><span class="p">,</span> <span class="n">initially</span> <span class="n">empty</span><span class="p">,</span> <span class="n">is</span> <span class="n">maintained</span> <span class="n">privately</span> <span class="n">by</span> <span class="n">the</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="k">class</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="ne">String</span><span class="p">}</span><span class="o">.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">p</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">When</span> <span class="n">the</span> <span class="n">intern</span> <span class="n">method</span> <span class="n">is</span> <span class="n">invoked</span><span class="p">,</span> <span class="k">if</span> <span class="n">the</span> <span class="n">pool</span> <span class="n">already</span> <span class="n">contains</span> <span class="n">a</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">string</span> <span class="n">equal</span> <span class="n">to</span> <span class="n">this</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="ne">String</span><span class="p">}</span> <span class="n">object</span> <span class="n">as</span> <span class="n">determined</span> <span class="n">by</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">the</span> <span class="p">{</span><span class="err">@</span><span class="n">link</span> <span class="c1">#equals(Object)} method, then the string from the pool is</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">returned</span><span class="o">.</span> <span class="n">Otherwise</span><span class="p">,</span> <span class="n">this</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="ne">String</span><span class="p">}</span> <span class="n">object</span> <span class="n">is</span> <span class="n">added</span> <span class="n">to</span> <span class="n">the</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">pool</span> <span class="ow">and</span> <span class="n">a</span> <span class="n">reference</span> <span class="n">to</span> <span class="n">this</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="ne">String</span><span class="p">}</span> <span class="n">object</span> <span class="n">is</span> <span class="n">returned</span><span class="o">.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">p</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">It</span> <span class="n">follows</span> <span class="n">that</span> <span class="k">for</span> <span class="n">any</span> <span class="n">two</span> <span class="n">strings</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="n">s</span><span class="p">}</span> <span class="ow">and</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="n">t</span><span class="p">},</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="n">s</span><span class="o">.</span><span class="n">intern</span><span class="p">()</span> <span class="o">==</span> <span class="n">t</span><span class="o">.</span><span class="n">intern</span><span class="p">()}</span> <span class="n">is</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="bp">true</span><span class="p">}</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="k">if</span> <span class="ow">and</span> <span class="n">only</span> <span class="k">if</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="n">s</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">t</span><span class="p">)}</span> <span class="n">is</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="bp">true</span><span class="p">}</span><span class="o">.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">p</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">All</span> <span class="n">literal</span> <span class="n">strings</span> <span class="ow">and</span> <span class="n">string</span><span class="o">-</span><span class="n">valued</span> <span class="n">constant</span> <span class="n">expressions</span> <span class="n">are</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">interned</span><span class="o">.</span> <span class="ne">String</span> <span class="n">literals</span> <span class="n">are</span> <span class="n">defined</span> <span class="ow">in</span> <span class="n">section</span> <span class="mf">3.10</span><span class="o">.</span><span class="mi">5</span> <span class="n">of</span> <span class="n">the</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">cite</span><span class="o">&gt;</span><span class="n">The</span> <span class="n">Java</span><span class="o">&amp;</span><span class="n">trade</span><span class="p">;</span> <span class="n">Language</span> <span class="n">Specification</span><span class="o">&lt;/</span><span class="n">cite</span><span class="o">&gt;.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="n">native</span> <span class="ne">String</span> <span class="n">intern</span><span class="p">();</span>
+</span></span></code></pre></div><p><code>intern</code>方法文档注释大意是：字符串池最初是空的，由String类私有地维护。
+在调用<code>intern</code>方法时，如果池中已经包含了由<code>equals(object)</code>方法确定的与该字符串对象相等的字符串，则返回池中的字符串。
+否则，该字符串对象将被添加到池中，并返回对该字符串对象的引用。</p>
+<p>下面示例中s1和s2采用<code>new String()</code>的方式新建了两个不同字符串，而s3和s4是通过<code>s1.intern()</code>方法取得一个字符串引用。
+<code>intern()</code>首先把s1引用的字符串放到<code>String Pool</code>中，然后返回这个字符串引用，因此s3和s4引用的是同一个字符串。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;aaa&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;aaa&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s2</span><span class="p">);</span><span class="w">           </span><span class="c1">// false</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">intern</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">intern</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s3</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s4</span><span class="p">);</span><span class="w">           </span><span class="c1">// true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>对于程序中大量使用存在的字符串时，尤其存在很多已经重复的字符串时，使用<code>intern()</code>方法能够节省内存空间。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">MAX_COUNT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1000</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">10000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[</span><span class="n">MAX_COUNT</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="w"> </span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="o">[]</span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="p">,</span><span class="n">6</span><span class="p">,</span><span class="n">7</span><span class="p">,</span><span class="n">8</span><span class="p">,</span><span class="n">9</span><span class="p">,</span><span class="n">10</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAX_COUNT</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//            arr[i] = new String(String.valueOf(data[i%data.length])); // 花费的时间为：3074</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">%</span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">)).</span><span class="na">intern</span><span class="p">();</span><span class="w"> </span><span class="c1">// 花费的时间为：1196</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;花费的时间为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">end</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">start</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">getStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">gc</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>不使用<code>intern</code>方法
+<img alt="不用intern方法测试" src="/iblog/posts/annex/images/essays/%E4%B8%8D%E7%94%A8intern%E6%96%B9%E6%B3%95%E6%B5%8B%E8%AF%95.png"></p>
+<p>使用<code>intern</code>方法后
+<img alt="使用intern方法测试" src="/iblog/posts/annex/images/essays/%E4%BD%BF%E7%94%A8intern%E6%96%B9%E6%B3%95%E6%B5%8B%E8%AF%95.png"></p>
+<h4 id="字符串常量池长度">字符串常量池长度</h4>
+<p>字符串常量池是不会存储相同内容的字符串的，字符串常量池其实是一个固定大小的<code>Hashtable</code>。
+如果放进字符串常量池的字符串非常多，就会造成Hash冲突严重，从而导致链表会很长，而链表长了后直接会造成的影响就是当调用<code>String.intern()</code>时性能会大幅下降。</p>
+<p>使用参数<code>-XX:StringTablesize</code>可设置字符串常量池的的长度，可以配置不同版本的Java，运行下列代码，使用命令进行查看<code>stringTableSize</code>大小：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">jsp(获取程序进程ID) -&gt; jinfo -flag StringTableSize 进程ID
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>不同JDK版本字符串常量池的的长度：</p>
+<ul>
+<li>在JDK6中<code>stringTable</code>是固定的，为1009的长度，所以如果常量池中的字符串过多就会导致效率下降很快。<code>-XX:StringTablesize</code>设置没有要求，可随意设置；</li>
+<li>在JDK7中，<code>stringTable</code>的长度默认值是60013，<code>-XX:StringTablesize</code>设置没有要求，可随意设置；</li>
+<li>在JDK8中，<code>stringTable</code>的长度默认为 60013，但不能低于 1009。</li>
+</ul>
+<h3 id="使用">使用</h3>
+<h4 id="创建字符串">创建字符串</h4>
+<p>创建字符串，常见的大概有这么几种方式：</p>
+<ol>
+<li><code>String</code>直接创建
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>String</code>对象创建
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;123&#34;</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>String</code>引用创建
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str1</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>格式化创建字符串
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;浮点型变量: %f, 整型变量: %d, 字符串变量: %s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">.</span><span class="na">0f</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<p>所有<code>String</code>对象都是不可变的，一旦创建，其内容不能改变，这使得字符串在多线程环境中是安全的。
+通过字面量的方式创建给一个字符串赋值，存储在字符串常量池中，而<code>new</code>创建的字符串对象在堆上。</p>
+<h4 id="拼接字符串">拼接字符串</h4>
+<p>因为<code>String</code>类是不可变的，所以所谓字符串拼接，都是重新生成了一个新的字符串。
+以下是字符串的几种拼接的方式：</p>
+<ol>
+<li>使用<code>concat</code>方法连接字符串
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">.</span><span class="na">concat</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str2</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>用&rdquo;+&ldquo;连接字符串
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 在编译时会编译成 String str4 = &#34;123456&#34;;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;456&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 会调用StringBuilder.append方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;789&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str4</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>用JDK内置处理字符串类<code>Stringbuilder</code>, <code>StringBuffer</code>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">StringBuilder</span><span class="w"> </span><span class="n">builder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">StringBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuffer</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">builder</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">str</span><span class="p">).</span><span class="na">append</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">).</span><span class="na">toString</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">str</span><span class="p">).</span><span class="na">append</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">).</span><span class="na">toString</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str6</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>Java8新增<code>String.join</code>方法连接字符串
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str7</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">join</span><span class="p">(</span><span class="s">&#34;-&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str8</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">join</span><span class="p">(</span><span class="s">&#34;~&#34;</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[]</span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="s">&#34;3&#34;</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str7</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str8</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>用第三方处理字符串工具类，例如: <code>apache.commons</code>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// Java8提供的String.join方法和`apache.commons`方法相似.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 主要作用是将数组或集合以某拼接符拼接到一起形成新的字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str9</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StringUtils</span><span class="p">.</span><span class="na">join</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[]</span><span class="p">{</span><span class="n">str</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;456&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;789&#34;</span><span class="p">});</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<p>如果在处理大量字符串的时候就需要注意性能和耗时，以下是耗时比较(短-&gt;长)：<code>StringBuilder</code>&lt;<code>StringBuffer</code>&lt;<code>concat</code>&lt;<code>+</code>&lt;<code>StringUtils.join</code> 。</p>
+<h4 id="拼接原理">“+”拼接原理</h4>
+<p>拼接字符串最简单的方式就是直接使用符号&rdquo;+&ldquo;来拼接，其实“+”是Java提供的一个语法糖。
+语法糖（Syntactic sugar），也译为糖衣语法，是由英国计算机科学家彼得·兰丁发明的一个术语，指计算机语言中添加的某种语法，这种语法对语言的功能没有影响，但是更方便程序员使用。
+语法糖让程序更加简洁，有更高的可读性。</p>
+<p>为了探究“+”拼接的原理，用<code>javap -verbose</code>命令进行反编译看一下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;456&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">str2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">  public static void main(java.lang.String[]);
+</span></span><span class="line"><span class="cl">    descriptor: ([Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">    flags: ACC_PUBLIC, ACC_STATIC
+</span></span><span class="line"><span class="cl">    Code:
+</span></span><span class="line"><span class="cl">      stack=2, locals=4, args_size=1
+</span></span><span class="line"><span class="cl">         0: ldc           #2                  // String 123
+</span></span><span class="line"><span class="cl">         2: astore_1
+</span></span><span class="line"><span class="cl">         3: ldc           #3                  // String 456
+</span></span><span class="line"><span class="cl">         5: astore_2
+</span></span><span class="line"><span class="cl">         6: new           #4                  // class java/lang/StringBuilder
+</span></span><span class="line"><span class="cl">         9: dup
+</span></span><span class="line"><span class="cl">        10: invokespecial #5                  // Method java/lang/StringBuilder.&#34;&lt;init&gt;&#34;:()V
+</span></span><span class="line"><span class="cl">        13: aload_1
+</span></span><span class="line"><span class="cl">        14: invokevirtual #6                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
+</span></span><span class="line"><span class="cl">        17: aload_2
+</span></span><span class="line"><span class="cl">        18: invokevirtual #6                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
+</span></span><span class="line"><span class="cl">        21: invokevirtual #7                  // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
+</span></span><span class="line"><span class="cl">        24: astore_3
+</span></span><span class="line"><span class="cl">        25: getstatic     #8                  // Field java/lang/System.out:Ljava/io/PrintStream;
+</span></span><span class="line"><span class="cl">        28: aload_3
+</span></span><span class="line"><span class="cl">        29: invokevirtual #9                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">        32: return
+</span></span><span class="line"><span class="cl">      // ...
+</span></span></code></pre></div><p>可以看到在字符串拼接过程中，是将<code>String</code>转成了<code>StringBuilder</code>后，使用<code>append</code>方法进行拼接字符串处理的，最后在去调用<code>StringBuilder</code>的<code>toString</code>方法进行返回。
+在JDK5之后，使用的是<code>StringBuilder</code>，在JDK5之前使用的是<code>StringBuffer</code>。</p>
+<p>知道了“+”底层之后，如果在循环中，使用“+”拼接字符串，会创建大量的<code>StringBuilder</code>对象，造成内存的浪费。
+所以对于大量字符串拼接操作，推荐使用<code>StringBuilder</code>或<code>StringBuffer</code>以提高性能。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 不推荐</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">StringConcatExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">result</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">length</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 推荐</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">StringBuilderExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">result</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">length</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="stringbuffer与stringbuilder">StringBuffer与StringBuilder</h4>
+<p><code>Stringbuilder</code>和<code>StringBuffer</code>是字符串拼接的两种实现类，它们有相同的父类：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractStringBuilder</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Appendable</span><span class="p">,</span><span class="w"> </span><span class="n">CharSequence</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * The value is used for character storage.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * The count is the number of characters used.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>StringBuffer</code>和<code>StringBuilder</code>是 Java 提供的用于处理字符串的类，二者的主要区别在于线程安全性和性能方面。拿<code>append</code>方法举例：</p>
+<ul>
+<li><code>StringBuilder.append</code>方法
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">StringBuilder</span><span class="w"> </span><span class="nf">append</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">str</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>StringBuffer.append</code>方法
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">  </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="n">StringBuffer</span><span class="w"> </span><span class="nf">append</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">toStringCache</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="kd">super</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">str</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>由此可以看出<code>StringBuilder</code>和<code>StringBuffer</code>原理是相似的，最大的区别就是<code>StringBuffer</code>是线程安全的，原因是用了<code>synchronized</code>修饰。
+<code>StringBuffer</code>是线程安全的，因为它的方法都是同步的，这意味着它是安全的，可以在多线程环境中使用。
+由于其线程安全性，每个方法调用都有同步开销，所以<code>StringBuffer</code>的性能比<code>StringBuilder</code>稍慢。</p>
+<p>与<code>String</code>类不同的是，<code>StringBuffer</code>和<code>StringBuilder</code>类的对象能够被多次的修改，并且不产生新的未使用对象。
+如果你需要一个可修改的字符串，应该使用<code>StringBuffer</code>或者<code>StringBuilder</code>，但是会有大量时间浪费在垃圾回收上，因为每次试图修改都有新的<code>String</code>对象被创建出来。</p>
+<p>通过<code>StringBuilder</code>的<code>append()</code>方式添加字符串的效率，要远远高于<code>String</code>的字符串拼接方法。
+在实际开发中还可以进行优化，<code>StringBuilder</code>的空参构造器，默认的字符串容量是16，如果需要存放的数据过多，容量就会进行扩容，我们可以设置默认初始化更大的长度，来减少扩容的次数。
+如果我们能够确定，前前后后需要添加的字符串不高于某个限定值，那么建议使用构造器创建一个阈值的长度。</p>
+<h4 id="常用方法">常用方法</h4>
+<p>基于Java8整理，如果查看其他方法请参照<a href="https://docs.oracle.com/javase/8/docs/api/index.html">Java8API官方文档</a>。</p>
+<ul>
+<li><code>substring</code>对字符串进行截取.返回一个新的字符串，它是此字符串的一个子字符串；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123456&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">substring</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 3456</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">substring</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 索引从1开始截取字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">substring2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 34</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">substring2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>replace</code>替换字符串.返回一个新的字符串，它是通过用 <code>newChar</code> 替换此字符串中出现的所有 <code>oldChar</code> 得到的；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123456&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 223456</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str</span><span class="p">.</span><span class="na">replace</span><span class="p">(</span><span class="sc">&#39;1&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;2&#39;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>replaceAll</code>使用给定的 <code>replacement</code> 替换此字符串所有匹配给定的正则表达式的子字符串；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;111111&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 222222</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str</span><span class="p">.</span><span class="na">replaceAll</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>valueOf</code>该方法作用是将对象转成<code>String</code>类型；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Integer</span><span class="w"> </span><span class="n">integer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">11111</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">integer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 11111</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="长度限制">长度限制</h3>
+<p>Java中的<code>String</code>内部是用一个字符数组<code>char[]</code>存储字符数据的，数组的最大长度限制由Java虚拟机规范决定。
+所以理论上，Java数组的最大长度是<code>Integer.MAX_VALUE(2^31 - 1)</code>，即2147483647，这也是String的长度限制，但在实际操作中，能分配的最大数组长度受可用内存限制。</p>
+<p>但是并不是这样，字符串字面量的长度不能超过65535字符，如果字符串字面量长度超过这个限制，编译器会抛出错误。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkStringConstant</span><span class="p">(</span><span class="n">DiagnosticPosition</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">nerrs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">((</span><span class="n">String</span><span class="p">)</span><span class="n">var2</span><span class="p">).</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">65535</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">log</span><span class="p">.</span><span class="na">error</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;limit.string&#34;</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="o">++</span><span class="k">this</span><span class="p">.</span><span class="na">nerrs</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>还有一点，<code>Stirng</code>长度之所以会受限制，是因JVM规范对常量池有所限制。
+<a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.7">CONSTANT_Utf8_info</a>是一个<code>CONSTANT_Utf8</code>类型的常量池数据项，它存储的是一个常量字符串。
+常量池中的所有字面量几乎都是通过<code>CONSTANT_Utf8_info</code>描述的，<code>CONSTANT_Utf8_info</code>的定义如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">ONSTANT_Utf8_info {
+</span></span><span class="line"><span class="cl">    u1 tag;
+</span></span><span class="line"><span class="cl">    u2 length;
+</span></span><span class="line"><span class="cl">    u1 bytes[length];
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><ul>
+<li><code>tag</code>：<code>CONSTANT_Utf8_info</code>结构的标记项值为<code>CONSTANT_Utf8(1)</code>；</li>
+<li><code>length</code>：<code>length</code>项的值表示字节数组中的字节数，而不是结果字符串的长度，其类型为<code>u2</code>；</li>
+<li><code>bytes[]</code>：字节数组包含字符串的字节数；</li>
+</ul>
+<p>到了这里长度终于出来了，那就是<code>length</code>。通过查阅《JVM规范》发现<code>u2</code>表示两个字节的无符号数，那么1个字节有8位，2个字节就有16位。
+16位无符号数可表示的最大值位<code>2^16 - 1 = 65535</code>。也就是说，<code>Class</code>文件中常量池的格式规定了，每个字符串常量的最大长度为65535字节。</p>
+<p>所以对<code>String</code>的长度限制主要有两点：</p>
+<ol>
+<li><code>Class</code>文件中常量池的格式规定了，每个字符串常量的最大长度为65535字节；</li>
+<li><code>checkStringConstant</code>方法，规定字符串字面量的长度不能超过65535字符，即最大65534个字符；</li>
+</ol>
+<p>所以一个字符串字面量最多可以包含65534个字符，但它的存储空间（字节数）并不会超过65535字节。</p>
+<p>那么<code>String</code>类长度限制是多少？</p>
+<ul>
+<li>在编译期间，长度不能超过65535个字符，即最大65534个字符，但65534个字符存储空间不会超过65535字节；</li>
+<li>在运行期，<code>String</code>对象的长度理论上可以达到<code>Integer.MAX_VALUE (2^31 - 1)</code>个字符，即 2,147,483,647 个字符，大概4G。
+在实际应用中，字符串的最大长度受限于可用内存和JVM配置；</li>
+</ul>
+<p>在程序开发中，如果用<code>String</code>变量接收<code>Base64</code>图片或音频视频，需要注意不要超过程序运行时字符串的最大阈值。</p>
+<h3 id="string类与编码">String类与编码</h3>
+<p>Java中的<code>String</code>类是基于<code>Unicode</code>字符集设计的，它可以存储任意<code>Unicode</code>字符。
+<code>Unicode</code>为世界上几乎所有的字符集提供了唯一的标识码，因此Java的<code>String</code>类可以处理多语言字符和符号。</p>
+<h4 id="unicode">Unicode</h4>
+<p><code>Unicode</code>（中文：万国码、国际码、统一码、单一码）是计算机科学领域里的一项业界标准。
+它对世界上大部分的文字系统进行了整理、编码，使得计算机可以用更为简单的方式来呈现和处理文字。</p>
+<p><code>Unicode</code>伴随着通用字符集的标准而发展，同时也以书本的形式对外发表。<code>Unicode</code>至今仍在不断增修，每个新版本都加入更多新的字符。
+目前最新的版本为2018年6月5日公布的11.0.0，已经收录超过13万个字符（第十万个字符在2005年获采纳）。
+<code>Unicode</code>涵盖的数据除了视觉上的字形、编码方法、标准的字符编码外，还包含了字符特性，如大小写字母。</p>
+<p><code>Unicode</code>是一种编码规范，是为解决全球字符通用编码而设计的，而<code>UTF-8</code>、<code>UTF-16</code>等是这种规范的一种实现，<code>Unicode</code>是字符集而<code>UTF-8</code>是编码规则。
+在Java虚拟机内部，<code>String</code>对象的存储是以<code>UTF-16</code>编码形式进行的。<code>UTF-16</code>编码是一种<code>Unicode</code>字符集的编码方式，它采用16位（即2个字节）编码单元来表示大部分字符，辅助字符则需要使用4个字节来表示。</p>
+<p>不管程序过程中用到了<code>GBK</code>还是<code>ISO8859-1</code>等格式，在存储与传递的过程中实际传递的都是<code>Unicode</code>编码的数据，要想接收到的值不出现乱码，就要保证传过去的时候用的是X编码，接收的时候也用X编码来转换接收。</p>
+<h4 id="编码与解码">编码与解码</h4>
+<p>字符串的编码和解码在Java中是非常常见和重要的操作，特别是在处理文件、网络通信或与外部系统交互时。</p>
+<ul>
+<li>编码是将字符串转换为字节序列的过程；</li>
+<li>解码是将字节序列转换为字符串的过程；</li>
+</ul>
+<p>字符串的编码和解码代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">StringEncodingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">originalString</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello, 你好&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">charsetName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;UTF-8&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编码：String -&gt; byte[]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">utf8Bytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">originalString</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(</span><span class="n">charsetName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Encoded UTF-8 bytes: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">bytesToHex</span><span class="p">(</span><span class="n">utf8Bytes</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 解码：byte[] -&gt; String</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">decodedString</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="n">utf8Bytes</span><span class="p">,</span><span class="w"> </span><span class="n">charsetName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Decoded String: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">decodedString</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">UnsupportedEncodingException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 辅助方法：将字节数组转换为十六进制字符串表示</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">bytesToHex</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">sb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">sb</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;%02X &#34;</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">sb</span><span class="p">.</span><span class="na">toString</span><span class="p">().</span><span class="na">trim</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在解码时，可能会出现乱码，原因是编码时格式和解码时格式不一致导致。
+即在编码时，是用一种编码，而在解码时，用的是另一种编码，所以导致乱码问题。所以想要避免乱码问题最简单的办法就是从始至终，都用同一种字符格式。</p>
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+        <a href="https://varkai.com">Designed by VarKai,</a>
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+
+    <div id="footer_slogan" class="footer_slogan">
+        <span>from 2021</span>
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+<script src="http://localhost:1313/iblog/js/darkmode.js"></script>
+<script src="http://localhost:1313/iblog/js/zozo.js"></script>
+<script src="//cdn1.lncld.net/static/js/3.0.4/av-min.js"></script>
+<script src="http://localhost:1313/iblog/js/busuanzi_2.3_busuanzi.pure.mini.js"></script>
+<script src="http://localhost:1313/iblog/js/html2canvas.js"></script>
+<script src="http://localhost:1313/iblog/js/utils.js"></script>
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+<script src="http://localhost:1313/iblog/js/fastsearch.js"></script>
+<script src="http://localhost:1313/iblog/js/fuse.js"></script>
+
+
+<script>
+    new Darkmode({
+        right: '32px', 
+        bottom: 'unset', 
+        
+        time: '0.15s', 
+        mixColor: '#f7f7f7', 
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+        buttonColorDark: '#212121', 
+        buttonColorLight: '#f7f7f7', 
+        saveInCookies: false, 
+        autoMatchOsTheme: true 
+    }).showWidget();
+
+    function addDarkmodeWidget(){
+        const hours = new Date().getHours();
+        if (hours >= 19 || hours <= 5){
+            new Darkmode({
+                right: '32px', 
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+                time: '0.3s', 
+                mixColor: '#f7f7f7', 
+                backgroundColor: '#f7f7f7', 
+                buttonColorDark: '#212121', 
+                buttonColorLight: '#f7f7f7', 
+                saveInCookies: false, 
+                autoMatchOsTheme: true 
+            }).toggle();
+        }
+    }
+    
+    
+</script>
+
+
+
+
+
+
+
+
+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/blog-site/public/posts/javabasics/rookie-exception/index.html b/blog-site/public/posts/javabasics/rookie-exception/index.html
new file mode 100644
index 00000000..86d8bb67
--- /dev/null
+++ b/blog-site/public/posts/javabasics/rookie-exception/index.html
@@ -0,0 +1,1236 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java异常 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="异常类型 Throwable可以用来表示任何可以作为异常抛出的类，分为两种：Error 和 Exception。 其中Error用来表示Java程序无法处理的错误，这类" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
+    
+
+	
+
+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%82%e5%b8%b8%e7%b1%bb%e5%9e%8b">
+                    异常类型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%87%aa%e5%ae%9a%e4%b9%89%e5%bc%82%e5%b8%b8">
+                    自定义异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%82%e5%b8%b8%e7%9a%84%e4%bc%a0%e6%92%ad">
+                    异常的传播
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%84%e7%90%86%e5%bc%82%e5%b8%b8">
+                    处理异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#try-catch">
+                    try-catch
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#try-catch-finally">
+                    try-catch-finally
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#throwsthrow">
+                    throws、throw
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%82%e5%b8%b8%e9%93%be">
+                    异常链
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%8f%e9%aa%8c%e6%80%bb%e7%bb%93">
+                    经验总结
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%8d%e8%a6%81%e6%bb%a5%e7%94%a8%e5%bc%82%e5%b8%b8">
+                    不要滥用异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%a9%bacatch">
+                    空catch
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%90%9e%e6%8e%89%e5%bc%82%e5%b8%b8">
+                    吞掉异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b2%be%e7%a1%ae%e5%a4%84%e7%90%86%e5%bc%82%e5%b8%b8">
+                    精确处理异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8a%9b%e5%87%ba%e5%bc%82%e5%b8%b8">
+                    抛出异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%89%e6%8b%a9%e5%bc%82%e5%b8%b8">
+                    选择异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%8d%e8%a6%81%e5%9c%a8finally%e4%b8%ad%e6%8a%9b%e5%bc%82%e5%b8%b8">
+                    不要在finally中抛异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e8%80%83%e6%96%87%e7%ab%a0">
+                    参考文章
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                        <h2 id="post_single_title">Java异常</h2>
+                        <span id="post_page_title_date" class="date">2021.01.13</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="异常类型">异常类型</h2>
+<p><img alt="Java异常分类" src="/iblog/posts/annex/images/essays/Java%E5%BC%82%E5%B8%B8%E5%88%86%E7%B1%BB.png"></p>
+<p><code>Throwable</code>可以用来表示任何可以作为异常抛出的类，分为两种：<code>Error</code> 和 <code>Exception</code>。
+其中<code>Error</code>用来表示Java程序无法处理的错误，这类错误一般与硬件有关，与程序本身无关，通常由系统进行处理，程序本身无法捕获和处理，是不可控制的。</p>
+<p><code>Exception</code>分为两种：运行时异常和检查型异常。</p>
+<ul>
+<li>受检异常：需要用<code>try...catch... </code>语句捕获并进行处理，并且可以从异常中恢复；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">MyException</span><span class="p">{}</span><span class="w">
+</span></span></span></code></pre></div>Java编译器对检查性异常会要求我们进行<code>catch</code>，必须得进行捕获，否则编译不过去。Java认为检查性异常都可以被处理，所以必须显示的处理<code>checked</code>异常。
+常见的检查性异常有<code>IOException</code>、<code>SqlException</code>。当我们希望我们的⽅法调⽤者，明确的处理⼀些特殊情况的时候，就应该使⽤受检异常。</li>
+<li>非受检异常：是程序运行时错误。例如：除0会引发 <code>ArithmeticException</code>，此时程序崩溃并且无法恢复。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="o">/</span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div>这种异常⼀般可以理解为是代码原因导致的。⽐如发⽣空指针、数组越界等。所以，只要代码写的没问题，这些异常都是可以避免的。也就不需要我们显⽰的进⾏处理。</li>
+</ul>
+<p><code>Exception</code>表⽰程序需要捕捉、需要处理的常，是由与程序设计的不完善⽽出现的问题，程序必须处理的问题。
+异常和错误的区别是，异常能被程序本身可以处理，错误是无法处理。</p>
+<h2 id="自定义异常">自定义异常</h2>
+<p>在Java中，自定义异常类可以帮助你创建特定于你的应用程序的异常类型，这些异常类型可以提供更清晰的错误描述，并使错误处理更加灵活和精确。
+在Java中自定义异常，但所有自定义异常都必须是<code>Throwable</code>的子类。
+如果希望写一个检查性异常类，则需要继承<code>Exception</code>类。如果你想写一个运行时异常类，那么需要继承<code>RuntimeException</code>类。</p>
+<p>自定义受检查异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 创建一个自定义的受检查异常类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyCheckedException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyCheckedException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyCheckedException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用自定义异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Test</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">MyCheckedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 条件判断或业务逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyCheckedException</span><span class="p">(</span><span class="s">&#34;This is a custom checked exception.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>自定义运行时异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 创建一个自定义的非受检查异常类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyUncheckedException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">RuntimeException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyUncheckedException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyUncheckedException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用自定义异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Test</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 条件判断或业务逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyUncheckedException</span><span class="p">(</span><span class="s">&#34;This is a custom unchecked exception.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="异常的传播">异常的传播</h2>
+<p>在Java中，异常传播指的是当一个方法内部抛出异常时，异常如何在调用栈中向上传播的过程。
+理解异常传播是异常处理机制中的重要部分，对于编写健壮的代码和良好的异常处理策略至关重要。</p>
+<p>当一个方法内部抛出异常时，异常会沿着调用链向上传播给调用者。这个过程描述了异常如何从方法内部向外部传递，并最终在调用栈中找到合适的异常处理器来处理异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExceptionPropagationExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">method1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception caught in main method: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method1</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">method2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">RuntimeException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;RuntimeException caught in method1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method2</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">method3</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method3</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 人为地抛出一个异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;Exception occurred in method3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>异常传播的基本过程：</p>
+<ol>
+<li>当方法内部抛出一个异常（使用<code>throw</code>关键字），异常对象被创建并包含了当前异常的堆栈信息，包括方法调用路径。</li>
+<li>异常从抛出它的方法开始，沿着方法调用链向上传播。每当方法内部抛出异常时，JVM将控制权传递给调用该方法的上级方法。</li>
+<li>异常会继续沿着调用链向上移动，直到找到合适的异常处理器来处理异常。处理器可以是<code>try-catch</code>块、异常处理方法或者不处理异常而继续向上传播。</li>
+<li>如果找到了与抛出的异常匹配的<code>catch</code>块或者方法签名中声明的<code>throws</code>子句，异常被捕获并在这里进行处理。处理可以包括记录日志、恢复操作或者向上抛出另一个异常。</li>
+<li>如果异常没有在当前方法中被捕获处理，它将继续向上传播，控制权交给调用当前方法的方法。这个过程继续直到异常被捕获或者传播到了调用栈的顶部。</li>
+<li>如果异常传播到了调用栈的顶部仍然没有被处理，通常情况下会导致程序终止，并打印异常的堆栈跟踪信息，这有助于开发人员定位和解决问题。</li>
+</ol>
+<h2 id="处理异常">处理异常</h2>
+<p>异常的处理⽅式有两种，⾃⼰处理，向上抛出交给调⽤者处理。</p>
+<p>需要注意的是，一般情况下不要丢弃异常，捕获异常后需要进行相关处理。
+如果用户觉得不能很好地处理该异常，就让它继续传播，传到别的地方去处理，或者把一个低级的异常转换成应用级的异常，重新抛出。
+千万不能捕获了之后什么也不做，或者只是使⽤<code>e.printStacktrace</code>。如果是练习这样写也就算了，但是在正式的环境上千万不能这样做。实际开发中应该使用日志记录。</p>
+<p>写完代码后请一定要检查下，代码中千万不要有<code>printStackTrace</code>。
+不能直接使用<code>printStackTrace</code>打印异常的原因在于它可能泄露敏感信息、未将异常信息记录到日志系统中、使得错误难以追踪和管理、影响系统性能，并且通常缺乏必要的上下文信息。
+因此，在正式开发中，应使用日志框架记录异常信息，以便更好地监控和调试应用程序。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExceptionHandlingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Logger</span><span class="w"> </span><span class="n">logger</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">LoggerFactory</span><span class="p">.</span><span class="na">getLogger</span><span class="p">(</span><span class="n">ExceptionHandlingExample</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">divide</span><span class="p">(</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 使用日志记录异常信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">logger</span><span class="p">.</span><span class="na">error</span><span class="p">(</span><span class="s">&#34;Division by zero error&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 或者根据业务逻辑重新抛出应用级异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CustomApplicationException</span><span class="p">(</span><span class="s">&#34;Failed to divide numbers&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 自定义应用级异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CustomApplicationException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">RuntimeException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CustomApplicationException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="try-catch">try-catch</h3>
+<p>自己处理异常指在当前方法内部通过<code>try-catch</code>语句捕获并处理异常，而不是将异常传播给调用者处理。
+这种方式适合于可以预见并且能够恢复的异常情况。处理异常的目的是在发生异常时执行某些逻辑，例如提供默认值、记录日志、给用户友好的错误提示等。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExceptionHandlingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">divide</span><span class="p">(</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error: Division by zero is not allowed. Defaulting result to 0.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 给出一个默认值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在Java中，一个<code>try</code>语句可以对应多个<code>catch</code>块来进行多重捕获。
+如果在<code>try</code>语句块中发生异常，异常会被依次传递给每个<code>catch</code>块，直到找到匹配的<code>catch</code>块进行处理。如果没有匹配的<code>catch</code>块，异常会继续向上抛出。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MultiCatchExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">numbers</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">numbers</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">);</span><span class="w"> </span><span class="c1">// ArrayIndexOutOfBoundsException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="c1">// ArithmeticException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArrayIndexOutOfBoundsException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Array index is out of bounds: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Arithmetic error occurred: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;An unexpected error occurred: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>从JDK7开始，Java引入了多个异常类型的合并处理，这使得可以将多个不同类型的异常在一个<code>catch</code>块中捕获和处理。
+这种特性可以减少重复的代码，并提高异常处理的简洁性和可读性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MultiCatchExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">numbers</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">numbers</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">);</span><span class="w"> </span><span class="c1">// ArrayIndexOutOfBoundsException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="c1">// ArithmeticException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArrayIndexOutOfBoundsException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;An error occurred: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;An unexpected error occurred: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="try-catch-finally">try-catch-finally</h3>
+<p><code>try</code> 语句块不止可以与 <code>catch</code> 连用，也可以与<code>finally</code>连用，但是 <code>catch</code> 不能与 <code>finally</code> 连用。
+<code>try-catch-finally</code>结构与异常密切相关，它是Java中用于处理异常的基本结构之一，用于确保资源的正确关闭和异常的正确处理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TryCatchFinallyExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BufferedReader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileReader</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">line</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">line</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">readLine</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">line</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error reading file: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">reader</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">reader</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w"> </span><span class="c1">// 确保关闭资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error closing reader: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>根据JVM规范，如果<code>try</code>语句块里边有返回值则返回<code>try</code>语句块里边的；
+如果<code>try</code>语句块和<code>finally</code>语句块都有<code>return</code>，则忽略<code>try</code>语句块里边的使用<code>finally</code>语句块里边的<code>return</code>；
+<code>finally</code>语句块是在<code>try</code>语句块或者<code>catch</code>语句块中的<code>return</code>语句之前执行的，无论是否发生异常，<code>finally</code>代码块中的代码总会被执行。
+一般情况下如果方法有返回值，切忌不要在<code>finally</code>中写<code>return</code>，这样会使得程序结构变得混乱。</p>
+<blockquote>
+<p><code>finally</code>语句块什么时候不执行？
+如果当一个线程在执行<code>try</code>语句块或者<code>catch</code>语句块时被打断（interrupted）或者被终止（killed）或退出虚拟机(<code>System.exit(0)</code>)，与其相对应的<code>finally</code>语句块可能不会执行。
+还有更极端的情况，就是在线程运行<code>try</code>语句块或者<code>catch</code>语句块时，突然死机或者断电，<code>finally</code>语句块肯定不会执行了。</p>
+</blockquote>
+<p>无论是否发生异常，<code>finally</code>代码块中的代码总会被执行。根据这个特性，<code>finally</code>块确保在代码执行过程中发生异常时，资源得到正确释放，所以经常用来关闭资源。
+自从JDK7之后，支持<code>try-with-resources</code>的写法，这种写法对比之前更清晰、明了：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">InputStream</span><span class="w"> </span><span class="n">in</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;awsl&#34;</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">in</span><span class="p">.</span><span class="na">read</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>JVM先会把<code>try</code>或者<code>catch</code>代码块中的返回值保留，再来执行<code>finally</code>代码块中的语句，等到<code>finally</code>代码块执行完毕之后，在把之前保留的返回值给返回出去。
+这条规则只适用于<code>return</code>和<code>throw</code>语句，不适用于<code>break</code>和<code>continue</code>语句，因为它们根本就没有返回值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// main 代码块中的执行结果为：1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;main 代码块中的执行结果为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">myMethod</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;try 代码块被执行！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="o">++</span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;finally 代码块被执行！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;finally 代码块中的i = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="throwsthrow">throws、throw</h3>
+<p>向上抛出交给调用者处理，这种方式通过在方法签名中使用<code>throws</code>关键字将异常向上抛出，交由调用该方法的代码处理。适用于方法本身无法或者不适合处理异常的情况。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExceptionHandlingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">process</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">process</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">divide</span><span class="p">(</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Caught ArithmeticException: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 处理部分异常逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 可能抛出其他类型的异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Exception</span><span class="p">(</span><span class="s">&#34;A different kind of exception occurred.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">ArithmeticException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>throws</code>用在方法上声明异常，子类继承的时候要继承该异常或者该异常的子类，不处理异常，谁调用该方法谁处理异常。
+<code>throws</code>抛出异常时，它的调用者也要申明抛出异常或者捕获，不然编译报错。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">ArithmeticException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>throw</code>用于方法内部，抛出的是异常对象。调用者可以不申明或不捕获但编译器不会报错。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>throws</code>表示出现异常的一种可能性，告诉调用者这个方法是危险的，并不一定会发生这些异常。<code>throw</code>则是抛出了异常，执行<code>throw</code>则一定抛出了某种异常对象。
+两者都是消极处理异常的方式（这里的消极并不是说这种方式不好），只是抛出或者可能抛出异常，但是不会由方法去处理异常，真正的处理异常由此方法的上层调用处理。</p>
+<h3 id="异常链">异常链</h3>
+<p>异常链则是一种特定的异常处理技术，通过在捕获异常时将原始异常作为参数传递给新的异常，这样来保留原始异常的详细信息。
+如果因为一个异常你决定抛出⼀个新的异常，⼀定要包含原有的异常，这样处理程序才可以通过<code>getCause</code>方法和<code>initCause</code>⽅法来访问异常最终的根源。
+这样做有助于调试和了解错误的根本原因。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 定义一个自定义异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyCustomException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyCustomException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyCustomException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 一个可能抛出异常的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SomeService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟抛出一个IOException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IOException</span><span class="p">(</span><span class="s">&#34;IO error occurred&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用异常链来包装原始异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SomeService</span><span class="w"> </span><span class="n">service</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SomeService</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">service</span><span class="p">.</span><span class="na">doSomething</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 包装原始异常并抛出新的自定义异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyCustomException</span><span class="p">(</span><span class="s">&#34;Failed to do something due to IO error&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="经验总结">经验总结</h2>
+<p>处理异常是软件开发中至关重要的一部分，有效的异常处理可以提高系统的健壮性、可靠性和用户体验。以下是处理异常的一些经验总结。</p>
+<h3 id="不要滥用异常">不要滥用异常</h3>
+<p>要谨慎地使用异常，异常捕获的代价非常高昂，异常使用过多会严重影响程序的性能。
+如果在程序中能够用<code>if</code>语句和<code>boolean</code>变量来进行逻辑判断，那么尽量减少异常的使用，从而避免不必要的异常捕获和处理。</p>
+<h3 id="空catch">空catch</h3>
+<p>千万不要使用空的<code>catch</code>块：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">try{
+</span></span><span class="line"><span class="cl"> // ...
+</span></span><span class="line"><span class="cl">}catch(IOException e){
+</span></span><span class="line"><span class="cl">  // ...
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在捕获了异常之后什么都不做，相当于忽略了这个异常。空的<code>catch</code>块意味着你在程序中隐藏了错误和异常，并且很可能导致程序出现不可控的执行结果。
+如果你非常肯定捕获到的异常不会以任何方式对程序造成影响，最好用日志将该异常进行记录，以便日后方便更新和维护。</p>
+<h3 id="吞掉异常">吞掉异常</h3>
+<p>请不要在<code>catch</code>块中吞掉异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">catch (NoSuchMethodException e) {
+</span></span><span class="line"><span class="cl">   return null;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>不要不处理异常，而返回<code>null</code>，这样异常就会被吞掉，无法获取到任何失败信息，会给日后的问题排查带来巨大困难。</p>
+<h3 id="精确处理异常">精确处理异常</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public void foo() throws Exception { //错误做法
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>一定要尽量避免上面的代码，因为他的调用者完全不知道错误的原因到底是什么。
+在方法声明中，可以由方法抛出一些特定受检异常。如果有多个，那就分别抛出多个，这样这个方法的使用者才会分别针对每个异常做特定的处理，从而避免发生故障。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public void foo() throws SpecificException1, SpecificException2 { 
+</span></span><span class="line"><span class="cl">//正确做法
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>同样的在捕获异常时，也要注意，尽量捕获特定的子类，而不是直接捕获<code>Exception</code>类。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    someMethod();
+</span></span><span class="line"><span class="cl">} 
+</span></span><span class="line"><span class="cl">catch (Exception e) {
+</span></span><span class="line"><span class="cl">    log.error(&#34;method has failed&#34;, e);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>上面代码，最大的问题就是，如果<code>someMethod()</code>的开发者在里面新增了一个特定的异常，并且预期是调用方能够特殊的对他进行处理。
+但是调用者直接<code>catch了Exception</code>类，就会导致永远无法知道<code>someMethod</code>的具体变化细节。这久可能导致在运行的过程中在某一个时间点程序崩溃。
+更不要去捕获<code>Throwable</code>类，因为Java中的<code>Error</code>也可以是<code>Throwable</code>的子类。但是<code>Error</code>是Java虚拟机本身无法控制的。Java虚拟机甚至可能不会在出现任何错误时请求用户的<code>catch</code>子句。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    someMethod();
+</span></span><span class="line"><span class="cl">} 
+</span></span><span class="line"><span class="cl">catch (Throwable e) {
+</span></span><span class="line"><span class="cl">    log.error(&#34;method has failed&#34;, e);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p><code>OutOfMemoryError</code>和<code>StackOverflowError</code>便是典型的例子，它们都是由于一些超出应用处理范围的情况导致的。</p>
+<h3 id="抛出异常">抛出异常</h3>
+<p>通常情况下，在捕获异常的时候抛出异常，需要注意的是，要始终在自定义异常中，覆盖原有的异常，从而构成一条异常链，这样堆栈跟踪就不会丢失：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">catch (NoSuchMethodException e) {
+</span></span><span class="line"><span class="cl">    throw new MyServiceException(&#34;Some information: &#34; + e.getMessage());  //错误做法
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>上面的命令可能会丢失掉主异常的堆栈跟踪。正确的方法是：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">catch (NoSuchMethodException e) {
+</span></span><span class="line"><span class="cl">     throw new MyServiceException(&#34;Some information: &#34; , e);  //正确做法
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>需要注意的是，可以记录异常或抛出异常，但不要同时做：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">catch (NoSuchMethodException e) {
+</span></span><span class="line"><span class="cl">   log.error(&#34;Some information&#34;, e);
+</span></span><span class="line"><span class="cl">   throw e;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>抛出和日志记录可能会在日志文件中产生多个日志消息,这就会导致同一个问题，却在日志中有很多不同的错误信息，使得开发人员陷入混乱。</p>
+<h3 id="选择异常">选择异常</h3>
+<p>一旦你决定抛出异常，你就要决定抛出抛出检查异常还是非检查异常。</p>
+<p>检查异常导致了太多的<code>try…catch</code>代码，可能有很多检查异常对开发人员来说是无法合理地进行处理的，比如：<code>SQLException</code>，而开发人员却不得不去进行<code>try…catch</code>，这样就会导致经常出现这样一种情况：逻辑代码只有很少的几行，而进行异常捕获和处理的代码却有很多行。
+这样不仅导致逻辑代码阅读起来晦涩难懂，而且降低了程序的性能。</p>
+<p>建议尽量避免检查异常的使用，如果确实该异常情况出现很的普遍，需要提醒调用者注意处理的话，就使用检查异常；否则使用非检查异常。
+因此，在一般情况下，尽量将检查异常转变为非检查异常交给上层处理。</p>
+<h3 id="不要在finally中抛异常">不要在finally中抛异常</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">  someMethod();  //抛出 exceptionOne
+</span></span><span class="line"><span class="cl">}finally{
+</span></span><span class="line"><span class="cl">  cleanUp();    //如果在这里再抛出一个异常，那么try中的exception将会丢失
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在上面的例子中，如果<code>someMethod()</code>抛出一个异常，并且在<code>finally</code>块中，<code>cleanUp()</code>也抛出一个异常，那么初始的<code>exception</code>将永远丢失。
+但是如果你不想处理<code>someMethod()</code>中的异常，但是仍然需要做一些清理工作，那么在<code>finally</code>块中进行清理。不要使用<code>catch</code>块。</p>
+<h2 id="参考文章">参考文章</h2>
+<ul>
+<li><a href="https://www.hollischuang.com/archives/5528">https://www.hollischuang.com/archives/5528</a></li>
+<li><a href="https://stackify.com/best-practices-exceptions-java">https://stackify.com/best-practices-exceptions-java</a></li>
+</ul>
+</div>
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+                                    
+                                        <a href="http://localhost:1313/iblog/tags/java%E5%9F%BA%E7%A1%80/">Java基础</a>
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+                                    
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diff --git a/blog-site/public/posts/javabasics/rookie-generics/index.html b/blog-site/public/posts/javabasics/rookie-generics/index.html
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+                        <h2 id="post_single_title">Java泛型</h2>
+                        <span id="post_page_title_date" class="date">2024.07.15</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
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+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>在Java中，泛型是一种强大的编程特性，允许类、接口和方法在定义时声明一种参数化类型，而在使用时可以指定具体的类型参数。泛型的主要目的是提高代码的重用性和类型安全性。</p>
+<p>确切地说，泛型的本质是参数化类型，也就是在代码设计中，将类型作为参数进行传递和使用。这种参数化类型的设计使得代码可以更加灵活和通用，而不需要针对不同的数据类型重复编写类似的代码。
+Java泛型也是一种语法糖，在编译阶段完成类型的转换的工作，避免在运行时强制类型转换而出现<code>ClassCastException</code>，类型转化异常。举个例子，最常见的就是使用泛型集合：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;String&gt; names = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">names.add(&#34;Alice&#34;);
+</span></span><span class="line"><span class="cl">names.add(&#34;Bob&#34;);
+</span></span><span class="line"><span class="cl">// 不需要强制转换为 String
+</span></span><span class="line"><span class="cl">String first = names.get(0);
+</span></span></code></pre></div><p>需要注意的是，泛型在Java中是通过类型擦除来实现的，这意味着泛型信息只在编译时存在，而在运行时会被擦除。
+由于类型擦除，运行时不会保留泛型类型的具体信息。所以对于泛型类的实例，无法在运行时获取其具体的类型参数信息。</p>
+<h2 id="泛型特点">泛型特点</h2>
+<p>泛型的好处是在编译的时候检查类型安全，并且所有的强制转换都是自动和隐式的，提高代码的重用率。
+通过泛型，编译器能够在编译时检查类型，并确保类型参数的一致性，从而避免了因类型转换错误而导致的运行时异常。这种类型安全性大大提高了代码的健壮性和可靠性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;String&gt; names = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">names.add(&#34;Alice&#34;);
+</span></span><span class="line"><span class="cl">names.add(&#34;Bob&#34;);
+</span></span><span class="line"><span class="cl">String first = names.get(0); // 不需要强制转换为 String
+</span></span></code></pre></div><p>泛型允许编写通用的代码模板，适用于多种数据类型。通过泛型，可以在不同的上下文中重复使用同一段代码，而无需为每种数据类型都编写相似的代码逻辑，从而提高了代码的重用性和灵活性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 泛型方法，用于打印任意类型的数组元素
+</span></span><span class="line"><span class="cl">public static &lt;T&gt; void printArray(T[] arr) {
+</span></span><span class="line"><span class="cl">    for (T elem : arr) {
+</span></span><span class="line"><span class="cl">        System.out.print(elem + &#34; &#34;);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    System.out.println();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>使用泛型可以减少或消除代码中的类型转换，使代码更加简洁和易于理解。不再需要在每处使用到集合或类时进行手动类型转换，从而提高了代码的可读性和可维护性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Map&lt;String, Integer&gt; map = new HashMap&lt;&gt;();
+</span></span><span class="line"><span class="cl">map.put(&#34;one&#34;, 1);
+</span></span><span class="line"><span class="cl">map.put(&#34;two&#34;, 2);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 不需要强制转换为 Integer
+</span></span><span class="line"><span class="cl">int value = map.get(&#34;one&#34;);
+</span></span></code></pre></div><p>泛型在提高代码的类型安全性和重用性方面有很多优点，但也存在一些缺点和限制。
+例如，Java泛型是通过类型擦除实现的，这意味着在编译时会将泛型类型信息擦除掉，便于与旧版Java兼容。这导致在运行时无法获取泛型类型的具体信息。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;Integer&gt; intList = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">List&lt;String&gt; strList = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">System.out.println(intList.getClass() == strList.getClass());  // Output: true
+</span></span></code></pre></div><h2 id="类型擦除">类型擦除</h2>
+<p>Java中的泛型通过一种称为类型擦除的机制实现。声明了泛型的<code>.java</code>源代码，在编译生成<code>.class</code>文件之后，泛型相关的信息就消失了。
+可以认为，源代码中泛型相关的信息，就是提供给编译器用的，泛型信息对Java编译器可以见，而对Java虚拟机不可见。</p>
+<p>关于如何实现泛型，Java官方文档中有对应的解释，<a href="https://docs.oracle.com/javase/tutorial/java/generics/erasure.html">原文</a>如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Generics were introduced to the Java language to provide tighter type checks at compile time and to support generic programming. To implement generics, the Java compiler applies type erasure to:
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">- Replace all type parameters in generic types with their bounds or Object if the type parameters are unbounded. The produced bytecode, therefore, contains only ordinary classes, interfaces, and methods.
+</span></span><span class="line"><span class="cl">- Insert type casts if necessary to preserve type safety.
+</span></span><span class="line"><span class="cl">- Generate bridge methods to preserve polymorphism in extended generic types.
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Type erasure ensures that no new classes are created for parameterized types; consequently, generics incur no runtime overhead.
+</span></span></code></pre></div><p>以下是实现类型擦除的步骤：</p>
+<ol>
+<li>当你写泛型代码时，Java编译器会在编译阶段进行类型检查，确保你使用的类型是正确的。例如，如果你声明一个<code>List&lt;String&gt;</code>，编译器会确保你只能向这个列表添加字符串；</li>
+<li>一旦编译完成，所有的泛型类型信息都会被移除，这个过程叫做“类型擦除”。在类型擦除过程中：
+<ul>
+<li>泛型类型参数被替换：所有的泛型类型参数会被替换为它们的上界（如果没有指定上界，就替换为<code>Object</code>）。</li>
+<li>插入必要的类型转换：在必要的地方，编译器会插入类型转换，以确保类型安全。</li>
+</ul>
+</li>
+<li>当泛型类被继承，并且子类使用具体类型时，编译器会生成桥接方法来保证子类的方法正确覆盖父类的方法。桥接方法是编译器自动生成的，用来保证多态性和类型一致性；
+<br><br>假设有一个父类和一个子类：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;child value&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div>编译后，<code>Child</code>类中会有一个桥方法：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;child value&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 生成的桥方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">getValue</span><span class="p">();</span><span class="w"> </span><span class="c1">// 调用实际的getValue方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<p>在编译时，泛型类型参数会被替换为它们的上限。如果没有明确的上限，则替换为<code>Object</code>。泛型擦除示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 泛型类
+</span></span><span class="line"><span class="cl">public class Box&lt;T&gt; {
+</span></span><span class="line"><span class="cl">    private T value;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public void setValue(T value) {
+</span></span><span class="line"><span class="cl">        this.value = value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public T getValue() {
+</span></span><span class="line"><span class="cl">        return value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 使用泛型类
+</span></span><span class="line"><span class="cl">Box&lt;String&gt; stringBox = new Box&lt;&gt;();
+</span></span><span class="line"><span class="cl">stringBox.setValue(&#34;Hello&#34;);
+</span></span><span class="line"><span class="cl">String value = stringBox.getValue();
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 擦除后的类
+</span></span><span class="line"><span class="cl">public class Box {
+</span></span><span class="line"><span class="cl">    private Object value;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public void setValue(Object value) {
+</span></span><span class="line"><span class="cl">        this.value = value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public Object getValue() {
+</span></span><span class="line"><span class="cl">        return value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 使用擦除后的类
+</span></span><span class="line"><span class="cl">Box stringBox = new Box();
+</span></span><span class="line"><span class="cl">stringBox.setValue(&#34;Hello&#34;);
+</span></span><span class="line"><span class="cl">String value = (String) stringBox.getValue(); // 强制类型转换
+</span></span></code></pre></div><p>由于泛型类型在运行时被擦除，无法在运行时获取泛型的实际类型信息。这会导致某些操作无法进行。例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">genericMethod</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">t</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">T</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在静态方法或静态上下文中，无法直接引用泛型类的类型参数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">GenericClass</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态方法中不能使用泛型类的类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// public static void staticMethod(T value) { // 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//     // ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// }</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 解决方法：定义静态泛型方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">staticMethod</span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>无法直接创建泛型数组。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 无法直接创建泛型数组
+</span></span><span class="line"><span class="cl">// List&lt;String&gt;[] stringLists = new ArrayList&lt;String&gt;[10]; // 编译错误
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 解决方法：使用原始类型数组并进行类型转换
+</span></span><span class="line"><span class="cl">List&lt;String&gt;[] stringLists = (List&lt;String&gt;[]) new ArrayList[10];
+</span></span></code></pre></div><p>泛型类型参数不能是基本数据类型，如<code>int</code>、<code>char</code>，只能是类类型。这可能会导致额外的装箱和拆箱开销，从而影响性能。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 使用基本数据类型会导致编译错误
+</span></span><span class="line"><span class="cl">// List&lt;int&gt; intList = new ArrayList&lt;&gt;(); // 编译错误
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 解决方法：使用包装类
+</span></span><span class="line"><span class="cl">List&lt;Integer&gt; intList = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">intList.add(1);
+</span></span><span class="line"><span class="cl">int value = intList.get(0); // 需要拆箱操作
+</span></span></code></pre></div><h2 id="泛型与反射">泛型与反射</h2>
+<p>Java中的泛型是通过类型擦除来实现的，这意味着泛型信息只在编译期间存在，而在运行时则被擦除。所以反射在运行时无法直接获取具体的泛型类型信息。</p>
+<p>类型擦除是Java泛型的一种实现机制，目的是保持与旧版本的兼容性。在编译过程中，泛型类型被替换为其非泛型上限，通常是<code>Object</code>类，并在需要时插入类型转换。
+这样Java编译器在编译期间进行类型检查，而在运行时不保留泛型类型信息。</p>
+<p>通过反射可以绕过Java泛型的类型检查，这利用了Java泛型的类型擦除机制。在编译时，泛型类型被擦除，实际操作的对象是原始类型<code>Object</code>。
+这使得在运行时可以向泛型集合中插入不同类型的元素。但这种做法会导致类型安全性问题，所以在实际开发中应谨慎使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">  </span><span class="c1">//这样调用 add 方法只能存储整形，因为泛型类型的实例为 Integer</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;add&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="p">.</span><span class="na">class</span><span class="p">).</span><span class="na">invoke</span><span class="p">(</span><span class="n">list</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;string&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="c1">// 1 string</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="泛型类">泛型类</h2>
+<p>在类上使用泛型，从而使类能够处理多种数据类型，而无需为每种数据类型编写单独的类。泛型类在定义时指定了一个或多个类型参数，这些类型参数在类的实例化时被具体的类型所替换。
+定义泛型类时，类型参数放在类名后面的尖括号内。例如，T是一个常用的类型参数名称，但你可以使用任何有效的标识符。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">NumberBox</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">number</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">NumberBox</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">number</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">number</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>需要注意的是，静态成员不能使用泛型类型参数，因为静态成员在类加载时已经存在，而类型参数在实例化时才确定。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericClass</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态成员不能使用泛型类的类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// private static T staticValue; // 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态方法不能直接使用泛型类的类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// public static void staticMethod(T value) { // 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//     // ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// }</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 可以使用泛型方法来解决这个问题</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">staticMethod</span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>泛型类不只接受一个类型参数，它还可以接受多个类型参数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Pair</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Pair</span><span class="p">(</span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="nf">getKey</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>除此之外，泛型类可以直接继承自另一个泛型类。当泛型类继承另一个泛型类时，可以选择保留父类的泛型类型参数，也可以重新定义自己的泛型类型参数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 父类是一个泛型类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Box</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Box</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 子类继承自泛型父类并保留类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ChildBox</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Box</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ChildBox</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>子类也可以重新定义自己的泛型类型参数，与父类的类型参数可以不同。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 父类是一个泛型类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Box</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Box</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 子类继承自泛型父类，并重新定义类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ChildBox</span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Box</span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ChildBox</span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>关于泛型类需要注意的是，一个泛型类可以继承自一个普通类，不需要在继承语法上做特别的修改。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 父类是一个普通类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 省略部分代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 子类是一个泛型类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Child</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 省略部分代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>但是普通类不能继承泛型类的类型参数，因为类型参数在实例化时才被确定，而普通类在编译时就被确定了。</p>
+<p>在Java中，使用泛型创建对象时，必须指定类型参数T的具体数据类型，即在尖括号&lt;&gt;中传入具体的类型。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Box&lt;Integer&gt; intBox = new Box&lt;&gt;(); // 使用 Integer 类型
+</span></span><span class="line"><span class="cl">intBox.setValue(123);
+</span></span><span class="line"><span class="cl">Integer intValue = intBox.getValue();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Box&lt;String&gt; strBox = new Box&lt;&gt;(); // 使用 String 类型
+</span></span><span class="line"><span class="cl">strBox.setValue(&#34;Hello&#34;);
+</span></span><span class="line"><span class="cl">String strValue = strBox.getValue();
+</span></span></code></pre></div><p>如果&lt;&gt;中什么都不传入，则编译器会发出警告，提示使用原始类型，这是不推荐的做法。使用原始类型的主要问题是类型安全性降低，容易引发<code>ClassCastException</code>等运行时错误。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Box rawBox = new Box(); // 使用原始类型（不推荐）
+</span></span><span class="line"><span class="cl">rawBox.setValue(&#34;Hello&#34;);
+</span></span><span class="line"><span class="cl">String strValue = (String) rawBox.getValue(); // 需要强制转换
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 编译时会发出警告：Box is a raw type. References to generic type Box&lt;T&gt; should be parameterized
+</span></span></code></pre></div><h2 id="泛型接口">泛型接口</h2>
+<p>泛型除了可以定义在类上，还可以定义在接口上。泛型接口允许你定义一个接口，其中的方法支持使用泛型类型参数。这样可以使得接口在实现时能够处理多种类型的数据，提高了灵活性和代码的复用性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">SomeInterface</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>实现泛型接口时可以指定具体的类型参数，也可以保留接口定义的类型参数，甚至可以不指定类型参数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SomeClass</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SomeInterface</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Doing something with: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AnotherClass</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SomeInterface</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Doing something with: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>实现泛型接口时没有确定类型参数，则默认为<code>Object</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AnotherClass</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SomeInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Doing something with: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>泛型接口可以拥有静态成员，但是这些静态成员不受类型参数的影响，属于接口本身的静态成员。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 定义一个泛型接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Generator</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">T</span><span class="w"> </span><span class="nf">generate</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态方法尝试使用类型参数 T，会导致编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printInfo</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Info: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实现泛型接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">StringGenerator</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Generator</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">generate</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Generated String&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="泛型方法">泛型方法</h2>
+<p>泛型方法是Java中一种特殊的方法，它在声明时可以使用泛型类型参数，使得方法在调用时可以接受不同类型的参数，并且能够保证类型安全。
+泛型方法是在方法声明中使用了泛型类型参数的方法。通常情况下，泛型方法的类型参数在方法返回类型之前声明。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericMethodExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型方法示例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">genericMethod</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Received: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">data</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在Java中，静态方法可以使用泛型，其声明方式与普通方法类似。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericMethodExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型方法示例：交换数组中的两个元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">swap</span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">T</span><span class="w"> </span><span class="n">temp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">temp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在静态成员中不能使用泛型类定义的类型参数，但我们可以将静态成员方法定义为一个泛型方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Test2</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态泛型方法示例：使用泛型类型参数 E</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 型类定义的类型参数 T 不能在静态方法中使用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">show</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>当一个方法需要处理多个泛型类型参数时，可以在方法签名中声明多个类型参数，并在方法体内使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MultiGenericMethodExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型方法示例：打印任意类型的数组元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printArray</span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">arr1</span><span class="p">,</span><span class="w"> </span><span class="n">U</span><span class="o">[]</span><span class="w"> </span><span class="n">arr2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;Array 1 elements: &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">elem</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">elem</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;Array 2 elements: &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">elem</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">elem</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>需要格外注意的是，Java泛型类中定义的类型参数与泛型方法中定义的类型参数是相互独立的，它们没有直接的关系。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Example</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型类中的类型参数 T</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">field</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型方法中的类型参数 U（与泛型类中的 T 无关）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method</span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">param</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">param</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>它们的命名可以不同，甚至可以具有相同的名称，但它们并不会直接相互影响或约束。为了避免混淆，如果在一个泛型类中存在泛型方法，那么两者的类型参数最好不要同名。</p>
+<h2 id="泛型通配符">泛型通配符</h2>
+<p>Java的泛型是类型安全的，即使两个类型具有继承关系，比如<code>Integer</code>是<code>Number</code>的子类，但<code>ArrayList&lt;Integer&gt;</code>并不是<code>ArrayList&lt;Number&gt;</code>的子类。
+这导致在处理不同泛型类型时，不能直接赋值或进行操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ArrayList&lt;Integer&gt; intList = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">ArrayList&lt;Number&gt; numList = intList; // 编译错误，ArrayList&lt;Integer&gt; 不是 ArrayList&lt;Number&gt; 的子类型
+</span></span></code></pre></div><p>使用泛型通配符可以解决这个问题，泛型通配符是用于解决泛型之间引用传递问题的特殊语法。
+泛型通配符通过引入<code>?</code>、<code>? extends T</code>和<code>? super T</code>这些语法，解决了泛型类型之间没有继承关系、不能直接赋值和操作以及无法处理不确定具体泛型类型等问题。</p>
+<p>泛型通配符用来表示未知类型，允许在泛型类、方法或接口中使用不确定的类型。
+它们主要有三种形式：<code>?</code>、<code>? extends ...</code>、<code>? super ...</code>，每种形式适用于不同的场景。</p>
+<ul>
+<li><code>?</code>通配符：表示任意类型，称为未限定通配符。<code>?</code>代表了任何一种数据类型，能代表任何一种数据类型的只有<code>null</code>。<code>Object</code>本身也算是一种数据类型，但却不能代表任何一种数据类型，所以<code>ArrayList&lt;Object&gt;</code>和<code>ArrayList&lt;?&gt;</code>的含义是不同的，前者类型是<code>Object</code>，也就是继承树的最高父类，而后者的类型完全是未知的，注意不要混淆。
+在使用时，可以用作泛型类型的参数，但不能实例化具体的泛型对象。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;?&gt; list = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 可以添加 null，因为 null 是任意引用类型的成员
+</span></span><span class="line"><span class="cl">list.add(null);
+</span></span><span class="line"><span class="cl">// 不能添加具体的对象，因为无法确定 list 的元素类型
+</span></span><span class="line"><span class="cl">// list.add(&#34;example&#34;); // 编译错误
+</span></span></code></pre></div></li>
+<li><code>? extends ...</code>通配符：<code>? extends T</code>表示某种具体类型的子类型（包括T自身），称为上界通配符。用于限制泛型类型的范围，可以用在方法参数、集合中的泛型类型等地方。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;? extends Number&gt; numbers = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 可以添加 null 或任何 Number 及其子类的对象
+</span></span><span class="line"><span class="cl">numbers.add(null);
+</span></span><span class="line"><span class="cl">numbers.add(new Integer(10));
+</span></span><span class="line"><span class="cl">numbers.add(new Double(3.14));
+</span></span><span class="line"><span class="cl">// 不能添加其他类型的对象，例如 String
+</span></span><span class="line"><span class="cl">// numbers.add(&#34;example&#34;); // 编译错误
+</span></span></code></pre></div></li>
+<li><code>? super ...</code>通配符：<code>? super T</code>表示某种具体类型的超类型（包括T自身），称为下界通配符。用于限制泛型类型为某个类的父类或者父类的父类等。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;? super Integer&gt; integers = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 可以添加 Integer 或其子类的对象
+</span></span><span class="line"><span class="cl">integers.add(new Integer(10));
+</span></span><span class="line"><span class="cl">integers.add(new Long(20L)); // Long 是 Integer 的父类
+</span></span><span class="line"><span class="cl">// 不能添加 Object 类型的对象
+</span></span><span class="line"><span class="cl">// integers.add(new Object()); // 编译错误
+</span></span></code></pre></div></li>
+</ul>
+<p>有一个有趣的问题，可能比较不好理解。使用了<code>ArrayList&lt;? extends Number&gt;</code>这样的通配符声明时，编译器会将此列表视为一个可以存放<code>Number</code>及其子类，如<code>Integer</code>、<code>Float</code>等对象的集合。然而这种声明方式也限制了你向这个集合中添加元素的能力。
+具体来说，你无法向使用了上界通配符<code>&lt;? extends Number&gt;</code>的列表中添加任何类型的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="n">ArrayList</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="c1">// 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Float</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">0</span><span class="p">));</span><span class="c1">// 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ArrayList&lt;? extends Number&gt;</code>表示这个列表中的元素的确是<code>Number</code>或其子类，但具体是哪一种子类是不确定的。
+在编译时，Java无法确定你尝试添加的是哪一种具体的子类<code>Integer</code>还是<code>Float</code>，因此会阻止这种可能会导致类型不匹配的操作。
+泛型的目的之一是在编译时提供类型安全性检查。使用了<code>&lt;? extends Number&gt;</code>的通配符后，编译器不能确保添加的具体子类型是安全的，因此禁止了这种操作。
+如果你需要向列表中添加元素，应该使用没有通配符的具体类型来声明列表。上界统配符最大的作用就是为了拓展方法形参中类型参数的范围。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w"> </span><span class="c1">// 正确，因为Integer是Number的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Float</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">0</span><span class="p">));</span><span class="w"> </span><span class="c1">// 正确，因为Float是Number的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>有意思的来了，使用<code>ArrayList&lt;? super Number&gt;</code>，添加<code>Object</code>类型的对象编译报错。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">super</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w"> </span><span class="c1">// 编译正确，Integer 是 Number 的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Float</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">0</span><span class="p">));</span><span class="w"> </span><span class="c1">// 编译正确，Float 是 Number 的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">());</span><span class="w"> </span><span class="c1">// 编译错误，Object 不是 Number 或其子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>其原因是，<code>ArrayList&lt;? super Number&gt;</code>的下界是<code>ArrayList&lt;Number&gt;</code>。因此，我们可以确定<code>Number</code>类及其子类的对象自然可以加入<code>ArrayList&lt;? super Number&gt;</code>集合中。
+而<code>Number</code>类的父类对象就不能加入<code>ArrayList&lt;? super Number&gt;</code>集合中了，因为不能确定<code>ArrayList&lt;? super Number&gt;</code>集合的数据类型。</p>
+<p>使用<code>extends</code>通配符,允许获取集合中的元素，因为可以确定元素至少是指定类型的子类。禁止向集合中添加任何元素，因为编译器无法确定具体的子类型，不能确保类型安全性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExtendsWildcardExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译错误：无法添加任何元素，因为编译器无法确定具体的子类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// list.add(new Integer(1));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// list.add(new Float(1.0));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 可以安全地获取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Number</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w"> </span><span class="c1">// 可以确定是 Number 类型或其子类的对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;First element: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>使用<code>super</code>通配符，允许向集合中添加元素，因为可以确定元素至少是指定类型的父类。禁止安全地从集合中读取元素，因为编译器无法确定具体的父类型，不能确保类型安全性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SuperWildcardExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">super</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 允许添加 Integer 及其子类的对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译错误：无法安全地从列表中获取元素，因为编译器无法确定具体的父类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Integer num = list.get(0);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译错误：只能存放 Integer 及其子类的对象，Object 不是 Integer 的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// list.add(new Object());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>PECS原则（Producer Extends, Consumer Super）是理解和使用Java泛型通配符的一个重要原则。这个原则帮助我们决定在使用泛型时，应该使用<code>extends</code>还是<code>super</code>通配符。
+如果我们从集合中读取元素并返回它们，即集合是生产者，我们应该使用<code>&lt;? extends T&gt;</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ProducerExtendsExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">integerList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">integerList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">integerList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">numberList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">integerList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Number</span><span class="w"> </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getFirst</span><span class="p">(</span><span class="n">numberList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;First number: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">number</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Number</span><span class="w"> </span><span class="nf">getFirst</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w"> </span><span class="c1">// 安全地读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>如果我们向集合中写入元素，即集合是消费者，我们应该使用<code>&lt;? super T&gt;</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConsumerSuperExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">numberList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">super</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">integerList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">numberList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">addNumbers</span><span class="p">(</span><span class="n">integerList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Number list: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">numberList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addNumbers</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">super</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">3</span><span class="p">));</span><span class="w"> </span><span class="c1">// 安全地写入元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">4</span><span class="p">));</span><span class="w"> </span><span class="c1">// 安全地写入元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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+    </a>
+</div>
+    <footer class="footer">
+    <div id="footer_powered_by" class="powered_by">
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+
+    <div id="footer_slogan" class="footer_slogan">
+        <span>from 2021</span>
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+<script>
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diff --git a/blog-site/public/posts/javabasics/rookie-io/index.html b/blog-site/public/posts/javabasics/rookie-io/index.html
new file mode 100644
index 00000000..eac5a584
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+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>JavaIO ｜ 脚踏实地</title>
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+    
+    <meta name="description" content="概览 IO，即in和out的缩写，也就是输入和输出，指应用程序和外部设备之间的数据传递，常见的外部设备包括文件、管道、网络连接。 从计算机结构的角度来看IO，IO就" />
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+
+
+
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+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
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+        <ul class="nav">
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%a7%88">
+                    概览
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+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b5%81%e7%9a%84%e5%88%86%e7%b1%bb">
+                    流的分类
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%be%93%e5%85%a5%e6%b5%81%e4%b8%8e%e8%be%93%e5%87%ba%e6%b5%81">
+                    输入流与输出流
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ad%97%e8%8a%82%e6%b5%81%e4%b8%8e%e5%ad%97%e7%ac%a6%e6%b5%81">
+                    字节流与字符流
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%8a%82%e7%82%b9%e6%b5%81%e4%b8%8e%e5%a4%84%e7%90%86%e6%b5%81">
+                    节点流与处理流
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ba%8f%e5%88%97%e5%8c%96">
+                    序列化
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+            
+            
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+                <a class="nav-link text-left" href="#%e5%ba%8f%e5%88%97%e5%8c%96%e4%bd%9c%e7%94%a8">
+                    序列化作用
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e5%ba%8f%e5%88%97%e5%8c%96">
+                    使用序列化
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#serializable">
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#externalizable">
+                    Externalizable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#transient">
+                    transient
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#serialversionuid">
+                    serialVersionUID
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%87%aa%e5%ae%9a%e4%b9%89%e5%ba%8f%e5%88%97%e5%8c%96%e5%92%8c%e5%8f%8d%e5%ba%8f%e5%88%97%e5%8c%96">
+                    自定义序列化和反序列化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
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+            
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+                <a class="nav-link text-left" href="#%e5%8d%95%e4%be%8b%e4%b8%8e%e5%ba%8f%e5%88%97%e5%8c%96">
+                    单例与序列化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#io%e6%a8%a1%e5%9e%8b">
+                    IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%98%bb%e5%a1%9e%e5%bc%8fio%e6%a8%a1%e5%9e%8b">
+                    阻塞式IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9d%9e%e9%98%bb%e5%a1%9eio%e6%a8%a1%e5%9e%8b">
+                    非阻塞IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#io%e5%a4%8d%e7%94%a8%e6%a8%a1%e5%9e%8b">
+                    IO复用模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bf%a1%e5%8f%b7%e9%a9%b1%e5%8a%a8io%e6%a8%a1%e5%9e%8b">
+                    信号驱动IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%82%e6%ad%a5io%e6%a8%a1%e5%9e%8b">
+                    异步IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#nio">
+                    NIO
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e6%af%94%e4%bc%a0%e7%bb%9fio">
+                    对比传统IO
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%9a%e9%81%93">
+                    通道
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%86%b2%e5%8c%ba">
+                    缓冲区
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
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+        <ul class="nav">
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%89%e6%8b%a9%e5%99%a8">
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+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e8%80%83%e6%96%87%e7%ab%a0">
+                    参考文章
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+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
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+
+</div>
+
+
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+
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+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
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+                <a href="http://localhost:1313/iblog/about/">关于</a>
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+    <div class="menu_icon">
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+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
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+            </h1>
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+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
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+                        <h2 id="post_single_title">JavaIO</h2>
+                        <span id="post_page_title_date" class="date">2021.04.09</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>IO，即<code>in</code>和<code>out</code>的缩写，也就是输入和输出，指应用程序和外部设备之间的数据传递，常见的外部设备包括文件、管道、网络连接。
+从计算机结构的角度来看IO，IO就是描述了计算机系统和外部设备之间通信的过程。</p>
+<p>传统的IO是通过流技术来处理的。<code>Java IO</code>通过数据流、序列化和文件系统提供输入和输出。
+流（<code>Stream</code>），是一个抽象的概念，是指一连串的数据（字符或字节），是以先进先出的方式发送信息的通道。
+代表任何有能力产出数据的数据源对象或者是有能力接受数据的接收端对象。流的作用就是为数据源和目的地建立一个输送通道。</p>
+<p>一般来说关于流的特性有以下几点：</p>
+<ul>
+<li>先进先出：最先写入输出流的数据最先被输入流读取到。</li>
+<li>顺序存取：可以一个接一个地往流中写入一串字节，读出时也将按写入顺序读取一串字节，不能随机访问中间的数据，<code>RandomAccessFile</code>除外。</li>
+<li>只读或只写：每个流只能是输入流或输出流的一种，不能同时具备两个功能，输入流只能进行读操作，对输出流只能进行写操作。
+在一个数据传输通道中，如果既要写入数据又要读取数据，则要分别提供两个流。</li>
+</ul>
+<h2 id="流的分类">流的分类</h2>
+<p><img alt="JavaIO流分类" src="/iblog/posts/annex/images/essays/JavaIO%E6%B5%81%E5%88%86%E7%B1%BB.png"></p>
+<p>根据数据传输特性将流抽象为各种类，方便更直观的进行数据操作。主要的分类方式有以下3种：</p>
+<ul>
+<li>按数据流的方向：分为输入流、输出流；</li>
+<li>按处理数据单位：分为字节流、字符流；</li>
+<li>按功能：分为节点流、处理流；</li>
+</ul>
+<p>看上面的几个分类可能会感觉到有些混乱，那什么时候用字节流？什么时候该用输出流呢？</p>
+<ol>
+<li>首先自己要知道是选择输入流还是输出流，这就要根据自己的情况而定，如果你想从程序写东西到别的地方，那么就选择输出流，反之用输入流。</li>
+<li>然后考虑你传输数据时，是选择使用字节流传输还是字符流，也就是每次传1个字节还是2个字节，有中文肯定就选择字符流了。</li>
+<li>前面两步就可以选出一个合适的节点流了，比如字节输入流<code>InputStream</code>，如果要在此基础上增强功能，那么就在处理流中选择一个合适的即可。</li>
+</ol>
+<h3 id="输入流与输出流">输入流与输出流</h3>
+<p>输入流和输出流是Java中用于处理字节数据的抽象类，它们提供了读取和写入数据的方法，用于处理各种数据源和目标，如文件、网络连接等。
+此输入、输出是相对于我们写的代码程序而言。</p>
+<ul>
+<li>输入流：从别的地方获取资源输入到我们的程序中；如从数据源（如文件、网络连接、内存等）读取数据；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">inputStream</span><span class="p">.</span><span class="na">read</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 处理读取的数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">inputStream</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>输出流：从我们的程序中输出到别的地方；如将一个字符串保存到本地文件中，就需要使用输出流；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">OutputStream</span><span class="w"> </span><span class="n">outputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;output.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello, World!&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">getBytes</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">outputStream</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="n">bytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">outputStream</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>输入流和输出流是Java中用于处理字节数据的基本抽象，它们提供了读取和写入数据的方法，能够处理各种数据源和目标。
+在实际应用中，根据需求选择合适的输入流或输出流的子类，并结合缓冲区等机制提高数据处理效率。</p>
+<h3 id="字节流与字符流">字节流与字符流</h3>
+<p>字节流和字符流的用法几乎完成全一样，区别在于字节流和字符流所操作的数据单元不同。字节流操作的单元是数据单元是8位的字节，而字符流操作的是数据单元为16位的字符。</p>
+<blockquote>
+<p>字符流的由来
+Java中字符是采用<code>Unicode</code>标准，一个字符是16位，即一个字符使用两个字节来表示。为此，Java中引入了处理字符的流。因为数据编码的不同，而有了对字符进行高效操作的流对象。本质其实就是基于字节流读取时，去查了指定的码表。
+在<code>Unicode</code>编码中，一个英文为一个字节，一个中文为两个字节。如果使用字节流处理中文，如果一次读写一个字符对应的字节数就不会有问题，一旦将一个字符对应的字节分裂开来，就会出现乱码了。</p>
+</blockquote>
+<p>字节流以字节为单位进行数据读写，适合处理二进制数据（如图像、音频等）和文本数据。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">inputStream</span><span class="p">.</span><span class="na">read</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 处理读取的字节数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">inputStream</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>字符流以字符为单位进行数据读写，适合处理文本数据（如文本文件、字符串等）。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Reader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileReader</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">read</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 处理读取的字符数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">reader</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>在Java中，字节流和字符流之间的转换可以通过<code>InputStreamReader</code>和<code>OutputStreamWriter</code>进行。
+这两个类分别将<code>InputStream</code>转换为<code>Reader</code>，以及将<code>OutputStream</code>转换为<code>Writer</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 字节输入流转换为字符输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ByteToCharStreamExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">FileInputStream</span><span class="w"> </span><span class="n">fileInputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;example.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">InputStreamReader</span><span class="w"> </span><span class="n">inputStreamReader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InputStreamReader</span><span class="p">(</span><span class="n">fileInputStream</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;UTF-8&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">BufferedReader</span><span class="w"> </span><span class="n">bufferedReader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="n">inputStreamReader</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">line</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">line</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bufferedReader</span><span class="p">.</span><span class="na">readLine</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">line</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 字节输出流转换为字符输出流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CharToByteStreamExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">FileOutputStream</span><span class="w"> </span><span class="n">fileOutputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;output.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">OutputStreamWriter</span><span class="w"> </span><span class="n">outputStreamWriter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">OutputStreamWriter</span><span class="p">(</span><span class="n">fileOutputStream</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;UTF-8&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">BufferedWriter</span><span class="w"> </span><span class="n">bufferedWriter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedWriter</span><span class="p">(</span><span class="n">outputStreamWriter</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">bufferedWriter</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="s">&#34;这是一个字符流到字节流的示例。&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">bufferedWriter</span><span class="p">.</span><span class="na">newLine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">bufferedWriter</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="s">&#34;Hello, world!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>字节流一般用来处理图像、视频、音频、<code>PPT、Word</code>等类型的文件。字符流一般用于处理纯文本类型的文件，如<code>txt</code>文件等，但不能处理图像视频等非文本文件。
+用一句话说就是，字节流可以处理一切文件，而字符流只能处理纯文本文件。
+字节流本身没有缓冲区，缓冲字节流相对于字节流，效率提升非常高。而字符流本身就带有缓冲区，缓冲字符流相对于字符流效率提升就不是那么大了。</p>
+<h3 id="节点流与处理流">节点流与处理流</h3>
+<p>按功能不同分为节点流、处理流：</p>
+<ul>
+<li>节点流：节点流直接连接到数据源（如文件、网络连接、内存等），负责实际的数据读写操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 文件输入节点流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 文件输出节点流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">OutputStream</span><span class="w"> </span><span class="n">outputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;output.txt&#34;</span><span class="p">);</span><span class="w"> 
+</span></span></span></code></pre></div></li>
+<li>处理流：处理流不直接操作数据源，而是通过包装在节点流上来增强其功能和处理能力。处理流的构造方法始终接受另一个流对象作为参数。
+通过多层包装，处理流形成了对节点流的封装，但实际的数据处理操作仍由底层节点流完成。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用处理流包装节点流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">BufferedReader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">InputStreamReader</span><span class="p">(</span><span class="n">inputStream</span><span class="p">));</span><span class="w"> 
+</span></span></span></code></pre></div></li>
+</ul>
+<h2 id="序列化">序列化</h2>
+<p>序列化是将对象的状态信息转换为可存储或传输的形式的过程。一个对象可以被表示为一个字节序列，该字节序列包括该对象的数据、有关对象的类型的信息和存储在对象中数据的类型。
+序列化是一种数据的持久化手段。一般广泛应用于网络传输，<code>RMI</code>和<code>RPC</code>等场景中。一般是以字节码或XML格式传输。而字节码或XML编码格式可以还原为完全相等的对象。</p>
+<p>将序列化对象写入文件之后，可以从文件中读取出来，这个相反的过程称为反序列化。</p>
+<h3 id="序列化作用">序列化作用</h3>
+<p>序列化机制允许将实现序列化的Java对象转换位字节序列，这些字节序列可以保存在磁盘上，或通过网络传输，以达到以后恢复成原来的对象。
+序列化机制使得对象可以脱离程序的运行而独立存在。</p>
+<p>对象序列化机制是Java语言内建的一种对象持久化方式，通过对象序列化，可以把对象的状态保存为字节数组，并且可以在有需要的时候将这个字节数组通过反序列化的方式再转换成对象。
+对象序列化可以很容易的在JVM中的活动对象和字节流之间进行转换。</p>
+<p>由于序列化整个过程都是Java虚拟机独立的，也就是说，在一个平台上序列化的对象可以在另一个完全不同的平台上反序列化该对象。
+在Java中，对象的序列化与反序列化被广泛应用到RMI(远程方法调用)及网络传输中。</p>
+<h3 id="使用序列化">使用序列化</h3>
+<p>使用Java对象序列化在保存对象时，会把其状态保存为一组字节，在未来再将这些字节组装成对象。
+必须注意地是，对象序列化保存的是对象的&quot;状态&quot;，即它的成员变量。所以对象序列化不会关注类中的静态变量。</p>
+<p>如果需要将某个对象保存到磁盘上或者通过网络传输，那么这个类应该实现<code>Serializable</code>接口或<code>Externalizable</code>接口。</p>
+<h4 id="serializable">Serializable</h4>
+<p>类的可序列化性是通过实现<code>java.io.Serializable</code>接口的类来启用的。没有实现此接口的类的任何状态都不会被序列化或反序列化。
+可序列化类的所有子类型本身都是可序列化的。序列化接口没有方法或字段，只用于标识可序列化的语义。</p>
+<p>为了允许非序列化类的子类型被序列化，子类型可以承担保存和恢复超类型的公共、受保护和(如果可以访问)包字段的状态的责任。
+只有当它所继承的类有一个可访问的无参数构造函数来初始化类的状态时，子类型才可以承担这种责任。如果不是这种情况，则声明一个类可序列化是错误的，该错误将在运行时检测到。</p>
+<p>当试图对一个对象进行序列化的时候，如果遇到未实现<code>Serializable</code>接口的对象。在此情况下，将抛出<code>NotSerializableException</code>，并标识非<code>serializable</code>对象的类。
+实现<code>Serializable</code>序列化反序列对象化代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//       serialUser();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;----------反序列化对象----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">unSerialUser</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">serialUser</span><span class="w"> </span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;Jane&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">));)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unSerialUser</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">User</span><span class="w"> </span><span class="n">newUser</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">User</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">newUser</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">User</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getAge</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAge</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;User{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, age=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Serializable</code>明明就是一个空的接口，它是怎么保证只有实现了该接口的方法才能进行序列化与反序列化的呢？
+对象的序列化过程是通过<code>ObjectOutputStream</code>和<code>ObjectInputputStream</code>来实现的。在<code>ObjectOutputStream</code>中<code>writeObject</code>的调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(&#34;stringlist&#34;));
+</span></span><span class="line"><span class="cl">objectOutputStream.writeObject(stringList);
+</span></span><span class="line"><span class="cl">IOUtils.close(objectOutputStream);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">writeObject
+</span></span><span class="line"><span class="cl">    ---&gt;writeObject0
+</span></span><span class="line"><span class="cl">    ---&gt;writeOrdinaryObject
+</span></span><span class="line"><span class="cl">    ---&gt;writeSerialData
+</span></span><span class="line"><span class="cl">    ---&gt;invokeWriteObject
+</span></span></code></pre></div><p><code>writeObject0</code>方法中有这么一段代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Underlying writeObject/writeUnshared implementation.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeObject0</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">unshared</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">oldMode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bout</span><span class="p">.</span><span class="na">setBlockDataMode</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">depth</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="c1">// ... </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// remaining cases</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">obj</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeString</span><span class="p">((</span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">unshared</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">cl</span><span class="p">.</span><span class="na">isArray</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeArray</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">desc</span><span class="p">,</span><span class="w"> </span><span class="n">unshared</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">obj</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Enum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeEnum</span><span class="p">((</span><span class="n">Enum</span><span class="o">&lt;?&gt;</span><span class="p">)</span><span class="w"> </span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">desc</span><span class="p">,</span><span class="w"> </span><span class="n">unshared</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// =============================</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">obj</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Serializable</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeOrdinaryObject</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">desc</span><span class="p">,</span><span class="w"> </span><span class="n">unshared</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">extendedDebugInfo</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NotSerializableException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">cl</span><span class="p">.</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\n&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">debugInfoStack</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NotSerializableException</span><span class="p">(</span><span class="n">cl</span><span class="p">.</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// =============================</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ... </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在进行序列化操作时，会判断要被序列化的类是否是<code>String</code>、<code>Enum</code>、<code>Array</code>和<code>Serializable</code>类型，如果不是则直接抛出<code>NotSerializableException</code>。</p>
+<h4 id="externalizable">Externalizable</h4>
+<p><code>Externalizable</code>继承了<code>Serializable</code>，该接口中定义了两个抽象方法：<code>writeExternal</code>()与<code>readExternal()</code>。
+当使用<code>Externalizable</code>接口来进行序列化与反序列化的时候，需要开发人员重写<code>writeExternal()</code>与<code>readExternal()</code>。</p>
+<p>还有一点值得注意，在使用<code>Externalizable</code>进行序列化的时候，在读取对象时，会调用被序列化类的无参构造器去创建一个新的对象，然后再将被保存对象的字段的值分别填充到新对象中。
+所以在实现<code>Externalizable</code>接口的类必须要提供一个<code>public</code>的无参的构造器。如果<code>User</code>类中没有无参数的构造函数，在反序列化时会抛出异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">java.io.InvalidClassException: content.posts.rookie.User; no valid constructor
+</span></span></code></pre></div><p>实现<code>Externalizable</code>序列化反序列对象化代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//       serialUser();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;----------反序列化对象----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">unSerialUser</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">serialUser</span><span class="w"> </span><span class="p">()</span><span class="w">  </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;Jane&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// /将对象序列化到文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">));)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unSerialUser</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">User</span><span class="w"> </span><span class="n">newUser</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">User</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">newUser</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">User</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Externalizable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">User</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getAge</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAge</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;User{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, age=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeExternal</span><span class="p">(</span><span class="n">ObjectOutput</span><span class="w"> </span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">out</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">out</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">age</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">readExternal</span><span class="p">(</span><span class="n">ObjectInput</span><span class="w"> </span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="n">in</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="n">in</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="transient">transient</h4>
+<p>对于一个类中的某些字段如果不需要序列化，就需要加上<code>transient</code>关键字。
+被<code>transient</code>修饰的成员变量，在序列化的时候其值会被忽略，在被反序列化后，<code>transient</code>变量的值被设为初始值，如<code>int</code>型的是0，引用类型的是<code>null</code>。
+此时<code>name</code>字段将不会被序列化，当然如果一个变量被<code>static</code>修饰，它也不会被序列化。这是因为<code>static</code>字段属于类，而不是类的具体实例。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 该字段不会被序列化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">address</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>当你不希望某个成员变量的状态被序列化时，可以使用<code>transient</code>关键字。通常这种情况是因为该变量的状态是临时的，或者该变量包含敏感信息（如密码），不应在序列化过程中保存。</p>
+<h4 id="serialversionuid">serialVersionUID</h4>
+<p>虚拟机是否允许反序列化， 不仅取决于类路径和功能代码是否⼀致，⼀个⾮常重要的⼀点是两个类的序列化 ID 是否⼀致，即<code>serialVersionUID</code>要求⼀致。
+因为⽂件存储中的内容可能被篡改，为了保证数据的安全，在进⾏反序列化时，JVM会把传来的字节流中的<code>serialVersionUID</code>与本地相应实体类的<code>serialVersionUID</code>进⾏⽐较，如果相同就认为是⼀致的，可以进⾏反序列化。
+否则就会出现序列化版本不⼀致的异常，即<code>InvalidCastException</code>。</p>
+<p><code>Serializable</code>接口注释：</p>
+<blockquote>
+<p>If a serializable class does not explicitly declare a serialVersionUID,
+then the serialization runtime will calculate a default
+serialVersionUID value for that class based on various aspects of the class,
+as described in the Java(TM) Object Serialization Specification.
+However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID values,
+since the default serialVersionUID computation is highly sensitive to class details that may vary depending on compiler implementations,
+and can thus result in unexpectedInvalidClassExceptions during deserialization.</p>
+</blockquote>
+<p>大意：当实现<code>java.io.Serializable</code>接口的类没有显式地定义⼀个<code>serialVersionUID</code>变量时候，Java序列化机制会根据编译的Class⾃动⽣成⼀个<code>serialVersionUID</code>作序列化版本⽐较⽤，
+这种情况下，如果<code>class</code>⽂件没有发⽣变化，就算再编译多次，<code>serialVersionUID</code>也不会变化的。但是如果发⽣了变化，那么这个⽂件对应的<code>serialVersionUID</code>也就会发⽣变化。</p>
+<p>Java强烈建议用户自定义一个<code>serialVersionUID</code>，如果我们没有在类中明确的定义一个<code>serialVersionUID</code>的话，反序列化时可能会导致<code>InvalidClassException</code>这个异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;----------序列化对象----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">serialUser</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;----------反序列化对象----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">unSerialUser</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">serialUser</span><span class="w"> </span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;Jane&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">));)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unSerialUser</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">User</span><span class="w"> </span><span class="n">newUser</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">User</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">newUser</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">User</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getAge</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAge</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;User{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, age=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">java.io.InvalidClassException: com.test.User; local class incompatible: stream classdesc serialVersionUID = -2986778152837257883, local class serialVersionUID = 7961728318907695402
+</span></span></code></pre></div><p>代码调用链：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ObjectInputStream.readObject 
+</span></span><span class="line"><span class="cl">    -&gt; readObject0
+</span></span><span class="line"><span class="cl">    -&gt; readOrdinaryObject
+</span></span><span class="line"><span class="cl">    -&gt; readClassDesc
+</span></span><span class="line"><span class="cl">    -&gt; readNonProxyDesc
+</span></span><span class="line"><span class="cl">    -&gt; ObjectStreamClass.initNonProxy
+</span></span></code></pre></div><p>在<code>initNonProxy</code>中 ，关键代码如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">initNonProxy</span><span class="p">(</span><span class="n">ObjectStreamClass</span><span class="w"> </span><span class="n">model</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                  </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">cl</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                  </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">resolveEx</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                  </span><span class="n">ObjectStreamClass</span><span class="w"> </span><span class="n">superDesc</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">throws</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">long</span><span class="w"> </span><span class="n">suid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Long</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">getSerialVersionUID</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ObjectStreamClass</span><span class="w"> </span><span class="n">osc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">cl</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">osc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lookup</span><span class="p">(</span><span class="n">cl</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">osc</span><span class="p">.</span><span class="na">isProxy</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;cannot bind non-proxy descriptor to a proxy class&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">isEnum</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">osc</span><span class="p">.</span><span class="na">isEnum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">isEnum</span><span class="w"> </span><span class="o">?</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;cannot bind enum descriptor to a non-enum class&#34;</span><span class="w"> </span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;cannot bind non-enum descriptor to an enum class&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ========== 判断反序列化 serializableUID 是否一致 ========== start//</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">serializable</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">osc</span><span class="p">.</span><span class="na">serializable</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">!</span><span class="n">cl</span><span class="p">.</span><span class="na">isArray</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">suid</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">osc</span><span class="p">.</span><span class="na">getSerialVersionUID</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="n">osc</span><span class="p">.</span><span class="na">name</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;local class incompatible: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="s">&#34;stream classdesc serialVersionUID = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">suid</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="s">&#34;, local class serialVersionUID = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">osc</span><span class="p">.</span><span class="na">getSerialVersionUID</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ========== 判断反序列化 serializableUID 是否一致 ========== end//</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 在反序列化过程中，对serialVersionUID做了比较，如果发现不相等，则直接抛出异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">classNamesEqual</span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">name</span><span class="p">,</span><span class="w"> </span><span class="n">osc</span><span class="p">.</span><span class="na">name</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="n">osc</span><span class="p">.</span><span class="na">name</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;local class name incompatible with stream class &#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="s">&#34;name \&#34;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">model</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>其中<code>getSerialVersionUID</code>方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="nf">getSerialVersionUID</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// REMIND: synchronize instead of relying on volatile?</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">suid</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">suid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">AccessController</span><span class="p">.</span><span class="na">doPrivileged</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">PrivilegedAction</span><span class="o">&lt;</span><span class="n">Long</span><span class="o">&gt;</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kd">public</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 生成一个默认的serialVersionUID</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">return</span><span class="w"> </span><span class="n">computeDefaultSUID</span><span class="p">(</span><span class="n">cl</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">suid</span><span class="p">.</span><span class="na">longValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这也就是报错的原因，在没有定义<code>serialVersionUID</code>的时候，会调用<code>computeDefaultSUID</code>方法，生成一个默认的<code>serialVersionUID</code>。
+所以如果一个类实现了<code>Serializable</code>接口，一定要记得定义<code>serialVersionUID</code>，否则会发生异常。<code>serialVersionUID</code>有两种显示的生成方式：</p>
+<ul>
+<li>默认的<code>1L</code>，比如：<code>private static final long serialVersionUID = 1L; </code></li>
+<li>根据类名、接口名、成员方法及属性等来生成一个64位的哈希字段，比如：<code>private static final  long   serialVersionUID = xxxxL;</code></li>
+</ul>
+<p>可通过编译器进行设置，让它帮忙提示：
+<img alt="idea检查serialVersionUID" src="/iblog/posts/annex/images/essays/idea%E6%A3%80%E6%9F%A5serialVersionUID.png"></p>
+<p><img alt="idea自动生成serialVersionUID" src="/iblog/posts/annex/images/essays/idea%E8%87%AA%E5%8A%A8%E7%94%9F%E6%88%90serialVersionUID.png"></p>
+<h3 id="自定义序列化和反序列化">自定义序列化和反序列化</h3>
+<p>想要实现自定义序列化和反序列化，可以在被序列化的类中增加<code>writeObject</code>和<code>readObject</code>方法来实现。
+举个例子，看一下<code>java.util.ArrayList</code>中的是如何自定义序列化的：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">implements</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">RandomAccess</span><span class="p">,</span><span class="w"> </span><span class="n">Cloneable</span><span class="p">,</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">Serializable</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">serialVersionUID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">8683452581122892189L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">transient</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elementData</span><span class="p">;</span><span class="w"> </span><span class="c1">// non-private to simplify nested class access</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ArrayList</code>实现了<code>java.io.Serializable</code>接口且有自定义<code>serialVersionUID</code>，那么我们就可以对它进行序列化及反序列化。
+<code>ArrayList</code>底层是通过数组实现的，其中数组<code>elementData</code>其实就是用来保存列表中的元素的。
+因为<code>elementData</code>是被<code>transient</code>修饰的，所以这个成员变量不会被序列化而保留下来。那么为什么却通过序列化和反序列化把<code>List</code>中的元素保留下来了呢？</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stringList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">stringList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">stringList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;world&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">stringList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;123&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">stringList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;init StringList&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">stringList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">objectOutputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;stringlist&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectOutputStream</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">stringList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">IOUtils</span><span class="p">.</span><span class="na">close</span><span class="p">(</span><span class="n">objectOutputStream</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">&#34;stringlist&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">objectInputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newStringList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">)</span><span class="n">objectInputStream</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">IOUtils</span><span class="p">.</span><span class="na">close</span><span class="p">(</span><span class="n">objectInputStream</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="n">file</span><span class="p">.</span><span class="na">exists</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">file</span><span class="p">.</span><span class="na">delete</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;new StringList&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">newStringList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ArrayList</code>实际上是动态数组，每次在放满以后自动增长设定的长度值，如果数组自动增长长度设为100，而实际只放了一个元素，那就会序列化99个<code>null</code>元素。
+为了保证在序列化的时候不会将这么多<code>null</code>同时进行序列化，<code>ArrayList</code>把元素数组设置为<code>transient</code>。
+为了防止一个包含大量空对象的数组被序列化优化存储，所以<code>ArrayList</code>使用<code>transient</code>来修饰<code>elementData</code>。
+但是作为一个集合，在序列化过程中还必须保证其中的元素可以被持久化下来，所以通过重写<code>writeObject</code>和<code>readObject</code>方法的方式把其中的元素保留下来。</p>
+<p>在序列化过程中，如果被序列化的类中定义了<code>writeObject</code>和<code>readObject</code>方法，虚拟机会试图调用对象类里的<code>writeObject</code>和<code>readObject</code>方法，进行用户自定义的序列化和反序列化。
+如果没有这样的方法，则默认调用是<code>ObjectOutputStream</code>的<code>defaultWriteObject</code>方法以及<code>ObjectInputStream</code>的<code>defaultReadObject</code>方法。
+用户自定义的<code>writeObject</code>和<code>readObject</code>方法可以允许用户控制序列化的过程，比如可以在序列化的过程中动态改变序列化的数值。对象的序列化过程通过<code>ObjectOutputStream</code>和<code>ObjectInputputStream</code>来实现的。</p>
+<p><code>writeObject</code>方法把<code>elementData</code>数组中的元素遍历的保存到输出流（<code>ObjectOutputStream</code>）中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeObject</span><span class="p">(</span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">ObjectOutputStream</span><span class="w"> </span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">IOException</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Write out element count, and any hidden stuff</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedModCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">modCount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">s</span><span class="p">.</span><span class="na">defaultWriteObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Write out size as capacity for behavioural compatibility with clone()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">s</span><span class="p">.</span><span class="na">writeInt</span><span class="p">(</span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Write out all elements in the proper order.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">elementData</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>readObject</code>方法从输入流（<code>ObjectInputStream</code>）中读出对象并保存赋值到 <code>elementData</code> 数组中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">readObject</span><span class="p">(</span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">ObjectInputStream</span><span class="w"> </span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">EMPTY_ELEMENTDATA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Read in size, and any hidden stuff</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">s</span><span class="p">.</span><span class="na">defaultReadObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Read in capacity</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">s</span><span class="p">.</span><span class="na">readInt</span><span class="p">();</span><span class="w"> </span><span class="c1">// ignored</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// be like clone(), allocate array based upon size not capacity</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ensureCapacityInternal</span><span class="p">(</span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elementData</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Read in all elements in the proper order.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">a</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那么在一个类中定义了<code>writeObject</code>和<code>readObject</code>方法，这两个方法是怎么被调用的呢？ 答案是会通过反射的方式调用。</p>
+<p>对象的序列化过程是通过<code>ObjectOutputStream</code>和<code>ObjectInputputStream</code>来实现的。在<code>ObjectOutputStream</code>中<code>writeObject</code>的调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(&#34;stringlist&#34;));
+</span></span><span class="line"><span class="cl">objectOutputStream.writeObject(stringList);
+</span></span><span class="line"><span class="cl">IOUtils.close(objectOutputStream);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">writeObject
+</span></span><span class="line"><span class="cl">    ---&gt;writeObject0
+</span></span><span class="line"><span class="cl">    ---&gt;writeOrdinaryObject
+</span></span><span class="line"><span class="cl">    ---&gt;writeSerialData
+</span></span><span class="line"><span class="cl">    ---&gt;invokeWriteObject
+</span></span></code></pre></div><p>其中<code>invokeWriteObject</code>方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/** class-defined writeObject method, or null if none */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">Method</span><span class="w"> </span><span class="n">writeObjectMethod</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Invokes the writeObject method of the represented serializable class.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Throws UnsupportedOperationException if this class descriptor is not
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * associated with a class, or if the class is externalizable,
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * non-serializable or does not define writeObject.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">void</span><span class="w"> </span><span class="nf">invokeWriteObject</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">out</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">UnsupportedOperationException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">requireInitialized</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">writeObjectMethod</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// ========== 调用writeObject 方法 start========== //</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeObjectMethod</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="p">{</span><span class="w"> </span><span class="n">out</span><span class="w"> </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// ========== 调用writeObject 方法 end========== //</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InvocationTargetException</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Throwable</span><span class="w"> </span><span class="n">th</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ex</span><span class="p">.</span><span class="na">getTargetException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">th</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">IOException</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="p">)</span><span class="w"> </span><span class="n">th</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">throwMiscException</span><span class="p">(</span><span class="n">th</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IllegalAccessException</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// should not occur, as access checks have been suppressed</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InternalError</span><span class="p">(</span><span class="n">ex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">UnsupportedOperationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>文档注释大意：调用表示的<code>serializable</code>类的<code>writeObject</code>方法，如果类描述符不与类相关联，或者该类是可外部化、不可序列化的，或者没有定义 <code>writeObject</code>，则抛出 <code>UnsupportedOperationException</code>。
+类定义的<code>writeObject</code>方法，如果没有则为<code>null</code>。</p>
+<p>所以基本可以确定是这个方法调用的，其中<code>writeObjectMethod.invoke(obj, new Object[]{ out });</code>是关键，而<code>writeObjectMethod</code>就是在序列化类中定义的<code>writeObject</code>方法，所以确实是通过反射的方式被调用了。</p>
+<h3 id="单例与序列化">单例与序列化</h3>
+<p>单例模式，是设计模式中最简单的一种。通过单例模式可以保证系统中一个类只有一个实例而且该实例易于外界访问，从而方便对实例个数的控制并节约系统资源。
+单例模式真的能够实现实例的唯一性吗？答案是否定的，很多人都知道使用反射可以破坏单例模式，除了反射以外，使用序列化与反序列化也同样会破坏单例。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">path</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/github/iblog/blog-site/content/posts/rookie/singleton.txt&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//Write Obj to file</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="n">path</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">Singleton</span><span class="p">.</span><span class="na">getSingleton</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//Read Obj from file</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">path</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Singleton</span><span class="w"> </span><span class="n">newInstance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Singleton</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//判断是否是同一个对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">newInstance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Singleton</span><span class="p">.</span><span class="na">getSingleton</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">serialVersionUID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">6377402142849822126L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getSingleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">MainTest</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>输出结果为<code>false</code>，结论为<code>Singleton</code>的序列化与反序列化得到的对象是一个新的对象，所以序列化破坏了<code>Singleton</code>的单例性。</p>
+<p>对象的序列化过程是通过<code>ObjectOutputStream</code>和<code>ObjectInputputStream</code>来实现的。<code>ObjectInputStream</code>中<code>readObject</code>的调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(&#34;stringlist&#34;));
+</span></span><span class="line"><span class="cl">objectOutputStream.writeObject(stringList);
+</span></span><span class="line"><span class="cl">IOUtils.close(objectOutputStream);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">readObject
+</span></span><span class="line"><span class="cl">    ---&gt; readObject0
+</span></span><span class="line"><span class="cl">    ---&gt; readOrdinary
+</span></span><span class="line"><span class="cl">    ---&gt; checkResolve
+</span></span></code></pre></div><p>其中<code>readOrdinaryObject</code> 方法，文档注释大意：读取并返回&quot;ordinary&quot;(即，不是字符串、类、<code>ObjectStreamClass</code>、数组或枚举常量)对象，如果对象的类是不可解析的，则为<code>null</code>(在这种情况下，<code>ClassNotFoundException</code>将与对象的句柄相关联)。设置<code>passHandle</code>为对象的赋值句柄。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Reads and returns &#34;ordinary&#34; (i.e., not a String, Class,
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * ObjectStreamClass, array, or enum constant) object, or null if object&#39;s
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * class is unresolvable (in which case a ClassNotFoundException will be
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * associated with object&#39;s handle).  Sets passHandle to object&#39;s assigned
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * handle.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">readOrdinaryObject</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">unshared</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// `desc.isInstantiable()`: 如果一个 `serializable/externalizable` 的类可以在运行时被实例化，那么该方法就返回true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// `desc.newInstance`：该方法通过反射的方式调用无参构造方法新建一个对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">desc</span><span class="p">.</span><span class="na">isInstantiable</span><span class="p">()</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">desc</span><span class="p">.</span><span class="na">newInstance</span><span class="p">()</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="p">)</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">desc</span><span class="p">.</span><span class="na">forClass</span><span class="p">().</span><span class="na">getName</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;unable to create instance&#34;</span><span class="p">).</span><span class="na">initCause</span><span class="p">(</span><span class="n">ex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// hasReadResolveMethod:如果实现了serializable 或者 externalizable接口的类中包含readResolve则返回true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">obj</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">handles</span><span class="p">.</span><span class="na">lookupException</span><span class="p">(</span><span class="n">passHandle</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">desc</span><span class="p">.</span><span class="na">hasReadResolveMethod</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// invokeReadResolve:通过反射的方式调用要被反序列化的类的readResolve方法。</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Object</span><span class="w"> </span><span class="n">rep</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">desc</span><span class="p">.</span><span class="na">invokeReadResolve</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">unshared</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">rep</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">isArray</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">rep</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cloneArray</span><span class="p">(</span><span class="n">rep</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">obj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>desc.isInstantiable</code>方法作用是，如果一个<code>serializable</code>/<code>externalizable</code>的类可以在运行时被实例化，那么该方法就返回<code>true</code>。
+如果返回<code>true</code>，就会触发<code>desc.newInstance</code>方法执行，该方法通过反射的方式调用无参构造方法新建一个对象。
+所以序列化破坏单例的原因是调用了<code>desc.newInstance</code>方法，从而序列化会通过反射调用无参数的构造方法创建一个新的对象。</p>
+<p>原因清楚了之后，那怎么解决呢？继续向下看<code>readOrdinaryObject</code>方法代码。
+<code>hasReadResolveMethod</code>方法的作用，如果实现了<code>serializable</code>或者<code>externalizable</code>接口的类中包含<code>readResolve</code>则返回<code>true</code>。
+<code>invokeReadResolve</code>是通过反射的方式调用要被反序列化的类的<code>readResolve</code>方法。
+所以在<code>Singleton</code>中定义<code>readResolve</code>方法，并在该方法中指定要返回的对象的生成策略，就可以防止单例被破坏。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">serialVersionUID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">6377402142849822126L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getSingleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">MainTest</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">readResolve</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="io模型">IO模型</h2>
+<p>在Unix操作系统中，常见的IO模型有以下五种：阻塞IO、非阻塞IO、信号驱动IO、IO多路转接、异步IO。其中，前四个被称为同步IO。</p>
+<h3 id="阻塞式io模型">阻塞式IO模型</h3>
+<p>BIO（<code>Blocking IO</code>），最传统的一种IO模型，即在读写数据过程中会发生阻塞现象。</p>
+<p>当用户线程发出IO请求之后，内核会去查看数据是否就绪，如果没有就绪就会等待数据就绪，而用户线程就会处于阻塞状态，用户线程交出CPU。
+当数据就绪之后，内核会将数据拷贝到用户线程，并返回结果给用户线程，用户线程才解除<code>block</code>状态。</p>
+<p>BIO编程简单，易于理解和实现，但因为一个请求IO会阻塞进程，不能充分利用CPU，导致低效的资源使用，特别是在处理大量连接时。
+所以不适用并发量大的应用，适用并发量小的网络应用开发。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try (Socket socket = new Socket(&#34;example.com&#34;, 80);
+</span></span><span class="line"><span class="cl">     InputStream input = socket.getInputStream();
+</span></span><span class="line"><span class="cl">     OutputStream output = socket.getOutputStream()) {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    output.write(&#34;GET / HTTP/1.1\r\n\r\n&#34;.getBytes());
+</span></span><span class="line"><span class="cl">    int data;
+</span></span><span class="line"><span class="cl">    while ((data = input.read()) != -1) {
+</span></span><span class="line"><span class="cl">        System.out.print((char) data);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">} catch (IOException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="非阻塞io模型">非阻塞IO模型</h3>
+<p>NIO（<code>NoBlocking IO</code>），当用户线程发起一个<code>read</code>操作后，并不需要等待，而是马上就得到了一个结果。
+如果结果是一个<code>error</code>时，它就知道数据还没有准备好，于是它可以再次发送<code>read</code>操作。
+一旦内核中的数据准备好了，并且又再次收到了用户线程的请求，那么它马上就将数据拷贝到了用户线程然后返回。</p>
+<p>在NIO中，IO操作立即返回，不会阻塞线程，所以线程可以在数据未准备好时执行其他任务。
+用户线程需要不断地询问内核数据是否就绪，也就说非阻塞IO不会交出CPU，而会一直占用CPU。</p>
+<p>NIO虽然线程不会被IO操作阻塞，可以同时处理多个连接，但编程复杂度较高，需要处理非阻塞逻辑和轮询。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try (SocketChannel socketChannel = SocketChannel.open()) {
+</span></span><span class="line"><span class="cl">    socketChannel.configureBlocking(false);
+</span></span><span class="line"><span class="cl">    socketChannel.connect(new InetSocketAddress(&#34;example.com&#34;, 80));
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    while (!socketChannel.finishConnect()) {
+</span></span><span class="line"><span class="cl">        // 做其他事情
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    ByteBuffer buffer = ByteBuffer.allocate(1024);
+</span></span><span class="line"><span class="cl">    int bytesRead = socketChannel.read(buffer);
+</span></span><span class="line"><span class="cl">} catch (IOException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>需要注意的是<code>Java NIO</code>不是IO模型中的NIO模型，而是IO多路复用模型。</p>
+<h3 id="io复用模型">IO复用模型</h3>
+<p>IO复用模型，一个线程不断去轮询多个<code>socket</code>的状态，只有当<code>socket</code>真正有读写事件时，才真正调用实际的IO读写操作。
+在多路复用IO模型中，只需要使用一个线程就可以管理多个<code>socket</code>，系统不需要建立新的进程或者线程，也不必维护这些线程和进程，并且只有在真正有<code>socket</code>读写事件进行时，才会使用IO资源，所以它大大减少了资源占用。</p>
+<p><code>Java NIO</code>实际上就是多路复用IO，通过<code>selector.select()</code>查询每个通道是否有到达事件，如果没有事件则一直阻塞在那里。
+因此这种方式会导致用户线程的阻塞，所以多路复用IO比较适合连接数比较多的情况。</p>
+<p><img alt="IO多路复用模型" src="/iblog/posts/annex/images/essays/IO%E5%A4%9A%E8%B7%AF%E5%A4%8D%E7%94%A8%E6%A8%A1%E5%9E%8B.png"></p>
+<p>单线程可以处理多个通道，提高资源利用率，性能好。适用高并发服务应用开发，一个进程响应多个请求，但编程复杂度较高，需要处理选择器和事件。
+常用的实现方式包括<code>select</code>、<code>poll</code>和<code>epoll</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try (Selector selector = Selector.open();
+</span></span><span class="line"><span class="cl">     ServerSocketChannel serverChannel = ServerSocketChannel.open()) {
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    serverChannel.bind(new InetSocketAddress(8080));
+</span></span><span class="line"><span class="cl">    serverChannel.configureBlocking(false);
+</span></span><span class="line"><span class="cl">    serverChannel.register(selector, SelectionKey.OP_ACCEPT);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    while (true) {
+</span></span><span class="line"><span class="cl">        selector.select();
+</span></span><span class="line"><span class="cl">        Set&lt;SelectionKey&gt; selectedKeys = selector.selectedKeys();
+</span></span><span class="line"><span class="cl">        Iterator&lt;SelectionKey&gt; iter = selectedKeys.iterator();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        while (iter.hasNext()) {
+</span></span><span class="line"><span class="cl">            SelectionKey key = iter.next();
+</span></span><span class="line"><span class="cl">            if (key.isAcceptable()) {
+</span></span><span class="line"><span class="cl">                // 处理接受事件
+</span></span><span class="line"><span class="cl">            } else if (key.isReadable()) {
+</span></span><span class="line"><span class="cl">                // 处理读取事件
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            iter.remove();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">} catch (IOException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><blockquote>
+<p>多路复用IO为何比非阻塞IO模型的效率高？
+因为在非阻塞IO中，不断地询问<code>socket</code>状态是通过用户线程去进行的，而在多路复用IO中，轮询每个<code>socket</code>状态是内核在进行的，这个效率要比用户线程要高的多。</p>
+</blockquote>
+<p>要注意的是，多路复用IO模型是通过轮询的方式来检测是否有事件到达，并且对到达的事件逐一进行响应。
+因此对于多路复用IO模型来说，一旦事件响应体很大，那么就会导致后续的事件迟迟得不到处理，并且会影响新的事件轮询。</p>
+<h3 id="信号驱动io模型">信号驱动IO模型</h3>
+<p>当用户线程发起一个IO请求操作，会给对应的<code>socket</code>注册一个信号函数，然后用户线程会继续执行不阻塞，当内核数据就绪时会发送一个信号给用户线程，用户线程接收到信号之后，便在信号函数中调用IO读写操作来进行实际的IO请求操作。</p>
+<p>在Java中，信号驱动IO模型不常见，更多用于<code>Unix/Linux</code>系统编程，通过<code>sigaction</code>和<code>SIGIO</code>信号实现。
+虽然信号驱动IO不需要轮询，避免了CPU资源浪费，但是编程复杂，依赖于操作系统的信号机制，且跨平台支持较差，开发中使用较少。</p>
+<h3 id="异步io模型">异步IO模型</h3>
+<p>AIO（<code>Async IO</code>）模型是比较理想的IO模型，当用户线程发起IO操作后，立刻就可以开始去做其它的事。
+从内核的角度看，当它收到一个IO请求之后，它会立刻返回给用户线程，说明IO请求已经成功发起了，因此不会对用户线程产生任何阻塞。
+然后，内核会等待数据准备完成，然后将数据拷贝到用户线程，当这一切都完成之后，内核会给用户线程发送一个信号，告诉它IO操作完成了。</p>
+<p>用户线程完全不需要知道实际的整个IO操作是如何进行的，只需要先发起一个请求，当接收内核返回的成功信号时表示IO操作已经完成，可以直接去使用数据了。</p>
+<p>在异步IO模型中，IO操作的两个阶段都不会阻塞用户线程，这两个阶段都是由内核自动完成，然后发送一个信号告知用户线程操作已完成。
+用户线程中不需要再次调用IO函数进行具体的读写。这点是和信号驱动模型有所不同的，在信号驱动模型中，当用户线程接收到信号表示数据已经就绪，然后需要用户线程调用IO函数进行实际的读写操作；
+而在异步IO模型中，收到信号表示IO操作已经完成，不需要再在用户线程中调用IO函数进行实际的读写操作。</p>
+<p>AIO不会阻塞线程，适用于高并发和低延迟的应用场景，但编程复杂度较高，需要处理异步操作和回调。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try (AsynchronousSocketChannel client = AsynchronousSocketChannel.open()) {
+</span></span><span class="line"><span class="cl">    Future&lt;Void&gt; connectFuture = client.connect(new InetSocketAddress(&#34;example.com&#34;, 80));
+</span></span><span class="line"><span class="cl">    connectFuture.get();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    ByteBuffer buffer = ByteBuffer.allocate(1024);
+</span></span><span class="line"><span class="cl">    Future&lt;Integer&gt; readFuture = client.read(buffer);
+</span></span><span class="line"><span class="cl">    readFuture.get();
+</span></span><span class="line"><span class="cl">} catch (IOException | InterruptedException | ExecutionException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h2 id="nio">NIO</h2>
+<p>NIO解释为<code>New IO</code>或<code>Non Blocking IO</code>是从Java 1.4 版本开始引入的一个新的IO API，可以替代标准的<code>Java IO</code>API。
+NIO支持面向缓冲区的、基于通道的IO操作，所以NIO将以更加高效的方式进行文件的读写操作。</p>
+<p>Java中的NIO是一个非常重要的部分，尤其是在处理高性能、高并发的应用时。NIO提供了一种比传统的阻塞IO更高效的方式来处理IO操作。
+<code>Java NIO</code>属于IO多路复用模型，只不过<code>Java NIO</code>组件提供了统一的应用开发API，屏蔽了底层的操作系统的差异。<code>Java NIO</code>类库包含以下三个核心组件：</p>
+<ul>
+<li>Channel（通道）</li>
+<li>Buffer（缓冲区）</li>
+<li>Selector（选择器）</li>
+</ul>
+<h3 id="对比传统io">对比传统IO</h3>
+<table>
+<thead>
+<tr>
+<th>区别</th>
+<th>传统IO</th>
+<th>NIO</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>传输方式</td>
+<td>面向流，通过流传输</td>
+<td>面向缓冲区，通过缓冲区传输</td>
+</tr>
+<tr>
+<td>是否阻塞</td>
+<td>阻塞IO</td>
+<td>非阻塞IO</td>
+</tr>
+<tr>
+<td>其他</td>
+<td>无</td>
+<td>选择器，可以解决阻塞问题</td>
+</tr>
+</tbody>
+</table>
+<p>什么是面向流？什么是面向缓冲区呢？
+在传统IO操作中，IO的<code>read</code>操作总是以流式的方式顺序地从一个流中读取一个或多个字节，因此，我们不能随意地改变读取指针的位置，也不能前后移动流中的数据。
+而NIO中引入了<code>Channel</code>（通道）和<code>Buffer</code>（缓冲区）的概念。面向缓冲区的读取和写入，都是与<code>Buffer</code>进行交互。
+用户程序只需要从通道中读取数据到缓冲区中，或将数据从缓冲区中写入到通道中。NIO不像OIO那样是顺序操作，可以随意地读取<code>Buffer</code>中任意位置的数据，可以随意修改<code>Buffer</code>中任意位置的数据。</p>
+<p>传统IO的操作是堵塞的，当一个线程调用<code>read()</code>或<code>write()</code>时，该线程被阻塞，直到有一些数据被读取，或数据完全写入，该线程在此期间不能再干任何事情了。
+NIO如何做到非阻塞的呢？当调用<code>read</code>方法时，系统底层已经把数据准备好了，应用程序只需要从通道把数据复制到<code>Buffer</code>（缓冲区）就行。
+如果没有数据，当前线程可以去干别的事情，不需要进行阻塞等待。根本原因是NIO使用了通道和通道的IO多路复用技术。</p>
+<h3 id="通道">通道</h3>
+<p>通道(<code>Channel</code>)用于源节点与目标节点的连接，在<code>Java NIO</code>中负责缓冲区中数据的传输。<code>Channel</code>本身不存储数据，需要配合缓冲区进行数据传输。
+<code>Channel</code>的角色和传统IO中的<code>Stream</code>是差不多的。在NIO中，一个网络连接使用一个通道表示，所有的NIO的IO操作都是通过连接通道完成的。
+一个通道类似于传统IO中的两个流的结合体，既可以从通道读取数据，也可以向通道写入数据。</p>
+<p><img alt="IO" src="/iblog/posts/annex/images/essays/IO%E4%B8%8ENIO-1.png"></p>
+<p><img alt="NIO" src="/iblog/posts/annex/images/essays/IO%E4%B8%8ENIO-2.png"></p>
+<p>通道的主要实现类：</p>
+<ul>
+<li><code>FileChannel</code>：用于读取、写入、映射和操作文件的通道。</li>
+<li><code>SocketChannel</code>：通过TCP读写网络中的数据。</li>
+<li><code>ServerSocketChannel</code>：可以监听新进来的TCP连接，对每一个新进来的连接都会创建一个<code>SocketChannel</code>。</li>
+<li><code>DatagramChannel</code>：通过UDP读写网络中的数据通道。</li>
+</ul>
+<p>Java针对支持通道的类提供了<code>getChannel()</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 使用非直接缓冲区完成读写操作
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param args args
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 获取通道</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">FileChannel</span><span class="w"> </span><span class="n">inChannel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;1.jpg&#34;</span><span class="p">).</span><span class="na">getChannel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">FileChannel</span><span class="w"> </span><span class="n">outChannel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;2.jpg&#34;</span><span class="p">).</span><span class="na">getChannel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 分配指定大小的缓冲区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ByteBuffer</span><span class="p">.</span><span class="na">allocate</span><span class="p">(</span><span class="n">1024</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将通道中的数据存入缓冲区中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">inChannel</span><span class="p">.</span><span class="na">read</span><span class="p">(</span><span class="n">buf</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 切换读取数据的模式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">buf</span><span class="p">.</span><span class="na">flip</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将缓冲区中的数据写入通道中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">outChannel</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="n">buf</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 清空缓冲区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">buf</span><span class="p">.</span><span class="na">clear</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">long</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;耗费的时间为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">end</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">start</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="缓冲区">缓冲区</h3>
+<p>通道负责传输，缓冲区负责存储，缓冲区底层实现是数组，用于存储不同类型的数据。
+若需要使用NIO，需要获取用于连接IO设备的通道以及用于容纳数据的缓冲区，然后操作缓冲区，对数据进行处理。</p>
+<p><code>Channel</code>提供从文件、网络读取数据的渠道，但是读写的数据都必须经过Buffer。
+所谓通道的读取，就是将数据从通道读取到缓冲区中；所谓通道的写入，就是将数据从缓冲区中写入到通道中。缓冲区的使用，是面向流进行读写操作的OIO所没有的，也是NIO非阻塞的重要前提和基础之一。</p>
+<p>根据数据类型的不同(<code>boolean</code>除外)，有以下<code>Buffer</code>常用子类：</p>
+<ul>
+<li><code>ByteBuffer</code>：用于存储字节数据</li>
+<li><code>CharBuffer</code>：用于存储字符数据</li>
+<li><code>ShortBuffer</code>：用于存储短整型数据</li>
+<li><code>IntBuffer</code>：用于存储整型数据</li>
+<li><code>LongBuffer</code>：用于存储长整型数据</li>
+<li><code>FloatBuffer</code>：用于存储浮点型数据</li>
+<li><code>DoubleBuffer</code>：用于存储双精度浮点型数据</li>
+</ul>
+<p>在父类抽象类<code>Buffer</code>中存在四个核心属性：</p>
+<ul>
+<li><code>capacity</code>：容量，表示缓冲区中最大存储数据的容量，一旦声明不能改变。一旦写入的对象数量超过了<code>capacity</code>容量，缓冲区就满了，不能再写入了。</li>
+<li><code>limit</code>：界限，表示缓冲区中可以写入或者读取的最大上限，<code>limit</code>后数据不能进行读写。</li>
+<li><code>position</code>：位置，表示缓冲区中正在操作数据的位置。</li>
+<li><code>mark</code>：标记，用于暂存<code>position</code>的值，可以通过<code>reset()</code>恢复到<code>mark</code>的位置。</li>
+</ul>
+<p>当向缓冲区写入数据时，缓冲区处于写模式。在写模式下，数据写入缓冲区，并更新位置属性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ByteBuffer buffer = ByteBuffer.allocate(10);
+</span></span><span class="line"><span class="cl">buffer.put((byte) 1);
+</span></span><span class="line"><span class="cl">buffer.put((byte) 2);
+</span></span><span class="line"><span class="cl">buffer.put((byte) 3);
+</span></span><span class="line"><span class="cl">// 此时，位置 position = 3，容量 capacity = 10，限制 limit = 10
+</span></span></code></pre></div><p>在读数据之前，需要调用<code>flip()</code>方法将缓冲区从写模式切换到读模式。<code>flip()</code>方法将限制设置为当前位置，然后将位置重置为零。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">buffer.flip();
+</span></span><span class="line"><span class="cl">// 此时，位置 position = 0，限制 limit = 3，容量 capacity = 10
+</span></span></code></pre></div><p>在读模式下，可以从缓冲区读取数据。每次读取操作都会更新位置属性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">while (buffer.hasRemaining()) {
+</span></span><span class="line"><span class="cl">    // 输出：1, 2, 3
+</span></span><span class="line"><span class="cl">    System.out.println(buffer.get());
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>读完数据后，可以调用<code>clear()</code>方法将位置重置为零，限制设置为容量，用于准备再次写入整个缓冲区的数据。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">buffer.clear();
+</span></span><span class="line"><span class="cl">// 此时，位置 position = 0，限制 limit = 10，容量 capacity = 10
+</span></span></code></pre></div><p><code>compact()</code>方法将未读的数据复制到缓冲区的开始位置，然后将位置设置为未读数据的数量。适用于继续写入缓冲区但保留未读数据的情况。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">buffer.compact();
+</span></span><span class="line"><span class="cl">// 此时，未读的数据被移到缓冲区的开始位置，位置 position 设置为未读数据的数量
+</span></span></code></pre></div><p>完整代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BufferExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个容量为10的ByteBuffer</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ByteBuffer</span><span class="p">.</span><span class="na">allocate</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 写入数据到缓冲区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 写入数据后的缓冲区状态:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 位置 (Position): 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 限制 (Limit): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 容量 (Capacity): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;写入数据后的缓冲区状态:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printBufferStatus</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 翻转缓冲区，准备读取</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">flip</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 翻转缓冲区后的状态:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 位置 (Position): 0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 限制 (Limit): 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 容量 (Capacity): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;翻转缓冲区后的状态:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printBufferStatus</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;读取数据:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">buffer</span><span class="p">.</span><span class="na">hasRemaining</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">buffer</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取数据后的缓冲区状态:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 位置 (Position): 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 限制 (Limit): 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 容量 (Capacity): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;读取数据后的缓冲区状态:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printBufferStatus</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 清空缓冲区，准备再次写入</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">clear</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 清空缓冲区后的状态:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 位置 (Position): 0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 限制 (Limit): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 容量 (Capacity): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;清空缓冲区后的状态:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printBufferStatus</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printBufferStatus</span><span class="p">(</span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;位置 (Position): &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">position</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;限制 (Limit): &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">limit</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;容量 (Capacity): &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">capacity</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>mark</code>方法，记录当前<code>position</code>位置，可以通过<code>reset()</code>恢复到<code>mark</code>的位置。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BufferMarkResetExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个容量为10的ByteBuffer</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ByteBuffer</span><span class="p">.</span><span class="na">allocate</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 写入数据到缓冲区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 标记当前位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">mark</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;标记位置 (Position)：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">position</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 继续写入数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前缓冲区位置 (Position)：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">position</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 调用reset()方法恢复到标记的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">reset</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;重置后的位置 (Position)：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">position</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 从标记的位置继续写入数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 翻转缓冲区，准备读取</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">flip</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;读取数据：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">buffer</span><span class="p">.</span><span class="na">hasRemaining</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">buffer</span><span class="p">.</span><span class="na">get</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="选择器">选择器</h3>
+<p>选择器是<code>Java NIO</code>中的一个核心组件，允许单个线程管理多个通道（<code>Channel</code>）。它可以监控多个通道的IO事件，例如数据是否准备好读取、是否可以写入等。
+通过选择器，应用程序可以在一个线程中同时管理多个通道的IO操作，而不必为每个通道创建一个单独的线程，这样可以提高系统资源利用率和应用程序的性能。</p>
+<blockquote>
+<p>什么是IO事件呢？
+表示通道某种IO操作已经就绪、或者说已经做好了准备。例如，如果一个新<code>Channel</code>链接建立成功了，就会在<code>Server Socket Channel</code>上发生一个IO事件，代表一个新连接一个准备好，这个IO事件叫做“接收就绪”事件。</p>
+</blockquote>
+<p><code>Selector</code>的本质，就是去查询这些IO就绪事件，所以，它的名称就叫做<code>Selector</code>查询者。
+从编程实现维度来说，IO多路复用编程的第一步，是把通道注册到选择器中，第二步则是通过选择器所提供的事件查询方法，这些注册的通道是否有已经就绪的IO事件。</p>
+<p>与传统IO相比，NIO使用选择器的最大优势就是系统开销小，系统不必为每一个网络连接创建进程/线程。
+通过<code>Java NIO</code>可以达到一个线程负责多个连接通道的IO处理，这是非常高效的。这种高效，恰恰就来自于Java的选择器组件<code>Selector</code>以及其底层的操作系统IO多路复用技术的支持。</p>
+<p>选择器的使命是完成IO的多路复用，其主要工作是通道的注册、监听、事件查询。
+一个通道代表一条连接通路，通过选择器可以同时监控多个通道的IO（输入输出）状况。选择器和通道的关系，是监控和被监控的关系。</p>
+<p><img alt="selector示意图" src="/iblog/posts/annex/images/essays/selector%E7%A4%BA%E6%84%8F%E5%9B%BE.png"></p>
+<p>使用选择器，首先需要通过<code>Selector.open()</code>方法创建一个选择器对象。选择器允许单个线程管理多个通道的IO操作，实现了IO多路复用的机制。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Selector selector = Selector.open();
+</span></span></code></pre></div><p>通过<code>register</code>方法将通道注册到选择器上，并指定选择器要监控的IO事件类型，可供选择器监控的通道IO事件类型，包括以下四种：</p>
+<ul>
+<li>可读：<code>SelectionKey.OP_READ</code></li>
+<li>可写：<code>SelectionKey.OP_WRITE</code></li>
+<li>连接：<code>SelectionKey.OP_CONNECT</code></li>
+<li>接收：<code>SelectionKey.OP_ACCEPT</code></li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
+</span></span><span class="line"><span class="cl">serverSocketChannel.configureBlocking(false); // 非阻塞模式
+</span></span><span class="line"><span class="cl">serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
+</span></span></code></pre></div><p>使用选择器的<code>select()</code>方法阻塞，直到至少有一个通道准备好进行IO操作，并处理每个发生的事件。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">selector.select(); // 阻塞直到有通道发生了注册的事件
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Set&lt;SelectionKey&gt; selectedKeys = selector.selectedKeys();
+</span></span><span class="line"><span class="cl">Iterator&lt;SelectionKey&gt; keyIterator = selectedKeys.iterator();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">while (keyIterator.hasNext()) {
+</span></span><span class="line"><span class="cl">    SelectionKey key = keyIterator.next();
+</span></span><span class="line"><span class="cl">    keyIterator.remove();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    if (key.isAcceptable()) {
+</span></span><span class="line"><span class="cl">        // 处理接受连接事件
+</span></span><span class="line"><span class="cl">        handleAccept(key, selector);
+</span></span><span class="line"><span class="cl">    } else if (key.isReadable()) {
+</span></span><span class="line"><span class="cl">        // 处理读事件
+</span></span><span class="line"><span class="cl">        handleRead(key);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>当有客户端连接时，我们通过服务端通道接受连接，并将客户端通道注册为读事件。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleAccept</span><span class="p">(</span><span class="n">SelectionKey</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">Selector</span><span class="w"> </span><span class="n">selector</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ServerSocketChannel</span><span class="w"> </span><span class="n">serverChannel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">ServerSocketChannel</span><span class="p">)</span><span class="w"> </span><span class="n">key</span><span class="p">.</span><span class="na">channel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SocketChannel</span><span class="w"> </span><span class="n">clientChannel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">serverChannel</span><span class="p">.</span><span class="na">accept</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">clientChannel</span><span class="p">.</span><span class="na">configureBlocking</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">clientChannel</span><span class="p">.</span><span class="na">register</span><span class="p">(</span><span class="n">selector</span><span class="p">,</span><span class="w"> </span><span class="n">SelectionKey</span><span class="p">.</span><span class="na">OP_READ</span><span class="p">);</span><span class="w"> </span><span class="c1">// 注册读事件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Accepted connection from &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">clientChannel</span><span class="p">.</span><span class="na">getRemoteAddress</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>读事件发生时，我们从通道中读取数据，并进行相应的处理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRead</span><span class="p">(</span><span class="n">SelectionKey</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SocketChannel</span><span class="w"> </span><span class="n">channel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">SocketChannel</span><span class="p">)</span><span class="w"> </span><span class="n">key</span><span class="p">.</span><span class="na">channel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ByteBuffer</span><span class="p">.</span><span class="na">allocate</span><span class="p">(</span><span class="n">1024</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">bytesRead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">channel</span><span class="p">.</span><span class="na">read</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">bytesRead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 客户端关闭连接</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">channel</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">key</span><span class="p">.</span><span class="na">cancel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Closed connection: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">channel</span><span class="p">.</span><span class="na">getRemoteAddress</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">buffer</span><span class="p">.</span><span class="na">flip</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">buffer</span><span class="p">.</span><span class="na">remaining</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">buffer</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">data</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Received: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="n">data</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">buffer</span><span class="p">.</span><span class="na">clear</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="参考文章">参考文章</h2>
+<ul>
+<li><a href="http://hollischuang.gitee.io/tobetopjavaer">http://hollischuang.gitee.io/tobetopjavaer</a></li>
+<li><a href="https://docs.oracle.com/javase/7/docs/api/java/io/Externalizable.html">https://docs.oracle.com/javase/7/docs/api/java/io/Externalizable.html</a></li>
+<li><a href="https://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html">https://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html</a></li>
+<li><a href="https://blog.csdn.net/crazymakercircle/article/details/120946903">https://blog.csdn.net/crazymakercircle/article/details/120946903</a></li>
+</ul>
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diff --git a/blog-site/public/posts/javabasics/rookie-java-container/index.html b/blog-site/public/posts/javabasics/rookie-java-container/index.html
new file mode 100644
index 00000000..a8de864a
--- /dev/null
+++ b/blog-site/public/posts/javabasics/rookie-java-container/index.html
@@ -0,0 +1,2225 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java集合 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="概述 Java中的集合主要包括Collection和Map两种，Collection存储着对象的集合，而Map存储着键值对的映射表。 数组 如果你看过ArrayLis" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
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+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
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+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%bf%b0">
+                    概述
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e7%bb%84">
+                    数组
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%98%e9%95%bf%e5%8f%82%e6%95%b0">
+                    变长参数
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9a%e4%b9%89%e6%95%b0%e7%bb%84">
+                    定义数组
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%81%8d%e5%8e%86%e6%95%b0%e7%bb%84">
+                    遍历数组
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e7%bb%84%e5%8e%bb%e9%87%8d">
+                    数组去重
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e7%bb%84%e8%bd%ac%e9%9b%86%e5%90%88">
+                    数组转集合
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#arraylist">
+                    ArrayList
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#randomaccess">
+                    RandomAccess
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cloneable">
+                    Cloneable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#arraylist%e6%89%a9%e5%ae%b9">
+                    ArrayList扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#arraylist%e4%b8%8elinkedlist">
+                    ArrayList与LinkedList
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#arraylist%e5%ae%89%e5%85%a8%e5%88%a0%e9%99%a4">
+                    ArrayList安全删除
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashset">
+                    HashSet
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8e%bb%e9%87%8d%e5%8e%9f%e7%90%86">
+                    去重原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#equals%e4%b8%8ehashcode">
+                    equals与hashCode
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8-1">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#queue">
+                    Queue
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap">
+                    HashMap
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e7%bb%93%e6%9e%84">
+                    HashMap结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hash%e5%86%b2%e7%aa%81">
+                    Hash冲突
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e5%ae%b9%e9%87%8f">
+                    HashMap容量
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e6%89%a9%e5%ae%b9">
+                    HashMap扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#17%e6%89%a9%e5%ae%b9">
+                    1.7扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#18%e6%89%a9%e5%ae%b9">
+                    1.8扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8-2">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
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+                        <h2 id="post_single_title">Java集合</h2>
+                        <span id="post_page_title_date" class="date">2021.10.04</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概述">概述</h2>
+<p>Java中的集合主要包括<code>Collection</code>和<code>Map</code>两种，<code>Collection</code>存储着对象的集合，而<code>Map</code>存储着键值对的映射表。</p>
+<p><img alt="Java中的集合-01" src="/iblog/posts/annex/images/essays/Java%E4%B8%AD%E7%9A%84%E9%9B%86%E5%90%88-01.jpg"></p>
+<h2 id="数组">数组</h2>
+<p>如果你看过<code>ArrayList</code>类源码，就知道<code>ArrayList</code>底层是通过数组来存储元素的，所以如果严格来说，数组也算集合的一种。
+Java中提供的数组是用来存储固定大小的同类型元素，所以Java数组就是同类数据元素的集合。
+在Java中，数组是一种非常常用的数据结构，用于存储同一类型的一组元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 定义一个整数数组
+</span></span><span class="line"><span class="cl">int[] intArray;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 初始化数组并赋值
+</span></span><span class="line"><span class="cl">intArray = new int[5]; // 数组长度为5，每个元素默认值为0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 定义并初始化数组
+</span></span><span class="line"><span class="cl">int[] anotherArray = {1, 2, 3, 4, 5}; // 定义并同时赋值
+</span></span></code></pre></div><p>数组是引用数据类型，如果使用了没有开辟空间的数组，则一定会出现<code>NullPointerException</code>异常信息。
+所以数组本质上也是Java对象，能够向下或者向上转型，能使用<code>instanceof</code>关键字。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int[] intArray; // 声明数组但未初始化
+</span></span><span class="line"><span class="cl">System.out.println(intArray[0]); // 这将导致 NullPointerException
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Object obj = new int[5]; // 向上转型
+</span></span><span class="line"><span class="cl">if (obj instanceof int[]) {
+</span></span><span class="line"><span class="cl">int[] array = (int[]) obj; // 向下转型
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Successfully casted obj to int[]&#34;);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>数组由于其连续的内存分配和高效的下标访问，具有高访问效率，但其固定大小、插入删除低效、单一类型限制和高内存要求使其在实际应用中不如集合灵活，
+所以我们应该优选集合，而不是数组。只有在已证明性能成为问题的时候，并且确定切换到数组对性能提高有帮助时，才应该将项目重构为使用数组。</p>
+<h3 id="变长参数">变长参数</h3>
+<p>在Java中，变长参数在方法定义中处理方式与数组相同。
+变长参数允许你传递任意数量的参数到一个方法中，编译时会将其处理为一个数组。例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public void methodName(int... values) {
+</span></span><span class="line"><span class="cl">    for (int value : values) {
+</span></span><span class="line"><span class="cl">        System.out.println(value);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// 在这个方法中，可以传递任意数量的整数
+</span></span><span class="line"><span class="cl">methodName(1, 2, 3); // 传递三个参数
+</span></span><span class="line"><span class="cl">methodName(4, 5); // 传递两个参数
+</span></span><span class="line"><span class="cl">methodName(); // 传递零个参数
+</span></span></code></pre></div><p>一个方法只能有一个变长参数，即使是不同类型也不行。并且变长参数必须是方法参数列表中的最后一个参数。</p>
+<h3 id="定义数组">定义数组</h3>
+<p>由于数组没有提供任何的封装，所有对元素的操作，都是通过自定义的方法实现的，对数组元素的操作比较麻烦，好在Java自带了一些API供开发者调用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="w"> </span><span class="p">};</span><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span></code></pre></div><p>需要注意的是[]，写在数组名称的前后都可以，但是推荐第一种写法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">array2</span><span class="o">[]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span></code></pre></div><h3 id="遍历数组">遍历数组</h3>
+<p>在Java中，遍历数组有多种不同的方式，每种方式适合不同的情况和需求。以下是几种常见的遍历数组的方式：</p>
+<ol>
+<li>使用普通for循环；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int[] array = {1, 2, 3, 4, 5};
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">for (int i = 0; i &lt; array.length; i++) {
+</span></span><span class="line"><span class="cl">    System.out.println(array[i]);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>使用增强for循环；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int[] array = {1, 2, 3, 4, 5};
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">for (int num : array) {
+</span></span><span class="line"><span class="cl">    System.out.println(num);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>使用Java 8的<code>Stream API</code>；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int[] array = {1, 2, 3, 4, 5};
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Arrays.stream(array).forEach(num -&gt; System.out.println(num));
+</span></span></code></pre></div></li>
+</ol>
+<h3 id="数组去重">数组去重</h3>
+<ol>
+<li>如果数组元素是对象类型（如<code>String</code>、<code>Integer</code>等），可以利用集合类的特性来进行去重。这种方法简单直接，适用于不需要保持原始顺序的情况；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayDuplicateRemoval</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用Set去重</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedHashSet</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">array</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="o">[]</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">set</span><span class="p">.</span><span class="na">toArray</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出去重后的数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">result</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>Java 8引入的<code>Stream API</code>提供了一种更加函数式和流畅的方式进行数组去重。这种方法同样适用于对象类型数组，且可以保持元素的原始顺序；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayDuplicateRemoval</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用Stream API去重</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="o">[]</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">stream</span><span class="p">(</span><span class="n">array</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                 </span><span class="p">.</span><span class="na">distinct</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                 </span><span class="p">.</span><span class="na">toArray</span><span class="p">(</span><span class="n">Integer</span><span class="o">[]</span><span class="p">::</span><span class="k">new</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出去重后的数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">result</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<h3 id="数组转集合">数组转集合</h3>
+<ol>
+<li>使用<code>Arrays.asList</code>方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayToCollection</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;A&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;B&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;D&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数组转换为List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">array</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>使用<code>Collections.addAll</code>方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayToCollection</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;A&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;B&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;D&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个空的List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数组元素添加到List中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Collections</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">list</span><span class="p">,</span><span class="w"> </span><span class="n">array</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>使用<code>Stream API</code>；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayToCollection</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;A&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;B&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;D&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数组转换为List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Stream</span><span class="p">.</span><span class="na">of</span><span class="p">(</span><span class="n">array</span><span class="p">).</span><span class="na">collect</span><span class="p">(</span><span class="n">Collectors</span><span class="p">.</span><span class="na">toList</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<h2 id="arraylist">ArrayList</h2>
+<p>在<code>List</code>接口实现类中，最常用的就是<code>ArrayList</code>，<code>ArrayList</code>类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删除元素。
+<code>ArrayList</code>继承了<code>AbstractList</code>，并实现了<code>List</code>、<code>RandomAccess</code>，<code>Cloneable</code>接口：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">RandomAccess</span><span class="p">,</span><span class="n">Cloneable</span><span class="p">,</span><span class="n">Serializable</span><span class="p">{}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="randomaccess">RandomAccess</h3>
+<p><code>Random</code>是随机的意思，<code>Access</code>是访问的意思，合起来<code>RandomAccess</code>就是随机访问的意思。
+<code>RandomAccess</code>接口是一个标记接口，用来标记实现的<code>List</code>集合具备快速随机访问的能力。
+所有的<code>List</code>实现都支持随机访问的，只是基于基本结构的不同，实现的速度不同罢了。</p>
+<p>当一个<code>List</code>拥有快速访问功能时，其遍历方法采用随机访问速度最快，而没有快速随机访问的<code>List</code>采用顺序访问的速度最快。
+如果集合中的数据量过大需要遍历时，此时需要格外注意，因为不同的遍历方式会影响很大，可以使用<code>instanceof</code>关键字来判断该类有没有<code>RandomAccess</code>标记：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 假设 list 数据量非常大,推荐写法
+</span></span><span class="line"><span class="cl">List&lt;Object&gt; list = ...;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">if(list instanceof RandomAccess){
+</span></span><span class="line"><span class="cl">    // 随机访问
+</span></span><span class="line"><span class="cl">    for (int i = 0;i&lt; list.size();i++) {
+</span></span><span class="line"><span class="cl">        System.out.println(list.get(i));
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}else {
+</span></span><span class="line"><span class="cl">    // 顺序访问
+</span></span><span class="line"><span class="cl">    for(Object obj: list) {
+</span></span><span class="line"><span class="cl">        System.out.println(obj);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在<code>List</code>中<code>ArrayList</code>被<code>RandomAccess</code>接口标记，而<code>LinkedList</code>没有被<code>RandomAccess</code>接口标记，所以<code>ArrayList</code>适合随机访问，而<code>LinkedList</code>适合顺序访问。</p>
+<h3 id="cloneable">Cloneable</h3>
+<p><code>Cloneable</code>接口是Java开发中常用的一个接口，它是一个标记接口。
+如果一个想要拷贝一个对象，就需要重写<code>Object</code>中的<code>clone</code>方法并让其实现<code>Cloneable</code>接口。如果只重写<code>clone</code>方法，不实现<code>Cloneable</code>接口就会报<code>CloneNotSupportedException</code>异常。</p>
+<p><code>clone</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>应当注意的是，<code>clone()</code>方法并不是<code>Cloneable</code>接口的方法，而是<code>Object</code>的一个<code>protected</code>方法。
+<code>Cloneable</code>接口只是规定，如果一个类没有实现<code>Cloneable</code>接口又调用了<code>clone</code>方法，就会抛出<code>CloneNotSupportedException</code>。
+换言之，<code>clone</code>方法规定了想要拷贝对象，就需要实现<code>Cloneable</code>方法，<code>clone</code>方法让<code>Cloneable</code>接口变得有意义。</p>
+<p>拷贝分为浅拷贝与深拷贝：</p>
+<ul>
+<li>浅拷贝：被复制对象的所有值属性都含有与原来对象的相同，而所有的对象引用属性仍然指向原来的对象；</li>
+<li>深拷贝：在浅拷贝的基础上，所有引用其他对象的变量也进行了<code>clone</code>，并指向被复制过的新对象；</li>
+</ul>
+<p>如果一个被复制的属性都是基本类型，那么只需要实现当前类的<code>Cloneable</code>机制就可以了，此为浅拷贝。
+如果被复制对象的属性包含其他实体类对象引用，那么这些实体类对象都需要实现<code>Cloneable</code>接口并覆盖<code>clone</code>方法。
+<code>ArrayList</code>中<code>clone</code>方法可以创建一个浅拷贝。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// ArrayList类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">transient</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elementData</span><span class="p">;</span><span class="w">     
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Returns a shallow copy of this &lt;tt&gt;ArrayList&lt;/tt&gt; instance.  (The
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * elements themselves are not copied.)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return a clone of this &lt;tt&gt;ArrayList&lt;/tt&gt; instance
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 调用Object类的clone方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ArrayList</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">ArrayList</span><span class="o">&lt;?&gt;</span><span class="p">)</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将集合中的元素进行拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="p">.</span><span class="na">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="p">.</span><span class="na">modCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">v</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// this shouldn&#39;t happen, since we are Cloneable</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InternalError</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// Arrays类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Arrays</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="nf">copyOf</span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newLength</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">copyOf</span><span class="p">(</span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="n">newLength</span><span class="p">,</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">getClass</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="p">,</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="nf">copyOf</span><span class="p">(</span><span class="n">U</span><span class="o">[]</span><span class="w"> </span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newLength</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">T</span><span class="o">[]&gt;</span><span class="w"> </span><span class="n">newType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">copy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">((</span><span class="n">Object</span><span class="p">)</span><span class="n">newType</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p">(</span><span class="n">Object</span><span class="p">)</span><span class="n">Object</span><span class="o">[]</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">?</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="o">[</span><span class="n">newLength</span><span class="o">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">Array</span><span class="p">.</span><span class="na">newInstance</span><span class="p">(</span><span class="n">newType</span><span class="p">.</span><span class="na">getComponentType</span><span class="p">(),</span><span class="w"> </span><span class="n">newLength</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">copy</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">original</span><span class="p">.</span><span class="na">length</span><span class="p">,</span><span class="w"> </span><span class="n">newLength</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">copy</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>ArrayList</code>中核心方法最终调用<code>Arrays.copyOf</code>方法，其中调用<code>Arrays.newInstance</code>方法或者创建一个新数组，<code>Arrays.newInstance</code>方法作用，是创建具有指定组件类型和长度的新数组。
+所以不论怎样都会创建一个<code>Object</code>数组。最后使用<code>System.arraycopy</code>方法将之前的旧数组中的元素拷贝到新创建的数组中，然后赋值给<code>ArrayList.elementData</code>对象并返回。</p>
+<p>如果需要深拷贝，即复制对象及其引用的所有对象，需要手动实现拷贝逻辑，通常涉及遍历列表并复制每个元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Item</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Item</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayListCopy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建并初始化一个ArrayList</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Item</span><span class="o">&gt;</span><span class="w"> </span><span class="n">originalList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;C&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 深拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Item</span><span class="o">&gt;</span><span class="w"> </span><span class="n">deepCopy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Item</span><span class="w"> </span><span class="n">item</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">originalList</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">deepCopy</span><span class="p">.</span><span class="na">add</span><span class="p">((</span><span class="n">Item</span><span class="p">)</span><span class="w"> </span><span class="n">item</span><span class="p">.</span><span class="na">clone</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 修改原始列表的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">).</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Z&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Original List: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">originalList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Deep Copy: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">deepCopy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="arraylist扩容">ArrayList扩容</h3>
+<p>因为<code>ArrayList</code>底层使用数组保存数据的，而数组一旦被创建就不能改变大小，但是<code>ArrayList</code>的长度是可以改变的，所以可以通过<code>ArrayList</code>类中的<code>add</code>方法找到数组扩容方法。
+<code>add</code>方法调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">add 
+</span></span><span class="line"><span class="cl">    -&gt; ensureCapacityInternal()
+</span></span><span class="line"><span class="cl">    -&gt; calculateCapacity()
+</span></span><span class="line"><span class="cl">    -&gt; ensureExplicitCapacity()
+</span></span><span class="line"><span class="cl">    -&gt; grow()
+</span></span></code></pre></div><p>通过<code>add</code>方法，最终找到了<code>grow</code>方法，也就是扩容的核心方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">grow</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">minCapacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// overflow-conscious code</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elementData</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">minCapacity</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">minCapacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">MAX_ARRAY_SIZE</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hugeCapacity</span><span class="p">(</span><span class="n">minCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// minCapacity is usually close to size, so this is a win:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>ArrayList</code>如果没有指定容量创建数组，默认会创建一个长度为10的数组用来保存元素，之后通过<code>grow</code>方法中的这段代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p><code>&gt;&gt;</code>右移几位就是相当于除以2的几次幂，所以每次扩容都是原容量的1.5倍。最后通过<code>Arrays.copyOf</code>方法将之前的数组中元素，全部移到新创建的数组上。</p>
+<p>由于频繁的扩容数组会对性能产生影响，如果在<code>ArrayList</code>中要存储很大的数据，需要在<code>ArrayList</code>的有参构造中指定数组的长度，来减少扩容的次数。
+需要注意的是创建指定长度的<code>ArrayList</code>，在没有<code>add</code>之前<code>ArrayList</code>中的数组已经初始化了，但是<code>List</code>的大小没变，因为<code>List</code>的大小是由<code>size</code>决定的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="p">(</span><span class="n">1000000</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><h3 id="arraylist与linkedlist">ArrayList与LinkedList</h3>
+<p><code>ArrayList</code>与<code>LinkedList</code>性能比较是一道经典的面试题，先说答案<code>ArrayList</code>查找快，增删慢，而<code>LinkedList</code>增删快，查找慢。
+造成这种原因是因为底层的数据结构不一样。<code>ArrayList</code>底层是数组，而数组的中的元素内存分配都是连续的，并且数组中的元素只能存放一种，这就造成了数组中的元素地址是有规律的，数组中查找元素快速的原因正是利用了这一特点。
+查询方式为: 首地址＋(元素类型长度*下标)。例如：<code>new int arr[5]; arr</code>数组的地址假设为<code>0x1000</code>，那么<code>arr[3]</code>地址可看作为 <code>0x1000 + (3 * 4)</code>，3为数组下标，4为int元素类型长度。</p>
+<p>而<code>LinkedList</code>在Java中的底层结构是对象，每一个对象结点中都保存了下一个结点的位置形成的链表结构，由于<code>LinkedList</code>元素的地址是不连续的，所以没办法按照数组那样去查找，所以就比较慢。</p>
+<p>由于数组一旦分配了大小就不能改变，所以<code>ArrayList</code>在进行添加操作时会创建新的数组，如果要添加到<code>ArrayList</code>中的指定的位置，是通过<code>System.arraycopy</code>方法将数组进行复制，新的数组会将待插入的指定位置空余出来，最后在将元素添加到集合中。
+在进行删除操作时是通过<code>System.arraycopy</code>方法，将待删除元素后面剩余元素复制到待删除元素的位置。当<code>ArrayList</code>里有大量数据时，这时候去频繁插入或删除元素会触发底层数组频繁拷贝，所以效率不高，还会造成内存空间的浪费。</p>
+<p><code>LinkedList</code>在进行添加，删除操作时，会用二分查找法找到将要添加或删除的元素，之后再设置对象的下一个结点来进行添加或删除操作，所以增加删除的效率高。</p>
+<blockquote>
+<p>二分查找法：也称为折半查找法，是一种适用于大量数据查找的方法，但是要求数据必须的排好序的，每次以中间的值进行比较，根据比较的结果可以直接舍去一半的值，直至全部找完（可能会找不到）或者找到数据为止。
+此处LinkedList会比较查找的元素是距离头结点比较近，还是尾结点比较近，距离哪边较近则从哪边开始查找。</p>
+</blockquote>
+<p><code>ArrayList</code>获取元素效率非常的高，时间复杂度是<code>O(1)</code>，而查找、插入和删除元素效率似乎不太高，时间复杂度为<code>O(n)</code>。
+<code>LinkedList</code>与<code>ArrayList</code>相反，获取第几个元素依次遍历复杂度<code>O(n)</code>，添加到末尾复杂度<code>O(1)</code>，添加到指定位置复杂度<code>O(n)</code>，删除元素直接指针指向操作复杂度<code>O(1)</code>。</p>
+<p>注意，<code>ArrayList</code>的增删不一定比<code>LinkedList</code>效率低，但是<code>ArrayList</code>查找效率一定比<code>LinkedList</code>高。
+如果在靠近末尾的地方插入，那么<code>ArrayList</code>只需要移动较少的数据，而<code>LinkedList</code>则需要一直查找到列表尾部，反而耗费较多时间，这时<code>ArrayList</code>就比<code>LinkedList</code>要快。</p>
+<p>所以在实际开发中，<code>ArrayList</code>适用于需要快速随机访问和较少插入删除操作的场景，而<code>LinkedList</code>适用于频繁插入删除操作和需要实现队列或双端队列的场景。</p>
+<h3 id="线程安全">线程安全</h3>
+<p>众所周知，<code>ArrayList</code>是线程不安全的，因为它不保证在多线程环境下的同步操作，当多个线程同时访问和修改同一个<code>ArrayList</code>对象时可能会导致数据不一致或抛出异常。
+多线程下抛出<code>ConcurrentModificationException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果没有报错，需要多试几次</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrayList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">arrayList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">arrayList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>出现该异常的原因是集合中的<code>fail-fast</code>机制。在查看源码的时候，发现调用<code>remove</code>方法时，会执行<code>checkForComodification</code>方法。
+若<code>modCount</code>不等于<code>expectedModCount</code>，则抛出<code>ConcurrentModificationException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkForComodification</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那为什么会抛出<code>ConcurrentModificationException</code>异常呢？
+在调用<code>add</code>方法时，会修改<code>modCount++</code>。一个线程调用<code>add</code>方法，一个线程调用<code>next</code>遍历方法，都共同读取<code>modCount</code>变量的值。
+因为是多线程操作，<code>expectedModCount</code>、<code>modCount</code>变量为公共的，所以很容易出现<code>modCount != expectedModCount</code>，所以便抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 添加元素到指定的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">element</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IndexOutOfBoundsException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;Index: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Size: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 修改modCount</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ensureCapacity</span><span class="p">(</span><span class="n">size</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">  </span><span class="c1">// Increments modCount!!</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">element</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">size</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>因此，在多线程环境中使用<code>ArrayList</code>时，需要手动同步操作，或者使用线程安全的集合类。保证<code>ArrayList</code>线程安全有以下几种方法：</p>
+<ol>
+<li>可以使用 <code>Vector</code> 来代替 <code>ArrayList</code>。<code>Vector</code>是线程安全的<code>ArrayList</code>，但是由于底层是加了<code>synchronized</code>，性能略差不推荐使用；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List list = new Vector();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+<li>使用<code>Collections.synchronizedArrayList()</code> 来创建 <code>ArrayList</code>。使用<code>Collections</code>工具类来创建<code>ArrayList</code>的思路是，在<code>ArrayList</code>的外边套了一个<code>synchronized</code>外壳，来保证<code>ArrayList</code>线程安全；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List list = Collections.synchronizedArrayList();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+<li>使用<code>CopyOnWriteArrayList()</code>来保证 <code>ArrayList</code> 线程安全。<code>CopyWriteArrayList</code>字面意思就是在写的时候复制，主要思想就是读写分离的思想。
+<code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>，所以保证了某个线程在写的时候不会被打断；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">CopyOnWriteArrayList&lt;String&gt; list = new CopyOnWriteArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+</ol>
+<p>其中比较推荐的解决方案是使用<code>CopyOnWriteArrayList</code>。
+<code>CopyWriteArrayList</code>字面意思就是在写的时候复制，思想就是读写分离的思想。它的基本原理是每次修改操作都会创建该列表的一个新副本，因此读操作不需要加锁，可以并发执行。
+以下是<code>CopyOnWriteArrayList</code>的<code>add()</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The array, accessed only via getArray/setArray. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The lock protecting all mutators */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Gets the array.  Non-private so as to also be accessible
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * from CopyOnWriteArraySet class.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="nf">getArray</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Appends the specified element to the end of this list.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param e element to be appended to this list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@code true}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">lock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elements</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">newElements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elements</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newElements</span><span class="o">[</span><span class="n">len</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setArray</span><span class="p">(</span><span class="n">newElements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>保证了某个线程在写的时候不会被打断。
+可以看到源码开始先是复制了一份数组，同一时刻只有一个线程写，其余的线程会读。在复制的数组上边进行写操作，写好以后在返回<code>true</code>。
+这样就把读写进行了分离，写好以后因为<code>array</code>加了<code>volatile</code>修饰，所以该数组是对于其他的线程是可见的，就会读取到最新的值。
+由于每次写操作都会创建一个数组的新副本，所以写操作的开销较大。但是读取操作非常高效且不需要加锁，因此适用于读操作远多于写操作的场景，例如缓存、白名单等。</p>
+<h3 id="arraylist安全删除">ArrayList安全删除</h3>
+<p>在<code>ArrayList</code>中删除元素时，&ldquo;安全删除&rdquo; 指的是在删除元素过程中避免出现异常或错误，并确保集合的结构和元素的状态保持一致。
+在使用增强型<code>for-each</code>循环遍历<code>ArrayList</code>时，如果尝试删除元素，会抛出<code>ConcurrentModificationException</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayListError</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;C&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;D&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">element</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">element</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">element</span><span class="p">);</span><span class="w"> </span><span class="c1">// 这会抛出 ConcurrentModificationException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在前面讲过<code>add</code>方法，会操作<code>modCount</code>变量的值，在查看源码的时候，发现调用<code>remove</code>方法时，也会操作<code>modCount</code>变量的值。
+当调用<code>remove</code>方法时执行了<code>modCount++</code>，此时<code>modCount</code>变成了<code>N+1</code>。然后接着再循环中遍历调用<code>next</code>方法，调用<code>checkForComodification</code>比较<code>expectedModCount</code>和<code>modCount</code>的大小，此时<code>modCount != expectedModCount</code>，便抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkForComodification</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c1">// 删除指定位置的元素 </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RangeCheck</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 修改modCount</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">modCount</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">E</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">E</span><span class="p">)</span><span class="w"> </span><span class="n">elementData</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">numMoved</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">numMoved</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">numMoved</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="o">[--</span><span class="n">size</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="c1">// Let gc do its work</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">oldValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>安全删除的关键在于，确保在遍历和删除操作中不会同时对集合的结构造成不一致性，从而导致程序运行时出现异常或者结果不符合预期。</p>
+<p>最经典的解决方案是使用<code>Iterator</code>遍历集合，在遍历过程中删除元素。在使用迭代器遍历<code>ArrayList</code>时，迭代器会维护一个<code>expectedModCount</code>，它记录了迭代开始时的<code>modCount</code>。
+每次调用迭代器的<code>next</code>方法时，都会检查当前的<code>modCount</code>是否与<code>expectedModCount</code>相等，如果不相等就抛出<code>ConcurrentModificationException</code>异常。使用迭代器的<code>remove()</code>方法能够确保在删除元素时，同步更新，从而避免异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ArrayList&lt;String&gt; list = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 添加元素到列表中
+</span></span><span class="line"><span class="cl">Iterator&lt;String&gt; iterator = list.iterator();
+</span></span><span class="line"><span class="cl">while (iterator.hasNext()) {
+</span></span><span class="line"><span class="cl">    String element = iterator.next();
+</span></span><span class="line"><span class="cl">    if (/* 满足删除条件 */) {
+</span></span><span class="line"><span class="cl">        iterator.remove(); // 使用迭代器的 remove 方法安全删除元素
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h2 id="hashset">HashSet</h2>
+<p><code>HashSet</code>是基于<code>HashMap</code>来实现的，支持快速查找，但不支持有序性操作。实现了<code>Set</code>接口，同时还实现了序列化和可克隆化。
+<code>Set</code>不允许存储重复的元素，即集合中的元素是唯一的。当试图添加一个已经存在的元素时，<code>add</code>方法会返回<code>false</code>，并且集合不会发生改变。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HashSetExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 HashSet 实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Orange&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 打印 HashSet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;HashSet: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">set</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 尝试添加重复元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">added</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Added duplicate element: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">added</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出: false</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After removing &#39;Banana&#39;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">set</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="去重原理">去重原理</h3>
+<p><code>HashSet</code>内部实际上是由一个<code>HashMap</code>实例支持的，其中<code>HashMap</code>的键值对中的键存储了<code>HashSet</code>中的元素，而值则是一个占位对象，用来表示键已经存在。</p>
+<p>当调用<code>HashSet</code>的<code>add(E e)</code>方法添加元素时，首先会调用元素<code>e</code>的 <code>hashCode</code>方法获取其哈希码。<code>HashSet</code>根据哈希码确定元素在内部<code>HashMap</code>的存储位置。
+如果该位置上已经存在一个元素，则使用 <code>equals</code> 方法比较新元素<code>e</code>与已存在的元素是否相等。
+如果<code>equals</code>方法返回<code>true</code>，则认为新元素与已存在元素相同，不进行添加操作，返回<code>false</code>。
+如果<code>equals</code>方法返回<code>false</code>，则说明哈希码冲突，但实际上是不同的对象，此时将新元素添加到 <code>HashSet</code>中，返回<code>true</code>。
+如果该位置上不存在任何元素，则直接将新元素添加到<code>HashSet</code>中，并返回<code>true</code>。</p>
+<p>简单来说，<code>HashSet</code>利用对象的哈希码和<code>equals</code>方法来确保集合中不存储重复的元素。
+当添加新元素时，先计算其哈希码确定存储位置，如果位置上已存在相同哈希码且通过<code>equals</code>方法比较相等的元素，则不添加，否则添加新元素到集合中。</p>
+<p><code>HashSet</code>添加方法的实现源码如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// hashmap 中 put() 返回 null 时，表示操作成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">e</span><span class="p">,</span><span class="w"> </span><span class="n">PRESENT</span><span class="p">)</span><span class="o">==</span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 返回值：如果插入位置没有元素则返回 null，否则返回上一个元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">put</span><span class="p">(</span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">return</span><span class="w"> </span><span class="n">putVal</span><span class="p">(</span><span class="n">hash</span><span class="p">(</span><span class="n">key</span><span class="p">),</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">false</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">final</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">putVal</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">onlyIfAbsent</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="kt">boolean</span><span class="w"> </span><span class="n">evict</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="c1">//如果哈希表为空，调用 resize() 创建一个哈希表，并用变量 n 记录哈希表长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">tab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">tab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">resize</span><span class="p">()).</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">    * 如果指定参数 hash 在表中没有对应的桶，即为没有碰撞
+</span></span></span><span class="line"><span class="cl"><span class="cm">    * Hash函数，(n - 1) &amp; hash 计算 key 将被放置的槽位
+</span></span></span><span class="line"><span class="cl"><span class="cm">    * (n - 1) &amp; hash 本质上是 hash % n 位运算更快
+</span></span></span><span class="line"><span class="cl"><span class="cm">    */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 直接将键值对插入到 map 中即可</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="c1">// 桶中已经存在元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">K</span><span class="w"> </span><span class="n">k</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 比较桶中第一个元素(数组中的结点)的 hash 值相等，key 相等</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">p</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">hash</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="p">((</span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">.</span><span class="na">key</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">key</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">key</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">k</span><span class="p">))))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 将第一个元素赋值给 e，用 e 来记录</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 当前桶中无该键值对，且桶是红黑树结构，按照红黑树结构插入</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">p</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">((</span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="w"> </span><span class="n">p</span><span class="p">).</span><span class="na">putTreeVal</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 当前桶中无该键值对，且桶是链表结构，按照链表结构插入到尾部</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">binCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">binCount</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 遍历到链表尾部</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">.</span><span class="na">next</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="n">p</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="c1">// 检查链表长度是否达到阈值，达到将该槽位节点组织形式转为红黑树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binCount</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">TREEIFY_THRESHOLD</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="c1">// -1 for 1st</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                  </span><span class="n">treeifyBin</span><span class="p">(</span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="n">hash</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 链表节点的&lt;key, value&gt;与 put 操作&lt;key, value&gt;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 相同时，不做重复操作，跳出循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">hash</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">((</span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">key</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">key</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">key</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">k</span><span class="p">))))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 找到或新建一个 key 和 hashCode 与插入元素相等的键值对，进行 put 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// existing mapping for key</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 记录 e 的 value</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">V</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">          * onlyIfAbsent 为 false 或旧值为 null 时，允许替换旧值
+</span></span></span><span class="line"><span class="cl"><span class="cm">          * 否则无需替换
+</span></span></span><span class="line"><span class="cl"><span class="cm">          */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">onlyIfAbsent</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 访问后回调</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">afterNodeAccess</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 返回旧值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">return</span><span class="w"> </span><span class="n">oldValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="c1">// 更新结构化修改信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="o">++</span><span class="n">modCount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="c1">// 键值对数目超过阈值时，进行 rehash</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="c1">// 插入后回调</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="n">afterNodeInsertion</span><span class="p">(</span><span class="n">evict</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>从上述源码可以看出，当将一个键值对放入<code>HashMap</code>时，首先根据<code>key</code>的<code>hashCode()</code>返回值决定该<code>Entry</code>的存储位置。如果有两个<code>key</code>的<code>hash</code>值相同，则会判断这两个元素<code>key</code>的<code>equals()</code>是否相同，如果相同就返回<code>true</code>，说明是重复键值对，那么<code>HashSet</code>中<code>add</code>方法的返回值会是<code>false</code>，表示<code>HashSet</code>添加元素失败。
+因此，如果向<code>HashSet</code>中添加一个已经存在的元素，新添加的集合元素不会覆盖已有元素，从而保证了元素的不重复。如果不是重复元素，<code>put</code>方法最终会返回<code>null</code>，传递到<code>HashSet</code>的<code>add</code>方法就是添加成功。</p>
+<h3 id="equals与hashcode">equals与hashCode</h3>
+<p>因为<code>HashSet</code>底层用到了<code>equals</code>和<code>hashCode</code>方法，如果对象中的<code>equals</code>和<code>hashCode</code>方法没有正确地重写，可能会导致<code>HashSet</code>在判断元素相等性时出现问题，从而允许添加相同的元素。</p>
+<p><code>equals()</code>地址比较是通过对象的哈希值来比较的。<code>hash</code>值是由<code>hashCode</code>方法产生的，<code>hashCode</code>属于<code>Object</code>类的本地方法，默认使用<code>==</code>比较两个对象，如果<code>equals()</code>相等<code>，hashcode</code>一定相等，如果<code>hashcode</code>相等，<code>equals</code>不一定相等。
+所以在覆盖<code>equals</code>方法时应当总是覆盖<code>hashCode</code>方法，保证等价的两个对象散列值也相等。</p>
+<p>下面的代码中，新建了两个等价的对象，并将它们添加到<code>HashSet</code>中。我们希望将这两个对象当成一样的，只在集合中添加一个对象，但是因为<code>EqualExample</code>没有实现<code>hashCode</code>方法，因此这两个对象的散列值是不同的，最终导致集合添加了两个等价的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">e1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EqualExample</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">e2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EqualExample</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e1</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">e2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">EqualExample</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">e1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">e2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">set</span><span class="p">.</span><span class="na">size</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>所以在覆盖<code>equals</code>方法时应当总是覆盖<code>hashCode</code>方法，保证等价的两个对象散列值也相等。</p>
+<h3 id="线程安全-1">线程安全</h3>
+<p><code>HashSet</code>和<code>ArrayList</code>类似，也是线程不安全的集合类，也会出现<code>ConcurrentModificationException</code>异常。代码演示线程不安全示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">set</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>HashSet</code>线程不安全的解决方案通常是使用<code>CopyOnWriteArraySet</code>。这种集合在读操作远多于写操作的场景中非常有用，因为它通过每次修改创建集合的副本来实现线程安全。
+<code>CopyOnWriteArraySet</code>是Java中一种线程安全的<code>Set</code>实现，内部使用了<code>CopyOnWriteArrayList</code>来存储元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">al</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an empty set.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">CopyOnWriteArraySet</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">al</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>因为底层用<code>CopyOnWriteArrayList</code>存储，所以写操作开销大，每次修改都会创建数组副本，适用场景有限。不适用于写操作频繁的场景，否则会导致高昂的内存和时间开销。
+与<code>CopyOnWriteArrayList</code>不同的是，<code>CopyOnWriteArraySet</code>不允许包含重复元素。如果尝试添加一个已经存在的元素，集合将保持不变，所以该集合在线程不安全的情况下可替代<code>HashSet</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CopyOnWriteArraySetExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 创建一个 CopyOnWriteArraySet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">cowSet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArraySet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w"> </span><span class="c1">// 不允许重复元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Set: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fruit</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">cowSet</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">fruit</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 添加新元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Grapes&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After adding Grapes: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After removing Banana: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="queue">Queue</h2>
+<p>在Java中，队列是一种常用的数据结构，用于按顺序存储元素，通常以先进先出(<code>FIFO</code>：<code>First In First Out</code>)的方式进行操作。
+它和<code>List</code>的区别在于，<code>List</code>可以在任意位置添加和删除元素，而队列只有两个操作，把元素添加到队列末尾，或者从队列头部取出元素。</p>
+<p>常见实现：</p>
+<ul>
+<li><code>LinkedList</code>：<code>LinkedList</code>类实现了<code>Queue</code>接口，同时也实现了<code>Deque</code>接口（双端队列）。它可以作为队列、双端队列或堆栈使用；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Queue&lt;String&gt; queue = new LinkedList&lt;&gt;();
+</span></span><span class="line"><span class="cl">queue.offer(&#34;A&#34;);
+</span></span><span class="line"><span class="cl">queue.offer(&#34;B&#34;);
+</span></span><span class="line"><span class="cl">queue.poll(); // 返回 &#34;A&#34; 并移除
+</span></span></code></pre></div></li>
+<li><code>PriorityQueue</code>：<code>PriorityQueue</code>是一个基于优先级堆实现的队列，元素根据其自然顺序进行排序；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">PriorityQueue&lt;Integer&gt; pq = new PriorityQueue&lt;&gt;();
+</span></span><span class="line"><span class="cl">pq.offer(2);
+</span></span><span class="line"><span class="cl">pq.offer(1);
+</span></span><span class="line"><span class="cl">pq.offer(3);
+</span></span><span class="line"><span class="cl">pq.poll(); // 返回 1 并移除
+</span></span></code></pre></div></li>
+<li><code>ArrayDeque</code>：<code>ArrayDeque</code>类实现了<code>Deque</code>接口，是一个可调整大小的数组实现的双端队列，通常比<code>LinkedList</code>更快；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Deque&lt;String&gt; deque = new ArrayDeque&lt;&gt;();
+</span></span><span class="line"><span class="cl">deque.offer(&#34;A&#34;);
+</span></span><span class="line"><span class="cl">deque.offerFirst(&#34;B&#34;);
+</span></span><span class="line"><span class="cl">deque.pollLast(); // 返回 &#34;A&#34; 并移除
+</span></span></code></pre></div></li>
+</ul>
+<p>队列的实现通常不允许插入<code>null</code>元素，尽管一些实现，如<code>LinkedList</code>，不禁止插入<code>null</code>元素。
+即使在允许的实现中，<code>null</code>也不应插入队列中，因为<code>poll</code>方法也使用<code>null</code>作为特殊返回值，用来表示队列不包含任何元素。这会导致难以区分队列中的<code>null</code>元素和队列为空的情况。</p>
+<p><code>poll()</code>和<code>peek()</code>方法：</p>
+<ul>
+<li><code>poll()</code>: 检索并删除此队列的头部，如果此队列为空，则返回<code>null</code>；</li>
+<li><code>peek()</code>: 检索但不删除此队列的头部，如果此队列为空，则返回<code>null</code>；</li>
+</ul>
+<h2 id="hashmap">HashMap</h2>
+<p><code>HashMap</code>是一个散列表，它存储的内容是键值对(<code>key-value</code>)映射。
+<code>HashMap</code>实现了<code>Map</code>接口，根据键的<code>HashCode</code>值存储数据，具有很快的访问速度，最多允许一条记录的键为<code>null</code>，不支持线程同步。<code>HashMap</code>是无序的，即不会记录插入的顺序。</p>
+<p>相关操作：</p>
+<ul>
+<li>存储：通过<code>key</code>的<code>hashcode</code>方法找到在<code>hashMap</code>存储的位置，如果该位置有元素则通过<code>equals</code>方法进行比较，如果<code>equals</code>返回值为<code>true</code>，则覆盖<code>value</code>；
+如果<code>equals</code>返回值为<code>false</code>则在该数组元素的头部追加该元素，形成一个链表结构；</li>
+<li>读取：通过<code>key</code>的<code>hashcode</code>方法获取元素存在该数组的位置，然后通过<code>equals</code>拿到该值；</li>
+</ul>
+<p>总的来说<code>hashMap</code>底层将<code>key-value</code>当成一个整体来处，<code>hashMap</code>底层采用一个<code>Entry</code>数组保存所有的键值对。
+当存储一个<code>entry</code>对象时，会根据<code>key</code>的<code>hashCode</code>来决定存放在数组中的位置，再根据<code>equals</code>方法来确定在链表中的位置，读取一个<code>entry</code>对象。
+<code>equals</code>和<code>hashCode</code>在<code>hashMap</code>中就像一个坐标一样，来定位<code>hashMap</code>中的值。</p>
+<h3 id="hashmap结构">HashMap结构</h3>
+<p><img alt="HashMap结构" src="/iblog/posts/annex/images/essays/HashMap%E7%BB%93%E6%9E%84.png"></p>
+<p>在JDK1.7及之前结构为<code>数组+单向链表</code>，JDK1.8及之后结构为<code>数组 + 单向链表/红黑树</code>。
+在JDK1.8时，如果存储<code>Map</code>中数组元素对应的索引的每个链表超过8，就将单向链表转化为红黑树，当红黑树的节点少于6个的时候又开始使用链表。</p>
+<p>那么为什么要使用红黑树？
+当有发生大量的<code>hash</code>冲突时，因为链表遍历效率很慢，为了提升查询的效率，所以使用了红黑树的数据结构。</p>
+<p>为什么不一开始就用红黑树代替链表结构？</p>
+<blockquote>
+<p>Because TreeNodes are about twice the size of regular nodes, we use them only when bins contain enough nodes to warrant use  (see TREEIFY_THRESHOLD).
+And when they become too small (due to removal or resizing) they are converted back to plain bins.</p>
+</blockquote>
+<p>这是JDK文档注释，大意为：单个<code>TreeNode</code>需要占用的空间大约是普通<code>Node</code>的两倍，所以只有当包含足够多的<code>Nodes</code>时才会转成<code>TreeNodes</code>，而是否足够多就是由<code>TREEIFY_THRESHOLD</code>的值(默认值8)决定的。
+而当桶中节点数由于移除或者<code>resize</code>变少后，又会变回普通的链表的形式，以便节省空间，这个阈值是<code>UNTREEIFY_THRESHOLD</code>(默认值6)。</p>
+<p>为什么树化阈值要设置为8？
+如果<code>hashCode</code>分布良好，也就是<code>hash</code>计算的结果离散好的话，那么红黑树这种形式是很少会被用到的，因为各个值都均匀分布，很少出现链表很长的情况。
+在理想情况下，链表长度符合泊松分布，各个长度的命中概率依次递减，当长度为8的时候，概率仅为0.00000006。
+这是一个小于千万分之一的概率，通常我们的<code>Map</code>里面是不会存储这么多的数据的，所以通常情况下，并不会发生从链表向红黑树的转换。</p>
+<p><code>HashMap</code>是通过<code>hash</code>算法来判断对象应该放在哪个桶里面的。JDK并不能阻止我们用户实现自己的哈希算法，如果我们故意把哈希算法变得不均匀，那么每次存放对象很容易造成<code>hash</code>冲突。
+链表长度超过8就转为红黑树的设计，更多的是为了防止用户自己实现了不好的哈希算法时导致链表过长，从而导致查询效率低，而此时转为红黑树更多的是一种保底策略，用来保证极端情况下查询的效率。
+红黑树的引入保证了在大量<code>hash</code>冲突的情况下，<code>HashMap</code>还具有良好的查询性能。</p>
+<p>那么在JDK1.8引入红黑树后，如果单链表节点个数超过8个是否一定会树化？
+这是不一定的，在进行树化之前会进行判断<code>(n = tab.length) &lt; MIN_TREEIFY_CAPACITY)</code>是否需要扩容，如果表中数组元素小于这个阈值（默认是64），就会进行扩容。
+因为扩容不仅能增加表中的容量，还能缩短单链表的节点数，从而更长远的解决链表遍历慢问题。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Replaces all linked nodes in bin at index for given hash unless
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * table is too small, in which case resizes instead.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">treeifyBin</span><span class="p">(</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tab</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MIN_TREEIFY_CAPACITY</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">tl</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">replacementTreeNode</span><span class="p">(</span><span class="n">e</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tl</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">hd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">p</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tl</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tl</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">tab</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hd</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">hd</span><span class="p">.</span><span class="na">treeify</span><span class="p">(</span><span class="n">tab</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hash冲突">Hash冲突</h3>
+<p>在<code>HashMap</code>中，哈希冲突，也叫<code>Hash</code>碰撞，是指两个不同的键通过同一散列函数计算得到的哈希值相同，从而映射到同一个桶中。
+当插入<code>HashMap</code>中元素的<code>key</code>出现重复时，这个时候就发生了<code>Hash</code>冲突了。哈希冲突是哈希表必须处理的问题。</p>
+<p>链地址法是处理哈希冲突的常见方法之一，它在每个桶中使用一个链表来存储所有映射到该桶的键值对。具体插入步骤：</p>
+<ol>
+<li>计算键的哈希值并确定其在数组中的位置；</li>
+<li>如果桶为空，直接将键值对存储在该桶中；</li>
+<li>如果桶不为空，则遍历桶中的链表，检查是否存在相同的键；
+<ul>
+<li>如果存在相同的键，更新对应的值；</li>
+<li>如果不存在相同的键，将新的键值对添加到链表的末尾；</li>
+</ul>
+</li>
+</ol>
+<p>在Java8及更高版本中，为了提高性能，当单个桶中的链表长度超过一定阈值（默认是 8）时，会将链表转换为红黑树。
+这种方法在大量冲突的情况下提供了更高效的查找和插入性能。具体插入步骤：</p>
+<ol>
+<li>计算键的哈希值确定存储位置；</li>
+<li>如果存储位置为空，则直接插入新键值对；</li>
+<li>如果存储位置已有节点，当链表长度超过阈值（默认为 8），将链表转换为红黑树，否则继续用链表存储；</li>
+<li>如果当前结点为红黑树结点，则根据节点的哈希值和键值比较，找到合适的插入位置；插入后，根据红黑树的性质进行调整，保持平衡；</li>
+<li>当桶中元素数量减少到一定阈值以下时（默认是 6），会将红黑树转换回链表，以减少内存开销；</li>
+</ol>
+<h3 id="hashmap容量">HashMap容量</h3>
+<p><code>HashMap</code>在创建时需要指定初始容量，如果不指定默认是16。初始容量指的是<code>HashMap</code>中桶的数量，即存储键值对的数组大小。
+如果能预估要存储的键值对数量，可以在创建<code>HashMap</code>时指定初始容量，以避免频繁的扩容操作。</p>
+<p>如果指定容量大小为10，那么实际大小是多少？
+先说答案，实际大小是16，其容量为不小于指定容量的2的N次方。</p>
+<p>为什么容量始终是2的N次方？
+为了减少<code>Hash</code>碰撞，尽量使<code>Hash</code>算法的结果均匀分布。</p>
+<p>当使用<code>put</code>方法时，到底存入<code>HashMap</code>的哪个数组中？
+这是通过<code>hash</code>算法决定的，如果某一个数组中的链表过长旧会影响查询的效率。为了避免出现<code>hash</code>碰撞，让<code>hash</code>尽可能的散列分布，就需要在<code>hash</code>算法上做文章。</p>
+<p>JDK1.7通过逻辑与运算，判断这个元素该进入哪个数组。在下面的代码中<code>length</code>的长度始终为不小于指定容量的2的N次方。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">indexFor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">h</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为了更好的理解这个方法，举个例子，假设<code>h=2</code>或<code>h=3</code>，<code>length=15</code>，执行<code>indexFor</code>方法，最终逻辑与运算后的结果是一致的，因为最终结果是一致的所以就导致了<code>hash</code>碰撞。
+这种问题多了以后会造成容器中的元素分布不均匀，都分配在同一个数组上，在查询的时候就减慢了查询的效率，另一方面也造成空间的浪费。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">-- 2转换为2进制与15-1进行&amp;运算
+</span></span><span class="line"><span class="cl">  0000 0010
+</span></span><span class="line"><span class="cl">&amp; 0000 1110 
+</span></span><span class="line"><span class="cl">———————————— 
+</span></span><span class="line"><span class="cl">  0000 1110
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 3转换为2进制与15-1进行&amp;运算
+</span></span><span class="line"><span class="cl">  0000 0011
+</span></span><span class="line"><span class="cl">&amp; 0000 1110 
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0000 1110
+</span></span></code></pre></div><p>为了避免上面<code>length=15</code>这类问题出现，所以集合的容量采用必须是2的N次幂这种方式。
+因为2的N次幂的结果减一转换为二进制后都是以<code>...1111</code>结尾的，所以在进行逻辑与运算时碰撞几率小。</p>
+<p>在JDK1.8中，在<code>putVal</code>方法中通过<code>i = (n - 1) &amp; hash</code>来计算key的散列地址：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">putVal</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">onlyIfAbsent</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">evict</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 此处省略了代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// i = (n - 1) &amp; hash]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 省略了代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这里的&quot;&amp;&ldquo;等同于&rdquo;%&quot;，但是&quot;%&ldquo;运算的速度并没有&rdquo;&amp;&ldquo;的操作速度快。
+&ldquo;&amp;&ldquo;操作能代替&rdquo;%&ldquo;运算，但必须满足一定的条件，即<code>a%b=a&amp;(b-1)</code>仅当b是2的n次方的时候才成立。</p>
+<p>容器容量怎么保持始终为2的N次方？
+<code>HashMap</code>的<code>tableSizeFor</code>方法做了处理，能保证永远都是2的N次幂。
+如果用户指定了初始容量，那么<code>HashMap</code>会计算出比该数大的第一个2的幂作为初始容量。另外就是在扩容的时候，也是进行成倍的扩容，即4变成8、8变成16。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Returns a power of two size for the given target capacity.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">tableSizeFor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">cap</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 假设n=17</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = 00010001 - 00010000 = 00010000 = 16</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cap</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00010000 | 00001000) = 00011000 = 24</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011000 | 00000110) = 00011110 = 30</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011110 | 00000001) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011111 | 00000000) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">8</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011111 | 00000000) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">16</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = 00011111 = 31，MAXIMUM_CAPACITY：Integer的最大长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// (31 &lt; 0) ? 1 : (31 &gt;= Integer的最大长度) ? Integer的最大长度 : 31 + 1 ;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 即最终返回 32 = 2 的 (n=5)次方</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>发现上面在进行<code>&gt;&gt;&gt;</code>操作时会将<code>cap</code>变量的二进制值变为最高位后边全是1，即<code>00010001 -&gt; 00011111</code>，所以这个算法就导致了任意传入一个数值，会将该数字变为它的2倍减1，因为任何尾数全为1的在加1都为2的倍数。
+至于开头减1，是因为如果给定的n已经是2的次幂，但是不进行减1操作的话，那么得到的值就是大于给定值的最小2的次幂值，例如，传入4就会返回8。
+这里面最大右移到16位，因为最大值是32个1，这是int类型存储变量的最大值，在往后就没意义了。</p>
+<p><code>HashMap</code>默认初始化容量为什么是16？
+这个问题没有找到相关解释。我推断这应该就是个经验值，既然一定要设置一个默认的<code>2^n</code>作为初始值，那么就需要在效率和内存使用上做一个权衡。
+这个值既不能太小，也不能太大，太小了就有可能频繁发生扩容，影响效率；太大了又浪费空间，不划算。所以16就作为一个经验值被采用了。</p>
+<p>关于默认容量的定义，故意把16写成<code>1 &lt;&lt; 4</code>这种形式，就是提醒开发者，这个地方要是2的次幂，与上面呼应。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * The default initial capacity - MUST be a power of two.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w"> </span><span class="c1">// aka 16</span><span class="w">
+</span></span></span></code></pre></div><p>那么<code>HashMap</code>初始化容量设置多少合适？
+当我们使用<code>HashMap(int initialCapacity)</code>来初始化容量的时候，<code>HashMap</code>并不会使用我们传进来的<code>initialCapacity</code>直接作为初始容量。
+JDK会默认帮我们计算一个相对合理的值当做初始容量，所谓合理值，其实是找到第一个比用户传入的值大的2的幂。
+如果创建<code>HashMap</code>初始化容量设置为7，那么<code>HashMap</code>通过计算会创建一个初始化为8的<code>HashMap</code>。当<code>HashMap</code>中的元素到<code>0.75 * 8 = 6</code>就会进行<strong>扩容</strong>，这明显是我们不希望看到的。</p>
+<blockquote>
+<p>负载因子，表示HashMap满的程度，默认值为0.75f，也就是说默认情况下，当HashMap中元素个数达到了容量的3/4的时候就会进行自动扩容；</p>
+</blockquote>
+<p>设置多少合适，可以参考JDK8中<code>putAll</code>方法中的实现：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">(int) ((float) expectedSize / 0.75F + 1.0F);
+</span></span></code></pre></div><p>通过<code>expectedSize/0.75F+1.0F</code>计算，将初始化容量设置为7带入，得到<code>7/0.75+1=10</code>，10经过JDK处理之后，会被设置成16，这就大大的减少了扩容的几率。
+当我们明确知道<code>HashMap</code>中元素的个数的时候，把默认容量设置成<code>expectedSize/0.75F+1.0F</code> 是一个在性能上相对好的选择，但同时也会牺牲些内存。</p>
+<p>这个算法在<code>guava</code>中也有实现，开发的时候，可以直接通过<code>Maps</code>类创建一个<code>HashMap</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Maps</span><span class="p">.</span><span class="na">newHashMapWithExpectedSize</span><span class="p">(</span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">newHashMapWithExpectedSize</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedSize</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="p">(</span><span class="n">capacity</span><span class="p">(</span><span class="n">expectedSize</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">capacity</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedSize</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">expectedSize</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">3</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CollectPreconditions</span><span class="p">.</span><span class="na">checkNonnegative</span><span class="p">(</span><span class="n">expectedSize</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;expectedSize&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">expectedSize</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">expectedSize</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1073741824</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)((</span><span class="kt">float</span><span class="p">)</span><span class="n">expectedSize</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">75F</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">.</span><span class="na">0F</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">2147483647</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hashmap扩容">HashMap扩容</h3>
+<p>随着<code>HashMap</code>中的元素增加，<code>Hash</code>碰撞导致获取元素方法的效率就会越来越低。为了保证获取元素方法的效率，所以针对<code>HashMap</code>中的数组进行扩容。
+扩容数组的方式只能再去开辟一个新的数组，并把之前的元素转移到新数组上。</p>
+<p><code>HashMap</code>的容量是有上限的，必须小于<code>1&lt;&lt;30</code>，即<code>1073741824</code>。如果容量超出了这个数，则不再增长，且阈值会被设置为<code>Integer.MAX_VALUE</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// Java8
+</span></span><span class="line"><span class="cl">if (oldCap &gt;= MAXIMUM_CAPACITY) {
+</span></span><span class="line"><span class="cl">    threshold = Integer.MAX_VALUE;
+</span></span><span class="line"><span class="cl">    return oldTab;
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// Java7
+</span></span><span class="line"><span class="cl">if (oldCapacity == MAXIMUM_CAPACITY) { 
+</span></span><span class="line"><span class="cl">    threshold = Integer.MAX_VALUE;
+</span></span><span class="line"><span class="cl">    return;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在<code>HashMap</code>中有一个概念叫<code>loadFactor</code>，即负载因子，它表示<code>HashMap</code>满的程度，默认值为<code>0.75f</code>，也就是说默认情况下，当<code>HashMap</code>中元素个数达到了容量的3/4的时候就会进行自动扩容。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>为什么负载因子默认设置为0.75？</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * The load factor used when none specified in constructor.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">DEFAULT_LOAD_FACTOR</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">75f</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>在<a href="https://docs.oracle.com/javase/6/docs/api/java/util/HashMap.html">JDK的官方文档</a>中解释如下：</p>
+<blockquote>
+<p>As a general rule, the default load factor (.75) offers a good tradeoff between time and space costs.
+Higher values decrease the space overhead but increase the lookup cost (reflected in most of the operations of the HashMap class, including get and put).
+The expected number of entries in the map and its load factor should be taken into account when setting its initial capacity, so as to minimize the number of rehash operations.
+If the initial capacity is greater than the maximum number of entries divided by the load factor, no rehash operations will ever occur.</p>
+</blockquote>
+<p>文档大意：一般来说，默认的负载因子(0.75)在时间和空间成本之间提供了很好的权衡。
+更高的值减少了空间开销，但增加了查找成本(反映在<code>HashMap</code>类的大多数操作中，包括<code>get</code>和<code>put</code>)。
+在设置映射的初始容量时，应该考虑映射中预期的条目数及其负载因子，以便最小化重哈希操作的数量。如果初始容量大于最大条目数除以负载因子，则不会发生重新散列操作。</p>
+<p>负载因子和<code>HashMap</code>中的扩容有关，当<code>HashMap</code>中的元素大于临界值（<code>threshold = loadFactor * capacity</code>）就会扩容。
+所以负载因子的大小决定了什么时机扩容，扩容又影响到了hash碰撞的频率，所以设置一个合理的负载因子可以有效的避免<code>hash</code>碰撞。</p>
+<p>设置为0.75的其他解释：</p>
+<ul>
+<li>根据数学公式推算，这个值在<code>log(2)</code>的时候比较合理；</li>
+<li>为了提升扩容效率，<code>HashMap</code>的容量有一个固定的要求，那就是一定是2的幂。如果负载因子是3/4的话，那么和容量的乘积结果就可以是一个整数；</li>
+</ul>
+<h4 id="17扩容">1.7扩容</h4>
+<p>扩容步骤：</p>
+<ol>
+<li>当插入新的键值对使得元素数量超过阈值时，<code>HashMap</code>会进行扩容；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">addEntry</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">bucketIndex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//size：The number of key-value mappings contained in this map.  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//threshold：The next size value at which to resize (capacity * load factor)  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//数组扩容条件：1.已经存在的key-value mappings的个数大于等于阈值  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//             2.底层数组的bucketIndex坐标处不等于null  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="kc">null</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">table</span><span class="o">[</span><span class="n">bucketIndex</span><span class="o">]</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">(</span><span class="n">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">table</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="c1">//扩容之后，数组长度变了  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hash</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kc">null</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">hash</span><span class="p">(</span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="c1">//为什么要再次计算一下hash值呢？  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bucketIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">indexFor</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">table</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="c1">//扩容之后，数组长度变了，在数组的下标跟数组长度有关，得重算。  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">createEntry</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="n">bucketIndex</span><span class="p">);</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w"> 
+</span></span></span></code></pre></div></li>
+<li>创建一个新的数组，新的容量是原来的两倍，新阈值=新容量*负载因子；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">resize</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">   </span><span class="c1">//传入新的容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">oldTable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">    </span><span class="c1">//引用扩容前的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldTable</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  </span><span class="c1">//扩容前的数组大小如果已经达到最大(2^30)了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w"> </span><span class="c1">//修改阈值为int的最大值(2^31-1)，这样以后就不会扩容了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">newTable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Entry</span><span class="o">[</span><span class="n">newCapacity</span><span class="o">]</span><span class="p">;</span><span class="w">  </span><span class="c1">//初始化一个新的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">transfer</span><span class="p">(</span><span class="n">newTable</span><span class="p">);</span><span class="w">                         </span><span class="c1">//！！将数据转移到新的Entry数组里</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">table</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="p">;</span><span class="w">                           </span><span class="c1">//HashMap的table属性引用新的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">);</span><span class="c1">//修改阈值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>将旧表中的所有元素重新计算哈希值，并放入新表中：通过<code>transfer</code>方法将旧数组上的元素转移到扩容后的新数组上。遍历旧表中的每个桶，对于每个桶中的每个节点，重新计算它们在新表中的索引位置，将节点放入新表的相应位置；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">transfer</span><span class="p">(</span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">newTable</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">src</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">                   </span><span class="c1">//src引用了旧的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">src</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">//遍历旧的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">src</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">             </span><span class="c1">//取得旧Entry数组的每个元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">src</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="c1">//释放旧Entry数组的对象引用（for循环后，旧的Entry数组不再引用任何对象）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">indexFor</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="p">,</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">);</span><span class="w"> </span><span class="c1">//！！重新计算每个元素在数组中的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">//标记[1]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">newTable</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">      </span><span class="c1">//将元素放在数组上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">             </span><span class="c1">//访问下一个Entry链上的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>将旧表引用指向新表；</li>
+</ol>
+<h4 id="18扩容">1.8扩容</h4>
+<p>Java1.8的<code>HashMap</code>扩容原理与1.7类似，但有一些重要改进。
+在1.8时做了一些优化，文档注释写的很清楚：&ldquo;元素的位置要么是在原位置，要么是在原位置再移动<strong>2次幂的位置</strong>&quot;。也就是对比1.7的迁移到新的数组上省去了重新计算<code>hash</code>值的时间。</p>
+<p>这里的&quot;2次幂的位置&quot;是指长度为原来数组元素两倍的位置。
+假设旧容量是16，那么其二进制表示是<code>10000</code>，扩容后的新容量是32，其二进制表示是<code>100000</code>。<code>HashMap</code>通过<code>h &amp; (length - 1)</code>计算索引。
+在扩容之前，容量为16，根据公式<code>hash &amp; (oldCapacity - 1)</code>计算，因为<code>oldCapacity - 1</code>的二进制是<code>0000 1111</code>，那么计算索引时使用的是哈希值的低四位。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">扩容之前的位置：
+</span></span><span class="line"><span class="cl">  0101 0101
+</span></span><span class="line"><span class="cl">&amp; 0000 1111
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0000 0101
+</span></span></code></pre></div><p>扩容后，新的索引还是通过<code>hash &amp; (newCapacity - 1)</code>计算的，若容量为32，因为<code>newCapacity - 1</code>的二进制是<code>0001 1111</code>，那么计算索引时使用的是哈希值的低五位。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">扩容之后的位置：
+</span></span><span class="line"><span class="cl">  0101 0101
+</span></span><span class="line"><span class="cl">&amp; 0001 1111
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0001 0101
+</span></span></code></pre></div><p>扩容后，新的索引位置只受到哈希值高位的影响，所以叫高位优化。
+高位优化的关键在于，如果一个哈希值在旧容量下的索引是<code>index</code>，那么在新容量下，这个哈希值要么在<code>index</code>位置，要么在<code>index + oldCapacity</code>位置。
+例如上面的例子，容量为16，扩容之前的位置为<code>0000 0101</code>即5，扩容之后的位置为<code>0001 0101</code>即21（16+5）。
+通过这种高位优化技术，Java1.8中的<code>HashMap</code>在扩容时无需重新计算所有元素的哈希值，只需根据哈希值的高位来判断元素的新位置，所以提高了扩容的效率。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Initializes or doubles table size.  If null, allocates in
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * accord with initial capacity target held in field threshold.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Otherwise, because we are using power-of-two expansion, the
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * elements from each bin must either stay at same index, or move
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * with a power of two offset in the new table.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return the table
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="nf">resize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">oldTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">oldTab</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">oldTab</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">threshold</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newCap</span><span class="p">,</span><span class="w"> </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">oldTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCap</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                     </span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldThr</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// double threshold</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldThr</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="c1">// initial capacity was placed in threshold</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldThr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">               </span><span class="c1">// zero initial threshold signifies using defaults</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)(</span><span class="n">DEFAULT_LOAD_FACTOR</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newThr</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">float</span><span class="w"> </span><span class="n">ft</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="n">newCap</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">newCap</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">ft</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">?</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                      </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">ft</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newThr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">({</span><span class="s">&#34;rawtypes&#34;</span><span class="p">,</span><span class="s">&#34;unchecked&#34;</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">newTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">[</span><span class="n">newCap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">table</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldTab</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">oldCap</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">oldTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 单个节点，直接移动到新表中的新位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">newTab</span><span class="o">[</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">newCap</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 红黑树节点，处理红黑树的拆分逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">((</span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">e</span><span class="p">).</span><span class="na">split</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">newTab</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="p">,</span><span class="w"> </span><span class="n">oldCap</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// preserve order</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 处理链表节点，使用高位优化技术重新分配节点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">loHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">loTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hiHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">hiTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                           </span><span class="c1">// 判断节点在新表中的位置，高位优化的关键</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">oldCap</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                               </span><span class="c1">// 保持在原位置（低位链表）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">loHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">loTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">loTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                               </span><span class="c1">// 移动到新位置（高位链表）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">hiTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">hiHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">hiTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">hiTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 将低位链表和高位链表分别放入新表中的相应位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loTail</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">loTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">newTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">loHead</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">hiTail</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">hiTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">newTab</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">oldCap</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hiHead</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">newTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="线程安全-2">线程安全</h3>
+<p><code>HashMap</code>是线程不安全的集合类。因为<code>HashMap</code>中的方法大多没有同步，这意味着如果一个线程在遍历<code>HashMap</code>的同时，另一个线程修改了<code>HashMap</code>，例如添加或删除元素，可能会导致<code>ConcurrentModificationException</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="n">Object</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">(),</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">map</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>更严重的是，当多个线程中的<code>HashMap</code>同时扩容时，再使用<code>put</code>方法添加元素，如果<code>hash</code>值相同，可能出现同时在同一数组下用链表表示，造成闭环，导致在<code>get</code>时会出现死循环，CPU飙升到100%。</p>
+<p>在大多数并发场景中，推荐使用<code>ConcurrentHashMap</code>，因为它设计用于高并发环境，并且在大多数情况下性能优于使用同步包装或手动同步的<code>HashMap</code>。
+<code>ConcurrentHashMap</code>是Java中的一种线程安全的哈希表实现，用来替代传统的<code>HashMap</code>，来解决在多线程环境中并发修改带来的问题。
+与<code>Hashtable</code>不同，<code>ConcurrentHashMap</code>不对整个表进行全局加锁。相反它只对具体操作涉及的部分进行加锁，减少了线程之间的竞争。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConcurrentHashMapExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ConcurrentHashMap</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentHashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;One&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Two&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Value for key 1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">keySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Key: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Value: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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diff --git a/blog-site/public/posts/javabasics/rookie-multi-thread/index.html b/blog-site/public/posts/javabasics/rookie-multi-thread/index.html
new file mode 100644
index 00000000..b4cedb19
--- /dev/null
+++ b/blog-site/public/posts/javabasics/rookie-multi-thread/index.html
@@ -0,0 +1,6708 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
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+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
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+	<title>Java多线程 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="线程与进程 进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。 线程是操作系统能够进行运算调度的最小单位。它被包" />
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+
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+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e4%b8%8e%e8%bf%9b%e7%a8%8b">
+                    线程与进程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e7%9a%84%e5%b9%b6%e8%a1%8c%e4%b8%b2%e8%a1%8c%e5%b9%b6%e5%8f%91">
+                    线程的并行、串行、并发
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e7%9a%84%e5%90%8c%e6%ad%a5%e5%bc%82%e6%ad%a5">
+                    线程的同步、异步
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%88%e6%8a%a4%e7%ba%bf%e7%a8%8b">
+                    守护线程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e7%9a%84%e7%8a%b6%e6%80%81">
+                    线程的状态
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e7%9b%b8%e5%85%b3%e6%96%b9%e6%b3%95">
+                    线程相关方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%9b%e5%bb%ba%e7%ba%bf%e7%a8%8b">
+                    创建线程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#thread">
+                    Thread
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#runnable">
+                    Runnable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#callable">
+                    Callable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e6%b1%a0">
+                    线程池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%9b%e5%bb%ba%e6%96%b9%e5%bc%8f">
+                    创建方式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%87%aa%e5%ae%9a%e4%b9%89%e7%ba%bf%e7%a8%8b%e6%b1%a0">
+                    自定义线程池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e6%b1%a0%e5%b7%a5%e4%bd%9c%e5%8e%9f%e7%90%86">
+                    线程池工作原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%98%bb%e5%a1%9e%e9%98%9f%e5%88%97">
+                    阻塞队列
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e6%b1%a0%e5%8f%82%e6%95%b0">
+                    线程池参数
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%90%88%e7%90%86%e9%85%8d%e7%bd%ae%e7%ba%bf%e7%a8%8b%e6%b1%a0%e5%8f%82%e6%95%b0">
+                    合理配置线程池参数
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%94%81">
+                    锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%ac%e5%b9%b3%e9%94%81%e4%b8%8e%e9%9d%9e%e5%85%ac%e5%b9%b3%e9%94%81">
+                    公平锁与非公平锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%af%e9%87%8d%e5%85%a5%e9%94%81%e4%b8%8e%e4%b8%8d%e5%8f%af%e9%87%8d%e5%85%a5%e9%94%81">
+                    可重入锁与不可重入锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%b1%e4%ba%ab%e9%94%81%e4%b8%8e%e7%8b%ac%e5%8d%a0%e9%94%81">
+                    共享锁与独占锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%82%b2%e8%a7%82%e9%94%81%e4%b8%8e%e4%b9%90%e8%a7%82%e9%94%81">
+                    悲观锁与乐观锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%87%aa%e6%97%8b%e9%94%81%e4%b8%8e%e9%80%82%e5%ba%94%e6%80%a7%e8%87%aa%e6%97%8b%e9%94%81">
+                    自旋锁与适应性自旋锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%81%8f%e5%90%91%e9%94%81">
+                    偏向锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bd%bb%e9%87%8f%e7%ba%a7%e9%94%81%e4%b8%8e%e9%87%8d%e9%87%8f%e7%ba%a7%e9%94%81">
+                    轻量级锁与重量级锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%af%e4%b8%ad%e6%96%ad%e9%94%81">
+                    可中断锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%92%e6%96%a5%e9%94%81">
+                    互斥锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%ad%bb%e9%94%81">
+                    死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e8%b5%84%e6%ba%90%e6%9c%89%e5%ba%8f%e5%88%86%e9%85%8d%e6%b3%95%e9%81%bf%e5%85%8d%e6%ad%bb%e9%94%81">
+                    使用资源有序分配法避免死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e9%93%b6%e8%a1%8c%e5%ae%b6%e7%ae%97%e6%b3%95%e9%81%bf%e5%85%8d%e6%ad%bb%e9%94%81">
+                    使用银行家算法避免死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8trylock%e8%bf%9b%e8%a1%8c%e8%b6%85%e6%97%b6%e9%94%81%e5%ae%9a">
+                    使用tryLock进行超时锁定
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#java%e5%86%85%e5%ad%98%e6%a8%a1%e5%9e%8b">
+                    Java内存模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8e%9f%e5%ad%90%e6%80%a7">
+                    原子性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%af%e8%a7%81%e6%80%a7">
+                    可见性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%89%e5%ba%8f%e6%80%a7">
+                    有序性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%99%90%e5%88%b6%e5%a4%84%e7%90%86%e5%99%a8%e4%bc%98%e5%8c%96">
+                    限制处理器优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%85%e5%ad%98%e5%b1%8f%e9%9a%9c">
+                    内存屏障
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#happens-before">
+                    Happens-Before
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#as-if-serial">
+                    as-if-serial
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#volatile">
+                    volatile
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e6%a1%88%e4%be%8b">
+                    使用案例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#volatile%e4%b8%8e%e5%8f%af%e8%a7%81%e6%80%a7">
+                    volatile与可见性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#volatile%e4%b8%8e%e6%9c%89%e5%ba%8f%e6%80%a7">
+                    volatile与有序性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#volatile%e4%b8%8e%e5%8e%9f%e5%ad%90%e6%80%a7">
+                    volatile与原子性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#synchronized">
+                    synchronized
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e7%a4%ba%e4%be%8b">
+                    使用示例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86">
+                    实现原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%94%81%e7%9a%84%e5%8d%87%e7%ba%a7">
+                    锁的升级
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#synchronized%e4%b8%8e%e5%8f%af%e8%a7%81%e6%80%a7">
+                    synchronized与可见性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#synchronized%e4%b8%8e%e5%8e%9f%e5%ad%90%e6%80%a7">
+                    synchronized与原子性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#synchronized%e4%b8%8e%e6%9c%89%e5%ba%8f%e6%80%a7">
+                    synchronized与有序性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cas">
+                    CAS
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e7%a4%ba%e4%be%8b-1">
+                    使用示例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#unsafe">
+                    Unsafe
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86-1">
+                    实现原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cas%e9%97%ae%e9%a2%98">
+                    CAS问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#juc%e5%8c%85">
+                    J.U.C.包
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#lock">
+                    Lock
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#readwritelock">
+                    ReadWriteLock
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#locksupport">
+                    LockSupport
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#aqs">
+                    AQS
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#reentrantlock">
+                    ReentrantLock
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e6%af%94synchronized">
+                    对比synchronized
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8a%a0%e9%94%81%e5%8e%9f%e7%90%86">
+                    加锁原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8a%e6%94%be%e9%94%81%e5%8e%9f%e7%90%86">
+                    释放锁原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#countdownlatch">
+                    CountDownLatch
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cyclicbarrier">
+                    CyclicBarrier
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#semaphore">
+                    Semaphore
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#threadlocal">
+                    ThreadLocal
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e6%af%94%e7%ba%bf%e7%a8%8b%e5%90%8c%e6%ad%a5">
+                    对比线程同步
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e7%a4%ba%e4%be%8b-2">
+                    使用示例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86-2">
+                    实现原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%85%e5%ad%98%e6%b3%84%e6%bc%8f%e9%97%ae%e9%a2%98">
+                    内存泄漏问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e7%94%a8%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8%e7%9a%84%e9%9b%86%e5%90%88">
+                    常用线程安全的集合
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#copywritearraylist">
+                    CopyWriteArrayList
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#copyonwritearrayset">
+                    CopyOnWriteArraySet
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashtable">
+                    HashTable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#concurrenthashmap">
+                    ConcurrentHashMap
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jdk17">
+                    JDK1.7
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jdk18">
+                    JDK1.8
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e8%80%83%e6%96%87%e7%ab%a0">
+                    参考文章
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Java多线程</h2>
+                        <span id="post_page_title_date" class="date">2021.05.05</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
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+                    <div class="post_content markdown"><h2 id="线程与进程">线程与进程</h2>
+<ul>
+<li>进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。</li>
+<li>线程是操作系统能够进行运算调度的最小单位。它被包含在进程之中，是进程中的实际执行单位。一个进程可以包含多个线程，这些线程共享进程的内存空间和资源，但有自己的栈和程序计数器。</li>
+</ul>
+<p>进程是操作系统资源分配的基本单位，而线程是处理器任务调度和执行的基本单位。
+一条线程指的是进程中的一个单一顺序的控制流，一个进程至少有一个线程，一个进程中可以并发多个线程，多个线程可共享数据，每条线程并行执行不同的任务。</p>
+<p>Java程序是多线程程序，每启动一个Java程序，至少我们知道的都会包含一个主线程和一个垃圾回收线程。而且启动的时候，每条线程可以并行执行不同的任务。</p>
+<p><img alt="线程与进程的关系" src="/iblog/posts/annex/images/essays/%E7%BA%BF%E7%A8%8B%E4%B8%8E%E8%BF%9B%E7%A8%8B%E7%9A%84%E5%85%B3%E7%B3%BB.jpg"></p>
+<h2 id="线程的并行串行并发">线程的并行、串行、并发</h2>
+<ul>
+<li>并行：前提是在多核CPU，多个线程同时被多个CPU执行，同时执行的线程并不会抢占CPU资源。</li>
+<li>串行：前提是在单核CPU条件下，单线程程序执行，不能同时执行，也不能去切换执行，也就是在同一时间段只能做一件事，如果需要做多件事情需要排队执行。</li>
+<li>并发：前提是多线程条件下，多个线程抢占一个CPU资源，多个线程被交替执行。因为CPU运算速度很快，所以用户感觉不到线程切换的卡顿。</li>
+</ul>
+<table>
+<thead>
+<tr>
+<th></th>
+<th style="text-align:center">单线程</th>
+<th>多线程</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>单CPU</td>
+<td style="text-align:center">串行</td>
+<td>并发</td>
+</tr>
+<tr>
+<td>多CPU</td>
+<td style="text-align:center">串行</td>
+<td>并行</td>
+</tr>
+</tbody>
+</table>
+<p>无论并行、并发，都可以有多个线程执行，如果是多个线程抢占一个CPU，交替执行，并且CPU通过时间片轮转等机制切换执行线程，这种情况下称为并发执行。
+多个线程同时被多个CPU执行，并且各个线程之间不会互相抢占CPU资源，这种情况下称为并行执行。每个线程都在自己的CPU核心上独立执行，互不干扰。</p>
+<p>对于单CPU的计算机来说，同一时间是只能干一件事儿的，如果是单线程就是串行，如果是多个线程就是并发。
+而对于多CPU的计算机说，同一时间能干多个事，如果多个CPU同时执行多个线程就是并行，如果一个CPU同时执行多个线程就是并行。</p>
+<p>并行与并发区别图解
+<img alt="并行与并发区别" src="/iblog/posts/annex/images/essays/%E5%B9%B6%E8%A1%8C%E4%B8%8E%E5%B9%B6%E5%8F%91%E5%8C%BA%E5%88%AB.png"></p>
+<p>并发是两个队列交替使用一台咖啡机，并行是两个队列同时使用两台咖啡机；
+如果串行，一个队列使用一台咖啡机，那么哪怕前面那个人便秘了去厕所呆半天，后面的人也只能死等着他回来才能去接咖啡，这种效率无疑是最低的。</p>
+<h2 id="线程的同步异步">线程的同步、异步</h2>
+<ul>
+<li>同步指的是按顺序执行任务，一个任务的执行必须等待前一个任务完成后才能继续。在同步模式下，任务按照严格的顺序依次执行，每个任务执行完毕后才能进行下一个任务。
+例如，使用关键字<code>synchronized</code>或<code>Lock</code>接口可以实现多线程的同步，确保多个线程按照特定的顺序或条件执行。</li>
+<li>异步指的是任务的执行不依赖于主线程或当前线程，可以通过回调、事件驱动等方式实现任务的并行执行或后台执行。 异步任务可以在任务执行过程中继续执行其他任务，不需要等待当前任务完成。
+异步在Java中通常通过多线程、回调函数或<code>Future</code>、<code>CompletableFuture</code>等方式实现。</li>
+</ul>
+<p>线程与同步异步关系：</p>
+<ul>
+<li>单线程环境下，所有任务按顺序同步执行。如果某个任务阻塞或者等待，整个程序会停止执行直到该任务完成。</li>
+<li>多线程环境下，同步任务可以通过加锁等机制实现对共享资源的安全访问，保证数据的一致性。多线程中的同步操作可以确保多个线程协调执行，避免数据竞争和不一致问题。</li>
+<li>单线程环境中，异步模式通过事件驱动或者非阻塞IO方式实现，可以模拟多任务并发执行的效果。虽然不能真正并行执行多个任务，但可以利用非阻塞方式处理IO或事件，提高响应速度。</li>
+<li>多线程环境中，异步操作通常通过新线程或线程池执行，实现任务的并行处理。多线程中的异步操作可以提高系统的吞吐量和响应能力，充分利用多核处理器的优势。</li>
+</ul>
+<table>
+<thead>
+<tr>
+<th></th>
+<th>单线程</th>
+<th>多线程</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>同步</td>
+<td>只能同步执行，按照顺序执行任务</td>
+<td>可以同步执行，多个线程按顺序执行任务</td>
+</tr>
+<tr>
+<td>异步</td>
+<td>不能直接异步执行，但可以通过事件循环或非阻塞IO模型实现类似异步效果</td>
+<td>可以异步执行，通过多线程或者线程池来实现并行处理</td>
+</tr>
+</tbody>
+</table>
+<h2 id="守护线程">守护线程</h2>
+<p>守护线程是指为其他线程服务的线程。守护线程也称“服务线程”，在没有用户线程可服务时会自动离开。因为作用是服务其他线程，所以在程序中的优先级比较低。
+在JVM中，所有非守护线程都执行完毕后，无论有没有守护线程，虚拟机都会自动退出。</p>
+<p>举例，垃圾回收线程就是一个经典的守护线程，当我们的程序中不再有任何运行的线程，程序就不会再产生垃圾，垃圾回收器也就无事可做。
+所以当垃圾回收线程是JVM上仅剩的线程时，垃圾回收线程会自动离开。它始终在低级别的状态中运行，用于实时监控和管理系统中的可回收资源。
+守护线程在程序中的操作演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="w"> </span><span class="n">daemon</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;启动线程---&gt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">daemon</span><span class="p">.</span><span class="na">setDaemon</span><span class="p">(</span><span class="n">i</span><span class="o">==</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">daemon</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isDaemon</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">daemon</span><span class="p">.</span><span class="na">isDaemon</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前线程是否是守护线程：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">isDaemon</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isDaemon</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">i</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="线程安全">线程安全</h2>
+<p>线程安全是指在多线程环境下，一个类、方法或代码块能够被多个线程安全地访问和修改，不会导致数据不一致性或产生不可预测的行为。线程安全通常通过同步机制实现，来确保多个线程不会同时访问或修改共享资源。</p>
+<p>在多线程并发环境中，多个线程共同操作同一个数据，如果最终数据的值与预期不一致，就会出现线程不安全问题。
+为了解决这个问题，Java中最常用的方法是加锁。当一个线程修改某个数据时，其他线程不能访问该数据，直到该线程操作结束并释放锁，其他线程才能继续操作该数据。</p>
+<p>线程安全问题的根本原因：</p>
+<ul>
+<li>CPU切换线程执导致的原子性问题。当CPU在执行线程时进行上下文切换，一个线程的操作可能在执行一半时被中断，导致另一个线程看到不完整的操作结果，从而出现数据不一致。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Counter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w"> </span><span class="c1">// 这个操作实际上分为三步：读取count值、增加1、写回count值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>缓存可见性问题。由于CPU、内存、IO设备读写速度差异巨大，为了减少CPU等待IO的时间，在CPU和内存之间引入了高速缓存。多核CPU的情况下，每个核心有自己的缓存，这会导致高速缓存与主内存之间的数据不一致，即一个核心对变量的修改，另一个核心可能看不到。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SharedData</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setFlag</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">getFlag</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">flag</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>指令优化重排序问题。编译器和处理器为了优化性能，可能会对指令进行重排序，这不会影响单线程环境下的执行结果，但在多线程环境下，可能导致程序行为不可预测。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Example</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">write</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">           </span><span class="c1">// 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">     </span><span class="c1">// 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">read</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">      </span><span class="c1">// 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="p">);</span><span class="w"> </span><span class="c1">// 4</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h2 id="线程的状态">线程的状态</h2>
+<p>线程状态共包含6种，通过<code>Thread.State</code>枚举类表示的。6种状态又可以互相的转换，线程状态转换关系：</p>
+<p><img alt="线程状态转换" src="/iblog/posts/annex/images/essays/%E7%BA%BF%E7%A8%8B%E8%BD%AC%E6%8D%A2%E5%9B%BE.jpg"></p>
+<ol>
+<li>新建状态(New): 线程被创建但尚未启动。例如，<code>Thread t = new Thread();</code> 状态为NEW；调用线程对象的<code>start()</code>方法会使线程从NEW状态转变为RUNNABLE状态。</li>
+<li>可运行状态(Runnable): 线程在Java虚拟机中执行中。这包括运行状态和就绪状态，线程可能正在运行，也可能等待操作系统为其分配CPU时间。
+<ul>
+<li>就绪（Ready）：线程已经被创建，等待被调度执行。此时可能有多个线程处于就绪状态，但只有一个线程能够获取CPU时间片执行。</li>
+<li>运行中（Running）：就绪的线程获得了CPU时间片，开始执行程序代码。</li>
+</ul>
+</li>
+<li>阻塞状态(Blocked): 当一个线程试图进入一个同步代码块或方法，但该同步块已经被其他线程持有时，线程将进入阻塞状态。阻塞状态的线程将等待获取同步锁，一旦获取到锁就可以转变为RUNNABLE状态。</li>
+<li>无限期等待(Waiting): 当线程调用<code>Object.wait()</code>、<code>Thread.join()</code>或<code>LockSupport.park()</code>方法时，它会进入WAITING状态，直到被其他线程显式唤醒。线程被唤醒后可以转变为RUNNABLE状态。</li>
+<li>限期等待(Timed Waiting): 当线程调用带有超时参数的等待方法，如<code>sleep()</code>、<code>wait(timeout)</code>、<code>join(timeout)</code>、<code>LockSupport.parkNanos()</code>或<code>LockSupport.parkUntil()</code>时，它会进入TIMED_WAITING状态，直到超时时间到达或被其他线程唤醒。
+超时时间到达或被唤醒后可以转变为RUNNABLE状态。</li>
+<li>死亡(Terminated): 线程完成<code>run()</code>方法的执行或者因异常而终止时，会进入TERMINATED状态。一旦线程的<code>run()</code>方法执行完成或抛出未捕获的异常，线程将进入终止状态。</li>
+</ol>
+<p>阻塞和等待的区别在于，阻塞是被动的，它是在等待获取一个排它锁。而等待是主动的，通过调用<code>Thread.sleep()</code>和<code>Object.wait()</code>等方法进入等待。</p>
+<h2 id="线程相关方法">线程相关方法</h2>
+<ul>
+<li><code>start()</code>：启动一个新线程，调用线程的<code>run()</code>方法。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Thread is running&#34;);
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start();
+</span></span></code></pre></div></li>
+<li><code>run()</code>：运行线程中的代码。可以通过继承<code>Thread</code>类并重写<code>run()</code>方法，或通过实现<code>Runnable</code>接口并传递给<code>Thread</code>类的构造函数。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public class MyThread extends Thread {
+</span></span><span class="line"><span class="cl">    public void run() {
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;Thread is running&#34;);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">MyThread t = new MyThread();
+</span></span><span class="line"><span class="cl">t.start();
+</span></span></code></pre></div></li>
+<li><code>sleep(long millis)</code>：让当前线程休眠指定的毫秒数。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    Thread.sleep(1000); // 休眠1秒
+</span></span><span class="line"><span class="cl">} catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>join()</code>：当有新的线程加入时，主线程会进入等待状态，一直到调用<code>join()</code>方法的线程执行结束为止。<code>join()</code>方法的实现依赖于对象的<code>wait()</code>方法。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    try {
+</span></span><span class="line"><span class="cl">        Thread.sleep(2000);
+</span></span><span class="line"><span class="cl">    } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">        e.printStackTrace();
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start();
+</span></span><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    t.join();
+</span></span><span class="line"><span class="cl">} catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>yield()</code>：用于让当前正在执行的线程暂时让出CPU的执行权，使其他线程有机会运行。它不会使线程进入阻塞或等待状态，只是让出当前的CPU时间片，让同等优先权的线程运行。
+如果没有同等优先权的线程，那么<code>yield()</code>方法将不会起作用。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public void run() {
+</span></span><span class="line"><span class="cl">    for (int i = 0; i &lt; 5; i++) {
+</span></span><span class="line"><span class="cl">        System.out.println(threadName + &#34; is running, iteration: &#34; + i);
+</span></span><span class="line"><span class="cl">        // 暂时让出CPU执行权，给其他线程机会
+</span></span><span class="line"><span class="cl">        Thread.yield();
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    System.out.println(threadName + &#34; has finished execution.&#34;);
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">    Thread thread1 = new Thread(new YieldExample(&#34;Thread 1&#34;));
+</span></span><span class="line"><span class="cl">    Thread thread2 = new Thread(new YieldExample(&#34;Thread 2&#34;));
+</span></span><span class="line"><span class="cl">    thread1.start();
+</span></span><span class="line"><span class="cl">    thread2.start();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>wait()</code>：使当前线程等待，直到另一个线程调用该对象的<code>notify()</code>或<code>notifyAll()</code>方法。<code>wait()</code>必须在同步<code>synchronized</code>块里使用。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">synchronized (lock) {
+</span></span><span class="line"><span class="cl">    lock.wait();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>notify()</code>：唤醒一个正在等待该对象的<code>wait()</code>方法的线程。如果多个线程都在该对象的监视器上等待，则任意选择一个线程被唤醒。
+<code>notify()</code>方法必须与<code>wait()</code>方法一起使用，否则会抛出<code>IllegalMonitorStateException</code>异常。<code>notify()</code>方法必须在同步代码块或同步方法中调用，因为它依赖于对象的监视器锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doWaitNotify</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">waitingThread</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is waiting...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w"> </span><span class="c1">// 进入等待状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is notified and resumed.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">waitingThread</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟一些操作延迟</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Notifying waiting thread...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notify</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒等待的线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>需要注意区分<code>wait</code>方法与<code>sleep</code>方法，很多人分不清。<code>sleep</code>和<code>wait</code>方法异同点：</p>
+<ul>
+<li><code>sleep()</code>属于<code>Thread</code>类，<code>wait()</code>属于<code>Object</code>类；</li>
+<li><code>sleep()</code>和<code>wait()</code>都会抛出<code>InterruptedException</code>异常，这个异常属于<code>checkedException</code>是不可避免；</li>
+<li>两者比较的共同之处是，都是使程序等待多长时间。不同的是调用<code>sleep()</code>不会释放锁，会使线程堵塞，而调用<code>wait()</code>会释放锁，让线程进入等待状态，用 <code>notify()</code>、<code>notifyall()</code>可以唤醒，或者等待时间到了；这是因为，如果没有释放锁，那么其它线程就无法进入对象的同步方法或者同步控制块中，那么就无法执行 <code>notify()</code> 或者 <code>notifyAll()</code> 来唤醒挂起的线程，造成死锁。</li>
+<li><code>wait()</code>必须在同步<code>synchronized</code>块里使用，<code>sleep()</code>可以在任意地方使用；</li>
+</ul>
+<p>其中&quot;<code>wait()</code>必须在同步<code>synchronized</code>块里使用&quot;，不止<code>wait</code>方法，<code>notify、notifyAll</code>也和<code>wait</code>方法一样，必须在<code>synchronized</code>块里使用，为什么呢？</p>
+<p>是为了避免丢失唤醒问题。假设没有<code>synchronized</code>修饰，使用了<code>wait</code>方法而没有设置等待时间，也没有调用唤醒方法或者唤醒方法调用的时机不对，这个线程将会永远的堵塞下去。
+<code>wait</code>、<code>notify</code>、<code>notifyAll</code>方法调用的时候要释放锁，你都没给它加锁，他怎么释放锁。所以如果没在<code>synchronized</code>块中调用<code>wait()、notify、notifyAll</code>方法是肯定抛异常的。</p>
+<h2 id="创建线程">创建线程</h2>
+<p>在Java中创建一个线程，有且仅有一种方式，创建一个<code>Thread</code>类实例，并调用它的<code>start</code>方法。</p>
+<h3 id="thread">Thread</h3>
+<p>最经典也是最常见的方式是通过继承<code>Thread</code>类，重写<code>run()</code>方法来创建线程。适用于需要直接控制线程生命周期的情况。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ThreadDemo</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadDemo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ThreadDemo</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;通过继承Thread类的方式创建线程,线程 %s 启动&#34;</span><span class="p">,</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="runnable">Runnable</h3>
+<p>实现<code>Runnale</code>接口，将它作为<code>target</code>参数传递给<code>Thread</code>类构造函数的方式创建线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;通过实现Runnable接口的方式，重写run方法创建线程；线程 %s 启动&#34;</span><span class="p">,</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="callable">Callable</h3>
+<p><code>Callable</code>接口与<code>Runnable</code>类似，但它可以返回结果，并且可以抛出异常，需要配合<code>Future</code>接口使用。通过实现<code>Callable</code>接口，来创建一个带有返回值的线程。
+在<code>Callable</code>执行完之前的这段时间，主线程可以先去做一些其他的事情，事情都做完之后，再获取<code>Callable</code>的返回结果。可以通过<code>isDone()</code>来判断子线程是否执行完。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">ExecutionException</span><span class="p">,</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FutureTask</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">futureTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FutureTask</span><span class="o">&lt;&gt;</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;通过实现Callable接口的方式，重写call方法创建线程；线程 %s 启动&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">10000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;我是call方法返回值&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">futureTask</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;主线程工作中 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">callRet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">callRet</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">futureTask</span><span class="p">.</span><span class="na">isDone</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">callRet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">futureTask</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;主线程继续工作 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;获取call方法返回值：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">callRet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在实际开发中，通常使用异步编程工具，如<code>CompletableFuture</code>。
+<code>CompletableFuture</code>是JDK8的新特性。<code>CompletableFuture</code>实现了<code>CompletionStage</code>接口和<code>Future</code>接口，前者是对后者的一个扩展，增加了异步会点、流式处理、多个<code>Future</code>组合处理的能力，使Java在处理多任务的协同工作时更加顺畅便利。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CompletableFutureRunAsyncExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CompletableFuture</span><span class="o">&lt;</span><span class="n">Void</span><span class="o">&gt;</span><span class="w"> </span><span class="n">future</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CompletableFuture</span><span class="p">.</span><span class="na">runAsync</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 异步执行的任务，没有返回值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Running asynchronously&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">future</span><span class="p">.</span><span class="na">thenRun</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After running asynchronously&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">future</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w"> </span><span class="c1">// 等待任务完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CompletableFuture</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">future</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CompletableFuture</span><span class="p">.</span><span class="na">supplyAsync</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="s">&#34;Hello&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">thenApply</span><span class="p">(</span><span class="n">result</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; CompletableFuture!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="线程池">线程池</h3>
+<p>线程池做的工作主要是控制运行的线程的数量，处理过程中将任务放入队列，然后在线程创建后启动这些任务。如果线程数量超过了最大数量超出数量的线程排队等候，等其它线程执行完毕，再从队列中取出任务来执行。
+线程池是一种用于管理和复用线程的机制，可以有效地提高应用程序的性能和资源利用率。它的主要特点为：线程复用，提高响应速度，管理线程。</p>
+<ul>
+<li>降低资源消耗，通过重复利用己创建的线程降低线程创建和销毁造成的消耗。</li>
+<li>提高响应速度，当任务到达时，任务可以不需要的等到线程创建就能立即执行。</li>
+<li>提高线程的管理性，线程是稀缺资源，如果无限制的创建，不仅会消耗系统资源，还会降低系统的稳定性，使用线程池可以进行统一的分配，调优和监控。</li>
+</ul>
+<h4 id="创建方式">创建方式</h4>
+<p>在Java中，使用<code>java.util.concurrent</code>包中的<code>Executor</code>来创建和管理线程池。几种常见的线程池创建方式：</p>
+<ul>
+<li><code>Executors.newSingleThreadExecutor()</code>：创建只有一个线程的线程池。</li>
+<li><code>Executors.newFixedThreadPool(int)</code>：创建固定线程的线程池。</li>
+<li><code>Executors.newCachedThreadPool()</code>：创建一个可缓存的线程池，线程数量随着处理业务数量变化。</li>
+</ul>
+<p>这三种常用创建线程池的方式，底层代码都是用<code>ThreadPoolExecutor</code>创建的。</p>
+<ol>
+<li>
+<p>使用<code>Executors.newSingleThreadExecutor()</code>创建一个单线程化的线程池，它只会用唯一的工作线程来执行任务，保证所有任务按照指定顺序执行。
+<code>newSingleThreadExecutor</code>将<code>corePoolSize</code>和<code>maximumPoolSize</code>都设置为1，它使用的<code>LinkedBlockingQueue</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">ExecutorService</span><span class="w"> </span><span class="nf">newSingleThreadExecutor</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FinalizableDelegatedExecutorService</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">0L</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedBlockingQueue</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Executors</span><span class="p">.</span><span class="na">newSingleThreadExecutor</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>
+<p>使用<code>Executors.newFixedThreadPool(int)</code>创建一个定长线程池，可控制线程最大并发数，超出的线程会在队列中等待。
+<code>newFixedThreadPool</code>创建的线程池<code>corePoolSize</code>和<code>maximumPoolSize</code>值是相等的，它使用的<code>LinkedBlockingQueue</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">ExecutorService</span><span class="w"> </span><span class="nf">newFixedThreadPool</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">nThreads</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="n">nThreads</span><span class="p">,</span><span class="w"> </span><span class="n">nThreads</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                  </span><span class="n">0L</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                  </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedBlockingQueue</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Executors</span><span class="p">.</span><span class="na">newFixedThreadPool</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>
+<p>使用<code>Executors.newCachedThreadPool()</code>创建一个可缓存线程池，如果线程池长度超过处理需要，可灵活回收空闲线程，若无可回收则新建线程。
+<code>newCachedThreadPool</code>将<code>corePoolSize</code>设置为0，将<code>maximumPoolSize</code>设置为<code>Integer.MAX_VALUE</code>，使用的 <code>SynchronousQueue</code>，也就是说来了任务就创建线程运行，当线程空闲超过60秒，就销毁线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">ExecutorService</span><span class="w"> </span><span class="nf">newCachedThreadPool</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                  </span><span class="n">60L</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">SECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                  </span><span class="k">new</span><span class="w"> </span><span class="n">SynchronousQueue</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Executors</span><span class="p">.</span><span class="na">newCachedThreadPool</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<h4 id="自定义线程池">自定义线程池</h4>
+<p>在实际开发中用哪个线程池？上面的三种一个都不用，我们生产上只能使用自定义的。<code>Executors</code>类中已经给你提供了，为什么不用？</p>
+<blockquote>
+<p>摘自<a href="https://developer.aliyun.com/topic/download?spm=a2c6h.15028928.J_5293118740.2&id=805">《阿里巴巴开发手册》</a>
+【强制】线程资源必须通过线程池提供，不允许在应用中自行显式创建线程。
+说明：线程池的好处是减少在创建和销毁线程上所消耗的时间以及系统资源的开销，解决资源不足的问题。 如果不使用线程池，有可能造成系统创建大量同类线程而导致消耗完内存或者“过度切换”的问题。<br>
+【强制】线程池不允许使用 <code>Executors</code> 去创建，而是通过 <code>ThreadPoolExecutor</code> 的方式，这样的处理方式让写的同学更加明确线程池的运行规则，规避资源耗尽的风险。
+说明：<code>Executors</code> 返回的线程池对象的弊端如下：
+1） <code>FixedThreadPool</code> 和 <code>SingleThreadPool</code>： 允许的请求队列长度为 <code>Integer.MAX_VALUE</code>，可能会堆积大量的请求，从而导致OOM。
+2） <code>CachedThreadPool</code>： 允许的创建线程数量为 <code>Integer.MAX_VALUE</code>，可能会创建大量的线程，从而导致 OOM。</p>
+</blockquote>
+<p>自定义线程池代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">2</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">5</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">1L</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">SECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedBlockingQueue</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">3</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Executors</span><span class="p">.</span><span class="na">defaultThreadFactory</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>SpringBoot异步配置，自定义线程池代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@EnableAsync</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AsyncConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 线程空闲存活的时间 单位: TimeUnit.SECONDS
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">KEEP_ALIVE_TIME</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">60</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">60</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * CPU 核心数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CPU_COUNT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Runtime</span><span class="p">.</span><span class="na">getRuntime</span><span class="p">().</span><span class="na">availableProcessors</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 核心线程数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CORE_POOL_SIZE</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">CPU_COUNT</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 线程池最大容纳线程数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * IO密集型:即存在大量堵塞; 公式: CPU核心数量 / 1- 阻塞系数 (阻塞系统在 0.8~0.9 之间)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * CPU密集型: 需要大量运算,没有堵塞或很少有; 公式:CPU核心数量 + 1
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">IO_MAXIMUM_POOL_SIZE</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">CPU_COUNT</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="n">1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">9</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CPU_MAXIMUM_POOL_SIZE</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CPU_COUNT</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行写入请求时的线程池
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 线程池
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;iSaveTaskThreadPool&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Executor</span><span class="w"> </span><span class="nf">iSaveTaskThreadPool</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">getThreadPoolTaskExecutor</span><span class="p">(</span><span class="s">&#34;iSaveTaskThreadPool-&#34;</span><span class="p">,</span><span class="n">IO_MAXIMUM_POOL_SIZE</span><span class="p">,</span><span class="n">100000</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行读请求时的线程池
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 线程池
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;iQueryThreadPool&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Executor</span><span class="w"> </span><span class="nf">iQueryThreadPool</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">getThreadPoolTaskExecutor</span><span class="p">(</span><span class="s">&#34;iQueryThreadPool-&#34;</span><span class="p">,</span><span class="n">CPU_MAXIMUM_POOL_SIZE</span><span class="p">,</span><span class="n">10000</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 创建一个线程池对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param threadNamePrefix 线程名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param queueCapacity 堵塞队列长度
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param refusePolicy 拒绝策略
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ThreadPoolTaskExecutor</span><span class="w"> </span><span class="nf">getThreadPoolTaskExecutor</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">threadNamePrefix</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">maxPoolSize</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">queueCapacity</span><span class="p">,</span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="w"> </span><span class="n">refusePolicy</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ThreadPoolTaskExecutor</span><span class="w"> </span><span class="n">taskExecutor</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolTaskExecutor</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setCorePoolSize</span><span class="p">(</span><span class="n">CORE_POOL_SIZE</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setMaxPoolSize</span><span class="p">(</span><span class="n">maxPoolSize</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setKeepAliveSeconds</span><span class="p">(</span><span class="n">KEEP_ALIVE_TIME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setThreadNamePrefix</span><span class="p">(</span><span class="n">threadNamePrefix</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 拒绝策略; 既不会抛弃任务,也不会抛出异常,而是将某些任务回退到调用者,从而降低新任务的流量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setRejectedExecutionHandler</span><span class="p">(</span><span class="n">refusePolicy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 阻塞队列 长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setQueueCapacity</span><span class="p">(</span><span class="n">queueCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setWaitForTasksToCompleteOnShutdown</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setAwaitTerminationSeconds</span><span class="p">(</span><span class="n">60</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">initialize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">taskExecutor</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="线程池工作原理">线程池工作原理</h4>
+<p><img alt="线程池工作原理" src="/iblog/posts/annex/images/essays/%E7%BA%BF%E7%A8%8B%E6%B1%A0%E5%B7%A5%E4%BD%9C%E5%8E%9F%E7%90%86.png"></p>
+<p>在创建了线程池后，等待提交过来的任务请求，当调用<code>execute</code>方法添加一个请求任务时，线程池会做如下判断：</p>
+<ol>
+<li>如果当前运行的线程数小于<code>corePoolSize</code>，那么马上创建线程运行该任务。</li>
+<li>如果当前运行的线程数大于等于<code>corePoolSize</code>，那么该任务会被放入任务队列。</li>
+<li>如果这时候任务队列满了且正在运行的线程数还小于<code>maximumPoolSize</code>，那么要创建非核心线程立刻运行这个任务扩容。</li>
+<li>如果任务队列满了且正在运行的线程数等于<code>maximumPoolSize</code>，那么线程池会启动饱和拒绝策略来执行。</li>
+<li>随着时间的推移，业务量越来越少，线程池中出现了空闲线程。当一个线程无事可做超过一定的时间时，线程池会进行判断，如果当前运行的线程数大于<code>corePoolSize</code>，那么这个线程就被停掉，所以线程池的所有任务完成后它最终会收缩到<code>corePoolSize</code>的大小。</li>
+</ol>
+<h4 id="阻塞队列">阻塞队列</h4>
+<p>阻塞队列，顾名思义，首先它是一个队列，一个阻塞队列在数据结构中所起的作用：</p>
+<ul>
+<li>当阻塞队列是空时，从队列中获取元素的操作将会被阻塞。</li>
+<li>当阻塞队列是满时，往队列里添加元素的操作将会被阻塞。</li>
+</ul>
+<p><img alt="阻塞队列" src="/iblog/posts/annex/images/essays/%E9%98%BB%E5%A1%9E%E9%98%9F%E5%88%97%E7%BB%93%E6%9E%84.jpeg"></p>
+<p>在多线程编程中，阻塞队列扮演着重要角色，特别适用于生产者-消费者模式，确保线程之间的同步和有序执行。阻塞队列的本质是一种数据结构，用于存储待执行的任务。
+当任务提交给线程池时，如果核心线程已满或任务队列达到容量上限，新任务将被放入阻塞队列中，等待执行条件的满足。</p>
+<p>阻塞在多线程领域指的是线程因某些条件而暂停执行，一旦条件满足，线程会被自动唤醒继续执行。这种机制保证了线程池的任务按照预期顺序执行，有效地管理并发任务的执行流程。</p>
+<p>在Java中，常见的线程池阻塞队列包括：</p>
+<ul>
+<li><code>ArrayBlockingQueue</code>: 由数组结构组成的有界阻塞队列。它按照 FIFO（先进先出）的顺序对元素进行排序。</li>
+<li><code>LinkedBlockingQueue</code>: 由链表结构组成的有界（默认大小为 <code>Integer.MAX_VALUE</code>，大约21亿）阻塞队列。同样按照 FIFO 的顺序对元素进行排序。</li>
+<li><code>PriorityBlockingQueue</code>: 支持优先级排序的无界阻塞队列。元素按照它们的优先级顺序被处理，具有最高优先级的元素总是被队列中的下一个要处理的元素。</li>
+<li><code>DelayQueue</code>: 使用优先级队列实现的延迟无界阻塞队列。队列中的元素只有在其指定的延迟时间到达时才能被取出。</li>
+<li><code>SynchronousQueue</code>: 不存储元素的阻塞队列，每个插入操作必须等待一个对应的移除操作。用于直接传递任务的场景。</li>
+<li><code>LinkedTransferQueue</code>: 由链表结构组成的无界阻塞队列，支持生产者-消费者的传输机制。与其他队列不同，它支持优先级传输。</li>
+<li><code>LinkedBlockingDeque</code>: 由链表结构组成的双向阻塞队列。它支持在队列的两端进行插入和移除操作，是一种双端队列。</li>
+</ul>
+<p>当你自定义线程池时，选择合适的阻塞队列是非常重要的。阻塞队列就像一个存放任务的“箱子”，线程池中的任务先放到这里，然后线程池的线程再从这里取出来执行。
+如果你的系统可能会有很多任务一起提交，可以考虑用能存很多任务的队列，比如<code>LinkedBlockingQueue</code>。这样即使任务多了，也不会丢失。
+如果你的任务有优先级，比如有些任务比其他的更重要，那就选<code>PriorityBlockingQueue</code>。它会按照任务的优先级来决定哪个任务先执行。
+如果应用程序需要限制内存使用，并希望在达到容量限制时阻塞新任务提交，可以选择<code>ArrayBlockingQueue</code>。</p>
+<h4 id="线程池参数">线程池参数</h4>
+<p>在Java中，线程池的创建和管理通过<code>java.util.concurrent.ThreadPoolExecutor</code>类完成。理解这个类构造函数的参数可以帮助我们更好地配置和优化线程池的运行效果。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="nf">ThreadPoolExecutor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">corePoolSize</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="kt">int</span><span class="w"> </span><span class="n">maximumPoolSize</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="kt">long</span><span class="w"> </span><span class="n">keepAliveTime</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="n">TimeUnit</span><span class="w"> </span><span class="n">unit</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="n">BlockingQueue</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">workQueue</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="n">ThreadFactory</span><span class="w"> </span><span class="n">threadFactory</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="n">RejectedExecutionHandler</span><span class="w"> </span><span class="n">handler</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><ul>
+<li><code>corePoolSize</code>: 核心线程数。当提交一个新任务时，如果当前运行的线程少于<code>corePoolSize</code>，则即使有空闲的工作线程，也会创建一个新线程来执行任务。
+核心线程在<code>ThreadPoolExecutor</code>的生命周期内始终存活，除非设置了<code>allowCoreThreadTimeOut</code>。</li>
+<li><code>maximumPoolSize</code>：线程池能够容纳同时执行的最大线程数，此值必须大于等于1。当任务队列满时，如果当前运行的线程数少于<code>maximumPoolSize</code>，则会创建新的线程来执行任务。</li>
+<li><code>threadFactory</code>：线程工厂，一般用默认的即可。用于创建新线程，通常用来给线程设置名称、设置为守护线程等。</li>
+<li><code>workQueue</code>：任务队列，用于保存等待执行任务的队列。随着业务量的增多，线程开始慢慢处理不过来，这时候需要放到任务队列中去等待线程处理。</li>
+<li><code>rejectedExecutionHandler</code>：拒绝策略。如果业务越来越多，线程池首先会扩容，扩容后发现还是处理不过来，任务队列已经满了，处理被拒绝任务的策略。
+<ol>
+<li><code>AbortPolicy</code>: 默认拒绝策略；直接抛出<code>java.util.concurrent.RejectedExecutionException</code>异常，阻止系统的正常运行；</li>
+<li><code>CallerRunsPolicy</code>：调用这运行，一种调节机制，该策略既不会抛弃任务，也不会抛出异常，而是将某些任务回退到调用者，从而降低新任务的流量；</li>
+<li><code>DiscardOldestPolicy</code>：抛弃队列中等待最久的任务，然后把当前任务加入到队列中；</li>
+<li><code>DiscardPolicy</code>：直接丢弃任务，不给予任何处理也不会抛出异常；如果允许任务丢失，这是一种最好的解决方案；</li>
+</ol>
+</li>
+<li><code>keepAliveTime</code>：多余的空闲线程的存活时间。如果线程池扩容后，能处理过来，而且数据量并没有那么大，用最初的线程数量就能处理过来，剩下的线程被叫做空闲线程。
+<code>keepAliveTime</code>指的是当线程数超过<code>corePoolSize</code>时，多余的空闲线程在等待新任务到来之前可以存活的最长时间。如果设置为0，则超出核心线程数的空闲线程会立即终止。</li>
+<li><code>unit</code>：<code>keepAliveTime</code>参数的时间单位，可以是<code>TimeUnit.SECONDS</code>、<code>TimeUnit.MILLISECONDS</code>等。</li>
+</ul>
+<h4 id="合理配置线程池参数">合理配置线程池参数</h4>
+<p>合理配置线程池参数，可以分为以下两种情况：</p>
+<ul>
+<li>CPU密集型：CPU密集的意思是该任务需要大量的运算，而没有阻塞，CPU一直全速运行；CPU密集型任务配置尽可能少的线程数量：<code>参考公式：（CPU核数+1）</code></li>
+<li>IO密集型：即该任务需要大量的IO，即大量的阻塞；在IO密集型任务中使用多线程可以大大的加速程序运行，故需要多配置线程数：参考公式：<code>CPU核数/ (1-阻塞系数) 阻塞系数在0.8~0.9之间</code></li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取CPU核心数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">coreNum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Runtime</span><span class="p">.</span><span class="na">getRuntime</span><span class="p">().</span><span class="na">availableProcessors</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="cm">/*
+</span></span></span><span class="line"><span class="cl"><span class="cm">             * 1. IO密集型: CPU核数/ (1-阻塞系数) 阻塞系数在0.8~0.9之间
+</span></span></span><span class="line"><span class="cl"><span class="cm">             * 2. CPU密集型: CPU核数+1
+</span></span></span><span class="line"><span class="cl"><span class="cm">             */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//            int maximumPoolSize = coreNum + 1;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">maximumPoolSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">coreNum</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="n">1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">9</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前线程池最大允许存放：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">maximumPoolSize</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;个线程&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">2</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">maximumPoolSize</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">1L</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">SECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedBlockingQueue</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">3</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Executors</span><span class="p">.</span><span class="na">defaultThreadFactory</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="锁">锁</h2>
+<p>在Java中根据锁的特性来划分可以分为很多，锁的主要作用是确保多线程环境下的数据安全，从而保证程序的正确执行。
+在Java中具体&quot;锁&quot;的实现，通常可以归纳为三种，使用<code>synchronized</code>关键字、调用<code>juc.locks</code>包下相关接口、使用<code>CAS</code>思想。</p>
+<table>
+<thead>
+<tr>
+<th>锁的类型与概念</th>
+<th>描述</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>公平锁</td>
+<td>线程按照请求的顺序获取锁。</td>
+</tr>
+<tr>
+<td>非公平锁</td>
+<td>线程获取锁的顺序不受控制，有可能插队。</td>
+</tr>
+<tr>
+<td>可重入锁</td>
+<td>允许同一个线程多次获取同一把锁，避免死锁。</td>
+</tr>
+<tr>
+<td>不可重入锁</td>
+<td>不允许同一个线程多次获取同一把锁。</td>
+</tr>
+<tr>
+<td>共享锁</td>
+<td>多个线程可以同时获取同一把锁。</td>
+</tr>
+<tr>
+<td>独占锁</td>
+<td>同一时间只允许一个线程获取该锁。</td>
+</tr>
+<tr>
+<td>悲观锁</td>
+<td>假设会有并发冲突，每次操作时都加锁。</td>
+</tr>
+<tr>
+<td>乐观锁</td>
+<td>假设不会有并发冲突，操作时不加锁，提交时检查是否冲突。</td>
+</tr>
+<tr>
+<td>偏向锁</td>
+<td>当只有一个线程访问同步块时，为该线程加锁，减少获取锁的操作成本。</td>
+</tr>
+<tr>
+<td>轻量级锁</td>
+<td>针对竞争不激烈的情况下进行优化，通过CAS操作来避免互斥。</td>
+</tr>
+<tr>
+<td>重量级锁</td>
+<td>竞争激烈时，锁的持有和释放会导致线程阻塞和唤醒。</td>
+</tr>
+<tr>
+<td>可中断锁</td>
+<td>允许在等待锁的过程中可以响应中断信号。</td>
+</tr>
+<tr>
+<td>互斥锁</td>
+<td>控制对共享资源的访问，同一时间只有一个线程可以获取锁。</td>
+</tr>
+<tr>
+<td>死锁</td>
+<td>几个线程因互相持有对方所需的资源而无法继续执行的状态。</td>
+</tr>
+</tbody>
+</table>
+<h3 id="公平锁与非公平锁">公平锁与非公平锁</h3>
+<p>根据线程获取锁的顺序来划分可分为公平锁和非公平锁。</p>
+<ul>
+<li>公平锁：公平锁是指多个线程按照申请锁的顺序来获取锁。即先到先得的原则，先请求锁的线程会先获取到锁，后到的线程会排队等待。
+优点是等待锁的线程不会饿死。缺点是整体吞吐效率相对非公平锁要低，等待队列中除第一个线程以外的所有线程都会阻塞，CPU唤醒阻塞线程的开销比非公平锁大。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">fairLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w"> </span><span class="c1">// true 表示使用公平锁</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>非公平锁：非公平锁是指多个线程获取锁的顺序是不确定的，是随机竞争的。即线程获取锁的顺序是不固定的，有可能新来的线程比等待时间长的线程先获取到锁。
+优点是可以通过减少线程切换的开销来提高并发性能，整体的吞吐效率高。缺点是处于等待队列中的线程可能会饿死，或者等很久才会获得锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">nonfairLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w"> </span><span class="c1">// false 表示使用非公平锁（默认）</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>通常情况下，如果不特别需要公平性，非公平锁能够提供更高的性能。但是在某些需要严格控制线程执行顺序的场景下，公平锁可能更为适合。
+在Java中公平锁和非公平锁的实现为<code>ReentrantLock</code>、<code>synchronized</code>。
+其中<code>synchronized</code>是非公平锁，<code>ReentrantLock</code>默认是非公平锁，但是可以指定<code>ReentrantLock</code>的构造函数创建公平锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an instance of {@code ReentrantLock}.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * This is equivalent to using {@code ReentrantLock(false)}.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">ReentrantLock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sync</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NonfairSync</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an instance of {@code ReentrantLock} with the
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * given fairness policy.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @param fair {@code true} if this lock should use a fair ordering policy
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">ReentrantLock</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">fair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sync</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fair</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FairSync</span><span class="p">()</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NonfairSync</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="可重入锁与不可重入锁">可重入锁与不可重入锁</h3>
+<p>根据一个线程是否可以多次获得同一把锁来划分，可分为可重入锁和不可重入锁。</p>
+<ul>
+<li>可重入锁：可重入锁是指同一个线程在外层方法获取锁之后，在内层方法仍然能够获取该锁的锁。即同一个线程可以多次获得同一把锁，可重入锁最大的作用就是避免死锁。所以可重入锁又叫做递归锁。</li>
+<li>不可重入锁：所谓不可重入锁，就是与可冲入锁作用相悖；不可重入锁是指一个线程在持有锁的情况下再次请求锁时，会被阻塞或导致死锁。即同一个线程不能多次获得同一把锁。</li>
+</ul>
+<p>举个例子，当你进入你家时门外会有锁，进入房间后厨房卫生间都可以随便进出，这个叫可重入锁。当你进入房间时，发现厨房、卫生间都上锁而且你拿不到钥匙，这个叫不可重入锁。
+在Java中<code>ReentrantLock</code>和<code>synchronized</code>都是可重入锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReentrantExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">outerMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Outer method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">innerMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">innerMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Inner method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReentrantExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">example</span><span class="p">.</span><span class="na">outerMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReentrantLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">outerMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Outer method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">innerMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">innerMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Inner method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReentrantLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">example</span><span class="p">.</span><span class="na">outerMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="共享锁与独占锁">共享锁与独占锁</h3>
+<p>根据锁的访问权限可划分为共享锁和独占锁。</p>
+<ul>
+<li>独占锁：独占锁又称排它锁，指一次只能有一个线程获得锁，其他所有尝试获取锁的线程都会被阻塞，直到持有锁的线程释放锁。
+只有一个线程能访问受保护的资源，从而确保资源的独占访问，适用于写操作等需要完全独占资源的场景。</li>
+<li>共享锁：共享锁允许多个线程同时获得锁，多个线程可以并发地访问受保护的资源。适用于读操作等可以并发访问的场景。
+多个线程可以同时持有锁，但如果某个线程需要进行写操作，则必须等到所有持有共享锁的线程释放锁。</li>
+</ul>
+<p>在Java中，对于<code>ReentrantLock</code>和<code>synchronized</code>都是独占锁。对于<code>ReentrantReadWriteLock</code>其读锁是共享锁而写锁是独占锁，读锁的共享可保证并发读是非常高效的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SharedLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="w"> </span><span class="n">rwLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="p">.</span><span class="na">ReadLock</span><span class="w"> </span><span class="n">readLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rwLock</span><span class="p">.</span><span class="na">readLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="p">.</span><span class="na">WriteLock</span><span class="w"> </span><span class="n">writeLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rwLock</span><span class="p">.</span><span class="na">writeLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">readMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">readLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the read lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// Read-only critical section</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">readLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; released the read lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">writeLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the write lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// Write critical section</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; released the write lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SharedLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SharedLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">readTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">readMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">writeTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">writeMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">t1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">readTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">t2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">readTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">t3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">writeTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">t1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">t2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">t3</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="悲观锁与乐观锁">悲观锁与乐观锁</h3>
+<p>根据对数据并发访问来划分，可分为悲观锁和乐观锁。乐观锁与悲观锁是一种广义上的概念，可以理解为一种标准类似于Java中的接口。</p>
+<ul>
+<li>对于多线程并发操作，加了悲观锁的线程认为每一次修改数据时都会有其他线程来跟它一起修改数据，所以在修改数据之前先会加锁，确保其他线程不会修改该数据。
+由于悲观锁在修改数据前先加锁的特性，能保证写操作时数据正确，所以悲观锁更适合写多读少的场景。</li>
+<li>乐观锁则与悲观锁相反，每一次修改数据时，都认为没有其他线程来跟它一起修改，所以在修改数据之前不会去添加锁，如果这个数据没有被更新，当前线程将自己修改的数据成功写入。如果数据已经被其他线程更新，则根据不同的实现方式执行不同的操作。
+由于乐观锁是一种无锁操作，所以在使用乐观锁的场景中读的性能会大幅度提升，适合读多写少。</li>
+</ul>
+<p>在Java中悲观锁的实现有，<code>synchronized</code>、<code>Lock</code>实现类，乐观锁的实现有<code>CAS</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SynchronizedExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SynchronizedExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SynchronizedExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Count: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">example</span><span class="p">.</span><span class="na">getCount</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">existingValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">count</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">existingValue</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">count</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">existingValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">count</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CASExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CASExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Count: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">example</span><span class="p">.</span><span class="na">getCount</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="自旋锁与适应性自旋锁">自旋锁与适应性自旋锁</h3>
+<p>自旋锁是一种特殊的锁，它不会让线程立即阻塞。
+当一个线程尝试获取某个锁时，如果该锁已被其他线程占用，就一直循环检测锁是否被释放，而不是进入线程挂起或睡眠状态，直到获取到某个锁超过一定的自旋次数后才会阻塞线程。
+自旋锁本身是有缺点的，它不能代替阻塞。如果锁被占用的时间很长，那么自旋的线程只会白白浪费处理器资源，带来性能上的浪费，所以使用自旋锁时需要根据具体的应用场景来权衡其利弊。</p>
+<p>在Java中，可以使用<code>java.util.concurrent.atomic</code>包下的原子类来实现自旋锁，其中<code>AtomicInteger</code>常被用来实现简单的自旋锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SpinLock</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">lock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 自旋等待获取锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">locked</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取到锁后，将 locked 设置为 true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unlock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 释放锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SpinLock</span><span class="w"> </span><span class="n">spinLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SpinLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">spinLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread 1 in critical section&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟临界区代码执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spinLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">spinLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread 2 in critical section&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟临界区代码执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spinLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为什么要使用自旋锁？在许多场景中，同步资源的锁定时间很短，为了这一小段时间去切换线程，线程挂起和恢复现场的花费可能会让系统得不偿失。
+简单来说就是，避免切换线程带来的开销。自旋等待虽然避免了线程切换的开销，但它要占用处理器时间。如果锁被占用的时间很短，自旋等待的效果就会非常好。
+反之，如果锁被占用的时间很长，那么自旋的线程只会白浪费处理器资源。所以自旋等待的时间必须要有一定的限度，如果自旋超过了限定次数（默认是10次，可以使用<code>-XX:PreBlockSpin</code>来更改）没有成功获得锁，就应当挂起线程。</p>
+<blockquote>
+<p>自旋锁在JDK 1.4中引入，默认关闭，但是可以使用<code>-XX:+UseSpinning</code>开启。在JDK1.6中默认开启，同时自旋的默认次数为10次，可以通过参数<code>-XX:PreBlockSpin</code>来调整。</p>
+</blockquote>
+<p>如果通过参数<code>-XX:PreBlockSpin</code>来调整自旋锁的自旋次数会带来诸多不便。假如将参数调整为10，但是系统很多线程都是等你刚刚退出的时候就释放了锁，假如多自旋一两次就可以获取锁。于是JDK1.6引入适应性自旋锁。</p>
+<p>适应性自旋锁是对自旋的升级、优化，自旋的时间不再固定，它根据当前锁的使用情况动态调整自旋等待时间。
+如果在同一个锁对象上，自旋等待刚刚成功获得过锁，并且持有锁的线程正在运行中，那么虚拟机就会认为这次自旋也是很有可能再次成功，进而它将允许自旋等待持续相对更长的时间。
+如果对于某个锁，自旋很少成功获得过，那在以后尝试获取这个锁时将可能省略掉自旋过程，直接阻塞线程，避免浪费处理器资源。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AdaptiveSpinLock</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">MIN_SPIN_COUNT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">MAX_SPIN_COUNT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AtomicBoolean</span><span class="w"> </span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicBoolean</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">spinCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MIN_SPIN_COUNT</span><span class="p">;</span><span class="w"> </span><span class="c1">// 初始自旋等待次数设定为最小值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">lock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">spins</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">spinCount</span><span class="p">;</span><span class="w"> </span><span class="c1">// 获取当前自旋次数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">locked</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">false</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">spins</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAX_SPIN_COUNT</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spins</span><span class="o">++</span><span class="p">;</span><span class="w"> </span><span class="c1">// 自旋次数递增</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 在真实场景中，可能需要添加短暂的延时，避免过多占用CPU资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">spins</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">onSpinWait</span><span class="p">();</span><span class="w"> </span><span class="c1">// 在Java 9及以上版本中，可以使用Thread.onSpinWait()来优化自旋等待</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">spinCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">spins</span><span class="p">;</span><span class="w"> </span><span class="c1">// 更新自旋次数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unlock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">locked</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AdaptiveSpinLock</span><span class="w"> </span><span class="n">spinLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AdaptiveSpinLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">spinLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread 1 in critical section&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟临界区代码执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spinLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">spinLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread 2 in critical section&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟临界区代码执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spinLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="偏向锁">偏向锁</h3>
+<p>偏向锁是Java中针对加锁操作进行的一种优化机制，主要针对只有一个线程访问同步块的场景。它的设计初衷是在无竞争的情况下，减少不必要的同步原语的性能消耗。</p>
+<blockquote>
+<p>《深入理解Java虚拟机》对偏向锁的解释：
+<code>Hotspot</code> 的作者经过以往的研究发现大多数情况下锁不仅不存在多线程竞争，而且总是由同一线程多次获得，为了让线程获得锁的代价更低而引入了偏向锁。
+当一个线程访问同步块并获取锁时，会在对象头和栈帧中的锁记录里存储锁偏向的线程 ID，以后该线程在进入和退出同步块时不需要花费CAS操作来加锁和解锁，而只需简单的测试一下对象头的 <code>MarkWord</code> 里是否存储着指向当前线程的偏向锁，如果测试成功，表示线程已经获得了锁，如果测试失败，则需要再测试下 <code>MarkWord</code> 中偏向锁的标识是否设置成 1（表示当前是偏向锁），如果没有设置，则使用 CAS 竞争锁，如果设置了，则尝试使用CAS将对象头的偏向锁指向当前线程。</p>
+</blockquote>
+<p>之所以叫偏向锁是因为偏向于第一个获取到他的线程，如果在程序执行中该锁没有被其他的线程获取，则持有偏向锁的线程将永远不需要再进行同步。
+但是如果线程间存在锁竞争，偏向锁会失效，此时会涉及到锁的撤销，将锁状态升级为适合多线程竞争的轻量级锁或者重量级锁，这个过程可能会引入额外的开销，影响性能。</p>
+<p>当一个线程访问同步块时，首先会尝试获取偏向锁。如果同步块之前没有被其他线程锁定，当前线程会尝试获取偏向锁，并将对象头的标记位设置为偏向锁。
+如果其他线程尝试访问该同步块，会检测到该同步块已经被偏向锁定，会尝试撤销偏向锁，升级为轻量级锁或者重量级锁。
+如果偏向线程已经不再访问该同步块，那么该对象头的标记位会被设置成无锁状态，接着是无锁状态。</p>
+<h3 id="轻量级锁与重量级锁">轻量级锁与重量级锁</h3>
+<p>根据锁的竞争情况来划分可以分为重量级锁和轻量级锁。</p>
+<ul>
+<li>重量级锁：重量级锁适用于多线程竞争激烈的情况下，它的实现通常依赖于操作系统的底层特性，重量级锁会导致线程堵塞。传统的重量级锁，使用的是系统互斥量实现的。</li>
+<li>轻量级锁：相对于重量级锁而言的。轻量级锁适用于多线程竞争不激烈的情况下，它的设计目标是在减少传统重量级锁在竞争时带来的性能损耗。</li>
+</ul>
+<p>在Java中轻量级锁的经典实现是CAS中的自旋锁。优点是竞争的线程不会阻塞，提高了程序的响应速度；缺点是如果始终得不到锁竞争的线程，使用自旋会消耗CPU。所以轻量级锁适合，追求响应时间，同步块执行速度非常快的场景。
+重量级锁依赖于操作系统提供的底层同步机制。优点是线程竞争不使用自旋，不会消耗CPU；缺点是当多个线程竞争同一个锁时，会直接阻塞等待，直到获取到锁的线程释放锁资源。适合追求吞吐量、同步块执行时间较长也就是线程竞争激烈的场景。</p>
+<p>轻量级锁不是在任何情况下都比重量级锁快的，要看同步块执行期间有没有多个线程抢占资源的情况。如果有，那么轻量级线程要承担CAS+互斥锁的性能消耗，就会比重量锁执行的更慢。</p>
+<h3 id="可中断锁">可中断锁</h3>
+<p>可中断锁顾名思义，就是可以中断的锁。
+如果某一线程A正在执行锁中的代码，另一线程B正在等待获取该锁，可能由于等待时间过长，线程B不想等待了，想先处理其他事情，我们可以让它中断自己或者在别的线程中中断它，这种就是可中断锁。</p>
+<p>在Java中<code>synchronized</code>就是不可中断锁，<code>Lock</code>是可中断锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SynchronizedExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">5000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟线程持有锁的操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;Thread-1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;Thread-2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 让Thread-1先获取锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 等待线程执行完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">LockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">5000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟线程持有锁的操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;Thread-1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">.</span><span class="na">tryLock</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// 可中断地尝试获取锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; unable to acquire the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;Thread-2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 让Thread-1先获取锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 等待线程执行完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="互斥锁">互斥锁</h3>
+<p>互斥锁是一种用于多线程编程中的同步原语，用于确保在任何时刻，只有一个线程可以访问共享资源，从而避免数据竞争和并发访问的冲突。
+在编程中，引入了对象互斥锁的概念，来保证共享数据操作的完整性。每个对象都对应于一个可称为&quot;互斥锁&quot;的标记，这个标记用来保证在任一时刻，只能有一个线程访问该对象。</p>
+<p>互斥锁在访问共享资源之前对对象进行加锁操作，在访问完成之后进行解锁操作。加锁后，任何其他试图再次加锁的线程会被阻塞，直到当前线程解锁其他线程才能访问公共资源。
+如果在解锁时有多个线程在等待获取锁，一旦锁被释放，它们将竞争重新获取锁。只有第一个竞争到锁的线程会变为就绪状态并开始执行，其他线程将继续等待。</p>
+<p>在Java里最基本的互斥手段就是使用<code>synchronized</code>关键字、<code>ReentrantLock</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SynchronizedMutexExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Counter: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="死锁">死锁</h3>
+<p>死锁并不是Java程序中通俗意义上的&quot;锁&quot;，而是程序中出现的一种问题。之所以放到“锁”这个标题下是为了方便类比，就类似谐音梗吧。</p>
+<p>死锁是指两个或多个线程在执行过程中，由于竞争资源或者互相等待释放资源而造成的一种僵局，使得所有参与的线程无法继续执行。
+举个例子，当线程A持有锁a并尝试获取锁b，线程B持有锁b并尝试获取锁a时，就会出现死锁。简单来说，死锁问题的产生是由两个或者以上线程并行执行的时候，争夺资源而互相等待造成的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;lockA&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;lockB&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadHolderLock</span><span class="p">(</span><span class="n">lockA</span><span class="p">,</span><span class="n">lockB</span><span class="p">),</span><span class="s">&#34;线程AAA&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadHolderLock</span><span class="p">(</span><span class="n">lockB</span><span class="p">,</span><span class="n">lockA</span><span class="p">),</span><span class="s">&#34;线程BBB&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="kd">class</span> <span class="nc">ThreadHolderLock</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Runnable</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">public</span><span class="w"> </span><span class="nf">ThreadHolderLock</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">this</span><span class="p">.</span><span class="na">lockA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lockA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">this</span><span class="p">.</span><span class="na">lockB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lockB</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lockA</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 持有锁 &#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockA</span><span class="o">+</span><span class="s">&#34;, 尝试获得&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockB</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                 </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                 </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lockB</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                 </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 持有锁 &#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockB</span><span class="o">+</span><span class="s">&#34;, 尝试获得&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockA</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用资源有序分配法避免死锁">使用资源有序分配法避免死锁</h4>
+<p>想要如何避免死锁，就要弄清楚死锁出现的原因，造成死锁必须达成的4个条件：</p>
+<ul>
+<li>互斥条件：一个资源每次只能被一个线程使用。例如，如果线程 A 已经持有的资源，不能再同时被线程 B 持有，如果线程 B 请求获取线程 A 已经占用的资源，那线程 B 只能等待，直到线程 A 释放了资源。</li>
+<li>请求与保持条件：一个线程因请求资源而阻塞时，对已获得的资源保持不放。例如，当线程 A 已经持有了资源 1，又想申请资源 2，而资源 2 已经被线程 C 持有了，所以线程 A 就会处于等待状态，但是线程 A 在等待资源 2 的同时并不会释放自己已经持有的资源 1。</li>
+<li>不剥夺条件：线程已获得的资源，在未使用完之前，不能强行剥夺。例如，当线程A已经持有了资源 ，在自己使用完之前不能被其他线程获取，线程 B 如果也想使用此资源，则只能在线程 A 使用完并释放后才能获取。</li>
+<li>循环等待条件：若干线程之间形成一种头尾相接的循环等待资源关系。比如，线程 A 已经持有资源 2，而想请求资源 1， 线程 B 已经获取了资源 1，而想请求资源 2，这就形成资源请求等待的环。</li>
+</ul>
+<p>避免死锁的产生就只需要破环其中一个条件就可以，最常见的并且可行的就是使用资源有序分配法，来破循环等待条件。
+资源有序分配法指的是，线程 A 和 线程 B 获取资源的顺序要一样，当线程 A 先尝试获取资源 A，然后尝试获取资源 B 的时候，线程 B 同样也是先尝试获取资源 A，然后尝试获取资源 B。也就是说，线程 A 和 线程 B 总是以相同的顺序申请自己想要的资源。
+给资源分配一个全局的唯一编号，进程必须按资源编号的顺序请求资源。这种方法可以避免循环等待，从而防止死锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Resource</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Resource</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Process</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="w"> </span><span class="n">resources</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Process</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">resources</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">resources</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquireResources</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 模拟处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">releaseResources</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">acquireResources</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Resource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired Resource &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">resource</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">releaseResources</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Resource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; released Resource &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">resource</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ResourceOrderingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource1</span><span class="p">,</span><span class="w"> </span><span class="n">resource2</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource2</span><span class="p">,</span><span class="w"> </span><span class="n">resource3</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource3</span><span class="p">,</span><span class="w"> </span><span class="n">resource1</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process3</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用银行家算法避免死锁">使用银行家算法避免死锁</h4>
+<p><img alt="银行家算法" src="/iblog/posts/annex/images/essays/%E9%93%B6%E8%A1%8C%E5%AE%B6%E7%AE%97%E6%B3%95.png"></p>
+<p>银行家算法：一个避免死锁的著名算法，是由艾兹格·迪杰斯特拉在1965年为T.H.E系统设计的一种避免死锁产生的算法。它以银行借贷系统的分配策略为基础，判断并保证系统的安全运行。</p>
+<p>在银行中，客户申请贷款的数量是有限的，每个客户在第一次申请贷款时要声明完成该项目所需的最大资金量，在满足所有贷款要求时，客户应及时归还。银行家在客户申请的贷款数量不超过自己拥有的最大值时，都应尽量满足客户的需要。通过判断借贷是否安全，然后决定借不借。
+举例，现有公司B、公司A、公司T，想要从银行分别贷款70亿、40亿、50亿，假设银行只有100亿供放贷，如果借不到企业最大需求的钱，钱将不会归还，怎么才能合理的放贷？</p>
+<table>
+<thead>
+<tr>
+<th>公司</th>
+<th>最大需求</th>
+<th>已借走</th>
+<th>最多还借</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>B</td>
+<td>70</td>
+<td>20</td>
+<td>50</td>
+</tr>
+<tr>
+<td>A</td>
+<td>40</td>
+<td>10</td>
+<td>30</td>
+</tr>
+<tr>
+<td>T</td>
+<td>50</td>
+<td>30</td>
+<td>20</td>
+</tr>
+</tbody>
+</table>
+<p>此时公司B、A、T已经从银行借走60亿，银行还剩40亿。此时银行可放贷金额组合：</p>
+<ul>
+<li>借给公司B10亿、公司A10亿、公司T20亿，等待公司T还钱再将10亿借给公司A，等待公司A还钱，再将钱借给公司B；</li>
+<li>借给公司T20亿，等公司T还钱再将钱借给公司A，等待公司A还钱再将钱借给公司B；</li>
+<li>借给公司A10亿，等待公司A还钱再将钱借给公司T，公司T还钱再将钱借给公司B；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Banker</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="p">;</span><span class="w">  </span><span class="c1">// 系统可用资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="p">;</span><span class="w">  </span><span class="c1">// 每个进程的最大资源需求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">allocation</span><span class="p">;</span><span class="w"> </span><span class="c1">// 每个进程当前已分配的资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">need</span><span class="p">;</span><span class="w">      </span><span class="c1">// 每个进程剩余的资源需求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Banker</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">available</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">maximum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">numProcesses</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">numResources</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">allocation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">numProcesses</span><span class="o">][</span><span class="n">numResources</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">need</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">numProcesses</span><span class="o">][</span><span class="n">numResources</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">numProcesses</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">numResources</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">need</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// 初始时，Need等于Maximum</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 请求资源的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">requestResources</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isRequestValid</span><span class="p">(</span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="n">request</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 请求不合法，拒绝请求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 试探性分配</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">allocation</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 安全性检查</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">safe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">isSafeState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">safe</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果不安全，恢复试探性分配前的状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">allocation</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">safe</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isRequestValid</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">request</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 请求超出需求或可用资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isSafeState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">work</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">finish</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">allocation</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">found</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">allocation</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">finish</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">canProceed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">work</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">need</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">work</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">canProceed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">canProceed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">work</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">work</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">allocation</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">finish</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">found</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">found</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">finish</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">f</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 存在未完成的进程，系统不安全</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w"> </span><span class="c1">// 所有进程都完成，系统安全</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BankerExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Banker</span><span class="w"> </span><span class="n">banker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Banker</span><span class="p">(</span><span class="n">available</span><span class="p">,</span><span class="w"> </span><span class="n">maximum</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">request1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 1 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">request2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 2 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">request3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 3 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用trylock进行超时锁定">使用tryLock进行超时锁定</h4>
+<p>使用 <code>java.util.concurrent.locks.ReentrantLock</code> 的 <code>tryLock</code>方法可以尝试获取锁，并设置超时时间，避免长时间等待造成的死锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Process</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Process</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock1</span><span class="p">.</span><span class="na">tryLock</span><span class="p">(</span><span class="n">50</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock2</span><span class="p">.</span><span class="na">tryLock</span><span class="p">(</span><span class="n">50</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired both locks&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="c1">// 模拟处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">lock2</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">lock1</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 等待一段时间再重试</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">50</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TryLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">,</span><span class="w"> </span><span class="n">lock1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="java内存模型">Java内存模型</h2>
+<p><a href="http://www.cs.umd.edu/~pugh/java/memoryModel/jsr133.pdf">Java内存模型</a>，即JMM（Java Memory Model）本身是一种抽象的概念，并不真实存在。
+它定义了Java程序中多线程间如何通过内存进行交互的规则和规范。屏蔽了各种硬件和操作系统的访问差异的，保证了Java程序在各种平台下对内存的访问都能保证效果一致的机制及规范。
+JMM规定了变量的读取和写入如何在主内存和各线程的工作内存之间进行，保证了并发编程的<strong>原子性</strong>、<strong>可见性</strong>及<strong>有序性</strong>。
+内存模型解决并发问题主要采用两种方式，<strong>限制处理器优化</strong>和使用<strong>内存屏障</strong>。</p>
+<p><img alt="Java内存模型" src="/iblog/posts/annex/images/essays/Java%E5%86%85%E5%AD%98%E6%A8%A1%E5%9E%8B.jpg"></p>
+<h3 id="原子性">原子性</h3>
+<p>原子性指的是一个操作或一组操作在执行时不可被中断，即这些操作要么全部完成，要么全部不完成。
+在Java中，为了保证原子性，提供了两个高级的字节码指令 <code>monitorenter</code> 和 <code>monitorexit</code>。对应的就是Java中的关键字 <code>synchronized</code>，在Java中只要被<code>synchronized</code>修饰就能保证原子性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="可见性">可见性</h3>
+<p>可见性指的是一个线程对共享变量的修改，能够及时被其他线程看到。Java提供了<code>volatile</code>关键字和<code>synchronized</code>关键字来保证变量的可见性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SharedData</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setFlag</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">getFlag</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">flag</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="有序性">有序性</h3>
+<p>有序性指的是程序的执行顺序按照代码的顺序执行，编译器和处理器可能会进行优化，但这些优化不会影响单线程的语义。
+在Java中，可以使用<code>synchronized</code>和<code>volatile</code>来保证多线程之间操作的有序性。其中<code>volatile</code> 关键字会禁止编译器指令重排，来保证。
+<code>synchronized</code> 关键字保证同一时刻只允许一条线程操作，而不能禁止指令重排，指令重排并不会影响单线程的顺序，它影响的是多线程并发执行的顺序性，从而保证了有序性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Example</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">write</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">           </span><span class="c1">// 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">     </span><span class="c1">// 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">read</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">      </span><span class="c1">// 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="p">);</span><span class="w"> </span><span class="c1">// 4</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在多线程环境下，Java语句可能会不按照顺序执行，所以要注意数据的依赖性。计算机在执行程序时，为了提高性能，编译器和处理器常常会做指令重排，一把分为以下两种：</p>
+<ul>
+<li>单线程环境里面确保程序最终执行结果和代码顺序执行的结果一致。处理器在进行重新排序是必须要考虑指令之间的数据依赖；</li>
+<li>多线程环境中线程交替执行，由于编译器优化重排的存在，两个线程使用的变量能否保持一致性是无法确定的，结果无法预测；</li>
+</ul>
+<h3 id="限制处理器优化">限制处理器优化</h3>
+<p>处理器和编译器为了提高执行效率，会对指令进行优化重排序。虽然这种优化不会影响单线程程序的执行结果，但在多线程环境下可能导致意外的行为。
+Java 内存模型通过以下方式限制处理器和编译器的优化：</p>
+<ul>
+<li><code>volatile</code>关键字：声明为<code>volatile</code>的变量会被直接写入主内存，并且在读取时直接从主内存中读取。<code>volatile</code> 禁止了指令重排序，保证了变量的可见性和有序性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>synchronized</code> 关键字：进入同步块时，会触发获取锁的操作，这会刷新线程的工作内存，从主内存中读取最新值；退出同步块时，会触发释放锁的操作，这会将工作内存中的值写回主内存。
+<code>synchronized</code> 也禁止了指令重排序，保证了变量的原子性和可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="内存屏障">内存屏障</h3>
+<p>内存屏障，也称为内存栅栏，是一种用于防止处理器和编译器对内存操作进行重排序的指令。
+内存屏障通过插入特殊的指令来强制某些操作的顺序执行，从而确保多线程环境下的正确性。Java内存模型在底层实现中使用了内存屏障来保证内存操作的有序性和可见性。</p>
+<p>内存屏障主要分为四种类型，在Java中内存屏障被隐式地应用于某些关键字和类中，用来确保线程安全和内存可见性。</p>
+<ol>
+<li><code>LoadLoad</code>屏障：确保在该屏障之前的所有 <code>load</code> 操作都完成后，才能执行该屏障后面的 <code>load</code> 操作。这种屏障保证了前面的 <code>load</code> 操作对后面的 <code>load</code> 操作的可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">SharedData data = ...;  // 获取共享对象的引用
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">while (!data.flag) {
+</span></span><span class="line"><span class="cl">    // 使用 LoadLoad 屏障保证可见性
+</span></span><span class="line"><span class="cl">    // 在这里插入 LoadLoad 屏障确保读取到最新的 flag 值
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// 使用 LoadLoad 屏障保证可见性
+</span></span><span class="line"><span class="cl">int result = data.x;  // 3. Load 操作
+</span></span></code></pre></div></li>
+<li><code>StoreStore</code>屏障：保证在该屏障之前的所有 <code>store</code> 操作都完成后，才能执行该屏障后面的 <code>store</code> 操作。这确保了前面的 <code>store</code> 操作对后面的 <code>store</code> 操作的可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">data.x = 42;        // 1. Store 操作
+</span></span><span class="line"><span class="cl">// 使用 StoreStore 屏障确保顺序性
+</span></span><span class="line"><span class="cl">data.flag = true;   // 2. Store 操作
+</span></span></code></pre></div></li>
+<li><code>LoadStore</code>屏障：确保在该屏障之前的所有 <code>load</code> 操作都完成后，才能执行该屏障后面的 <code>store</code> 操作。这种屏障保证了前面的 <code>load</code> 操作对后面的 <code>store</code> 操作的可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">while (!data.flag) {
+</span></span><span class="line"><span class="cl">    // Spin until flag is true
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// 使用 LoadStore 屏障保证顺序性
+</span></span><span class="line"><span class="cl">int result = data.x;  // 3. Load 操作
+</span></span></code></pre></div></li>
+<li><code>StoreLoad</code>屏障：保证在该屏障之前的所有 <code>store</code> 操作都完成后，才能执行该屏障后面的 <code>load</code> 操作。这确保了前面的 <code>store</code> 操作对后面的 <code>load</code> 操作的可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">data.x = 42;        // 1. Store 操作
+</span></span><span class="line"><span class="cl">// 使用 StoreLoad 屏障保证可见性
+</span></span><span class="line"><span class="cl">data.flag = true;   // 2. Store 操作
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 在另一个线程 B 中
+</span></span><span class="line"><span class="cl">while (!data.flag) {
+</span></span><span class="line"><span class="cl">    // Spin until flag is true
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">int result = data.x;  // 3. Load 操作
+</span></span></code></pre></div></li>
+</ol>
+<h3 id="happens-before">Happens-Before</h3>
+<p>&ldquo;Happens-Before&quot;原则是Java内存模型中的一个核心概念，用来定义多个线程之间操作的执行顺序和内存可见性。
+如果一个操作A在另一个操作B之前，那么在内存模型中，A的所有操作结果对于B是可见的，并且A的执行顺序在B之前。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ProgramOrderExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">example</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">    </span><span class="c1">// 1. Happens-Before</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// 2. Happens-Before</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>需要注意的是两个操作之间存在Happens-Before关系，并不意味着Java的具体实现必须要按照Happens-Before关系指定的顺序来执行。
+如果重排序之后的执行结果，与按Happens-Before关系来执行的结果一致，那么JMM允许这种重排序。JMM只要求在最终的执行结果上保持与Happens-Before关系一致的语义。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HappensBeforeExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">         </span><span class="c1">// Statement 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">   </span><span class="c1">// Statement 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">    </span><span class="c1">// Statement 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;x = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">x</span><span class="p">);</span><span class="w">  </span><span class="c1">// Statement 4</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;flag is false&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>根据Happens-Before规则：</p>
+<ul>
+<li>Statement 1 在 Statement 2 之前执行，因此 <code>x = 1</code> 的操作 Happens-Before <code>flag = true</code> 的操作。</li>
+<li>Statement 2 在 Statement 3 之前执行，因此 <code>flag = true</code> 的操作 Happens-Before <code>if (flag)</code> 的操作。</li>
+</ul>
+<p>如果<code>thread2</code>观察到<code>flag</code>的值为<code>true</code>，则说明 Happens-Before 原则保证了在此之前的操作结果对于其他线程是可见的。但是只要不改变程序的最终执行结果和Happens-Before关系，Java内存模型允许编译器和处理器进行指令重排序。
+<code>thread1</code>可能会将<code>flag</code>设置 <code>true</code>之后才设置 <code>x</code> 的值为<code>1</code>。这种情况下，<code>thread2</code>在检查<code>flag</code>之后，可能会观察到 <code>x = 1</code>。
+这种情况仍然满足Happens-Before关系，尽管发生了重排序。</p>
+<p>&ldquo;Happens-Before&quot;原则在Java内存模型中包含8条具体的规则：</p>
+<ol>
+<li>程序顺序规则。在一个线程内，按照程序代码的顺序执行，前面的操作总是先于后面的操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int a = 1;   // 1. Happens-Before
+</span></span><span class="line"><span class="cl">int b = 2;   // 2. Happens-Before
+</span></span></code></pre></div></li>
+<li>监视器锁规则。一个线程在同步块内部对一个锁的解锁操作，一定早于另一个线程对同一个锁的加锁操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">synchronized(lock) {
+</span></span><span class="line"><span class="cl">    // 操作 A
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// 锁的释放 Happens-Before 后续的加锁
+</span></span><span class="line"><span class="cl">synchronized(lock) {
+</span></span><span class="line"><span class="cl">    // 操作 B
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>volatile</code>变量规则。对一个 <code>volatile</code> 变量的写操作，一定早于随后对这个变量的读操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">volatile boolean flag = false;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">flag = true; // 写操作 Happens-Before
+</span></span><span class="line"><span class="cl">if (flag) {  // 读操作
+</span></span><span class="line"><span class="cl">    // flag 的写操作 Happens-Before flag 的读操作
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>线程启动规则。主线程启动一个子线程，子线程中的操作一定在主线程中启动该子线程的操作之后执行。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 操作 B
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start(); // 启动操作 Happens-Before
+</span></span></code></pre></div></li>
+<li>线程终止规则。一个线程中的所有操作一定早于另一个线程检测到这个线程已经终止。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 操作 A
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start();
+</span></span><span class="line"><span class="cl">t.join(); // A Happens-Before join 返回
+</span></span></code></pre></div></li>
+<li>线程中断规则。对线程的中断操作一定早于被中断线程检测到中断事件。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 检测中断
+</span></span><span class="line"><span class="cl">    if (Thread.interrupted()) {
+</span></span><span class="line"><span class="cl">        // 中断事件发生
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start();
+</span></span><span class="line"><span class="cl">t.interrupt(); // Happens-Before 检测中断
+</span></span></code></pre></div></li>
+<li>对象的构造函数规则。一个对象的构造函数执行结束一定早于该对象的 finalize 方法开始执行。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">class MyObject {
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    protected void finalize() {
+</span></span><span class="line"><span class="cl">        // 构造函数 Happens-Before finalize 方法
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>传递性规则。如果操作 A 发生在操作 B 之前，操作 B 发生在操作 C 之前，那么操作 A 一定早于操作 C。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t1 = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 操作 A
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">Thread t2 = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 操作 B
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t1.start();
+</span></span><span class="line"><span class="cl">t1.join(); // A Happens-Before join 返回
+</span></span><span class="line"><span class="cl">t2.start();
+</span></span><span class="line"><span class="cl">t2.join(); // join 返回 Happens-Before B
+</span></span></code></pre></div></li>
+</ol>
+<h3 id="as-if-serial">as-if-serial</h3>
+<p>为了提高并行度，优化程序性能，编译器和处理器会对代码进行指令重排序。但为了不改变程序的执行结果，尽可能地提高程序执行的并行度，编译器、必须遵守<code>as-if-serial</code>语义。</p>
+<p>&ldquo;as-if-serial&quot;最初来自于计算机科学领域中的编译优化和程序行为的讨论。
+这个概念的核心思想是，编译器和计算机系统在进行优化时，可以重新排列和改变指令的执行顺序，只要最终程序的执行结果与按照程序顺序执行时的结果一致即可。
+这个原则确保了编译器和硬件系统在优化时不会改变程序的语义和行为。就是不管怎么重排序，单线程程序的执行结果不能被改变。</p>
+<p>编译器和处理器不会对存在数据依赖关系的操作做重排序，因为这种重排序会改变执行结果。但是如果操作之间不存在数据依赖关系，这些操作可能被编译器和处理器重排序。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int a=1;
+</span></span><span class="line"><span class="cl">int b=2;
+</span></span><span class="line"><span class="cl">int c=a+b;
+</span></span></code></pre></div><p>a和c之间存在数据依赖关系，同时b和c之间也存在数据依赖关系。因此在最终执行的指令序列中，c不能被重排序到A和B的前面，c如果排到a和b的前面，程序的结果将会被改变。
+a和b之间没有数据依赖关系，编译器和处理器可以重排序a和b之间的执行顺序。</p>
+<h2 id="volatile">volatile</h2>
+<p><code>volatile</code>通常被比喻成轻量级的锁，是Java并发编程中比较重要的一个关键字。<code>volatile</code>作用：</p>
+<ul>
+<li>可见性：当一个线程修改了 <code>volatile</code> 变量的值，新的值对于其他线程是立即可见的。这避免了其他线程读取到旧的缓存值。</li>
+<li>有序性：对 <code>volatile</code> 变量的读写操作不会被重排序。所有对 <code>volatile</code> 变量的写操作在内存中会按照程序的顺序执行，同时在一个线程中的操作不会重排序到 <code>volatile</code> 变量的读写操作之后。</li>
+</ul>
+<p>注意<code>volatile</code>不保证原子性，也就是线程不安全。</p>
+<h3 id="使用案例">使用案例</h3>
+<p>在Java中<code>volatile</code>是一个变量修饰符，只能用来修饰变量。<code>volatile</code>典型的使用就是单例模式中的双重检查锁实现。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">多线程下的单例模式 DCL(double check lock)
+</span></span></span><span class="line"><span class="cl"><span class="cm">**/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SingletonDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// volatile 此处作用 禁止指令重排</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">SingletonDemo</span><span class="w"> </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">SingletonDemo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">SingletonDemo</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">SingletonDemo</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SingletonDemo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为什么在此处要使用<code>volatile</code>修饰<code>singleton</code>？
+多线程下的DCL单例模式，如果不加<code>volatile</code>修饰不是绝对安全的，因为在创建对象的时候JVM底层会进行三个步骤：</p>
+<ol>
+<li>分配对象的内存空间；</li>
+<li>初始化对象；</li>
+<li>设置对象指向刚刚分配的内存地址；</li>
+</ol>
+<p>其中步骤2和步骤3是没有数据依赖关系的，而且无论重排前还是重排后的程序执行结果在单线程中并没有改变，因此这种重排优化是允许的。
+所以有可能先执行步骤3在执行步骤2，导致分配的对象不为<code>null</code>，但对象没有被初始化。所以当一个线程获取对象不为<code>null</code>时，由于对象未必已经完成初始化，会存在线程不安全的风险。</p>
+<h3 id="volatile与可见性">volatile与可见性</h3>
+<p>各个线程对主内存中共享变量的操作，都是各个线程各自拷贝到自己的工作内存操作后再写回主内存中的。
+这就可能存在一个线程AAA修改了共享变量X的值还未写回主内存中时 ，另外一个线程BBB又对内存中的一个共享变量X进行操作，但此时A线程工作内存中的共享比那里X对线程B来说并不不可见。
+这种工作内存与主内存同步延迟现象就造成了可见性问题。</p>
+<p>这种变量的可见性问题可以用<code>volatile</code>来解决。<code>volatile</code>的作用简单来说就是当一个线程修改了数据，并且写回主物理内存，其他线程都会得到通知获取最新的数据。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// thread1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; is come in&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 模拟执行其他业务</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 用该线程改变A类中 number 变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">a</span><span class="p">.</span><span class="na">numberTo100</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;thread1&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果number 等于0，则其他线程会一直等待 则证明 volatile 没有保证变量的可见性；相反则保证了变量的可见性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">number</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; thread is over&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 注意: 此时变量要加 volatile 关键字修饰； 可以去掉 volatile 来进行对比测试</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">numberTo100</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; update number&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为什么<code>volatile</code>能确保变量的可见性？
+将上面单例模式DCL实现用命令<code>javap -v SingletonDemo.class &gt;test.txt</code>命令执行，将反编译后的字节码指令写入到test文件中，可以看到<code>ACC_VOLATILE</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public static volatile content.posts.rookie.SingletonDemo singleton;
+</span></span><span class="line"><span class="cl">descriptor: Lcontent/posts/rookie/SingletonDemo;
+</span></span><span class="line"><span class="cl">flags: ACC_PUBLIC, ACC_STATIC, ACC_VOLATILE
+</span></span></code></pre></div><p><code>volatile</code>在字节码层面，就是使用访问标志<code>ACC_VOLATILE</code>来表示，供后续操作此变量时判断访问标志是否为<code>ACC_VOLATILE</code>，来决定是否遵循<code>volatile</code>的语义处理。</p>
+<p>可以从<code>openjdk8</code>中找到对应的源码文件：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">openjdk8/hotspot/src/share/vm/interpreter/bytecodeInterpreter.cpp
+</span></span></code></pre></div><p><img alt="volitile字节码" src="/iblog/posts/annex/images/essays/volitile%E5%AD%97%E8%8A%82%E7%A0%81.png"></p>
+<p>重点是<code>cache-&gt;is_volatile()</code>方法，调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">bytecodeInterpreter.cpp&gt;is_volatile() 
+</span></span><span class="line"><span class="cl">==&gt; accessFlags.hpp&gt;is_volatile 
+</span></span><span class="line"><span class="cl">==&gt; bytecodeInterpreter.cpprelease_byte_field_put
+</span></span><span class="line"><span class="cl">==&gt; oop.inline.hpp&gt;(oopDesc::byte_field_acquire、oopDesc::release_byte_field_put)
+</span></span><span class="line"><span class="cl">==&gt; orderAccess.hpp
+</span></span><span class="line"><span class="cl">&gt;&gt; orderAccess_linux_x86.inline.hpp.OrderAccess::release_store
+</span></span></code></pre></div><p>最终调用了<code>OrderAccess::release_store</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">inline void     OrderAccess::release_store(volatile jbyte*   p, jbyte   v) { *p = v; }
+</span></span><span class="line"><span class="cl">inline void     OrderAccess::release_store(volatile jshort*  p, jshort  v) { *p = v; }
+</span></span></code></pre></div><p>可以从上面看到C++的实现层面，又使用C++中的<code>volatile</code>关键字，用来修饰变量，通常用于建立语言级别的内存屏障<code>memory barrier</code>。
+在《C++ Programming Language》一书中对<code>volatile</code>修饰词的解释：</p>
+<blockquote>
+<p>A volatile specifier is a hint to a compiler that an object may change its value in ways not specified by the language so that aggressive optimizations must be avoided.</p>
+</blockquote>
+<ul>
+<li><code>volatile</code>修饰的类型变量表示可以被某些编译器未知的因素更改。</li>
+<li>使用 <code>volatile</code> 变量时，避免激进的优化。系统总是重新从内存读取数据，即使它前面的指令刚从内存中读取被缓存，防止出现未知更改和主内存中不一致。</li>
+</ul>
+<p>其在64位系统的实现<code>orderAccess_linux_x86.inline.hpp.OrderAccess::release_store</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">inline void OrderAccess::fence() {
+</span></span><span class="line"><span class="cl">  if (os::is_MP()) {
+</span></span><span class="line"><span class="cl">    // always use locked addl since mfence is sometimes expensive
+</span></span><span class="line"><span class="cl">#ifdef AMD64
+</span></span><span class="line"><span class="cl">    __asm__ volatile (&#34;lock; addl $0,0(%%rsp)&#34; : : : &#34;cc&#34;, &#34;memory&#34;);
+</span></span><span class="line"><span class="cl">#else
+</span></span><span class="line"><span class="cl">    __asm__ volatile (&#34;lock; addl $0,0(%%esp)&#34; : : : &#34;cc&#34;, &#34;memory&#34;);
+</span></span><span class="line"><span class="cl">#endif
+</span></span><span class="line"><span class="cl">  }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>其中代码<code>lock; addl $0,0(%%rsp)</code>就是常说的<strong>lock前缀</strong>。</p>
+<blockquote>
+<p>lock前缀，会保证某个处理器对共享内存的独占使用。它将本处理器缓存写入内存，该写入操作会引起其他处理器或内核对应的缓存失效。通过独占内存、使其他处理器缓存失效，达到了“指令重排序无法越过内存屏障”的作用。</p>
+</blockquote>
+<p>对于 <code>volatile</code>修饰的变量，当对 <code>volatile</code> 修饰的变量进行写操作的时候，JVM会向处理器发送一条带有<code>lock</code>前缀的指令，将这个缓存中的变量回写到系统主存中。
+但是就算写回到内存，如果其他处理器缓存的值还是旧的，再执行计算操作就会有问题，所以在多处理器下，为了保证各个处理器的缓存是一致的，就会实现<strong>缓存一致性协议</strong>。</p>
+<blockquote>
+<p>缓存一致性协议: 每个处理器通过嗅探在总线上传播的数据来检查自己缓存的值是不是过期了，当处理器发现自己缓存行对应的内存地址被修改，就会将当前处理器的缓存行设置成无效状态，当处理器要对这个数据进行修改操作的时候，会强制重新从系统内存里把数据读到处理器缓存里。</p>
+</blockquote>
+<p>为了提高CPU处理器的执行速度，在处理器和内存之间增加了多级缓存来提升。但是由于引入了多级缓存，就存在缓存数据不一致问题。</p>
+<p><img alt="CPU多级缓存" src="/iblog/posts/annex/images/essays/CPU%E5%A4%9A%E7%BA%A7%E7%BC%93%E5%AD%98.jpg"></p>
+<p>所以如果一个变量被<code>volatile</code>所修饰的话，在每次数据变化之后，其值都会被强制刷入主存。
+而其他处理器的缓存由于遵守了缓存一致性协议，也会把这个变量的值从主存加载到自己的缓存中。这就保证了一个<code>volatile</code>在并发编程中，其值在多个缓存中是可见的。</p>
+<h3 id="volatile与有序性">volatile与有序性</h3>
+<p>有序性指的就是代码按照顺序执行，是对比指令重排来说的。计算机在执行程序时，为了提高性能，编译器和处理器常常会做指令重排。
+在上面的使用案例中的代码，单例模式DCL就是一个使用禁止指令重排的案例。</p>
+<p><code>volatile</code>禁止指令重排的原因是什么？<code>volatile</code> 关键字通过在读写操作前后插入内存屏障来禁止指令重排序，从而确保了内存可见性和操作的有序性。</p>
+<ol>
+<li>写入<code>volatile</code>变量时：</li>
+</ol>
+<ul>
+<li>在写操作之前插入一个 <code>StoreStore</code> 屏障，确保在写入 <code>volatile</code> 变量之前的所有普通写操作都已经完成。</li>
+<li>在写操作之后插入一个 <code>StoreLoad</code> 屏障，确保在写入 <code>volatile</code> 变量之后的所有普通读操作都能读取到最新的值。</li>
+</ul>
+<ol start="2">
+<li>读取<code>volatile</code>变量时：</li>
+</ol>
+<ul>
+<li>在读操作之前插入一个 <code>LoadLoad</code> 屏障，确保在读取 <code>volatile</code> 变量之前的所有普通读操作都已经完成。</li>
+<li>在读操作之后插入一个 <code>LoadStore</code> 屏障，确保在读取 <code>volatile</code> 变量之后的所有普通写操作都能读取到最新的值。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Example</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writer</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">42</span><span class="p">;</span><span class="w">    </span><span class="c1">// 1. 普通写操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">   </span><span class="c1">// 2. volatile 写操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">reader</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">    </span><span class="c1">// 3. volatile 读操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w"> </span><span class="c1">// 4. 普通读操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="volatile与原子性">volatile与原子性</h3>
+<p><code>volatile</code>不保证原子性，也就是线程不安全。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 创建20个线程 每个线程让 number++ 1000次；
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * number 变量用 volatile 修饰
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 如果 volatile 保证变量的原子性，则最后结果为 20 * 1000，反之则不保证。
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 当然不排除偶然事件，建议反复多试几次。
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">a</span><span class="p">.</span><span class="na">addPlusplus</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前存活线程大于 2 个(包括main线程) 礼让线程继续执行上边的线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">activeCount</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">yield</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; Thread is over\t&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="na">number</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addPlusplus</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">number</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>不保证原子性的原因，由于各个线程之间都是复制主内存的数据到自己的工作空间里边修改数据，CPU的轮询反复切换线程，会导致数据丢失。
+即某个线程修改了数据，准备回主内存，此时CPU切换到另一个线程修改了数据，并且写回到了主内存。其他的线程不知道主内存的数据已经被更改，还会执行将之前从主内存复制的数据修改后的，写到主内存，这就导致了数据被覆盖、丢失。</p>
+<p>如果要解决原子性的问题，在Java中只能控制线程，在修改的时候不能被中断，即加锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 创建20个线程 每个线程让 number++ 1000次；
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * number 变量用 volatile 修饰
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 如果 volatile 保证变量的原子性，则最后结果为 20 * 1000，反之则不保证。
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 当然不排除偶然事件，建议反复多试几次。
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">a</span><span class="p">.</span><span class="na">addPlusplus</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前存活线程大于 2 个(包括main线程) 礼让线程继续执行上边的线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">activeCount</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">yield</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; Thread is over\t&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="na">number</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 如果要解决原子性的问题可以用synchronized 关键字(这种太浪费性能)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 可用JUC下的 AtomicInteger 来解决
+</span></span></span><span class="line"><span class="cl"><span class="cm">     **/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">atomicInteger</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">number</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addPlusplus</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">incrementAndGet</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>对于<code>AtomicInteger.incrementAndGet</code>方法来说，原理就是<code>volatile</code> + <code>do...while()</code> + <code>CAS</code>;</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">incrementAndGet</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">getAndAddInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//=========================</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>用<code>volatile</code>修饰该变量，保证该变量被某个线程修改时，保证其他线程中的这个变量的可见性。
+在多线程环境下，CPU轮流切换线程执行，有可能某个线程修改了数据，准备回主内存，此时CPU切换到另一个线程修改了数据，并且写回到了主内存，此时就导致数据的不准确。
+<code>do...while()</code> + <code>CAS</code>的作用就是，当某个线程工作内存中的值与主内存中的值，如果不相同就会一直<code>while</code>循环下去，之所以用<code>do..while</code>是考虑到做自增操作。</p>
+<h2 id="synchronized">synchronized</h2>
+<p><code>synchronized</code>是Java提供的关键字译为同步，是Java中用于实现线程同步的一种机制。它可以确保在同一时间只有一个线程能够执行某段代码，从而避免线程安全问题。
+当它修饰一个方法或者一个代码块的时候，同一时刻最多只有一个线程执行这段代码。<code>synchronized</code>关键字在需要原子性、可见性和有序性这三种特性的时候都可以作为其中一种解决方案，大部分并发控制操作都能使用<code>synchronized</code>来完成。</p>
+<p><code>synchronized</code>的作用：</p>
+<ul>
+<li>互斥性：确保在同一时间只有一个线程可以执行被 <code>synchronized</code> 修饰的代码块或方法。</li>
+<li>可见性：当一个线程退出 <code>synchronized</code> 代码块时，它所做的所有修改对于进入 <code>synchronized</code> 代码块的其他线程是可见的。这是通过释放和获得监视器锁来实现的。</li>
+</ul>
+<h3 id="使用示例">使用示例</h3>
+<table>
+<thead>
+<tr>
+<th>修饰的对象</th>
+<th>作用范围</th>
+<th>作用对象</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>同步一个实例方法</td>
+<td>整个实例方法</td>
+<td>调用此方法的对象</td>
+</tr>
+<tr>
+<td>同步一个静态方法</td>
+<td>整个静态方法</td>
+<td>此类的所有对象</td>
+</tr>
+<tr>
+<td>同步代码块-对象</td>
+<td>整个代码块</td>
+<td>调用此代码块的对象</td>
+</tr>
+<tr>
+<td>同步代码块-类</td>
+<td>整个代码块</td>
+<td>此类的所有对象</td>
+</tr>
+</tbody>
+</table>
+<ul>
+<li>同步一个实例方法。在这种情况下，<code>increment</code>方法被声明为同步方法。当一个线程调用这个方法时，它会获得该实例的监视器锁，其他线程必须等待这个线程释放锁后才能调用这个方法。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>同步一个静态方法。当<code>synchronized</code>作用于静态方法时，其锁就是当前类的<code>class</code>对象锁。由于静态成员不专属于任何一个实例对象，而是类成员，因此通过<code>class</code>对象锁可以控制静态成员的并发操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>同步代码块。在某些情况下，我们编写的方法体可能比较大，同时存在一些比较耗时的操作，而需要同步的代码又只有一小部分，如果直接对整个方法进行同步操作，这样做就有点浪费。此时我们可以使用同步代码块的方式对需要同步的代码进行包裹。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div>除了使用<code>synchronized(this)</code>锁定，当然静态方法是没有this对象的，也可以使用<code>class</code>对象来做为锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">MainTest</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>当如果没有明确的对象作为锁，只是想让一段代码同步时，可以创建一个特殊的对象来充当锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">synchronized</span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="c1">// .....</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>零长度的<code>byte</code>数组对象创建起来将比任何对象都经济。查看编译后的字节码，生成零长度的<code>byte[]</code>对象只需3条操作码，而<code>Object lock = new Object()</code>则需要7行操作码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">byte[] emptyArray = new byte[0];
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">0: iconst_0       // 将常量0推送到栈顶
+</span></span><span class="line"><span class="cl">1: newarray byte  // 创建一个新的byte类型数组
+</span></span><span class="line"><span class="cl">3: astore_1       // 将引用类型的数据存储到局部变量表中
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Object lock = new Object();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">0: new           #2   // 创建一个新的对象
+</span></span><span class="line"><span class="cl">3: dup                // 复制栈顶的操作数栈顶的值，并将复制值压入栈顶
+</span></span><span class="line"><span class="cl">4: invokespecial #1   // 调用实例初始化方法, 使用Object.&lt;init&gt;
+</span></span><span class="line"><span class="cl">7: astore_1           // 将引用类型的数据存储到局部变量表中
+</span></span></code></pre></div><h3 id="实现原理">实现原理</h3>
+<p><code>synchronized</code>关键字在Java中通过进入和退出一个监视器来实现同步。监视器本质上是一种锁，它可以是类对象锁或实例对象锁。每个对象在JVM中都有一个与之关联的监视器。
+当一个线程进入同步代码块或方法时，它会尝试获得对象的监视器。如果成功获得锁，线程就可以执行同步代码；否则它将被阻塞，直到获得锁为止。</p>
+<p>在Java中<code>synchronized</code>锁对象时，其实就是改变对象中的对象头的<code>markword</code>的锁的标志位来实现的。用<code>javap -v MainTest.class</code>命令反编译下面代码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">demo01</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;demo 01&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">demo02</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">MainTest</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;demo 02&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">  synchronized void demo01();
+</span></span><span class="line"><span class="cl">    descriptor: ()V
+</span></span><span class="line"><span class="cl">    flags: ACC_SYNCHRONIZED
+</span></span><span class="line"><span class="cl">    Code:
+</span></span><span class="line"><span class="cl">      stack=2, locals=1, args_size=1
+</span></span><span class="line"><span class="cl">         0: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
+</span></span><span class="line"><span class="cl">         3: ldc           #3                  // String demo 01
+</span></span><span class="line"><span class="cl">         5: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">         8: return
+</span></span><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">void demo02();
+</span></span><span class="line"><span class="cl">    descriptor: ()V
+</span></span><span class="line"><span class="cl">    flags:
+</span></span><span class="line"><span class="cl">    Code:
+</span></span><span class="line"><span class="cl">      stack=2, locals=3, args_size=1
+</span></span><span class="line"><span class="cl">         0: ldc           #5                  // class content/posts/rookie/MainTest
+</span></span><span class="line"><span class="cl">         2: dup
+</span></span><span class="line"><span class="cl">         3: astore_1
+</span></span><span class="line"><span class="cl">         4: monitorenter
+</span></span><span class="line"><span class="cl">         5: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
+</span></span><span class="line"><span class="cl">         8: ldc           #6                  // String demo 02
+</span></span><span class="line"><span class="cl">        10: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">        13: aload_1
+</span></span><span class="line"><span class="cl">        14: monitorexit
+</span></span><span class="line"><span class="cl">        15: goto          23
+</span></span><span class="line"><span class="cl">        18: astore_2
+</span></span><span class="line"><span class="cl">        19: aload_1
+</span></span><span class="line"><span class="cl">        20: monitorexit
+</span></span><span class="line"><span class="cl">        21: aload_2
+</span></span><span class="line"><span class="cl">        22: athrow
+</span></span><span class="line"><span class="cl">        23: return
+</span></span><span class="line"><span class="cl">// ...
+</span></span></code></pre></div><p>通过反编译后代码可以看出：</p>
+<ul>
+<li>对于同步方法，JVM采用<code>ACC_SYNCHRONIZED</code>标记符来实现同步；</li>
+<li>对于同步代码块，JVM采用<code>monitorenter</code>、<code>monitorexit</code>两个指令来实现同步；</li>
+</ul>
+<p>其中同步代码块，有两个<code>monitorexit</code>指令的原因是为了保证抛异常的情况下也能释放锁，所以<code>javac</code>为同步代码块添加了一个隐式的<code>try-finally</code>，在<code>finally</code>中会调用<code>monitorexit</code>命令释放锁。</p>
+<p><a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-2.html#jvms-2.11.10">官方文档</a>中关于同步方法和同步代码块的实现原理描述：</p>
+<blockquote>
+<p>方法级的同步是隐式的。同步方法的常量池中会有一个 <code>ACC_SYNCHRONIZED</code> 标志。当某个线程要访问某个方法的时候，会检查是否有 <code>ACC_SYNCHRONIZED</code>，如果有设置，则需要先获得监视器锁，然后开始执行方法，方法执行之后再释放监视器锁。这时如果其他线程来请求执行方法，会因为无法获得监视器锁而被阻断住。值得注意的是，如果在方法执行过程中，发生了异常，并且方法内部并没有处理该异常，那么在异常被抛到方法外面之前监视器锁会被自动释放。<br>
+同步代码块使用 <code>monitorenter</code> 和 <code>monitorexit</code> 两个指令实现。可以把执行 <code>monitorenter</code> 指令理解为加锁，执行 <code>monitorexit</code> 理解为释放锁。 每个对象维护着一个记录着被锁次数的计数器。未被锁定的对象的该计数器为0，当一个线程获得锁（执行 <code>monitorenter</code>）后，该计数器自增变为 1 ，当同一个线程再次获得该对象的锁的时候，计数器再次自增。当同一个线程释放锁（执行 <code>monitorexit</code> 指令）的时候，计数器再自减。当计数器为0的时候。锁将被释放，其他线程便可以获得锁。</p>
+</blockquote>
+<p>其实无论是<code>ACC_SYNCHRONIZED</code>还是<code>monitorenter</code>、<code>monitorexit</code>都是基于<code>Monitor</code>实现的，每一个锁都对应一个<code>monitor</code>对象。
+在Java虚拟机(HotSpot)中，<code>Monitor</code>是基于C++实现的，由<code>ObjectMonitor</code>实现。在<code>/hotspot/src/share/vm/runtime/objectMonitor.hpp</code>中有<code>ObjectMonitor</code>的实现。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// initialize the monitor, exception the semaphore, all other fields
+</span></span><span class="line"><span class="cl">// are simple integers or pointers
+</span></span><span class="line"><span class="cl">ObjectMonitor() {
+</span></span><span class="line"><span class="cl">    _header       = NULL;
+</span></span><span class="line"><span class="cl">    _count        = 0; //记录个数
+</span></span><span class="line"><span class="cl">    _waiters      = 0,
+</span></span><span class="line"><span class="cl">    _recursions   = 0;
+</span></span><span class="line"><span class="cl">    _object       = NULL;
+</span></span><span class="line"><span class="cl">    _owner        = NULL;
+</span></span><span class="line"><span class="cl">    _WaitSet      = NULL; //处于wait状态的线程，会被加入到_WaitSet
+</span></span><span class="line"><span class="cl">    _WaitSetLock  = 0 ;
+</span></span><span class="line"><span class="cl">    _Responsible  = NULL ;
+</span></span><span class="line"><span class="cl">    _succ         = NULL ;
+</span></span><span class="line"><span class="cl">    _cxq          = NULL ;
+</span></span><span class="line"><span class="cl">    FreeNext      = NULL ;
+</span></span><span class="line"><span class="cl">    _EntryList    = NULL ; //处于等待锁block状态的线程，会被加入到该列表
+</span></span><span class="line"><span class="cl">    _SpinFreq     = 0 ;
+</span></span><span class="line"><span class="cl">    _SpinClock    = 0 ;
+</span></span><span class="line"><span class="cl">    OwnerIsThread = 0 ;
+</span></span><span class="line"><span class="cl">  }
+</span></span></code></pre></div><ul>
+<li><code>_owner</code>：指向持有<code>ObjectMonitor</code>对象的线程；</li>
+<li><code>_WaitSet</code>：存放处于<code>wait</code>状态的线程队列；</li>
+<li><code>_EntryList</code>：存放处于等待锁<code>block</code>状态的线程队列；</li>
+<li><code>_recursions</code>：锁的重入次数；</li>
+<li><code>_count</code>：用来记录该线程获取锁的次数；</li>
+</ul>
+<p>当多个线程同时访问一段同步代码时，首先会进入<code>_EntryList</code>队列中，当某个线程获取到对象的<code>monitor</code>后进入<code>_Owner</code>区域，并把<code>monitor</code>中的<code>_owner</code>变量设置为当前线程，同时<code>monitor</code>中的计数器<code>_count</code>加1，即获得对象锁。</p>
+<p><img alt="synchronized原理" src="/iblog/posts/annex/images/essays/synchronized%E5%8E%9F%E7%90%86.gif"></p>
+<p>若此时持有<code>monitor</code>的线程调用<code>wait()</code>方法，将释放当前对象持有的<code>monitor</code>，<code>_owner</code>变量恢复为<code>null</code>，<code>_count</code>自减1，同时该线程进入<code>_WaitSet</code>集合中等待被唤醒。若当前线程执行完毕也将释放<code>monitor</code>并复位变量的值，以便其他线程进入获取<code>monitor</code>。</p>
+<p><code>ObjectMonitor</code>中其他方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">  bool      try_enter (TRAPS) ;
+</span></span><span class="line"><span class="cl">  void      enter(TRAPS);
+</span></span><span class="line"><span class="cl">  void      exit(bool not_suspended, TRAPS);
+</span></span><span class="line"><span class="cl">  void      wait(jlong millis, bool interruptable, TRAPS);
+</span></span><span class="line"><span class="cl">  void      notify(TRAPS);
+</span></span><span class="line"><span class="cl">  void      notifyAll(TRAPS);
+</span></span></code></pre></div><p><code>sychronized</code>加锁的时候，会调用<code>objectMonitor</code>的<code>enter</code>方法，解锁的时候会调用<code>exit</code>方法。
+在JDK1.6之前，<code>synchronized</code>的实现直接调用<code>ObjectMonitor</code>的<code>enter</code>和<code>exit</code>，这种锁被称之为重量级锁，这也是早期<code>synchronized</code>效率低的原因。
+所以，在JDK1.6中出现对锁进行了很多的优化，进而出现轻量级锁，偏向锁，锁消除，适应性自旋锁，锁粗化。</p>
+<blockquote>
+<p>早期的<code>synchronized</code>效率低的原因：
+Java的线程是映射到操作系统原生线程之上的，如果要阻塞或唤醒一个线程就需要操作系统的帮忙，监视器锁<code>monitor</code>是依赖于底层的操作系统的<code>Mutex Lock</code>来实现的，而操作系统实现线程之间的切换时需要从用户态转换到核心态。因此状态转换需要花费很多的处理器时间。
+对于代码简单的同步块（如被<code>synchronized</code>修饰的<code>get</code>、<code>set</code>方法）状态转换消耗的时间有可能比用户代码执行的时间还要长，所以说<code>synchronized</code>是Java语言中一个重量级的操作。也是为什么早期的<code>synchronized</code>效率低的原因。</p>
+</blockquote>
+<h3 id="锁的升级">锁的升级</h3>
+<p>在JDK1.6之前，使用<code>synchronized</code>被称作重量级锁，它的实现是基于底层操作系统的<code>mutex</code>互斥原语的，这个开销是很大的。所以在JDK1.6时JVM对<code>synchronized</code>做了优化。
+<code>synchronized</code>锁对象时，其实就是改变对象中的对象头的<code>markword</code>的锁的标志位来实现的。对象头中<code>markword</code>锁状态的表示：</p>
+<table>
+<thead>
+<tr>
+<th>锁状态</th>
+<th><code>markword</code> 锁标志位</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>无锁状态</td>
+<td><code>01</code></td>
+</tr>
+<tr>
+<td>偏向锁状态</td>
+<td><code>01</code></td>
+</tr>
+<tr>
+<td>轻量级锁状态</td>
+<td><code>00</code></td>
+</tr>
+<tr>
+<td>重量级锁状态</td>
+<td><code>10</code></td>
+</tr>
+<tr>
+<td>被垃圾回收器标记</td>
+<td><code>11</code></td>
+</tr>
+</tbody>
+</table>
+<p>对象的锁状态，可以分为4种，级别从低到高依次是：无锁状态、偏向锁状态、轻量级锁状态和重量级锁状态。
+其中这几个锁只有重量级锁是需要使用操作系统底层<code>mutex</code>互斥原语来实现，其他的锁都是使用对象头来实现的。</p>
+<ul>
+<li>无锁状态：<code>markword</code>锁的标志位0，偏向锁的标志位为1；例如：刚被创建出来的对象。</li>
+<li>偏向锁：如果一个线程获取了锁，此时<code>markword</code>的结构变为偏向锁结构，当这个线程再次请求锁时，无需再做任何同步操作，直接可以获取锁。
+省去了大量有关锁申请的操作，从而也就提供程序的性能。</li>
+<li>轻量级锁：当锁是偏向锁的时候，被另外的线程所访问，偏向锁就会升级为轻量级锁，其他线程会通过自旋的形式尝试获取锁，不会阻塞从而提高性能。</li>
+<li>重量级锁：升级为重量级锁时，锁标志的状态值变为“10”，此时<code>MarkWord</code>中存储的是指向重量级锁的指针，此时等待锁的线程都会进入阻塞状态，所以开销是很大。</li>
+</ul>
+<p>随着锁的竞争，锁从偏向锁升级到轻量级锁，再升级的重量级锁。锁升级过程：</p>
+<ol>
+<li>无锁状态升级为偏向锁：
+一个对象刚开始实例化的时候，没有任何线程来访问它的时候，它是可偏向的，意味着它现在认为只可能有一个线程来访问它，所以当第一个线程来访问它的时候，它会偏向这个线程。此时对象持有偏向锁。
+偏向第一个线程，这个线程在修改对象头成为偏向锁的时候使用CAS操作，并将对象头中的<code>ThreadID</code>改成自己的ID，之后再次访问这个对象时，只需要对比ID，就不需要再使用CAS在进行操作。</li>
+<li>偏向锁升级为轻量级锁：
+一旦有第二个线程访问这个对象，因为偏向锁不会主动释放，所以第二个线程可以看到对象的偏向状态。
+这时表明在这个对象上已经存在竞争了，JVM会检查原来持有该对象锁的线程是否依然存活，如果不存活，则可以将对象变为无锁状态，然后重新偏向新的线程。
+如果原来的线程依然存活，则马上执行这个线程的操作栈，检查该对象的使用情况，如果仍然需要持有偏向锁，则偏向锁升级为轻量级锁。</li>
+<li>轻量级锁升级为重量级锁：
+轻量级锁认为竞争存在，但是竞争的程度很轻，一般两个线程对于同一个锁的操作都会错开，或者说稍微等待一下，另一个线程就会释放锁。
+但是当自旋超过一定的次数，或者一个线程在持有锁，一个在自旋，又有第三个来访时，轻量级锁膨胀为重量级锁，重量级锁使除了拥有锁的线程以外的线程都阻塞。
+当持有锁的线程退出同步块或方法时，会执行<code>monitorexit</code>指令释放锁。如果有其他线程在等待该锁，它们会被唤醒并竞争锁的所有权。</li>
+</ol>
+<p>在所有的锁都启用的情况下，线程进入临界区时会先获取偏向锁，如果已经存在偏向锁了，则会尝试获取轻量级锁，启用自旋锁。
+如果自旋也没有获取到锁，则使用重量级锁，将没有获取到锁的线程阻塞挂起，直到持有锁的线程执行完同步块唤醒他们。</p>
+<p>偏向锁是在无锁争用的情况下使用的，也就是同步代码块在当前线程没有执行完之前，没有其它线程会执行该同步块。
+一旦有了第二个线程的争用，偏向锁就会升级为轻量级锁，如果轻量级锁自旋到达阈值后，没有获取到锁，就会升级为重量级锁。</p>
+<p>锁可以升级，但是不可以降级，有的观点认为不会进行锁降级。
+实际上，锁降级确实是会发生的，当JVM进入<strong>安全点</strong>的时候，会检查是否有闲置的`Monitor，然后试图进行降级。
+也就是说，仅仅是发生在STW的时候，只有垃圾回收线程能够观测到它，在我们正常使用的过程中是不会发生锁降级的，只有在GC的时候才会降级。</p>
+<blockquote>
+<p>安全点：程序执行时并非在所有地方都能停顿下来开始GC，只有在特定的位置才能停顿下来开始GC，这些位置称为安全点。</p>
+</blockquote>
+<h3 id="synchronized与可见性">synchronized与可见性</h3>
+<p>可见性是指当多个线程访问同一个变量时，一个线程修改了这个变量的值，其他线程能够立即看得到修改的值。</p>
+<p>Java内存模型规定了所有的变量都存储在主内存中，每条线程还有自己的工作内存，线程的工作内存中保存了该线程中是用到的变量的主内存副本拷贝，线程对变量的所有操作都必须在工作内存中进行，而不能直接读写主内存。
+不同的线程之间也无法直接访问对方工作内存中的变量，线程间变量的传递均需要自己的工作内存和主存之间进行数据同步进行。所以就可能出现线程1改了某个变量的值，但是线程2不可见的情况。</p>
+<p>被<code>synchronized</code>修饰的代码，在开始执行时会加锁，执行完成后会进行解锁。但是为了保证可见性，有一条规则是这样的，“对一个变量解锁之前，必须先把此变量同步回主存中”，这样解锁后，后续线程就可以访问到被修改后的值。
+所以<code>synchronized</code>关键字锁住的对象，其值是具有可见性的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">VisibilityExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">toggleFlag</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 修改共享变量并确保可见性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">!</span><span class="n">flag</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 其他操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isFlag</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取共享变量并确保可见性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">flag</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="synchronized与原子性">synchronized与原子性</h3>
+<p>原子性是指一个操作是不可中断的，要全部执行完成，要不就都不执行。</p>
+<p>线程是CPU调度的基本单位，CPU有时间片的概念，会根据不同的调度算法进行线程调度。当一个线程获得时间片之后开始执行，在时间片耗尽之后，就会失去CPU使用权。所以在多线程场景下，由于时间片在线程间轮换，就会发生原子性问题。
+在Java中，为了保证原子性，提供了两个高级的字节码指令<code>monitorenter</code>和<code>monitorexit</code>，这两个字节码指令，在Java中对应的关键字就是<code>synchronized</code>。
+通过<code>monitorexit</code>和<code>monitorexit</code>指令，可以保证被<code>synchronized</code>修饰的代码在同一时间只能被一个线程访问，在锁未释放之前，无法被其他线程访问到。
+因此在Java中可以使用<code>synchronized</code>来保证方法和代码块内的操作是原子性的。</p>
+<p>举个例子，线程1在执行<code>monitorenter</code>指令的时候，会对<code>Monitor</code>进行加锁，加锁后其他线程无法获得锁，除非线程1主动解锁。
+即使在执行过程中，由于某种原因，比如CPU时间片用完，线程1放弃了CPU，但是它并没有进行解锁。
+而由于<code>synchronized</code>的锁是可重入的，下一个时间片还是只能被他自己获取到，还是会继续执行代码，直到所有代码执行完，这就保证了原子性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AtomicityExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 原子性的递增操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">decrement</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 原子性的递减操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 原子性的读取操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicityExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicityExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程1：递增操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程2：递减操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">decrement</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 启动线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 等待两个线程执行完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出最终的计数结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Final Count: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">example</span><span class="p">.</span><span class="na">getCount</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="synchronized与有序性">synchronized与有序性</h3>
+<p>有序性即程序执行的顺序按照代码的先后顺序执行。</p>
+<p>除了引入了时间片以外，由于处理器优化和指令重排等，CPU还可能对输入代码进行乱序执行，比如<code>load-&gt;add-&gt;save</code>有可能被优化成<code>load-&gt;save-&gt;add</code>这就是可能存在有序性问题。
+这里需要注意的是，<code>synchronized</code>是无法禁止指令重排和处理器优化的，也就是说<code>synchronized</code>无法避免上述提到的问题。
+那<code>synchronized</code>是如何保证有序性的？</p>
+<p><code>synchronized</code>通过两个主要机制来保证有序性。<code>synchronized</code>的主要特性是互斥性，意味着在同一时刻只有一个线程可以进入同步块，既然是单线程就需要遵守<code>as-if-serial</code>语义，那么就可以认为单线程程序是按照顺序执行的。</p>
+<blockquote>
+<p><code>as-if-serial</code>语义：不管怎么重排序（编译器和处理器为了提高并行度），单线程程序的执行结果都不能被改变。编译器和处理器无论如何优化，都必须遵守<code>as-if-serial</code>语义。</p>
+</blockquote>
+<p>第二个保证就是内存屏障。编译器和CPU在执行代码时，可能会为了优化性能进行指令重排，但<code>synchronized</code>块内的指令不会被重排。
+原因就是Java内存模型通过在进入和退出<code>synchronized</code>块时插入内存屏障，来保证这些操作在多线程环境下的顺序执行。
+在进入<code>synchronized</code>块时，会插入一个<code>LoadLoad</code>屏障和一个<code>LoadStore</code>屏障，确保在锁被获取后，前面的所有读操作和写操作都已经完成。
+在退出<code>synchronized</code>块时，会插入一个<code>StoreStore</code>屏障和一个<code>StoreLoad</code>屏障，确保在锁被释放前，所有的写操作都已经完成，并且这些写操作对其他线程可见。</p>
+<h2 id="cas">CAS</h2>
+<p>CAS全称为<code>Compare and Swap</code>被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更新为新值。
+CAS操作是原子的，这意味着在多个线程同时执行CAS操作时，不会发生竞争条件。</p>
+<h3 id="使用示例-1">使用示例</h3>
+<p><code>java.util.concurrent.atomic</code>并发包下的所有原子类都是基于CAS来实现的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">atomicInteger</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">result</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;更新成功，当前值：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;更新失败，当前值：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>CAS一些常见使用场景：</p>
+<ul>
+<li>使用CAS实现线程安全的计数器，避免传统锁的开销。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">oldValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">counter</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">counter</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">oldValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">newValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>使用CAS来实现无锁队列、栈等数据结构。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASQueue</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">enqueue</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">dequeue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentHead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentHead</span><span class="p">,</span><span class="w"> </span><span class="n">nextNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在数据库中，CAS可以用于实现乐观锁机制，避免长时间持有锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">OptimisticLocking</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">version</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">updateWithOptimisticLock</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedVersion</span><span class="p">,</span><span class="w"> </span><span class="n">Runnable</span><span class="w"> </span><span class="n">updateTask</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">currentVersion</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentVersion</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedVersion</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">updateTask</span><span class="p">.</span><span class="na">run</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentVersion</span><span class="p">,</span><span class="w"> </span><span class="n">currentVersion</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getVersion</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OptimisticLocking</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">OptimisticLocking</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">updateTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Performing update&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">version</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">getVersion</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">success</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">updateWithOptimisticLock</span><span class="p">(</span><span class="n">version</span><span class="p">,</span><span class="w"> </span><span class="n">updateTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">success</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Update successful.&#34;</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Update failed.&#34;</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在实现线程池时，CAS可以用于安全地管理线程状态和任务队列。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASThreadPool</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">submitTask</span><span class="p">(</span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Runnable</span><span class="w"> </span><span class="nf">getTask</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentHead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentHead</span><span class="p">,</span><span class="w"> </span><span class="n">nextNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="unsafe">Unsafe</h3>
+<p><code>Unsafe</code>是CAS的核心类，Java无法直接访问底层操作系统，而是通过<code>native</code>方法来访问。不过尽管如此，JVM还是开了一个后门，JDK中有一个类<code>Unsafe</code>，它提供了硬件级别的原子操作。</p>
+<p><code>Unsafe</code>类位于<code>sun.misc</code>包中，它提供了访问底层操作系统的特定功能，如直接内存访问、CAS 操作等。
+由于其提供了直接操作内存的能力，使用不当可能导致内存泄漏、数据损坏等问题，应谨慎使用。
+<code>Unsafe</code>类包含了许多不安全的操作，所以它并不是Java标准的一部分，而且在Java9开始已经标记为受限制的API。</p>
+<p>Java中CAS操作的执行依赖于<code>Unsafe</code>类的方法，<code>Unsafe</code>类中的所有方法都是<code>native</code>修饰的，也就是说<code>Unsafe</code>类中的方法都直接调用操作系统底层资源执行相应任务。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">UnsafeExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Unsafe</span><span class="w"> </span><span class="n">unsafe</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Field</span><span class="w"> </span><span class="n">field</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Unsafe</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;theUnsafe&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">field</span><span class="p">.</span><span class="na">setAccessible</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">unsafe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Unsafe</span><span class="p">)</span><span class="w"> </span><span class="n">field</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">valueOffset</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">objectFieldOffset</span><span class="p">(</span><span class="n">UnsafeExample</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;value&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">current</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">unsafe</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="实现原理-1">实现原理</h3>
+<p>以<code>AtomicInteger</code>原子整型类为例，来看一下CAS实现原理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">().</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">compareAndSet
+</span></span><span class="line"><span class="cl">    --&gt; unsafe.compareAndSwapInt
+</span></span><span class="line"><span class="cl">    ---&gt; unsafe.compareAndSwapInt
+</span></span><span class="line"><span class="cl">    --&gt; (C++) cmpxchg
+</span></span></code></pre></div><p><code>AtomicInteger</code>内部方法都是基于<code>Unsafe</code>类实现的。</p>
+<blockquote>
+<p><code>Unsafe</code>是CAS的核心类，Java无法直接访问底层操作系统，而是通过<code>native</code>方法来访问。不过尽管如此，JVM还是开了一个后门，JDK中有一个类<code>Unsafe</code>，它提供了硬件级别的原子操作。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// setup to use Unsafe.compareAndSwapInt for updates</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Unsafe</span><span class="w"> </span><span class="n">unsafe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Unsafe</span><span class="p">.</span><span class="na">getUnsafe</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">valueOffset</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">objectFieldOffset</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">(</span><span class="n">AtomicInteger</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;value&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="n">ex</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSet</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expect</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">update</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">expect</span><span class="p">,</span><span class="w"> </span><span class="n">update</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>compareAndSwapInt</code>方法参数：</p>
+<ul>
+<li><code>this</code>：<code>Unsafe</code>对象本身，需要通过这个类来获取 <code>value</code> 的内存偏移地址；</li>
+<li><code>valueOffset</code>： <code>valueOffset</code> 表示的是变量值在内存中的偏移地址，因为 <code>Unsafe</code> 就是根据内存偏移地址获取数据的原值的。</li>
+<li><code>expect</code>：当前预期的值；</li>
+<li><code>update</code>：要设置的新值；</li>
+</ul>
+<p>继续向底层深入，就会看到<code>Unsafe</code>类中的一些其他方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Unsafe</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapObject</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapLong</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>对应查看<code>openjdk</code>的<code>hotspot</code>源码，<code>src/share/vm/prims/unsafe.cpp</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">#define FN_PTR(f) CAST_FROM_FN_PTR(void*, &amp;f)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapObject&#34;, CC&#34;(&#34;OBJ&#34;J&#34;OBJ&#34;&#34;OBJ&#34;)Z&#34;,  FN_PTR(Unsafe_CompareAndSwapObject)},
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapInt&#34;,  CC&#34;(&#34;OBJ&#34;J&#34;&#34;I&#34;&#34;I&#34;&#34;)Z&#34;,      FN_PTR(Unsafe_CompareAndSwapInt)},
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapLong&#34;, CC&#34;(&#34;OBJ&#34;J&#34;&#34;J&#34;&#34;J&#34;&#34;)Z&#34;,      FN_PTR(Unsafe_CompareAndSwapLong)},
+</span></span></code></pre></div><p>最终在<code>hotspot</code>源码实现<code>/src/share/vm/runtime/Atomic.cpp</code>中都会调用统一的<code>cmpxchg</code>函数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-cpp" data-lang="cpp"><span class="line"><span class="cl"><span class="n">jbyte</span> <span class="n">Atomic</span><span class="o">::</span><span class="n">cmpxchg</span><span class="p">(</span><span class="n">jbyte</span> <span class="n">exchange_value</span><span class="p">,</span> <span class="k">volatile</span> <span class="n">jbyte</span><span class="o">*</span><span class="n">dest</span><span class="p">,</span> <span class="n">jbyte</span> <span class="n">compare_value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">     <span class="n">assert</span> <span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="n">jbyte</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span><span class="p">,</span><span class="s">&#34;assumption.&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="n">uintptr_t</span> <span class="n">dest_addr</span> <span class="o">=</span> <span class="p">(</span><span class="n">uintptr_t</span><span class="p">)</span> <span class="n">dest</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">uintptr_t</span> <span class="n">offset</span> <span class="o">=</span> <span class="n">dest_addr</span> <span class="o">%</span> <span class="k">sizeof</span><span class="p">(</span><span class="n">jint</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="k">volatile</span> <span class="n">jint</span><span class="o">*</span><span class="n">dest_int</span> <span class="o">=</span> <span class="p">(</span> <span class="k">volatile</span> <span class="n">jint</span><span class="o">*</span><span class="p">)(</span><span class="n">dest_addr</span> <span class="o">-</span> <span class="n">offset</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 对象当前值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jint</span> <span class="n">cur</span> <span class="o">=</span> <span class="o">*</span><span class="n">dest_int</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 当前值cur的地址
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jbyte</span> <span class="o">*</span> <span class="n">cur_as_bytes</span> <span class="o">=</span> <span class="p">(</span><span class="n">jbyte</span> <span class="o">*</span><span class="p">)</span> <span class="p">(</span> <span class="o">&amp;</span> <span class="n">cur</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// new_val地址
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jint</span> <span class="n">new_val</span> <span class="o">=</span> <span class="n">cur</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">jbyte</span> <span class="o">*</span> <span class="n">new_val_as_bytes</span> <span class="o">=</span> <span class="p">(</span><span class="n">jbyte</span> <span class="o">*</span><span class="p">)</span> <span class="p">(</span> <span class="o">&amp;</span> <span class="n">new_val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">      <span class="c1">// new_val存exchange_value，后面修改则直接从new_val中取值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">new_val_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">=</span> <span class="n">exchange_value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 比较当前值与期望值，如果相同则更新，不同则直接返回
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="k">while</span> <span class="p">(</span><span class="n">cur_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">==</span> <span class="n">compare_value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="c1">// 调用汇编指令cmpxchg执行CAS操作，期望值为cur，更新值为new_val
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>         <span class="n">jint</span> <span class="n">res</span> <span class="o">=</span> <span class="n">cmpxchg</span><span class="p">(</span><span class="n">new_val</span><span class="p">,</span> <span class="n">dest_int</span><span class="p">,</span> <span class="n">cur</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">         <span class="k">if</span> <span class="p">(</span><span class="n">res</span> <span class="o">==</span> <span class="n">cur</span><span class="p">)</span> <span class="k">break</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">cur</span> <span class="o">=</span> <span class="n">res</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">new_val</span> <span class="o">=</span> <span class="n">cur</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">new_val_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">=</span> <span class="n">exchange_value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="p">}</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 返回当前值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="k">return</span> <span class="n">cur_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">];</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>从上述源码可以看出CAS操作通过CPU提供的原子指令<code>cmpxchg</code>来实现无锁操作，这个指令会保证在多个处理器同时访问和修改数据时的正确性。</p>
+<p>CPU处理器速度远远大于在主内存中的速度，为了加快访问速度，现代CPU引入了多级缓存，如L1、L2、L3 级别的缓存，这些缓存离CPU越近就越快。
+这些缓存存储了频繁使用的数据，但在多处理器环境中，缓存的一致性成为了下一个问题。
+当CPU中某个处理器对缓存中的共享变量进行了操作后，其他处理器会有个嗅探机制。即将其他处理器共享变量的缓存失效，当其他线程读取时会重新从主内存中读取最新的数据，这是基于<code>MESI</code>缓存一致性协议来实现的。</p>
+<p>在多线程环境中，CAS就是比较当前线程工作内存中的值和主内存中的值，如果相同则执行规定操作，否则继续比较，直到主内存和当前线程工作内存中的值一致为止。
+每个CPU核心都有自己的缓存，用于存储频繁访问的数据。当一个线程在某个CPU核心上修改了共享变量的值时，其他CPU核心上缓存中的该变量会被标记为无效，这样其他线程再访问该变量时就会重新从主内存中获取最新值，从而保证了数据的一致性。
+CAS操作通过CPU提供的原子指令<code>cmpxchg</code>来比较和交换变量的值，它的原子性和线程安全性依赖于CPU的硬件支持和缓存一致性协议的保障。</p>
+<p><img alt="CPU多级缓存" src="/iblog/posts/annex/images/essays/CPU%E5%A4%9A%E7%BA%A7%E7%BC%93%E5%AD%98.jpg"></p>
+<p>所以当执行CAS方法时，读取变量当前的值，并与预期值进行比较。如果变量的当前值等于预期值，则将其更新为新值。如果变量的当前值不等于预期值，则不执行更新操作。
+注意CAS操作是原子的，即整个过程不会被其他线程打断。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="cas问题">CAS问题</h3>
+<ul>
+<li>循环时间长开销：CAS操作在失败时会进行自旋重试，即反复尝试CAS操作直到成功或达到一定的重试次数。自旋次数过多可能会影响性能，因此在使用CAS时需要权衡自旋次数和性能之间的关系。
+例如<code>getAndAddInt</code>方法执行，如果CAS失败会一直会进行尝试，如果CAS长时间不成功，可能会给CPU带来很大的开销。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>原子性问题：CAS操作本身是原子的，即在执行过程中不会被中断。但需要注意的是，CAS操作是针对单个变量的原子操作，而对于判断某个变量的值并根据结果进行另外的操作，需要额外的控制确保整体的原子性。
+这个时候就可以用锁来保证原子性，但是Java从1.5开始JDK提供了<code>AtomicReference</code>类来保证引用对象之间的原子性，可以把多个变量放在一个对象里来进行CAS操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AtomicReferenceSimpleExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DataObject</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">var2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="nf">DataObject</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">var2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 AtomicReference 实例，并初始化为一个 DataObject 对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">DataObject</span><span class="o">&gt;</span><span class="w"> </span><span class="n">atomicRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">DataObject</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Initial&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行 CAS 操作，修改 DataObject 对象的属性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">updateAndGet</span><span class="p">(</span><span class="n">data</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="p">.</span><span class="na">setVar1</span><span class="p">(</span><span class="n">data</span><span class="p">.</span><span class="na">getVar1</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="p">.</span><span class="na">setVar2</span><span class="p">(</span><span class="s">&#34;Updated&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取修改后的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DataObject</span><span class="w"> </span><span class="n">updatedObject</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Updated var1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">updatedObject</span><span class="p">.</span><span class="na">getVar1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Updated var2: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">updatedObject</span><span class="p">.</span><span class="na">getVar2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>ABA问题：ABA问题指的是，在CAS操作过程中，如果一个变量的值从A变成了B，然后再变回A，那么CAS操作会错误地认为变量的值未改变过。
+比如，线程1从内存位置V取出A，线程2同时也从内存取出A，并且线程2进行一些操作将值改为B，然后线程2又将V位置数据改成A，这时候线程1进行CAS操作发现内存中的值依然时A，然后线程1操作成功。尽管线程1的CAS操作成功，但是不代表这个过程没有问题。
+简而言之就是只比较结果，不比较过程。解决ABA问题的常见方法是使用版本号或者标记来跟踪变量的变化。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ABASolutionWithVersion</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始值为100，初始版本号为0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicStampedReference</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">atomicRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicStampedReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">100</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">stampHolder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// 用于获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w"> </span><span class="c1">// 期望值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">200</span><span class="p">;</span><span class="w"> </span><span class="c1">// 新值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟一个线程进行 ABA 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">getStamp</span><span class="p">();</span><span class="w"> </span><span class="c1">// 获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// 修改值和版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 再次修改回原值和新版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 其他线程进行 CAS 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">getStamp</span><span class="p">();</span><span class="w"> </span><span class="c1">// 获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;CAS Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出CAS操作结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h2 id="juc包">J.U.C.包</h2>
+<p><code>java.util.concurrent</code>，简称 J.U.C.。是Java并发工具包，提供了在多线程编程中常用的工具类和框架，帮助开发者简化并发编程的复杂性，并提高程序的性能和可靠性。</p>
+<p><code>java.util.concurrent.locks</code>包下常用的类与接口是<code>JDK1.5</code>后新增的。<code>lock</code>的出现是为了弥补<code>synchronized</code>关键字解决不了的一些问题。
+例如，当一个代码块被<code>synchronized</code>修饰了，一个线程获取了对应的锁，并执行该代码块时，其他线程只能一直等待，等待获取锁的线程释放锁。
+如果这个线程因为某些原因被堵塞了，没有释放锁，那么其他线程只能一直等待下去，导致效率很低。
+因此就需要有一种机制可以不让等待的线程一直无期限地等待下去，比如只等待一定的时间或者能够响应中断，通过<code>Lock</code>就可以办到。</p>
+<p><code>java.util.concurrent</code>包中的锁在<code>locks</code>包下：</p>
+<p><img alt="juc.locks" src="/iblog/posts/annex/images/essays/juc.locks.png"></p>
+<p><code>Lock</code>和<code>ReadWriteLock</code>是两大锁的根接口，<code>Lock</code>代表实现类是<code>ReentrantLock</code>，<code>ReadWriteLock</code>的代表实现类是<code>ReentrantReadWriteLock</code>。</p>
+<p>除了锁之外，<code>java.util.concurrent</code>包还提供了一些其他的工具类和框架，如<code>Semaphore</code>、<code>CountDownLatch</code>、<code>CyclicBarrier</code>等。</p>
+<h3 id="lock">Lock</h3>
+<p><code>Lock</code>接口在Java的<code>java.util.concurrent.locks</code>包中定义，用于实现更灵活的线程同步机制。与传统的 <code>synchronized</code> 关键字相比，<code>Lock</code>接口提供了更多的操作和更细粒度的控制。
+在实际使用中，自然是能够替代<code>synchronized</code>关键字的。</p>
+<p><code>Lock</code>接口中的方法：</p>
+<ul>
+<li><code>lock()</code>：<code>lock()</code>方法是平常使用得最多的一个方法，就是用来获取锁。如果锁已经被另一个线程持有，则当前线程将会被阻塞，直到锁被释放。
+如果使用<code>lock</code>方法必须主动去释放锁，并且在发生异常时，不会自动释放锁。因此使用<code>Lock</code>必须在<code>try-catch</code>块中进行，并且将释放锁的操作放在<code>finally</code>块中进行，以保证锁一定被被释放，防止死锁的发生。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>lockInterruptibly()</code>：获取锁，但与<code>lock()</code>方法不同，它允许线程在等待获取锁的过程中被中断。
+例如，当两个线程同时通过<code>lock.lockInterruptibly()</code>想获取某个锁时，如果此时线程A获取到了锁，而线程B在等待，那么对线程B调用<code>threadB.interrupt()</code>能够中断线程B的等待过程。
+当一个线程获取了锁之后，是不会被<code>interrupt()</code>方法中断的。因为<code>interrupt()</code>方法只能中断阻塞过程中的线程而不能中断正在运行过程中的线程。与 <code>synchronized</code> 相比，当一个线程处于等待某个锁的状态，是无法被中断的，只有一直等待下去。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">LockInterruptiblyExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lockInterruptibly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LockInterruptiblyExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LockInterruptiblyExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; was interrupted.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">interrupt</span><span class="p">();</span><span class="w"> </span><span class="c1">// Interrupt the second thread</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>trylock()</code>：该方法的作用是尝试获取锁，如果锁可用则返回<code>true</code>，不可用则返回<code>false</code>。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TryLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">.</span><span class="na">tryLock</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; could not acquire the lock.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TryLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TryLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">example</span><span class="p">::</span><span class="n">increment</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>newCondition</code>：<code>Lock</code>接口提供了方法<code>Condition newCondition();</code>，返回的<code>Condition</code>类型也是一个接口，<code>Condition</code>提供了更细粒度的线程通信控制，用于实现复杂的线程间协作。
+类似于<code>Object</code>类中的<code>wait()</code>、<code>notify()</code>和<code>notifyAll()</code>方法。
+<ul>
+<li><code>await()</code>：当前线程等待，直到被通知或被中断。</li>
+<li><code>signal()</code>：唤醒一个等待线程。如果所有线程都在等待，则任意选择一个线程唤醒。</li>
+<li><code>signalAll()</code>：唤醒所有等待线程。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConditionExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Condition</span><span class="w"> </span><span class="n">condition</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">newCondition</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">counter</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="n">condition</span><span class="p">.</span><span class="na">await</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">condition</span><span class="p">.</span><span class="na">signal</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">reset</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">condition</span><span class="p">.</span><span class="na">signal</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">ConditionExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConditionExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Runnable</span><span class="w"> </span><span class="n">incrementTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">example</span><span class="p">::</span><span class="n">increment</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Runnable</span><span class="w"> </span><span class="n">resetTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">example</span><span class="p">::</span><span class="n">reset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">incrementTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">resetTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="readwritelock">ReadWriteLock</h3>
+<p><code>ReadWriteLock</code>接口提供了一种用于在某些情况下可以显著提升并发性能的锁定机制。
+它允许多个读线程同时访问共享资源，但对写线程使用排他锁，这样读操作不会互相阻塞，而写操作会阻塞所有其他操作。</p>
+<p>该接口有两个方法：</p>
+<ul>
+<li><code>readLock()</code>：返回用于读取操作的锁。</li>
+<li><code>writeLock()</code>：返回用于写入操作的锁。</li>
+</ul>
+<p><code>ReadWriteLock</code>管理一组锁，一个是只读的锁，一个是写锁。Java并发库中<code>ReetrantReadWriteLock</code>实现了<code>ReadWriteLock</code>接口并添加了可重入的特性。
+对于<code>ReetrantReadWriteLock</code>其读锁是共享锁而写锁是独占锁，读锁的共享可保证并发读是非常高效的。需要注意的是，读写、写读、写写的过程是互斥的，只有读读不是互斥的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReadWriteLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReadWriteLock</span><span class="w"> </span><span class="n">readWriteLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">readLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">readWriteLock</span><span class="p">.</span><span class="na">readLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">writeLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">readWriteLock</span><span class="p">.</span><span class="na">writeLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 读操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">readValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">readLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; Reading: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">readLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 写操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeValue</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">writeLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; Writing: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReadWriteLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReadWriteLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">readTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">readValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">100</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟读取时间</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">writeTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">writeValue</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">150</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟写入时间</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">readTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">readTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">writeTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread3</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="locksupport">LockSupport</h3>
+<p><code>LockSupport</code>是<code>java.util.concurrent.locks</code>包下的一个工具类。它提供了最基本的线程阻塞和解除阻塞的功能，通常用来构建更高级的同步机制。
+其中有两个重要的方法，通过<code>park()</code>和<code>unpark()</code>方法来实现阻塞和唤醒线程的操作，可以理解为<code>wait()</code>和<code>notify()</code>的加强版。</p>
+<ul>
+<li><code>park()</code>：阻塞当前线程，直到线程被其他线程中断或调用<code>unpark()</code>方法唤醒。</li>
+<li><code>unpark()</code>：唤醒指定线程。如果该线程尚未阻塞，则下一次调用<code>park()</code>方法时不会阻塞。</li>
+</ul>
+<p>传统等待唤醒机制是使用<code>Object</code>中的<code>wait()</code>方法让线程等待，使用<code>Object</code>中的<code>notify()</code>方法唤醒线程。
+或者使用JUC包中<code>Condition</code>的<code>await()</code>方法让线程等待，使用<code>signal()</code>方法唤醒线程。</p>
+<p><code>wait()</code>和<code>notify()</code>/<code>await()</code>和<code>signal()</code>方法必须要在同步块或同步方法里且成对出现使用，如果没有在<code>synchronized</code>代码块使用则抛出<code>java.lang.IllegalMonitorStateException</code>。
+必须先<code>wait()</code>/<code>await()</code>后<code>notify()</code>/<code>signal()</code>，如果先<code>notify()</code>后<code>wait()</code>会出现另一个线程一直处于等待状态。</p>
+<p><code>LockSupport</code>对比传统等待唤醒机制，能够解决传统等待唤醒问题。
+<code>LockSupport</code>使用的是许可机制，而<code>wait/notify</code>使用的是监视器机制。每个线程最多只有一个许可，调用<code>park()</code>会消耗一个许可，如果有许可则会直接消耗这张许可然后退出，如果没有许可就堵塞等待许可可用。
+调用<code>unpark()</code>则会增加一个许可，连续调用多次<code>unpark()</code>和调用一次一样，只会增加一个许可。而且<code>LockSupport</code>的<code>park()</code>和<code>unpark()</code>是可中断的，且无需在同步块中使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">LockSupportProducerConsumer</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">consumer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Consumer waiting for resource&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">LockSupport</span><span class="p">.</span><span class="na">park</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Consumer consumed resource&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">producer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">2000</span><span class="p">);</span><span class="w"> </span><span class="c1">// Simulate some work with sleep</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">resource</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Producer produced resource&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">LockSupport</span><span class="p">.</span><span class="na">unpark</span><span class="p">(</span><span class="n">consumer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">consumer</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">producer</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>LockSupport</code>类使用了一种名为<code>Permit</code>的概念来做到阻塞和唤醒线程的功能，每个线程都有一个<code>Permit</code>，<code>Permit</code>只有两个值1和0，默认是0。
+官网解释<code>LockSupport</code>是用来创建锁和同步其他类的基本线程的阻塞原语。<code>LockSupport</code>最终调用的<code>Unsafe</code>中的<code>native</code>方法。以<code>unpark、park</code>为例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unpark</span><span class="p">(</span><span class="n">Thread</span><span class="w"> </span><span class="n">thread</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">thread</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">unpark</span><span class="p">(</span><span class="n">thread</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">park</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">blocker</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">setBlocker</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">blocker</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">park</span><span class="p">(</span><span class="kc">false</span><span class="p">,</span><span class="w"> </span><span class="n">0L</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">setBlocker</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="aqs">AQS</h3>
+<p>AQS是指<code>java.util.concurrent.locks</code>包下的一个抽象类<code>AbstractQueuedSynchronizer</code>译为，抽象的队列<strong>同步器</strong>。</p>
+<blockquote>
+<p>同步器是在多线程编程中用于管理线程间协作和同步的机制。同步器通常用于协调线程的执行顺序、控制共享资源的访问以及管理线程的状态。常见的同步器包括：CountDownLatch、CyclicBarrier、Semaphore等。</p>
+</blockquote>
+<p>在JUC包下，能够看到有许多类都继承了AQS，如<code>ReentrantLock</code>、<code>CountDownLatch</code>、<code>ReentrantReadWriteLock</code>、<code>Semaphore</code>。</p>
+<p><img alt="JUC.locks包UML" src="/iblog/posts/annex/images/essays/JUC.locks%E5%8C%85UML.png"></p>
+<p>AQS是用来构建锁或其它同步器组件的重要基础框架，以及是整个JUC体系的基石，它用于实现依赖先进先出队列的阻塞锁和相关的同步器。
+AQS提供了一个框架，用于创建在等待队列中具有独占或共享模式的同步器。</p>
+<p><img alt="AQS" src="/iblog/posts/annex/images/essays/AQS.png"></p>
+<p>AQS可以理解为一个框架，因为它定义了一些JUC包下常用&quot;锁&quot;的标准。
+AQS简单来说，包含一个<code>status</code>和一个队列。<code>status</code>保存线程持有锁的状态，用于判断该线程获没获取到锁，没获取到锁就去队列中排队。
+AQS中的队列，是指CLH队列（Craig， Landin， and Hagerste[三个人名组成]）锁队列的变体，是一个双向队列。
+队列中的元素即<code>Node</code>结点，每个<code>Node</code>中包含：头结点、尾结点、等待状态、存放的线程等。<code>Node</code>遵循从尾部入队，从头部出队的规则，即先进先出原则。</p>
+<p><img alt="AQS简单理解" src="/iblog/posts/annex/images/essays/AQS%E7%AE%80%E5%8D%95%E7%90%86%E8%A7%A3.png"></p>
+<p>在多线程并发环境下，使用<code>lock</code>加锁，当处在加锁与解锁之间的代码，只能有一个线程来执行。这时候其他线程不能够获取锁，如果不处理线程就会造成了堵塞。
+在AQS框架中，会将暂时获取不到锁的线程加入到队列里，这个队列就是AQS的抽象表现。它会将这些线程封装成队列的结点，通过CAS、自旋以及<code>LockSupport.park()</code>的方式，维护<code>state</code>变量的状态，使并发达到同步的效果。</p>
+<h3 id="reentrantlock">ReentrantLock</h3>
+<p><code>ReentrantLock</code>译为可重入锁，是一种锁的实现类，它提供了比<code>synchronized</code>关键字更广泛的锁定操作选项，提供了公平锁和非公平锁两种模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReentrantLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; incremented counter to &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReentrantLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">100</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="对比synchronized">对比synchronized</h4>
+<p>Java提供了两种锁机制来控制多个线程对共享资源的互斥访问，第一个是JVM实现的 <code>synchronized</code>，而另一个是 JDK 实现的 <code>ReentrantLock</code>。</p>
+<table>
+<thead>
+<tr>
+<th>比较</th>
+<th>synchronized</th>
+<th>ReentrantLock</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>锁的实现</td>
+<td>JVM实现</td>
+<td>JDK实现</td>
+</tr>
+<tr>
+<td>性能</td>
+<td>synchronized 与 ReentrantLock 大致相同</td>
+<td>synchronized 与 ReentrantLock 大致相同</td>
+</tr>
+<tr>
+<td>等待可中断</td>
+<td>不可中断</td>
+<td>可中断</td>
+</tr>
+<tr>
+<td>公平锁</td>
+<td>非公平锁</td>
+<td>默认非公平锁，也可以是公平锁</td>
+</tr>
+<tr>
+<td>锁绑定多个条件</td>
+<td>不能绑定</td>
+<td>可以同时绑定多个Condition对象</td>
+</tr>
+<tr>
+<td>可重入</td>
+<td>可重入锁</td>
+<td>可重入锁</td>
+</tr>
+<tr>
+<td>释放锁</td>
+<td>自动释放锁</td>
+<td>调用 unlock() 释放锁</td>
+</tr>
+<tr>
+<td>等待唤醒</td>
+<td>搭配wait()、notify或notifyAll()使用</td>
+<td>搭配await()/singal()使用</td>
+</tr>
+</tbody>
+</table>
+<p><code>synchronized</code>与<code>ReentrantLock</code>最直观的区别就是，在使用<code>ReentrantLock</code>的时候需要调用<code>unlock</code>方法释放锁，所以为了保证一定释放，通常都是和 <code>try-finally</code> 配合使用的。
+在实际开发中除非需要使用<code>ReentrantLock</code>的高级功能，否则优先使用<code>synchronized</code>。
+这是因为<code>synchronized</code>是JVM实现的一种锁机制，JVM原生地支持它，而<code>ReentrantLock</code>不是所有的JDK版本都支持。并且使用<code>synchronized</code>不用担心没有释放锁而导致死锁问题，因为JVM会确保锁的释放。</p>
+<h4 id="加锁原理">加锁原理</h4>
+<p><code>ReentrantLock</code>原理用到了AQS，而AQS包括一个线程队列和一个<code>state</code>变量，<code>state</code>，它的值有3种状态：没占用是0，占用了是1，大于1是可重入锁。
+所以<code>ReentrantLock</code>加锁过程，可以简单理解为<code>state</code>变量的变化。</p>
+<p>在多线程并发环境下，某个线程持有锁，将<code>state</code>由0设置为1，如果有其他线程再次进入，线程则会经过一系列判断，然后构建<code>Node</code>结点，最终形成双向链表结构。
+最后执行<code>LockSupport.park()</code>方法，将等待的线程挂起，如果当前持有锁的线程释放了锁，则将<code>state</code>变量设置为0，调用<code>LockSpoort.unpark()</code>方法指定唤醒等待队列中的某个线程。</p>
+<p><img alt="reentrantLock加锁" src="/iblog/posts/annex/images/essays/reentrantLock%E5%8A%A0%E9%94%81.png"></p>
+<p><code>ReentrantLock</code>加锁有两种形式，默认是非公平锁，但可以通过构造方法来指定为公平锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">reentrantLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an instance of {@code ReentrantLock} with the
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * given fairness policy.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @param fair {@code true} if this lock should use a fair ordering policy
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">ReentrantLock</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">fair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sync</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fair</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FairSync</span><span class="p">()</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NonfairSync</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>无论是公平锁还是非公平锁，由于用到了AQS框架，所以底层实现的逻辑大致是差不多的，<code>ReentrantLock</code>加锁核心方法调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">lock()
+</span></span><span class="line"><span class="cl">    --&gt; acquire()
+</span></span><span class="line"><span class="cl">    --&gt; tryAcquire()
+</span></span><span class="line"><span class="cl">    --&gt; addWaiter()
+</span></span><span class="line"><span class="cl">    --&gt; acquireQueued()
+</span></span><span class="line"><span class="cl">    --&gt; selfInterrupt()
+</span></span></code></pre></div><p>公平锁还是非公平锁虽然大致逻辑差不多，但是区别总是有的，总的来说非公平锁比非公平锁在代码里面多了几行判断。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// ===========重写 lock 方法对比===========</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">lock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">acquire</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 非公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">lock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetState</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setExclusiveOwnerThread</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquire</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">acquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">tryAcquire</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquireQueued</span><span class="p">(</span><span class="n">addWaiter</span><span class="p">(</span><span class="n">Node</span><span class="p">.</span><span class="na">EXCLUSIVE</span><span class="p">),</span><span class="w"> </span><span class="n">arg</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">selfInterrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// ===========重写 tryAcquire 方法对比===========</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">protected</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">tryAcquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">acquires</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">c</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">hasQueuedPredecessors</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">compareAndSetState</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">acquires</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setExclusiveOwnerThread</span><span class="p">(</span><span class="n">current</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">current</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">getExclusiveOwnerThread</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">nextc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">acquires</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nextc</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="s">&#34;Maximum lock count exceeded&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">setState</span><span class="p">(</span><span class="n">nextc</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 非公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">protected</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">tryAcquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">acquires</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">nonfairTryAcquire</span><span class="p">(</span><span class="n">acquires</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">nonfairTryAcquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">acquires</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">c</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetState</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">acquires</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setExclusiveOwnerThread</span><span class="p">(</span><span class="n">current</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">current</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">getExclusiveOwnerThread</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">nextc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">acquires</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nextc</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="c1">// overflow</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="s">&#34;Maximum lock count exceeded&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">setState</span><span class="p">(</span><span class="n">nextc</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在重写的<code>tryAcquire</code>方法里，公平锁在获取同步状态时多了一个限制条件即<code>hasQueuedPredecessors()</code>方法。该方法作用是保证等待队列中的线程按照从头到尾的顺序排队获取锁。
+举个例子，目前队列中有两个线程A、B，线程A，在线程B的前面。在当前线程释放锁的时候，线程B获取到了锁，该方法会判断当前头结点的下一个结点中存放的线程跟当前线程是否相同。
+在这个例子中头结点的下一个结点存放的线程是傀儡结点线程为<code>null</code>，而当前线程是线程B，所以返回<code>true</code>，回到上一个方法<code>true</code>取反就是<code>false</code>所以获取锁失败。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">hasQueuedPredecessors</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// The correctness of this depends on head being initialized</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// before tail and on head.next being accurate if the current</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// thread is first in queue.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">;</span><span class="w"> </span><span class="c1">// Read fields in reverse initialization order</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">s</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">((</span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">h</span><span class="p">.</span><span class="na">next</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">thread</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在执行完<code>tryAcquire</code>方法之后就会执行<code>addWaiter</code>方法。
+<code>addWaiter</code>方法作用为，当第一次将等待的线程添加到队列时，先会调用<code>enq</code>方法。
+如果不是第一次调用，即尾结点不为空，队列中已经有了其他线程结点，则会直接将当前线程的前结点指向尾结点，即队列中最后一个线程结点。
+然后用CAS将前一个结点的下一个结点指向当前结点，形成链表结构，最后返回添加到队列中的结点。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">addWaiter</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">mode</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">(),</span><span class="w"> </span><span class="n">mode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Try the fast path of enq; backup to full enq on failure</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">pred</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pred</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">node</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pred</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetTail</span><span class="p">(</span><span class="n">pred</span><span class="p">,</span><span class="w"> </span><span class="n">node</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">pred</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">enq</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>enq</code>方法作用是将等待获取锁的线程封装成<code>Node</code>结点，并将<code>Node</code>结点串联起来，形成双向链表结构，简而言之就是将线程添加到等待队列中去。                                                                <br>
+该方法运用自旋机制，如果添加的结点为第一个结点，则会在第一个实际结点之前，生成一个“傀儡结点”。添加的第一个结点的前结点指向傀儡结点，尾结点指向实际结点。傀儡结点的后结点则指向添加的第一个结点。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">enq</span><span class="p">(</span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(;;)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">t</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// Must initialize</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetHead</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">()))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">t</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetTail</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">node</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">t</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">t</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>之后执行<code>acquireQueued</code>方法，该方法用到了自旋机制。首先判断当前结点是否为头结点，如果是头结点，就让头结点中的线程尝试获取锁。
+如果不是头结点，执行<code>shouldParkAfterFailedAcquire</code>方法尝试让当前线程挂起，直到持有锁的线程释放锁，唤醒等待的线程之后再去尝试获取锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">acquireQueued</span><span class="p">(</span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">failed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">interrupted</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(;;)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">predecessor</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">p</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">tryAcquire</span><span class="p">(</span><span class="n">arg</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">setHead</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">p</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="c1">// help GC</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">failed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">interrupted</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">shouldParkAfterFailedAcquire</span><span class="p">(</span><span class="n">p</span><span class="p">,</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parkAndCheckInterrupt</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">interrupted</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">failed</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">cancelAcquire</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>shouldParkAfterFailedAcquire</code>方法，该方法首先判断上一个结点的<code>waitStatus</code>。
+如果该队列只有一个结点，则上一个结点为头结点，此时头结点的<code>waitStatus=0</code>，经过该方法会将上一个结点的<code>waitStatus</code>通过CAS，设置为-1。
+因为最外部是一个自旋机制，会一直循环，所以当第二次进入该方法，则会直接返回<code>true</code>。返回<code>true</code>意味着当前线程将进入堵塞状态，会执行<code>parkAndCheckInterrupt()</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">shouldParkAfterFailedAcquire</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">pred</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">ws</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pred</span><span class="p">.</span><span class="na">waitStatus</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ws</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Node</span><span class="p">.</span><span class="na">SIGNAL</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ws</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pred</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pred</span><span class="p">.</span><span class="na">prev</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">pred</span><span class="p">.</span><span class="na">waitStatus</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pred</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">compareAndSetWaitStatus</span><span class="p">(</span><span class="n">pred</span><span class="p">,</span><span class="w"> </span><span class="n">ws</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p">.</span><span class="na">SIGNAL</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>parkAndCheckInterrupt</code>方法，底层是调用<code>LockSupport.park()</code>方法让线程挂起，直到持有锁的线程将它们唤醒。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">parkAndCheckInterrupt</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">LockSupport</span><span class="p">.</span><span class="na">park</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">interrupted</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ReentrantLock</code>其加锁核心方法为<code>acquire</code>方法。最终执行完毕，下面的<code>if</code>表达式返回<code>true</code>，则执行<code>selfInterrupt</code>方法中断线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">acquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">tryAcquire</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquireQueued</span><span class="p">(</span><span class="n">addWaiter</span><span class="p">(</span><span class="n">Node</span><span class="p">.</span><span class="na">EXCLUSIVE</span><span class="p">),</span><span class="w"> </span><span class="n">arg</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">selfInterrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ReentrantLock</code>在采用非公平锁构造时，首先检查锁状态，如果锁可用，直接通过CAS设置成持有状态，且把当前线程设置为锁的拥有者。
+如果当前锁已经被持有，那么接下来进行可重入检查，如果可重入，需要为锁状态加上请求数。如果不属于上面两种情况，那么说明锁是被其他线程持有，当前线程应该放入等待队列。</p>
+<p>在放入等待队列的过程中，首先要检查队列是否为空队列，如果为空队列，需要创建虚拟的头节点，然后把对当前线程封装的节点加入到队列尾部。
+由于设置尾部节点采用了CAS，为了保证尾节点能够设置成功，<code>ReentrantLock</code>采用了无限循环的方式，直到设置成功为止。</p>
+<p>在完成放入等待队列任务后，则需要维护节点的状态，以及及时清除处于<code>Cancel</code>状态的节点，来帮助垃圾收集器及时回收。
+如果当前节点之前的节点的等待状态小于1，说明当前节点之前的线程处于等待状态，那么当前节点的线程也应处于等待状态。通过<code>LockSupport</code>类实现等待挂起的功能。
+当等待的线程被唤起后，检查中断状态，如果处于中断状态，那么需要中断当前线程。</p>
+<h4 id="释放锁原理">释放锁原理</h4>
+<p><img alt="reentrantLock解锁" src="/iblog/posts/annex/images/essays/reentrantLock%E8%A7%A3%E9%94%81.png"></p>
+<p><code>ReentrantLock</code>释放锁调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">unlock()
+</span></span><span class="line"><span class="cl">    --&gt; release()
+</span></span><span class="line"><span class="cl">    --&gt; tryRelease()
+</span></span><span class="line"><span class="cl">    --&gt; unparkSuccessor()
+</span></span></code></pre></div><p>在<code>release</code>方法中如果<code>tryRelease</code>方法返回<code>true</code>，则判断队列头结点中的<code>waitStatus</code>，如果不等于0则执行<code>unparkSuccessor</code>方法，按顺序唤醒队列中等待的线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">release</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tryRelease</span><span class="p">(</span><span class="n">arg</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">h</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">h</span><span class="p">.</span><span class="na">waitStatus</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">unparkSuccessor</span><span class="p">(</span><span class="n">h</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>tryRelease</code>方法作用是尝试释放锁，首先获取当前持有锁线程的<code>state</code>变量并使其减1。
+如果减1后的<code>state</code>值等于0，则认为该线程马上要释放锁，将当前持有锁的线程设置为<code>null</code>，将0设置为<code>state</code>的新值并返回<code>true</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">tryRelease</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">releases</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getState</span><span class="p">()</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">releases</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">getExclusiveOwnerThread</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalMonitorStateException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">c</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">setExclusiveOwnerThread</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">setState</span><span class="p">(</span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">free</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>unparkSuccessor</code>方法用于唤醒等待队列中的后继节点。首先判断当前节点的等待状态如果小于0，将其设置为0。
+然后从尾部开始向前查找，直到找到一个有效的后继节点，如果找到一个有效的后继节点，唤醒其线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unparkSuccessor</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">ws</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">waitStatus</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ws</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">compareAndSetWaitStatus</span><span class="p">(</span><span class="n">node</span><span class="p">,</span><span class="w"> </span><span class="n">ws</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">waitStatus</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">;</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">t</span><span class="p">.</span><span class="na">prev</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">t</span><span class="p">.</span><span class="na">waitStatus</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">t</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LockSupport</span><span class="p">.</span><span class="na">unpark</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">thread</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="countdownlatch">CountDownLatch</h3>
+<p><code>count down latch</code>直译为倒计时门闩，也可以叫做闭锁。</p>
+<blockquote>
+<p>门闩，汉语词汇。拼音：mén shuān 释义：指门关上后，插在门内使门推不开的滑动插销。</p>
+</blockquote>
+<p><code>CountDownLatch</code>JDK文档注释：</p>
+<blockquote>
+<p>A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes.</p>
+</blockquote>
+<p>文档大意：一种同步辅助工具，允许一个或多个线程等待，直到在其他线程中执行的一组操作完成。</p>
+<p><code>CountDownLatch</code>是Java中的一个同步工具类，用于使一个或多个线程等待其他线程完成一组操作。<code>CountDownLatch</code>通过一个计数器实现，该计数器的初始值由构造方法指定，底层还是AQS。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="nf">CountDownLatch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">count</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;count &lt; 0&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">this</span><span class="p">.</span><span class="na">sync</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Sync</span><span class="p">(</span><span class="n">count</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>每调用一次<code>countDown()</code>方法，计数器减一，当计数器到达零时，所有因调用<code>await()</code>方法而等待的线程都将被唤醒。
+举个例子，晚上教室关门，要等同学都离开之后，再关门：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CountDownLatch</span><span class="w"> </span><span class="n">countDownLatch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CountDownLatch</span><span class="p">(</span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">7</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;同学&#34;</span><span class="o">+</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 离开&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">countDownLatch</span><span class="p">.</span><span class="na">countDown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">countDownLatch</span><span class="p">.</span><span class="na">await</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;关门...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="cyclicbarrier">CyclicBarrier</h3>
+<p><code>Cyclic Barrier</code>直译为循环屏障，是Java中关于线程的计数器，也可以叫它栅栏。</p>
+<p><code>CyclicBarrier</code>JDK文档注释：</p>
+<blockquote>
+<p>A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point.  CyclicBarriers are useful in programs involving a fixed sized party of threads that must occasionally wait for each other. The barrier is called <em>cyclic</em> because it can be re-used after the waiting threads are released.</p>
+</blockquote>
+<p>文档大意：一种同步辅助工具，允许一组线程相互等待到达一个共同的障碍点。<code>cyclicbarrier</code>在包含固定大小的线程组的程序中非常有用，这些线程必须偶尔相互等待。
+这个屏障被称为<code>cyclic</code>，因为它可以在等待的线程被释放后被重用。</p>
+<p>它与<code>CountDownLatch</code>的作用是相反的，<code>CountDownLatch</code>是定义一个次数，然后减直到减到0，再去执行一些任务。
+而<code>CyclicBarrier</code>是定义一个上限次数，从零开始加，直到加到定义的上限次数，再去执行一些任务。
+<code>CountDownLatch</code>的计数器只能使用一次，而<code>CyclicBarrier</code>的计数器可以使用<code>reset()</code>方法重置，可以使用多次，所以<code>CyclicBarrier</code>能够处理更为复杂的场景。
+例如，凑齐七颗龙珠召唤神龙：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CyclicBarrier</span><span class="w"> </span><span class="n">cyclicBarrier</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CyclicBarrier</span><span class="p">(</span><span class="n">7</span><span class="p">,()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;凑齐七颗龙珠，召唤神龙！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">7</span><span class="p">;</span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;拿到&#34;</span><span class="o">+</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;星龙珠&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">cyclicBarrier</span><span class="p">.</span><span class="na">await</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">BrokenBarrierException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CyclicBarrier</code>要做的事情是，让一组线程达到一个屏障时被阻塞，直到最后一个线程达到屏障时，所有被屏障拦截的线程才会继续干活，线程进入屏障通过<code>CyclicBarrier.await()</code>方法。</p>
+<p><img alt="CyclicBarrier" src="/iblog/posts/annex/images/essays/CyclicBarrier.gif"></p>
+<p><code>CyclicBarrier</code>是基于<code>ReentrantLock</code>实现的，其底层也是基于AQS。
+<code>CyclicBarrier</code>通过一个内部的计数器和一个锁来实现线程间的协调。当所有线程都调用<code>await</code>方法时，计数器递减，当计数器为零时，所有等待的线程将被唤醒，并重置计数器，以便下一次使用。</p>
+<h3 id="semaphore">Semaphore</h3>
+<p><code>Semaphore</code>译为信号量，有时被称为信号灯。可以用来控制同时访问特定资源的线程数量，通过协调各个线程，保证合理的使用资源。
+信号量主要用于两个目的，一个是用于多个共享资源的互斥使用，另一个用于并发线程数量的控制。</p>
+<p><code>Semaphore</code>JDK文档注释：</p>
+<blockquote>
+<p>A counting semaphore.  Conceptually, a semaphore maintains a set of permits.  Each {@link #acquire} blocks if necessary until a permit is available, and then takes it.  Each {@link #release} adds a permit, potentially releasing a blocking acquirer.</p>
+</blockquote>
+<p>文档大意：<code>Semaphore</code>是一个计数信号量。从概念上讲，信号量维护一组许可。如果需要，每个<code>acquire</code>方法调用会阻塞，直到有一个许可可用，然后获取许可。
+每个<code>release</code>方法调用会添加一个许可，可能会释放一个阻塞的线程。实际上，<code>Semaphore</code>并没有维护实际的许可对象，只是维护一个可用许可的计数，并根据计数执行相应的操作。</p>
+<p>举个例子，九辆车抢三个车位，车位满了之后只有等里面的车离开停车场外面的车才可以进入。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Semaphore</span><span class="w"> </span><span class="n">semaphore</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Semaphore</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">9</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">semaphore</span><span class="p">.</span><span class="na">acquire</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;辆车，抢到车位&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">2000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;停车结束.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">semaphore</span><span class="p">.</span><span class="na">release</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Semaphore</code>通过一个计数器和一个队列来管理许可和等待线程。它依赖于AQS来实现同步逻辑。
+<code>Semaphore</code>是用来保护一个或者多个共享资源的访问，<code>Semaphore</code>内部维护了一个计数器，其值为可以访问的共享资源的个数。
+一个线程要访问共享资源，先获得信号量，如果信号量的计数器值大于1，意味着有共享资源可以访问，则使其计数器值减去1，再访问共享资源。
+如果计数器值为0，线程进入休眠。当某个线程使用完共享资源后，释放信号量，并将信号量内部的计数器加1，之前进入休眠的线程将被唤醒并再次试图获得信号量。</p>
+<p><code>Semaphore</code>的核心方法为：</p>
+<ul>
+<li><code>acquire()</code>：获取一个许可，如果没有可用的许可，当前线程将被阻塞，直到有许可可用。
+当调用<code>semaphore.acquire()</code>方法时，当前线程会尝试去同步队列获取一个令牌，获取令牌的过程也就是使用原子操作去修改同步队列的<code>state</code>，获取一个令牌则修改为<code>state=state-1</code>。
+当计算出来的<code>state&lt;0</code>，则代表令牌数量不足，此时会创建一个<code>Node</code>节点加入阻塞队列，挂起当前线程。当计算出来的<code>state&gt;=0</code>，则代表获取令牌成功。</li>
+<li><code>release()</code>：释放一个许可，将其返回到<code>Semaphore</code>。
+当调用<code>semaphore.release()</code>方法时，线程会尝试释放一个令牌，释放令牌的过程也就是把同步队列的<code>state</code>修改为<code>state=state+1</code>的过程。
+释放令牌成功之后，同时会唤醒同步队列中的一个线程。被唤醒的节点会重新尝试去修改<code>state=state-1</code>的操作，如果<code>state&gt;=0</code>则获取令牌成功，否则重新进入阻塞队列，挂起线程。</li>
+</ul>
+<h2 id="threadlocal">ThreadLocal</h2>
+<p><code>ThreadLocal</code>文档注释：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">This class provides thread-local variables.
+</span></span><span class="line"><span class="cl">These variables differ from their normal counterparts in that each thread that accesses one (via its {@code get} or {@code set} method) has its own,
+</span></span><span class="line"><span class="cl">independently initialized copy of the variable. 
+</span></span></code></pre></div><p>文档大意：这个类提供线程局部变量。这些变量与普通变量的不同之处在于，每个访问它们的线程(通过其get方法或set方法)都有自己的独立初始化的变量副本。</p>
+<p>如文档注释所说，<code>ThraedLocal</code>为每个使用该变量的线程提供独立的变量副本，所以每一个线程都可以独立地改变自己的副本，而不会影响其它线程所对应的副本。
+每个访问<code>ThreadLocal</code>变量的线程都有自己的隔离副本，这样防止了线程之间的干扰，消除了同步的需要。
+从线程的角度看，目标变量就象是线程的本地变量，这也是类名中“Local”所要表达的意思。说白了<code>ThreadLocal</code>就是存放线程的局部变量的。</p>
+<h3 id="对比线程同步">对比线程同步</h3>
+<p><code>ThreadLocal</code>是修饰变量的，重点是在控制变量的作用域，初衷不是为了解决线程并发和线程冲突的，而是为了让变量的种类变的更多更丰富，方便使用。很多开发语言在语言级别都提供这种作用域的变量类型。</p>
+<p>其实要保证线程安全，并不一定就是要进行同步，两者没有因果关系。同步只是保证共享数据竞争时的手段。如果一个方法本来就不涉及共享数据，那它自然就无需任何同步措施去保证正确性。
+线程安全，并不一定就是要进行同步，<code>ThreadLocal</code>目的是线程安全，但不是同步手段。</p>
+<p><code>ThreadLocal</code>和线程同步机制都可以解决多线程中共享变量的访问冲突问题。
+在同步机制中，通过对象的锁机制保证同一时间只有一个线程访问变量。使用同步机制要求程序谨慎地分析什么时候对变量进行读写，什么时候需要锁定某个对象，什么时候释放对象锁等繁杂的问题，程序设计和编写难度相对较大。
+而<code>ThreadLocal</code> 则从另一个角度来解决多线程的并发访问。<code>ThreadLocal</code>会为每一个线程提供一个独立的变量副本，从而隔离了多个线程对数据的访问冲突。因为每一个线程都拥有自己的变量副本，从而也就没有必要对该变量进行同步了。
+<code>ThreadLocal</code>提供了线程安全的共享对象，在编写多线程代码时，可以把不安全的变量封装进<code>ThreadLocal</code>。</p>
+<p>虽然<code>ThreadLocal</code>能够保证多线程访问数据安全，但是由于在每个线程中都创建了副本，所以要考虑它对资源的消耗，比如内存的占用会比不使用<code>ThreadLocal</code>要大。
+对于多线程资源共享的问题，同步机制采用了“以时间换空间”的方式，而<code>ThreadLocal</code>采用了“以空间换时间”的方式。前者仅提供一份变量，让不同的线程排队访问，而后者为每一个线程都提供了一份变量，因此可以同时访问而互不影响。</p>
+<h3 id="使用示例-2">使用示例</h3>
+<p>在JDK5.0中，<code>ThreadLocal</code>已经支持泛型，该类的类名已经变为<code>ThreadLocal&lt;T&gt;</code>。API方法也相应进行了调整，新版本的API方法分别是<code>void set(T value)</code>、<code>T get()</code>。</p>
+<p><code>ThreadLocal</code>中主要有三个方法：</p>
+<ul>
+<li><code>set()</code>：设置当前线程的线程局部变量的值。</li>
+<li><code>get()</code>：该方法返回当前线程所对应的线程局部变量。</li>
+<li><code>remove()</code>：删除当前线程的线程局部变量，目的是为了减少内存的占用。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ThreadLocalExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 创建一个 ThreadLocal 变量，用于存储每个线程独立的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ThreadLocal</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadLocal</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 设置线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="s">&#34;Thread-1&#39;s Value&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并打印线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 删除线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">remove</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; after remove: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 设置线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="s">&#34;Thread-2&#39;s Value&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并打印线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 删除线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">remove</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; after remove: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>除此之外，<code>ThreadLocal</code>提供了一个<code>withInitial()</code>方法统一初始化所有线程的<code>ThreadLocal</code>的值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ThreadLocalWithInitialExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 使用 withInitial 方法提供初始值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ThreadLocal</span><span class="o">&lt;</span><span class="n">SimpleDateFormat</span><span class="o">&gt;</span><span class="w"> </span><span class="n">dateFormat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ThreadLocal</span><span class="p">.</span><span class="na">withInitial</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SimpleDateFormat</span><span class="p">(</span><span class="s">&#34;yyyy-MM-dd&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并打印线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">SimpleDateFormat</span><span class="w"> </span><span class="n">df</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dateFormat</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">formattedDate</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">df</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">formattedDate</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 删除线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">dateFormat</span><span class="p">.</span><span class="na">remove</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并打印线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">SimpleDateFormat</span><span class="w"> </span><span class="n">df</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dateFormat</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">formattedDate</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">df</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">formattedDate</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 删除线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">dateFormat</span><span class="p">.</span><span class="na">remove</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ThreadLocal</code>是一种强大的工具，适用于需要线程隔离的场景，如用户会话、数据库连接和格式化对象等。
+使用<code>ThreadLocal</code>可以有效地管理线程本地的数据，避免多线程环境下的竞争和数据一致性问题。
+但是由于<code>ThreadLocal</code>的生命周期与线程相关，如果在线程池中使用<code>ThreadLocal</code>，需要注意及时调用<code>remove()</code>方法清理线程局部变量，来防止内存泄漏。</p>
+<h3 id="实现原理-2">实现原理</h3>
+<p><code>ThreadLocal</code>类本身并不存储线程本地变量的值，而是通过<code>ThreadLocalMap</code>来实现。
+每个线程内部都有一个<code>ThreadLocalMap</code>实例，<code>ThreadLocal</code>变量作为<code>ThreadLocalMap</code>的键，存储的值是该线程对应的变量值。</p>
+<p><code>set</code>方法首先获取当前线程 <code>Thread</code> 对象，然后获取该线程的 <code>ThreadLocalMap</code> 实例。如果存在，则将值存储在 <code>ThreadLocalMap</code> 中；否则，创建一个新的 <code>ThreadLocalMap</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">set</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 每个线程 都有一个自己的ThreadLocalMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ThreadLocalMap 里就保存着所有的ThreadLocal变量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getMap</span><span class="p">(</span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 向map里添加值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// map为null，创建一个 ThreadLocalMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">createMap</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 全局定义的localMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">ThreadLocal</span><span class="p">.</span><span class="na">ThreadLocalMap</span><span class="w"> </span><span class="n">threadLocals</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 获取当前线程所持有的localMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="nf">getMap</span><span class="p">(</span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">t</span><span class="p">.</span><span class="na">threadLocals</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 创建，初始化 localMap </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">void</span><span class="w"> </span><span class="nf">createMap</span><span class="p">(</span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">firstValue</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">t</span><span class="p">.</span><span class="na">threadLocals</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadLocalMap</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">firstValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>get</code>方法同样先获取当前线程 <code>Thread</code> 对象，然后获取该线程的 <code>ThreadLocalMap</code> 实例。再通过 <code>ThreadLocal</code> 对象作为键从 <code>ThreadLocalMap</code> 中获取值。如果键不存在，则调用 <code>setInitialValue</code> 方法初始化变量。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">get</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 每个线程 都有一个自己的ThreadLocalMap，</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ThreadLocalMap里就保存着所有的ThreadLocal变量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getMap</span><span class="p">(</span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//ThreadLocalMap的key就是当前ThreadLocal对象实例，</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//多个ThreadLocal变量都是放在这个map中的</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ThreadLocalMap</span><span class="p">.</span><span class="na">Entry</span><span class="w"> </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">getEntry</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//从map里取出来的值就是我们需要的这个ThreadLocal变量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">T</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="p">)</span><span class="n">e</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果map没有初始化，那么在这里初始化一下</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">setInitialValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 全局定义的localMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">ThreadLocal</span><span class="p">.</span><span class="na">ThreadLocalMap</span><span class="w"> </span><span class="n">threadLocals</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 获取当前线程所持有的localMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="nf">getMap</span><span class="p">(</span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">t</span><span class="p">.</span><span class="na">threadLocals</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>setInitialValue</code> 方法通过 <code>initialValue</code> 方法获取初始值，并存储在 <code>ThreadLocalMap</code> 中。如果 <code>initialValue</code> 方法未被重写，默认返回 <code>null</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">setInitialValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">initialValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getMap</span><span class="p">(</span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">createMap</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">protected</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">initialValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ThreadLocalMap</code>是一个自定义的哈希表，其中每个元素是一个<code>Entry</code>对象。
+<code>ThreadLocalMap</code>是一个比较特殊的<code>Map</code>，它的每个<code>Entry</code>的<code>key</code>都是一个弱引用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Entry</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WeakReference</span><span class="o">&lt;</span><span class="n">ThreadLocal</span><span class="o">&lt;?&gt;&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The value associated with this ThreadLocal. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Object</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//key就是一个弱引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="p">(</span><span class="n">ThreadLocal</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">k</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">v</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">k</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">v</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这样设计的好处是，如果这个变量不再被其他对象使用时，可以自动回收这个<code>ThreadLocal</code>对象，避免可能的内存泄露。</p>
+<h3 id="内存泄漏问题">内存泄漏问题</h3>
+<p>虽然<code>ThreadLocalMap</code>中的<code>key</code>是弱引用，当不存在外部强引用的时候，就会自动被回收。但是<code>Entry</code>中的<code>value</code>依然是强引用，<code>value</code>的引用链条如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread --&gt; ThreadLocalMap --&gt; Entry --&gt; value
+</span></span></code></pre></div><p>只有当<code>Thread</code>被回收时，这个<code>value</code>才有被回收的机会，否则只要线程不退出，<code>value</code>总是会存在一个强引用。
+但是要求每个<code>Thread</code>都会退出，是一个极其苛刻的要求，对于线程池来说，大部分线程会一直存在在系统的整个生命周期内，那样的话就会造成<code>value</code>对象出现泄漏的可能。</p>
+<p>如果<code>get()</code>方法总是访问固定几个一直存在的<code>ThreadLocal</code>，那么清理动作就不会执行，如果你没有机会调用<code>set()</code>和<code>remove()</code>，那么这个内存泄漏依然会发生。
+所以当你不需要这个<code>ThreadLocal</code>变量时，主动调用<code>remove()</code>，这样是能够避免内存泄漏的。可以将<code>ThreadLocal</code>的使用和清理放在<code>try-finally</code>块中，确保<code>remove()</code>方法总是会被调用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ThreadLocal&lt;MyClass&gt; threadLocal = new ThreadLocal&lt;&gt;();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    threadLocal.set(new MyClass());
+</span></span><span class="line"><span class="cl">    // 使用线程局部变量
+</span></span><span class="line"><span class="cl">} finally {
+</span></span><span class="line"><span class="cl">    threadLocal.remove();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>除此之外，应尽量避免将<code>ThreadLocal</code>对象声明为静态变量，特别是在应用服务器或类似环境中，因为它们的生命周期通常较长，会增加内存泄漏的风险。</p>
+<h2 id="常用线程安全的集合">常用线程安全的集合</h2>
+<p>在多线程环境中，数据的一致性和线程的安全性是至关重要的。传统的集合类，如<code>ArrayList</code>、<code>HashMap</code>和<code>HashSet</code>，在并发访问时并不安全，可能会导致数据不一致和其他并发问题。
+为了在并发编程中高效且安全地操作数据，Java提供了一系列线程安全的集合类来替代这些传统集合。</p>
+<table>
+<thead>
+<tr>
+<th>线程不安全</th>
+<th>线程安全替代</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>ArrayList</td>
+<td>CopyOnWriteArrayList</td>
+</tr>
+<tr>
+<td>HashSet</td>
+<td>CopyOnWriteArraySet</td>
+</tr>
+<tr>
+<td>HashMap</td>
+<td>HashTable、ConcurrentHashMap</td>
+</tr>
+</tbody>
+</table>
+<h3 id="copywritearraylist">CopyWriteArrayList</h3>
+<p><code>CopyOnWriteArrayList</code>是Java中的一种线程安全的<code>List</code>实现，适用于读操作远多于写操作的场景，该集合在线程不安全的情况下可替代<code>ArrayList</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrayList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">arrayList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">arrayList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CopyWriteArrayList</code>字面意思就是在写的时候复制，思想就是读写分离的思想。它的基本原理是每次修改操作都会创建该列表的一个新副本，因此读操作不需要加锁，可以并发执行。
+以下是<code>CopyOnWriteArrayList</code>的<code>add()</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The array, accessed only via getArray/setArray. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The lock protecting all mutators */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Gets the array.  Non-private so as to also be accessible
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * from CopyOnWriteArraySet class.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="nf">getArray</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Appends the specified element to the end of this list.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param e element to be appended to this list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@code true}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">lock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elements</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">newElements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elements</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newElements</span><span class="o">[</span><span class="n">len</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setArray</span><span class="p">(</span><span class="n">newElements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>保证了某个线程在写的时候不会被打断。
+可以看到源码开始先是复制了一份数组，同一时刻只有一个线程写，其余的线程会读。在复制的数组上边进行写操作，写好以后在返回<code>true</code>。
+这样就把读写进行了分离，写好以后因为<code>array</code>加了<code>volatile</code>修饰，所以该数组是对于其他的线程是可见的，就会读取到最新的值。</p>
+<p>由于每次写操作都会创建一个数组的新副本，所以写操作的开销较大。但是读取操作非常高效且不需要加锁，因此适用于读操作远多于写操作的场景，例如缓存、白名单等。
+不适合写操作频繁的场景，在这种情况下，<code>ConcurrentLinkedQueue</code>或<code>ConcurrentHashMap</code>等其他线程安全集合可能更合适。</p>
+<h3 id="copyonwritearrayset">CopyOnWriteArraySet</h3>
+<p><code>CopyOnWriteArraySet</code>是Java中一种线程安全的<code>Set</code>实现，内部使用了<code>CopyOnWriteArrayList</code>来存储元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">al</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an empty set.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">CopyOnWriteArraySet</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">al</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这种集合在读操作远多于写操作的场景中非常有用，因为它通过每次修改创建集合的副本来实现线程安全。
+因为底层用<code>CopyOnWriteArrayList</code>存储，所以写操作开销大，每次修改都会创建数组副本，适用场景有限。不适用于写操作频繁的场景，否则会导致高昂的内存和时间开销。
+与<code>CopyOnWriteArrayList</code>不同的是，<code>CopyOnWriteArraySet</code>不允许包含重复元素。如果尝试添加一个已经存在的元素，集合将保持不变，所以该集合在线程不安全的情况下可替代<code>HashSet</code>。
+<code>CopyOnWriteArraySet</code>适用于需要唯一性且不关心元素顺序的场景，例如维护一组独特的订阅者或监听器。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CopyOnWriteArraySetExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 CopyOnWriteArraySet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">cowSet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArraySet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w"> </span><span class="c1">// 不允许重复元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Set: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fruit</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">cowSet</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">fruit</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加新元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Grapes&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After adding Grapes: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After removing Banana: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hashtable">HashTable</h3>
+<p><code>HashTable</code>的出现是为了解决<code>HashMap</code>线程不安全的问题，但因为性能的原因，在多线程环境下很少使用，一般都会使用<code>ConcurrentHashMap</code>。<code>HashTable</code>性能低的原因，就是直接加了<code>synchronized</code>修饰。</p>
+<p><code>HashMap</code>中的方法大多没有同步，这意味着如果一个线程在遍历<code>HashMap</code>的同时，另一个线程修改了<code>HashMap</code>，例如添加或删除元素，可能会导致<code>ConcurrentModificationException</code>。
+当遍历<code>HashTable</code>中的元素时，此时另一个线程来修改数据，这个时候加锁是没问题的。但是在没有另一个线程该数据的时候，<code>HashTable</code>还是加锁，这时性能就不太好了。可理解为<code>HashTable</code>性能不好的原因就是锁的粒度太粗了。</p>
+<p><code>Hashtable</code>的线程安全通过在方法级别使用<code>synchronized</code>关键字来实现，这确保了每次只有一个线程能够执行任何给定的方法。这种方法级别的锁定提供了基本的线程安全，但在高并发环境下会导致性能瓶颈。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HashtableExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 Hashtable</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Hashtable</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashtable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Hashtable</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashtable</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;One&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashtable</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Two&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashtable</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Three&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Value for key 1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">hashtable</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Value for key 2: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">hashtable</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashtable</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">hashtable</span><span class="p">.</span><span class="na">keySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Key: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Value: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">hashtable</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="concurrenthashmap">ConcurrentHashMap</h3>
+<p><code>ConcurrentHashMap</code>是Java中的一种线程安全的哈希表实现，用来替代传统的<code>HashMap</code>，来解决在多线程环境中并发修改带来的问题。
+与<code>Hashtable</code>不同，<code>ConcurrentHashMap</code>不对整个表进行全局加锁。相反它只对具体操作涉及的部分进行加锁，减少了线程之间的竞争。
+因为<code>HashMap</code>在JDK1.7与JDK1.8做了调整，所以<code>ConcurrentHashMap</code>在JDK1.7与JDK1.8实现也有所不同。</p>
+<h4 id="jdk17">JDK1.7</h4>
+<p>JDK1.7<code>ConcurrentHashMap</code>采用<code>segment</code>的分段锁机制实现线程安全，其中<code>segment</code>类继承自<code>ReentrantLock</code>。用<code>ReentrantLock</code>、CAS来保证线程安全。
+每个分段相当于一个独立的哈希表，并且分别加锁。</p>
+<p>需要注意的是JDK1.7中的ConcurrentHashMap，分段数量是固定。在创建<code>ConcurrentHashMap</code>实例时，必须指定初始的分段数量。
+这个初始的分段数量在实例创建后是不可动态修改的，也就是说一旦创建了<code>ConcurrentHashMap</code>，其分段数量就固定不变了。数组的长度就是<code>concurrencyLevel</code>指定的分段数量。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="nf">ConcurrentHashMap</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">initialCapacity</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">concurrencyLevel</span><span class="p">){}</span><span class="w">
+</span></span></span></code></pre></div><p>相比之下，JDK1.8中的<code>ConcurrentHashMap</code>改进了这一点，不再使用固定的分段数量，而是根据当前的容量动态调整分段的数量，从而更好地适应不同的并发场景，提升了并发性能和灵活性。</p>
+<p><img alt="jdk1.7ConcurrentHashMap" src="/iblog/posts/annex/images/essays/jdk1.7ConcurrentHashMap.png"></p>
+<p>整个<code>ConcurrentHashMap</code>被划分为多个分段，每个分段都是一个独立的哈希表。每个分段独立加锁，细化了锁的粒度，同时允许多个线程同时操作不同的分段，从而提高并发性能。
+使用<code>ReentrantLock</code>锁定分段，在执行插入、删除或更新操作时，只有操作涉及的分段会被锁定，其他分段不受影响。
+在进行插入操作时，先根据键的哈希值确定应该操作哪个分段，然后锁定该分段并进行操作。这种方法可以减少锁争用，提高并发性能。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public V put(K key， V value) {
+</span></span><span class="line"><span class="cl">    Segment&lt;K,V&gt; s;
+</span></span><span class="line"><span class="cl">    if (value == null)
+</span></span><span class="line"><span class="cl">        throw new NullPointerException();
+</span></span><span class="line"><span class="cl">    int hash = hash(key.hashCode());
+</span></span><span class="line"><span class="cl">    int j = (hash &gt;&gt;&gt; segmentShift) &amp; segmentMask;
+</span></span><span class="line"><span class="cl">    if ((s = (Segment&lt;K,V&gt;)UNSAFE.getObject          // nonvolatile; recheck
+</span></span><span class="line"><span class="cl">         (segments, (j &lt;&lt; SSHIFT) + SBASE)) == null) //  in ensureSegment
+</span></span><span class="line"><span class="cl">        s = ensureSegment(j);
+</span></span><span class="line"><span class="cl">    return s.put(key, hash, value, false);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>首先判空，然后计算哈希值。计算<code>put</code>进来的元素分配到哪个<code>segment</code>数组上，判断当前<code>segments</code>数组上的元素是否为空，如果分段为空就会使用<code>ensureSegment</code>方法创建<code>segment</code>对象；
+最后调用<code>Segment.put</code>方法存放到对应的节点中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Returns the segment for the given index, creating it and
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * recording in segment table (via CAS) if not already present.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @param k the index
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @return the segment
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">ensureSegment</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">k</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">ss</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">segments</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">u</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">k</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">SSHIFT</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">SBASE</span><span class="p">;</span><span class="w"> </span><span class="c1">// raw offset</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">seg</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">seg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">getObjectVolatile</span><span class="p">(</span><span class="n">ss</span><span class="p">,</span><span class="w"> </span><span class="n">u</span><span class="p">))</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">proto</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ss</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// use segment 0 as prototype</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">cap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">proto</span><span class="p">.</span><span class="na">table</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">float</span><span class="w"> </span><span class="n">lf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">proto</span><span class="p">.</span><span class="na">loadFactor</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)(</span><span class="n">cap</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">lf</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">HashEntry</span><span class="o">[</span><span class="n">cap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">seg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">getObjectVolatile</span><span class="p">(</span><span class="n">ss</span><span class="p">,</span><span class="w"> </span><span class="n">u</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// recheck</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">(</span><span class="n">lf</span><span class="p">,</span><span class="w"> </span><span class="n">threshold</span><span class="p">,</span><span class="w"> </span><span class="n">tab</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">seg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">getObjectVolatile</span><span class="p">(</span><span class="n">ss</span><span class="p">,</span><span class="w"> </span><span class="n">u</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">compareAndSwapObject</span><span class="p">(</span><span class="n">ss</span><span class="p">,</span><span class="w"> </span><span class="n">u</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">seg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">seg</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ensureSegment</code>方法作用是返回指定索引的分段对象，通过CAS判断，如果还没有分段则创建它并记录在分段表中。</p>
+<p>当多个线程同时执行该方法，同时通过<code>ensureSegment</code>方法创建<code>segment</code>对象时，只有一个线程能够创建成功。
+其中创建的新<code>segment</code>对象中的加载因子、存放位置、扩容阈值与<code>segment[0]</code>元素保持一致，这样性能更高，因为不用在计算了。</p>
+<p>为了保证线程安全，在<code>ensureSegment</code>方法中用<code>Unsafe</code>类中的一些方法做了三次判断，其中最后一次也就是该方法保证线程安全的关键，用到了CAS操作。确保只有一个线程能够成功创建分段。
+当多个线程并发执行下面的代码，先执行CAS的线程，判断<code>segment</code>数组中某个位置是空的，然后就把这个线程自己创建的<code>segment</code>数组赋值给<code>seg</code>，即<code>seg = s</code>然后<code>break</code>跳出循环。
+后执行的线程会再次判断seg是否为空，因先执行的线程已经<code>seg = s</code>不为空了，所以循环条件不成立，也就不再执行了。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">while ((seg = (Segment&lt;K，V&gt;)UNSAFE.getObjectVolatile(ss, u)) == null) {
+</span></span><span class="line"><span class="cl">    if (UNSAFE.compareAndSwapObject(ss, u, null, seg = s))
+</span></span><span class="line"><span class="cl">        break;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p><code>Segment.put</code>为了保证线程安全，执行<code>put</code>方法时需要加锁，如果未能获取锁，会执行<code>scanAndLockForPut</code>方法，确保最终能获取到锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">final V put(K key, int hash, V value, boolean onlyIfAbsent) {
+</span></span><span class="line"><span class="cl">    HashEntry&lt;K,V&gt; node = tryLock() ? null :
+</span></span><span class="line"><span class="cl">        scanAndLockForPut(key, hash, value);
+</span></span><span class="line"><span class="cl">    // ... 插入节点操作 最后释放锁
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p><code>scanAndLockForPut</code>方法的主要作用就是加锁，如果没有获取锁，就会一致遍历<code>segment</code>数组，直到遍历到最后一个元素。
+每次遍历完都会尝试获取锁，如果还是获取不到锁，就会重试，最大次数为<code>MAX_SCAN_RETRIES</code>在CPU多核下为64次，如果大于64次就会强制加锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">scanAndLockForPut</span><span class="p">(</span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">entryForHash</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">hash</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">retries</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// negative while locating node</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">tryLock</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">f</span><span class="p">;</span><span class="w"> </span><span class="c1">// to recheck first below</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">retries</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="c1">// speculatively create node</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">retries</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">key</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">key</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">retries</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">retries</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">MAX_SCAN_RETRIES</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">retries</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                 </span><span class="p">(</span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">entryForHash</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">hash</span><span class="p">))</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">first</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f</span><span class="p">;</span><span class="w"> </span><span class="c1">// re-traverse if entry changed</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">retries</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">MAX_SCAN_RETRIES</span><span class="w"> </span><span class="o">=</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Runtime</span><span class="p">.</span><span class="na">getRuntime</span><span class="p">().</span><span class="na">availableProcessors</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">64</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><h4 id="jdk18">JDK1.8</h4>
+<p>在JDK1.8中，<code>ConcurrentHashMap</code>进行了重大改进，弃用了分段锁机制，转而采用更细粒度的并发控制机制。
+直接用Node数组+链表/红黑树的数据结构来实现，并发控制使用 <code>synchronized</code> 和CAS来操作，整体看起来就像是优化过且线程安全的<code>HashMap</code>。
+虽然在JDK1.8中还能看到<code>Segment</code>的数据结构，但是已经简化了其属性，这样做只是为了兼容旧版本。</p>
+<p>JDK1.8中彻底放弃了<code>Segment</code>转而采用的是<code>Node</code>，其设计思想也不再是JDK1.7中的分段锁思想。
+<code>ConcurrentHashMap</code>在JDK1.8中不再使用分段锁，而是使用与<code>HashMap</code>类似的数组+链表/红黑树的数据结构。
+数组中的每个桶是一个链表或红黑树的头节点。<code>HashMap</code>不同的是<code>ConcurrentHashMap</code>只是增加了同步操作来控制并发。</p>
+<p><img alt="jdk1.8ConcurrentHashMap" src="/iblog/posts/annex/images/essays/jdk1.8ConcurrentHashMap.png"></p>
+<p>插入操作首先根据键的哈希值定位到具体的桶。如果该桶为空，则使用CAS操作插入新的节点。如果该桶非空，则使用<code>synchronized</code>锁定该桶，并进行链表或红黑树的插入操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">final V putVal(K key, V value, boolean onlyIfAbsent) {
+</span></span><span class="line"><span class="cl">    if (key == null || value == null)
+</span></span><span class="line"><span class="cl">        throw new NullPointerException();
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    // 计算键的哈希值，并将其扩散
+</span></span><span class="line"><span class="cl">    int hash = spread(key.hashCode());
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    // 记录桶中元素个数
+</span></span><span class="line"><span class="cl">    int binCount = 0;
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    // 循环查找或插入元素
+</span></span><span class="line"><span class="cl">    for (Node&lt;K,V&gt;[] tab = table;;) {
+</span></span><span class="line"><span class="cl">        Node&lt;K,V&gt; f;
+</span></span><span class="line"><span class="cl">        int n, i, fh;
+</span></span><span class="line"><span class="cl">        
+</span></span><span class="line"><span class="cl">        // 如果表为空或长度为0，则进行初始化
+</span></span><span class="line"><span class="cl">        if (tab == null || (n = tab.length) == 0)
+</span></span><span class="line"><span class="cl">            tab = initTable();
+</span></span><span class="line"><span class="cl">        
+</span></span><span class="line"><span class="cl">        // 计算存储位置
+</span></span><span class="line"><span class="cl">        else if ((f = tabAt(tab, i = (n - 1) &amp; hash)) == null) {
+</span></span><span class="line"><span class="cl">            // 如果位置为空，则尝试使用 CAS 插入新节点
+</span></span><span class="line"><span class="cl">            if (casTabAt(tab, i, null, new Node&lt;K,V&gt;(hash, key, value, null)))
+</span></span><span class="line"><span class="cl">                break;  // 插入成功，退出循环
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        
+</span></span><span class="line"><span class="cl">        // 如果位置非空，处理链表或红黑树结构
+</span></span><span class="line"><span class="cl">        else if ((fh = f.hash) == MOVED)
+</span></span><span class="line"><span class="cl">            tab = helpTransfer(tab, f); // 如果处于扩容状态，则帮助进行扩容
+</span></span><span class="line"><span class="cl">        
+</span></span><span class="line"><span class="cl">        else {
+</span></span><span class="line"><span class="cl">            V oldVal = null;
+</span></span><span class="line"><span class="cl">            
+</span></span><span class="line"><span class="cl">            // 使用 synchronized 锁定桶
+</span></span><span class="line"><span class="cl">            synchronized (f) {
+</span></span><span class="line"><span class="cl">                if (tabAt(tab, i) == f) {
+</span></span><span class="line"><span class="cl">                    if (fh &gt;= 0) {
+</span></span><span class="line"><span class="cl">                        // 处理链表结构
+</span></span><span class="line"><span class="cl">                        binCount = 1;
+</span></span><span class="line"><span class="cl">                        for (Node&lt;K,V&gt; e = f;; ++binCount) {
+</span></span><span class="line"><span class="cl">                            K ek;
+</span></span><span class="line"><span class="cl">                            if (e.hash == hash &amp;&amp;
+</span></span><span class="line"><span class="cl">                                ((ek = e.key) == key ||
+</span></span><span class="line"><span class="cl">                                 (ek != null &amp;&amp; key.equals(ek)))) {
+</span></span><span class="line"><span class="cl">                                oldVal = e.val;
+</span></span><span class="line"><span class="cl">                                if (!onlyIfAbsent)
+</span></span><span class="line"><span class="cl">                                    e.val = value;
+</span></span><span class="line"><span class="cl">                                break;
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">                            Node&lt;K,V&gt; pred = e;
+</span></span><span class="line"><span class="cl">                            if ((e = e.next) == null) {
+</span></span><span class="line"><span class="cl">                                pred.next = new Node&lt;K,V&gt;(hash, key, value, null);
+</span></span><span class="line"><span class="cl">                                break;
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">                        }
+</span></span><span class="line"><span class="cl">                    } else if (f instanceof TreeBin) {
+</span></span><span class="line"><span class="cl">                        // 处理红黑树结构
+</span></span><span class="line"><span class="cl">                        Node&lt;K,V&gt; p;
+</span></span><span class="line"><span class="cl">                        binCount = 2;
+</span></span><span class="line"><span class="cl">                        if ((p = ((TreeBin&lt;K,V&gt;)f).putTreeVal(hash, key, value)) != null) {
+</span></span><span class="line"><span class="cl">                            oldVal = p.val;
+</span></span><span class="line"><span class="cl">                            if (!onlyIfAbsent)
+</span></span><span class="line"><span class="cl">                                p.val = value;
+</span></span><span class="line"><span class="cl">                        }
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            
+</span></span><span class="line"><span class="cl">            // 根据操作结果进行进一步处理
+</span></span><span class="line"><span class="cl">            if (binCount != 0) {
+</span></span><span class="line"><span class="cl">                if (binCount &gt;= TREEIFY_THRESHOLD)  // 如果链表长度达到阈值，则转为红黑树
+</span></span><span class="line"><span class="cl">                    treeifyBin(tab, i);
+</span></span><span class="line"><span class="cl">                if (oldVal != null)
+</span></span><span class="line"><span class="cl">                    return oldVal;  // 返回旧值
+</span></span><span class="line"><span class="cl">                break;  // 插入完成，退出循环
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    // 更新计数器
+</span></span><span class="line"><span class="cl">    addCount(1L, binCount);
+</span></span><span class="line"><span class="cl">    return null;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>如果<code>table</code>为空或长度为0，则调用<code>initTable()</code>方法进行初始化。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">private final Node&lt;K,V&gt;[] initTable() {
+</span></span><span class="line"><span class="cl">    Node&lt;K,V&gt;[] tab; int sc;
+</span></span><span class="line"><span class="cl">    while ((tab = table) == null || tab.length == 0) {
+</span></span><span class="line"><span class="cl">        if ((sc = sizeCtl) &lt; 0)
+</span></span><span class="line"><span class="cl">            Thread.yield(); // lost initialization race; just spin
+</span></span><span class="line"><span class="cl">        else if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) {
+</span></span><span class="line"><span class="cl">            try {
+</span></span><span class="line"><span class="cl">                if ((tab = table) == null || tab.length == 0) {
+</span></span><span class="line"><span class="cl">                    int n = (sc &gt; 0) ? sc : DEFAULT_CAPACITY;
+</span></span><span class="line"><span class="cl">                    @SuppressWarnings(&#34;unchecked&#34;)
+</span></span><span class="line"><span class="cl">                    Node&lt;K,V&gt;[] nt = (Node&lt;K,V&gt;[])new Node&lt;?,?&gt;[n];
+</span></span><span class="line"><span class="cl">                    table = tab = nt;
+</span></span><span class="line"><span class="cl">                    sc = n - (n &gt;&gt;&gt; 2);
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            } finally {
+</span></span><span class="line"><span class="cl">                sizeCtl = sc;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            break;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    return tab;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>根据键的哈希值<code>hash</code>计算存储在<code>table</code>中的位置。如果该位置为空，则使用<code>casTabAt()</code>方法尝试通过CAS操作插入新的<code>Node</code>节点。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int hash = spread(key.hashCode());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// hash算法，计算存放在map中的位置；要保证尽可能的均匀分散，避免hash冲突
+</span></span><span class="line"><span class="cl">static final int HASH_BITS = 0x7fffffff;
+</span></span><span class="line"><span class="cl">static final int spread(int h) {
+</span></span><span class="line"><span class="cl">    // 等同于： key.hashCode() ^ (key.hashCode() &gt;&gt;&gt; 16) &amp; 0x7fffffff
+</span></span><span class="line"><span class="cl">    return (h ^ (h &gt;&gt;&gt; 16)) &amp; HASH_BITS;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>如果位置非空，首先判断是否处于扩容状态<code>MOVED</code>，如果是，则调用<code>helpTransfer()</code>方法协助进行扩容操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// MOVED = -1
+</span></span><span class="line"><span class="cl">if ((fh = f.hash) == MOVED)
+</span></span><span class="line"><span class="cl">tab = helpTransfer(tab, f);
+</span></span></code></pre></div><p>如果位置上是链表结构<code>(fh &gt;= 0)</code>，则遍历链表，根据键查找或插入节点。如果位置上是红黑树结构<code>(f instanceof TreeBin)</code>，则调用<code>putTreeVal()</code>方法在红黑树中插入节点。
+然后使用<code>synchronized (f)</code>锁定桶，确保在链表或红黑树操作期间其他线程不能修改桶的结构。根据链表长度<code>binCount &gt;= TREEIFY_THRESHOLD(默认是8)</code>，则把链表转化为红黑树结构的情况，如果插入操作修改了已有节点的值，则返回旧值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">V oldVal = null;
+</span></span><span class="line"><span class="cl">synchronized (f) {
+</span></span><span class="line"><span class="cl">    if (tabAt(tab, i) == f) {
+</span></span><span class="line"><span class="cl">        if (fh &gt;= 0) {
+</span></span><span class="line"><span class="cl">            binCount = 1;
+</span></span><span class="line"><span class="cl">            for (Node&lt;K,V&gt; e = f;; ++binCount) {
+</span></span><span class="line"><span class="cl">                K ek;
+</span></span><span class="line"><span class="cl">                if (e.hash == hash &amp;&amp;
+</span></span><span class="line"><span class="cl">                    ((ek = e.key) == key ||
+</span></span><span class="line"><span class="cl">                     (ek != null &amp;&amp; key.equals(ek)))) {
+</span></span><span class="line"><span class="cl">                    oldVal = e.val;
+</span></span><span class="line"><span class="cl">                    if (!onlyIfAbsent)
+</span></span><span class="line"><span class="cl">                        e.val = value;
+</span></span><span class="line"><span class="cl">                    break;
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">                Node&lt;K,V&gt; pred = e;
+</span></span><span class="line"><span class="cl">                if ((e = e.next) == null) {
+</span></span><span class="line"><span class="cl">                    pred.next = new Node&lt;K,V&gt;(hash, key,
+</span></span><span class="line"><span class="cl">                                              value, null);
+</span></span><span class="line"><span class="cl">                    break;
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        else if (f instanceof TreeBin) {
+</span></span><span class="line"><span class="cl">            Node&lt;K,V&gt; p;
+</span></span><span class="line"><span class="cl">            binCount = 2;
+</span></span><span class="line"><span class="cl">            if ((p = ((TreeBin&lt;K,V&gt;)f).putTreeVal(hash, key,
+</span></span><span class="line"><span class="cl">                                           value)) != null) {
+</span></span><span class="line"><span class="cl">                oldVal = p.val;
+</span></span><span class="line"><span class="cl">                if (!onlyIfAbsent)
+</span></span><span class="line"><span class="cl">                    p.val = value;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">if (binCount != 0) {
+</span></span><span class="line"><span class="cl">    if (binCount &gt;= TREEIFY_THRESHOLD)
+</span></span><span class="line"><span class="cl">        treeifyBin(tab, i);
+</span></span><span class="line"><span class="cl">    if (oldVal != null)
+</span></span><span class="line"><span class="cl">        return oldVal;
+</span></span><span class="line"><span class="cl">    break;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>最后调用<code>addCount()</code>方法更新元素计数器，表示成功插入了一个节点。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 相当于size++
+</span></span><span class="line"><span class="cl">addCount(1L, binCount);
+</span></span></code></pre></div><p>其中<code>addCount()</code>方法中也包含了扩容操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addCount</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">x</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">check</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">CounterCell</span><span class="o">[]</span><span class="w"> </span><span class="n">as</span><span class="p">;</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">b</span><span class="p">,</span><span class="w"> </span><span class="n">s</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">as</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">counterCells</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="o">!</span><span class="n">U</span><span class="p">.</span><span class="na">compareAndSwapLong</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">BASECOUNT</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">baseCount</span><span class="p">,</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">x</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CounterCell</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">v</span><span class="p">;</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">m</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">uncontended</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">as</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">m</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">as</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">(</span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">as</span><span class="o">[</span><span class="n">ThreadLocalRandom</span><span class="p">.</span><span class="na">getProbe</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">m</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">!</span><span class="p">(</span><span class="n">uncontended</span><span class="w"> </span><span class="o">=</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="n">U</span><span class="p">.</span><span class="na">compareAndSwapLong</span><span class="p">(</span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">CELLVALUE</span><span class="p">,</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="na">value</span><span class="p">,</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">x</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">fullAddCount</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="w"> </span><span class="n">uncontended</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">check</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sumCount</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">check</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="n">nt</span><span class="p">;</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">sc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="p">(</span><span class="kt">long</span><span class="p">)(</span><span class="n">sc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sizeCtl</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">tab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">resizeStamp</span><span class="p">(</span><span class="n">n</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">sc</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">sc</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">RESIZE_STAMP_SHIFT</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">sc</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">sc</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">MAX_RESIZERS</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">nt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nextTable</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">transferIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">U</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">SIZECTL</span><span class="p">,</span><span class="w"> </span><span class="n">sc</span><span class="p">,</span><span class="w"> </span><span class="n">sc</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">transfer</span><span class="p">(</span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="n">nt</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">U</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">SIZECTL</span><span class="p">,</span><span class="w"> </span><span class="n">sc</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                         </span><span class="p">(</span><span class="n">rs</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">RESIZE_STAMP_SHIFT</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">transfer</span><span class="p">(</span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sumCount</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>节点从<code>table</code>移动到<code>nextTable</code>，大体思想是遍历、复制的过程。
+通过<code>Unsafe.compareAndSwapInt</code>修改<code>sizeCtl</code>值，保证只有一个线程能够初始化<code>nextTable</code>，扩容后的数组长度为原来的两倍，但是容量是原来的1.5。</p>
+<h2 id="参考文章">参考文章</h2>
+<ul>
+<li><a href="http://www.threadlocal.cn">http://www.threadlocal.cn</a></li>
+<li><a href="https://blog.csdn.net/lufeng20/article/details/24314381">https://blog.csdn.net/lufeng20/article/details/24314381</a></li>
+<li><a href="https://blog.csdn.net/qq_35190492/article/details/116431270">https://blog.csdn.net/qq_35190492/article/details/116431270</a></li>
+<li><a href="https://www.cnblogs.com/dolphin0520/p/3920407.html">https://www.cnblogs.com/dolphin0520/p/3920407.html</a></li>
+<li><a href="https://www.jianshu.com/p/c0642afe03e0">https://www.jianshu.com/p/c0642afe03e0</a></li>
+<li><a href="https://www.cnblogs.com/edisonchou/p/5061886.html">https://www.cnblogs.com/edisonchou/p/5061886.html</a></li>
+<li><a href="https://zhuanlan.zhihu.com/p/361475700">https://zhuanlan.zhihu.com/p/361475700</a></li>
+<li><a href="http://www.cs.umd.edu/~pugh/java/memoryModel/jsr133.pdf">http://www.cs.umd.edu/~pugh/java/memoryModel/jsr133.pdf</a></li>
+<li><a href="https://www.cnblogs.com/myseries/p/10784076.html">https://www.cnblogs.com/myseries/p/10784076.html</a></li>
+<li><a href="http://www.blogjava.net/zhanglongsr/articles/356782.html">http://www.blogjava.net/zhanglongsr/articles/356782.html</a></li>
+<li><a href="https://zhuanlan.zhihu.com/p/290991898">https://zhuanlan.zhihu.com/p/290991898</a></li>
+<li><a href="https://blog.csdn.net/choukekai/article/details/63688332">https://blog.csdn.net/choukekai/article/details/63688332</a></li>
+<li><a href="https://blog.csdn.net/zqz_zqz/article/details/70233767">https://blog.csdn.net/zqz_zqz/article/details/70233767</a></li>
+<li><a href="https://tech.meituan.com/2018/11/15/java-lock.html">https://tech.meituan.com/2018/11/15/java-lock.html</a></li>
+<li><a href="https://www.cnblogs.com/aspirant/p/11470858.html">https://www.cnblogs.com/aspirant/p/11470858.html</a></li>
+<li><a href="https://www.bilibili.com/video/BV1xt411S7xy?p=159">https://www.bilibili.com/video/BV1xt411S7xy?p=159</a></li>
+<li><a href="https://developer.51cto.com/art/202104/656540.htm">https://developer.51cto.com/art/202104/656540.htm</a></li>
+<li><a href="https://blog.csdn.net/qq_38293564/article/details/80558157">https://blog.csdn.net/qq_38293564/article/details/80558157</a></li>
+<li><a href="https://zhuanlan.zhihu.com/p/98593407">https://zhuanlan.zhihu.com/p/98593407</a></li>
+<li><a href="https://blog.csdn.net/zbc1090549839/article/details/53389602">https://blog.csdn.net/zbc1090549839/article/details/53389602</a></li>
+<li><a href="https://www.hollischuang.com/archives/2030">https://www.hollischuang.com/archives/2030</a></li>
+<li><a href="https://blog.csdn.net/javazejian/article/details/72828483">https://blog.csdn.net/javazejian/article/details/72828483</a></li>
+<li><a href="https://blog.csdn.net/luoweifu/article/details/46613015">https://blog.csdn.net/luoweifu/article/details/46613015</a></li>
+<li><a href="https://www.artima.com/insidejvm/ed2/threadsynch.html">https://www.artima.com/insidejvm/ed2/threadsynch.html</a></li>
+<li><a href="https://xie.infoq.cn/article/d3afa3e6f9a70155106627ce5">https://xie.infoq.cn/article/d3afa3e6f9a70155106627ce5</a></li>
+<li><a href="http://hollischuang.gitee.io/tobetopjavaer/#/basics/concurrent-coding/synchronized">http://hollischuang.gitee.io/tobetopjavaer/#/basics/concurrent-coding/synchronized</a></li>
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diff --git a/blog-site/public/posts/javabasics/rookie-object-oriented/index.html b/blog-site/public/posts/javabasics/rookie-object-oriented/index.html
new file mode 100644
index 00000000..7e4e920f
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@@ -0,0 +1,6550 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
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+    <meta name="viewport" content="width=device-width, initial-scale=1" />
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+    
+    
+    <meta name="description" content="概览 面向对象简称OO(object-oriented)是相对面向过程(procedure-oriented)来说的，是一种编程思想，Java就是一门面向对象的语" />
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+    <div class="post-password">
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+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%a7%88">
+                    概览
+                </a>
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+            
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+        
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+        
+        
+        
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+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bd%af%e4%bb%b6%e8%ae%be%e8%ae%a1%e5%8e%9f%e5%88%99">
+                    软件设计原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8d%95%e4%b8%80%e8%81%8c%e8%b4%a3%e5%8e%9f%e5%88%99">
+                    单一职责原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%80%e6%94%be%e5%b0%81%e9%97%ad%e5%8e%9f%e5%88%99">
+                    开放封闭原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%be%9d%e8%b5%96%e5%80%92%e7%bd%ae%e5%8e%9f%e5%88%99">
+                    依赖倒置原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%a5%e5%8f%a3%e9%9a%94%e7%a6%bb%e5%8e%9f%e5%88%99">
+                    接口隔离原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8c%e6%b0%8f%e6%9b%bf%e6%8d%a2%e5%8e%9f%e5%88%99">
+                    里氏替换原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%90%88%e6%88%90%e5%a4%8d%e7%94%a8%e5%8e%9f%e5%88%99">
+                    合成复用原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%aa%e7%b1%b3%e7%89%b9%e6%b3%95%e5%88%99">
+                    迪米特法则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9d%a2%e5%90%91%e5%af%b9%e8%b1%a1%e4%b8%89%e5%a4%a7%e7%89%b9%e6%80%a7">
+                    面向对象三大特性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b0%81%e8%a3%85">
+                    封装
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%a7%e6%89%bf">
+                    继承
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%a7%e6%89%bf%e4%b8%8e%e7%bb%84%e5%90%88">
+                    继承与组合
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8a%bd%e8%b1%a1%e7%b1%bb%e4%b8%8e%e6%8e%a5%e5%8f%a3">
+                    抽象类与接口
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%9a%e6%80%81">
+                    多态
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8d%e5%86%99%e4%b8%8e%e9%87%8d%e8%bd%bd">
+                    重写与重载
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%ae%be%e8%ae%a1%e6%a8%a1%e5%bc%8f">
+                    设计模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8d%95%e4%be%8b%e6%a8%a1%e5%bc%8f">
+                    单例模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%a5%bf%e6%b1%89%e5%bc%8f">
+                    饿汉式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e4%b8%8d%e5%ae%89%e5%85%a8%e7%9a%84%e6%87%92%e6%b1%89%e5%bc%8f">
+                    线程不安全的懒汉式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8%e7%9a%84%e6%87%92%e6%b1%89%e5%bc%8f">
+                    线程安全的懒汉式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8c%e9%87%8d%e6%a0%a1%e9%aa%8c%e9%94%81">
+                    双重校验锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9d%99%e6%80%81%e5%86%85%e9%83%a8%e7%b1%bb%e5%bc%8f">
+                    静态内部类式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9e%9a%e4%b8%be%e5%bc%8f">
+                    枚举式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8d%95%e4%be%8b%e4%b8%8e%e5%ba%8f%e5%88%97%e5%8c%96">
+                    单例与序列化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b7%a5%e5%8e%82%e6%a8%a1%e5%bc%8f">
+                    工厂模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ae%80%e5%8d%95%e5%b7%a5%e5%8e%82%e6%a8%a1%e5%bc%8f">
+                    简单工厂模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b7%a5%e5%8e%82%e6%96%b9%e6%b3%95%e6%a8%a1%e5%bc%8f">
+                    工厂方法模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8a%bd%e8%b1%a1%e5%b7%a5%e5%8e%82%e6%a8%a1%e5%bc%8f">
+                    抽象工厂模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8e%9f%e5%9e%8b%e6%a8%a1%e5%bc%8f">
+                    原型模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b5%85%e5%85%8b%e9%9a%86">
+                    浅克隆
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b7%b1%e5%85%8b%e9%9a%86">
+                    深克隆
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%bb%e7%bb%93">
+                    总结
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bb%ba%e9%80%a0%e8%80%85%e6%a8%a1%e5%bc%8f">
+                    建造者模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%82%e9%85%8d%e5%99%a8%e6%a8%a1%e5%bc%8f">
+                    适配器模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e8%b1%a1%e9%80%82%e9%85%8d%e5%99%a8">
+                    对象适配器
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b1%bb%e9%80%82%e9%85%8d%e5%99%a8">
+                    类适配器
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%bb%e7%bb%93-1">
+                    总结
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a1%a5%e6%8e%a5%e6%a8%a1%e5%bc%8f">
+                    桥接模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%84%e5%90%88%e6%a8%a1%e5%bc%8f">
+                    组合模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a3%85%e9%a5%b0%e6%a8%a1%e5%bc%8f">
+                    装饰模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%96%e8%a7%82%e6%a8%a1%e5%bc%8f">
+                    外观模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%ab%e5%85%83%e6%a8%a1%e5%bc%8f">
+                    享元模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%a3%e7%90%86%e6%a8%a1%e5%bc%8f">
+                    代理模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9d%99%e6%80%81%e4%bb%a3%e7%90%86">
+                    静态代理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jdk%e5%8a%a8%e6%80%81%e4%bb%a3%e7%90%86">
+                    JDK动态代理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cglib%e5%8a%a8%e6%80%81%e4%bb%a3%e7%90%86">
+                    Cglib动态代理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%bb%e7%bb%93-2">
+                    总结
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%81%8c%e8%b4%a3%e9%93%be%e6%a8%a1%e5%bc%8f">
+                    职责链模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%91%bd%e4%bb%a4%e6%a8%a1%e5%bc%8f">
+                    命令模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e9%87%8a%e5%99%a8%e6%a8%a1%e5%bc%8f">
+                    解释器模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%ad%e4%bb%a3%e5%99%a8%e6%a8%a1%e5%bc%8f">
+                    迭代器模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ad%e4%bb%8b%e8%80%85%e6%a8%a1%e5%bc%8f">
+                    中介者模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%87%e5%bf%98%e5%bd%95%e6%a8%a1%e5%bc%8f">
+                    备忘录模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%82%e5%af%9f%e8%80%85%e6%a8%a1%e5%bc%8f">
+                    观察者模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%8a%b6%e6%80%81%e6%a8%a1%e5%bc%8f">
+                    状态模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ad%96%e7%95%a5%e6%a8%a1%e5%bc%8f">
+                    策略模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a8%a1%e6%9d%bf%e6%96%b9%e6%b3%95%e6%a8%a1%e5%bc%8f">
+                    模板方法模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%ae%bf%e9%97%ae%e8%80%85%e6%a8%a1%e5%bc%8f">
+                    访问者模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
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+                        <h2 id="post_single_title">Java面向对象</h2>
+                        <span id="post_page_title_date" class="date">2021.02.15</span>
+                        
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+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>面向对象简称OO(<code>object-oriented</code>)是相对面向过程(<code>procedure-oriented</code>)来说的，是一种编程思想，Java就是一门面向对象的语言，包括三大特性和六大原则。
+其中，三大特性指的是封装、继承和多态。六大原则指的是单一职责原则、开放封闭原则、迪米特原则、里氏替换原则、依赖倒置原则以及接口隔离原则。
+单一职责原则是指一个类应该是一组相关性很高的函数和数据的封装，这是为了提高程序的内聚性，而其他五个原则是通过抽象来实现的，目的是为了降低程序的耦合性以及提高可扩展性。</p>
+<p>面向对象编程简称OOP(<code>Object-oriented programming</code>)，是将事务高度抽象化的编程模式。
+面向对象编程是以功能来划分问题的，将问题分解成一个一个步骤，对每个步骤进行相应的抽象，形成对应对象，通过不同对象之间的调用，组合成某个功能解决问题。</p>
+<p>面向对象是对比面向过程来说的，面向过程编程简称POP(<code>Procedural oriented programming</code>)。
+面向过程编程是一种以过程为中心的编程方式，主要通过一系列步骤来处理数据。程序通过调用函数一步步完成任务，每个函数都执行特定的操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 面向过程编程示例：计算矩形面积</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ProceduralExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 定义计算面积的函数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calculateArea</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">width</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">height</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">width</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">width</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">height</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">area</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">calculateArea</span><span class="p">(</span><span class="n">width</span><span class="p">,</span><span class="w"> </span><span class="n">height</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;矩形的面积是: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">area</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>面向对象编程是一种以对象为中心的编程方式，将数据和操作封装在一起，通过对象的交互来完成程序的功能。对象是类的实例，类定义了对象的属性和方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 面向对象编程示例：计算矩形面积</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 定义矩形类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Rectangle</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构造函数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Rectangle</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">width</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">height</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">width</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">height</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算面积的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calculateArea</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">width</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ObjectOrientedExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建矩形对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Rectangle</span><span class="w"> </span><span class="n">rectangle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Rectangle</span><span class="p">(</span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 调用对象的方法计算面积</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">area</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rectangle</span><span class="p">.</span><span class="na">calculateArea</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;矩形的面积是: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">area</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>通过例子可以看出面向对象更重视不重复造轮子，即创建一次重复使用。
+简而言之，用面向过程的方法写出来的程序是一份蛋炒饭，而用面向对象写出来的程序是一份盖浇饭，就是在一碗白米饭上面浇上一份盖菜，你喜欢什么菜，你就浇上什么菜。</p>
+<p>面向对象是模型化的，你只需抽象出几个类，进行封装成各个功能，通过不同对象之间的调用来解决问题，而面向过程需要把问题分解为几个步骤，每个步骤用对应的函数调用即可。
+面向过程是具体化的、流程化的，解决一个问题需要你一步一步的分析，一步一步的实现。
+面向对象的底层其实还是面向过程，把面向过程抽象成类，然后进行封装，方便我们我们使用就是面向对象了。</p>
+<p>抽象会使复杂的问题更加简单化，面向对象更符合人类的思维，而面向过程则是机器的思想。
+选择哪种编程范式取决于具体的应用场景和开发需求。对于复杂系统的开发，面向对象更有优势，因为它可以更好地组织和管理代码；而对于一些简单的任务，面向过程可能更加直观和高效。</p>
+<h2 id="软件设计原则">软件设计原则</h2>
+<p>软件设计原则是指导软件开发过程中设计和构建软件系统的一组规则。
+这些规则的目的是为了让程序达到高内聚、低耦合以及提高扩展性，其实现手段是面向对象的三大特性：封装、继承以及多态。</p>
+<table>
+<thead>
+<tr>
+<th>设计原则名称</th>
+<th>核心思想</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>单一职责原则</td>
+<td>一个类只负责一个特定的职责</td>
+</tr>
+<tr>
+<td>开放封闭原则</td>
+<td>软件实体应该可以扩展，但不应该修改其已有代码</td>
+</tr>
+<tr>
+<td>依赖倒转原则</td>
+<td>高层模块不应该依赖低层模块，两者都应该依赖抽象；抽象不应该依赖细节，细节应该依赖抽象</td>
+</tr>
+<tr>
+<td>里氏替换原则</td>
+<td>任何基类可以出现的地方，子类也可以出现</td>
+</tr>
+<tr>
+<td>接口隔离原则</td>
+<td>使用多个专门的接口，而不是一个通用的接口</td>
+</tr>
+<tr>
+<td>合成复用原则</td>
+<td>优先使用组合而不是继承来实现代码复用</td>
+</tr>
+<tr>
+<td>迪米特法则</td>
+<td>一个对象应尽量少地了解其他对象，从而降低耦合度</td>
+</tr>
+</tbody>
+</table>
+<h3 id="单一职责原则">单一职责原则</h3>
+<p>其核心思想为，一个类最好只做一件事。单一职责原则可降低类的复杂度，提高代码可读性、可维护性、降低变更风险。
+单一职责原则可以看做是低耦合、高内聚在面向对象原则上的引申，将职责定义为引起变化的原因，以提高内聚性来减少引起变化的原因。
+职责过多，可能引起它变化的原因就越多，这将导致职责依赖，相互之间就产生影响，从而大大损伤其内聚性和耦合度。
+通常意义下的单一职责，就是指只有一种单一功能，不要为类实现过多的功能点，以保证实体只有一个引起它变化的原因。
+专注，是一个人优良的品质；同样的，单一也是一个类的优良设计。交杂不清的职责将使得代码看起来特别别扭牵一发而动全身，有失美感和必然导致丑陋的系统错误风险。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Vehicle</span><span class="w"> </span><span class="n">vehicle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Vehicle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vehicle</span><span class="p">.</span><span class="na">running</span><span class="p">(</span><span class="s">&#34;汽车&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 飞机不是在路上行驶</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vehicle</span><span class="p">.</span><span class="na">running</span><span class="p">(</span><span class="s">&#34;飞机&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 在run方法中违反了单一职责原则
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 解决方法根据不同的交通工具,分解成不同的类即可
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Vehicle</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">running</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在路上行驶 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 解决</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Driving</span><span class="w"> </span><span class="n">driving</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Driving</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">driving</span><span class="p">.</span><span class="na">running</span><span class="p">(</span><span class="s">&#34;汽车&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Flight</span><span class="w"> </span><span class="n">flight</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Flight</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flight</span><span class="p">.</span><span class="na">running</span><span class="p">(</span><span class="s">&#34;飞机&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Driving</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">running</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在路上行驶 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Flight</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">running</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在空中飞行 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>只要类中方法数量足够少，可以在方法级别保持单一职责原则。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Vehicle2</span><span class="w"> </span><span class="n">vehicle2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Vehicle2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vehicle2</span><span class="p">.</span><span class="na">driving</span><span class="p">(</span><span class="s">&#34;汽车&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vehicle2</span><span class="p">.</span><span class="na">flight</span><span class="p">(</span><span class="s">&#34;飞机&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/*
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 改进
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Vehicle2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">driving</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在路上行驶 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">flight</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在空中飞行 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="开放封闭原则">开放封闭原则</h3>
+<p>软件实体应该是可扩展的，而不可修改的。也就是对提供方扩展开放，对使用方修改封闭的。开放封闭原则主要体现在两个方面：</p>
+<ul>
+<li>对扩展开放，意味着有新的需求或变化时，可以对现有代码进行扩展，以适应新的情况。</li>
+<li>对修改封闭，意味着类一旦设计完成，就可以独立完成其工作，而不要对其进行任何尝试的修改。</li>
+</ul>
+<p>实现开放封闭原则的核心思想是对抽象编程，而不对具体编程。
+因为抽象相对稳定，让类依赖于固定的抽象，所以修改就是封闭的；而通过面向对象的继承和多态机制，又可以实现对抽象类的继承，通过覆写其方法来改变固有行为，实现新的拓展方法，所以就是开放的。
+需求总是变化，当我们给程序添加或者修改功能时，需要用开放封闭原则来封闭变化满足需求，同时还能保持软件内部的封装体系稳定，不被需求的变化影响。
+编程中遵循其他原则，以及使用其他设计模式的目的就是为了遵循开闭原则。</p>
+<p>当软件需要变化时，尽量使用扩展的软件实体的方式行为来实现变化，而不是通过修改已有的代码来实现变化。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Mother</span><span class="w"> </span><span class="n">mother</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Mother</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Son</span><span class="w"> </span><span class="n">son</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Son</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Daughter</span><span class="w"> </span><span class="n">daughter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Daughter</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 注入子类对象 如果扩展需要其他类 换成其他对象即可</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mother</span><span class="p">.</span><span class="na">setAbstractFather</span><span class="p">(</span><span class="n">son</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mother</span><span class="p">.</span><span class="na">display</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractFather</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Son</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractFather</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;son class ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Daughter</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractFather</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;daughter class ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Mother</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractFather</span><span class="w"> </span><span class="n">abstractFather</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAbstractFather</span><span class="p">(</span><span class="n">AbstractFather</span><span class="w"> </span><span class="n">abstractFather</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">abstractFather</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">abstractFather</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractFather</span><span class="p">.</span><span class="na">display</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="依赖倒置原则">依赖倒置原则</h3>
+<p>该原则依赖于抽象，具体而言就是高层模块不依赖于底层模块，二者都同依赖于抽象，抽象不依赖于具体，具体依赖于抽象。
+我们知道，依赖一定会存在于类与类、模块与模块之间。当两个模块之间存在紧密的耦合关系时，最好的方法就是分离接口和实现，即在依赖之间定义一个抽象的接口使得高层模块调用接口，而底层模块实现接口的定义，以此来有效控制耦合关系，达到依赖于抽象的设计目标。
+抽象的稳定性决定了系统的稳定性，因为抽象是不变的，依赖于抽象是面向对象设计的精髓，也是依赖倒置原则的核心。
+依赖于抽象是一个通用的原则，而某些时候依赖于细节则是在所难免的，必须权衡在抽象和具体之间的取舍。</p>
+<p>依赖于抽象，就是对接口编程，不要对实现编程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 定义一个接口，表示消息发送者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">MessageSender</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实现接口的EmailSender类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">EmailSender</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">MessageSender</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Sending email with message: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实现接口的SmsSender类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SmsSender</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">MessageSender</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Sending SMS with message: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 高层模块的MessageService类依赖于MessageSender接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">MessageService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">MessageSender</span><span class="w"> </span><span class="n">sender</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 通过构造函数注入依赖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MessageService</span><span class="p">(</span><span class="n">MessageSender</span><span class="w"> </span><span class="n">sender</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">sender</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sender</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">processMessage</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用MessageSender接口发送消息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sender</span><span class="p">.</span><span class="na">sendMessage</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用EmailSender发送消息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MessageSender</span><span class="w"> </span><span class="n">emailSender</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EmailSender</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MessageService</span><span class="w"> </span><span class="n">emailService</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MessageService</span><span class="p">(</span><span class="n">emailSender</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">emailService</span><span class="p">.</span><span class="na">processMessage</span><span class="p">(</span><span class="s">&#34;Hello via Email!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用SmsSender发送消息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MessageSender</span><span class="w"> </span><span class="n">smsSender</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SmsSender</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MessageService</span><span class="w"> </span><span class="n">smsService</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MessageService</span><span class="p">(</span><span class="n">smsSender</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">smsService</span><span class="p">.</span><span class="na">processMessage</span><span class="p">(</span><span class="s">&#34;Hello via SMS!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="接口隔离原则">接口隔离原则</h3>
+<p>使用多个小的专门的接口，而不要使用一个大的总接口。具体而言，接口隔离原则体现在，接口应该是内聚的，应该避免“胖”接口。
+一个类对另外一个类的依赖应该建立在最小的接口上，不要强迫依赖不用的方法，这是一种接口污染。
+接口有效地将细节和抽象隔离，体现了对抽象编程的一切好处，接口隔离强调接口的单一性，而胖接口存在明显的弊端，会导致实现的类型必须完全实现接口的所有方法、属性等。
+某些时候，实现类并非需要所有的接口定义，在设计上这是“浪费”，而且在实施上这会带来潜在的问题，对胖接口的修改将导致一连串的客户端程序需要修改，有时候这是一种灾难。
+在这种情况下，应该将胖接口<strong>分离</strong>为多个特点的定制化方法，使得客户端仅仅依赖于它们的实际调用的方法，从而解除了客户端不会依赖于它们不用的方法。</p>
+<p>分离的手段主要有以下两种：</p>
+<ul>
+<li>委托分离，通过增加一个新的类型来委托客户的请求，隔离客户和接口的直接依赖，但是会增加系统的开销。</li>
+<li>多重继承分离，通过接口多继承来实现客户的需求，这种方式是较好的。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FuncImpl</span><span class="w"> </span><span class="n">func</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FuncImpl</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">func</span><span class="p">.</span><span class="na">func1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">func</span><span class="p">.</span><span class="na">func2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">func</span><span class="p">.</span><span class="na">func3</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Function1</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果将接口中的方法都写在一个接口就会造成实现该接口就要重写该接口所有方法。</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 当然Java 8 接口可以有实现，降低了维护成本，解了决该问题；</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 但是我们还是应当遵循该原则，使得接口看起来更加清晰</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// void func2();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// void func3();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Function2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">func2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Function3</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">func3</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">FuncImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Function1</span><span class="p">,</span><span class="n">Function2</span><span class="p">,</span><span class="n">Function3</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am function1 impl&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func2</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am function2 impl&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func3</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am function3 impl&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="里氏替换原则">里氏替换原则</h3>
+<p>里氏替换原则这一思想体现为对继承机制的约束规范，只有子类能够替换基类时，才能保证系统在运行期内识别子类，这是保证继承复用的基础。
+在父类和子类的具体行为中，必须严格把握继承层次中的关系和特征，将基类替换为子类，程序的行为不会发生任何变化。
+同时这一约束反过来则是不成立的，子类可以替换基类，但是基类不一定能替换子类。
+里氏替换原则，主要着眼于对抽象和多态建立在继承的基础上，因此只有遵循了里氏替换原则，才能保证继承复用是可靠地。</p>
+<p>实现的方法是面向接口编程，即将公共部分抽象为基类接口或抽象类，在子类中通过覆写父类的方法实现新的方式支持同样的职责。
+里氏替换原则是关于继承机制的设计原则，违反了里氏替换原则就必然导致违反开放封闭原则。
+里氏替换原则能够保证系统具有良好的拓展性，同时实现基于多态的抽象机制，能够减少代码冗余，避免运行期的类型判别。</p>
+<p>简单来说就是子类可以扩展父类的功能，而不应该改变父类原有的功能。
+如果通过重写父类方法来完成新的功能，这样写起来虽然简单，但整个体系的可复用性会非常差，特别是运用多态比较频繁时，程序运行出错的概率会非常大。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Rectangle</span><span class="w"> </span><span class="n">rectangle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Rectangle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">rectangle</span><span class="p">.</span><span class="na">setWidth</span><span class="p">(</span><span class="n">20</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">rectangle</span><span class="p">.</span><span class="na">setHeight</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">(</span><span class="n">rectangle</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">print</span><span class="p">(</span><span class="n">rectangle</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=======================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Rectangle</span><span class="w"> </span><span class="n">square</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Square</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">square</span><span class="p">.</span><span class="na">setWidth</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 因为 Square类 重写了父类 setWidth setHeight 方法，会导致 while 循环变成一个无限循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">(</span><span class="n">square</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">print</span><span class="p">(</span><span class="n">square</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">resize</span><span class="p">(</span><span class="n">Rectangle</span><span class="w"> </span><span class="n">rectangle</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">rectangle</span><span class="p">.</span><span class="na">getWidth</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">rectangle</span><span class="p">.</span><span class="na">getHeight</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">rectangle</span><span class="p">.</span><span class="na">setHeight</span><span class="p">(</span><span class="n">rectangle</span><span class="p">.</span><span class="na">getHeight</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">print</span><span class="p">(</span><span class="n">Rectangle</span><span class="w"> </span><span class="n">rectangle</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">rectangle</span><span class="p">.</span><span class="na">getWidth</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">rectangle</span><span class="p">.</span><span class="na">getHeight</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 正方形</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Square</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Rectangle</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setWidth</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">width</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setWidth</span><span class="p">(</span><span class="n">width</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setHeight</span><span class="p">(</span><span class="n">width</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHeight</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">height</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setWidth</span><span class="p">(</span><span class="n">height</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setHeight</span><span class="p">(</span><span class="n">height</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 长方形</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Rectangle</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setWidth</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">width</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">width</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHeight</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">height</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">height</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getWidth</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getHeight</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="合成复用原则">合成复用原则</h3>
+<p>在面向对象设计中，可以通过两种方法在不同的环境中复用已有的设计和实现，即通过组合/聚合关系或通过继承。
+首先应该考虑使用组合/聚合，因为组合/聚合可以使系统更加灵活，降低类与类之间的耦合度，一个类的变化对其他类造成的影响相对较少；
+其次才考虑继承，在使用继承时，需要严格遵循里氏代换原则，有效使用继承会有助于对问题的理解，降低复杂度，而滥用继承反而会增加系统构建和维护的难度以及系统的复杂度，因此需要慎重使用继承复用。</p>
+<p>尽量使用对象组合，而不是继承来达到复用的目的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 引擎接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Engine</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 电动引擎</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ElectricEngine</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Engine</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">start</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Electric engine starts...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 燃油引擎</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">GasEngine</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Engine</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">start</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Gas engine starts...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 汽车类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Car</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Engine</span><span class="w"> </span><span class="n">engine</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Car</span><span class="p">(</span><span class="n">Engine</span><span class="w"> </span><span class="n">engine</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">engine</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">engine</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">start</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">engine</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Car starts...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个电动引擎汽车</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Engine</span><span class="w"> </span><span class="n">electricEngine</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElectricEngine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Car</span><span class="w"> </span><span class="n">electricCar</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Car</span><span class="p">(</span><span class="n">electricEngine</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">electricCar</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=======================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个燃油引擎汽车</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Engine</span><span class="w"> </span><span class="n">gasEngine</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">GasEngine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Car</span><span class="w"> </span><span class="n">gasCar</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Car</span><span class="p">(</span><span class="n">gasEngine</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">gasCar</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="迪米特法则">迪米特法则</h3>
+<p>迪米特法则又叫最少知识原则，就是说一个对象应当对其他对象有尽可能少的了解。其核心思想为，降低类之间的耦合。
+如果类与类之间的关系越密切，耦合度越大，当一个类发生改变时，对另一个类的影响也越大，所以一个对象应该对其他对象有最少的了解。
+通俗地讲，一个类应该对自己需要耦合或调用的类知道得最少，被耦合或调用的类的内部是如何复杂都和我没关系，那是你的事情，我就知道你提供的<code>public</code>方法，我就调用这么多，其他的一概不关心。
+迪米特法则其根本思想，是强调了类之间的松耦合。类之间的耦合越弱，越有利于复用，一个处在弱耦合的类被修改，不会对有关系的类造成搏击，也就是说，信息的隐藏促进了软件的复用。</p>
+<p>迪米特法则还有个更简单的定义，只与直接的<strong>朋友</strong>交谈，不跟“陌生人”说话。</p>
+<blockquote>
+<p>朋友定义：每个对象都会与其他对象有耦合关系，只要两个对象之间有耦合关系，我们就说这两个对象之间是朋友关系。<br>
+耦合的方式很多：依赖、关联、组合、聚合等。其中，我们称出现成员变量、方法参数、方法返回值中的类为直接的朋友，而出现在局部变量中的类不是直接的朋友。也就是说，陌生的类最好不要以局部变量的形式出现在类的内部。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 学生类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Student</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Class</span><span class="w"> </span><span class="n">myClass</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Student</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="w"> </span><span class="n">myClass</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">myClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myClass</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查询自己的班级信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">queryClassInfo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">className</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myClass</span><span class="p">.</span><span class="na">getClassName</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; is in class &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">className</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 班级类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Class</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">className</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Class</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">className</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">className</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">className</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getClassName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">className</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 老师类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Teacher</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Teacher</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 不符合迪米特法则的方法示例，直接返回班级名</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// public String getStudentClass(Student student) {</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//     return student.myClass.getClassName();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// }</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 通过学生对象调用公共方法获取班级信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getStudentClass</span><span class="p">(</span><span class="n">Student</span><span class="w"> </span><span class="n">student</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">student</span><span class="p">.</span><span class="na">queryClassInfo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建班级</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Class</span><span class="w"> </span><span class="n">class1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Class</span><span class="p">(</span><span class="s">&#34;Class 1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建学生并设置班级</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Student</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Student</span><span class="p">(</span><span class="s">&#34;Alice&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">class1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 学生查询自己的班级信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">student</span><span class="p">.</span><span class="na">queryClassInfo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=======================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建老师并查询学生的班级信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Teacher</span><span class="w"> </span><span class="n">teacher</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Teacher</span><span class="p">(</span><span class="s">&#34;Mr. Smith&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">studentClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">teacher</span><span class="p">.</span><span class="na">getStudentClass</span><span class="p">(</span><span class="n">student</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">student</span><span class="p">.</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; is in class &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">studentClass</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="面向对象三大特性">面向对象三大特性</h2>
+<p>面向对象编程具有三大基本特性，它们是：封装、继承、多态。这些特性是面向对象编程语言如Java、Python等的基础。
+面向对象编程的三大特性共同作用，使得程序设计更加灵活、可扩展和易于维护。
+封装提供了数据的安全性和访问控制，继承实现了代码的重用和层次化设计，多态增加了代码的适应性和灵活性。这些特性共同构成了面向对象编程范式的核心，是现代软件开发中广泛应用的重要基础。</p>
+<h3 id="封装">封装</h3>
+<p>封装是面向对象方法的重要原则，就是把对象的属性和操作（或服务）结合为一个独立的整体，并尽可能隐藏对象的内部实现细节。
+简单的说，一个类就是一个封装了数据以及操作这些数据的代码的逻辑实体。在一个对象内部，某些代码或某些数据可以是私有的，不能被外界访问。
+通过这种方式，对象对内部数据提供了不同级别的保护，以防止程序中无关的部分意外的改变或错误的使用了对象的私有部分。</p>
+<p>良好的封装能够减少耦合，提高了可维护性和灵活性以及可重用性，允许类内部结构自由修改，并对成员变量进行精确控制，同时有效隐藏信息和实现细节。
+封装的目的是增强安全性和简化编程，使用者不必了解具体的实现细节，而只是要通过外部接口以特定的访问权限来使用类的成员。
+其中包括<code>private</code>、<code>protected</code>和<code>public</code>三个访问权限修饰符，如果不加修饰符，则表示包级可见（<code>default</code>）。</p>
+<table>
+<thead>
+<tr>
+<th>修饰符</th>
+<th>当前类</th>
+<th>同一包下</th>
+<th>其他包的子类</th>
+<th>不同包的子类</th>
+<th>其他包</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>public</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+</tr>
+<tr>
+<td>protected</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y/N</td>
+<td>N</td>
+</tr>
+<tr>
+<td>default</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+<td>N</td>
+<td>N</td>
+</tr>
+<tr>
+<td>private</td>
+<td>Y</td>
+<td>N</td>
+<td>N</td>
+<td>N</td>
+<td>N</td>
+</tr>
+</tbody>
+</table>
+<p>这四种访问权限的控制符能够控制类中成员的可见性，当然需要满足在不使用Java反射的情况下。</p>
+<ul>
+<li><code>private</code>：仅在定义它们的类内部可见。</li>
+<li><code>protected</code>：同一个包内的类和该类的子类可以访问。</li>
+<li><code>default</code>：包级可见性，同一个包内的类可以访问。</li>
+<li><code>public</code>：任何类都可以访问。</li>
+</ul>
+<p>设计良好的模块会隐藏所有的实现细节，把它的<code>API</code>与它的实现清晰地隔离开来。
+模块之间只通过它们的<code>API</code>进行通信，一个模块不需要知道其他模块的内部工作情况，这个概念被称为信息隐藏或封装。因此访问权限应当尽可能地使每个类或者成员不被外界访问。
+如果子类的方法重写了父类的方法，那么子类中该方法的访问级别不允许低于父类的访问级别。这是为了确保可以使用父类实例的地方都可以使用子类实例，也就是确保满足里氏替换原则。</p>
+<p>某个类的字段决不能是公有的，因为这么做的话就失去了对这个字段修改行为的控制，其他类可以对其随意修改。
+下面的例子中，<code>AccessExample</code>拥有id公有字段，如果在某个时刻，我们想要使用<code>int</code>存储<code>id</code>字段，那么就需要修改所有类中的代码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AccessExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// public int id;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>可以使用公有的<code>getter</code>和<code>setter</code>方法来替换公有字段，这样的话就可以控制对字段的修改行为，实现了封装。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AccessExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setId</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>但是也有例外，如果是包级私有的类或者私有的嵌套类，那么直接暴露成员不会有特别大的影响。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AccessWithInnerClassExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">class</span> <span class="nc">InnerClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">InnerClass</span><span class="w"> </span><span class="n">innerClass</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">AccessWithInnerClassExample</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">innerClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InnerClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">innerClass</span><span class="p">.</span><span class="na">x</span><span class="p">;</span><span class="w">  </span><span class="c1">// 直接访问</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="继承">继承</h3>
+<p>继承可以使用父类的所有功能，并在无需重新编写原来类的情况下对这些功能进行扩展。 通过继承创建的新类称为“子类”或“派生类”，被继承的类称为“基类”、“父类”或“超类”。
+继承的过程，就是从一般到特殊的过程。继承概念的实现方式有两种，<strong>实现继承</strong>与<strong>接口继承</strong>。实现继承是指直接使用基类的属性和方法而无需额外编码的能力；接口继承是指仅使用属性和方法的名称、但是子类必须提供实现的能力。</p>
+<ul>
+<li>实现继承：如果多个类的某个部分的功能相同，那么可以抽象出一个类来，把相同的部分放到父类中，让他们继承这个类；</li>
+<li>接口继承：如果多个类处理的目标是一样的，但是处理的方法方式不同，那么就定义一个接口，也就是一个标准，让他们的实现这个接口，各自实现自己具体的处理方法来处理那个目标；</li>
+</ul>
+<p>继承的根本原因是因为要复用，而实现的根本原因是需要定义一个标准。</p>
+<h4 id="继承与组合">继承与组合</h4>
+<p>继承是实现复用代码的重要手段，但是继承会破坏封装；组合也是代码复用的重要方式，可以提供良好的封装性。</p>
+<table>
+<thead>
+<tr>
+<th>特性</th>
+<th>组合</th>
+<th>继承</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>优点</td>
+<td>不破坏封装，整体类与局部类之间松耦合，彼此相对独立；具有较好的可扩展性；支持动态组合，运行时可以选择不同类型的局部对象；整体类可以对局部类进行包装，提供新的接口。</td>
+<td>子类能自动继承父类的接口；支持扩展父类的功能；创建子类对象时无需创建父类对象。</td>
+</tr>
+<tr>
+<td>缺点</td>
+<td>整体类不能自动获得和局部类同样的接口；创建整体类对象时需要创建所有局部类的对象。</td>
+<td>破坏封装，子类与父类之间紧密耦合，子类依赖于父类的实现，缺乏独立性；增加系统结构的复杂度；不支持动态继承，子类无法选择不同的父类。</td>
+</tr>
+</tbody>
+</table>
+<p>在设计中，通常会同时使用继承和组合来实现代码的复用和关系建模，具体根据需求和设计原则来选择合适的关系模型。
+组合比继承更加灵活，所以在写代码如果这个功能组合和继承都能够完成，那么应该优先选择组合，但是继承在一些场景还是要优先于组合的：</p>
+<ul>
+<li>继承要慎用，其使用场合仅限于你确信使用该技术有效的情况。一个判断方法是，问一问自己是否需要从新类向基类进行向上转型。如果是必须的，则继承是必要的。反之则应该好好考虑是否需要继承。</li>
+<li>只有当子类真正是超类的子类型时，才适合用继承。换句话说，对于两个类A和B，只有当两者之间确实存在<code>is-a</code>关系的时候，类B才应该继承类A。</li>
+</ul>
+<p>通过下列代码可以发现，子类可以访问父类的成员变量方法，并且通过重写可以改变父类方法实现从而破坏了封装性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 继承</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">B</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">B</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">b</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;I am super class ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">B</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">A</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 调用父类成员 </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">t</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="kd">super</span><span class="p">.</span><span class="na">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在继承结构中，父类的内部细节对于子类是可见的。所以我们通常也可以说通过继承的代码复用是一种白盒式代码复用。
+如果基类的实现发生改变，那么派生类的实现也将随之改变，这样就导致了子类行为的不可预知性。</p>
+<p>为了保证父类有良好的封装性，不会对子类随意更改，设计父类时应遵循以下原则：</p>
+<ul>
+<li>尽量隐藏父类的内部数据.尽量把所有父类的所有成员变量都用<code>private</code>修饰，不要让子类直接访问父类的成员；</li>
+<li>不要让子类随意的修改访问父类的方法，父类中那些仅为辅助其他的工具方法，应该使用<code>private</code>修饰，让子类无法访问该方法。如果父类中的方法需要被外部类调用，则需以<code>public</code>修饰，但又不希望重写父类方法可以使用<code>final</code>来修饰方法；
+但如果希望父类某个方法被重写，但又不希望其他类访问自由，可以使用<code>protected</code>修饰；</li>
+<li>尽量不要在父类构造器中调用将要被子类重写的方法；</li>
+</ul>
+<p><code>super</code>关键字通常用在继承的子类中，通常有以下作用：</p>
+<ul>
+<li>访问父类的构造函数：可以使用<code>super</code>函数访问父类的构造函数，从而委托父类完成一些初始化的工作。
+应该注意到，子类一定会调用父类的构造函数来完成初始化工作，一般是调用父类的默认构造函数，如果子类需要调用父类其它构造函数，那么就可以使用<code>super</code>函数。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Parent</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Parent constructor&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Child</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">();</span><span class="w"> </span><span class="c1">// 调用父类构造方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Child constructor&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>访问父类的成员：如果子类重写了父类的某个方法，可以通过使用<code>super </code>关键字来引用父类的方法实现。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Parent&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Child&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">displayName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Child&#39;s name: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">     </span><span class="c1">// 输出 Child</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Parent&#39;s name: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 Parent</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在子类中调用父类的方法：这对于子类重写父类方法时，希望在子类方法中调用父类方法的场景非常有用。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Parent&#39;s display method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">display</span><span class="p">();</span><span class="w"> </span><span class="c1">// 调用父类的display方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Child&#39;s display method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>继承是类与类或者接口与接口之间最常见的关系，继承是一种<code>is-a</code>的关系。而组合强调的是整体与部分、拥有的关系，即<code>has-a</code>的关系。
+组合是把旧类对象作为新类对象的成员变量组合进来，用以实现新类的功能。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">B</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">B</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">b</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;I am super class ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">B</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">B</span><span class="p">(</span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 复用 A 类提供的 test 方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">a</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>组合是通过对现有的对象进行拼装产生新的、更复杂的功能。因为在对象之间，各自的内部细节是不可见的，所以我们也说这种方式的代码复用是黑盒式代码复用。因为组合中一般都定义一个类型，所以在编译期根本不知道具体会调用哪个实现类的方法。</p>
+<h4 id="抽象类与接口">抽象类与接口</h4>
+<p>抽象类和接口也是Java继承体系中的重要组成部分。
+抽象类是用来捕捉子类的通用特性的，而接口则是抽象方法的集合；抽象类不能被实例化，只能被用作子类的超类，是被用来创建继承层级里子类的模板，而接口只是一种形式，自身不能做任何事情。</p>
+<p>抽象类和抽象方法都使用<code>abstract</code>关键字进行声明。如果一个类中包含抽象方法，那么这个类必须声明为抽象类。
+抽象类和普通类最大的区别是，抽象类不能被实例化，需要继承抽象类才能实例化其子类。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractClassExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func2</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;func2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractExtendClassExample</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractClassExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;func1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实例化抽象类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// AbstractClassExample ac1 = new AbstractClassExample(); </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实例化抽象类子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// AbstractClassExample ac2 = new AbstractExtendClassExample();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// ac2.func1();</span><span class="w">
+</span></span></span></code></pre></div><p>接口是抽象类的延伸，在Java8之前，它可以看成是一个完全抽象的类，也就是说它不能有任何的方法实现。
+但从Java8 开始，接口也可以拥有默认的方法实现，这是因为不支持默认方法的接口的维护成本太高了。在Java8之前，如果一个接口想要添加新的方法，那么要修改所有实现了该接口的类，现在不用修改所有实现该接口的类。</p>
+<p>接口中的成员（字段、方法）默认都是<code>public</code>的，并且不允许定义为<code>private</code>或者 <code>protected</code>。
+接口的字段默认都是用<code>static</code>和<code>final</code>修饰的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">InterfaceExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">default</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func2</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;func2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">123</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// int y;               // Variable &#39;y&#39; might not have been initialized</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">       </span><span class="c1">// Modifier &#39;public&#39; is redundant for interface fields</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// private int k = 0;   // Modifier &#39;private&#39; not allowed here</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// protected int l = 0; // Modifier &#39;protected&#39; not allowed here</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// private void fun3(); // Modifier &#39;private&#39; not allowed here</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">InterfaceImplementExample</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">InterfaceExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;func1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>Java的接口可以多继承：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">interface</span> <span class="nc">Action</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Serializable</span><span class="p">,</span><span class="n">AutoCloseable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="c1">// to do ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>从设计层面上看，抽象类提供了一种<code>is-a</code>关系，那么就必须满足里式替换原则，即子类对象必须能够替换掉所有父类对象。
+而接口更像是一种 <code>like-a</code> 关系，它只是提供一种方法实现契约，并不要求接口和实现接口的类具有 <code>is-a</code> 关系。
+抽象类是一种自下而上的思想，而接口是一种自上而下的思想。抽象类是将多个类的公共特点聚合到同一个类中，然后实现父类的方法；接口更像是对类的一种约束，其他类调用实现某接口的类。</p>
+<p>从语法角度来看，一个类可以实现多个接口，但是不能继承多个抽象类。接口的字段只能是<code>static</code>和<code>final</code>类型的，而抽象类的字段没有这种限制，接口的成员只能是<code>public</code>的，而抽象类的成员可以有多种访问权限。</p>
+<p>接口适合的情况包括需要让不相关的类都实现相同方法，例如实现<code>Comparable</code>接口中的<code>compareTo</code>方法，以及需要实现类似多重继承的效果。
+抽象类则更适合于多个相关类需要共享代码逻辑，或者需要控制继承来的成员访问权限，以及需要继承非静态和非常量字段的场景。选择使用接口或抽象类取决于设计需求和代码结构的具体情况。</p>
+<p>在很多情况下，接口优先于抽象类。因为接口没有抽象类严格的类层次结构要求，可以灵活地为一个类添加行为。
+并且从Java8开始，接口也可以有默认的方法实现，使得修改接口的成本也变的很低。</p>
+<h3 id="多态">多态</h3>
+<p>多态是面向对象编程中的一个重要概念，它允许对象以多种形式出现。
+在Java中，多态主要通过继承和接口来实现。多态性使得一个对象可以被看作是其本身的类型，也可以被看作是其父类或接口的类型。
+多态存在的前提，有类继承或者接口实现、子类要重写父类的方法、父类的引用指向子类的对象，如：<code>Parent p = new Child();</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">contextLoads</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am Parent ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">contextLoads</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am Child ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">mainTest</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Parent</span><span class="w"> </span><span class="n">child</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Child</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// i am Child ... </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">child</span><span class="p">.</span><span class="na">contextLoads</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>通过多态，可以将相似的操作封装在父类或接口中，子类只需要实现或重写这些操作，从而减少代码的重复。
+多态使得程序更加灵活和可扩展，可以在不修改现有代码的情况下增加新的功能。
+通过多态，可以用接口来定义一组可互换的操作，使得代码更具通用性。
+但多态不能使用子类特有的方法和属性，在编写代码期间使用多态调用方法或属性时，编译工具首先会检查父类中是否有该方法和属性，如果没有则会编译报错。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">contextLoads</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am Parent ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w">  </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;child&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">contextLoads</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am Child ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">mainTest</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Parent</span><span class="w"> </span><span class="n">child</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Child</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译报错: 无法解析 &#39;Parent&#39; 中的方法 &#39;test&#39;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">child</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译报错: 不能解决符号 &#39;c&#39;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">child</span><span class="p">.</span><span class="na">c</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="重写与重载">重写与重载</h4>
+<p>多态分为两种主要类型：静态绑定（编译时多态）和动态绑定（运行时多态）。</p>
+<p>动态绑定发生在运行时，主要通过方法重写实现，我们通常所说的多态就是指这个。重写存在于继承体系中，指子类实现了一个与父类在方法声明上完全相同的一个方法。
+动态绑定的关键在于：父类的引用可以指向子类的对象，方法调用在运行时根据实际对象类型来决定执行哪个方法。</p>
+<p>为了满足里式替换原则，重写有以下三个限制，使用<code>@Override</code>注解，可以让编译器帮忙检查是否满足这三个限制条件。</p>
+<ul>
+<li>子类方法的访问权限必须大于等于父类方法；</li>
+<li>子类方法的返回类型必须是父类方法返回类型或为其子类型；</li>
+<li>子类方法抛出的异常类型必须是父类抛出异常类型或为其子类型；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Animal</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">makeSound</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Animal makes a sound&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">makeSound</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Dog barks&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Cat</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">makeSound</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Cat meows&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TestDynamicBinding</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">myDog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">myCat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Cat</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">myDog</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"> </span><span class="c1">// 输出 &#34;Dog barks&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">myCat</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"> </span><span class="c1">// 输出 &#34;Cat meows&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>静态绑定发生在编译时，主要通过方法重载实现。
+重载是在一个类里面，方法名字相同，但参数类型、个数、顺序至少有一个不同，返回类型可以相同也可以不同。应该注意的是，只有返回值不同，其它都相同不算是重载。编译器在编译时决定调用哪一个方法。
+每个重载的方法都必须有一个独一无二的参数类型列表。最常用的地方就是构造器的重载。</p>
+<p>重载规则：</p>
+<ul>
+<li>被重载的方法必须改变参数列表(参数个数或类型不一样)；</li>
+<li>被重载的方法可以改变返回类型；</li>
+<li>被重载的方法可以改变访问修饰符；</li>
+<li>被重载的方法可以声明新的或更广的检查异常；</li>
+<li>方法能够在同一个类中或者在一个子类中被重载；</li>
+<li>无法以返回值类型作为重载函数的区分标准；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Overloading</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">test</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;test1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;test2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">   
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//以下两个参数类型顺序不同</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;test3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;returntest3&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">   
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;test4&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;returntest4&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">   
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Overloading</span><span class="w"> </span><span class="n">o</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Overloading</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">o</span><span class="p">.</span><span class="na">test</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">o</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">o</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="s">&#34;test3&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">o</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="s">&#34;test4&#34;</span><span class="p">,</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>方法的重写和重载是Java多态性的不同表现，重写是父类与子类之间多态性的一种表现，重载可以理解成多态的具体表现形式。
+方法重载是一个类中定义了多个方法名相同，而他们的参数的数量不同或数量相同而类型和次序不同，则称为方法的重载。
+方法重写是在子类存在方法与父类的方法的名字相同，而且参数的个数与类型一样，返回值也一样的方法，就称为重写。
+方法重载是一个类的多态性的表现，而方法重写是子类与父类的一种多态性表现。</p>
+<h2 id="设计模式">设计模式</h2>
+<p>设计模式是一套被反复使用、多数人知晓的、经过分类编目的、代码设计经验的总结，使用设计模式是为了可重用代码、让代码更容易被他人理解、保证代码可靠性、高内聚低耦合。
+虽然<a href="https://baike.baidu.com/item/GoF/6406151?fr=aladdin">GoF</a>设计模式只有23个，但是它们各具特色，每个模式都为某一个可重复的设计问题提供了一套解决方案。
+根据它们的用途，设计模式可分为创建型，结构型和行为型三种，其中创建型模式主要用于描述如何创建对象，结构型模式主要用于描述如何实现类或对象的组合，行为型模式主要用于描述类或对象怎样交互以及怎样分配职责。
+在GoF23种设计模式中包含5种创建型设计模式、7种结构型设计模式和11种行为型设计模式。此外，根据某个模式主要是用于处理类之间的关系还是对象之间的关系，设计模式还可以分为类模式和对象模式。</p>
+<p>设计模式练习网站: <a href="https://java-design-patterns.com/patterns">https://java-design-patterns.com/patterns</a></p>
+<table>
+<thead>
+<tr>
+<th>设计模式类型</th>
+<th>设计模式名称</th>
+<th>介绍</th>
+<th>学习难度</th>
+<th>使用频率</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>创建型模式(6种)</td>
+<td>单例模式</td>
+<td>保证一个类仅有一个对象，并提供一个访问它的全局访问点。</td>
+<td>★☆☆☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>简单工厂模式</td>
+<td>定义一个工厂类，它可以根据参数的不同返回不同类的实例，被创建的实例通常都具有共同的父类。</td>
+<td>★★☆☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>工厂方法模式</td>
+<td>定义一个用于创建对象的接口，让子类决定将哪一个类实例化。</td>
+<td>★★☆☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>抽象工厂模式</td>
+<td>提供一个创建一系列相关或相互依赖对象的接口，而无需指定它们的具体类。</td>
+<td>★★★★☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>原型模式</td>
+<td>使用原型实例指定创建对象的种类，并且通过拷贝这些原型创建新的对象。</td>
+<td>★★★☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>建造者模式</td>
+<td>将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示。</td>
+<td>★★★★☆</td>
+<td>★★☆☆☆</td>
+</tr>
+<tr>
+<td>结构型模式(7种)</td>
+<td>适配器模式</td>
+<td>将一个类的接口转换成客户希望的另一个接口。适配器模式使得原本由于接口不兼容而不能一起工作的那些类可以一起工作。</td>
+<td>★★☆☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>桥接模式</td>
+<td>将抽象部分与它的实现部分分离，使他们都可以独立地变化。</td>
+<td>★★★☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>组合模式</td>
+<td>组合多个对象形成树形结构以表示具有“整体—部分”关系的层次结构。组合模式对单个对象和组合对象的使用具有一致性。</td>
+<td>★★★☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>装饰模式</td>
+<td>动态地给一个对象增加一些额外的职责，就增加对象功能来说，装饰模式比生成子类实现更为灵活。</td>
+<td>★★★☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>外观模式</td>
+<td>为子系统中的一组接口提供一个统一的入口。外观模式定义了一个高层接口，这个接口使得这一子系统更加容易使用。</td>
+<td>★☆☆☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>享元模式</td>
+<td>运用共享技术有效地支持大量细粒度的对象。</td>
+<td>★★★★☆</td>
+<td>★☆☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>代理模式</td>
+<td>为其他对象提供一个代理以控制对这个对象的访问。</td>
+<td>★★★☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td>行为模式(11种)</td>
+<td>职责链模式</td>
+<td>为解除请求的发送者和接收者之间的耦合，而使多个对象都有机会处理这个请求。将这些对象连成一条链，并沿着这条链传递该请求，直到有对象处理它。</td>
+<td>★★★☆☆</td>
+<td>★★☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>命令模式</td>
+<td>将一个请求封装为一个对象，从而使你可用不同的请求对客户进行参数化，对请求排队或记录请求日志，以及支持可取消的操作。</td>
+<td>★★★☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>解释器模式</td>
+<td>定义一个语言，定义它的文法的一种表示，并定义一个解释器，该解释器使用该表示来解释语言中的句子。</td>
+<td>★★★★★</td>
+<td>★☆☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>迭代器模式</td>
+<td>提供一种方法顺序访问一个聚合对象中各个元素，而又不需暴露该对象的内部表示。</td>
+<td>★★★☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>中介者模式</td>
+<td>用一个中介对象来封装一系列的对象交互。中介者使各对象不需要显示地相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互。</td>
+<td>★★★☆☆</td>
+<td>★★☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>备忘录模式</td>
+<td>在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保持该状态，这样以后就可以将该对象恢复到保存的状态。</td>
+<td>★★☆☆☆</td>
+<td>★★☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>观察者模式</td>
+<td>定义对象间的一种一对多的依赖关系，以便当一个对象的状态发生改变时，所有依赖于它的对象都得到通知并自动刷新。</td>
+<td>★★★☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>状态模式</td>
+<td>允许一个对象在其内部状态改变时改变它的行为。对象看起来似乎修改了它所属的类。</td>
+<td>★★★☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>策略模式</td>
+<td>定义一系列的算法，把它们一个个封装起来，并且使他们可相互替换。本模式使得算法的变化可以独立于使用它的客户。</td>
+<td>★☆☆☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>模板方法模式</td>
+<td>定义一个操作中的算法的骨架，而将一些步骤延迟到子类。</td>
+<td>★★☆☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>访问者模式</td>
+<td>表示一个作用于某对象结构中的各元素的操作。它使你可以在不改变各元素类别的前提下定义作用于这些元素的新操作。</td>
+<td>★★★★☆</td>
+<td>★☆☆☆☆</td>
+</tr>
+</tbody>
+</table>
+<h3 id="单例模式">单例模式</h3>
+<p>确保某一个类只有一个实例，而且自行实例化并向整个系统提供这个实例，这个类称为单例类，它提供全局访问的方法。单例模式是一种对象创建型模式。
+单例模式设计就是采用一定的方法保证在整个程序中，对某个类只能存在一个对象的实例，并且该类只提供一个取得其对象实例的方法。</p>
+<p>单例模式作用：</p>
+<ul>
+<li>在内存里只有一个实例，减少了内存的开销，尤其是频繁的创建和销毁实例（比如网站首页页面缓存）；</li>
+<li>避免对资源的多重占用（比如写文件操作）；</li>
+</ul>
+<p>单例模式主要应用在需要频繁的进行创建和销毁的对象、创建对象时耗时过多或耗费资源过多、重量级对象，但又经常用到的对象、工具类对象、频繁访问数据库或文件的对象(比如数据源、<code>session</code> 工厂等)。
+单例模式在Java中有6种实现。</p>
+<table>
+<thead>
+<tr>
+<th>名称</th>
+<th>优点</th>
+<th>缺点</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>饿汉式</td>
+<td>线程安全，写法简单</td>
+<td>不懒加载，可能造成浪费</td>
+</tr>
+<tr>
+<td>懒汉式(线程不安全)</td>
+<td>懒加载</td>
+<td>线程不安全</td>
+</tr>
+<tr>
+<td>懒汉式(线程安全)</td>
+<td>线程安全，懒加载</td>
+<td>效率很低，反序列化破坏单例</td>
+</tr>
+<tr>
+<td>双重校验锁</td>
+<td>线程安全，懒加载</td>
+<td>反序列化破坏单例</td>
+</tr>
+<tr>
+<td>静态内部类式</td>
+<td>线程安全，懒加载</td>
+<td>反序列化破坏单例</td>
+</tr>
+<tr>
+<td>枚举式</td>
+<td>防止反射攻击，反序列化创建对象，写法简单</td>
+<td>不能传参，不能继承其他类</td>
+</tr>
+</tbody>
+</table>
+<h4 id="饿汉式">饿汉式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这种写法比较简单，就是在类加载的时候就完成实例化。避免了线程同步问题。但是在类装载的时候就完成实例化，没有达到懒加载的效果。如果从始至终从未使用过这个实例，则会造成内存的浪费。</p>
+<h4 id="线程不安全的懒汉式">线程不安全的懒汉式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">instance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>起到了懒加载的效果，但是只能在单线程下使用。如果在多线程下，一个线程进入了<code>if (singleton == null)</code>判断语句块，还未来得及往下执行，另一个线程也通过了这个判断语句，这时便会产生多个实例，所以在多线程环境下不可使用这种方式。</p>
+<h4 id="线程安全的懒汉式">线程安全的懒汉式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">instance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>虽然解决了线程安全问题但是效率太低了，每个线程在想获得类的实例时候，执行<code>getInstance()</code>方法都要进行同步。而其实这个方法只执行一次实例化代码就够了，后面的想获得该类实例，直接 <code>return</code>就行了。</p>
+<h4 id="双重校验锁">双重校验锁</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * volatile在这作用: 禁止JVM指令重排
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">instance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">Singleton</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">instance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Double-Check</code>概念是多线程开发中常使用到的，如代码中所示，我们进行了两次<code>if (singleton == null)</code>检查，这样就可以保证线程安全了。
+这样，实例化代码只用执行一次，后面再次访问时，判断<code>if (singleton == null)</code>，直接<code>return</code>实例化对象，也避免的反复进行方法同步。</p>
+<h4 id="静态内部类式">静态内部类式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">InnerClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">InnerClass</span><span class="p">.</span><span class="na">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这种方式同样利用了<code>classloder</code>的机制来保证初始化<code>instance</code>时只有一个线程，它跟饿汉式不同的是（很细微的差别）：饿汉式是只要<code>Singleton</code>类被装载了，那么<code>instance</code>就会被实例化（没有达到<code>lazy loading</code>效果），而这种方式是<code>Singleton</code>类被装载了，<code>instance</code>不一定被初始化。
+因为<code>SingletonHolder</code>类没有被主动使用，只有显示通过调用<code>getInstance</code>方法时，才会显示装载<code>SingletonHolder</code>类，从而实例化<code>instance</code>。
+想象一下，如果实例化<code>instance</code>很消耗资源，我想让他延迟加载，另外一方面，我不希望在<code>Singleton</code>类加载时就实例化，因为我不能确保<code>Singleton</code>类还可能在其他的地方被主动使用从而被加载，那么这个时候实例化<code>instance</code>显然是不合适的。
+这个时候，这种方式相比饿汉式更加合理。</p>
+<h4 id="枚举式">枚举式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">enum</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">INSTAMCE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这种方式是《Effective Java》作者<code>Josh Bloch</code>提倡的方式，借助 JDK1.5 中添加的枚举来实现单例模式。不仅能避免多线程同步问题，而且还能防止反序列化重新创建新的对象。</p>
+<h4 id="单例与序列化">单例与序列化</h4>
+<p>上述单例模式6种写法除了枚举式单例外其他5种写法都存在序列化问题。序列化可以破坏单例，原因是序列化会通过反射调用无参数的构造方法创建一个新的对象。</p>
+<p>要想防止序列化对单例的破坏，只要在单例类中定义<code>readResolve</code>方法就可以解决该问题。原理是反序列化时，会通过反射的方式调用要被反序列化的类的<code>readResolve</code>方法，所以在这个方法中可以自定义序列化的方式。
+主要在<code>Singleton</code>类中定义<code>readResolve</code>方法，并在该方法中指定要返回的对象的生成策略，就可以防止单例被破坏。
+以双重校验锁为例，在该单例类中插入<code>readResolve</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="w"> </span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getSingleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">Singleton</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">readResolve</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="工厂模式">工厂模式</h3>
+<p>工厂模式是将实例化的对象代码提取出来，放到一个类中统一管理和维护，达到和主项目的依赖关系的解耦，从而提高项目的扩展和维护性。
+创建对象实例时不要直接<code>new</code>类，而是把这个<code>new</code>类的动作放在一个工厂的方法中并返回。不要让类继承具体的类，而是继承抽象类或者实现接口。</p>
+<h4 id="简单工厂模式">简单工厂模式</h4>
+<p>简单工厂模式，定义一个工厂类，它可以根据参数的不同返回不同类的实例，被创建的实例通常都具有共同的父类。
+因为在简单工厂模式中用于创建实例的方法是静态方法，因此简单工厂模式又被称为静态工厂方法模式，它属于类创建型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SimpleFactoryDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SimpleFactory</span><span class="p">.</span><span class="na">getTest</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SimpleFactoryImpl1</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SimpleFactoryInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am  simpleFactory 1 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SimpleFactoryImpl2</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SimpleFactoryInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am  simpleFactory 2 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SimpleFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getTest</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">1</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">SimpleFactoryImpl1</span><span class="w"> </span><span class="n">simpleFactory</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SimpleFactoryImpl1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">simpleFactory</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">2</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">SimpleFactoryImpl2</span><span class="w"> </span><span class="n">simpleFactoryImpl2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SimpleFactoryImpl2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">simpleFactoryImpl2</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">default</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>简单工厂模式的优点是实现了对象创建和使用的分离，符合面向接口编程的思想，从而实现代码解耦。然而，如果工厂内包含的逻辑和职责过多，会导致代码臃肿和扩展困难。
+尤其是在产品类型较多时，添加新产品需要修改工厂逻辑，可能导致系统维护和扩展变得复杂。简单工厂模式适用于创建对象较少且业务逻辑不复杂的场景。</p>
+<h4 id="工厂方法模式">工厂方法模式</h4>
+<p>工厂方法模式，定义一个用于创建对象的接口，让子类决定将哪一个类实例化。工厂方法模式让一个类的实例化延迟到其子类。
+工厂方法模式又简称为工厂模式，又可称作虚拟构造器模式或多态工厂模式。工厂方法模式是一种类创建型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FactoryMethodDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FoodFactory</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ColdRiceNoodleFactory</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">f</span><span class="p">.</span><span class="na">getFood</span><span class="p">().</span><span class="na">eat</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 扩展需要增加产品及相应产品工厂并实现相关接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Food</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Food</span><span class="w"> </span><span class="nf">getFood</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RiceNoodle</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;eat rice noodle ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RiceNoodleFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FoodFactory</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Food</span><span class="w"> </span><span class="nf">getFood</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ColdRiceNoodle</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;eat cold rice noodle ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ColdRiceNoodleFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Food</span><span class="w"> </span><span class="nf">getFood</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>工厂方法模式是简单工厂模式的延伸，它继承了简单工厂模式的优点，同时还弥补了简单工厂模式的不足。
+使用工厂方法模式扩展时，无须修改抽象工厂和抽象产品提供的接口，无须修改客户端，也无须修改其他的具体工厂和具体产品，只要添加一个具体工厂和具体产品就可以了，这样系统的可扩展性也就变得非常好，完全符合“开闭原则”。
+但是在添加新产品时，需要编写新的具体产品类，而且还要提供与之对应的具体工厂类，系统中类的个数将成对增加，在一定程度上增加了系统的复杂度，有更多的类需要编译和运行，会给系统带来一些额外的开销。</p>
+<h4 id="抽象工厂模式">抽象工厂模式</h4>
+<p>抽象工厂模式，提供一个创建一系列相关或相互依赖对象的接口，而无须指定它们具体的类。抽象工厂模式又称为Kit模式，它是一种对象创建型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">interface</span> <span class="nc">Food</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ColdRiceNoodle</span><span class="w"> </span><span class="nf">getColdRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RiceNoodle</span><span class="w"> </span><span class="nf">getRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RiceNoodle</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;eating rice noodle&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ColdRiceNoodle</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;eating cold rice noodle&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RiceNoodleFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="w"> </span><span class="nf">getColdRiceNoodle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="w"> </span><span class="nf">getRiceNoodle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ColdRiceNoodleFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="w"> </span><span class="nf">getColdRiceNoodle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="w"> </span><span class="nf">getRiceNoodle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>抽象工厂模式是工厂方法模式的进一步延伸，仍然具有工厂方法和简单工厂的优点。抽象工厂模式隔离了具体类的生成，使得客户并不需要知道什么被创建。
+由于这种隔离，更换一个具体工厂就变得相对容易，所有的具体工厂都实现了抽象工厂中定义的那些公共接口，因此只需改变具体工厂的实例，就可以在某种程度上改变整个软件系统的行为。
+但是抽象工厂也存在一些缺点，增加新的产品等级结构麻烦，需要对原有系统进行较大的修改，甚至需要修改抽象层代码，这显然会带来较大的不便，违背了“开闭原则”。</p>
+<h3 id="原型模式">原型模式</h3>
+<p>在Java中通过<code>new</code>关键字创建的对象是非常繁琐的，在我们需要大量对象的情况下，原型模式就是我们可以考虑实现的方式。
+使用原型实例指定创建对象的种类，并且通过拷贝这些原型创建新的对象。原型模式是一种对象创建型模式。</p>
+<p>原型模式我们也称为克隆模式，即一个某个对象为原型克隆出来一个一模一样的对象，该对象的属性和原型对象一模一样，而且对于原型对象没有任何影响。
+原型模式的克隆方式有两种，浅克隆和深度克隆；浅克隆和深克隆的主要区别在于是否支持引用类型的成员变量的复制。</p>
+<h4 id="浅克隆">浅克隆</h4>
+<p>在浅克隆中，当对象被复制时只复制它本身和其中包含的值类型的成员变量，而引用类型的成员对象并没有复制。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ShallowClone</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">cloneHuman</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CloneHuman</span><span class="p">(</span><span class="s">&#34;黑色&#34;</span><span class="p">,</span><span class="s">&#34;大眼睛&#34;</span><span class="p">,</span><span class="s">&#34;高鼻梁&#34;</span><span class="p">,</span><span class="s">&#34;大嘴巴&#34;</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(</span><span class="n">123231231231L</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">clone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman</span><span class="p">)</span><span class="n">cloneHuman</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;头发：%s,眼睛：%s,鼻子：%s,嘴巴：%s,生日：%s&#34;</span><span class="p">,</span><span class="n">clone</span><span class="p">.</span><span class="na">getHair</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getEye</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getNodes</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getMouse</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getBirth</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;浅克隆，引用类型地址比较：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">cloneHuman</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">clone</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CloneHuman</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getHair</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHair</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getEye</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setEye</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getNodes</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNodes</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getMouse</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setMouse</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneHuman</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">,</span><span class="n">Date</span><span class="w"> </span><span class="n">brith</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">brith</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="nf">getBirth</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setBirth</span><span class="p">(</span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>Java提供的<code>Cloneable</code>接口和<code>Serializable</code>接口的代码非常简单，它们都是空接口，这种空接口也称为标识接口，标识接口中没有任何方法的定义，其作用是告诉JRE这些接口的实现类是否具有某个功能，如是否支持克隆、是否支持序列化等。</p>
+<p>应该注意的是，<code>clone</code>方法并不是<code>Cloneable</code>接口的方法，而是<code>Object</code>的一个<code>protected</code>方法。
+<code>Cloneable</code>接口只是规定，如果一个类没有实现<code>Cloneable</code>接口又调用了<code>clone()</code>方法，就会抛出 <code>CloneNotSupportedException</code>。</p>
+<h4 id="深克隆">深克隆</h4>
+<p>在深克隆中，除了对象本身被复制外，对象所包含的所有成员变量也将复制。
+深克隆有两种实现方式，第一种是在浅克隆的基础上实现，第二种是通过序列化和反序列化实现。</p>
+<p>在浅克隆的基础上实现：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DeepClone</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">cloneHuman</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CloneHuman</span><span class="p">(</span><span class="s">&#34;黑色&#34;</span><span class="p">,</span><span class="s">&#34;大眼睛&#34;</span><span class="p">,</span><span class="s">&#34;高鼻梁&#34;</span><span class="p">,</span><span class="s">&#34;大嘴巴&#34;</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(</span><span class="n">123231231231L</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">clone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman</span><span class="p">)</span><span class="n">cloneHuman</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;头发：%s,眼睛：%s,鼻子：%s,嘴巴：%s,生日：%s&#34;</span><span class="p">,</span><span class="n">clone</span><span class="p">.</span><span class="na">getHair</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getEye</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getNodes</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getMouse</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getBirth</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;深克隆，引用类型地址比较：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">cloneHuman</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">clone</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CloneHuman</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getHair</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHair</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getEye</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setEye</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getNodes</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNodes</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getMouse</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setMouse</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneHuman</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">,</span><span class="n">Date</span><span class="w"> </span><span class="n">brith</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">brith</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">human</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman</span><span class="p">)</span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">human</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Date</span><span class="p">)</span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">human</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="nf">getBirth</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setBirth</span><span class="p">(</span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>序列化反序列化实现深克隆：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DeepClone2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman2</span><span class="w"> </span><span class="n">cloneHuman1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CloneHuman2</span><span class="p">(</span><span class="s">&#34;黑色&#34;</span><span class="p">,</span><span class="s">&#34;大眼睛&#34;</span><span class="p">,</span><span class="s">&#34;高鼻梁&#34;</span><span class="p">,</span><span class="s">&#34;大嘴巴&#34;</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(</span><span class="n">123231231231L</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用序列化和反序列化实现深克隆</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ByteArrayOutputStream</span><span class="w"> </span><span class="n">bos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ByteArrayOutputStream</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="n">bos</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">cloneHuman1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bos</span><span class="p">.</span><span class="na">toByteArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ByteArrayInputStream</span><span class="w"> </span><span class="n">bis</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ByteArrayInputStream</span><span class="p">(</span><span class="n">bytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="n">bis</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 克隆好的对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman2</span><span class="w"> </span><span class="n">cloneHuman2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman2</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;深克隆，引用类型地址比较：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">cloneHuman1</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">cloneHuman2</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CloneHuman2</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="p">,</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getHair</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHair</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getEye</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setEye</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getNodes</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNodes</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getMouse</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setMouse</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneHuman2</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">,</span><span class="n">Date</span><span class="w"> </span><span class="n">brith</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">brith</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman2</span><span class="w"> </span><span class="n">human</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman2</span><span class="p">)</span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">human</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Date</span><span class="p">)</span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">human</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="nf">getBirth</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setBirth</span><span class="p">(</span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="总结">总结</h4>
+<p>原型模式作为一种快速创建大量相同或相似对象的方式，在软件开发中应用较为广泛，很多软件提供的复制和粘贴操作就是原型模式的典型应用。
+通过<code>clone</code>的方式在获取大量对象的时候性能开销基本没有什么影响，而<code>new</code>的方式随着实例的对象越来越多，性能会急剧下降，所以原型模式是一种比较重要的获取实例的方式。</p>
+<p>优点：</p>
+<ul>
+<li>当创建新的对象实例较为复杂时，使用原型模式可以简化对象的创建过程，提高创建对象的效率。</li>
+<li>可以使用深克隆的方式保存对象的状态，使用原型模式将对象复制一份并将其状态保存起来，可辅助实现撤销操作。</li>
+<li>扩展性较好，由于在原型模式中提供了抽象原型类，在客户端可以针对抽象原型类进行编程，而将具体原型类写在配置文件中，增加或减少产品类对原有系统都没有任何影响。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>需要为每一个类配备一个克隆方法，而且该克隆方法位于一个类的内部，当对已有的类进行改造时，需要修改源代码，违背了“开闭原则”。</li>
+<li>在实现深克隆时需要编写较为复杂的代码，而且当对象之间存在多重的嵌套引用时，为了实现深克隆，每一层对象对应的类都必须支持深克隆，实现起来可能会比较麻烦。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>原型模式很少单独出现，一般是和工厂方法模式一起出现，通过<code>clone</code>的方法创建一个对象，然后由工厂方法提供给调用者。</li>
+<li><code>Spring</code>中<code>bean</code>的创建实际就是两种：单例模式和原型模式。</li>
+<li>创建新对象成本较大，新的对象可以通过原型模式对已有对象进行复制来获得。</li>
+<li>系统要保存对象的状态，而对象的状态变化很小，或者对象本身占用内存较少时，可以使用原型模式配合备忘录模式来实现。</li>
+</ul>
+<h3 id="建造者模式">建造者模式</h3>
+<p>建造者模式，将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示。建造者模式是一种对象创建型模式。
+建造者模式是较为复杂的创建型模式，它将客户端与包含多个组成部分的复杂对象的创建过程分离，客户端无须知道复杂对象的内部组成部分与装配方式，只需要知道所需建造者的类型即可。
+它关注如何一步一步创建一个的复杂对象，不同的具体建造者定义了不同的创建过程，且具体建造者相互独立，增加新的建造者非常方便，无须修改已有代码，系统具有较好的扩展性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Director</span><span class="w"> </span><span class="n">director</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Director</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Builder</span><span class="w"> </span><span class="n">commonBuilder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CommonRole</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">director</span><span class="p">.</span><span class="na">construct</span><span class="p">(</span><span class="n">commonBuilder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Role</span><span class="w"> </span><span class="n">commonRole</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">commonBuilder</span><span class="p">.</span><span class="na">getRole</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">commonRole</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Role</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">body</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">foot</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">sp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">hp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setSp</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">sp</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">sp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getSp</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">sp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHp</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hp</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getHp</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">hp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Role{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;head=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, body=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">body</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, foot=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">foot</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, sp=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">sp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, hp=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">hp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Builder</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderHead</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderBody</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderFoot</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderSp</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderHp</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderName</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Role</span><span class="w"> </span><span class="nf">getRole</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Role</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CommonRole</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Builder</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Role</span><span class="w"> </span><span class="n">role</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Role</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderHead</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;building head .....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderBody</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;building body .....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderFoot</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;building foot .....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderSp</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">role</span><span class="p">.</span><span class="na">setSp</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderHp</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">role</span><span class="p">.</span><span class="na">setHp</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">role</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;lucy&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Role</span><span class="w"> </span><span class="nf">getRole</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">role</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Director</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">construct</span><span class="p">(</span><span class="n">Builder</span><span class="w"> </span><span class="n">builder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderHead</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderBody</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderFoot</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderHp</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderSp</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderName</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>优点：</p>
+<ul>
+<li>客户端不必知道产品内部组成的细节，将产品本身与产品的创建过程解耦，使得相同的创建过程可以创建不同的产品对象。</li>
+<li>建造者模式很容易进行扩展。如果有新的需求，通过实现一个新的建造者类就可以完成，基本上不用修改之前已经测试通过的代码，因此也就不会对原有功能引入风险，符合开放封闭原则。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>若产品内部发生变化，建造者都要修改，成本较大；若内部变化复杂，会有很多的建造类。</li>
+<li>产品必须有共同点，使用范围有限。建造者模式创造出来的产品，其组成部分基本相同。如果产品之间的差异较大，则不适用这个模式。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>需要生成的产品对象有复杂的内部结构，这些产品对象通常包含多个成员属性。</li>
+<li>需要生成的产品对象的属性相互依赖，需要指定其生成顺序。</li>
+<li>对象的创建过程独立于创建该对象的类。在建造者模式中引入了指挥者类，将创建过程封装在指挥者类中，而不在建造者类中。</li>
+<li>隔离复杂对象的创建和使用，并使得相同的创建过程可以创建不同的产品。</li>
+</ul>
+<h3 id="适配器模式">适配器模式</h3>
+<p>适配器模式，将一个接口转换成客户希望的另一个接口(指广义的接口，它可以表示一个方法或者方法的集合)，使接口不兼容的那些类可以一起工作，其别名为包装器。
+适配器模式既可以作为类结构型模式，也可以作为对象结构型模式。</p>
+<p>在适配器模式中，我们通过增加一个新的适配器类来解决接口不兼容的问题，使得原本没有任何关系的类可以协同工作。根据适配器类与适配者类的关系不同，适配器模式可分为对象适配器和类适配器两种，在对象适配器模式中，适配器与适配者之间是关联关系。
+在类适配器模式中，适配器与适配者之间是继承或实现关系。</p>
+<h4 id="对象适配器">对象适配器</h4>
+<p>由于在Java中不支持多重继承，而且有破坏封装之嫌。所以提倡多用组合少用继承，在实际开发中推荐使用对象适配器模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">RedHat</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Linux</span><span class="p">()).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Win10</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Windows</span><span class="p">()).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Adapter</span><span class="w"> </span><span class="n">adapter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Adapter</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Windows</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">RedHat</span><span class="p">(</span><span class="n">adapter</span><span class="p">).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">LinuxSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">WindowsSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Linux</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;linux 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Windows</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;windows 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RedHat</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RedHat</span><span class="p">(</span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">linuxSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">useInputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始使用 redHat 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">linuxSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;结束使用 redHat 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Win10</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Win10</span><span class="p">(</span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">windowsSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">useInputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始使用 win10 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">windowsSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;结束使用 win10 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 在 Linux 系统上使用 windows 输入法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Adapter</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Adapter</span><span class="p">(</span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">windowsSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">windowsSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="类适配器">类适配器</h4>
+<p>类适配器模式和对象适配器模式最大的区别在于适配器和适配者之间的关系不同，对象适配器模式中适配器和适配者之间是关联关系，而类适配器模式中适配器和适配者是继承关系。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">RedHat</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Linux</span><span class="p">()).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Win10</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Windows</span><span class="p">()).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Adapter</span><span class="w"> </span><span class="n">adapter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Adapter</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">RedHat</span><span class="p">(</span><span class="n">adapter</span><span class="p">).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">LinuxSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">WindowsSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Linux</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;linux 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Windows</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;windows 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RedHat</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RedHat</span><span class="p">(</span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">linuxSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">useInputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始使用 redHat 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">linuxSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;结束使用 redHat 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Win10</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Win10</span><span class="p">(</span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">windowsSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">useInputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始使用 win10 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">windowsSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;结束使用 win10 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 在 Linux 系统上使用 windows 输入法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Adapter</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Windows</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="总结-1">总结</h4>
+<p>适配器模式将现有接口转化为客户类所期望的接口，实现了对现有类的复用，它是一种使用频率非常高的设计模式，在软件开发中得以广泛应用，在<code>Spring</code>等开源框架、驱动程序设计（如<code>JDBC</code>中的数据库驱动程序）中也使用了适配器模式。</p>
+<p>优点：</p>
+<ul>
+<li>将目标类和适配者类解耦，通过引入一个适配器类来重用现有的适配者类，无须修改原有结构。</li>
+<li>增加了类的透明性和复用性，同时系统的灵活性和扩展性都非常好，更换适配器或者增加新的适配器都非常方便。可以在不修改原有代码的基础上增加新的适配器类，完全符合开放封闭原则。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>过多地使用适配器，会让系统非常零乱，不易整体进行把握。比如，明明看到调用的是 A 接口，其实内部被适配成了 B 接口的实现，一个系统如果太多出现这种情况，无异于一场灾难。因此如果不是很有必要，可以不使用适配器。</li>
+<li>对象适配器模式的缺点是很难置换适配者类的方法。</li>
+<li>类适配器模式中的目标抽象类只能为接口，不能为类，其使用有一定的局限性。</li>
+</ul>
+<p>使用场景</p>
+<ul>
+<li>系统需要使用现有的类，而这些类的接口不符合系统的需要；想要建立一个可以重复使用的类，用于与一些彼此之间没有太大关联的一些类一起工作。</li>
+<li>系统需要使用现有的类，而此类的接口不符合系统的需要。</li>
+<li>想要建立一个可以重复使用的类，用于与一些彼此之间没有太大关联的一些类，包括一些可能在将来引进的类一起工作，这些源类不一定有一致的接口。</li>
+<li>通过接口转换，将一个类插入另一个类系中。如，老虎和飞禽，现在多了一个飞虎，在不增加实体的需求下，增加一个适配器，在里面包容一个虎对象，实现飞的接口。</li>
+</ul>
+<h3 id="桥接模式">桥接模式</h3>
+<p>桥接模式，将实现与抽象放在两个不同的类层次中，使两个层次可以独立改变。它是一种对象结构型模式，又称为柄体模式或接口模式。
+桥接模式是一种很实用的结构型设计模式，如果软件系统中某个类存在两个独立变化的维度，通过该模式可以将这两个维度分离出来，使两者可以独立扩展，让系统更加符合“单一职责原则”。</p>
+<p>如手机制造，内存是一个公司生产，芯片是另一个公司生产，而品牌又是另一个公司。我们需要什么样子的手机就把相应的芯片、内存组装起来。桥接模式就是把两个不同维度的东西桥接起来。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Phone_A</span><span class="w"> </span><span class="n">phone_a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Phone_A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_a</span><span class="p">.</span><span class="na">setAbstractChip</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Chip_A</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_a</span><span class="p">.</span><span class="na">setAbstractMemory</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Memory_A</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_a</span><span class="p">.</span><span class="na">finished</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Phone_B</span><span class="w"> </span><span class="n">phone_b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Phone_B</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_b</span><span class="p">.</span><span class="na">setAbstractChip</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Chip_B</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_b</span><span class="p">.</span><span class="na">setAbstractMemory</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Memory_A</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_b</span><span class="p">.</span><span class="na">finished</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractMemory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractChip</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">type</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span>  <span class="nc">AbstractPhone</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractMemory</span><span class="w"> </span><span class="n">abstractMemory</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractChip</span><span class="w"> </span><span class="n">abstractChip</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAbstractChip</span><span class="p">(</span><span class="n">AbstractChip</span><span class="w"> </span><span class="n">abstractChip</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">abstractChip</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">abstractChip</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAbstractMemory</span><span class="p">(</span><span class="n">AbstractMemory</span><span class="w"> </span><span class="n">abstractMemory</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">abstractMemory</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">abstractMemory</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finished</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Memory_A</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractMemory</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">size</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;create 6G of memory ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Memory_B</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractMemory</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">size</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;create 8G of memory ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Chip_A</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractChip</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">type</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;snapdragon 888 chip ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Chip_B</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractChip</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">type</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;A14 chip ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Phone_A</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPhone</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finished</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractMemory</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractChip</span><span class="p">.</span><span class="na">type</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;phone_a assembly completed ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Phone_B</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPhone</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finished</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractMemory</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractChip</span><span class="p">.</span><span class="na">type</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;phone_b assembly completed ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>桥接模式是设计Java虚拟机和实现JDBC等驱动程序的核心模式之一，应用较为广泛。
+在软件开发中如果一个类或一个系统有多个变化维度时，都可以尝试使用桥接模式对其进行设计。桥接模式为多维度变化的系统提供了一套完整的解决方案，并且降低了系统的复杂度。</p>
+<p>优点：</p>
+<ul>
+<li>实现了抽象和实现部分的分离，从而极大的提供了系统的灵活性，让抽象部分和实现部分独立开来，这有助于系统进行分层设计，从而产生更好的结构化系统。</li>
+<li>优秀的扩展能力。在两个变化维度中任意扩展一个维度，都不需要修改原有系统，符合开放封闭原则。</li>
+<li>桥接模式替代多层继承方案，可以减少子类的个数，降低系统的管理和维护成本。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>桥接模式的引入会增加系统的理解与设计难度，由于聚合关联关系建立在抽象层，要求开发者针对抽象进行设计与编程。</li>
+<li>桥接模式要求正确识别出系统中两个独立变化的维度(抽象、和实现)，因此其使用范围有一定的局限性，即需要有这样的应用场景，如何正确识别两个独立维度也需要一定的经验积累。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>桥接模式主要解决在有多种可能会变化的情况下，用继承会造成类爆炸问题，扩展起来不灵活。对于两个独立变化的维度，使用桥接模式再适合不过了。</li>
+<li>如果一个系统需要在构件的抽象化角色和具体化角色之间增加更多的灵活性，避免在两个层次之间建立静态的继承联系，通过桥接模式可以使它们在抽象层建立一个关联关系。</li>
+</ul>
+<h3 id="组合模式">组合模式</h3>
+<p>组合模式，组合多个对象形成树形结构以表示具有“整体—部分”关系的层次结构。组合模式对单个对象和组合对象的使用具有一致性，组合模式又可以称为“整体—部分”模式，它是一种对象结构型模式。
+组合模式，是用于把一组相似的对象当作一个单一的对象。组合模式依据树形结构来组合对象，用来表示部分以及整体层次。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Tree</span><span class="w"> </span><span class="n">tree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Tree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tree</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">LeftNode</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tree</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">RightNode</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tree</span><span class="p">.</span><span class="na">implmethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">implmethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LeftNode</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception: the method is not supported. &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception: the method is not supported. &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">implmethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;left node method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RightNode</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception: the method is not supported. &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception: the method is not supported. &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">implmethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;right node method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Tree</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">AbstractTree</span><span class="o">&gt;</span><span class="w"> </span><span class="n">treeList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">treeList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">treeList</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">implmethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;tree node&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">treeList</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">implmethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>组合模式使用面向对象的思想来实现树形结构的构建与处理，描述了如何将容器对象和叶子对象进行递归组合，实现简单，灵活性好。
+由于在软件开发中存在大量的树形结构，因此组合模式是一种使用频率较高的结构型设计模式。在XML解析、组织结构树处理、文件系统设计等领域，组合模式都得到了广泛应用。</p>
+<p>优点：</p>
+<ul>
+<li>高层模块调用简单。客户端可以一致地使用一个组合结构或其中单个对象，不必关心处理的是单个对象还是整个组合结构。</li>
+<li>在组合模式中节点增加自由，无须对现有类库进行任何修改，符合开闭原则。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>在使用组合模式时，其叶子和树的声明都是实现类，而不是接口，违反了依赖倒置原则。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>部分、整体场景，如树形菜单，文件、文件夹的管理。</li>
+<li>希望用户忽略组合对象与单个对象的不同，用户将统一地使用组合结构中的所有对象。</li>
+</ul>
+<h3 id="装饰模式">装饰模式</h3>
+<p>装饰模式，动态地给一个对象增加一些额外的职责，就增加对象功能来说，装饰模式比生成子类实现更为灵活。装饰模式是一种对象结构型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Drink</span><span class="w"> </span><span class="n">coffee</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ShortBlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单价格：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">cost</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单描述：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">getDesc</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">coffee</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Chocolate</span><span class="p">(</span><span class="n">coffee</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单价格：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">cost</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单描述：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">getDesc</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">coffee</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Milk</span><span class="p">(</span><span class="n">coffee</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单价格：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">cost</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单描述：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">getDesc</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Drink</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">price</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setDesc</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">desc</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">desc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getDesc</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setPrice</span><span class="p">(</span><span class="kt">double</span><span class="w"> </span><span class="n">price</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">price</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">price</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">getPrice</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">price</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">cost</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ShortBlock</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Drink</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ShortBlock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setPrice</span><span class="p">(</span><span class="n">3</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;ShortBlock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">cost</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">getPrice</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LongBlock</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Drink</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">LongBlock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setPrice</span><span class="p">(</span><span class="n">5</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;LongBlock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">cost</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">getPrice</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CoffeeShop</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Drink</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Drink</span><span class="w"> </span><span class="n">coffee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="nf">CoffeeShop</span><span class="p">(</span><span class="n">Drink</span><span class="w"> </span><span class="n">coffee</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">coffee</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">coffee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">cost</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">getPrice</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">cost</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getDesc</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">desc</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">getPrice</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="s">&#34; &amp;&amp; &#34;</span><span class="o">+</span><span class="w">  </span><span class="n">coffee</span><span class="p">.</span><span class="na">getDesc</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Milk</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">CoffeeShop</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Milk</span><span class="p">(</span><span class="n">Drink</span><span class="w"> </span><span class="n">seasoning</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">seasoning</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;Milk&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setPrice</span><span class="p">(</span><span class="n">6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Chocolate</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">CoffeeShop</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Chocolate</span><span class="p">(</span><span class="n">Drink</span><span class="w"> </span><span class="n">seasoning</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">seasoning</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;Chocolate&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setPrice</span><span class="p">(</span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>装饰模式降低了系统的耦合度，可以动态增加或删除对象的职责，并使得需要装饰的具体构件类和具体装饰类可以独立变化，以便增加新的具体构件类和具体装饰类。
+在软件开发中，装饰模式应用较为广泛，例如在<code>JavaIO</code>中的输入流和输出流的设计、<code>javax.swing</code>包中一些图形界面构件功能的增强等地方都运用了装饰模式。</p>
+<p>一般的，我们为了扩展一个类经常使用继承方式实现，由于继承为类引入静态特征，并且随着扩展功能的增多，子类会很膨胀，装饰者模式主要解决这个问题。</p>
+<p>优点：</p>
+<ul>
+<li>对于扩展一个对象的功能，装饰模式比继承更加灵活性，不会导致类的个数急剧增加。</li>
+<li>装饰类和被装饰类可以独立发展，不会相互耦合，装饰模式是继承的一个替代模式，装饰模式可以动态扩展一个实现类的功能。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>多层装饰比较复杂。</li>
+<li>使用装饰模式进行系统设计时将产生很多小对象，这些对象的区别在于它们之间相互连接的方式有所不同，而不是它们的类或者属性值有所不同，大量小对象的产生势必会占用更多的系统资源，在一定程序上影响程序的性能。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>这种模式创建了一个装饰类，用来包装原有的类，并在保持类方法签名完整性的前提下，提供了额外的功能，可代替继承。</li>
+<li>扩展一个类的功能。</li>
+<li>动态增加功能，动态撤销功能。</li>
+<li>当不能采用继承的方式对系统进行扩展或者采用继承不利于系统扩展和维护时可以使用装饰模式。不能采用继承的情况主要有两类：
+<ul>
+<li>第一类是系统中存在大量独立的扩展，为支持每一种扩展或者扩展之间的组合将产生大量的子类，使得子类数目呈爆炸性增长；</li>
+<li>第二类是因为类已定义为不能被继承；</li>
+</ul>
+</li>
+</ul>
+<h3 id="外观模式">外观模式</h3>
+<p>外观模式，为子系统中的一组接口提供一个统一的入口。外观模式定义了一个高层接口，这个接口使得这一子系统更加容易使用。
+外观模式又称为门面模式，它是一种对象结构型模式。外观模式是迪米特法则的一种具体实现，通过引入一个新的外观角色可以降低原有系统的复杂度，同时降低客户类与子系统的耦合度。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Facade</span><span class="w"> </span><span class="n">facade</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Facade</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">facade</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Facade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="n">c</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">D</span><span class="w"> </span><span class="n">d</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Facade</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="p">.</span><span class="na">getInstance</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">B</span><span class="p">.</span><span class="na">getInstance</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">C</span><span class="p">.</span><span class="na">getInstance</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">d</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">D</span><span class="p">.</span><span class="na">getInstance</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">a</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">b</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">c</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">d</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * A调用B类，A调用C类，B调用C类，D调用B类，D调用C类
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">private</span><span class="w"> </span><span class="nf">A</span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="n">B</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="n">C</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;A class test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">B</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">B</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">B</span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">C</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;B class test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">C</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">C</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">C</span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kd">static</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;C class test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">D</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">D</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">D</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">D</span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">D</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">B</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">C</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;D class test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>外观模式的主要目的在于降低系统的复杂程度，在面向对象软件系统中，类与类之间的关系越多，不能表示系统设计得越好，反而表示系统中类之间的耦合度太大，这样的系统在维护和修改时都缺乏灵活性，因为一个类的改动会导致多个类发生变化，而外观模式的引入在很大程度上降低了类与类之间的耦合关系。
+引入外观模式之后，增加新的子系统或者移除子系统都非常方便，客户类无须进行修改（或者极少的修改），只需要在外观类中增加或移除对子系统的引用即可。
+从这一点来说，外观模式在一定程度上并不符合开放封闭原则，增加新的子系统需要对原有系统进行一定的修改，虽然这个修改工作量不大。</p>
+<p>优点：</p>
+<ul>
+<li>减少关联关系；对客户端屏蔽了具体的实现，使得子系统使用起来更加容易；客户端代码将变得很简单，与之关联的对象也很少。</li>
+<li>解耦合；具体实现有改变不会影响到调用的客户端，只需要调整外观类即可。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>如果设计不当，扩展时增加新的实现可能需要修改外观类的源代码，违背了开放封闭原则.</li>
+<li>不能很好地限制客户端直接使用子系统类，如果对客户端访问子系统类做太多的限制则减少了可变性和灵活性。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>当要为访问一系列复杂的子系统提供一个简单入口时可以使用外观模式。</li>
+<li>客户端程序与多个子系统之间存在很大的依赖性。引入外观类可以将子系统与客户端解耦，从而提高子系统的独立性和可移植性。</li>
+<li>在层次化结构中，可以使用外观模式定义系统中每一层的入口，层与层之间不直接产生联系，而通过外观类建立联系，降低层之间的耦合度。</li>
+</ul>
+<h3 id="享元模式">享元模式</h3>
+<p>享元模式，运用共享技术有效地支持大量细粒度对象的复用。系统只使用少量的对象，而这些对象都很相似，状态变化很小，可以实现对象的多次复用。
+由于享元模式要求能够共享的对象必须是细粒度对象，因此它又称为轻量级模式，它是一种对象结构型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WebSiteFactory</span><span class="w"> </span><span class="n">webSiteFactory</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WebSiteFactory</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;新闻&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;lucy&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;新闻&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;jane&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;博客&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;jack&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;博客&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;maik&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;博客&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;seven&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;网站类型共：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">countWebSiteType</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WebSite</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">use</span><span class="p">(</span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ConcreateWebSite</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WebSite</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ConcreateWebSite</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">use</span><span class="p">(</span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;网站类型名称：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="s">&#34;\t 网站用户：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">user</span><span class="p">.</span><span class="na">getUsername</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">User</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">User</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">username</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setUsername</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">username</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getUsername</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">WebSiteFactory</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">WebSite</span><span class="o">&gt;</span><span class="w"> </span><span class="n">pool</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WebSite</span><span class="w"> </span><span class="nf">getWebSite</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">webSiteName</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">pool</span><span class="p">.</span><span class="na">containsKey</span><span class="p">(</span><span class="n">webSiteName</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">pool</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">webSiteName</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcreateWebSite</span><span class="p">(</span><span class="n">webSiteName</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">pool</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">webSiteName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">countWebSiteType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">pool</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>当系统中存在大量相同或者相似的对象时，享元模式是一种较好的解决方案，它通过共享技术实现相同或相似的细粒度对象的复用，从而节约了内存空间，提高了系统性能。
+相比其他结构型设计模式，享元模式的使用频率并不算太高，但是作为一种以“节约内存，提高性能”为出发点的设计模式，它在软件开发中还是得到了一定程度的应用。如：<code>String</code>、Java的池技术等。</p>
+<p>享元模式主要解决在有大量对象时，有可能会造成内存溢出，我们把其中共同的部分抽象出来，如果有相同的业务请求，直接返回在内存中已有的对象，避免重新创建。</p>
+<p>优点：</p>
+<ul>
+<li>大大减少对象的创建，降低系统的内存，使效率提高。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>提高了系统的复杂度，需要分离出外部状态和内部状态，而且外部状态具有固有化的性质，不应该随着内部状态的变化而变化，否则会造成系统的混乱。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>在使用享元模式时需要维护一个存储享元对象的享元池，而这需要耗费一定的系统资源，因此，应当在需要多次重复使用享元对象时才值得使用享元模式。</li>
+<li>系统有大量相似对象。</li>
+<li>需要缓冲池的场景。</li>
+</ul>
+<h3 id="代理模式">代理模式</h3>
+<p>代理模式，给某一个对象提供一个代理或占位符，并由代理对象来控制对原对象的访问。
+代理模式是为一个对象提供一个替身，以控制对这个对象的访问，即通过代理对象访问目标对象。
+这样做的好处是，可以在目标对象实现的基础上，增强额外的功能操作，即扩展目标对象的功能。被代理的对象可以是远程对象、创建开销大的对象或需要安全控制的对象。
+代理模式有不同的形式，主要有三种 静态代理、动态代理 (<code>JDK</code>代理、<code>Cglib</code>代理)。</p>
+<h4 id="静态代理">静态代理</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ProxyImpl</span><span class="w"> </span><span class="n">proxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ProxyImpl</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StaticProxy</span><span class="w"> </span><span class="n">staticProxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StaticProxy</span><span class="p">(</span><span class="n">proxy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">staticProxy</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">ProxyInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ProxyImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ProxyInterface</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;helloWorld&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">StaticProxy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ProxyInterface</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ProxyImpl</span><span class="w"> </span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">StaticProxy</span><span class="w"> </span><span class="p">(</span><span class="n">ProxyImpl</span><span class="w"> </span><span class="n">target</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">target</span><span class="o">=</span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;静态代理之前...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">target</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;静态代理之后...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>静态代理能在不修改目标对象的功能前提下，能通过代理对象对目标进行扩展。
+但是因为代理对象需要与目标对象实现相同的接口，所以会有很多代理类一旦接口增加方法后，目标对象与代理对象都需要维护。</p>
+<h4 id="jdk动态代理">JDK动态代理</h4>
+<p>JDK动态代理，代理对象不需要实现接口，但是目标对象需要实现接口，否则不能实现动态代理。代理对象的生产是利用JDK的API，动态的在内存中构建代理对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ProxyImpl</span><span class="w"> </span><span class="n">proxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ProxyImpl</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ProxyInterface</span><span class="w"> </span><span class="n">jdkProxyInterface</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">ProxyInterface</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">JDKProxy</span><span class="p">().</span><span class="na">bind</span><span class="p">(</span><span class="n">proxy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">jdkProxyInterface</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">ProxyInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ProxyImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ProxyInterface</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;helloWorld&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">JDKProxy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//通用类型，表示被代理的真实对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">bind</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">target</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">target</span><span class="o">=</span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//生成代理类（与被代理对象实现相同接口的兄弟类）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">Proxy</span><span class="p">.</span><span class="na">newProxyInstance</span><span class="p">(</span><span class="n">target</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getClassLoader</span><span class="p">(),</span><span class="w"> </span><span class="n">target</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getInterfaces</span><span class="p">(),</span><span class="w"> </span><span class="p">(</span><span class="n">proxy</span><span class="p">,</span><span class="w"> </span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;JDK动态代理前&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">res</span><span class="o">=</span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">target</span><span class="p">,</span><span class="w"> </span><span class="n">args</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;JDK动态代理后&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="cglib动态代理">Cglib动态代理</h4>
+<p><code>Cglib</code>代理也叫作子类代理，它是在内存中构建一个子类对象从而实现对目标对象功能扩展。
+<code>Cglib</code>是一个强大的高性能的代码生成包，它可以在运行期扩展Java类与实现Java接口，广泛的被许多AOP的框架使用，例如<code>Spring AOP</code>，实现方法拦截。</p>
+<p>以下测试代码需要导入<code>Cglib</code>和<code>asm</code>相关jar包：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">asm-3.3.1.jar
+</span></span><span class="line"><span class="cl">cglib-2.2.jar
+</span></span></code></pre></div><p>使用<code>Cglib</code>实现动态代理时出现了下面这个异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Exception in thread &#34;main&#34; java.lang.IncompatibleClassChangeError: 
+</span></span><span class="line"><span class="cl">class net.sf.cglib.core.DebuggingClassWriter has interface org.objectweb.asm.ClassVisitor as super class
+</span></span></code></pre></div><p>原因是<code>cglib.jar</code>包含<code>asm.jar</code>包。报错内容是<code>ClassVisitor</code>的父类不相容。<a href="https://my.oschina.net/itblog/blog/528613">详细原因分析</a>。
+测试时用<code>cglib2.2.jar</code>和<code>asm3.3.1.jar</code>版本，解决jar包冲突问题。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Target</span><span class="w"> </span><span class="n">target</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Target</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Target</span><span class="w"> </span><span class="n">bind</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Target</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">CGLibProxy</span><span class="p">().</span><span class="na">bind</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bind</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Target</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;helloWorld&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CGLibProxy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">MethodInterceptor</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="n">Object</span><span class="w"> </span><span class="nf">bind</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">target</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Enhancer</span><span class="w"> </span><span class="n">enhancer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Enhancer</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">enhancer</span><span class="p">.</span><span class="na">setSuperclass</span><span class="p">(</span><span class="n">target</span><span class="p">.</span><span class="na">getClass</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">enhancer</span><span class="p">.</span><span class="na">setCallback</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">enhancer</span><span class="p">.</span><span class="na">create</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">intercept</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">proxy</span><span class="p">,</span><span class="w"> </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">,</span><span class="w"> </span><span class="n">MethodProxy</span><span class="w"> </span><span class="n">methodProxy</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Object</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;CGLib动态代理前&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">res</span><span class="o">=</span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">target</span><span class="p">,</span><span class="w"> </span><span class="n">args</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;CGLib动态代理后&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="总结-2">总结</h4>
+<p>代理模式是常用的结构型设计模式之一，它为对象的间接访问提供了一个解决方案，可以对对象的访问进行控制。
+代理模式主要解决，在直接访问对象时带来的问题。比如说，要访问的对象在远程的机器上。在面向对象系统中，有些对象由于某些原因，对象创建开销很大，或者某些操作需要安全控制，或者需要进程外的访问，直接访问会给使用者或者系统结构带来很多麻烦，我们可以在访问此对象时加上一个对此对象的访问层。</p>
+<p>优点：</p>
+<ul>
+<li>职责清晰。能够协调调用者和被调用者，在一定程度上降低了系统的耦合度。</li>
+<li>高扩展性。增加和更换代理类无须修改源代码，符合开闭原则，系统具有较好的灵活性和可扩展性。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>由于在客户端和真实主题之间增加了代理对象，因此有些类型的代理模式可能会造成请求的处理速度变慢。</li>
+<li>实现代理模式需要额外的工作，有些代理模式的实现非常复杂。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>想在访问一个类时做一些控制。</li>
+</ul>
+<h3 id="职责链模式">职责链模式</h3>
+<p>职责链模式，避免请求发送者与接收者耦合在一起，让多个对象都有可能接收请求，将这些对象连接成一条链，并且沿着这条链传递请求，直到有对象处理它为止。职责链模式是一种对象行为型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 产品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">test</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RequestEntity</span><span class="p">(</span><span class="s">&#34;test&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">2000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 指定职责链</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BeforeHandler</span><span class="w"> </span><span class="n">before</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BeforeHandler</span><span class="p">(</span><span class="s">&#34;before&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AfterHandler</span><span class="w"> </span><span class="n">after</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AfterHandler</span><span class="p">(</span><span class="s">&#34;after&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PostHandler</span><span class="w"> </span><span class="n">post</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PostHandler</span><span class="p">(</span><span class="s">&#34;post&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 形成链状闭环 要确保会被责任链中的组件处理 否则会一直循环下去 ，当然也可以选择不闭环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">before</span><span class="p">.</span><span class="na">setHandler</span><span class="p">(</span><span class="n">after</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">after</span><span class="p">.</span><span class="na">setHandler</span><span class="p">(</span><span class="n">post</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">post</span><span class="p">.</span><span class="na">setHandler</span><span class="p">(</span><span class="n">before</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">after</span><span class="p">.</span><span class="na">handleRequest</span><span class="p">(</span><span class="n">test</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RequestEntity</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">grade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RequestEntity</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">,</span><span class="n">Integer</span><span class="w"> </span><span class="n">grade</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">grade</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">grade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="nf">getGrade</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">grade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Handler</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 下一个引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Handler</span><span class="w"> </span><span class="n">handler</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Handler</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHandler</span><span class="p">(</span><span class="n">Handler</span><span class="w"> </span><span class="n">handler</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">handler</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">handler</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRequest</span><span class="p">(</span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BeforeHandler</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Handler</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">BeforeHandler</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRequest</span><span class="p">(</span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;分数为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;，被&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;处理 &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">handler</span><span class="p">.</span><span class="na">handleRequest</span><span class="p">(</span><span class="n">requestEntity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">AfterHandler</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Handler</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">AfterHandler</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRequest</span><span class="p">(</span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">2000</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;分数为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;，被&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;处理 &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">handler</span><span class="p">.</span><span class="na">handleRequest</span><span class="p">(</span><span class="n">requestEntity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">PostHandler</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Handler</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">PostHandler</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRequest</span><span class="p">(</span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">3000</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;分数为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;，被&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;处理 &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">handler</span><span class="p">.</span><span class="na">handleRequest</span><span class="p">(</span><span class="n">requestEntity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>职责链模式通过建立一条链来组织请求的处理者，请求将沿着链进行传递，请求发送者无须知道请求在何时、何处以及如何被处理，实现了请求发送者与处理者的解耦。
+在软件开发中，如果遇到有多个对象可以处理同一请求时可以应用职责链模式，例如在Web应用开发中创建一个过滤器(Filter)链来对请求数据进行过滤，在工作流系统中实现公文的分级审批等等，使用职责链模式可以较好地解决此类问题。</p>
+<p>优点：</p>
+<ul>
+<li>增加新的请求处理类很方便，只需要在客户端重新建链即可，从这一点来看是符合开闭原则的。</li>
+<li>为请求创建了一个接收者对象的链式结构。对请求的发送者和接收者进行解耦。</li>
+<li>简化了对象，使得对象不需要知道链的结构。</li>
+<li>增强给对象指派职责的灵活性。通过改变链内的成员或者调动它们的次序，允许动态地新增或者删除责任。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>系统性能将受到一定影响，可能会造成循环调用。特别是在链比较长的时候，因此需控制链中最大节点数量，一般通过在<code>Handler</code>中设置一个最大节点数量，在<code>setNext</code>方法中判断是否已经超过阀值，超过则不允许该链建立，避免出现超长链无意识地破坏系统性能。</li>
+<li>调试不方便。采用了类似递归的方式，调试时逻辑可能比较复杂。可能不容易观察运行时的特征，有碍于除错。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>在处理消息的时候以过滤很多通道。</li>
+<li>有多个对象可以处理同一个请求，具体哪个对象处理该请求由运行时刻自动确定。</li>
+<li>在不明确指定接收者的情况下，向多个对象中的一个提交一个请求。</li>
+<li>可动态指定一组对象处理请求。</li>
+</ul>
+<h3 id="命令模式">命令模式</h3>
+<p>命令模式，将一个请求封装为一个对象，从而让我们可用不同的请求对客户进行参数化；对请求排队或者记录请求日志，以及支持可撤销的操作。
+命令模式是一种对象行为型模式，其别名为动作模式或事务模式。
+命令模式可以将请求发送者和接收者完全解耦，发送者与接收者之间没有直接引用关系，发送请求的对象只需要知道如何发送请求，而不必知道如何完成请求。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LightReceiver</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LightOnCommand</span><span class="w"> </span><span class="n">lightOnCommand</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LightOnCommand</span><span class="p">(</span><span class="n">lightReceiver</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LightOffCommand</span><span class="w"> </span><span class="n">lightOffCommand</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LightOffCommand</span><span class="p">(</span><span class="n">lightReceiver</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RemoteCommand</span><span class="w"> </span><span class="n">remoteCommand</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RemoteCommand</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 测试</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">remoteCommand</span><span class="p">.</span><span class="na">setCommand</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="n">lightOnCommand</span><span class="p">,</span><span class="n">lightOffCommand</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 按下开灯按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;按下开灯按钮 -------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">remoteCommand</span><span class="p">.</span><span class="na">onButtonPushed</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 按下关灯按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;按下关灯按钮 -------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">remoteCommand</span><span class="p">.</span><span class="na">offButtonPushed</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 按下撤销按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;按下撤销按钮 ---------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">remoteCommand</span><span class="p">.</span><span class="na">undoButtonPushed</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Command</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行命令
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 撤销命令
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">undo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LightReceiver</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">on</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开灯 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">off</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;关灯 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LightOnCommand</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Command</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">LightOnCommand</span><span class="p">(</span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lightReceiver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lightReceiver</span><span class="p">.</span><span class="na">on</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">undo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lightReceiver</span><span class="p">.</span><span class="na">off</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LightOffCommand</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">LightOffCommand</span><span class="p">(</span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lightReceiver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lightReceiver</span><span class="p">.</span><span class="na">off</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">undo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lightReceiver</span><span class="p">.</span><span class="na">on</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 空执行 默认命令实现类
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">NoCommand</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;默认命令执行&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">undo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;默认撤销方法&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RemoteCommand</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 存放开关命令</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">onCommands</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">offCommands</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 存放撤销命令</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">undoCommands</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RemoteCommand</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">undoCommands</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Command</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">onCommands</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Command</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">offCommands</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Command</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 默认空命令</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">onCommands</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NoCommand</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">offCommands</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NoCommand</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 设置命令</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w">  </span><span class="nf">setCommand</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">no</span><span class="p">,</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">onCommand</span><span class="p">,</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">offCommand</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">onCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">onCommand</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">offCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">offCommand</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 按下开的按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">onButtonPushed</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">no</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">onCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">.</span><span class="na">exec</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 记录撤销操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">undoCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">onCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 按下关闭的按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">offButtonPushed</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">no</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">offCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">.</span><span class="na">exec</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 记录撤销操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">undoCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">offCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 按下撤销按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">undoButtonPushed</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">no</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">undoCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">.</span><span class="na">undo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>命令模式是一种使用频率非常高的设计模式，它可以将请求发送者与接收者解耦，请求发送者通过命令对象来间接引用请求接收者，使得系统具有更好的灵活性和可扩展性。
+在基于GUI的软件开发，无论是在电脑桌面应用还是在移动应用中，命令模式都得到了广泛的应用。
+在软件系统中，行为请求者与行为实现者通常是一种紧耦合的关系，但某些场合，比如需要对行为进行记录、撤销或重做、事务等处理时，这种无法抵御变化的紧耦合的设计就不太合适。</p>
+<p>优点：</p>
+<ul>
+<li>降低了系统耦合度。</li>
+<li>新的命令可以很容易地加入到系统中。由于增加新的具体命令类不会影响到其他类，因此增加新的具体命令类很容易，无须修改原有系统源代码，甚至客户类代码，满足开闭原则的要求。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>使用命令模式可能会导致某些系统有过多的具体命令类。因为针对每一个对请求接收者的调用操作都需要设计一个具体命令类，因此在某些系统中可能需要提供大量的具体命令类，这将影响命令模式的使用。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>请求调用者需要与请求接收者解耦时，命令模式可以使调用者和接收者不直接交互。</li>
+<li>当系统需要支持命令的撤销操作和恢复操作时。</li>
+<li>系统需要在不同的时间指定请求、将请求排队和执行请求。一个命令对象和请求的初始调用者可以有不同的生命期，换言之，最初的请求发出者可能已经不在了，而命令对象本身仍然是活动的，可以通过该命令对象去调用请求接收者，而无须关心请求调用者的存在性，可以通过请求日志文件等机制来具体实现。</li>
+</ul>
+<h3 id="解释器模式">解释器模式</h3>
+<p>解释器模式，定义一个语言的文法，并且建立一个解释器来解释该语言中的句子，这里的“语言”是指使用规定格式和语法的代码。解释器模式是一种类行为型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">expStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getExpStr</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">getValue</span><span class="p">(</span><span class="n">expStr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Calculator</span><span class="w"> </span><span class="n">calculator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Calculator</span><span class="p">(</span><span class="n">expStr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;运算结果：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">expStr</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">calculator</span><span class="p">.</span><span class="na">run</span><span class="p">(</span><span class="n">var</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获得表达式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getExpStr</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;请输入表达式：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">InputStreamReader</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">in</span><span class="p">))).</span><span class="na">readLine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获得值映射</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getValue</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">expStr</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">expStr</span><span class="p">.</span><span class="na">toCharArray</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ch</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">map</span><span class="p">.</span><span class="na">containsKey</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">ch</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;请输入&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;的值：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">String</span><span class="w"> </span><span class="n">in</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">InputStreamReader</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">in</span><span class="p">))).</span><span class="na">readLine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">ch</span><span class="p">),</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">in</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">map</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 表达式解释器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 终结表达式
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">VarExpression</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">VarExpression</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 非终结表达式
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SymbolExpression</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SymbolExpression</span><span class="p">(</span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 因为 SymbolExpression  是让其子类来实现，因此 interpreter 是一个默认实现</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 减法
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SubExpression</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SymbolExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">SubExpression</span><span class="p">(</span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 加法
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">AddExpression</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SymbolExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">AddExpression</span><span class="p">(</span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 计算器 调用加减法
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Calculator</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">expression</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="nf">Calculator</span><span class="p">(</span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">expression</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">expression</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">expression</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Calculator</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">expStr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 安排运算先后顺序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">AbstractExpression</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 表达式拆分成字符数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">charArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">expStr</span><span class="p">.</span><span class="na">toCharArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//遍历我们的字符数组，  即遍历	[a, +, b]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//针对不同的情况，做处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">charArray</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">charArray</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 从 stack 取 出 left =&gt; &#34;a&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 取出右表达式 &#34;b&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">VarExpression</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">charArray</span><span class="o">[++</span><span class="n">i</span><span class="o">]</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">AddExpression</span><span class="p">(</span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 然后根据得到 left 和 right 构建 AddExpresson 加入 stack</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">VarExpression</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">charArray</span><span class="o">[++</span><span class="n">i</span><span class="o">]</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">SubExpression</span><span class="p">(</span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">default</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">//如果是一个 Var 就创建要给 VarExpression 对象，并 push 到 stack</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">VarExpression</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">charArray</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//当遍历完整个 charArray  数组后，stack 就得到最后</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">expression</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">run</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//最后将表达式 a+b 和 var = {a=10,b=20}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//然后传递给 expression 的 interpreter 进行解释执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">expression</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>解释器模式为自定义语言的设计和实现提供了一种解决方案，它用于定义一组文法规则并通过这组文法规则来解释语言中的句子。
+虽然解释器模式的使用频率不是特别高，但是它在正则表达式、XML文档解释等领域还是得到了广泛使用。
+与解释器模式类似，目前还诞生了很多基于抽象语法树的源代码处理工具，例如<code>Eclipse</code>中的<code>Eclipse AST</code>，它可以用于表示Java语言的语法结构，用户可以通过扩展其功能，创建自己的文法规则。</p>
+<p>优点：</p>
+<ul>
+<li>易于改变和扩展文法。增加新的解释表达式较为方便。如果用户需要增加新的解释表达式只需要对应增加一个新的终结符表达式或非终结符表达式类，原有表达式类代码无须修改，符合“开闭原则”。</li>
+<li>易于实现简单文法。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>可利用场景比较少。</li>
+<li>对于复杂的文法比较难维护。解释器模式会引起类膨胀，如果一个语言包含太多文法规则，类的个数将会急剧增加，导致系统难以管理和维护。</li>
+<li>解释器模式采用递归调用方法。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>对于一些固定文法构建一个解释句子的解释器。</li>
+<li>可以将一个需要解释执行的语言中的句子表示为一个抽象语法树</li>
+<li>一些重复出现的问题可以用一种简单的语言来进行表达。</li>
+<li>一个简单语法需要解释的场景。</li>
+</ul>
+<h3 id="迭代器模式">迭代器模式</h3>
+<p>迭代器模式，提供一种方法来访问聚合对象，而不用暴露这个对象的内部表示，其别名为游标。迭代器模式是一种对象行为型模式。
+迭代器模式的重要用途就是帮助我们遍历容器。迭代器模式，提供一种遍历集合元素的统一接口，用一致的方法遍历集合元素，不需要知道集合对象的底层表示，即不暴露其内部的结构。
+在迭代器模式结构中包含聚合和迭代器两个层次结构，考虑到系统的灵活性和可扩展性，在迭代器模式中应用了工厂方法模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Bread</span><span class="w"> </span><span class="n">bread</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Bread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bread</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;面粉&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bread</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;黄油&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bread</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;白糖&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bread</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;鸡蛋&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Iterator</span><span class="w"> </span><span class="n">iterator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bread</span><span class="p">.</span><span class="na">getIterator</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">iterator</span><span class="p">.</span><span class="na">hasNext</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">iterator</span><span class="p">.</span><span class="na">next</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">FoodIterator</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Iterator</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">foods</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w">      </span><span class="n">position</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">FoodIterator</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">foods</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">foods</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">foods</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">hasNext</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">position</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">foods</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">next</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">food</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">foods</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">position</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">food</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Food</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Iterator</span><span class="w"> </span><span class="nf">getIterator</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Bread</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">foods</span><span class="w">    </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[</span><span class="n">4</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w">      </span><span class="n">position</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">foods</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">position</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Iterator</span><span class="w"> </span><span class="nf">getIterator</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FoodIterator</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">foods</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>迭代器模式是一种使用频率非常高的设计模式，通过引入迭代器可以将数据的遍历功能从聚合对象中分离出来，聚合对象只负责存储数据，而遍历数据由迭代器来完成。
+由于很多编程语言的类库都已经实现了迭代器模式，因此在实际开发中，我们只需要直接使用Java、C#等语言已定义好的迭代器即可，迭代器已经成为我们操作聚合对象的基本工具之一。
+迭代器的使用现在非常广泛，因为Java中提供了<code>java.util.Iterator</code>。而且Java中的很多容器，如<code>Collection</code>、<code>Set</code>也都提供了对迭代器的支持。</p>
+<p>优点：</p>
+<ul>
+<li>提供一个统一的方法遍历对象，客户不用再考虑聚合的类型，使用一种方法就可以遍历对象了。</li>
+<li>隐藏了聚合的内部结构，客户端要遍历聚合的时候只能取到迭代器，而不会知道聚合的具体组成。</li>
+<li>提供了一种设计思想，就是一个类应该只有一个引起变化的原因。
+在聚合类中，我们把迭代器分开，就是要把管理对象集合和遍历对象集合的责任分开，这样一来集合改变的话，只影响到聚合对象。而如果遍历方式改变的话，只影响到了迭代器。</li>
+<li>当要展示一组相似对象，或者遍历一组相同对象时使用，适合使用迭代器模式</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>由于迭代器模式将存储数据和遍历数据的职责分离，增加新的聚合类需要对应增加新的迭代器类，类的个数成对增加，这在一定程度上增加了系统的复杂性。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>需要为一个聚合对象提供多种遍历方式。</li>
+<li>使用迭代器模式可以为遍历不同的聚合结构提供一个统一的接口，接口的实现类中为不同的聚合结构提供不同的遍历方式，而客户端可以一致性地操作该接口。</li>
+</ul>
+<h3 id="中介者模式">中介者模式</h3>
+<p>中介者模式，用一个中介对象（中介者）来封装一系列的对象交互，中介者使各对象不需要显式地相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互。
+中介者模式又称为调停者模式，它是一种对象行为型模式。
+如果在一个系统中对象之间存在多对多的相互关系，我们可以将对象之间的一些交互行为从各个对象中分离出来，并集中封装在一个中介者对象中，并由该中介者进行统一协调，这样对象之间多对多的复杂关系就转化为相对简单的一对多关系。
+通过引入中介者来简化对象之间的复杂交互，中介者模式是“迪米特法则”的一个典型应用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//创建一个中介者对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcreteMediator</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//创建 Alarm  并且加入到ConcreteMediator 对象的 HashMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Alarm</span><span class="w"> </span><span class="n">alarm</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Alarm</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;alarm&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//创建了 CoffeeMachine 对象，并且加入到	ConcreteMediator 对象的 HashMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CoffeeMachine</span><span class="w"> </span><span class="n">coffeeMachine</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CoffeeMachine</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;coffeeMachine&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//创建  tV , 并	且加入到	ConcreteMediator 对象的 HashMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TV</span><span class="w"> </span><span class="n">tV</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TV</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;TV&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//让闹钟发出消息 依次调用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alarm</span><span class="p">.</span><span class="na">sendAlarm</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">coffeeMachine</span><span class="p">.</span><span class="na">finishCoffee</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alarm</span><span class="p">.</span><span class="na">sendAlarm</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tV</span><span class="p">.</span><span class="na">startTv</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 中介者
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Mediator</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">register</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">,</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="n">colleague</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ConcreteMediator</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Mediator</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 集合，放入所有的同事对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Colleague</span><span class="o">&gt;</span><span class="w"> </span><span class="n">colleagueMap</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">interMap</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ConcreteMediator</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">colleagueMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">interMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">register</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">,</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="n">colleague</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">colleague</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Alarm</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">interMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;Alarm&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">colleague</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">CoffeeMachine</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">interMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;CoffeeMachine&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;........&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">colleagueName</span><span class="p">)</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Alarm</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">stateChange</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">((</span><span class="n">CoffeeMachine</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">interMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="s">&#34;CoffeeMachine&#34;</span><span class="p">)))).</span><span class="na">startCoffee</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">((</span><span class="n">TV</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">interMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="s">&#34;TV&#34;</span><span class="p">)))).</span><span class="na">startTv</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">stateChange</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">((</span><span class="n">TV</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">interMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="s">&#34;TV&#34;</span><span class="p">)))).</span><span class="na">stopTv</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">colleagueName</span><span class="p">)</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">TV</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//如果 TV 发现消息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 抽象同事类
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Colleague</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Colleague</span><span class="p">(</span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mediator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mediator</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Mediator</span><span class="w"> </span><span class="nf">getMediator</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">mediator</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Alarm</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Alarm</span><span class="p">(</span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//在创建 Alarm 同事对象时，将自己放入到 ConcreteMediator 对象中[集合]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mediator</span><span class="p">.</span><span class="na">register</span><span class="p">(</span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendAlarm</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">sendMessage</span><span class="p">(</span><span class="n">stateChange</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 调用的中介者对象的 getMessage 方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">getMediator</span><span class="p">().</span><span class="na">getMessage</span><span class="p">(</span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">TV</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">TV</span><span class="p">(</span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mediator</span><span class="p">.</span><span class="na">register</span><span class="p">(</span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">getMediator</span><span class="p">().</span><span class="na">getMessage</span><span class="p">(</span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">startTv</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;It&#39;s time to StartTv!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">stopTv</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;StopTv!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CoffeeMachine</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CoffeeMachine</span><span class="p">(</span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mediator</span><span class="p">.</span><span class="na">register</span><span class="p">(</span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">getMediator</span><span class="p">().</span><span class="na">getMessage</span><span class="p">(</span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">startCoffee</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;It&#39;s time to startcoffee!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finishCoffee</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After 5 minutes!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Coffee is ok!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sendMessage</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>中介者模式将一个网状的系统结构变成一个以中介者对象为中心的星形结构，在这个星型结构中，使用中介者对象与其他对象的一对多关系来取代原有对象之间的多对多关系。
+中介者模式在事件驱动类软件中应用较为广泛，特别是基于GUI（图形用户界面）的应用软件，此外，在类与类之间存在错综复杂的关联关系的系统中，中介者模式都能得到较好的应用。</p>
+<p>优点：</p>
+<ul>
+<li>减少类间依赖，降低了耦合，符合迪米特法则。</li>
+<li>简化了对象之间的交互，它用中介者和同事的一对多交互代替了原来同事之间的多对多交互，一对多关系更容易理解、维护和扩展，将原本难以理解的网状结构转换成相对简单的星型结构。</li>
+<li>降低了类的复杂度，将一对多转化成了一对一。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>中介者承担了较多的责任，一旦中介者出现了问题，整个系统就会受到影响。</li>
+<li>如果设计不当，可能会导致具体中介者类非常复杂，使得系统难以维护，在实际使用过程中要特别注意。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>主要解决对象与对象之间存在大量的关联关系，这样势必会导致系统的结构变得很复杂，同时若一个对象发生改变，我们也需要跟踪与之相关联的对象，同时做出相应的处理。
+应当注意不应当在职责混乱的时候使用。</li>
+<li>系统中对象之间存在比较复杂的引用关系，导致它们之间的依赖关系结构混乱而且难以复用该对象。</li>
+<li>想通过一个中间类来封装多个类中的行为，而又不想生成太多的子类。</li>
+</ul>
+<h3 id="备忘录模式">备忘录模式</h3>
+<p>备忘录模式，在不破坏封装的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态，这样可以在以后将对象恢复到原先保存的状态。它是一种对象行为型模式，其别名为<code>Token</code>。
+在设计备忘录类时需要考虑其封装性，除了<code>Originator</code>类，不允许其他类来调用备忘录类<code>Memento</code>的构造函数与相关方法，如果不考虑封装性，允许其他类调用构造方法，将导致在备忘录中保存的历史状态发生改变，通过撤销操作所恢复的状态就不再是真实的历史状态，备忘录模式也就失去了本身的意义。
+所谓备忘录模式就是在不破坏封装的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态，这样可以在以后将对象恢复到原先保存的状态。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Originator</span><span class="w"> </span><span class="n">originator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Originator</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CareTaker</span><span class="w"> </span><span class="n">careTaker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CareTaker</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">careTaker</span><span class="p">.</span><span class="na">saveMemento</span><span class="p">(</span><span class="n">originator</span><span class="p">.</span><span class="na">saveState</span><span class="p">(</span><span class="s">&#34; 状态#1 &#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">careTaker</span><span class="p">.</span><span class="na">saveMemento</span><span class="p">(</span><span class="n">originator</span><span class="p">.</span><span class="na">saveState</span><span class="p">(</span><span class="s">&#34; 状态#2 &#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">careTaker</span><span class="p">.</span><span class="na">saveMemento</span><span class="p">(</span><span class="n">originator</span><span class="p">.</span><span class="na">saveState</span><span class="p">(</span><span class="s">&#34; 状态#3 &#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;目前保存的状态为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">originator</span><span class="p">.</span><span class="na">getState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始恢复以前的状态 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originator</span><span class="p">.</span><span class="na">recover</span><span class="p">(</span><span class="n">careTaker</span><span class="p">.</span><span class="na">recover</span><span class="p">(</span><span class="n">0</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;恢复之后的状态为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">originator</span><span class="p">.</span><span class="na">getState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Originator</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Memento</span><span class="w"> </span><span class="nf">saveState</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">state</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Memento</span><span class="p">(</span><span class="n">state</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">recover</span><span class="p">(</span><span class="n">Memento</span><span class="w"> </span><span class="n">memento</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="n">memento</span><span class="p">.</span><span class="na">getState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 备忘录对象 保存对象信息
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Memento</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 需要保存状态
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Memento</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">state</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 管理备忘录对象
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CareTaker</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Memento</span><span class="o">&gt;</span><span class="w"> </span><span class="n">mementos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Memento</span><span class="w"> </span><span class="nf">recover</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="k">return</span><span class="w"> </span><span class="n">mementos</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">saveMemento</span><span class="p">(</span><span class="n">Memento</span><span class="w"> </span><span class="n">memento</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mementos</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">memento</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>备忘录模式在很多软件的使用过程中普遍存在，但是在应用软件开发中，它的使用频率并不太高，因为现在很多基于窗体和浏览器的应用软件并没有提供撤销操作。
+如果需要为软件提供撤销功能，备忘录模式无疑是一种很好的解决方案。在一些字处理软件、图像编辑软件、数据库管理系统等软件中备忘录模式都得到了很好的应用。
+为了符合迪米特原则，还要增加一个管理备忘录的类(<code>CareTaker</code>)，为了节约内存，可使用原型模式和备忘录模式。</p>
+<p>优点：</p>
+<ul>
+<li>给用户提供了一种可以恢复状态的机制，可以使用户能够比较方便地回到某个历史的状态。</li>
+<li>实现了信息的封装，使得用户不需要关心状态的保存细节。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>消耗资源。如果类的成员变量过多，势必会占用比较大的资源，而且每一次保存都会消耗一定的内存。每保存一次对象的状态都需要消耗一定的系统资源。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>很多时候我们总是需要记录一个对象的内部状态，这样做的目的就是为了允许用户取消不确定或者错误的操作，能够恢复到他原先的状态，使得他有&quot;后悔药&quot;可吃。</li>
+<li>需要保存/恢复数据的相关状态场景。</li>
+<li>提供一个可回滚的操作。</li>
+</ul>
+<h3 id="观察者模式">观察者模式</h3>
+<p>观察者模式，定义对象之间的一种一对多依赖关系，使得每当一个对象状态发生改变时，其相关依赖对象皆得到通知并被自动更新。
+观察者模式的别名包括发布-订阅模式、模型-视图模式、源-监听器模式或从属者模式。观察者模式是一种对象行为型模式。</p>
+<p>观察者模式描述了如何建立对象与对象之间的依赖关系，以及如何构造满足这种需求的系统。
+观察者模式包含观察目标和观察者两类对象，一个目标可以有任意数目的与之相依赖的观察者，一旦观察目标的状态发生改变，所有的观察者都将得到通知。
+作为对这个通知的响应，每个观察者都将监视观察目标的状态以使其状态与目标状态同步，这种交互也称为发布-订阅(Publish-Subscribe)。观察目标是通知的发布者，它发出通知时并不需要知道谁是它的观察者，可以有任意数目的观察者订阅它并接收通知。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WeatherData</span><span class="w"> </span><span class="n">weatherData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WeatherData</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CurrentCondition</span><span class="w"> </span><span class="n">currentCondition</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CurrentCondition</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BaiduSite</span><span class="w"> </span><span class="n">baiduSite</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BaiduSite</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 注册观察者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">registerObserver</span><span class="p">(</span><span class="n">currentCondition</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">registerObserver</span><span class="p">(</span><span class="n">baiduSite</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 设置数据 一旦数据变化 所有的观察者都会变化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">setWeatherData</span><span class="p">(</span><span class="n">10f</span><span class="p">,</span><span class="w"> </span><span class="n">20f</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 移除注册观察者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">removeObserver</span><span class="p">(</span><span class="n">baiduSite</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 唤醒所有已经注册的观察者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">notifyObservers</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Subject</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">registerObserver</span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">removeObserver</span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">notifyObservers</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 观察者
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Observer</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="kt">float</span><span class="w">  </span><span class="n">temperature</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">WeatherData</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Subject</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Observer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">observers</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setWeatherData</span><span class="p">(</span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">registerObserver</span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">observers</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">observer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">removeObserver</span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">observers</span><span class="p">.</span><span class="na">contains</span><span class="p">(</span><span class="n">observer</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">observers</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">observer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">notifyObservers</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 唤醒所有的观察者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">observers</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">observer</span><span class="p">.</span><span class="na">update</span><span class="p">(</span><span class="n">temperature</span><span class="p">,</span><span class="n">humidity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CurrentCondition</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Observer</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">displayed</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">displayed</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;===当前天气情况===&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前湿度：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前温度：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BaiduSite</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Observer</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">displayed</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">displayed</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;===当前百度网站天气情况===&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前湿度：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前温度：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>观察者模式是一种使用频率非常高的设计模式，无论是移动应用、Web应用或者桌面应用，观察者模式几乎无处不在，它为实现对象之间的联动提供了一套完整的解决方案，凡是涉及到一对一或者一对多的对象交互场景都可以使用观察者模式。
+观察者模式广泛应用于各种编程语言的GUI事件处理的实现，在基于事件的XML解析技术（如SAX2）以及Web事件处理中也都使用了观察者模式。</p>
+<p>优点：</p>
+<ul>
+<li>观察者和被观察者是抽象耦合的。观察目标只需要维持一个抽象观察者的集合，无须了解其具体观察者。由于观察目标和观察者没有紧密地耦合在一起，因此它们可以属于不同的抽象化层次。</li>
+<li>观察者模式满足“开闭原则”的要求，增加新的具体观察者无须修改原有系统代码，在具体观察者与观察目标之间不存在关联关系的情况下，增加新的观察目标也很方便。</li>
+<li>观察者模式可以实现表示层和数据逻辑层的分离，定义了稳定的消息更新传递机制，并抽象了更新接口，使得可以有各种各样不同的表示层充当具体观察者角色。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>如果一个被观察者对象有很多的直接和间接的观察者的话，将所有的观察者都通知到会花费很多时间。</li>
+<li>如果在观察者和观察目标之间有循环依赖的话，观察目标会触发它们之间进行循环调用，可能导致系统崩溃。</li>
+<li>观察者模式没有相应的机制让观察者知道所观察的目标对象是怎么发生变化的，而仅仅只是知道观察目标发生了变化。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>一个对象状态改变给其他对象通知的问题，而且要考虑到易用和低耦合，保证高度的协作。一个对象（目标对象）的状态发生改变，所有的依赖对象（观察者对象）都将得到通知，进行广播通知。</li>
+<li>一个抽象模型有两个方面，其中一个方面依赖于另一个方面。将这些方面封装在独立的对象中使它们可以各自独立地改变和复用。</li>
+<li>一个对象的改变将导致其他一个或多个对象也发生改变，而不知道具体有多少对象将发生改变，可以降低对象之间的耦合度。</li>
+<li>一个对象必须通知其他对象，而并不知道这些对象是谁。</li>
+<li>需要在系统中创建一个触发链，A对象的行为将影响B对象，B对象的行为将影响C对象……，可以使用观察者模式创建一种链式触发机制。</li>
+</ul>
+<p>注意事项：</p>
+<ul>
+<li>Java中已经有了对观察者模式的支持类。</li>
+<li>避免循环引用。</li>
+<li>如果顺序执行，某一观察者错误会导致系统卡壳，一般采用异步方式。</li>
+</ul>
+<h3 id="状态模式">状态模式</h3>
+<p>状态模式，允许一个对象在其内部状态改变时改变它的行为，对象看起来似乎修改了它的类。其别名为状态对象，状态模式是一种对象行为型模式。
+状态模式用于解决系统中复杂对象的状态转换以及不同状态下行为的封装问题。当系统中某个对象存在多个状态，这些状态之间可以进行转换，而且对象在不同状态下行为不相同时可以使用状态模式。
+状态模式将一个对象的状态从该对象中分离出来，封装到专门的状态类中，使得对象状态可以灵活变化，对于客户端而言，无须关心对象状态的转换以及对象所处的当前状态，无论对于何种状态的对象，客户端都可以一致处理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建活动对象，奖品有 1 个奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RaffleActivity</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 我们连续抽 300 次奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">30</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;--------第&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;次抽奖----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 参加抽奖，第一步点击扣除积分</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">debuctMoney</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 第二步抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">raffle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 扣除积分 - 50</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 是否抽中奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 发放奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RaffleActivity</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// state 表示活动当前的状态，是变化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 奖品数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 四个属性，表示四种状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">noRafflleState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NoRaffleState</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">canRaffleState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CanRaffleState</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">dispenseState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DispenseState</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">dispensOutState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DispenseOutState</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//构造器</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//1. 初始化当前的状态为 noRafflleState（即不能抽奖的状态）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//2. 初始化奖品的数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RaffleActivity</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNoRafflleState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//扣分, 调用当前状态的 deductMoney</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">debuctMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">state</span><span class="p">.</span><span class="na">deductMoney</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前的状态是抽奖成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">state</span><span class="p">.</span><span class="na">raffle</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//领取奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">state</span><span class="p">.</span><span class="na">dispensePrize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">state</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//这里请大家注意，每领取一次奖品，count--</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">curCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">curCount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setCount</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getNoRafflleState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">noRafflleState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNoRafflleState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">noRafflleState</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">noRafflleState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">noRafflleState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getCanRaffleState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">canRaffleState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setCanRaffleState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">canRaffleState</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">canRaffleState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">canRaffleState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getDispenseState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">dispenseState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setDispenseState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">dispenseState</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dispenseState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dispenseState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getDispensOutState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">dispensOutState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setDispensOutState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">dispensOutState</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dispensOutState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dispensOutState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">DispenseOutState</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 初始化时传入活动引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">DispenseOutState</span><span class="p">(</span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;奖品发送完了，请下次再参加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;奖品发送完了，请下次再参加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;奖品发送完了，请下次再参加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">DispenseState</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 初始化时传入活动引用，发放奖品后改变其状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">DispenseState</span><span class="p">(</span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不能扣除积分&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不能抽奖&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//发放奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getCount</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;恭喜中奖了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 改变状态为不能抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getNoRafflleState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;很遗憾，奖品发送完了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 改变状态为奖品发送完毕, 后面我们就不可以抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getDispensOutState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//System.out.println(&#34;抽奖活动结束&#34;);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//System.exit(0);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">NoRaffleState</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 初始化时传入活动引用，扣除积分后改变其状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">NoRaffleState</span><span class="p">(</span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 当前状态可以扣积分 , 扣除后，将状态设置成可以抽奖状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;扣除 50 积分成功，您可以抽奖了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getCanRaffleState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 当前状态不能抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;扣了积分才能抽奖喔！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 当前状态不能发奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不能发放奖品&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CanRaffleState</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CanRaffleState</span><span class="p">(</span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;已经扣取过了积分&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//可以抽奖, 抽完奖后，根据实际情况，改成新的状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;正在抽奖，请稍等！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Random</span><span class="w"> </span><span class="n">r</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Random</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">r</span><span class="p">.</span><span class="na">nextInt</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 10%中奖机会</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">num</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 改变活动状态为发放奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getDispenseState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;很遗憾没有抽中奖品！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 改变状态为不能抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getNoRafflleState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 不能发放奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;没中奖，不能发放奖品&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>状态模式将一个对象在不同状态下的不同行为封装在一个个状态类中，通过设置不同的状态对象可以让环境对象拥有不同的行为，而状态转换的细节对于客户端而言是透明的，方便了客户端的使用。
+在实际开发中，状态模式具有较高的使用频率，在工作流和游戏开发中状态模式都得到了广泛的应用，例如公文状态的转换、游戏中角色的升级等。</p>
+<p>优点：</p>
+<ul>
+<li>封装了状态的转换规则，在状态模式中可以将状态的转换代码封装在环境类或者具体状态类中，可以对状态转换代码进行集中管理，而不是分散在一个个业务方法中。</li>
+<li>将所有与某个状态有关的行为放到一个类中，只需要注入一个不同的状态对象即可使环境对象拥有不同的行为。</li>
+<li>可以让多个环境对象共享一个状态对象，从而减少系统中对象的个数。</li>
+<li>允许状态转换逻辑与状态对象合成一体，而不是提供一个巨大的条件语句块，状态模式可以让我们避免使用庞大的条件语句来将业务方法和状态转换代码交织在一起。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>状态模式的使用必然会增加系统类和对象的个数。</li>
+<li>状态模式的结构与实现都较为复杂，如果使用不当将导致程序结构和代码的混乱。</li>
+<li>状态模式对“开闭原则”的支持并不太好，增加新的状态类需要修改那些负责状态转换的源代码，否则无法转换到新增状态；而且修改某个状态类的行为也需修改对应类的源代码。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>状态模式主要解决对象的行为依赖于它的状态（属性），并且可以根据它的状态改变而改变它的相关行为。
+在代码中包含大量与对象状态有关的条件语句时应该考虑使用状态模式。应当注意的是，在行为受状态约束的时候使用状态模式，状态应该不超过5个，太多则导致程序结构、代码混乱。</li>
+<li>行为随状态改变而改变的场景。</li>
+<li>条件、分支语句的代替者。</li>
+</ul>
+<h3 id="策略模式">策略模式</h3>
+<p>策略模式，定义一系列算法类，将每一个算法封装起来，并让它们可以相互替换，策略模式让算法独立于使用它的客户而变化，也称为政策模式。策略模式是一种对象行为型模式。
+策略模式的主要目的是将算法的定义与使用分开，也就是将算法的行为和环境分开，将算法的定义放在专门的策略类中，每一个策略类封装了一种实现算法，使用算法的环境类针对抽象策略类进行编程，符合“依赖倒转原则”。
+在出现新的算法时，只需要增加一个新的实现了抽象策略类的具体策略类即可。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Bird</span><span class="w"> </span><span class="n">bird</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Bird</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bird</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Duck</span><span class="w"> </span><span class="n">duck</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Duck</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">duck</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Dog</span><span class="w"> </span><span class="n">dog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dog</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;变为会飞 ：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dog</span><span class="p">.</span><span class="na">setFlyStrategy</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">GoodFlyStrategy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dog</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">FlyStrategy</span><span class="w"> </span><span class="n">flyStrategy</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setFlyStrategy</span><span class="p">(</span><span class="n">FlyStrategy</span><span class="w"> </span><span class="n">flyStrategy</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">flyStrategy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">flyStrategy</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Bird</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractStrategy</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Bird</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;小鸟&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">GoodFlyStrategy</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Duck</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Duck</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;鸭子&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BadFlyStrategy</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Dog</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;狗&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NoFlyStrategy</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">FlyStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">GoodFlyStrategy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FlyStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;擅长飞翔 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BadFlyStrategy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FlyStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不擅长飞翔 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">NoFlyStrategy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FlyStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不会飞 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>策略模式用于算法的自由切换和扩展，它是应用较为广泛的设计模式之一。策略模式对应于解决某一问题的一个算法族，允许用户从该算法族中任选一个算法来解决某一问题，同时可以方便地更换算法或者增加新的算法。
+只要涉及到算法的封装、复用和切换都可以考虑使用策略模式。如果一个系统的策略多于四个，就需要考虑使用混合模式，解决策略类膨胀的问题。</p>
+<p>优点：</p>
+<ul>
+<li>策略模式提供了对“开闭原则”的完美支持，用户可以在不修改原有系统的基础上选择算法或行为，也可以灵活地增加新的算法或行为。</li>
+<li>策略模式提供了管理相关的算法族的办法。策略类的等级结构定义了一个算法或行为族，恰当使用继承可以把公共的代码移到抽象策略类中，从而避免重复的代码。</li>
+<li>策略模式提供了一种算法的复用机制，由于将算法单独提取出来封装在策略类中，因此不同的环境类可以方便地复用这些策略类。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>客户端必须知道所有的策略类，并自行决定使用哪一个策略类。这就意味着客户端必须理解这些算法的区别，以便适时选择恰当的算法。
+换言之，策略模式只适用于客户端知道所有的算法或行为的情况。</li>
+<li>所有策略类都需要对外暴露。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>一个系统有许多许多类，而区分它们的只是他们直接的行为，那么使用策略模式可以动态地让一个对象在许多行为中选择一种行为。</li>
+<li>如果一个对象有很多的行为，如果不用恰当的模式，这些行为就只好使用多重的条件选择语句来实现。</li>
+</ul>
+<h3 id="模板方法模式">模板方法模式</h3>
+<p>模板方法模式，定义一个操作中的算法骨架，而将算法的一些步骤延迟到子类中，使得子类可以不改变该算法结构的情况下重定义该算法的某些特定步骤。
+模板方法模式是一种基于继承的代码复用技术，它是一种类行为型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====红豆豆浆=====&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RedBean</span><span class="w"> </span><span class="n">redBean</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RedBean</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">redBean</span><span class="p">.</span><span class="na">template</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====花生豆浆=====&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Peanut</span><span class="w"> </span><span class="n">peanut</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Peanut</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">peanut</span><span class="p">.</span><span class="na">template</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====豆浆=====&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">None</span><span class="w"> </span><span class="n">none</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">None</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">none</span><span class="p">.</span><span class="na">template</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SoyaMilk</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">template</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">filterMaterial</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">soak</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isAppended</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">add</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">over</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">filterMaterial</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第一步：筛选材料&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">soak</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第二步：浸泡&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">over</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第四步：打豆浆&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 钩子方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isAppended</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Peanut</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SoyaMilk</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第三步：加入花生&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RedBean</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SoyaMilk</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第三步：加入红豆&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">None</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SoyaMilk</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isAppended</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>模板方法模式是基于继承的代码复用技术，它体现了面向对象的诸多重要思想，是一种使用较为频繁的模式。
+模板方法模式广泛应用于框架设计中，以确保通过父类来控制处理流程的逻辑顺序（如框架的初始化，测试流程的设置等）。</p>
+<p>优点：</p>
+<ul>
+<li>它封装了不变部分，扩展可变部分。它把认为是不变部分的算法封装到父类中实现，而把可变部分算法由子类继承实现，便于子类继续扩展。</li>
+<li>它在父类中提取了公共的部分代码，便于代码复用。</li>
+<li>部分方法是由子类实现的，因此子类可以通过扩展方式增加相应的功能，符合开闭原则。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>需要为每一个基本方法的不同实现提供一个子类，如果父类中可变的基本方法太多，将会导致类的个数增加，系统更加庞大，设计也更加抽象，间接地增加了系统实现的复杂度。此时，可结合桥接模式来进行设计。</li>
+<li>由于继承关系自身的缺点，如果父类添加新的抽象方法，则所有子类都要改一遍。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>算法的整体步骤很固定，但其中个别部分易变时，这时候可以使用模板方法模式，将容易变的部分抽象出来，供子类实现。</li>
+<li>当多个子类存在公共的行为时，可以将其提取出来并集中到一个公共父类中以避免代码重复。首先，要识别现有代码中的不同之处，并且将不同之处分离为新的操作。最后，用一个调用这些新的操作的模板方法来替换这些不同的代码。</li>
+<li>当需要控制子类的扩展时，模板方法只在特定点调用钩子操作，这样就只允许在这些点进行扩展。</li>
+</ul>
+<h3 id="访问者模式">访问者模式</h3>
+<p>访问者模式，提供一个作用于某对象结构中的各元素的操作表示，它使我们可以在不改变各元素的类的前提下定义作用于这些元素的新操作。访问者模式是一种对象行为型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectStructure</span><span class="w"> </span><span class="n">objectStructure</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectStructure</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">attach</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Man</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">attach</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">WoMan</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">attach</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Man</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">attach</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">WoMan</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示成功的评价</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Success</span><span class="w"> </span><span class="n">success</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Success</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">display</span><span class="p">(</span><span class="n">success</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示失败的评价</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Fail</span><span class="w"> </span><span class="n">fail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Fail</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">display</span><span class="p">(</span><span class="n">fail</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Action</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getManResult</span><span class="p">(</span><span class="n">Man</span><span class="w"> </span><span class="n">man</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getWomanResult</span><span class="p">(</span><span class="n">WoMan</span><span class="w"> </span><span class="n">woman</span><span class="w"> </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Success</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Action</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getManResult</span><span class="p">(</span><span class="n">Man</span><span class="w"> </span><span class="n">man</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;男人觉得很赞～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getWomanResult</span><span class="p">(</span><span class="n">WoMan</span><span class="w"> </span><span class="n">woman</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;女人觉得很赞～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Fail</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Action</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getManResult</span><span class="p">(</span><span class="n">Man</span><span class="w"> </span><span class="n">man</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;男人觉得很失败～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getWomanResult</span><span class="p">(</span><span class="n">WoMan</span><span class="w"> </span><span class="n">woman</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;女人觉得很失败～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span>  <span class="nc">Person</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">accpet</span><span class="p">(</span><span class="n">Action</span><span class="w"> </span><span class="n">action</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">WoMan</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Person</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">accpet</span><span class="p">(</span><span class="n">Action</span><span class="w"> </span><span class="n">action</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">action</span><span class="p">.</span><span class="na">getWomanResult</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Man</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Person</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">accpet</span><span class="p">(</span><span class="n">Action</span><span class="w"> </span><span class="n">action</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">action</span><span class="p">.</span><span class="na">getManResult</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ObjectStructure</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">people</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">attach</span><span class="p">(</span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">people</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">detach</span><span class="p">(</span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">people</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">(</span><span class="n">Action</span><span class="w"> </span><span class="n">acion</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">people</span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">item</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">item</span><span class="p">.</span><span class="na">accpet</span><span class="p">(</span><span class="n">acion</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>由于访问者模式的使用条件较为苛刻，本身结构也较为复杂，因此在实际应用中使用频率不是特别高。
+当系统中存在一个较为复杂的对象结构，且不同访问者对其所采取的操作也不相同时，可以考虑使用访问者模式进行设计。
+在XML文档解析、编译器的设计、复杂集合对象的处理等领域访问者模式得到了一定的应用。</p>
+<p>优点：</p>
+<ul>
+<li>扩展性好。增加新的访问操作很方便。使用访问者模式，增加新的访问操作就意味着增加一个新的具体访问者类，实现简单，无须修改源代码，符合“开闭原则”。</li>
+<li>复用性好。可以通过访问者来定义整个对象结构通用的功能，从而提高系统的复用程度。</li>
+<li>灵活性好。访问者模式将数据结构与作用于结构上的操作解耦，使得操作集合可相对自由地演化而不影响系统的数据结构。</li>
+<li>符合单一职责原则单一职责原则。访问者模式把相关的行为封装在一起，构成一个访问者，使每一个访问者的功能都比较单一。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>破坏封装。访问者模式中具体元素对访问者公布细节，这破坏了对象的封装性。具体元素对访问者公布细节，违反了迪米特法则。</li>
+<li>违反了依赖倒置原则依赖倒置原则。访问者模式依赖了具体类，而没有依赖抽象类。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>需要对一个对象结构中的对象进行很多不同的并且不相关的操作，而需要避免让这些操作&quot;污染&quot;这些对象的类，使用访问者模式将这些封装到类中。访问者可以对功能进行统一，可以做报表、UI、拦截器与过滤器。</li>
+<li>对象结构中对象对应的类很少改变，但经常需要在此对象结构上定义新的操作。</li>
+<li>需要对一个对象结构中的对象进行很多不同的并且不相关的操作，而需要避免让这些操作&quot;污染&quot;这些对象的类，也不希望在增加新操作时修改这些类。</li>
+</ul>
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\ No newline at end of file
diff --git a/blog-site/public/posts/javabasics/rookie-objectclass-methods/index.html b/blog-site/public/posts/javabasics/rookie-objectclass-methods/index.html
new file mode 100644
index 00000000..e19606de
--- /dev/null
+++ b/blog-site/public/posts/javabasics/rookie-objectclass-methods/index.html
@@ -0,0 +1,1650 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>JavaObject类方法 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="概览 Object类位于java.lang包中，编译时会自动导入。当我们创建一个类时，如果没有明确继承一个父类，那么它就会自动继承Object，成为Object的" />
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+    <div class="post-password">
+        
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+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%a7%88">
+                    概览
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#equals">
+                    equals
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ad%89%e4%bb%b7%e5%85%b3%e7%b3%bb">
+                    等价关系
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%8e%e5%8f%8c%e7%ad%89%e5%8f%b7">
+                    与双等号
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8d%e5%86%99equals%e6%96%b9%e6%b3%95">
+                    重写equals方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashcode">
+                    hashCode
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%94%af%e4%b8%80%e6%80%a7">
+                    唯一性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashcode%e4%b8%8eequals">
+                    hashCode与equals
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8d%e5%86%99hashcode%e6%96%b9%e6%b3%95">
+                    重写hashCode方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#tostring">
+                    toString
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8d%e5%86%99tostring%e6%96%b9%e6%b3%95">
+                    重写toString方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8tostring">
+                    使用toString
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#clone">
+                    clone
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cloneable%e6%8e%a5%e5%8f%a3">
+                    Cloneable接口
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b5%85%e6%8b%b7%e8%b4%9d%e4%b8%8e%e6%b7%b1%e6%8b%b7%e8%b4%9d">
+                    浅拷贝与深拷贝
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#clone%e7%9a%84%e6%9b%bf%e4%bb%a3">
+                    clone的替代
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#finalize">
+                    finalize
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#getclass">
+                    getClass
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
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+                        <h2 id="post_single_title">JavaObject类方法</h2>
+                        <span id="post_page_title_date" class="date">2021.07.10</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p><code>Object</code>类位于<code>java.lang</code>包中，编译时会自动导入。当我们创建一个类时，如果没有明确继承一个父类，那么它就会自动继承<code>Object</code>，成为<code>Object</code>的子类。
+<code>Object</code>类可以显示继承，也可以隐式继承，效果都是一样的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Object</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// to do</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// to do</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>Java<code>Object</code>类是所有类的父类，也就是说Java的所有类都继承了<code>Object</code>。因此，<code>Object</code>类提供了一组通用的方法，这些方法可以在所有Java对象上调用。</p>
+<table>
+<thead>
+<tr>
+<th>方法名称</th>
+<th>方法作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>equals</td>
+<td>比较两个对象是否相同</td>
+</tr>
+<tr>
+<td>hashCode</td>
+<td>获取对象的哈希值</td>
+</tr>
+<tr>
+<td>toString</td>
+<td>返回对象的字符串表示形式</td>
+</tr>
+<tr>
+<td>clone</td>
+<td>创建并返回一个对象的拷贝</td>
+</tr>
+<tr>
+<td>finalize</td>
+<td>当垃圾收集确定不再有对对象的引用时，由垃圾收集器在对象上调用</td>
+</tr>
+<tr>
+<td>getClass</td>
+<td>获取对象运行时的类</td>
+</tr>
+<tr>
+<td>notify</td>
+<td>唤醒在该对象上等待的某个线程</td>
+</tr>
+<tr>
+<td>notifyAll</td>
+<td>唤醒在该对象上等待的所有线程</td>
+</tr>
+<tr>
+<td>wait</td>
+<td>让当前线程进入等待(阻塞)状态。直到其他线程调用此对象的<code>notify()</code>方法或<code>notifyAll()</code>方法。</td>
+</tr>
+</tbody>
+</table>
+<h2 id="equals">equals</h2>
+<p><code>equals</code>方法是Java中的一个重要方法，用于比较两个对象是否相等。默认情况下，<code>Object</code>类中的<code>equals</code>方法比较的是对象的内存地址，但许多类会重写这个方法以实现自定义的比较逻辑。
+<code>Object</code>类中的<code>equals()</code>源码如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>该实现只是简单地比较两个对象的引用是否相同，即是否指向同一个内存地址。</p>
+<h3 id="等价关系">等价关系</h3>
+<p>在Java中，<code>equals</code>方法用于确定两个对象是否相等。为了正确实现这个方法，必须确保它满足等价关系的要求。等价关系是一种自反的、对称的和传递的关系。
+具体来说，<code>equals</code>方法必须遵循以下规则：</p>
+<ul>
+<li>自反性：对于任何非<code>null</code>的引用值<code>x</code>，<code>x.equals(x)</code>必须返回<code>true</code>。</li>
+<li>对称性：对于任何非<code>null</code>的引用值<code>x</code>和<code>y</code>，如果<code>x.equals(y)</code>返回<code>true</code>，那么<code>y.equals(x)</code>也必须返回<code>true</code>。</li>
+<li>传递性：对于任何非<code>null</code>的引用值<code>x</code>、<code>y</code>和<code>z</code>，如果<code>x.equals(y)</code>返回<code>true</code>，并且<code>y.equals(z)</code>返回<code>true</code>，那么<code>x.equals(z)</code>也必须返回<code>true</code>。</li>
+<li>一致性：对于任何非<code>null</code>的引用值<code>x</code>和<code>y</code>，只要对象的状态没有改变，多次调用<code>x.equals(y)</code>应当返回相同的结果。</li>
+<li>非空性：对于任何非<code>null</code>的引用值<code>x</code>，<code>x.equals(null)</code>必须返回<code>false</code>。</li>
+</ul>
+<h3 id="与双等号">与双等号</h3>
+<p>对于基本类型，<code>==</code>判断两个值是否相等，基本类型没有<code>equals()</code>方法。对于引用类型，<code>==</code>判断两个变量是否引用同一个对象，而<code>equals()</code>判断引用的对象是否等价。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Integer x = new Integer(1);
+</span></span><span class="line"><span class="cl">Integer y = new Integer(1);
+</span></span><span class="line"><span class="cl">System.out.println(x.equals(y)); // true
+</span></span><span class="line"><span class="cl">System.out.println(x == y);      // false
+</span></span></code></pre></div><p><code>equals()</code>作用是判断两个对象是否相等，但一般有两种情况：</p>
+<ol>
+<li>类没有覆盖<code>equals</code>方法，则相当于通过 <code>==</code>来比较这两个对象的地址；</li>
+<li>类覆盖<code>equals</code>方法，一般我们通过<code>equals()</code>来比较两个对象的内容是否相等，相等则返回<code>true</code>；</li>
+</ol>
+<p>之前有一道经典的面试题，问的就是<code>==</code>和<code>equals</code>的区别。
+<code>==</code>运算符比较两个引用是否指向同一个对象。
+<code>equals</code>方法比较两个对象的内容是否相等。默认情况下，<code>Object</code>类中的<code>equals</code>方法比较的是对象的内存地址，但许多类会重写这个方法以比较对象的内容。</p>
+<h3 id="重写equals方法">重写equals方法</h3>
+<p><code>equals()</code>在不重写的情况下与<code>==</code>作用一样，都是比较的内存中的地址，但是<code>equals()</code>可以重写。
+重写<code>equals</code>方法的目的是为了定义对象内容相等的逻辑。默认的<code>equals</code>方法比较内存地址，而我们通常需要比较对象的内容。
+重写<code>equals</code>方法一般思路：</p>
+<ol>
+<li>检查是否为同一个对象的引用，如果是直接返回<code>true</code>；</li>
+<li>检查是否是同一个类型，如果不是，直接返回<code>false</code>；</li>
+<li>将<code>Object</code>对象进行转型；</li>
+<li>判断每个关键域是否相等；</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">EqualExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">z</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">o</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">o</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">o</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">getClass</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">o</span><span class="p">.</span><span class="na">getClass</span><span class="p">())</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">that</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">EqualExample</span><span class="p">)</span><span class="w"> </span><span class="n">o</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">that</span><span class="p">.</span><span class="na">x</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">y</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">that</span><span class="p">.</span><span class="na">y</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">z</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">that</span><span class="p">.</span><span class="na">z</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="hashcode">hashCode</h2>
+<p>在Java中<code>hashcode</code>方法是<code>Object</code>类的<code>native</code>方法，返回值为int类型，根据一定的规则将与对象相关的信息，如对象的存储地址，对象的字段等，映射成一个数值，这个数值称作为<code>hash</code>值。
+<code>hashCode</code>方法在Java中非常重要，尤其在使用哈希表（如<code>HashMap</code>、<code>HashSet</code>等）时。<code>hashCode</code>方法返回一个整数，该整数称为对象的哈希码。这个哈希码用于确定对象在哈希表中的存储位置。</p>
+<p>为了使<code>hashCode</code>方法正确工作，并确保在集合中对象的行为正确，必须遵循以下约定：</p>
+<ul>
+<li>如果两个对象不相等，它们的哈希码不一定要不同。但是不相等的对象产生不同哈希码，总体上呈均匀分布，可以提高哈希表的性能。</li>
+<li>在程序的同一执行过程中，只要对象的信息没有被修改，多次调用<code>hashCode</code>方法应该返回相同的整数。</li>
+<li>如果根据<code>equals</code>方法，两个对象是相等的，那么调用这两个对象的<code>hashCode</code>方法必须返回相同的整数。</li>
+</ul>
+<p><code>hashCode</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">hashCode</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>根据这个方法的声明可知，该方法返回一个<code>int</code>类型的数值，并且是本地方法，因此在<code>Object</code>类中并没有给出具体的实现。</p>
+<h3 id="唯一性">唯一性</h3>
+<p>对于包含容器类型的程序设计语言来说，基本上都会涉及到<code>hashCode</code>。
+在Java中也一样，<code>hashCode</code>方法的主要作用是为了配合基于散列的集合一起正常运行，这样的散列集合包括<code>HashSet、HashMap</code>以及<code>HashTable</code>。</p>
+<p>在集合中已经存在上万条数据或更多的数据场景下向集合中插入对象时，如何判别在集合中是否已经存在该对象了？</p>
+<p>如果采用<code>equals</code>方法去逐一比较，效率必然是一个问题，此时<code>hashCode</code>方法的优点就体现出来了。
+因为两个不同的对象可能会有相同的<code>hashCode</code>值，所有不能通过<code>hashCode</code>值来判断两个对象是否相等，但是可以直接根据<code>hashcode</code>值判断两个对象不等，如果两个对象的<code>hashCode</code>值不等，则必定是两个不同的对象。
+当集合要添加新的对象时，先调用这个对象的<code>hashCode</code>方法，得到对应的<code>hashcode</code>值，如果存放的<code>hash</code>值中没有该<code>hashcode</code>值，它就可以直接存进去，不用再进行任何比较了。
+如果存在该<code>hashcode</code>值，就调用它的<code>equals</code>方法与新元素进行比较，相同的话就不存了，不相同就去存。</p>
+<p>需要额外注意的是，设计<code>hashCode</code>方法时最重要的因素就是，无论何时，对同一个对象调用<code>hashCode()</code>都应该产生同样的值。
+如果在将一个对象用<code>put()</code>添加进<code>HashMap</code>时产生一个<code>hashCdoe</code>值，而用<code>get()</code>取出时却产生了另一个<code>hashCode</code>值，那么就无法获取该对象了。
+所以如果你的<code>hashCode</code>方法依赖于对象中易变的数据，就要当心了，因为此数据发生变化时，<code>hashCode()</code>方法就会生成一个不同的散列码，从而获取不到该对象。
+所以在重写<code>hashCode</code>方法和<code>equals</code>方法的时候，如果对象中的数据易变，则最好在<code>equals</code>方法和<code>hashCode</code>方法中不要依赖于该字段。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Person</span><span class="w"> </span><span class="n">p1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Person</span><span class="p">(</span><span class="s">&#34;lucy&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">22</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 85134311</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">hashCode</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">Person</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">p1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">p1</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="n">13</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// null</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">hashMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Person</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Person</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAge</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">hashCode</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">.</span><span class="na">hashCode</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">37</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">.</span><span class="na">equals</span><span class="p">(((</span><span class="n">Person</span><span class="p">)</span><span class="w"> </span><span class="n">obj</span><span class="p">).</span><span class="na">name</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p">((</span><span class="n">Person</span><span class="p">)</span><span class="w"> </span><span class="n">obj</span><span class="p">).</span><span class="na">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hashcode与equals">hashCode与equals</h3>
+<p><code>hashCode()</code>返回散列值，而<code>equals()</code>是用来判断两个对象是否等价。等价的两个对象散列值一定相同，但是散列值相同的两个对象不一定等价。
+<code>equals()</code>地址比较是通过对象的哈希值来比较的。<code>hash</code>值是由<code>hashCode</code>方法产生的，<code>hashCode</code>属于<code>Object</code>类的本地方法，默认使用<code>==</code>比较两个对象。
+如果<code>equals()</code>相等<code>，hashcode</code>一定相等，如果<code>hashcode</code>相等，<code>equals</code>不一定相等。所以在覆盖<code>equals</code>方法时应当总是覆盖<code>hashCode</code>方法，保证等价的两个对象散列值也相等。</p>
+<p>下面的代码中，新建了两个等价的对象，并将它们添加到<code>HashSet</code>中。
+我们希望将这两个对象当成一样的，只在集合中添加一个对象，但是因为<code>EqualExample</code>没有实现<code>hashCode()</code>方法，因此这两个对象的散列值是不同的，最终导致集合添加了两个等价的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">e1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EqualExample</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">e2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EqualExample</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e1</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">e2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">EqualExample</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">e1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">e2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">set</span><span class="p">.</span><span class="na">size</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>所以在覆盖 <code>equals()</code>方法时应当总是覆盖<code>hashCode</code>方法，保证等价的两个对象散列值也相等。</p>
+<h3 id="重写hashcode方法">重写hashCode方法</h3>
+<p>重写<code>hashCode</code>方法规则：</p>
+<ul>
+<li>把某个非零的常数值，保存在一个名为<code>result</code>的int类型的常量中；</li>
+<li>字段值哈希码的计算：
+<ul>
+<li>如果是<code>boolean</code>类型，<code>true</code>为1，<code>false</code>则为0；</li>
+<li>如果是<code>byte、char、short</code>和<code>int</code>类型，需要强制转为int的值；</li>
+<li>如果是<code>long</code>类型，计算<code>(int)(f^(f&gt;&gt;32))</code>；</li>
+<li>如果是<code>float</code>类型，计算<code>Float.floatToIntBits(f)</code>；</li>
+<li>如果是<code>double</code>类型，计算<code>Double.doubleToLongBits(f)</code>，再按照<code>long</code>的方法进行计算；</li>
+<li>如果是引用类型，则调用其<code>hashCode</code>方法，假设其<code>hashCode</code>满足你的需求；</li>
+</ul>
+</li>
+<li>代入公式<code>result = result * 31 + c</code>，返回<code>result</code>；</li>
+</ul>
+<p>《Effective Java》的作者推荐使用基于17和31的散列码的算法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">hashCode</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">17</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">31</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">31</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">31</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">z</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>Java7新增的<code>Objects</code>类提供了计算<code>hashCode</code>的通用方法，可以很简洁实现<code>hashCode</code>方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">hashCode</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">Objects</span><span class="p">.</span><span class="na">hash</span><span class="p">(</span><span class="n">name</span><span class="p">,</span><span class="n">age</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>现在比较流行的写法是用<code>Lombok</code>，在类上使用<code>@EqualsAndHashCode</code>注解：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@EqualsAndHashCode</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Person</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构造方法、getter、setter等略</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="tostring">toString</h2>
+<p><code>toString</code>方法是<code>Object</code>类里定义的，默认返回类名和它的引用地址，即<code>ToStringExample@4554617c</code>这种形式。其中@后面的数值为散列码的无符号十六进制表示。
+通常情况下，<code>toString</code>方法返回一个字符串，该字符串包含对象的状态信息，便于调试和日志记录。<code>Object</code>类<code>toString</code>源代码如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">getClass</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;@&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">toHexString</span><span class="p">(</span><span class="n">hashCode</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="重写tostring方法">重写toString方法</h3>
+<p>当我们打印一个对象的引用时，实际是默认调用这个对象的<code>toString</code>方法。
+当打印的对象所在类没有重写<code>Object</code>中的<code>toString()</code>方法时，默认调用的是<code>Object</code>类中<code>toString()</code>方法，返回此对象所在的类及对应的堆空间对象实体的首地址值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// object.ToStringDemo@511d50c0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ToStringDemo</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ToStringDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>当我们打印对象所在类重写了<code>toString()</code>，调用的就是已经重写了的<code>toString</code>方法，一般重写是将类对象的属性信息返回。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ToStringDemo</span><span class="w"> </span><span class="n">toStringDemo</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ToStringDemo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">toStringDemo</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;lucy&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ToStringDemo{name=&#39;lucy&#39;}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">toStringDemo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ToStringDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;ToStringDemo{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="使用tostring">使用toString</h3>
+<p>一般情况下，使用<code>toString</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// object.ToStringDemo@511d50c0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ToStringDemo</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>还有有一种隐式的调用方法，当你将一个对象与字符串进行拼接操作时，如果对象不是字符串类型，Java会自动调用该对象的<code>toString</code>方法来获取其字符串表示形式，然后再与其他字符串拼接起来。
+这种行为可以让代码更加简洁和易读，而不需要显式调用<code>toString</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Date</span><span class="w"> </span><span class="n">time</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;time = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">time</span><span class="p">);</span><span class="c1">//相当于下一行代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;time = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">time</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>基本数据类型转换为<code>String</code>类型也是调用了对应包装类的<code>toString</code>方法，如<code>Integer</code>、<code>Double</code>等。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int i = 10;
+</span></span><span class="line"><span class="cl">System.out.println(&#34;i=&#34; + i);
+</span></span></code></pre></div><h2 id="clone">clone</h2>
+<p>在Java中可以使用<code>clone</code>方法用于创建并返回一个对象的副本，对象克隆指的是创建一个新的对象，新对象的内容与原始对象相同。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>要在自定义类中实现对象的克隆，需要执行以下步骤：</p>
+<ul>
+<li>实现<code>Cloneable</code>接口，这是一个标记接口，自身没有方法；</li>
+<li>覆盖重写<code>clone</code>方法，可见性提升为<code>public</code>；</li>
+</ul>
+<h3 id="cloneable接口">Cloneable接口</h3>
+<p><code>Cloneable</code>接口是Java开发中常用的一个接口，它是一个标记接口。
+如果一个想要拷贝一个对象，就需要重写<code>Object</code>中的<code>clone</code>方法并让其实现<code>Cloneable</code>接口。如果只重写<code>clone</code>方法，不实现<code>Cloneable</code>接口就会报<code>CloneNotSupportedException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>应当注意的是，<code>clone</code>方法并不是<code>Cloneable</code>接口的方法，而是<code>Object</code>的一个<code>protected</code>方法。
+<code>Cloneable</code>接口只是规定，如果一个类没有实现<code>Cloneable</code>接口又调用了<code>clone</code>方法，就会抛出<code>CloneNotSupportedException</code>。
+换言之，<code>clone</code>方法规定了想要拷贝对象，就需要实现<code>Cloneable</code>方法，<code>clone</code>方法让<code>Cloneable</code>接口变得有意义。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CloneExample</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="浅拷贝与深拷贝">浅拷贝与深拷贝</h3>
+<p>拷贝分为浅拷贝与深拷贝：</p>
+<ul>
+<li>浅拷贝：被复制对象的所有值属性都含有与原来对象的相同，而所有的对象引用属性仍然指向原来的对象；</li>
+<li>深拷贝：在浅拷贝的基础上，所有引用其他对象的变量也进行了<code>clone</code>，并指向被复制过的新对象；</li>
+</ul>
+<p>如果一个被复制的属性都是基本类型，那么只需要实现当前类的<code>Cloneable</code>机制就可以了，此为浅拷贝。
+如果被复制对象的属性包含其他实体类对象引用，那么这些实体类对象都需要实现<code>Cloneable</code>接口并覆盖<code>clone</code>方法。</p>
+<ul>
+<li>浅拷贝创建一个新对象，这个新对象的字段内容与原对象相同，但如果字段是引用类型（比如数组、对象），浅拷贝只复制引用地址，不复制引用的实际对象。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyObject</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">MyObject</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w"> </span><span class="c1">// 浅拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">MyObject</span><span class="w"> </span><span class="n">original</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">(</span><span class="n">42</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">MyObject</span><span class="w"> </span><span class="n">copy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">MyObject</span><span class="p">)</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">original</span><span class="p">.</span><span class="na">array</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">99</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">copy</span><span class="p">.</span><span class="na">array</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 99</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>深拷贝创建一个新对象，这个新对象和原对象完全独立，包括复制所有引用类型字段的实际对象，而不仅仅是引用地址。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyObject</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">MyObject</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">MyObject</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arrayCopy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w"> </span><span class="c1">// 复制数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">(</span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="n">arrayCopy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">MyObject</span><span class="w"> </span><span class="n">original</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">(</span><span class="n">42</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">MyObject</span><span class="w"> </span><span class="n">copy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">original</span><span class="p">.</span><span class="na">array</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">99</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">copy</span><span class="p">.</span><span class="na">array</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="clone的替代">clone的替代</h3>
+<p>虽然<code>Cloneable</code>和<code>clone()</code>方法在Java中是标准的浅拷贝方式，但它们在实际开发中不太常用。主要是因为使用<code>clone()</code>方法来拷贝一个对象即复杂又有风险，它会抛出异常，并且还需要类型转换。
+《Effective Java》 书上讲到，最好不要去使用 <code>clone()</code>，可以使用拷贝构造函数或者拷贝工厂来拷贝一个对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CloneConstructorExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneConstructorExample</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneConstructorExample</span><span class="p">(</span><span class="n">CloneConstructorExample</span><span class="w"> </span><span class="n">original</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">original</span><span class="p">.</span><span class="na">arr</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">set</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">get</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">CloneConstructorExample e1 = new CloneConstructorExample();
+</span></span><span class="line"><span class="cl">CloneConstructorExample e2 = new CloneConstructorExample(e1);
+</span></span><span class="line"><span class="cl">e1.set(2, 222);
+</span></span><span class="line"><span class="cl">System.out.println(e2.get(2)); // 2
+</span></span></code></pre></div><h2 id="finalize">finalize</h2>
+<p><code>finalize</code>方法是Java提供的对象终止机制，允许开发人员提供对象被销毁之前的自定义处理逻辑。
+当垃圾回收器发现没有引用指向一个对象，即垃圾回收此对象之前，总会先调用这个对象的<code>finalize</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Called by the garbage collector on an object when garbage collection
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * determines that there are no more references to the object.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * A subclass overrides the {@code finalize} method to dispose of
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * system resources or to perform other cleanup.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finalize</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>文档注释大意：当GC确定不再有对对象的引用时，由垃圾收集器在对象上调用。子类重写<code>finalize</code>方法来释放系统资源或执行其他清理。</p>
+<p>简而言之，<code>finalize</code>方法是与Java中的垃圾回收器有关系。当一个对象变成一个垃圾对象的时候，如果此对象的内存被回收，那么就会调用该类中定义的<code>finalize</code>方法。
+当一个对象可被回收时，就需要执行该对象的<code>finalize</code>方法，那么就有可能在该方法中让对象重新被引用，从而实现自救。自救只能进行一次，如果回收的对象之前调用了<code>finalize</code>方法自救，后面回收时不会再调用该方法。</p>
+<p><code>finalize</code>方法允许在子类中被重写，用于在对象被回收时进行资源释放。
+通常在这个方法中进行一些资源释放和清理的工作，比如关闭文件、套接字和数据库连接等。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finalize</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 执行清理操作，比如关闭文件或释放资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Finalize method called&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">super</span><span class="p">.</span><span class="na">finalize</span><span class="p">();</span><span class="w"> </span><span class="c1">// 确保调用超类的 finalize 方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>尽管<code>finalize</code>可以被用来释放资源，但在实际开发中已经被认为是不可靠和过时的方式。永远不要主动调用某个对象的<code>finalize</code>方法，应该交给垃圾回收机制调用的原因：</p>
+<ul>
+<li>在调用<code>finalize</code>方法时时可能会导致对象复活；</li>
+<li><code>finalize</code>方法的执行时间是没有保障的，它完全由GC线程决定，极端情况下，若不发生GC，则<code>finalize</code>方法将没有执行机会。
+因为优先级比较低，即使主动调用该方法，也不会因此就直接进行回收；</li>
+<li>一个糟糕的<code>finalize</code>方法会严重影响GC的性能；</li>
+</ul>
+<p>如果从所有的根节点都无法访问到某个对象，说明对象己经不再使用了，一般来说，此对象需要被回收。
+但事实上，也并非是“非死不可”的，这时候它们暂时处于“缓刑”阶段。一个无法触及的对象有可能在某一个条件下“复活”自己，如果这样那么对它的回收就是不合理的，为此虚拟机中定义了的对象可能的三种状态：</p>
+<ul>
+<li>可触及的：从根节点开始，可以到达这个对象；对象存活被使用；</li>
+<li>可复活的：对象的所有引用都被释放，但是对象有可能在<code>finalize</code>中复活；对象被复活，对象在<code>finalize</code>方法中被重新使用；</li>
+<li>不可触及的：对象的<code>finalize</code>方法被调用，并且没有复活，那么就会进入不可触及状态；对象死亡、对象没有被使用；</li>
+</ul>
+<p>只有在对象不可触及时才可以被回收，不可触及的对象不可能被复活，因为<code>finalize</code>只会被调用一次。
+判定一个对象是否可回收，至少要经历两次标记过程：</p>
+<ul>
+<li>如果对象没有没有引用链，则进行第一次标记；</li>
+<li>进行筛选，判断此对象是否有必要执行<code>finalize</code>方法；
+<ol>
+<li>如果对象没有重写<code>finalize</code>方法，或者<code>finalize</code>方法已经被虚拟机调用过，则虚拟机视为“没有必要执行”，对象被判定为不可触及的。</li>
+<li>如果对象重写了<code>finalize</code>方法，且还未执行过，那么会被插入到<code>F-Queue</code>队列中，由一个虚拟机自动创建的、低优先级的<code>Finalizer</code>线程触发其<code>finalize</code>方法执行。</li>
+<li><code>finalize</code>方法是对象逃脱死亡的最后机会，稍后GC会对<code>F-Queue</code>队列中的对象进行第二次标记。如果对象在<code>finalize</code>方法中与引用链上的任何一个对象建立了联系，那么在第二次标记时，该对象会被移出“即将回收”集合。
+之后对象会再次出现没有引用存在的情况。在这个情况下，<code>finalize</code>方法不会被再次调用，对象会直接变成不可触及的状态，也就是说，一个对象的<code>finalize</code>方法只会被调用一次。</li>
+</ol>
+</li>
+</ul>
+<p>代码演示对象能否被回收：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">MainTest</span><span class="w"> </span><span class="n">var</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 此方法只能被调用一次
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 可对该方法进行注释，来测试finalize方法是否能复活对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finalize</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;调用当前类重写的finalize()方法&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 复活对象 让当前带回收对象重新与引用链中的对象建立联系</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">new</span><span class="w"> </span><span class="n">MainTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">gc</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;-----------------第一次gc操作------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 因为Finalizer线程的优先级比较低，暂停2秒，以等待它</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">2000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kd">var</span><span class="w"> </span><span class="err">== </span><span class="n">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;对象已经死了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 如果第一次对象就死亡了 就终止</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;对象还活着&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;-----------------第二次gc操作------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">gc</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 下面代码和上面代码是一样的，但是 对象却自救失败了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">2000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kd">var</span><span class="w"> </span><span class="err">== </span><span class="n">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;对象已经死了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;对象还活着&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="getclass">getClass</h2>
+<p><code>getClass</code>方法是Java中的一个重要方法，它用于返回对象的运行时类。这个方法定义在<code>java.lang.Object</code>类中，因此每个Java对象都可以调用它。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Returns the runtime class of this {@code Object}. The returned
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * {@code Class} object is the object that is locked by {@code
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * static synchronized} methods of the represented class.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">getClass</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>文档大意：返回这个对象的运行时类，返回的<code>Class</code>对象是被表示类的<code>static synchronized</code>方法锁定的对象。</p>
+<p><code>getClass</code>方法返回对象运行时的类，返回的类型是<code>Class</code>类型的对象。可以通过这个<code>Class</code>对象来创建调用这个方法的对象和执行一些其他操作，这便是反射的入口。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello, World!&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">getClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">clazz</span><span class="p">.</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;substring&#34;</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">str</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">12</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w"> </span><span class="c1">// Output: World</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在某些情况下，需要比较两个对象是否属于同一类型。通过<code>getClass</code>方法可以方便地进行类型比较。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;World&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">42</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">str1</span><span class="p">.</span><span class="na">getClass</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str2</span><span class="p">.</span><span class="na">getClass</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;str1 and str2 are of the same type.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">str1</span><span class="p">.</span><span class="na">getClass</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">num</span><span class="p">.</span><span class="na">getClass</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;str1 and num are of different types.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="notify">notify</h2>
+<p><code>notify</code>方法用于唤醒在该对象监视器上等待的一个线程。如果有多个线程在该对象上等待，具体唤醒哪一个线程是由线程调度器决定的，并且是不确定的。
+被唤醒的线程将继续执行，从调用<code>wait</code>方法的地方开始。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">notify</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p><code>notify</code>适用于有多个线程等待一个共享资源，但每次只能一个线程进行处理的情况。
+例如，生产者-消费者模型中，当有一个生产者线程生产了一个产品，可以使用<code>notify</code>唤醒一个消费者线程来消费该产品。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">SharedResource</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Queue</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">queue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CAPACITY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">produce</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">queue</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">queue</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Produced: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notify</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒一个等待的消费者线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">consume</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">queue</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">queue</span><span class="p">.</span><span class="na">poll</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Consumed: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notify</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒一个等待的生产者线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">NotifyExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SharedResource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SharedResource</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">producer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">produce</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">consumer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">consume</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">producer</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">consumer</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="notifyall">notifyAll</h2>
+<p><code>notifyAll</code>方法用于唤醒在该对象监视器上等待的所有线程。所有被唤醒的线程将竞争对象的监视器锁，只有一个线程能成功获得锁并继续执行。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">notifyAll</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p><code>notifyAll</code>适用于多个线程等待同一个条件，并且当条件满足时，需要所有等待的线程都重新检查条件的情况。
+例如，在某些复杂的同步场景中，当某个状态变化需要通知所有等待线程时，使用<code>notifyAll</code>可以确保所有等待的线程都被唤醒并检查新状态。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">SharedResource</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Queue</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">queue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CAPACITY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">produce</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">queue</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">queue</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Produced: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notifyAll</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒所有等待的消费者线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">consume</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">queue</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">queue</span><span class="p">.</span><span class="na">poll</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Consumed: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notifyAll</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒所有等待的生产者线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">NotifyAllExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SharedResource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SharedResource</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">producer1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">produce</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">producer2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">produce</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">consumer1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">consume</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">consumer2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">consume</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">producer1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">producer2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">consumer1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">consumer2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="wait">wait</h2>
+<p><code>wait</code>方法使当前线程进入等待状态，同时<code>wait()</code>也会让当前线程释放它所持有的锁。
+直到其他线程调用该对象的<code>notify</code>方法或<code>notifyAll</code>方法来唤醒它，或者在指定的时间内没有被唤醒。该方法必须在同步块或同步方法中调用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">wait</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">wait</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">timeout</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">wait</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">timeout</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">nanos</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><ul>
+<li><code>wait()</code>：使当前线程无限期等待，直到被唤醒。</li>
+<li><code>wait(long timeout)</code>：使当前线程等待指定的毫秒数后自动唤醒。</li>
+<li><code>wait(long timeout, int nanos)</code>：使当前线程等待指定的时间（以毫秒和纳秒为单位）后自动唤醒。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WaitNotifyExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">waitingThread</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is waiting...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">lock</span><span class="p">.</span><span class="na">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is resumed.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">notifyingThread</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is notifying...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">lock</span><span class="p">.</span><span class="na">notify</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">waitingThread</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// Ensure waitingThread starts waiting</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notifyingThread</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>需要注意区分<code>wait</code>方法与<code>sleep</code>方法，很多人分不清。<code>sleep</code>和<code>wait</code>方法异同点：</p>
+<ul>
+<li><code>sleep()</code>属于<code>Thread</code>类，<code>wait()</code>属于<code>Object</code>类；</li>
+<li><code>sleep()</code>和<code>wait()</code>都会抛出<code>InterruptedException</code>异常，这个异常属于<code>checkedException</code>是不可避免；</li>
+<li>两者比较的共同之处是，都是使程序等待多长时间。不同的是调用<code>sleep()</code>不会释放锁，会使线程堵塞，而调用<code>wait()</code>会释放锁，让线程进入等待状态，用 <code>notify()</code>、<code>notifyall()</code>可以唤醒，或者等待时间到了；这是因为，如果没有释放锁，那么其它线程就无法进入对象的同步方法或者同步控制块中，那么就无法执行 <code>notify()</code> 或者 <code>notifyAll()</code> 来唤醒挂起的线程，造成死锁。</li>
+<li><code>wait()</code>必须在同步<code>synchronized</code>块里使用，<code>sleep()</code>可以在任意地方使用；</li>
+</ul>
+<p>其中&quot;<code>wait()</code>必须在同步<code>synchronized</code>块里使用&quot;，不止<code>wait</code>方法，<code>notify、notifyAll</code>也和<code>wait</code>方法一样，必须在<code>synchronized</code>块里使用，为什么呢？</p>
+<p>是为了避免丢失唤醒问题。假设没有<code>synchronized</code>修饰，使用了<code>wait</code>方法而没有设置等待时间，也没有调用唤醒方法或者唤醒方法调用的时机不对，这个线程将会永远的堵塞下去。
+<code>wait</code>、<code>notify</code>、<code>notifyAll</code>方法调用的时候要释放锁，你都没给它加锁，他怎么释放锁。所以如果没在<code>synchronized</code>块中调用<code>wait()、notify、notifyAll</code>方法是肯定抛异常的。</p>
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+    
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+        buttonColorDark: '#212121', 
+        buttonColorLight: '#f7f7f7', 
+        saveInCookies: false, 
+        autoMatchOsTheme: true 
+    }).showWidget();
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+            new Darkmode({
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+                mixColor: '#f7f7f7', 
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+                buttonColorDark: '#212121', 
+                buttonColorLight: '#f7f7f7', 
+                saveInCookies: false, 
+                autoMatchOsTheme: true 
+            }).toggle();
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+    
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+
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+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/blog-site/public/posts/javabasics/rookie-operation/index.html b/blog-site/public/posts/javabasics/rookie-operation/index.html
new file mode 100644
index 00000000..25ffc8b5
--- /dev/null
+++ b/blog-site/public/posts/javabasics/rookie-operation/index.html
@@ -0,0 +1,2682 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java运算 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="运算符与表达式 运算符 运算符指明对操作数的运算方式。组成表达式的Java操作符有很多种。 运算符按照其要求的操作数数目来分，可以有单目运算符、双目运算符和三目运算符" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
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+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%90%e7%ae%97%e7%ac%a6%e4%b8%8e%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    运算符与表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ae%97%e6%9c%af%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    算术运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b5%8b%e5%80%bc%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    赋值运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%af%94%e8%be%83%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    比较运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%bb%e8%be%91%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    逻辑运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%8d%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    位运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%89%e7%9b%ae%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    三目运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#instanceof">
+                    instanceof
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%90%e7%ae%97%e9%a1%ba%e5%ba%8f">
+                    运算顺序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%ad%a3%e5%88%99%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    正则表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#lambda%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    Lambda表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%a7%e5%88%b6%e6%b5%81%e8%af%ad%e5%8f%a5">
+                    控制流语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#if-else%e8%af%ad%e5%8f%a5">
+                    if-else语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#switch%e8%af%ad%e5%8f%a5">
+                    switch语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#for%e8%af%ad%e5%8f%a5">
+                    for语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#do-while%e5%92%8cwhile%e8%af%ad%e5%8f%a5">
+                    do-while和while语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e6%95%b0%e4%bc%a0%e9%80%92">
+                    参数传递
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b5%ae%e7%82%b9%e7%b1%bb%e7%b2%be%e5%ba%a6%e9%97%ae%e9%a2%98">
+                    浮点类精度问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#bigdecimal">
+                    BigDecimal
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e6%9c%ac%e7%94%a8%e6%b3%95">
+                    基本用法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%88%8d%e5%85%a5%e8%a7%84%e5%88%99">
+                    舍入规则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#scale%e5%b1%9e%e6%80%a7">
+                    scale属性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%af%94%e8%be%83%e5%a4%a7%e5%b0%8f">
+                    比较大小
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#math">
+                    Math
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#ceil%e5%92%8cfloor">
+                    ceil和floor
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
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+                        <h2 id="post_single_title">Java运算</h2>
+                        <span id="post_page_title_date" class="date">2021.01.30</span>
+                        
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+                    <div class="post_content markdown"><h2 id="运算符与表达式">运算符与表达式</h2>
+<h3 id="运算符">运算符</h3>
+<p>运算符指明对操作数的运算方式。组成表达式的Java操作符有很多种。
+运算符按照其要求的操作数数目来分，可以有单目运算符、双目运算符和三目运算符，它们分别对应于1个、2个、3个操作数。
+按其功能来分，可以有算术运算符、赋值运算符、比较(关系)运算符、逻辑运算符、位运算符和其他运算符。</p>
+<h4 id="算术运算符">算术运算符</h4>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>备注</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>+</td>
+<td>加法</td>
+<td>相加运算符两侧的值</td>
+<td></td>
+<td><code>int sum = 5 + 3;</code></td>
+</tr>
+<tr>
+<td>-</td>
+<td>减法</td>
+<td>左操作数减去右操作数</td>
+<td></td>
+<td><code>int difference = 5 - 3;</code></td>
+</tr>
+<tr>
+<td>*</td>
+<td>乘法</td>
+<td>相乘操作符两侧的值</td>
+<td></td>
+<td><code>int product = 5 * 3;</code></td>
+</tr>
+<tr>
+<td>/</td>
+<td>除法</td>
+<td>左操作数除以右操作数</td>
+<td>右操作数不能为0</td>
+<td><code>int quotient = 10 / 2;</code></td>
+</tr>
+<tr>
+<td>%</td>
+<td>取余</td>
+<td>左操作数除以右操作数的余数</td>
+<td></td>
+<td><code>int remainder = 10 % 3;</code></td>
+</tr>
+<tr>
+<td>++</td>
+<td>自增</td>
+<td>操作数的值增加1</td>
+<td></td>
+<td><code>int a = 5; a++;</code></td>
+</tr>
+<tr>
+<td>&ndash;</td>
+<td>自减</td>
+<td>操作数的值减少1</td>
+<td></td>
+<td><code>int a = 5; a--;</code></td>
+</tr>
+</tbody>
+</table>
+<p>关于取余，如果被取余的数小于取余的数，那取余的结果就是被除数，例如，<code>4%5=4</code>、<code>3%5=3</code>；
+如果被取余的数等于取余的数，结果是0，例如，<code>5%5=0</code>；
+如果取余数是1，结果是0，例如，<code>9%1=0</code>。</p>
+<p>当使用随机数生成器产生的结果时，取余运算可将结果限制在上限为操作数最大值减1的范围。
+例如：n是随机数，那么<code>n%10</code>就是<code>0~9</code>中的一个数。无论n是多大的数，<code>n%10</code>只能是<code>0~9</code>之间的一个数，利用这一特性，可以应用在数据库分库、分表等。</p>
+<p>对于自增和自减，需要特别留意的是<code>++</code>和<code>--</code>运算符可以前置、后置，都是合法的语句，如<code>a++</code>和<code>++a</code>都是合法的，上面这两种写法其最终的结果都是是变量a的值加1了，但是它们之间也是有区别的。
+其区别是：表达是<code>++a</code>会先将a的值自增1，然后在使用变量a，而表达式<code>a++</code>是先使用了a的值，然后再让a的值自增1。也就是说在一些表达式，使用<code>a++</code>和使用<code>++a</code>得到的结果时不一样的，例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">i</span><span class="o">++</span><span class="p">);</span><span class="c1">// 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="o">++</span><span class="n">i</span><span class="p">);</span><span class="c1">// 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>++</code>和<code>--</code>两个运算符只能作用于变量，而不能作用于表达式，例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 编译报错</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">((</span><span class="n">j</span><span class="o">+</span><span class="n">i</span><span class="p">)</span><span class="o">++</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="赋值运算符">赋值运算符</h4>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>=</td>
+<td>赋值</td>
+<td>将右操作数的值赋给左侧操作数</td>
+<td><code>int a = 5;</code></td>
+</tr>
+<tr>
+<td>+=</td>
+<td>加等于</td>
+<td>把左操作数和右操作数相加赋值给左操作数</td>
+<td><code>int b = 3; b += 2;</code></td>
+</tr>
+<tr>
+<td>-=</td>
+<td>减等于</td>
+<td>把左操作数和右操作数相减赋值给左操作数</td>
+<td><code>int c = 7; c -= 4;</code></td>
+</tr>
+<tr>
+<td>*=</td>
+<td>乘等于</td>
+<td>把左操作数和右操作数相乘赋值给左操作数</td>
+<td><code>int d = 2; d *= 3;</code></td>
+</tr>
+<tr>
+<td>/=</td>
+<td>除等于</td>
+<td>把左操作数和右操作数相除赋值给左操作数</td>
+<td><code>int e = 10; e /= 2;</code></td>
+</tr>
+<tr>
+<td>%=</td>
+<td>模等于</td>
+<td>把左操作数和右操作数取模后赋值给左操作数</td>
+<td><code>int f = 10; f %= 3;</code></td>
+</tr>
+<tr>
+<td>&laquo;=</td>
+<td>左位移等于</td>
+<td>把左操作数和右操作数进行左移运算后赋值给左操作数</td>
+<td><code>int g = 8; g &lt;&lt;= 2;</code></td>
+</tr>
+<tr>
+<td>&raquo;=</td>
+<td>右位移等于</td>
+<td>把左操作数和右操作数进行右移运算后赋值给左操作数</td>
+<td><code>int h = 16; h &gt;&gt;= 2;</code></td>
+</tr>
+<tr>
+<td>&amp;=</td>
+<td>按位与等于</td>
+<td>把左操作数和右操作数进行按位与运算后赋值给左操作数</td>
+<td><code>int i = 5; i &amp;= 3;</code></td>
+</tr>
+<tr>
+<td>|=</td>
+<td>按位或等于</td>
+<td>把左操作数和右操作数进行按位或运算后赋值给左操作数</td>
+<td><code>int j = 5; j &amp;#124;= 3;</code></td>
+</tr>
+<tr>
+<td>^=</td>
+<td>异或等于</td>
+<td>把左操作数和右操作数进行按位异或运算后赋值给左操作数</td>
+<td><code>int k = 5; k ^= 3;</code></td>
+</tr>
+</tbody>
+</table>
+<p>在进行复合赋值运算时，Java会自动进行类型转换。
+例如，如果左操作数是一个较小的数据类型，而右操作数是一个较大的数据类型，则右操作数会被自动转换为左操作数的类型，然后进行运算。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">byte</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">a</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="c1">// 合法，等同于 a = (byte)(a + 5);</span><span class="w">
+</span></span></span></code></pre></div><p>复合赋值运算符是原子操作，即它们是一个完整的、不可分割的操作，不会被中断或其他线程干扰。
+对于数值型数据，特别是整数类型，需要注意复合赋值运算符可能导致的溢出问题。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">127</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">b</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// b 现在是 -128，发生了溢出</span><span class="w">
+</span></span></span></code></pre></div><h4 id="比较运算符">比较运算符</h4>
+<p>比较运算符也称为关系运算符，用于展示两个操作数之间的关系。
+使用比较运算符表达式的最终结果为<code>boolean</code>型，也就是其结果只有两个<code>true</code>和<code>false</code>。</p>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>==</td>
+<td>双等号</td>
+<td>检查两个操作数的值是否相等</td>
+<td><code>boolean isEqual = (5 == 5);</code></td>
+</tr>
+<tr>
+<td>!=</td>
+<td>不等号</td>
+<td>检查两个操作数的值是否不相等</td>
+<td><code>boolean notEqual = (5 != 3);</code></td>
+</tr>
+<tr>
+<td>&gt;</td>
+<td>大于</td>
+<td>检查左操作数的值是否大于右操作数</td>
+<td><code>boolean greaterThan = (5 &gt; 3);</code></td>
+</tr>
+<tr>
+<td>&lt;</td>
+<td>小于</td>
+<td>检查左操作数的值是否小于右操作数</td>
+<td><code>boolean lessThan = (5 &lt; 3);</code></td>
+</tr>
+<tr>
+<td>&gt;=</td>
+<td>大于等于</td>
+<td>检查左操作数的值是否大于或等于右操作数</td>
+<td><code>boolean greaterOrEqual = (5 &gt;= 5);</code></td>
+</tr>
+<tr>
+<td>&lt;=</td>
+<td>小于等于</td>
+<td>检查左操作数的值是否小于或等于右操作数</td>
+<td><code>boolean lessOrEqual = (5 &lt;= 5);</code></td>
+</tr>
+</tbody>
+</table>
+<h4 id="逻辑运算符">逻辑运算符</h4>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>&amp;&amp;</td>
+<td>逻辑与</td>
+<td>当且仅当两个操作数都为真时，条件为真</td>
+<td><code>boolean result = (true &amp;&amp; false);</code></td>
+</tr>
+<tr>
+<td>||</td>
+<td>逻辑或</td>
+<td>如果两个操作数任何一个为真时，条件为真</td>
+<td><code>boolean result = (true || false);</code></td>
+</tr>
+<tr>
+<td>!</td>
+<td>逻辑非</td>
+<td>用来反转操作数的逻辑状态，条件取反</td>
+<td><code>boolean result = !true;</code></td>
+</tr>
+</tbody>
+</table>
+<p><code>&amp;&amp;</code>运算符，运算顺序是从左到右计算，运算规则是如果两个操作数都是真，则返回<code>true</code>，否则返回<code>false</code>。
+但是当判定到第一个操作数为<code>false</code>时，其结果必定为<code>false</code>，这时候就不再会判定第二个操作数了。
+这种特性可以在复杂条件语句中提高效率，并可以避免不必要的计算。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">++</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">j</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// flag的值: false,i的值:2,j的值:2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;flag的值: %s,i的值:%s,j的值:%s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">flag</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在使用逻辑运算符时，特别是在复杂的条件逻辑中，尽量保证逻辑表达式的意图清晰，建议使用括号明确运算顺序。</p>
+<h4 id="位运算符">位运算符</h4>
+<p>位运算符在追求代码效率和编写底层应用时，使用的比较多，在企业Java开发一般用到的较少。</p>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>&amp;</td>
+<td>按位与</td>
+<td>如果相对应位都是1，则结果为1，否则为0</td>
+<td><code>int result = 5 &amp; 3;</code></td>
+</tr>
+<tr>
+<td>|</td>
+<td>按位或</td>
+<td>如果相对应位都是0，则结果为0，否则为1</td>
+<td><code>int result = 5 | 3;</code></td>
+</tr>
+<tr>
+<td>^</td>
+<td>按位异或</td>
+<td>如果相对应位值相同，则结果为0，否则为1</td>
+<td><code>int result = 5 ^ 3;</code></td>
+</tr>
+<tr>
+<td>~</td>
+<td>按位取反</td>
+<td>翻转操作数的每一位，即0变成1，1变成0</td>
+<td><code>int result = ~5;</code></td>
+</tr>
+<tr>
+<td>&laquo;</td>
+<td>左移</td>
+<td>左操作数按位左移右操作数指定的位数</td>
+<td><code>int result = 5 &lt;&lt; 2;</code></td>
+</tr>
+<tr>
+<td>&raquo;</td>
+<td>右移</td>
+<td>左操作数按位右移右操作数指定的位数</td>
+<td><code>int result = 5 &gt;&gt; 2;</code></td>
+</tr>
+<tr>
+<td>&raquo;&gt;</td>
+<td>无符号右移</td>
+<td>左操作数的值按右操作数指定的位数右移，移动得到的空位以零填充</td>
+<td><code>int result = 5 &gt;&gt;&gt; 2;</code></td>
+</tr>
+</tbody>
+</table>
+<p>一些小技巧：</p>
+<ul>
+<li><code>&gt;&gt;</code>：右移几位就是相当于除以2的几次幂；</li>
+<li><code>&lt;&lt;</code>：左移几位就是相当于乘以2的几次幂；</li>
+<li><code>%</code>：当b为2的n次方时，有如下替换公式：<code>a % b = a &amp; (b-1)</code>；</li>
+</ul>
+<p>位运算符只能对整数型(<code>int</code>、<code>long</code>、<code>short</code>、<code>byte</code>)和字符型数据(<code>char</code>)进行操作。
+因为位运算符是以<code>bit</code>运算单位的，所以想要弄明白位运算符，就要先弄明白二进制的表示方法。</p>
+<p>以下示例用十进制的1和2进行运算，1用二进制表示为<code>0000 0001</code>，2用二进制表示为<code>0000 0010</code>，为了更好的理解位运算，下面我会详细解析：</p>
+<ul>
+<li><code>&amp;</code>：如果相对应位都是1，则结果为1，否则为0；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">0000 0010
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0000
+</span></span></code></pre></div></li>
+<li><code>|</code>：如果相对应位都是 0，则结果为 0，否则为 1；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">0000 0010
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0011
+</span></span></code></pre></div></li>
+<li><code>^</code>：如果相对应位值相同，则结果为0，否则为1；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">0000 0010
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0011
+</span></span></code></pre></div></li>
+<li><code>~</code>：翻转操作数的每一位，即0变成1，1变成0；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0011
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">1111 1100
+</span></span></code></pre></div></li>
+<li><code>&lt;&lt;</code>：左操作数按位左移右操作数指定的位数，如1左移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0100
+</span></span></code></pre></div></li>
+<li><code>&gt;&gt;</code>：左操作数按位右移右操作数指定的位数；（正数右移高位补0，负数右移高位补1）
+1右移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0000
+</span></span></code></pre></div>负一右移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">1111 1111
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">1111 1111
+</span></span></code></pre></div></li>
+<li><code>&gt;&gt;&gt;</code>：左操作数的值按右操作数指定的位数右移，移动得到的空位以零填充；（无符号右移，无论是正数还是负数，高位通通补0）
+1无符号右移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0000
+</span></span></code></pre></div>负一无符号右移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">1111 1111
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0011 1111
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="三目运算符">三目运算符</h4>
+<p>该运算符有3个操作数，其功能是对表达式条件进行判断，根据判断结果是<code>true</code>或者<code>false</code>两种情况赋予赋予不同的返回值。</p>
+<p>该运算符的主要是决定哪个值应该赋值给变量。在某些情况下，可以发现三目运算符和<code>if...else</code>作用是相同的，可以完全替代<code>if...else</code>。
+三目运算符可以使代码更加简洁和可读，特别是在简单的条件赋值或返回语句中，但应该尽量避免过多的嵌套三目运算符，以免降低代码的可读性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">?</span><span class="w">  </span><span class="n">1</span><span class="p">:</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 等价于if...else以下代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">var2</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那么三目运算符与<code>if...else</code>到底哪有啥不同？要探究这个原因，需要看JVM是对三目运算符怎么处理的。
+用<code>javap -verbose</code>命令，分别把<code>if...else</code>和三目运算符相关代码进行反编译：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果var2大于1 则var1等于1 否则等于2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">?</span><span class="w">  </span><span class="n">1</span><span class="p">:</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl">  <span class="o">//</span> <span class="o">...</span>
+</span></span><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl"> <span class="o">//</span> <span class="o">...</span>
+</span></span><span class="line"><span class="cl">  <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="n">java</span><span class="o">.</span><span class="n">lang</span><span class="o">.</span><span class="n">String</span><span class="p">[]);</span>
+</span></span><span class="line"><span class="cl">    <span class="n">descriptor</span><span class="p">:</span> <span class="p">([</span><span class="n">Ljava</span><span class="o">/</span><span class="n">lang</span><span class="o">/</span><span class="ne">String</span><span class="p">;)</span><span class="n">V</span>
+</span></span><span class="line"><span class="cl">    <span class="n">flags</span><span class="p">:</span> <span class="n">ACC_PUBLIC</span><span class="p">,</span> <span class="n">ACC_STATIC</span>
+</span></span><span class="line"><span class="cl">    <span class="n">Code</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">      <span class="n">stack</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">locals</span><span class="o">=</span><span class="mi">3</span><span class="p">,</span> <span class="n">args_size</span><span class="o">=</span><span class="mi">1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">0</span><span class="p">:</span> <span class="n">iconst_1</span> <span class="o">//</span> <span class="err">向栈里添加</span><span class="n">int类型</span> <span class="mi">1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">1</span><span class="p">:</span> <span class="n">istore_1</span> <span class="o">//</span> <span class="err">将</span><span class="ne">int</span> <span class="mi">1</span> <span class="err">存储到局部变量</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">2</span><span class="p">:</span> <span class="n">iconst_0</span> <span class="o">//</span> <span class="err">向栈里添加</span><span class="n">int类型</span> <span class="mi">0</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">3</span><span class="p">:</span> <span class="n">istore_2</span> <span class="o">//</span> <span class="err">将</span><span class="ne">int</span> <span class="mi">2</span> <span class="err">存储到局部变量</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">4</span><span class="p">:</span> <span class="n">iload_2</span>  <span class="o">//</span> <span class="err">从局部变量加载</span><span class="ne">int</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">5</span><span class="p">:</span> <span class="n">iconst_1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">6</span><span class="p">:</span> <span class="n">if_icmple</span>     <span class="mi">13</span>  <span class="o">//</span> <span class="err">将</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="err">步骤栈中的变量弹出</span> <span class="err">进行比较</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">9</span><span class="p">:</span> <span class="n">iconst_1</span> <span class="o">//</span> <span class="err">比较成功</span> <span class="err">存储该值到栈中</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">10</span><span class="p">:</span> <span class="n">goto</span>          <span class="mi">14</span> <span class="o">//</span> <span class="err">改变地址</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">13</span><span class="p">:</span> <span class="n">iconst_2</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">14</span><span class="p">:</span> <span class="n">istore_1</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">15</span><span class="p">:</span> <span class="k">return</span>
+</span></span><span class="line"><span class="cl">      <span class="n">LineNumberTable</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">6</span><span class="p">:</span> <span class="mi">0</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">7</span><span class="p">:</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">8</span><span class="p">:</span> <span class="mi">4</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">9</span><span class="p">:</span> <span class="mi">15</span>
+</span></span><span class="line"><span class="cl">      <span class="n">LocalVariableTable</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Start</span>  <span class="n">Length</span>  <span class="n">Slot</span>  <span class="n">Name</span>   <span class="n">Signature</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">0</span>      <span class="mi">16</span>     <span class="mi">0</span>  <span class="n">args</span>   <span class="p">[</span><span class="n">Ljava</span><span class="o">/</span><span class="n">lang</span><span class="o">/</span><span class="ne">String</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">2</span>      <span class="mi">14</span>     <span class="mi">1</span>  <span class="n">var1</span>   <span class="n">I</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">4</span>      <span class="mi">12</span>     <span class="mi">2</span>  <span class="n">var2</span>   <span class="n">I</span>
+</span></span><span class="line"><span class="cl">      <span class="n">StackMapTable</span><span class="p">:</span> <span class="n">number_of_entries</span> <span class="o">=</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">        <span class="n">frame_type</span> <span class="o">=</span> <span class="mi">253</span> <span class="o">/*</span> <span class="n">append</span> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">          <span class="n">offset_delta</span> <span class="o">=</span> <span class="mi">13</span>
+</span></span><span class="line"><span class="cl">          <span class="n">locals</span> <span class="o">=</span> <span class="p">[</span> <span class="ne">int</span><span class="p">,</span> <span class="ne">int</span> <span class="p">]</span>
+</span></span><span class="line"><span class="cl">        <span class="n">frame_type</span> <span class="o">=</span> <span class="mi">64</span> <span class="o">/*</span> <span class="n">same_locals_1_stack_item</span> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">          <span class="n">stack</span> <span class="o">=</span> <span class="p">[</span> <span class="ne">int</span> <span class="p">]</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="o">//</span> <span class="o">...</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="kt">int</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">var2</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl">  <span class="o">//</span> <span class="o">...</span>
+</span></span><span class="line"><span class="cl">  <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="n">java</span><span class="o">.</span><span class="n">lang</span><span class="o">.</span><span class="n">String</span><span class="p">[]);</span>
+</span></span><span class="line"><span class="cl">    <span class="n">descriptor</span><span class="p">:</span> <span class="p">([</span><span class="n">Ljava</span><span class="o">/</span><span class="n">lang</span><span class="o">/</span><span class="ne">String</span><span class="p">;)</span><span class="n">V</span>
+</span></span><span class="line"><span class="cl">    <span class="n">flags</span><span class="p">:</span> <span class="n">ACC_PUBLIC</span><span class="p">,</span> <span class="n">ACC_STATIC</span>
+</span></span><span class="line"><span class="cl">    <span class="n">Code</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">      <span class="n">stack</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">locals</span><span class="o">=</span><span class="mi">3</span><span class="p">,</span> <span class="n">args_size</span><span class="o">=</span><span class="mi">1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">0</span><span class="p">:</span> <span class="n">iconst_1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">1</span><span class="p">:</span> <span class="n">istore_1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">2</span><span class="p">:</span> <span class="n">iconst_0</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">3</span><span class="p">:</span> <span class="n">istore_2</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">4</span><span class="p">:</span> <span class="n">iload_2</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">5</span><span class="p">:</span> <span class="n">iconst_1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">6</span><span class="p">:</span> <span class="n">if_icmple</span>     <span class="mi">14</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">9</span><span class="p">:</span> <span class="n">iconst_1</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">10</span><span class="p">:</span> <span class="n">istore_1</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">11</span><span class="p">:</span> <span class="n">goto</span>          <span class="mi">16</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">14</span><span class="p">:</span> <span class="n">iconst_2</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">15</span><span class="p">:</span> <span class="n">istore_1</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">16</span><span class="p">:</span> <span class="k">return</span>
+</span></span><span class="line"><span class="cl">      <span class="n">LineNumberTable</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">6</span><span class="p">:</span> <span class="mi">0</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">7</span><span class="p">:</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">8</span><span class="p">:</span> <span class="mi">4</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">9</span><span class="p">:</span> <span class="mi">9</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">11</span><span class="p">:</span> <span class="mi">14</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">13</span><span class="p">:</span> <span class="mi">16</span>
+</span></span><span class="line"><span class="cl">      <span class="n">LocalVariableTable</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Start</span>  <span class="n">Length</span>  <span class="n">Slot</span>  <span class="n">Name</span>   <span class="n">Signature</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">0</span>      <span class="mi">17</span>     <span class="mi">0</span>  <span class="n">args</span>   <span class="p">[</span><span class="n">Ljava</span><span class="o">/</span><span class="n">lang</span><span class="o">/</span><span class="ne">String</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">2</span>      <span class="mi">15</span>     <span class="mi">1</span>  <span class="n">var1</span>   <span class="n">I</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">4</span>      <span class="mi">13</span>     <span class="mi">2</span>  <span class="n">var2</span>   <span class="n">I</span>
+</span></span><span class="line"><span class="cl">      <span class="n">StackMapTable</span><span class="p">:</span> <span class="n">number_of_entries</span> <span class="o">=</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">        <span class="n">frame_type</span> <span class="o">=</span> <span class="mi">253</span> <span class="o">/*</span> <span class="n">append</span> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">          <span class="n">offset_delta</span> <span class="o">=</span> <span class="mi">14</span>
+</span></span><span class="line"><span class="cl">          <span class="n">locals</span> <span class="o">=</span> <span class="p">[</span> <span class="ne">int</span><span class="p">,</span> <span class="ne">int</span> <span class="p">]</span>
+</span></span><span class="line"><span class="cl">        <span class="n">frame_type</span> <span class="o">=</span> <span class="mi">1</span> <span class="o">/*</span> <span class="n">same</span> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="o">//</span> <span class="o">...</span>
+</span></span></code></pre></div><p>通过查阅<a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-6.html">《Java虚拟机指令集》</a>，在参照上面反编译的字节码反编译的内容，可以看到JVM对上边的代码进行了什么处理。
+通过比较两次反编译后的代码可以得出一个结论，即三目运算符与<code>if..else</code>执行的命令几乎没有差异。
+但是对于实际开发来说三目运算符的可读性相对不如<code>if...else</code>代码，所以在常见的编码中，三目运算符更倾向于简单的<code>if...else</code>语句的替代。</p>
+<h4 id="instanceof">instanceof</h4>
+<p><code>instanceof</code>是一个双目运算符，该关键字的作用是判断左边的对象是不是右边类的实例，并返回一个<code>boolean</code>值。
+<code>instanceof</code>可以用来检查对象的类型，包括检查对象是否是其直接类的实例或者其父类的实例，或实现了某个接口。
+在实际开发中经常用于在运行时动态确定对象的类型，从而决定如何处理对象或执行特定的逻辑。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">animal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断 animal 是否是 Animal 类的实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isAnimal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">animal</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Animal</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Is animal an instance of Animal? &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">isAnimal</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出：true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断 animal 是否是 Dog 类的实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isDog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">animal</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Dog</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Is animal an instance of Dog? &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">isDog</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出：true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断 animal 是否是 Object 类的实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isObject</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">animal</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Object</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Is animal an instance of Object? &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">isObject</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出：true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="运算顺序">运算顺序</h4>
+<p>Java语言中运算符的优先级共分为14级，其中1级最高，14级最低，在同一个表达式中运算符优先级高的先执行。
+Java中大部分运算符也是从左向右结合的，只有单目运算符、赋值运算符、三目运算符例外，是从右向左运算的。</p>
+<table>
+<thead>
+<tr>
+<th style="text-align:center">优先级</th>
+<th>运算符</th>
+<th style="text-align:center">结合性</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td style="text-align:center">1</td>
+<td>()、[]</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">2</td>
+<td>!、+、-、~、++、&ndash;</td>
+<td style="text-align:center">从右向左</td>
+</tr>
+<tr>
+<td style="text-align:center">3</td>
+<td>*、/、%</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">4</td>
+<td>+、-</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">5</td>
+<td>«、»、&raquo;&gt;</td>
+<td style="text-align:center">从左向</td>
+</tr>
+<tr>
+<td style="text-align:center">6</td>
+<td>&lt;、&lt;=、&gt;、&gt;=、instanceof</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">7</td>
+<td>==、!=</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">8</td>
+<td>&amp;</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">10</td>
+<td>|</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">11</td>
+<td>&amp;&amp;</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">12</td>
+<td>||</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">13</td>
+<td>?:</td>
+<td style="text-align:center">从右向左</td>
+</tr>
+<tr>
+<td style="text-align:center">14</td>
+<td>=、+=、-=、*=、/=、&amp;=、|=、^=、~=、&laquo;=、&raquo;=、&raquo;&gt;=</td>
+<td style="text-align:center">从右向左</td>
+</tr>
+</tbody>
+</table>
+<p>在实际开发中，不要把一个表达式写得过于复杂。如果一个表达式过于复杂，则会影响代码可读性，建议把它分成几步来完成。
+不要过多地依赖运算符的优先级来控制表达式的执行顺序，这样可读性太差，尽量使用小括号来控制表达式的执行顺序，这样能提高代码的可读性和减少歧义。</p>
+<h3 id="表达式">表达式</h3>
+<p>在Java中表达式通常是以分号结尾的一段代码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">int</span><span class="w"> </span><span class="n">sum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">c</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">y</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">a</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>表达式是由运算符和运算对象组成的，表达式可以定义为一组变量、常量、运算符等符号的组合，其结构形成一个计算值的过程，换句话说，表达式是用来计算值的一种编程结构。
+变量的赋值与计算都离不开表达式，表达式的运算依赖于变量、常量和运算符。</p>
+<h4 id="正则表达式">正则表达式</h4>
+<p>正则表达式，又称规则表达式，英语：<code>Regular Expression</code>，在代码中常简写为<code>regex</code>、<code>regexp</code>或<code>RE</code>。
+正则表达式通常被用来检索、替换那些符合某个模式(规则)的文本，在众多语言中都可以支持正则表达式，如<code>Perl</code>、<code>PHP</code>、<code>Java</code>、<code>Python</code>、<code>Ruby</code>等。</p>
+<p>正则表达式并不仅限于某一种语言，但是在每种语言中有细微的差别。
+例如：在其他语言中，<code>\\</code> 表示，在正则表达式中插入一个普通的（字面上的）反斜杠。在Java中，<code>\\</code> 表示，插入一个正则表达式的反斜线，所以其后的字符具有特殊的意义。
+所以，在其他的语言中，一个反斜杠<code>\</code>就足以具有转义的作用，而在Java中正则表达式中则需要有两个反斜杠才能被解析为其他语言中的转义作用。
+也可以简单的理解在Java的正则表达式中，两个 <code>\\</code> 代表其他语言中的一个<code>\</code>，这也就是为什么表示一位数字的正则表达式是 <code>\\d</code>，而表示一个普通的反斜杠是 <code>\\\\</code>。</p>
+<p>正则表达式是由普通字符（如英文字母）以及特殊字符（也称为元字符）组成的文字模式，例如：<code>String str = &quot;abc^123/?[1,2]&quot;;</code>。
+在Java中主要是使用正则表达式处理字符串，Java从jdk1.4开始提供了一个包<code>java.util.regex</code>来处理正则表达式。
+主要使用<code>java.util.regex</code>包中<code>Pattern</code>类，<code>Matcher</code>类来处理字符串，使用正则表达式示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 表示匹配以字母a为开头的单词</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">regx</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;\\ba\\w*\\b&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将给定的正则表达式编译到具有给定标志的模式中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Pattern</span><span class="w"> </span><span class="n">pattern</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern</span><span class="p">.</span><span class="na">compile</span><span class="p">(</span><span class="n">regx</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 创建匹配给定输入与此模式的匹配器</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Matcher</span><span class="w"> </span><span class="n">matcher</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pattern</span><span class="p">.</span><span class="na">matcher</span><span class="p">(</span><span class="s">&#34;abcdab cccabcd aaacd&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 循环 查找与上边正则匹配的字符序列</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">matcher</span><span class="p">.</span><span class="na">find</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 返回 由以前匹配操作 所匹配的 输入子序列</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">matcher</span><span class="p">.</span><span class="na">group</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;:&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">res</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>总的来说，正则表达式是对字符串操作的一种逻辑公式，用事先定义好的一些特定字符、及这些特定字符的组合，组成一个&quot;规则字符串&quot;，这个&quot;规则字符串&quot;用来表达对字符串的一种过滤逻辑。
+正则表达式的灵活性、逻辑性和功能性非常的强，可以迅速地用极简单的方式达到字符串的复杂控制，但是对于刚接触的人来说比较晦涩难懂。以下是常用正则表达式：</p>
+<table>
+<thead>
+<tr>
+<th>描述</th>
+<th>正则表达式</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>是否为数字</td>
+<td><code>^[0-9]*$</code></td>
+</tr>
+<tr>
+<td>是否为n位数数字</td>
+<td><code>^\d{n}$</code></td>
+</tr>
+<tr>
+<td>是否为m-n位的数字</td>
+<td><code>^\d{m,n}$</code></td>
+</tr>
+<tr>
+<td>是否输入至少n位的数字</td>
+<td><code>^\d{n,}$</code></td>
+</tr>
+<tr>
+<td>是否为整数</td>
+<td><code>^-?\d+$</code></td>
+</tr>
+<tr>
+<td>是否为负整数</td>
+<td><code>^-[0-9]*[1-9][0-9]*$</code></td>
+</tr>
+<tr>
+<td>是否为正整数</td>
+<td><code>^[0-9]*[1-9][0-9]*$</code></td>
+</tr>
+<tr>
+<td>是否为汉字</td>
+<td><code>^[\u4e00-\u9fa5]{0,}$</code></td>
+</tr>
+<tr>
+<td>是否为邮箱</td>
+<td><code>^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$</code></td>
+</tr>
+<tr>
+<td>是否为域名</td>
+<td><code>[a-zA-Z0-9][-a-zA-Z0-9]{0,62}(\.[a-zA-Z0-9][-a-zA-Z0-9]{0,62})+\.?</code></td>
+</tr>
+<tr>
+<td>是否为URL</td>
+<td><code>^http://([\w-]+\.)+[\w-]+(/[\w-./?%&amp;=]*)?$</code></td>
+</tr>
+<tr>
+<td>是否为手机号码</td>
+<td>`^(13[0-9]</td>
+</tr>
+<tr>
+<td>是否为固话号码</td>
+<td>`^($$\d{3,4}-)</td>
+</tr>
+<tr>
+<td>是否为身份证号码</td>
+<td>`^(\d{15}</td>
+</tr>
+<tr>
+<td>是否为日期（YYYY-MM-DD）</td>
+<td><code>^\d{4}-\d{2}-\d{2}$</code></td>
+</tr>
+<tr>
+<td>是否为时间（HH:MM:SS）</td>
+<td><code>^\d{2}:\d{2}:\d{2}$</code></td>
+</tr>
+<tr>
+<td>是否为十六进制颜色码</td>
+<td>`^#?([a-fA-F0-9]{6}</td>
+</tr>
+<tr>
+<td>是否包含HTML标签</td>
+<td>`&lt;(&quot;[^&quot;]*&quot;</td>
+</tr>
+<tr>
+<td>是否为金额（带小数点的数字）</td>
+<td><code>^\d+(\.\d{1,2})?$</code></td>
+</tr>
+<tr>
+<td>是否为UUID</td>
+<td><code>^[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}$</code></td>
+</tr>
+</tbody>
+</table>
+<h4 id="lambda表达式">Lambda表达式</h4>
+<p><code>Lambda</code>表达式是Java 8引入的一项重要功能，用于简化实现接口中单个抽象方法的类的写法，使代码更加简洁和易读。
+<code>Lambda</code>表达式可以看作是匿名函数，可以在没有声明其所属类的情况下创建函数对象。</p>
+<p><code>Lambda</code>表达式的基本语法如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Consumer</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">consumer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><ul>
+<li>参数列表：<code>(s)</code>为参数，类似于方法的参数；</li>
+<li>箭头符号：<code>-&gt;</code>，用于分隔参数和方法体；</li>
+<li>方法体：<code>System.out.println(s)</code>为方法体，方法体可以是一个表达式或一个代码块；</li>
+</ul>
+<p><code>Lambda</code>表达式通常用于替代匿名类：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 使用匿名类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Comparator</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">comparator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Comparator</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">compare</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s1</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">s2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用Lambda表达式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Comparator</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">comparatorLambda</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">s1</span><span class="p">,</span><span class="w"> </span><span class="n">s2</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p><code>Lambda</code>在开发中最常用的就是集合中<code>Stream</code>流，举例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="s">&#34;a&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;b&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;c&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用forEach方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">list</span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">item</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">item</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用stream API进行过滤和排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filteredList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">stream</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="p">.</span><span class="na">filter</span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">startsWith</span><span class="p">(</span><span class="s">&#34;a&#34;</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="p">.</span><span class="na">sorted</span><span class="p">((</span><span class="n">s1</span><span class="p">,</span><span class="w"> </span><span class="n">s2</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">s2</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="p">.</span><span class="na">collect</span><span class="p">(</span><span class="n">Collectors</span><span class="p">.</span><span class="na">toList</span><span class="p">());</span><span class="w">
+</span></span></span></code></pre></div><p>Java 8引入了许多函数式接口，这些接口在<code>java.util.function</code>包中定义，常用的函数式接口包括：</p>
+<ul>
+<li><code>Consumer&lt;T&gt;</code>：<code>Consumer</code>接口表示接受一个输入参数并且不返回结果的操作，它通常用于对单个参数执行某种操作；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">accept</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConsumerExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Consumer</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">printer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printer</span><span class="p">.</span><span class="na">accept</span><span class="p">(</span><span class="s">&#34;Hello, World!&#34;</span><span class="p">);</span><span class="w">  </span><span class="c1">// 输出：Hello, World!</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>Supplier&lt;T&gt;</code>：<code>Supplier</code>接口表示提供一个结果的供应商，无输入参数，它通常用于提供或生成某种值；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">T</span><span class="w"> </span><span class="nf">get</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SupplierExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Supplier</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">supplier</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="s">&#34;Hello, Supplier!&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">supplier</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">  </span><span class="c1">// 输出：Hello, Supplier!</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>Function&lt;T, R&gt;</code>：<code>Function</code>接口表示接受一个输入参数并返回一个结果的函数，它通常用于将输入转换为输出；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">R</span><span class="w"> </span><span class="nf">apply</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FunctionExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Function</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">lengthFunction</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">lengthFunction</span><span class="p">.</span><span class="na">apply</span><span class="p">(</span><span class="s">&#34;Hello&#34;</span><span class="p">));</span><span class="w">  </span><span class="c1">// 输出：5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>Predicate&lt;T&gt;</code>：<code>Predicate</code>接口表示一个接受单个参数并返回布尔值的断言，它通常用于条件判断；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">boolean</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PredicateExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Predicate</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">isEmpty</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">isEmpty</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">));</span><span class="w">  </span><span class="c1">// 输出：true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">isEmpty</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="s">&#34;Hello&#34;</span><span class="p">));</span><span class="w">  </span><span class="c1">// 输出：false</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>在<code>Lambda</code>表达式中，方法的引用也发生了变化，使用<code>::</code>操作符，主要有四种类型：</p>
+<ul>
+<li>引用静态方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Consumer</span><span class="o">&lt;</span><span class="n">List</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">sort</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Collections</span><span class="p">::</span><span class="n">sort</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>引用实例方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Predicate</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">equals</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">::</span><span class="n">equals</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>引用对象的实例方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Function</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">length</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">::</span><span class="n">length</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>引用构造函数；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Supplier</span><span class="o">&lt;</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">listSupplier</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ArrayList</span><span class="p">::</span><span class="k">new</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h2 id="控制流语句">控制流语句</h2>
+<h3 id="if-else语句">if-else语句</h3>
+<p><code>if</code>语句是最基本的控制语句，它只有在<code>if(exception)</code>为<code>true</code>的时候才会执行特定的代码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">var1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;hello world ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>if</code>语句后面可以跟<code>else</code>语句，当<code>if(exception)</code>为<code>false</code>时，<code>else</code>语句体将被执行。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">var1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;if ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="k">else</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;else ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>if</code>语句后面可以跟<code>else-if-else</code>语句：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HelloWorld</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="kd">var</span><span class="w"> </span><span class="err">= &#34;</span><span class="n">123</span><span class="s">&#34;;
+</span></span></span><span class="line"><span class="cl"><span class="s">        if (&#34;</span><span class="n">123</span><span class="s">&#34;.equals(var)){
+</span></span></span><span class="line"><span class="cl"><span class="s">            System.out.println(&#34;</span><span class="n">123</span><span class="w"> </span><span class="p">...</span><span class="s">&#34;);
+</span></span></span><span class="line"><span class="cl"><span class="s">        }else if(&#34;</span><span class="n">234</span><span class="s">&#34;.equals(var)){
+</span></span></span><span class="line"><span class="cl"><span class="s">            System.out.println(&#34;</span><span class="n">234</span><span class="w"> </span><span class="p">...</span><span class="s">&#34;);
+</span></span></span><span class="line"><span class="cl"><span class="s">        }else if (&#34;</span><span class="n">345</span><span class="s">&#34;.equals(var)){
+</span></span></span><span class="line"><span class="cl"><span class="s">            System.out.println(&#34;</span><span class="n">345</span><span class="w"> </span><span class="p">...</span><span class="s">&#34;);
+</span></span></span><span class="line"><span class="cl"><span class="s">        }else{
+</span></span></span><span class="line"><span class="cl"><span class="s">            System.out.println(&#34;</span><span class="p">...</span><span class="s">&#34;);
+</span></span></span><span class="line"><span class="cl"><span class="s">        }
+</span></span></span><span class="line"><span class="cl"><span class="s">    }
+</span></span></span><span class="line"><span class="cl"><span class="s">}
+</span></span></span></code></pre></div><h3 id="switch语句">switch语句</h3>
+<p><code>switch</code>语句在项目开发中比较常用，可以和<code>if-else</code>实现相同的功能，但使用<code>switch</code>语句可以提高代码的可读性。</p>
+<p><code>switch-case</code>语句用于判断一个变量是否等于一系列值中的某个值，每个值称为一个分支。
+<code>switch</code>语句还可以包含一个<code>default</code>分支，当没有任何<code>case</code>分支的值与变量值相等时，<code>default</code>分支的代码将被执行。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">case</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;123&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">case</span><span class="w"> </span><span class="s">&#34;456&#34;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">default</span><span class="w"> </span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;over ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">   
+</span></span></span></code></pre></div><p>当变量的值与<code>case</code>语句的值相等时，那么<code>case</code>语句之后的语句开始执行，直到<code>break</code>语句出现，才会跳出<code>switch</code>语句。
+如果没有<code>break</code>语句出现，程序会继续执行下一条<code>case</code>语句，直到出现<code>break</code>语句，需要注意的是，<code>default</code>分支不需要<code>break</code>语句。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="k">case</span><span class="w"> </span><span class="n">100</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;first case ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="k">case</span><span class="w"> </span><span class="n">200</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;second case ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>switch</code>语句中的变量类型可以是，<code>byte</code>、<code>short</code>、<code>int</code>、<code>char</code>或者<code>enum</code>，从Java7开始，可以在<code>switch</code>条件判断语句中使用<code>String</code>对象。
+<code>switch</code>不支持<code>long</code>，是因为<code>switch</code>的设计初衷是对那些只有少数的几个值进行等值判断，如果值过于复杂，那么还是用<code>if</code>比较合适。</p>
+<h3 id="for语句">for语句</h3>
+<p>for语句提供了一种紧凑的方法来遍历一系列值。因为它反复循环直到满足特定条件，程序员经常将其称为“for循环”。
+for循环执行的次数是在执行前就确定的，for语句的一般形式可以表示为：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>for循环的三个表达式是可选的，例如可以这样创建一个无限循环：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(;;){
+</span></span><span class="line"><span class="cl">    // to do ...
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p><code>foreach</code>语句是Java5的新特征之一，在遍历数组、集合方面，为开发人员提供了极大的方便。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">arr</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在for循环中，<code>可以使用continue</code>语句用来结束当前循环，并进入下一次循环。
+注意仅仅这一次循环结束了，不是所有循环结束了，后边的循环依旧进行。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果s等于1,则结束本次循环 执行下次循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>break</code>语句作用是跳出循环，<code>break</code>主要用在循环语句或者<code>switch</code>语句中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HelloWorld</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// s等于2,结束for循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>如果存在多层循环，要注意<code>break</code>只能跳出一层循环，而不能结束多层循环。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;外层 for ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>如果想要跳出多层循环，可以用以下方式，当然也可以用<code>break</code>跳两次循环。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">test</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="w"> </span><span class="n">test</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;外层 for ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>continue</code>也可以用上面的这种方式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nl">test</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="w"> </span><span class="n">test</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;外层 for ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>return</code>语句表示从当前方法退出，控制流返回到调用方法的地方。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;外层 for ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>return</code>语句有两种形式，一种返回值，另一种不返回值。
+要返回一个值，只需将值(或计算该值的表达式)放在<code>return</code>关键字之后即可，像这样<code>return ++count;</code>。</p>
+<h3 id="do-while和while语句">do-while和while语句</h3>
+<p><code>while</code>语句对表达式进行计算，表达式必须返回一个布尔值。如果表达式的计算结果为<code>true</code>,<code>while</code>语句将执行<code>while</code>块中的语句。
+<code>while</code>语句继续测试表达式并执行其块，直到表达式的计算结果为<code>false</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">while</span><span class="p">(</span><span class="o">++</span><span class="n">i</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="n">i</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>do-while</code>循环和<code>while</code>循环相似。对于<code>while</code>循环如果条件一开始不满足，循环体可能一次也不会执行，而<code>do-while</code>循环它会先执行一次循环体，然后再检查条件。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">i</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34; ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">--</span><span class="n">i</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>while</code>循环、<code>do-while</code>循环和for循环是Java中的三种常见循环结构。在大多数情况下，性能差异可以忽略不计，代码的清晰和易读性才是关键。</p>
+<ul>
+<li><code>while</code>循环：用于在满足条件前可能不执行循环体的情况；</li>
+<li><code>do-while</code>循环：用于至少需要执行一次循环体的情况；</li>
+<li>for循环：用于已知循环次数或需要固定迭代次数的情况；</li>
+</ul>
+<h2 id="参数传递">参数传递</h2>
+<p>对于基本数据类型（如int、char、float等），值传递意味着传递的是变量的副本，是值传递。
+如果是对象，那就是引用传递，这个理解是错误的。</p>
+<p>形式参数与实际参数：</p>
+<ul>
+<li>形式参数：是在定义函数名和函数体的时候使用的参数，目的是用来接收调用该函数时传入的参数；</li>
+<li>实际参数：在调用有参函数时，主调函数和被调函数之间有数据传递关系。在主调函数中调用一个函数时，函数名后面括号中的参数称为“实际参数”；</li>
+</ul>
+<p>举个例子：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HelloWorld</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 实参 </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">test</span><span class="p">(</span><span class="s">&#34;world&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 形参</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">param</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;hello &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">param</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>值传递与引用传递：</p>
+<ul>
+<li>值传递: 是指在调用函数时将实际参数复制一份传递到函数中，这样在函数中如果对参数进行修改，将不会影响到实际参数；</li>
+<li>引用传递: 是指在调用函数时将实际参数的地址直接传递到函数中，那么在函数中对参数所进行的修改，将影响到实际参数；</li>
+</ul>
+<table>
+<thead>
+<tr>
+<th></th>
+<th>值传递</th>
+<th>引用传递</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>区别</td>
+<td>传参时会创建副本</td>
+<td>传参数不创建副本</td>
+</tr>
+<tr>
+<td>描述</td>
+<td>方法中无法修改原始对象</td>
+<td>方法中可以修改原始对象</td>
+</tr>
+</tbody>
+</table>
+<p>举个例子，如果在方法中改变对象的字段值会改变原对象该字段值，因为改变的是同一个地址指向的内容。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">PassByValueExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Dog</span><span class="w"> </span><span class="n">dog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">func</span><span class="p">(</span><span class="n">dog</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">dog</span><span class="p">.</span><span class="na">getName</span><span class="p">());</span><span class="w">          </span><span class="c1">// B</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func</span><span class="p">(</span><span class="n">Dog</span><span class="w"> </span><span class="n">dog</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dog</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">);</span><span class="c1">//dog.name=&#34;B&#34;;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>然后有人就说Java传递对象类型参数是引用传递，其实这一点在官方<a href="https://docs.oracle.com/javase/tutorial/java/javaOO/arguments.html">《Java™教程》</a>中有相关的描述。</p>
+<blockquote>
+<p>Passing Reference Data Type Arguments.
+Reference data type parameters, such as objects, are also passed into methods by value. This means that when the method returns, the passed-in reference still references the same object as before. However, the values of the object&rsquo;s fields can be changed in the method, if they have the proper access level.<br></p>
+</blockquote>
+<p>文档大意：
+传递引用数据类型参数，引用数据类型参数(如对象)也按值传递给方法。
+这意味着当方法返回时，传入的引用仍然引用与之前相同的对象，但是如果对象的字段具有适当的访问级别，则可以在方法中更改它们的值。</p>
+<p>所以在Java中的参数传递确实是值传递，但在处理对象引用时，表现出的行为可能让人误以为是引用传递。
+举个例子来更好的理解：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyObject</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PassByValueExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">MyObject</span><span class="w"> </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">modifyObject</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After method call: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="p">);</span><span class="w">  </span><span class="c1">// 输出: 20</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">resetObject</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After resetObject call: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="p">);</span><span class="w">  </span><span class="c1">// 输出: 20</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">modifyObject</span><span class="p">(</span><span class="n">MyObject</span><span class="w"> </span><span class="n">obj</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w">  </span><span class="c1">// 修改对象的属性，会影响原对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">resetObject</span><span class="p">(</span><span class="n">MyObject</span><span class="w"> </span><span class="n">obj</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">();</span><span class="w">  </span><span class="c1">// 修改的是引用的副本，不影响原引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">30</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>值传递和引用传递最大的区别是，传递的过程中有没有复制出一个副本来，如果是传递副本，那就是值传递，否则就是引用传递。
+在Java中，其实是通过值传递实现的参数传递，只不过对于Java对象的传递，传递的内容是对象的引用的副本。
+所以Java的参数是以值传递的形式传入方法中，而不是引用传递。
+Java对象的传递，是通过复制的方式把引用关系传递了。如果我们没有改引用关系，而是找到引用的地址，把里面的内容改了，是会对调用方有影响的，因为大家指向的是同一个共享地址。</p>
+<h2 id="浮点类精度问题">浮点类精度问题</h2>
+<p>在Java中，使用浮点类型进行计算会造成精度丢失。例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 0.20000005</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 0.19999999999999996</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2d</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那么为什么浮点类型会存在精度精度丢失问题呢？
+因为Java的浮点类型在计算机中是用二进制来存储的，也就是小数在转二进制的时候出现了精度丢失。</p>
+<p>小数如何转二进制？
+将待转的数字乘以2，取出整数部分作为二进制表示的第1位，然后再将小数部分乘以2，将得到的整数部分作为二进制表示的第2位，以此类推，直到小数部分为0。
+特殊情况，如果小数部分出现循环，无法停止，则用有限的二进制位无法准确表示一个小数，这也是在编程语言中表示小数会出现误差的原因。
+例如，0.1转二进制：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0.1 x 2 = 0.2  取整数位 0
+</span></span><span class="line"><span class="cl">0.2 x 2 = 0.4  取整数位 0
+</span></span><span class="line"><span class="cl">0.4 x 2 = 0.8  取整数位 0
+</span></span><span class="line"><span class="cl">0.8 x 2 = 1.6  取整数位 1
+</span></span><span class="line"><span class="cl">0.6 x 2 = 1.2  取整数位 1
+</span></span><span class="line"><span class="cl">0.2 x 2 = 0.4  取整数位 0
+</span></span><span class="line"><span class="cl">0.4 x 2 = 0.8  取整数位 0
+</span></span><span class="line"><span class="cl">0.8 x 2 = 1.6  取整数位 1
+</span></span><span class="line"><span class="cl">0.6 x 2 = 1.2  取整数位 1
+</span></span><span class="line"><span class="cl">........无限循环
+</span></span></code></pre></div><p>因为计算机中存储一个浮点类型所用的位数是有限的，所以遇到无限循环的小数，只能选择在某个精度进行保存。
+由于计算机中保存的小数其实是十进制的小数的近似值，并不是准确值，所以，千万不要在代码中使用浮点数来表示金额等重要的指标。</p>
+<p>那怎么解决浮点精度丢失问题？
+Java中的<code>BigDecimal</code>类提供了精确的十进制数学运算，避免了浮点数精度丢失的问题。
+<code>BigDecimal</code>能够保证精度主要因为它基于十进制表示和算术运算，避免了二进制浮点数在表示和计算小数时可能出现的舍入误差和精度问题。</p>
+<h2 id="bigdecimal">BigDecimal</h2>
+<p>Java在<code>java.math</code>包中提供的API类<code>BigDecimal</code>，用来对超过16位有效位的数进行精确的运算。
+双精度浮点型变量<code>double</code>可以处理16位有效数，在实际应用中，需要对更大或者更小的数进行运算和处理，所以需要用到<code>BigDecimal</code>。</p>
+<p>Java中提供了大数字(超过16位有效位)的操作类，即<code>java.math.BinInteger</code>类和<code>java.math.BigDecimal</code>类，用于高精度计算。
+其中<code>BigInteger</code>类是针对大整数的处理类，而<code>BigDecimal</code>类则是针对大小数的处理类。<code>BigDecimal</code>类的实现用到了<code>BigIntege</code>类，不同的是<code>BigDecimal</code>加入了小数的概念。</p>
+<h3 id="基本用法">基本用法</h3>
+<p><code>BigDecimal</code>一共有两种方法可以进行初始化赋值，构造器初始化赋值，<code>valueOf</code>方法初始化赋值。
+在使用<code>BigDecimal</code>中参数为<code>double</code>类型的构造器时，发现存储结果并不准确。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 打印结果: 0.200000000000000011102230246251565404236316680908203125</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="n">0</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>找到Java API中的相关描述：</p>
+<blockquote>
+<p>The results of this constructor can be somewhat unpredictable.
+One might assume that writing {@code new BigDecimal(0.1)} in Java creates a {@code BigDecimal} which is exactly equal to 0.1 (an unscaled value of 1, with a scale of 1), but it is actually equal to 0.1000000000000000055511151231257827021181583404541015625.
+This is because 0.1 cannot be represented exactly as a {@code double} (or, for that matter, as a binary fraction of any finite length).<br>
+Thus, the value that is being passed<i>in</i> to the constructor is not exactly equal to 0.1, appearances notwithstanding.<br>
+The {@code String} constructor, on the other hand, is perfectly predictable: writing {@code new BigDecimal(&ldquo;0.1&rdquo;)} creates a {@code BigDecimal} which is <i>exactly</i> equal to 0.1, as one would expect.  Therefore, it is generally recommended that the {@linkplain #BigDecimal(String)<tt>String</tt> constructor} be used in preference to this one.</p>
+</blockquote>
+<p>大概意思是说，用<code>double</code>作为参数的构造函数，无法精确构造一个<code>BigDecimal</code>对象，需要自己指定一个上下文的环境，也就是指定精确位。
+而利用<code>String</code>对象作为参数传入的构造函数能精确的构造出一个<code>BigDecimal</code>对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 0.2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;0.2&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>所以要想获得精确的结果，要使用<code>BigDecimal</code>的字符串构造函数，不要使用<code>double</code>参数的构造函数。</p>
+<p><code>BigDecimal</code>所创建的是对象，我们不能使用传统的<code>+、-、*、/</code>等算术运算符直接对其对象进行数学运算，而必须调用其相对应的方法。
+方法中的参数也必须是<code>BigDecimal</code>的对象，构造器是类的特殊方法，专门用来创建对象，特别是带有参数的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 + num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">subtract</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 - num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">multiply</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 * num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">divide</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 / num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 绝对值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;|num1 / num2| = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">.</span><span class="na">abs</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>另外说一下<code>BigDecimal</code>如何转换其他类型。
+<code>BigDecimal</code>类提供了<code>intValue</code>,<code>byteValue</code>,<code>shortValue</code>等将<code>BigDecimal</code>对象转换成对应类型的方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">bigDecimal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">byteValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">shortValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">intValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">floatValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">doubleValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">longValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="舍入规则">舍入规则</h3>
+<p>在使用除法的时候如果两个数字，除不尽而又没有设置精确小数位和舍入模式，就会报错：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">divide</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 / num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Exception in thread &#34;main&#34; java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.
+</span></span></code></pre></div><p>为了防止报错，我们可以这样写：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">divide</span><span class="p">(</span><span class="n">num2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">.</span><span class="na">ROUND_UP</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 打印结果: num1 / num2 = 0.334</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 / num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>BigDecimal</code>类<code>divide</code>方法中<code>roundingMode</code>参数为舍入规则，如果不指定默认采用则四舍五入方式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// divisor: 除数; scale: 精确小数位; roundingMode: 舍入规则</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">BigDecimal</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">divisor</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">scale</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">roundingMode</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p><code>BigDecimal</code>类在进行数值运算时，可以通过指定不同的舍入规则来控制计算结果的精确度和舍入方式。
+舍入规则由<code>RoundingMode</code>枚举类定义，Java 提供了几种常见的舍入模式，每种模式都适用于不同的应用场景和需求，我们在使用<code>BigDecimal</code>除法的时候，最好要指定精确小数位和舍入模式。</p>
+<ul>
+<li><code>RoundingMode.UP</code>：向正无穷方向舍入，即始终向远离零的方向舍入。例如，对 <code>3.14</code> 使用 <code>UP</code> 模式舍入结果为 <code>4</code>。</li>
+<li><code>RoundingMode.DOWN</code>：向零方向舍入，即截断小数部分。例如，对 <code>3.14</code> 使用 <code>DOWN</code> 模式舍入结果为 <code>3</code>。</li>
+<li><code>RoundingMode.CEILING</code>：向正无穷方向舍入，如果是正数则表现和 <code>UP</code> 一样，如果是负数则表现和 <code>DOWN</code> 一样。例如，对 <code>-3.14</code> 使用 <code>CEILING</code> 模式舍入结果为 <code>-3</code>；对 <code>3.14</code> 使用 <code>CEILING</code> 模式舍入结果为 <code>4</code>。</li>
+<li><code>RoundingMode.FLOOR</code>：向负无穷方向舍入，如果是正数则表现和 <code>DOWN</code> 一样，如果是负数则表现和 <code>UP</code> 一样。例如，对 <code>-3.14</code> 使用 <code>FLOOR</code> 模式舍入结果为 <code>-4</code>；对 <code>3.14</code> 使用 <code>FLOOR</code> 模式舍入结果为 <code>3</code>。</li>
+<li><code>RoundingMode.HALF_UP</code>：四舍五入，当舍弃部分 &gt;= 0.5 时，舍入行为同 <code>UP</code>；否则，舍入行为同 <code>DOWN</code>。例如，对 <code>3.5</code> 使用 <code>HALF_UP</code> 模式舍入结果为 <code>4</code>；对 <code>3.4</code> 使用 <code>HALF_UP</code> 模式舍入结果为 <code>3</code>。</li>
+<li><code>RoundingMode.HALF_DOWN</code>：四舍五入，当舍弃部分 &gt; 0.5 时，舍入行为同 <code>UP</code>；否则，舍入行为同 <code>DOWN</code>。例如，对 <code>3.5</code> 使用 <code>HALF_DOWN</code> 模式舍入结果为 <code>3</code>；对 <code>3.4</code> 使用 <code>HALF_DOWN</code> 模式舍入结果为 <code>3</code>。</li>
+<li><code>RoundingMode.HALF_EVEN</code>：银行家舍入法，当舍弃部分等于 0.5 时，舍入行为同 <code>HALF_UP</code>；否则，舍入行为同 <code>HALF_DOWN</code>。例如，对 <code>2.5</code> 使用 <code>HALF_EVEN</code> 模式舍入结果为 <code>2</code>；对 <code>3.5</code> 使用 <code>HALF_EVEN</code> 模式舍入结果为 <code>4</code>。</li>
+<li><code>RoundingMode.UNNECESSARY</code>：不需要舍入，如果计算结果需要舍入，则抛出 <code>ArithmeticException</code> 异常。</li>
+</ul>
+<h3 id="scale属性">scale属性</h3>
+<p><code>BigDecimal</code>对象中<code>scale</code>字段属性，指的是小数点后面的位数，比如，对于<code>BigDecimal</code>值 123.45，<code>scale</code>是 2。</p>
+<p><code>setScale</code>可以增加或减少<code>BigDecimal</code>的小数位数。
+当增加小数位数时，新增加的位数会被填充为零。当减少小数位数时，多余的位数会被舍去，并根据指定的舍入模式进行舍入。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BigDecimalSetScaleExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;123.4567&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 增加 scale</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">increasedScale</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">.</span><span class="na">setScale</span><span class="p">(</span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">RoundingMode</span><span class="p">.</span><span class="na">UNNECESSARY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Increased scale: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">increasedScale</span><span class="p">);</span><span class="w"> </span><span class="c1">// 123.456700</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 减少 scale，并使用四舍五入模式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">decreasedScale</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">.</span><span class="na">setScale</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">RoundingMode</span><span class="p">.</span><span class="na">HALF_UP</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Decreased scale: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">decreasedScale</span><span class="p">);</span><span class="w"> </span><span class="c1">// 123.46</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 减少 scale，并使用向下舍入模式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">decreasedScaleDown</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">.</span><span class="na">setScale</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">RoundingMode</span><span class="p">.</span><span class="na">DOWN</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Decreased scale (down): &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">decreasedScaleDown</span><span class="p">);</span><span class="w"> </span><span class="c1">// 123.45</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>setScale</code>方法用于设置<code>BigDecimal</code>对象的<code>scale</code>，并且可以指定舍入模式。
+在设置新的<code>scale</code>时，如果不指定舍入模式且新的<code>scale</code>小于当前<code>scale</code>，则会抛出<code>ArithmeticException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.12345&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num1</span><span class="p">.</span><span class="na">setScale</span><span class="p">(</span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">num1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">java.lang.ArithmeticException: Rounding necessary
+</span></span></code></pre></div><h3 id="比较大小">比较大小</h3>
+<p>使用<code>BigDecimal</code>进行比较操作需要特别注意，因为<code>BigDecimal</code>是用于精确计算的数据类型，不能像基本数据类型一样直接使用比较操作符，如 <code>&lt;, &gt;, ==</code>来比较。
+可以用<code>BigDecimal</code>的<code>equals</code>方法来进行比较。这里要注意，<code>equals</code>方法会比较数值和精度是否完全相同，即使两个对象表示的是相同的数值但精度不同，也会返回<code>false</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.10&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// false</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">num1</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">num2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">num2</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">num3</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>可以看到<code>1.10</code>和<code>1.1</code>数值是相等的，而<code>equals</code>方法返回的却是<code>false</code>。看一下<code>BigDecimal</code>中重写的<code>equals</code>的源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Compares this {@code BigDecimal} with the specified
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * {@code Object} for equality.  Unlike {@link
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * #compareTo(BigDecimal) compareTo}, this method considers two
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * {@code BigDecimal} objects equal only if they are equal in
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * value and scale (thus 2.0 is not equal to 2.00 when compared by
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * this method).
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @param  x {@code Object} to which this {@code BigDecimal} is
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *         to be compared.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @return {@code true} if and only if the specified {@code Object} is a
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *         {@code BigDecimal} whose value and scale are equal to this
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *         {@code BigDecimal}&#39;s.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @see    #compareTo(java.math.BigDecimal)
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @see    #hashCode
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">x</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">xDec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">BigDecimal</span><span class="p">)</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="k">this</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">scale</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">xDec</span><span class="p">.</span><span class="na">scale</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">long</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">intCompact</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">long</span><span class="w"> </span><span class="n">xs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xDec</span><span class="p">.</span><span class="na">intCompact</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">INFLATED</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">xs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">INFLATED</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">xs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">compactValFor</span><span class="p">(</span><span class="n">xDec</span><span class="p">.</span><span class="na">intVal</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">xs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">xs</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">INFLATED</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">xs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">compactValFor</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">intVal</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">inflated</span><span class="p">().</span><span class="na">equals</span><span class="p">(</span><span class="n">xDec</span><span class="p">.</span><span class="na">inflated</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>文档中有这么一段描述：</p>
+<blockquote>
+<p>objects equal only if they are equal in value and scale. thus 2.0 is not equal to 2.00 when compared by this method</p>
+</blockquote>
+<p>大意：对象只有在<code>value</code>和<code>scale</code>相等时才相等。因此，用本方法比较时，2.0不等于2.00。</p>
+<p>所以不要用<code>equals</code>方法来比较<code>BigDecimal</code>对象，因为它的<code>equals</code>方法会比较<code>scale</code>，如果<code>scale</code>不一样，它会返回<code>false</code>。
+如果需要比较数值相等，不考虑精度，可以使用<code>compareTo</code>方法进行比较，并判断返回的结果是否为0。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.10&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a小于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a等于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a大于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a大于等于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a小于等于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="math">Math</h2>
+<p><code>java.lang.Math</code>，该类和Java中的运算息息相关。<code>Math</code>类是一个工具类，被<code>final</code>修饰，构造方法是私有的，大部分方法都被<code>public static</code>修饰。</p>
+<p>基本用法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 计算平方根</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;4的平方根: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">sqrt</span><span class="p">(</span><span class="n">4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">//计算立方根</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;8的立方根: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">cbrt</span><span class="p">(</span><span class="n">8</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 计算n的m次方</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;2的3次方: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">pow</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 计算最大值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1和2中最大值: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 计算最小值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1和2中最小值: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 求绝对值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;-1的绝对值: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">abs</span><span class="p">(</span><span class="o">-</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 向上取整</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1.2向上取整: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 向下取整</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1.2向下取整: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">floor</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// [0,1)区间的随机数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;[0,1)区间的随机数: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 返回与参数值最接近的 double值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kt">double</span><span class="w"> </span><span class="n">rint</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">rint</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;rint方法: %s\n&#34;</span><span class="p">,</span><span class="n">rint</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 四舍五入 float时返回int值，double时返回long值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kt">long</span><span class="w"> </span><span class="n">round</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">round1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5f</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;round方法: 1.5四舍五入: %s\n&#34;</span><span class="p">,</span><span class="n">round</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="ceil和floor">ceil和floor</h3>
+<p><code>ceil</code>方法的功能是向上取整。<code>ceil</code>译为“天花板”，顾名思义就是对操作数取顶，<code>Math.ceil(a)</code>就是取大于a的最小整数。
+需要注意的是它的返回值不是<code>int</code>类型，而是<code>double</code>类型。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 向上取整</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1.2向上取整: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span></code></pre></div><p><code>floor</code>方法的功能是向下取整。<code>floor</code>译为“地板”，顾名思义是对操作数取底。
+<code>Math.floor(a)</code>，就会取小于a的最大整数。它的返回值类型与<code>ceil</code>一致，也是<code>double</code>类型。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 向下取整</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1.2向下取整: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">floor</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span></code></pre></div><p>一般情况下，<code>Math.ceil(x)</code>的值正好是<code>-Math.floor(-x)</code>的值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Math.ceil(1.2) = 2.0
+</span></span><span class="line"><span class="cl">-Math.floor(-1.2) = 2.0
+</span></span></code></pre></div><p>特殊情况：</p>
+<ul>
+<li>如果参数值已经等于一个数学整数，则结果与参数相同。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">double</span><span class="w"> </span><span class="n">result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">2</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(2.0): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result1</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 2.0</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>如果参数是NaN或无穷大或正零或负零，则结果与参数相同。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">double</span><span class="w"> </span><span class="n">result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">Double</span><span class="p">.</span><span class="na">NaN</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(Double.NaN): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 NaN</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">result5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">0</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(0.0): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result5</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 0.0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">result6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="o">-</span><span class="n">0</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(-0.0): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result6</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 -0.0</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>如果实参值小于零但大于-1.0，则结果为负零。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">double</span><span class="w"> </span><span class="n">result7</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="o">-</span><span class="n">0</span><span class="p">.</span><span class="na">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(-0.5): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result7</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 -0.0</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="random">random</h3>
+<p><code>random</code>方法是 Java 中用于生成伪随机数的基本方法之一。它返回一个<code>double</code>类型的随机数，范围在<code>[0.0, 1.0)</code>，包括0.0但不包括1.0。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">RandomExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 生成一个 0.0 到 1.0 之间的随机数（不包括 1.0）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">double</span><span class="w"> </span><span class="n">randomValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;随机数: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">randomValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>由于<code>random</code>方法生成的是<code>[0.0, 1.0)</code>之间的随机数，可以通过数学运算将其转换为不同范围的随机数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">RandomExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">15</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">randomInt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">min</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p">((</span><span class="n">max</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">min</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%d 到 %d 之间的随机整数: %d\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">min</span><span class="p">,</span><span class="w"> </span><span class="n">max</span><span class="p">,</span><span class="w"> </span><span class="n">randomInt</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>通过源码可以看到，<code>Math.random</code>底层是调用了<code>Random</code>类中<code>nextDouble</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">random</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">RandomNumberGeneratorHolder</span><span class="p">.</span><span class="na">randomNumberGenerator</span><span class="p">.</span><span class="na">nextDouble</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// Random.nextDouble</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">nextDouble</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="p">(((</span><span class="kt">long</span><span class="p">)(</span><span class="n">next</span><span class="p">(</span><span class="n">26</span><span class="p">))</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">27</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">next</span><span class="p">(</span><span class="n">27</span><span class="p">))</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">DOUBLE_UNIT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>也就是说以下代码执行的逻辑是相同的：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// [0,1)区间的随机数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;[0,1)区间的随机数: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;[0,1)区间的随机数: %s\n&#34;</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">Random</span><span class="p">().</span><span class="na">nextDouble</span><span class="p">());</span><span class="w">
+</span></span></span></code></pre></div><p><code>Random</code>类位于<code>java.util</code>包下，此类的实例用于生成伪随机数流。
+之所以称之为伪随机，是因为真正意义上的随机数（或者称为随机事件）在某次产生过程中是按照实验过程表现的分布概率随机产生的，其结果是不可预测，不可见的。
+而计算机中的随机函数是按照一定的算法模拟产生的，其结果是确定的，可见的。我们认为这样产生的数据不是真正意义上的随机数，因而称之为伪随机。</p>
+<p>该类提供了两种构造方法，无参构造底层调用的也是有参构造。
+将<code>System.nanoTime()</code>作为参数传递。如果使用无参构造，默认的<code>seed</code>值为<code>System.nanoTime()</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 无参构造</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">Random</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="k">this</span><span class="p">(</span><span class="n">seedUniquifier</span><span class="p">()</span><span class="w"> </span><span class="o">^</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 有参构造</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">Random</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">seed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">getClass</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Random</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">seed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicLong</span><span class="p">(</span><span class="n">initialScramble</span><span class="p">(</span><span class="n">seed</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// subclass might have overriden setSeed</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">seed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicLong</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">setSeed</span><span class="p">(</span><span class="n">seed</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>要注意的是用有参构造创建<code>Random</code>对象，如果随机种子相同，不管执行多少次，最后结果都是相同的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Random</span><span class="w"> </span><span class="n">random</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Random</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 第一次执行程序打印结果: 随机数: -1155869325</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 第二次执行程序打印结果: 随机数: -1155869325</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;随机数: %s\n&#34;</span><span class="p">,</span><span class="n">random</span><span class="p">.</span><span class="na">nextInt</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="round">round</h3>
+<p><code>round</code>方法用于对浮点数进行四舍五入，并返回最接近的整数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 四舍五入 float时返回int值，double时返回long值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">round</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">round1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5f</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;round方法: 1.5四舍五入: %s\n&#34;</span><span class="p">,</span><span class="n">round</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p>一般情况，<code>round</code>方法用于对浮点数进行四舍五入，并返回最接近的整数。特殊情况:</p>
+<ul>
+<li>如果参数是NaN，结果是0；NaN表示非数值，例如：0.0/0结果为NAN，负数的平方根结果也为NAN；</li>
+<li>如果参数是负无穷大或小于或等于<code>Integer.MIN_VALUE</code>，结果为<code>Integer.MIN_VALUE</code>；</li>
+<li>如果参数是正无穷大或大于或等于<code>Integer.MAX_VALUE</code>，结果为<code>Integer.MAX_VALUE</code>；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 四舍五入 float时返回int值，double时返回long值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">round1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">long</span><span class="w"> </span><span class="n">round2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">Double</span><span class="p">.</span><span class="na">NaN</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">round3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">2147483648123L</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">round4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="o">-</span><span class="n">2147483647123L</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;0四舍五入: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">round1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Double.NaN=[%s],四舍五入: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">NaN</span><span class="p">,</span><span class="w"> </span><span class="n">round2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Integer.MAX_VALUE=[%s] + 1 四舍五入: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">,</span><span class="w"> </span><span class="n">round3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Integer.MIN_VALUE=[%s] - 1 四舍五入: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MIN_VALUE</span><span class="p">,</span><span class="w"> </span><span class="n">round4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Math.round()</code>和<code>BigDecimal</code>类的四舍五入方法在实现和使用上有一些显著的区别。
+<code>Math.round()</code>适用于对普通的浮点数进行简单的整数舍入，例如将浮点数转换为最接近的整数值。
+<code>BigDecimal.setScale()</code>适用于需要精确控制数值精度和舍入方式的场景，特别是在金融计算、税务计算等要求高精度和可预测舍入行为的应用中。</p>
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+        
+        
+        
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+        
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+                    反射原理
+                </a>
+            </li>
+            
+            
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+                    反射应用场景
+                </a>
+            </li>
+            
+            
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+        
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+                    反射与注解
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+        
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+                    反射与枚举
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+        
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+                    反射与泛型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+                </a>
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+        
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+        
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+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Java反射</h2>
+                        <span id="post_page_title_date" class="date">2021.10.02</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概述">概述</h2>
+<p>在Java程序运行状态中，对于任意一个实体类，都能够知道这个类的所有属性和方法，对于任意一个对象，都能够调用它的任意方法和属性。这种动态获取信息以及动态调用对象方法的功能，称为Java语言的反射机制。</p>
+<p>反射是Java语言的一个特性，它允许程序在运行时来进行自我检查并且对内部的成员进行操作。通过反射，我们可以在运行时获得程序或程序集中每一个类型的成员和成员的信息。
+程序中一般的对象的类型都是在编译期就确定下来的，而Java反射机制可以动态地创建对象并调用其属性，这样的对象的类型在编译期是未知的。
+反射的核心是JVM在运行时动态加载类或调用方法、访问属性，它不需要事先知道运行对象是谁。本质是JVM得到<code>class</code>对象之后，再通过<code>class</code>对象进行反编译，从而获取对象的各种信息。</p>
+<h2 id="反射入口">反射入口</h2>
+<p>在操作反射前我们要先了解一些Class类。Java的<code>Class</code>类是java反射机制的基础，通过<code>Class</code>类我们可以获得关于一个类的相关信息。
+虚拟机为每种类型管理一个独一无二的<code>Class</code>对象，也就是说每个类都有一个<code>Class</code>对象。运行程序时，Java虚拟机首先检查是否所要加载的类对应的<code>Class</code>对象是否已经加载。
+如果没有加载，JVM就会根据类名查找<code>.class</code>文件，并将其<code>Class</code>对象载入。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w">  </span><span class="nf">Class</span><span class="p">(</span><span class="n">ClassLoader</span><span class="w"> </span><span class="n">loader</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">classLoader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">loader</span><span class="p">;</span><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Class</code>类的构造器是私有的，只有JVM可以创建<code>Class</code>的对象。因此不可以像普通类一样<code>new</code>一个<code>Class</code>对象，但是却可以通过已有的类得到一个<code>Class</code>对象。
+在运行时获取<code>Class</code>的对象，共有三种方式：</p>
+<ol>
+<li>通过<code>Class.forName()</code>方法。这种方式使用类的全限定名（包名+类名）来获取<code>Class</code>对象，常用于动态加载类。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    Class&lt;?&gt; clazz = Class.forName(&#34;com.example.MyClass&#34;);
+</span></span><span class="line"><span class="cl">} catch (ClassNotFoundException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>通过类的<code>.class</code>属性。这种方式在编译时就已经知道类的类型，适用于静态加载类。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MyClass</span><span class="p">.</span><span class="na">class</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>通过对象的<code>getClass()</code>方法。这种方式通过已知对象来获取它的<code>Class</code>对象。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">MyClass</span><span class="w"> </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">obj</span><span class="p">.</span><span class="na">getClass</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<h2 id="操作反射">操作反射</h2>
+<p>在Java中，只要给定类的名字，就可以通过反射机制来获得类的所有信息、调用方法、访问和修改属性等操作。
+反射使得程序可以在运行时检查类的结构和行为，而不需要在编译时知道类的具体信息。使用反射会有异常出现，注意处理异常。Java中<code>Class</code>类和<code>java.lang.reflect</code>一起对反射提供了支持。</p>
+<ul>
+<li>反射可以获取类的完整信息，包括类名、包名、父类、接口、构造函数、字段和方法等。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Class&lt;?&gt; clazz = Class.forName(&#34;java.util.ArrayList&#34;);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取类名
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Class Name: &#34; + clazz.getName());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取包名
+</span></span><span class="line"><span class="cl">Package pkg = clazz.getPackage();
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Package Name: &#34; + pkg.getName());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取所有构造函数
+</span></span><span class="line"><span class="cl">Constructor&lt;?&gt;[] constructors = clazz.getConstructors();
+</span></span><span class="line"><span class="cl">for (Constructor&lt;?&gt; constructor : constructors) {
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Constructor: &#34; + constructor);
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取所有方法
+</span></span><span class="line"><span class="cl">Method[] methods = clazz.getMethods();
+</span></span><span class="line"><span class="cl">for (Method method : methods) {
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Method: &#34; + method.getName());
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取所有字段
+</span></span><span class="line"><span class="cl">Field[] fields = clazz.getDeclaredFields();
+</span></span><span class="line"><span class="cl">for (Field field : fields) {
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Field: &#34; + field.getName());
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>反射可以在运行时创建类的实例，而不需要在编译时知道类的名字。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Class&lt;?&gt; clazz = Class.forName(&#34;java.util.ArrayList&#34;);
+</span></span><span class="line"><span class="cl">Constructor&lt;?&gt; constructor = clazz.getConstructor();
+</span></span><span class="line"><span class="cl">Object instance = constructor.newInstance();
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Instance: &#34; + instance);
+</span></span></code></pre></div></li>
+<li>反射允许在运行时访问和修改对象的字段，即使字段是私有的。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Class&lt;?&gt; clazz = Class.forName(&#34;com.example.Person&#34;);
+</span></span><span class="line"><span class="cl">Object person = clazz.getConstructor().newInstance();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取私有字段
+</span></span><span class="line"><span class="cl">Field nameField = clazz.getDeclaredField(&#34;name&#34;);
+</span></span><span class="line"><span class="cl">nameField.setAccessible(true);  // 允许访问私有字段
+</span></span><span class="line"><span class="cl">nameField.set(person, &#34;John Doe&#34;);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取字段值
+</span></span><span class="line"><span class="cl">String name = (String) nameField.get(person);
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Name: &#34; + name);
+</span></span></code></pre></div></li>
+<li>反射可以在运行时调用对象的方法，包括私有方法。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Class&lt;?&gt; clazz = Class.forName(&#34;com.example.Person&#34;);
+</span></span><span class="line"><span class="cl">Object person = clazz.getConstructor().newInstance();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取方法
+</span></span><span class="line"><span class="cl">Method setNameMethod = clazz.getMethod(&#34;setName&#34;, String.class);
+</span></span><span class="line"><span class="cl">Method getNameMethod = clazz.getMethod(&#34;getName&#34;);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 调用方法
+</span></span><span class="line"><span class="cl">setNameMethod.invoke(person, &#34;Jane Doe&#34;);
+</span></span><span class="line"><span class="cl">String name = (String) getNameMethod.invoke(person);
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Name: &#34; + name);
+</span></span></code></pre></div></li>
+</ul>
+<h2 id="反射特点">反射特点</h2>
+<p>通过反射机制我们可以获得类的各种内容，进行反编译。对于Java这种先编译再运行的语言来说，反射机制可以使代码更加灵活，更加容易实现面向对象。</p>
+<ul>
+<li>反射允许在运行时动态加载类、创建对象、调用方法和访问属性，这使得程序具有更高的灵活性和动态性，可以根据运行时的需求来适应不同的情况。</li>
+<li>反射使得编写通用代码和框架变得更加容易。例如，许多框架和库（如Spring和Hibernate）利用反射来实现依赖注入、持久化等功能，从而提高了代码的复用性和可维护性。</li>
+<li>反射可以帮助解耦合，减少类之间的依赖关系。通过反射，可以在不知道具体类名的情况下操作对象，从而简化了系统的结构和设计。</li>
+</ul>
+<p>反射功能虽然强大，但不应任意使用。如果一个功能可以不用反射完成，那么最好就不用。</p>
+<ul>
+<li>性能开销 ：反射操作通常比直接调用要慢。因为反射调用涉及到动态查找方法、字段和进行安全检查，这些步骤在运行时会带来额外的性能开销。在性能敏感的场景下，频繁使用反射可能会导致程序性能下降。</li>
+<li>安全限制 ：反射打破了Java语言的封装性和安全性，可以访问和修改私有成员，甚至可以执行敏感操作。因此在使用反射时需要格外注意安全性问题，避免不必要的暴露和风险。</li>
+<li>内部暴露 ：使用反射可以使代码更加复杂和难以理解。反射操作的代码通常比直接调用的代码更加复杂，可读性较差，可能增加代码维护的困难。</li>
+</ul>
+<h2 id="反射性能">反射性能</h2>
+<p>Java反射机制提供了一种在运行时动态操作类、方法和属性的强大能力。这使得反射成为许多框架和库的基础，如<code>Spring</code>和<code>Hibernate</code>。然而反射的灵活性是有代价的，反射操作通常比直接调用要慢得多。
+以下是一个比较直接方法调用和反射调用性能的示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReflectionPerformanceTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MyClass</span><span class="w"> </span><span class="n">myClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MyClass</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;myMethod&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">iterations</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1000000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 直接调用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">startTime</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">iterations</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">myClass</span><span class="p">.</span><span class="na">myMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">endTime</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">directCallDuration</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">endTime</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">startTime</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Direct call duration: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">directCallDuration</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; ns&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 反射调用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">startTime</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">iterations</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">myClass</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">endTime</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">reflectionCallDuration</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">endTime</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">startTime</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Reflection call duration: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">reflectionCallDuration</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; ns&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Some operation</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>反射慢的主要原因是在于它绕过了编译时的优化，并且在运行时需要动态查找类信息和进行安全性检查，导致额外的性能开销。</p>
+<ol>
+<li>绕过编译时优化： Java编译器可以在编译时对代码进行优化，如方法内联、常量折叠等，以提高执行效率。
+而反射调用是在运行时动态解析的，编译器无法对其进行类似的优化，导致执行速度相对较慢。</li>
+<li>动态查找和安全检查： 反射允许代码在运行时动态获取类的信息、调用方法和访问字段，甚至能够绕过访问控制。
+因此每次反射调用都需要在运行时进行类信息的查找和安全性检查，这些额外的步骤增加了方法调用的开销，使得反射相比直接调用更为缓慢。</li>
+</ol>
+<p>反射适合于那些需要在运行时动态加载类、调用未知类的方法或访问私有成员的情况。在性能要求严格的地方，尽量避免使用反射。
+如果需要多次反射调用，尽量将反射操作放在静态方法或静态初始化块中，来减少实例化对象的开销，避免重复的反射查找。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Method</span><span class="w"> </span><span class="n">myMethod</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">myMethod</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MyClass</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredMethod</span><span class="p">(</span><span class="s">&#34;methodName&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">myMethod</span><span class="p">.</span><span class="na">setAccessible</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w"> </span><span class="c1">// 如果是私有方法，需要设置访问权限</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">NoSuchMethodException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">invokeMyMethod</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InvocationTargetException</span><span class="p">,</span><span class="w"> </span><span class="n">IllegalAccessException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">myMethod</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="反射原理">反射原理</h2>
+<p>反射的核心是<code>java.lang.reflect</code>包，该包中包含了用于反射操作的类和接口，如<code>Class</code>、<code>Field</code>、<code>Method</code>、<code>Constructor</code>等。反射主要依赖于<code>Class</code>对象来进行操作。
+Java反射的本质是JVM得到<code>class</code>对象之后，再通过<code>class</code>对象进行&quot;反编译&quot;，从而获取对象的各种信息。描述反射为“反编译”可能不太准确，因为反射并不是将字节码重新转换为源代码。实际上，反射是在运行时通过Class对象来查询和操作已加载的类的结构信息。</p>
+<p>反射基本原理大致可分为以下几个步骤：</p>
+<ol>
+<li>JVM的类加载机制负责将类的字节码从不同的源，如<code>.class</code>文件、<code>JAR</code>包等，加载到内存中，并将其转化为可以在JVM上运行的Class对象。反射依赖于JVM的类加载机制来获取类的结构信息并进行操作。</li>
+<li>当使用反射时，首先需要获取类的Class对象。每个类在 JVM 中加载后，都会有一个对应的Class对象。这个对象包含了类的所有信息，包括类的结构（字段、方法、构造函数）、注解、泛型信息等。
+反射的第一步是获取这个Class对象，可以通过类名、对象实例的<code>getClass()</code>方法或者类的字面常量<code>.class</code>来获取。</li>
+<li>通过Class对象，可以使用反射API来访问类的字段、方法和构造函数。实际上，反射是在运行时通过Class对象来查询和操作已加载的类的结构信息。</li>
+<li>在具体实现上，Java反射依赖于<code>java.lang.reflect</code>包中的一系列类和接口。这些类和接口提供了访问和操作类结构的方法，例如<code>Field</code>、<code>Method</code>、<code>Constructor</code>等。</li>
+</ol>
+<h2 id="反射应用场景">反射应用场景</h2>
+<p>反射在Java编程中有广泛的应用场景。它主要用于动态加载类、运行时获取和操作类的信息，以及实现灵活的编程逻辑。
+通过反射，可以实现诸如依赖注入框架，如<code>Spring</code>、ORM框架，如<code>Hibernate</code>、动态代理、自定义注解处理器、插件化系统等功能。
+这些特性使得Java程序能够在运行时动态适应不同的需求和环境，提高了代码的灵活性和可维护性。</p>
+<h3 id="反射与注解">反射与注解</h3>
+<p>反射可以在运行时动态地获取和解析类、方法、字段上的注解信息。利用这个特性我们可以根据注解的内容来实现不同的逻辑，例如自定义的业务规则、权限控制等。</p>
+<p>反射在自定义注解处理器中特别有用，可以通过反射获取类、方法的信息，并根据注解信息生成代码或者进行其他处理。
+这种方式被广泛应用于框架和工具的开发中，例如<code>Spring</code>框架中的各种注解处理器。自定义一个注解体会一下。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 定义一个注解</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Retention</span><span class="p">(</span><span class="n">RetentionPolicy</span><span class="p">.</span><span class="na">RUNTIME</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Target</span><span class="p">(</span><span class="n">ElementType</span><span class="p">.</span><span class="na">METHOD</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@interface</span><span class="w"> </span><span class="n">MyAnnotation</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="nf">value</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用注解的类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@MyAnnotation</span><span class="p">(</span><span class="s">&#34;Hello Annotation&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Method with annotation&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReflectionAndAnnotationExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MyClass</span><span class="w"> </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">obj</span><span class="p">.</span><span class="na">getClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取方法上的注解信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">clazz</span><span class="p">.</span><span class="na">getDeclaredMethod</span><span class="p">(</span><span class="s">&#34;myMethod&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MyAnnotation</span><span class="w"> </span><span class="n">annotation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">method</span><span class="p">.</span><span class="na">getAnnotation</span><span class="p">(</span><span class="n">MyAnnotation</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">annotation</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Annotation value: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">annotation</span><span class="p">.</span><span class="na">value</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用反射调用带有注解的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="反射与枚举">反射与枚举</h3>
+<p>反射不能用于创建枚举类型的对象。因为枚举类型是单例的，每个枚举常量在Java虚拟机中只有一个实例。通过反射创建新的枚举实例会破坏枚举类型的单例性质。
+Java语言规范明确规定了枚举类型的创建和管理方式，禁止反射机制创建新的枚举实例，来确保枚举类型的安全性和一致性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">enum</span><span class="w"> </span><span class="n">Day</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SUNDAY</span><span class="p">,</span><span class="w"> </span><span class="n">MONDAY</span><span class="p">,</span><span class="w"> </span><span class="n">TUESDAY</span><span class="p">,</span><span class="w"> </span><span class="n">WEDNESDAY</span><span class="p">,</span><span class="w"> </span><span class="n">THURSDAY</span><span class="p">,</span><span class="w"> </span><span class="n">FRIDAY</span><span class="p">,</span><span class="w"> </span><span class="n">SATURDAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">EnumReflectionExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取枚举类型的构造方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Constructor</span><span class="o">&lt;</span><span class="n">Day</span><span class="o">&gt;</span><span class="w"> </span><span class="n">constructor</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Day</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredConstructor</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 尝试通过反射调用构造方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">constructor</span><span class="p">.</span><span class="na">setAccessible</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Day</span><span class="w"> </span><span class="n">newDay</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">constructor</span><span class="p">.</span><span class="na">newInstance</span><span class="p">(</span><span class="s">&#34;NEW_DAY&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;New Day: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">newDay</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 捕获并打印异常信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">java.lang.NoSuchMethodException: Day.&lt;init&gt;(java.lang.String, int)
+</span></span><span class="line"><span class="cl">    at java.lang.Class.getDeclaredConstructor0(Native Method)
+</span></span><span class="line"><span class="cl">    at java.lang.Class.getDeclaredConstructor(Class.java:2178)
+</span></span><span class="line"><span class="cl">    at EnumReflectionExample.main(EnumReflectionExample.java:11)
+</span></span></code></pre></div><p>具体的原因是在<code>Constructor</code>类中的<code>newInstance</code>方法，枚举类无法通过反射来创建对象，原因是<code>newInstance</code>方法加了判断如果是枚举类就抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@CallerSensitive</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">newInstance</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="p">...</span><span class="w"> </span><span class="n">initargs</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">throws</span><span class="w"> </span><span class="n">InstantiationException</span><span class="p">,</span><span class="w"> </span><span class="n">IllegalAccessException</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">           </span><span class="n">IllegalArgumentException</span><span class="p">,</span><span class="w"> </span><span class="n">InvocationTargetException</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">override</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">Reflection</span><span class="p">.</span><span class="na">quickCheckMemberAccess</span><span class="p">(</span><span class="n">clazz</span><span class="p">,</span><span class="w"> </span><span class="n">modifiers</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">caller</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Reflection</span><span class="p">.</span><span class="na">getCallerClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">checkAccess</span><span class="p">(</span><span class="n">caller</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">modifiers</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">clazz</span><span class="p">.</span><span class="na">getModifiers</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">Modifier</span><span class="p">.</span><span class="na">ENUM</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;Cannot reflectively create enum objects&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ConstructorAccessor</span><span class="w"> </span><span class="n">ca</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">constructorAccessor</span><span class="p">;</span><span class="w">   </span><span class="c1">// read volatile</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ca</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ca</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">acquireConstructorAccessor</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">T</span><span class="w"> </span><span class="n">inst</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="p">)</span><span class="w"> </span><span class="n">ca</span><span class="p">.</span><span class="na">newInstance</span><span class="p">(</span><span class="n">initargs</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">inst</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>除了不能创建枚举类的对象外，反射还是能够调用枚举类的方法的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">enum</span><span class="w"> </span><span class="n">Day</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SUNDAY</span><span class="p">,</span><span class="w"> </span><span class="n">MONDAY</span><span class="p">,</span><span class="w"> </span><span class="n">TUESDAY</span><span class="p">,</span><span class="w"> </span><span class="n">WEDNESDAY</span><span class="p">,</span><span class="w"> </span><span class="n">THURSDAY</span><span class="p">,</span><span class="w"> </span><span class="n">FRIDAY</span><span class="p">,</span><span class="w"> </span><span class="n">SATURDAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printMessage</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Today is &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">EnumReflectionExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取枚举常量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Day</span><span class="w"> </span><span class="n">day</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Day</span><span class="p">.</span><span class="na">SUNDAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取枚举类的 Class 对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">day</span><span class="p">.</span><span class="na">getClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并调用枚举类的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">clazz</span><span class="p">.</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;printMessage&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">day</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="反射与泛型">反射与泛型</h3>
+<p>Java中的泛型是通过类型擦除来实现的，这意味着泛型信息只在编译期间存在，而在运行时则被擦除。所以反射在运行时无法直接获取具体的泛型类型信息。</p>
+<p>类型擦除是Java泛型的一种实现机制，目的是保持与旧版本的兼容性。在编译过程中，泛型类型被替换为其非泛型上限，通常是<code>Object</code>类，并在需要时插入类型转换。
+这样Java编译器在编译期间进行类型检查，而在运行时不保留泛型类型信息。</p>
+<p>通过反射可以绕过Java泛型的类型检查，这利用了Java泛型的类型擦除机制。在编译时，泛型类型被擦除，实际操作的对象是原始类型<code>Object</code>。
+这使得在运行时可以向泛型集合中插入不同类型的元素。但这种做法会导致类型安全性问题，所以在实际开发中应谨慎使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">  </span><span class="c1">//这样调用 add 方法只能存储整形，因为泛型类型的实例为 Integer</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;add&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="p">.</span><span class="na">class</span><span class="p">).</span><span class="na">invoke</span><span class="p">(</span><span class="n">list</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;string&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="c1">// 1 string</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="反射与框架">反射与框架</h3>
+<p>反射在许多Java框架中起着至关重要的作用，它使得框架能够在运行时动态地操作对象、调用方法和访问字段。
+例如，Spring的核心功能之一是依赖注入，就是利用反射动态地创建和注入对象。Spring使用反射来调用构造函数、设置字段和调用方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">MyRepository</span><span class="w"> </span><span class="n">myRepository</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>@Autowired</code>注解文档注释上面，可以看到与之息息相关的一个类<code>AutowiredAnnotationBeanPostProcessor</code>，即<code>@Autowired</code>后置处理器。
+看到该类实现了<code>MergedBeanDefinitionPostProcessor</code>接口，在<code>postProcessMergedBeanDefinition</code>方法上打一个断点，就可以看到<code>@Autowired</code>的调用栈。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/*
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @see AutowiredAnnotationBeanPostProcessor
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Target</span><span class="p">({</span><span class="n">ElementType</span><span class="p">.</span><span class="na">CONSTRUCTOR</span><span class="p">,</span><span class="w"> </span><span class="n">ElementType</span><span class="p">.</span><span class="na">METHOD</span><span class="p">,</span><span class="w"> </span><span class="n">ElementType</span><span class="p">.</span><span class="na">PARAMETER</span><span class="p">,</span><span class="w"> </span><span class="n">ElementType</span><span class="p">.</span><span class="na">FIELD</span><span class="p">,</span><span class="w"> </span><span class="n">ElementType</span><span class="p">.</span><span class="na">ANNOTATION_TYPE</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Retention</span><span class="p">(</span><span class="n">RetentionPolicy</span><span class="p">.</span><span class="na">RUNTIME</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Documented</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nd">@interface</span><span class="w"> </span><span class="n">Autowired</span><span class="p">{}</span><span class="w">
+</span></span></span></code></pre></div><p><code>@Autowired</code>注解调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">AbstractApplicationContext.refresh(容器初始化)
+</span></span><span class="line"><span class="cl">    ---&gt; registerBeanPostProcessors (注册AutowiredAnnotationBeanPostProcessor) 
+</span></span><span class="line"><span class="cl">    ---&gt; finishBeanFactoryInitialization
+</span></span><span class="line"><span class="cl">    ---&gt; AbstractAutowireCapableBeanFactory.doCreateBean
+</span></span><span class="line"><span class="cl">    ---&gt; AbstractAutowireCapableBeanFactory.applyMergedBeanDefinitionPostProcessors
+</span></span><span class="line"><span class="cl">    ---&gt; MergedBeanDefinitionPostProcessor.postProcessMergedBeanDefinition
+</span></span><span class="line"><span class="cl">    ---&gt; AutowiredAnnotationBeanPostProcessor.findAutowiringMetadata
+</span></span></code></pre></div><p>核心调用：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">postProcessMergedBeanDefinition
+</span></span><span class="line"><span class="cl">    ---&gt;findAutowiringMetadata
+</span></span><span class="line"><span class="cl">    ---&gt;buildAutowiringMetadata
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessMergedBeanDefinition</span><span class="p">(</span><span class="n">RootBeanDefinition</span><span class="w"> </span><span class="n">beanDefinition</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">beanType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">beanName</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 调用 findAutowiringMetadata</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">InjectionMetadata</span><span class="w"> </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">findAutowiringMetadata</span><span class="p">(</span><span class="n">beanName</span><span class="p">,</span><span class="w"> </span><span class="n">beanType</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">metadata</span><span class="p">.</span><span class="na">checkConfigMembers</span><span class="p">(</span><span class="n">beanDefinition</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">InjectionMetadata</span><span class="w"> </span><span class="nf">findAutowiringMetadata</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">beanName</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="p">,</span><span class="w"> </span><span class="nd">@Nullable</span><span class="w"> </span><span class="n">PropertyValues</span><span class="w"> </span><span class="n">pvs</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Fall back to class name as cache key, for backwards compatibility with custom callers.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">cacheKey</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">hasLength</span><span class="p">(</span><span class="n">beanName</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">beanName</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">clazz</span><span class="p">.</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Quick check on the concurrent map first, with minimal locking.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">InjectionMetadata</span><span class="w"> </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">injectionMetadataCache</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">cacheKey</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">InjectionMetadata</span><span class="p">.</span><span class="na">needsRefresh</span><span class="p">(</span><span class="n">metadata</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">injectionMetadataCache</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">injectionMetadataCache</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">cacheKey</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">InjectionMetadata</span><span class="p">.</span><span class="na">needsRefresh</span><span class="p">(</span><span class="n">metadata</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">metadata</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">metadata</span><span class="p">.</span><span class="na">clear</span><span class="p">(</span><span class="n">pvs</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 调用buildAutowiringMetadata</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildAutowiringMetadata</span><span class="p">(</span><span class="n">clazz</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">injectionMetadataCache</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">cacheKey</span><span class="p">,</span><span class="w"> </span><span class="n">metadata</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">metadata</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">InjectionMetadata</span><span class="w"> </span><span class="nf">buildAutowiringMetadata</span><span class="p">(</span><span class="kd">final</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">LinkedList</span><span class="o">&lt;</span><span class="n">InjectionMetadata</span><span class="p">.</span><span class="na">InjectedElement</span><span class="o">&gt;</span><span class="w"> </span><span class="n">elements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">targetClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">clazz</span><span class="p">;</span><span class="c1">//需要处理的目标类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;</span><span class="n">InjectionMetadata</span><span class="p">.</span><span class="na">InjectedElement</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currElements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 通过反射获取该类所有的字段，并遍历每一个字段，并通过方法findAutowiredAnnotation遍历每一个字段的所用注解，</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果用autowired修饰了，则返回auotowired相关属性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReflectionUtils</span><span class="p">.</span><span class="na">doWithLocalFields</span><span class="p">(</span><span class="n">targetClass</span><span class="p">,</span><span class="w"> </span><span class="n">field</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">AnnotationAttributes</span><span class="w"> </span><span class="n">ann</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">findAutowiredAnnotation</span><span class="p">(</span><span class="n">field</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ann</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="c1">//校验autowired注解是否用在了static方法上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Modifier</span><span class="p">.</span><span class="na">isStatic</span><span class="p">(</span><span class="n">field</span><span class="p">.</span><span class="na">getModifiers</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">logger</span><span class="p">.</span><span class="na">isWarnEnabled</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">logger</span><span class="p">.</span><span class="na">warn</span><span class="p">(</span><span class="s">&#34;Autowired annotation is not supported on static fields: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">field</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="c1">//判断是否指定了required</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">boolean</span><span class="w"> </span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">determineRequiredStatus</span><span class="p">(</span><span class="n">ann</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">currElements</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">AutowiredFieldElement</span><span class="p">(</span><span class="n">field</span><span class="p">,</span><span class="w"> </span><span class="n">required</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 和上面一样的逻辑，但是是通过反射处理类的method</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReflectionUtils</span><span class="p">.</span><span class="na">doWithLocalMethods</span><span class="p">(</span><span class="n">targetClass</span><span class="p">,</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Method</span><span class="w"> </span><span class="n">bridgedMethod</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BridgeMethodResolver</span><span class="p">.</span><span class="na">findBridgedMethod</span><span class="p">(</span><span class="n">method</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">BridgeMethodResolver</span><span class="p">.</span><span class="na">isVisibilityBridgeMethodPair</span><span class="p">(</span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">bridgedMethod</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">AnnotationAttributes</span><span class="w"> </span><span class="n">ann</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">findAutowiredAnnotation</span><span class="p">(</span><span class="n">bridgedMethod</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ann</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">method</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">ClassUtils</span><span class="p">.</span><span class="na">getMostSpecificMethod</span><span class="p">(</span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Modifier</span><span class="p">.</span><span class="na">isStatic</span><span class="p">(</span><span class="n">method</span><span class="p">.</span><span class="na">getModifiers</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">logger</span><span class="p">.</span><span class="na">isWarnEnabled</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">logger</span><span class="p">.</span><span class="na">warn</span><span class="p">(</span><span class="s">&#34;Autowired annotation is not supported on static methods: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">method</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">method</span><span class="p">.</span><span class="na">getParameterCount</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">logger</span><span class="p">.</span><span class="na">isWarnEnabled</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">logger</span><span class="p">.</span><span class="na">warn</span><span class="p">(</span><span class="s">&#34;Autowired annotation should only be used on methods with parameters: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">method</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">boolean</span><span class="w"> </span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">determineRequiredStatus</span><span class="p">(</span><span class="n">ann</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">PropertyDescriptor</span><span class="w"> </span><span class="n">pd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeanUtils</span><span class="p">.</span><span class="na">findPropertyForMethod</span><span class="p">(</span><span class="n">bridgedMethod</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">currElements</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">AutowiredMethodElement</span><span class="p">(</span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">required</span><span class="p">,</span><span class="w"> </span><span class="n">pd</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 用@Autowired修饰的注解可能不止一个，因此都加在currElements这个容器里面，一起处理		</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">elements</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">currElements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">targetClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetClass</span><span class="p">.</span><span class="na">getSuperclass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">targetClass</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">targetClass</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">Object</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InjectionMetadata</span><span class="p">(</span><span class="n">clazz</span><span class="p">,</span><span class="w"> </span><span class="n">elements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>通过上面的源码，可以看到Spring在运行时通过反射查找<code>@Autowired</code>注解，并自动注入相关字段。
+Spring框架利用反射遍历目标类及其超类的所有字段和方法，查找并收集所有使用了<code>@Autowired</code>注解的元素。对于每个字段和方法，首先通过反射获取注解信息，如果字段或方法被<code>@Autowired</code>注解修饰且符合条件（如非静态），则将其封装成对应的注入元素（<code>AutowiredFieldElement</code>或<code>AutowiredMethodElement</code>）并添加到当前元素列表中。
+最后，这些注入元素会被封装到<code>InjectionMetadata</code>对象中，并用于实际的依赖注入过程，从而实现Spring的自动注入功能。</p>
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diff --git a/blog-site/public/posts/javakeyword/java-keyword-volatile/index.html b/blog-site/public/posts/javakeyword/java-keyword-volatile/index.html
index 93e17180..ff07fa06 100644
--- a/blog-site/public/posts/javakeyword/java-keyword-volatile/index.html
+++ b/blog-site/public/posts/javakeyword/java-keyword-volatile/index.html
@@ -66,30 +66,6 @@
         
         
         
-        <ul class="nav">
-            
-        <ul class="nav">
-            
-            
-            <li class="nav-item">
-                <a class="nav-link text-left" href="#volatile">
-                    volatile
-                </a>
-            </li>
-            
-            
-        </ul>
-        
-        </ul>
-        
-        
-        
-        
-        
-        
-        
-        
-        
         <ul class="nav">
             
         <ul class="nav">
@@ -301,8 +277,8 @@ <h2 id="post_single_title">volatile关键字详解</h2>
                         </span>
                         
                     </div>
-                    <div class="post_content markdown"><h2 id="volatile">volatile</h2>
-<p><code>volatile</code>通常被比喻成轻量级的锁，是Java并发编程中比较重要的一个关键字。<code>volatile</code>作用：</p>
+                    <div class="post_content markdown"><p>volatile
+<code>volatile</code>通常被比喻成轻量级的锁，是Java并发编程中比较重要的一个关键字。<code>volatile</code>作用：</p>
 <ul>
 <li>可见性：当一个线程修改了 <code>volatile</code> 变量的值，新的值对于其他线程是立即可见的。这避免了其他线程读取到旧的缓存值。</li>
 <li>有序性：对 <code>volatile</code> 变量的读写操作不会被重排序。所有对 <code>volatile</code> 变量的写操作在内存中会按照程序的顺序执行，同时在一个线程中的操作不会重排序到 <code>volatile</code> 变量的读写操作之后。</li>
@@ -558,7 +534,8 @@ <h3 id="volatile与有序性">volatile与有序性</h3>
 </span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
 </span></span></span></code></pre></div><p>用<code>volatile</code>修饰该变量，保证该变量被某个线程修改时，保证其他线程中的这个变量的可见性。
 在多线程环境下，CPU轮流切换线程执行，有可能某个线程修改了数据，准备回主内存，此时CPU切换到另一个线程修改了数据，并且写回到了主内存，此时就导致数据的不准确。
-<code>do...while()</code> + <code>CAS</code>的作用就是，当某个线程工作内存中的值与主内存中的值，如果不相同就会一直<code>while</code>循环下去，之所以用<code>do..while</code>是考虑到做自增操作。</p>
+<code>do...while()</code> + <code>CAS</code>的作用就是，当某个线程工作内存中的值与主内存中的值，如果不相同就会一直<code>while</code>循环下去，之所以用<code>do..while</code>是考虑到做自增操作。
+������</p>
 </div>
                     <div id="post_footer" class="post_footer">
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diff --git "a/blog-site/public/posts/javakeyword/static\345\205\263\351\224\256\345\255\227/index.html" "b/blog-site/public/posts/javakeyword/static\345\205\263\351\224\256\345\255\227/index.html"
new file mode 100644
index 00000000..d3eda6e1
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diff --git "a/blog-site/public/posts/javakeyword/strictfp\345\205\263\351\224\256\345\255\227/index.html" "b/blog-site/public/posts/javakeyword/strictfp\345\205\263\351\224\256\345\255\227/index.html"
new file mode 100644
index 00000000..d3eda6e1
--- /dev/null
+++ "b/blog-site/public/posts/javakeyword/strictfp\345\205\263\351\224\256\345\255\227/index.html"
@@ -0,0 +1,342 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title> ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+	
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+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
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+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
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+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
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+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
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+                    <span>脚踏实地</span>
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diff --git "a/blog-site/public/posts/javakeyword/this\345\205\263\351\224\256\345\255\227/index.html" "b/blog-site/public/posts/javakeyword/this\345\205\263\351\224\256\345\255\227/index.html"
new file mode 100644
index 00000000..d3eda6e1
--- /dev/null
+++ "b/blog-site/public/posts/javakeyword/this\345\205\263\351\224\256\345\255\227/index.html"
@@ -0,0 +1,342 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
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+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title> ｜ 脚踏实地</title>
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+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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diff --git "a/blog-site/public/posts/javakeyword/transient\345\205\263\351\224\256\345\255\227/index.html" "b/blog-site/public/posts/javakeyword/transient\345\205\263\351\224\256\345\255\227/index.html"
new file mode 100644
index 00000000..d3eda6e1
--- /dev/null
+++ "b/blog-site/public/posts/javakeyword/transient\345\205\263\351\224\256\345\255\227/index.html"
@@ -0,0 +1,342 @@
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+                mixColor: '#f7f7f7', 
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+                buttonColorDark: '#212121', 
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+            }).toggle();
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+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/blog-site/public/posts/spring/java-spring/index.html b/blog-site/public/posts/spring/java-spring/index.html
index 593ed8c2..a55d33c4 100644
--- a/blog-site/public/posts/spring/java-spring/index.html
+++ b/blog-site/public/posts/spring/java-spring/index.html
@@ -2471,7 +2471,7 @@ <h4 id="finishbeanfactoryinitialization">finishBeanFactoryInitialization</h4>
 </span></span><span class="line"><span class="cl">   --&gt;AbstractAdvisorAutoProxyCreator.findEligibleAdvisors
 </span></span><span class="line"><span class="cl">   --&gt;AbstractAdvisorAutoProxyCreator.findCandidateAdvisors
 </span></span><span class="line"><span class="cl">   --&gt;BeanFactoryAdvisorRetrievalHelper.findAdvisorBeans
-</span></span></code></pre></div><p>BeanFactoryAdvisorRetrievalHelper这个类是一个Spring AOP内部工具类，用来从Bean容器中获取所有Spring的Advisor Bean。
+</span></span></code></pre></div><p><code>BeanFactoryAdvisorRetrievalHelper</code>这个类是一个Spring AOP内部工具类，用来从Bean容器中获取所有Spring的Advisor Bean。
 该工具内部使用了缓存机制，虽然公开的查找方法可能会被调用多次，但并不是每次都会真正查找，而是会利用缓存。</p>
 <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Advisor</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">findAdvisorBeans</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
 </span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="c1">//cachedAdvisorBeanNames是advisor名称的缓存</span><span class="w">
@@ -2995,7 +2995,7 @@ <h3 id="spring事务工作原理">Spring事务工作原理</h3>
 </span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
 </span></span></span></code></pre></div><p><code>invokeWithinTransaction</code>方法是<code>TransactionInterceptor</code>类中的核心方法，它负责在执行目标方法时管理事务的生命周期。首先该方法通过<code>getTransactionAttributeSource()</code>获取事务属性源，进而确定当前方法是否需要事务支持。
 接着根据获取的事务属性，选择合适的事务管理器，并生成一个方法标识以记录当前事务的上下文信息。在方法执行前，会检查是否需要开启新的事务，并在事务环境中执行目标方法的逻辑。
-如果方法执行过程中出现异常，事务管理器会回滚事务以保证数据一致性，否则在方法执行成功后，事务管理器将提交事务。最后无论方法执行结果如何，都会清理事务相关的信息，释放资源并恢复状态，来保证事务管理的完整性和有效性</p>
+如果方法执行过程中出现异常，事务管理器会回滚事务以保证数据一致性，否则在方法执行成功后，事务管理器将提交事务。最后无论方法执行结果如何，都会清理事务相关的信息，释放资源并恢复状态，来保证事务管理的完整性和有效性。</p>
 <p>简而言之，当一个方法使用了<code>@Transactional</code>注解，在程序运行时，JVM为该Bean创建一个代理对象，并且在调用目标方法的时候进行使用<code>TransactionInterceptor</code>拦截，代理对象负责在调用目标方法之前开启事务，然后执行方法的逻辑。
 方法执行成功，则提交事务，如果执行方法中出现异常，则回滚事务。同时Spring利用<code>ThreadLocal</code>会将事务资源（如数据库连接）与当前线程绑定，以确保在同一事务中共享资源，这些资源在事务提交或回滚时会被清理。</p>
 </div>
diff --git a/blog-site/public/posts/toy/pay-code/index.html b/blog-site/public/posts/toy/pay-code/index.html
new file mode 100644
index 00000000..fc51e4ba
--- /dev/null
+++ b/blog-site/public/posts/toy/pay-code/index.html
@@ -0,0 +1,3102 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>整合支付功能 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="结构 完整代码：https://gitee.com/gitee_pikaqiu/easy-archetype pom.xml &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.alipay.sdk&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;alipay-sdk-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;4.9.9&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt;" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
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+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
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+    
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+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%93%e6%9e%84">
+                    结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#pomxml">
+                    pom.xml
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#applicationyml">
+                    application.yml
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%ac%e5%85%b1%e9%83%a8%e5%88%86">
+                    公共部分
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payservice">
+                    PayService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payrefundable">
+                    PayRefundAble
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payorderqueryable">
+                    PayOrderQueryAble
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payordercloseable">
+                    PayOrderCloseAble
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#paymentable">
+                    PaymentAble
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#abstractpayservice">
+                    AbstractPayService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#commonpayrequest">
+                    CommonPayRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payplatformtypeenum">
+                    PayPlatformTypeEnum
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payfacade">
+                    PayFacade
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payfacadeimpl">
+                    PayFacadeImpl
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payexception">
+                    PayException
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%94%af%e4%bb%98%e5%ae%9d">
+                    支付宝
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayrefundservice">
+                    AlipayRefundService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipaypayorderqueryservice">
+                    AlipayPayOrderQueryService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipaypaymentservice">
+                    AlipayPaymentService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayordercloseservice">
+                    AlipayOrderCloseService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#aliapp">
+                    AliApp
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alih5">
+                    AliH5
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipc">
+                    AliPc
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayordercloserequest">
+                    AlipayOrderCloseRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipaypaymentrequest">
+                    AlipayPaymentRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayqueryorderrequest">
+                    AlipayQueryOrderRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayrefundrequest">
+                    AlipayRefundRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayconfiguration">
+                    AlipayConfiguration
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayproperties">
+                    AlipayProperties
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%be%ae%e4%bf%a1">
+                    微信
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayrefundservice">
+                    WxpayRefundService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpaypaymentservice">
+                    WxpayPaymentService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayorderqueryservice">
+                    WxpayOrderQueryService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayordercloseservice">
+                    WxpayOrderCloseService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxapp">
+                    WxApp
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxh5">
+                    WxH5
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxjsapi">
+                    WxJsapi
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxnative">
+                    WxNative
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxorderqueryrequest">
+                    WxOrderQueryRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayordercloserequest">
+                    WxpayOrderCloseRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpaypaymentrequest">
+                    WxpayPaymentRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxrefundrequest">
+                    WxRefundRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayconfiguration">
+                    WxpayConfiguration
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayproperties">
+                    WxpayProperties
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b0%83%e7%94%a8%e6%b5%8b%e8%af%95">
+                    调用测试
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayexamplecontroller">
+                    AlipayExampleController
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayexamplecontroller">
+                    WxpayExampleController
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#paytestcontroller">
+                    PayTestController
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_pic" title="导出图片" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_markdown" title="导出markdown" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
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+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">整合支付功能</h2>
+                        <span id="post_page_title_date" class="date">2023.08.10</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="结构">结构</h2>
+<p><img alt="整合支付功能" src="/iblog/posts/annex/images/essays/%E6%95%B4%E5%90%88%E6%94%AF%E4%BB%98%E5%8A%9F%E8%83%BD-01.jpg"></p>
+<p>完整代码：<a href="https://gitee.com/gitee_pikaqiu/easy-archetype">https://gitee.com/gitee_pikaqiu/easy-archetype</a></p>
+<h2 id="pomxml">pom.xml</h2>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-xml" data-lang="xml"><span class="line"><span class="cl"><span class="nt">&lt;dependencies&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-web<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-test<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;scope&gt;</span>test<span class="nt">&lt;/scope&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.projectlombok<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>lombok<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;optional&gt;</span>true<span class="nt">&lt;/optional&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>cn.hutool<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>hutool-all<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>5.8.11<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>com.alipay.sdk<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>alipay-sdk-java<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>4.9.9<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>com.github.binarywang<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>weixin-java-pay<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>4.5.0<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="nt">&lt;/dependencies&gt;</span>
+</span></span></code></pre></div><h2 id="applicationyml">application.yml</h2>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="nt">server</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">port</span><span class="p">:</span><span class="w"> </span><span class="m">8080</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">pay</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">wechat</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#微信公众号或者小程序等的appid</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">appId</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#微信支付商户号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">mchId</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#微信支付商户密钥</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">mchKey</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#服务商模式下的子商户公众账号ID</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">subAppId</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#服务商模式下的子商户号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">subMchId</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># p12证书的位置，可以指定绝对路径，也可以指定类路径（以classpath:开头）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">keyPath</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">alipay</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 应用ID,您的APPID，收款账号既是您的APPID对应支付宝账号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">appId</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 商户私钥，您的PKCS8格式RSA2私钥</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">merchantPrivateKey</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 支付宝公钥,查看地址：https://openhome.alipay.com/platform/keyManage.htm 对应APPID下的支付宝公钥。</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">alipayPublicKey</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 服务器异步通知页面路径  需http://格式的完整路径，不能加?id=123这类自定义参数，必须外网可以正常访问</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">notifyUrl</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;http://localhost:8080/ali/paymentNotify&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 页面跳转同步通知页面路径 需http://格式的完整路径，不能加?id=123这类自定义参数，必须外网可以正常访问</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">returnUrl</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;http://localhost:8080/ali/paymentNotify&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 签名方式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">signType</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;RSA2&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 字符编码格式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">charset</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;utf-8&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 格式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">format</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;json&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 支付宝网关</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">gatewayUrl</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;https://openapi.alipaydev.com/gateway.do&#34;</span><span class="w">
+</span></span></span></code></pre></div><h2 id="公共部分">公共部分</h2>
+<h3 id="payservice">PayService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取支付平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 支付平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付时可能存在的行为; 支付订单 查询订单 生成支付二维码 退款等
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return any
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">apply</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payrefundable">PayRefundAble</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayRefundAble</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payorderqueryable">PayOrderQueryAble</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayOrderQueryAble</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payordercloseable">PayOrderCloseAble</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayOrderCloseAble</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="paymentable">PaymentAble</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PaymentAble</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="abstractpayservice">AbstractPayService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractPayService</span><span class="o">&lt;</span><span class="n">Q</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="p">,</span><span class="n">S</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">apply</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">payRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Q</span><span class="w"> </span><span class="n">orderInfo</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Q</span><span class="p">)</span><span class="w"> </span><span class="n">payRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 前置处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;开始执行前置处理.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">preprocessing</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="s">&#34;支付前置处理失败,不能继续执行&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;前置处理执行完毕&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;开始执行,请求参数 {}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">S</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">processing</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;执行完毕,响应参数 {}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">result</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 后置处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;开始执行后置处理.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">postprocessing</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;后置处理执行完毕.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 前置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 通过 ; false 不通过
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w">  </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preprocessing</span><span class="p">(</span><span class="n">Q</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 核心处理方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 支付结果
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">S</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">Q</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postprocessing</span><span class="p">(</span><span class="n">Q</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="commonpayrequest">CommonPayRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payplatformtypeenum">PayPlatformTypeEnum</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">enum</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 支付平台</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ALIPAY</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">WECHAT</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payfacade">PayFacade</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayFacade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付调用接口（指定操作传入class，传入请求参数）
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param &lt;T&gt;       支付操作类型 {@linkplain  PayService}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">execute</span><span class="p">(</span><span class="n">Class</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">payClass</span><span class="p">,</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payfacadeimpl">PayFacadeImpl</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PayFacadeImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayFacade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">execute</span><span class="p">(</span><span class="n">Class</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">payClass</span><span class="p">,</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Optional</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">payItem</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">SpringUtil</span><span class="p">.</span><span class="na">getBeansOfType</span><span class="p">(</span><span class="n">payClass</span><span class="p">).</span><span class="na">values</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">stream</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">filter</span><span class="p">(</span><span class="n">item</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">item</span><span class="p">.</span><span class="na">getPayPlatformType</span><span class="p">().</span><span class="na">equals</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">.</span><span class="na">getPayTypeEnum</span><span class="p">()))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">findFirst</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;支付行为[{}],调用平台类型[{}]&#34;</span><span class="p">,</span><span class="n">payClass</span><span class="p">.</span><span class="na">getSimpleName</span><span class="p">(),</span><span class="n">orderInfo</span><span class="p">.</span><span class="na">getPayTypeEnum</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Optional</span><span class="o">&lt;</span><span class="n">PayService</span><span class="o">&gt;</span><span class="w"> </span><span class="n">payService</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Optional</span><span class="o">&lt;</span><span class="n">PayService</span><span class="o">&gt;</span><span class="p">)</span><span class="w"> </span><span class="n">payItem</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">payService</span><span class="p">.</span><span class="na">isPresent</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">payService</span><span class="p">.</span><span class="na">get</span><span class="p">().</span><span class="na">apply</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;未获取到支付平台类型&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payexception">PayException</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PayException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">msg</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">PayException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">msg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">PayException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">msg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="支付宝">支付宝</h2>
+<h3 id="alipayrefundservice">AlipayRefundService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayRefundService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="o">&lt;</span><span class="n">AlipayRefundRequest</span><span class="p">,</span><span class="n">AlipayTradeRefundResponse</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayRefundAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradeRefundResponse</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">AlipayRefundRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeRefundRequest</span><span class="w"> </span><span class="n">alipayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayTradeRefundRequest</span><span class="w"> </span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setBizContent</span><span class="p">(</span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeRefundResponse</span><span class="w"> </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">alipayRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">AlipayApiException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">response</span><span class="p">.</span><span class="na">isSuccess</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 退款成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipaypayorderqueryservice">AlipayPayOrderQueryService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayPayOrderQueryService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="o">&lt;</span><span class="n">AlipayQueryOrderRequest</span><span class="p">,</span><span class="n">AlipayTradeQueryResponse</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayOrderQueryAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradeQueryResponse</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">AlipayQueryOrderRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeQueryRequest</span><span class="w"> </span><span class="n">alipayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayTradeQueryRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setBizContent</span><span class="p">(</span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeQueryResponse</span><span class="w"> </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">alipayRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">AlipayApiException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">response</span><span class="p">.</span><span class="na">isSuccess</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 支付成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipaypaymentservice">AlipayPaymentService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayPaymentService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="o">&lt;</span><span class="n">AlipayPaymentRequest</span><span class="p">,</span><span class="w"> </span><span class="n">AlipayTradePagePayResponse</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PaymentAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayProperties</span><span class="w"> </span><span class="n">aliPayProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="n">alipayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setReturnUrl</span><span class="p">(</span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getReturnUrl</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setNotifyUrl</span><span class="p">(</span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getNotifyUrl</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setBizContent</span><span class="p">(</span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayResponse</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">AlipayApiException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayordercloseservice">AlipayOrderCloseService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayOrderCloseService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="o">&lt;</span><span class="n">AlipayOrderCloseRequest</span><span class="p">,</span><span class="n">AlipayTradeCloseResponse</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayOrderCloseAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradeCloseResponse</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">AlipayOrderCloseRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeCloseRequest</span><span class="w"> </span><span class="n">alipayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayTradeCloseRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setBizContent</span><span class="p">(</span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeCloseResponse</span><span class="w"> </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">alipayRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">AlipayApiException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">response</span><span class="p">.</span><span class="na">isSuccess</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 关闭成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="aliapp">AliApp</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AliApp</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AlipayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayPaymentRequest</span><span class="p">.</span><span class="na">setProduct_code</span><span class="p">(</span><span class="s">&#34;QUICK_MSECURITY_PAY&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alih5">AliH5</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AliH5</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AlipayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayPaymentRequest</span><span class="p">.</span><span class="na">setProduct_code</span><span class="p">(</span><span class="s">&#34;QUICK_WAP_WAY&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipc">AliPc</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AliPc</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AlipayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayPaymentRequest</span><span class="p">.</span><span class="na">setProduct_code</span><span class="p">(</span><span class="s">&#34;FAST_INSTANT_TRADE_PAY&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayordercloserequest">AlipayOrderCloseRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayOrderCloseRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 该交易在支付宝系统中的交易流水号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 订单支付时传入的商户订单号,和支付宝交易号不能同时为空。 trade_no,out_trade_no如果同时存在优先取trade_no
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipaypaymentrequest">AlipayPaymentRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayPaymentRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 订单名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subject</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 付款金额
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">total_amount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商品描述
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">body</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 超时时间参数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">timeout_express</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;60m&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 产品编号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">product_code</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayqueryorderrequest">AlipayQueryOrderRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayQueryOrderRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayrefundrequest">AlipayRefundRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayRefundRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付宝交易号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款请求号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_request_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款金额
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refund_amount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayconfiguration">AlipayConfiguration</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Configuration</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@EnableConfigurationProperties</span><span class="p">(</span><span class="n">AlipayProperties</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayConfiguration</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayProperties</span><span class="w"> </span><span class="n">aliPayProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="nf">alipayClient</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultAlipayClient</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getGatewayUrl</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getAppId</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getMerchantPrivateKey</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getFormat</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getCharset</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getAlipayPublicKey</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getSignType</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayproperties">AlipayProperties</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@ConfigurationProperties</span><span class="p">(</span><span class="n">prefix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;pay.alipay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayProperties</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 应用ID,您的APPID，收款账号既是您的APPID对应支付宝账号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">appId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户私钥，您的PKCS8格式RSA2私钥
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">merchantPrivateKey</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付宝公钥,查看地址：https://openhome.alipay.com/platform/keyManage.htm 对应APPID下的支付宝公钥。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">alipayPublicKey</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 服务器异步通知页面路径  需http://格式的完整路径，不能加?id=123这类自定义参数，必须外网可以正常访问
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">notifyUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 页面跳转同步通知页面路径 需http://格式的完整路径，不能加?id=123这类自定义参数，必须外网可以正常访问
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">returnUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 签名方式
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">signType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 字符编码格式
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">charset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 格式
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">format</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付宝网关
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">gatewayUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="微信">微信</h2>
+<h3 id="wxpayrefundservice">WxpayRefundService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayRefundService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayRefundAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxRefundRequest</span><span class="w"> </span><span class="n">wxRefundRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">WxRefundRequest</span><span class="p">)</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayRefundRequest</span><span class="w"> </span><span class="n">refundRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayRefundRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setOutRefundNo</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getOutRefundNo</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setRefundAccount</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getRefundAccount</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setRefundDesc</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getRefundDesc</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setRefundFee</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getRefundFee</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setNotifyUrl</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getNotifyUrl</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setRefundFeeType</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getRefundFeeType</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setTransactionId</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getTransactionId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setOutRefundNo</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getOutTradeNo</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setTotalFee</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getTotalFee</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">refund</span><span class="p">(</span><span class="n">refundRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">WxPayException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpaypaymentservice">WxpayPaymentService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayPaymentService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PaymentAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 微信统一下单请求对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">request</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setOutTradeNo</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getOut_trade_no</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setBody</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getBody</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setFeeType</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getFee_type</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setTotalFee</span><span class="p">(</span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getTotal_fee</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setSpbillCreateIp</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getSpbill_create_ip</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setNotifyUrl</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getNotify_url</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setProductId</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setTimeExpire</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getTime_expire</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setTimeStart</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getTime_start</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setProfitSharing</span><span class="p">(</span><span class="s">&#34;Y&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">request</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">unifiedOrder</span><span class="p">(</span><span class="n">buildUnifiedOrderRequest</span><span class="p">((</span><span class="n">WxpayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">WxPayException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayorderqueryservice">WxpayOrderQueryService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayOrderQueryService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayOrderQueryAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxOrderQueryRequest</span><span class="w"> </span><span class="n">wxQueryOrder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">WxOrderQueryRequest</span><span class="p">)</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayOrderQueryRequest</span><span class="w"> </span><span class="n">req</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayOrderQueryRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">req</span><span class="p">.</span><span class="na">setSubMchId</span><span class="p">(</span><span class="n">wxQueryOrder</span><span class="p">.</span><span class="na">getSubMchId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">req</span><span class="p">.</span><span class="na">setSubAppId</span><span class="p">(</span><span class="n">wxQueryOrder</span><span class="p">.</span><span class="na">getSubMchAppId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">req</span><span class="p">.</span><span class="na">setOutTradeNo</span><span class="p">(</span><span class="n">wxQueryOrder</span><span class="p">.</span><span class="na">getPayOrderId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayOrderQueryResult</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">queryOrder</span><span class="p">(</span><span class="n">req</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">WxPayException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="s">&#34;微信订单查询异常&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 根据状态判断</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;SUCCESS&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 支付成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;USERPAYING&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 支付中，等待用户输入密码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;CLOSED&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">())</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;REVOKED&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">())</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;PAYERROR&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// CLOSED—已关闭， REVOKED—已撤销(刷卡支付), PAYERROR--支付失败(其他原因，如银行返回失败) 支付失败</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// unknow</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayordercloseservice">WxpayOrderCloseService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayOrderCloseService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayOrderCloseAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxpayOrderCloseRequest</span><span class="w"> </span><span class="n">wxOrderInfo</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">WxpayOrderCloseRequest</span><span class="p">)</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayOrderCloseRequest</span><span class="w"> </span><span class="n">wxPayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayOrderCloseRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayRequest</span><span class="p">.</span><span class="na">setOutTradeNo</span><span class="p">(</span><span class="n">wxOrderInfo</span><span class="p">.</span><span class="na">getOut_trade_no</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayOrderCloseResult</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">closeOrder</span><span class="p">(</span><span class="n">wxPayRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">WxPayException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxapp">WxApp</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxApp</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WxpayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setTradeType</span><span class="p">(</span><span class="n">WxPayConstants</span><span class="p">.</span><span class="na">TradeType</span><span class="p">.</span><span class="na">APP</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setOpenid</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getOpenid</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxh5">WxH5</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxH5</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WxpayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setTradeType</span><span class="p">(</span><span class="n">WxPayConstants</span><span class="p">.</span><span class="na">TradeType</span><span class="p">.</span><span class="na">MWEB</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setOpenid</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getOpenid</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxjsapi">WxJsapi</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxJsapi</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WxpayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setTradeType</span><span class="p">(</span><span class="n">WxPayConstants</span><span class="p">.</span><span class="na">TradeType</span><span class="p">.</span><span class="na">JSAPI</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setOpenid</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getOpenid</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxnative">WxNative</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxNative</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WxpayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setTradeType</span><span class="p">(</span><span class="n">WxPayConstants</span><span class="p">.</span><span class="na">TradeType</span><span class="p">.</span><span class="na">NATIVE</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxorderqueryrequest">WxOrderQueryRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxOrderQueryRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">payOrderId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 特约商户传入</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** 子商户ID **/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subMchId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** 子账户appID **/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subMchAppId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayordercloserequest">WxpayOrderCloseRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayOrderCloseRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpaypaymentrequest">WxpayPaymentRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayPaymentRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 公众账号appid
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">appid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mch_id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商品描述
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">body</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 附加数据; 在查询API和支付通知中原样返回，可作为自定义参数使用。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">attach</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号; 要求32个字符内（最少6个字符），只能是数字、大小写字母_-|*且在同一个商户号下唯一
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 总金额(分)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">total_fee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 默认人民币：CNY
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">fee_type</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易起始时间 格式为yyyyMMddHHmmss
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">time_start</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易结束时间 格式为yyyyMMddHHmmss
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">time_expire</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易类型;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * JSAPI -JSAPI支付
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * NATIVE -Native支付
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * APP -APP支付
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">trade_type</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商品ID; trade_type=NATIVE时，此参数必传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">product_id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 用户标识; trade_type=JSAPI时（即JSAPI支付），此参数必传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">openid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 是否分账 不传默认不分账
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;p&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Y-是，需要分账
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * N-否，不分账
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">profit_sharing</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 回调地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">notify_url</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支持IPV4和IPV6两种格式的IP地址。用户的客户端IP
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">spbill_create_ip</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 随机字符串； 长度要求在32位以内
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nonce_str</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxrefundrequest">WxRefundRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxRefundRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 微信支付订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">transactionId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户退款单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outRefundNo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 订单金额
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">totalFee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款金额
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">refundFee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款货币种类
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundFeeType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款资金来源
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundAccount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款原因
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundDesc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款结果通知url
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">notifyUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayconfiguration">WxpayConfiguration</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Configuration</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@ConditionalOnClass</span><span class="p">(</span><span class="n">WxPayService</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@EnableConfigurationProperties</span><span class="p">(</span><span class="n">WxpayProperties</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayConfiguration</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WxpayProperties</span><span class="w"> </span><span class="n">properties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@ConditionalOnMissingBean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="nf">wxService</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayConfig</span><span class="w"> </span><span class="n">payConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayConfig</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setAppId</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getAppId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setMchId</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getMchId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setMchKey</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getMchKey</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setSubAppId</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getSubAppId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setSubMchId</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getSubMchId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setKeyPath</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getKeyPath</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 可以指定是否使用沙箱环境</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setUseSandboxEnv</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayServiceImpl</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">setConfig</span><span class="p">(</span><span class="n">payConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayproperties">WxpayProperties</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@ConfigurationProperties</span><span class="p">(</span><span class="n">prefix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;pay.wechat&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayProperties</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 设置微信公众号或者小程序等的appid
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">appId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 微信支付商户号
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mchId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 微信支付商户密钥
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mchKey</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 服务商模式下的子商户公众账号ID，普通模式请不要配置，请在配置文件中将对应项删除
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subAppId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 服务商模式下的子商户号，普通模式请不要配置，最好是请在配置文件中将对应项删除
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subMchId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * apiclient_cert.p12文件的绝对路径，或者如果放在项目中，请以classpath:开头指定
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">keyPath</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 支付回调地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">payNotifyUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 退款回调地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundNotifyUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="调用测试">调用测试</h2>
+<h3 id="alipayexamplecontroller">AlipayExampleController</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@RestController</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/example/alipay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayExampleController</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 统一下单
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/59da99d0_alipay.trade.page.pay
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/unifiedOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradePagePayResponse</span><span class="w"> </span><span class="nf">unifiedOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/bff76748_alipay.trade.query
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/queryOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradeQueryResponse</span><span class="w"> </span><span class="nf">queryOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradeQueryRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易退款
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/357441a2_alipay.trade.fastpay
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/refund&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradeRefundResponse</span><span class="w"> </span><span class="nf">refund</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradeRefundRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/357441a2_alipay.trade.fastpay.refund.query
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/refundQuery&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradeFastpayRefundQueryResponse</span><span class="w"> </span><span class="nf">refundQuery</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradeFastpayRefundQueryRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易关闭
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/8dc9ebb3_alipay.trade.close
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/closeOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradeCloseResponse</span><span class="w"> </span><span class="nf">closeOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradeCloseRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayexamplecontroller">WxpayExampleController</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@RestController</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/example/wxpay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayExampleController</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 查询订单(详见https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_2)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 该接口提供所有微信支付订单的查询，商户可以通过查询订单接口主动查询订单状态，完成下一步的业务逻辑。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 需要调用查询接口的情况：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * ◆ 当商户后台、网络、服务器等出现异常，商户系统最终未接收到支付通知；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * ◆ 调用支付接口后，返回系统错误或未知交易状态情况；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * ◆ 调用被扫支付API，返回USERPAYING的状态；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * ◆ 调用关单或撤销接口API之前，需确认支付状态；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址：https://api.mch.weixin.qq.com/pay/orderquery
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param transactionId 微信订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param outTradeNo    商户系统内部的订单号，当没提供transactionId时需要传这个。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/queryOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayOrderQueryResult</span><span class="w"> </span><span class="nf">queryOrder</span><span class="p">(</span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">transactionId</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                            </span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">queryOrder</span><span class="p">(</span><span class="n">transactionId</span><span class="p">,</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/queryOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayOrderQueryResult</span><span class="w"> </span><span class="nf">queryOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayOrderQueryRequest</span><span class="w"> </span><span class="n">wxPayOrderQueryRequest</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">queryOrder</span><span class="p">(</span><span class="n">wxPayOrderQueryRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 关闭订单
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 应用场景
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 以下情况需要调用关单接口：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 1. 商户订单支付失败需要生成新单号重新发起支付，要对原订单号调用关单，避免重复支付；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 2. 系统下单后，用户支付超时，系统退出不再受理，避免用户继续，请调用关单接口。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 注意：订单生成后不能马上调用关单接口，最短调用时间间隔为5分钟。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址：https://api.mch.weixin.qq.com/pay/closeorder
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 是否需要证书：   不需要。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param outTradeNo 商户系统内部的订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/closeOrder/{outTradeNo}&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayOrderCloseResult</span><span class="w"> </span><span class="nf">closeOrder</span><span class="p">(</span><span class="nd">@PathVariable</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">closeOrder</span><span class="p">(</span><span class="n">outTradeNo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/closeOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayOrderCloseResult</span><span class="w"> </span><span class="nf">closeOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayOrderCloseRequest</span><span class="w"> </span><span class="n">wxPayOrderCloseRequest</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">closeOrder</span><span class="p">(</span><span class="n">wxPayOrderCloseRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 调用统一下单接口，并组装生成支付所需参数对象.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 统一下单请求参数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param &lt;T&gt;     请使用{@link com.github.binarywang.wxpay.bean.order}包下的类
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.github.binarywang.wxpay.bean.order}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/createOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">createOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">createOrder</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 统一下单(详见https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_1)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在发起微信支付前，需要调用统一下单接口，获取&#34;预支付交易会话标识&#34;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址：https://api.mch.weixin.qq.com/pay/unifiedorder
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象，注意一些参数如appid、mchid等不用设置，方法内会自动从配置对象中获取到（前提是对应配置中已经设置）
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/unifiedOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayUnifiedOrderResult</span><span class="w"> </span><span class="nf">unifiedOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">unifiedOrder</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 微信支付-申请退款
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 详见 https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_4
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口链接：https://api.mch.weixin.qq.com/secapi/pay/refund
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 退款操作结果
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/refund&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayRefundResult</span><span class="w"> </span><span class="nf">refund</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayRefundRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">refund</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 微信支付-查询退款
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 应用场景：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *  提交退款申请后，通过调用该接口查询退款状态。退款有一定延时，用零钱支付的退款20分钟内到账，
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *  银行卡支付的退款3个工作日后重新查询退款状态。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 详见 https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_5
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口链接：https://api.mch.weixin.qq.com/pay/refundquery
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 以下四个参数四选一
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param transactionId 微信订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param outTradeNo    商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param outRefundNo   商户退款单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param refundId      微信退款单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 退款信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/refundQuery&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayRefundQueryResult</span><span class="w"> </span><span class="nf">refundQuery</span><span class="p">(</span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">transactionId</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                              </span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                              </span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outRefundNo</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                              </span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundId</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">refundQuery</span><span class="p">(</span><span class="n">transactionId</span><span class="p">,</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">,</span><span class="w"> </span><span class="n">outRefundNo</span><span class="p">,</span><span class="w"> </span><span class="n">refundId</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param wxPayRefundQueryRequest 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 退款信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @throws WxPayException
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/refundQuery&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayRefundQueryResult</span><span class="w"> </span><span class="nf">refundQuery</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayRefundQueryRequest</span><span class="w"> </span><span class="n">wxPayRefundQueryRequest</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">refundQuery</span><span class="p">(</span><span class="n">wxPayRefundQueryRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付回调通知处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/notify/order&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">parseOrderNotifyResult</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">xmlData</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">WxPayOrderNotifyResult</span><span class="w"> </span><span class="n">notifyResult</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">parseOrderNotifyResult</span><span class="p">(</span><span class="n">xmlData</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// TODO 根据自己业务场景需要构造返回对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">WxPayNotifyResponse</span><span class="p">.</span><span class="na">success</span><span class="p">(</span><span class="s">&#34;成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款回调通知处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param xmlData
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/notify/refund&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">parseRefundNotifyResult</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">xmlData</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">WxPayRefundNotifyResult</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">parseRefundNotifyResult</span><span class="p">(</span><span class="n">xmlData</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// TODO 根据自己业务场景需要构造返回对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">WxPayNotifyResponse</span><span class="p">.</span><span class="na">success</span><span class="p">(</span><span class="s">&#34;成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 扫码支付回调通知处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/notify/scanpay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">parseScanPayNotifyResult</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">xmlData</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">WxScanPayNotifyResult</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">parseScanPayNotifyResult</span><span class="p">(</span><span class="n">xmlData</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// TODO 根据自己业务场景需要构造返回对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">WxPayNotifyResponse</span><span class="p">.</span><span class="na">success</span><span class="p">(</span><span class="s">&#34;成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 扫码支付模式一生成二维码的方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 二维码中的内容为链接，形式为：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * weixin://wxpay/bizpayurl?sign=XXXXX&amp;appid=XXXXX&amp;mch_id=XXXXX&amp;product_id=XXXXXX&amp;time_stamp=XXXXXX&amp;nonce_str=XXXXX
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 其中XXXXX为商户需要填写的内容，商户将该链接生成二维码，如需要打印发布二维码，需要采用此格式。商户可调用第三方库生成二维码图片。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文档详见: https://pay.weixin.qq.com/wiki/doc/api/native.php?chapter=6_4
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param productId  产品Id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param logoFile   商户logo图片的文件对象，可以为空
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param sideLength 要生成的二维码的边长，如果为空，则取默认值400
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 生成的二维码的字节数组
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="nf">createScanPayQrcodeMode1</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">productId</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="n">logoFile</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">sideLength</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">createScanPayQrcodeMode1</span><span class="p">(</span><span class="n">productId</span><span class="p">,</span><span class="w"> </span><span class="n">logoFile</span><span class="p">,</span><span class="w"> </span><span class="n">sideLength</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 扫码支付模式一生成二维码的方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 二维码中的内容为链接，形式为：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * weixin://wxpay/bizpayurl?sign=XXXXX&amp;appid=XXXXX&amp;mch_id=XXXXX&amp;product_id=XXXXXX&amp;time_stamp=XXXXXX&amp;nonce_str=XXXXX
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 其中XXXXX为商户需要填写的内容，商户将该链接生成二维码，如需要打印发布二维码，需要采用此格式。商户可调用第三方库生成二维码图片。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文档详见: https://pay.weixin.qq.com/wiki/doc/api/native.php?chapter=6_4
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param productId 产品Id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 生成的二维码URL连接
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span></code></pre></div><h3 id="paytestcontroller">PayTestController</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RestController</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/example/iPay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PayTestController</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PayFacade</span><span class="w"> </span><span class="n">payFacade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/alipayUnifiedOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">alipayUnifiedOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payFacade</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">PaymentAble</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayPaymentRequest</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setBody</span><span class="p">(</span><span class="s">&#34;商品描述&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setSubject</span><span class="p">(</span><span class="s">&#34;支付宝测试商品&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setTotal_amount</span><span class="p">(</span><span class="s">&#34;0.1&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setOut_trade_no</span><span class="p">(</span><span class="s">&#34;2023009999999&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;支付宝-支付-交易成功&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/alipayUnifiedOrderNotify&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">alipayUnifiedOrderNotify</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;支付宝-支付回调-交易成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;交易成功！&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/wxUnifiedOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">wxUnifiedOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payFacade</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">PaymentAble</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">new</span><span class="w"> </span><span class="n">WxpayPaymentRequest</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setBody</span><span class="p">(</span><span class="s">&#34;微信测试商品&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setTotal_fee</span><span class="p">(</span><span class="s">&#34;0.1&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setOut_trade_no</span><span class="p">(</span><span class="s">&#34;2023009999999&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;微信-支付-交易成功&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/wxUnifiedOrderNotify&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">wxUnifiedOrderNotify</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;微信-支付回调-交易成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;交易成功！&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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+
+    function addDarkmodeWidget(){
+        const hours = new Date().getHours();
+        if (hours >= 19 || hours <= 5){
+            new Darkmode({
+                right: '32px', 
+                bottom: 'unset', 
+                
+                time: '0.3s', 
+                mixColor: '#f7f7f7', 
+                backgroundColor: '#f7f7f7', 
+                buttonColorDark: '#212121', 
+                buttonColorLight: '#f7f7f7', 
+                saveInCookies: false, 
+                autoMatchOsTheme: true 
+            }).toggle();
+        }
+    }
+    
+    
+</script>
+
+
+
+
+
+
+
+
+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/blog-site/public/posts/toy/pipeline-business/index.html b/blog-site/public/posts/toy/pipeline-business/index.html
new file mode 100644
index 00000000..20a6e44e
--- /dev/null
+++ b/blog-site/public/posts/toy/pipeline-business/index.html
@@ -0,0 +1,2191 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head><script src="/iblog/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=iblog/livereload" data-no-instant defer></script>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java管道流设计模式结合业务 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="流程图 代码实现 完整代码：https://gitee.com/gitee_pikaqiu/easy-pipeline pom &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.plugin&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-plugin-core&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;${spring.plugin.core.version}&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt;" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
+    
+
+	
+
+    <link rel="shortcut icon" href="http://localhost:1313/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="http://localhost:1313/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b5%81%e7%a8%8b%e5%9b%be">
+                    流程图
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%a3%e7%a0%81%e5%ae%9e%e7%8e%b0">
+                    代码实现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#pom">
+                    pom
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#context">
+                    context
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#eventcontext">
+                    EventContext
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#biztype">
+                    BizType
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#abstracteventcontext">
+                    AbstractEventContext
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filter">
+                    filter
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#eventfilter">
+                    EventFilter
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#abstracteventfilter">
+                    AbstractEventFilter
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#eventfilterchain">
+                    EventFilterChain
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filterchainpipeline">
+                    FilterChainPipeline
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#defaulteventfilterchain">
+                    DefaultEventFilterChain
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#selector">
+                    selector
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filterselector">
+                    FilterSelector
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#defaultfilterselector">
+                    DefaultFilterSelector
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b0%83%e7%94%a8%e4%bb%a3%e7%a0%81">
+                    调用代码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#pipelineapplication">
+                    PipelineApplication
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#controller">
+                    controller
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#entity">
+                    entity
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#service">
+                    service
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness1">
+                    service.business1
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness1context">
+                    service.business1.context
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness1filters">
+                    service.business1.filters
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness1plugins">
+                    service.business1.plugins
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness2">
+                    service.business2
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness2context">
+                    service.business2.context
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness2filters">
+                    service.business2.filters
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness2plugins">
+                    service.business2.plugins
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#serviceconfig">
+                    service.config
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#serviceselector">
+                    service.selector
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#applicationyml">
+                    application.yml
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
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+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
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+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Java管道流设计模式结合业务</h2>
+                        <span id="post_page_title_date" class="date">2023.06.15</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="流程图">流程图</h2>
+<p><img alt="管道流设计结合业务-01" src="/iblog/posts/annex/images/essays/%E7%AE%A1%E9%81%93%E6%B5%81%E8%AE%BE%E8%AE%A1%E7%BB%93%E5%90%88%E4%B8%9A%E5%8A%A1-01.jpg"></p>
+<h2 id="代码实现">代码实现</h2>
+<p><img alt="管道流设计结合业务-02" src="/iblog/posts/annex/images/essays/%E7%AE%A1%E9%81%93%E6%B5%81%E8%AE%BE%E8%AE%A1%E7%BB%93%E5%90%88%E4%B8%9A%E5%8A%A1-02.jpg"></p>
+<p>完整代码：<a href="https://gitee.com/gitee_pikaqiu/easy-pipeline">https://gitee.com/gitee_pikaqiu/easy-pipeline</a></p>
+<h3 id="pom">pom</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-xml" data-lang="xml"><span class="line"><span class="cl"><span class="nt">&lt;dependencies&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-web<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.plugin<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-plugin-core<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>${spring.plugin.core.version}<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-test<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;scope&gt;</span>test<span class="nt">&lt;/scope&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.projectlombok<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>lombok<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;optional&gt;</span>true<span class="nt">&lt;/optional&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>cn.hutool<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>hutool-all<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>${hutool.version}<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl"><span class="nt">&lt;/dependencies&gt;</span>
+</span></span></code></pre></div><h3 id="context">context</h3>
+<h4 id="eventcontext">EventContext</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">EventContext</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 是否继续调用链
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">continueChain</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取当前过滤器选择器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">FilterSelector</span><span class="w"> </span><span class="nf">getFilterSelector</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="biztype">BizType</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">BizType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取业务类型码值
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 业务类型名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="abstracteventcontext">AbstractEventContext</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractEventContext</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">EventContext</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">BizType</span><span class="w"> </span><span class="n">businessType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="nf">AbstractEventContext</span><span class="p">(</span><span class="n">BizType</span><span class="w"> </span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">businessType</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">businessType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">filterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">continueChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="nf">getFilterSelector</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="filter">filter</h3>
+<h4 id="eventfilter">EventFilter</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">EventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 过滤逻辑封装点
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param context 上下文对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param chain   调用链
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">doFilter</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">,</span><span class="w"> </span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">chain</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="abstracteventfilter">AbstractEventFilter</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doFilter</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">,</span><span class="w"> </span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">chain</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">context</span><span class="p">.</span><span class="na">getFilterSelector</span><span class="p">().</span><span class="na">matchFilter</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getSimpleName</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">handler</span><span class="p">(</span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 是否继续执行调用链</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">context</span><span class="p">.</span><span class="na">continueChain</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">chain</span><span class="p">.</span><span class="na">nextHandler</span><span class="p">(</span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param context 上下文对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="eventfilterchain">EventFilterChain</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行当前过滤器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param context 上下文对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 跳过当前过滤器 执行下一个执行过滤器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param context 上下文对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">nextHandler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="filterchainpipeline">FilterChainPipeline</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">F</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&gt;</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">DefaultEventFilterChain</span><span class="o">&lt;</span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="n">last</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">F</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">append</span><span class="p">(</span><span class="n">F</span><span class="w"> </span><span class="n">filter</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultEventFilterChain</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">last</span><span class="p">,</span><span class="w"> </span><span class="n">filter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">F</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">append</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">description</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="n">filter</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;过滤器调用链管道开始设置 {} 过滤器&#34;</span><span class="p">,</span><span class="n">description</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultEventFilterChain</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">last</span><span class="p">,</span><span class="w"> </span><span class="n">filter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">DefaultEventFilterChain</span><span class="o">&lt;</span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getFilterChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">last</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="defaulteventfilterchain">DefaultEventFilterChain</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DefaultEventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filter</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">DefaultEventFilterChain</span><span class="p">(</span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="p">,</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filter</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">filter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filter</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">filter</span><span class="p">.</span><span class="na">doFilter</span><span class="p">(</span><span class="n">context</span><span class="p">,</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">nextHandler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">next</span><span class="p">.</span><span class="na">handler</span><span class="p">(</span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="selector">selector</h3>
+<h4 id="filterselector">FilterSelector</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">FilterSelector</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 匹配过滤器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param currentFilterName 过滤器名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 匹配成功
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">matchFilter</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">currentFilterName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取当前所有过滤器名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 过滤器名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getAllFilterNames</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="defaultfilterselector">DefaultFilterSelector</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DefaultFilterSelector</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FilterSelector</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w">  </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filterNames</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CollUtil</span><span class="p">.</span><span class="na">newArrayList</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">matchFilter</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">currentFilterName</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">filterNames</span><span class="p">.</span><span class="na">stream</span><span class="p">().</span><span class="na">anyMatch</span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">Objects</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">,</span><span class="n">currentFilterName</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getAllFilterNames</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">filterNames</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="调用代码">调用代码</h2>
+<p><img alt="管道流设计结合业务-03" src="/iblog/posts/annex/images/essays/%E7%AE%A1%E9%81%93%E6%B5%81%E8%AE%BE%E8%AE%A1%E7%BB%93%E5%90%88%E4%B8%9A%E5%8A%A1-03.jpg"></p>
+<h3 id="pipelineapplication">PipelineApplication</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@SpringBootApplication</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@EnablePluginRegistries</span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">Business1PostPlugin</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="n">Business2PostPlugin</span><span class="p">.</span><span class="na">class</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PipelineApplication</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SpringApplication</span><span class="p">.</span><span class="na">run</span><span class="p">(</span><span class="n">PipelineApplication</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="n">args</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="controller">controller</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@RestController</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/pipelineTest&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PipelineController</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Service</span><span class="w"> </span><span class="n">business1PipelineTestService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Service</span><span class="w"> </span><span class="n">business2PipelineTestService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/business1&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">business1</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PipelineRequestVo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setUuid</span><span class="p">(</span><span class="s">&#34;business1-1110-1111231afsas-123adss&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setBusinessCode</span><span class="p">(</span><span class="s">&#34;business1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Business1Model2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Business1Model1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business1PipelineTestService</span><span class="p">.</span><span class="na">doService</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/business2&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">business2</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PipelineRequestVo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setUuid</span><span class="p">(</span><span class="s">&#34;business2-1110-1111231afsas-123adss&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setBusinessCode</span><span class="p">(</span><span class="s">&#34;business2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setModel3</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Business2Model1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setModel4</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Business2Model2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business2PipelineTestService</span><span class="p">.</span><span class="na">doService</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="entity">entity</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PipelineRequestVo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uuid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">businessCode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Model2</span><span class="w"> </span><span class="n">model2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Model2</span><span class="w"> </span><span class="n">model4</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="service">service</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">enum</span><span class="w"> </span><span class="n">BusinessTypeEnum</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">BizType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BUSINESS_1</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="s">&#34;业务1&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BUSINESS_2</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="s">&#34;业务2&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BUSINESS_3</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="s">&#34;业务3&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">code</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness1">service.business1</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business1Service</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">doService</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1ServiceImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1Service</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Qualifier</span><span class="p">(</span><span class="s">&#34;business1PipelineSelectorFactory&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w">  </span><span class="n">PipelineSelectorFactory</span><span class="w"> </span><span class="n">business1PipelineSelectorFactory</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w">  </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business1PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w">  </span><span class="n">PluginRegistry</span><span class="o">&lt;</span><span class="n">Business1PostPlugin</span><span class="p">,</span><span class="w"> </span><span class="n">Business1Model1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business1PostPlugin</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doService</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============business1开始===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理器参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始获取FilterSelector===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">business1PipelineSelectorFactory</span><span class="p">.</span><span class="na">getFilterSelector</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Context</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Business1Context</span><span class="p">(</span><span class="n">BusinessTypeEnum</span><span class="p">.</span><span class="na">BUSINESS_1</span><span class="p">,</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;获取FilterSelector完成: {}&#34;</span><span class="p">,</span><span class="n">filterSelector</span><span class="p">.</span><span class="na">getAllFilterNames</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============获取FilterSelector完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始执行过滤器===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setPipelineTestRequest</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">getModel2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">getModel1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">filterChainPipeline</span><span class="p">.</span><span class="na">getFilterChain</span><span class="p">().</span><span class="na">handler</span><span class="p">(</span><span class="n">pipelineEventContext</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============执行过滤器完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理后获取值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始执行后置处理器===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model2</span><span class="w"> </span><span class="n">model2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getModel2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getPipelineTestRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business1PostPlugin</span><span class="p">.</span><span class="na">getPluginsFor</span><span class="p">(</span><span class="n">model1</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">handler</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">handler</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">model1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============执行后置处理器完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============business1结束===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness1context">service.business1.context</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Context</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventContext</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Model2</span><span class="w"> </span><span class="n">model2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Business1Context</span><span class="p">(</span><span class="n">BizType</span><span class="w"> </span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">continueChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Model1</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Model2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness1filters">service.business1.filters</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business1PipelineFilter</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">Business1Context</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Filter1</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">Business1Context</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1PipelineFilter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">Business1Context</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟操作数据库 等业务操作 可以利用门面模式进行解耦</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName1</span><span class="p">(</span><span class="s">&#34;张三&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName2</span><span class="p">(</span><span class="s">&#34;李四&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName3</span><span class="p">(</span><span class="s">&#34;王五&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model2</span><span class="w"> </span><span class="n">model2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;18&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;小白&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;Filter1执行完毕...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存入新的值到上下文对象中 下个处理器继续处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">model1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">model2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Filter2</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">Business1Context</span><span class="o">&gt;</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1PipelineFilter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">Business1Context</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟操作数据库 等业务操作 可以利用门面模式进行解耦</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName1</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName1</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName2</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName2</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName3</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName3</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">100</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;Filter2执行完毕...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存入新的值到上下文对象中 下个处理器继续处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">model1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">context</span><span class="p">.</span><span class="na">getModel2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness1plugins">service.business1.plugins</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business1PostPlugin</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Plugin</span><span class="o">&lt;</span><span class="n">Business1Model1</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param model 处理参数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1ServicePluginImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1PostPlugin</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">supports</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===&gt;{}&#34;</span><span class="p">,</span><span class="n">model</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1ServicePluginImpl2</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1PostPlugin</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">supports</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===&gt;{}&#34;</span><span class="p">,</span><span class="n">model</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness2">service.business2</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business2Service</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">doService</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2ServiceImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2Service</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Qualifier</span><span class="p">(</span><span class="s">&#34;business2PipelineSelectorFactory&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PipelineSelectorFactory</span><span class="w"> </span><span class="n">business2PipelineSelectorFactory</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business2PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PluginRegistry</span><span class="o">&lt;</span><span class="n">Business2PostPlugin</span><span class="p">,</span><span class="w"> </span><span class="n">Business2Model1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business2PostPlugin</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doService</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============business2开始===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理器参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始获取FilterSelector===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">business2PipelineSelectorFactory</span><span class="p">.</span><span class="na">getFilterSelector</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Context</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Business2Context</span><span class="p">(</span><span class="n">BusinessTypeEnum</span><span class="p">.</span><span class="na">BUSINESS_2</span><span class="p">,</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;获取FilterSelector完成: {}&#34;</span><span class="p">,</span><span class="n">filterSelector</span><span class="p">.</span><span class="na">getAllFilterNames</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============获取FilterSelector完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始执行过滤器===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setPipelineTestRequest</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">getModel4</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">getModel3</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">filterChainPipeline</span><span class="p">.</span><span class="na">getFilterChain</span><span class="p">().</span><span class="na">handler</span><span class="p">(</span><span class="n">pipelineEventContext</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============执行过滤器完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理后获取值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始执行后置处理器===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model2</span><span class="w"> </span><span class="n">model2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getModel2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getPipelineTestRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business2PostPlugin</span><span class="p">.</span><span class="na">getPluginsFor</span><span class="p">(</span><span class="n">model1</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">handler</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">handler</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">model1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============执行后置处理器完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============business2结束===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness2context">service.business2.context</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Context</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventContext</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Model2</span><span class="w"> </span><span class="n">model2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Business2Context</span><span class="p">(</span><span class="n">BizType</span><span class="w"> </span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">continueChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Model1</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Model2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness2filters">service.business2.filters</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business2PipelineFilter</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">Business2Context</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Filter1</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">Business2Context</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2PipelineFilter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">Business2Context</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟操作数据库 等业务操作 可以利用门面模式进行解耦</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName1</span><span class="p">(</span><span class="s">&#34;张三&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName2</span><span class="p">(</span><span class="s">&#34;李四&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName3</span><span class="p">(</span><span class="s">&#34;王五&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model2</span><span class="w"> </span><span class="n">model2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;18&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;小白&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;Filter1执行完毕...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存入新的值到上下文对象中 下个处理器继续处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">model1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">model2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Filter2</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">Business2Context</span><span class="o">&gt;</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2PipelineFilter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">Business2Context</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟操作数据库 等业务操作 可以利用门面模式进行解耦</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName1</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName1</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName2</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName2</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName3</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName3</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">100</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;Filter2执行完毕...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存入新的值到上下文对象中 下个处理器继续处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">model1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">context</span><span class="p">.</span><span class="na">getModel2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness2plugins">service.business2.plugins</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business2PostPlugin</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Plugin</span><span class="o">&lt;</span><span class="n">Business2Model1</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param model 处理参数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2ServicePluginImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2PostPlugin</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">supports</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===&gt;{}&#34;</span><span class="p">,</span><span class="n">model</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2ServicePluginImpl2</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2PostPlugin</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">supports</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===&gt;{}&#34;</span><span class="p">,</span><span class="n">model</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="serviceconfig">service.config</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@ConfigurationProperties</span><span class="p">(</span><span class="n">prefix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;test&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FilterConfigProperties</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">configs</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="nf">getConfigs</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">configs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">configs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MapUtil</span><span class="p">.</span><span class="na">newHashMap</span><span class="p">(</span><span class="n">16</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">configs</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PipelineFilterConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Business1PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business1PipelineFilter</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business1PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business1FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Business2PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business2PipelineFilter</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business2PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business2FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">FilterConfigProperties</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business1PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">business1ChargePipeline</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">configs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">.</span><span class="na">getConfigs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">business1PipelineFilter</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">configs</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">business1FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">Map</span><span class="p">.</span><span class="na">Entry</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">filtersName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">configs</span><span class="p">.</span><span class="na">entrySet</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">distinctCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filtersName</span><span class="p">.</span><span class="na">stream</span><span class="p">().</span><span class="na">distinct</span><span class="p">().</span><span class="na">count</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">distinctCount</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">business1PipelineFilter</span><span class="p">.</span><span class="na">size</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;设置的过滤器数量大于实际过滤器数量&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business1PipelineFilter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">stream</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">sorted</span><span class="p">(</span><span class="n">Comparator</span><span class="p">.</span><span class="na">comparing</span><span class="p">(</span><span class="n">Business1PipelineFilter</span><span class="p">::</span><span class="n">order</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">business1FilterChainPipeline</span><span class="p">::</span><span class="n">append</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">business1FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business2PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">business2ChargePipeline</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">configs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">.</span><span class="na">getConfigs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">business2PipelineFilter</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">configs</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">business2FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">Map</span><span class="p">.</span><span class="na">Entry</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">filtersName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">configs</span><span class="p">.</span><span class="na">entrySet</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">distinctCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filtersName</span><span class="p">.</span><span class="na">stream</span><span class="p">().</span><span class="na">distinct</span><span class="p">().</span><span class="na">count</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">distinctCount</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">business2PipelineFilter</span><span class="p">.</span><span class="na">size</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;设置的过滤器数量大于实际过滤器数量&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business2PipelineFilter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">stream</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">sorted</span><span class="p">(</span><span class="n">Comparator</span><span class="p">.</span><span class="na">comparing</span><span class="p">(</span><span class="n">Business2PipelineFilter</span><span class="p">::</span><span class="n">order</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">business2FilterChainPipeline</span><span class="p">::</span><span class="n">append</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">business2FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="serviceselector">service.selector</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PipelineSelectorFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">FilterSelector</span><span class="w">  </span><span class="nf">getFilterSelector</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;business1PipelineSelectorFactory&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1PipelineSelectorFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PipelineSelectorFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">FilterConfigProperties</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="nf">getFilterSelector</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">businessCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">request</span><span class="p">.</span><span class="na">getBusinessCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DefaultFilterSelector</span><span class="w"> </span><span class="n">defaultFilterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultFilterSelector</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">businessCode</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;business1&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">defaultFilterSelector</span><span class="p">.</span><span class="na">setFilterNames</span><span class="p">(</span><span class="n">filterConfigProperties</span><span class="p">.</span><span class="na">getConfigs</span><span class="p">().</span><span class="na">getOrDefault</span><span class="p">(</span><span class="n">businessCode</span><span class="p">,</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">unmodifiableList</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">())));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">defaultFilterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;business2PipelineSelectorFactory&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2PipelineSelectorFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PipelineSelectorFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">FilterConfigProperties</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="nf">getFilterSelector</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">businessCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">request</span><span class="p">.</span><span class="na">getBusinessCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DefaultFilterSelector</span><span class="w"> </span><span class="n">defaultFilterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultFilterSelector</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">businessCode</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;business2&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">defaultFilterSelector</span><span class="p">.</span><span class="na">setFilterNames</span><span class="p">(</span><span class="n">filterConfigProperties</span><span class="p">.</span><span class="na">getConfigs</span><span class="p">().</span><span class="na">getOrDefault</span><span class="p">(</span><span class="n">businessCode</span><span class="p">,</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">unmodifiableList</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">())));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">defaultFilterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="applicationyml">application.yml</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="nt">server</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">port</span><span class="p">:</span><span class="w"> </span><span class="m">8080</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">test</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">configs</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">business1</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span>- <span class="l">Business1Filter1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span>- <span class="l">Business1Filter2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">business2</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span>- <span class="l">Business2Filter1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span>- <span class="l">Business2Filter2</span><span class="w">
+</span></span></span></code></pre></div></div>
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diff --git a/blog-site/public/posts/toy/uploadfile-code/index.html b/blog-site/public/posts/toy/uploadfile-code/index.html
new file mode 100644
index 00000000..d8d1ac29
--- /dev/null
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@@ -0,0 +1,2184 @@
+<!DOCTYPE html>
+<html lang="zh" >
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#abstractdownloadmanagement">
+                    AbstractDownloadManagement
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypefileconfig">
+                    ArchetypeFileConfig
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypefileplatformtype">
+                    ArchetypeFilePlatformType
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#fileconstant">
+                    FileConstant
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filefacade">
+                    FileFacade
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filemanagementbridge">
+                    FileManagementBridge
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#downloadfileextensions">
+                    DownloadFileExtensions
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#uploadfileextensions">
+                    UploadFileExtensions
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%98%bf%e9%87%8c%e4%ba%91">
+                    阿里云
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#aliyunfileconfig">
+                    AliyunFileConfig
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypealiyundownload">
+                    ArchetypeAliyunDownload
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypealiyunupload">
+                    ArchetypeAliyunUpload
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#fastdfs">
+                    fastdfs
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#fastdfsconfig">
+                    FastDfsConfig
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypefastdfsdownload">
+                    ArchetypeFastDfsDownload
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypefastdfsupload">
+                    ArchetypeFastDfsUpload
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%ac%e5%9c%b0">
+                    本地
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#localfileconfig">
+                    LocalFileConfig
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypelocaldownload">
+                    ArchetypeLocalDownload
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypelocalupload">
+                    ArchetypeLocalUpload
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b0%83%e7%94%a8%e6%b5%8b%e8%af%95">
+                    调用测试
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filetest">
+                    FileTest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="http://localhost:1313/iblog/">首页</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="http://localhost:1313/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="http://localhost:1313/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="http://localhost:1313/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1688701481347" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3517" width="16" height="16"><path d="M425.610455 85.814544H149.05897A42.303635 42.303635 0 0 0 106.6274 128.075535V896.492068c0 23.326702 18.976933 42.26099 42.43157 42.26099h682.743143a42.559504 42.559504 0 0 0 42.431569-42.559504v-384.016365a42.644793 42.644793 0 0 1 85.289587 0v384.016365A127.849091 127.849091 0 0 1 831.802113 1024H149.05897A127.635867 127.635867 0 0 1 21.337813 896.449423V128.03289A127.593222 127.593222 0 0 1 149.101614 0.524957h276.466196a42.644793 42.644793 0 0 1 0 85.289587z m564.062683 158.08425l-170.579174 170.579173a42.644793 42.644793 0 1 1-60.299738-60.299738L856.578738 256.393718H618.364922a42.644793 42.644793 0 1 1 0-85.289587h238.213816l-97.784512-97.784511A42.644793 42.644793 0 1 1 819.093964 13.019882l170.579174 170.579174a42.644793 42.644793 0 0 1 0 60.299738zM149.272194 597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h51.514911c59.190973 0 107.891327 23.284057 107.976617 97.102195 0 71.003581-49.46796 102.347504-106.185536 102.347504h-31.343923v66.781747a32.282109 32.282109 0 0 1-64.606862 0V597.552066z m92.709781 100.215264c31.429213 0 46.568114-16.46089 46.568114-45.757863 0-30.064579-17.313786-40.512554-48.359196-40.512554h-26.311837v86.270417h28.145563z m232.414124-142.860058c81.878003 0 136.036891 43.710913 136.036891 147.67892S556.231457 853.420826 477.935617 853.420826h-38.16709a42.644793 42.644793 0 0 1-42.644794-42.644793v-213.223967a42.644793 42.644793 0 0 1 42.644794-42.644794h34.542282z m-4.008611 240.729859c43.32711 0 73.988717-22.047358 73.988717-93.050939 0-71.046226-30.704251-90.705476-73.988717-90.705476h-8.699538v183.79906h8.699538zM692.481573 853.420826a32.282109 32.282109 0 0 1-32.282109-32.282108V597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h99.063855a29.680776 29.680776 0 1 1 0 59.404197h-77.144431v65.374469h61.749661a29.894 29.894 0 1 1 0 59.788h-61.749661v81.66478a32.282109 32.282109 0 0 1-32.282108 32.282108z" fill="#5f5f5f" p-id="3518"></path></svg>
+                    </a>
+                    <a id="export_pic" title="导出图片" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1689071509720" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="4564" width="16" height="16"><path d="M909.132886 0.037506h-184.960611a33.909445 33.909445 0 0 0-32.368107 33.909445 33.909445 33.909445 0 0 0 33.909445 33.395666h158.244078l-200.373995 199.346437a33.395666 33.395666 0 0 0 0 47.781491 31.854327 31.854327 0 0 0 23.633856 9.76181 33.909445 33.909445 0 0 0 24.147635-9.76181l198.832657-199.346437V272.340628a33.909445 33.909445 0 0 0 69.874009 0V88.921355A88.37007 88.37007 0 0 0 909.132886 0.037506zM216.558153 347.866211a107.37991 107.37991 0 1 0 107.37991-107.379911 107.89369 107.89369 0 0 0-107.37991 107.379911z m154.133843 0a51.377948 51.377948 0 0 1-97.618101 0 51.377948 51.377948 0 1 1 97.618101 0z" p-id="4565" fill="#424242"></path><path d="M963.079731 437.777619a34.423225 34.423225 0 0 0-33.909446 33.909445v265.110209a1811.07265 1811.07265 0 0 0-137.692899-193.181082 106.352351 106.352351 0 0 0-78.60826-36.478343 123.820854 123.820854 0 0 0-82.204716 35.964563l-3.596456 3.082677-188.557068 176.74014c-11.816928-13.358266-47.781491-51.377948-82.204716-87.856291a83.232275 83.232275 0 0 0-85.801172-21.578738 105.324792 105.324792 0 0 0-38.019681 19.52362l-141.289356 121.765736V89.948914a22.092517 22.092517 0 0 1 22.606297-22.606297h417.702713a33.395666 33.395666 0 0 0 33.395666-33.909445 33.395666 33.395666 0 0 0-33.395666-33.395666H113.802258A89.911408 89.911408 0 0 0 23.89085 89.948914v844.139678a89.911408 89.911408 0 0 0 89.911408 89.911408h793.27551a89.911408 89.911408 0 0 0 89.397629-89.911408v-462.401528a33.909445 33.909445 0 0 0-33.395666-33.909445z m-33.909446 496.310973a22.606297 22.606297 0 0 1-22.092517 22.606297H113.802258a22.606297 22.606297 0 0 1-22.606297-22.606297v-88.37007l183.933052-160.812976a43.157476 43.157476 0 0 1 15.413385-7.192912 15.927164 15.927164 0 0 1 17.982281 5.137794c37.505902 36.478343 78.60826 83.232275 82.718496 87.856291a61.653537 61.653537 0 0 0 42.643696 22.092517 62.681096 62.681096 0 0 0 51.377948-20.037399c8.220472-8.220472 134.610223-125.875971 194.208641-181.877935a57.029522 57.029522 0 0 1 34.423225-16.440943 45.212594 45.212594 0 0 1 29.79921 15.927164 2954.231982 2954.231982 0 0 1 186.501949 256.889738z" p-id="4566" fill="#424242"></path></svg>
+                    </a>
+                    <a id="export_markdown" title="导出markdown" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_doc" title="导出文档" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1689246982401" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="6825" width="16" height="16"><path d="M270.76864 608.32h180.8a31.68 31.68 0 0 0 0-62.976H270.76864a31.68 31.68 0 0 0 0 62.976zM271.34464 458.56h457.92a33.472 33.472 0 0 0 31.552-34.752 33.28 33.28 0 0 0-31.552-34.624H271.34464a34.816 34.816 0 0 0 0 69.376zM271.34464 293.504h457.92a33.344 33.344 0 0 0 31.552-34.688 33.216 33.216 0 0 0-31.552-34.624H271.34464a33.28 33.28 0 0 0-31.616 34.624 33.28 33.28 0 0 0 31.616 34.688z" p-id="6826" fill="#424242"></path><path d="M869.87264 0H153.77664A70.4 70.4 0 0 0 84.65664 70.912V953.6A69.952 69.952 0 0 0 153.77664 1024h370.048a32 32 0 0 0 0-63.68H147.12064V64h729.6v468.672a31.296 31.296 0 1 0 62.528 0V70.912A70.4 70.4 0 0 0 869.87264 0z" p-id="6827" fill="#424242"></path><path d="M482.16064 730.624h337.664L715.82464 625.216a28.864 28.864 0 0 1-7.936-28.736 29.184 29.184 0 0 1 20.608-21.184 29.632 29.632 0 0 1 29.12 8.128l174.784 177.216-174.784 176.96a29.184 29.184 0 0 1-49.728-13.312 29.248 29.248 0 0 1 8-28.8l103.936-105.344H482.16064a29.696 29.696 0 0 1-29.504-29.76 29.632 29.632 0 0 1 29.504-29.76z" p-id="6828" fill="#424242"></path></svg>
+                    </a>
+                </span>
+                <a  id="icon_more" title="更多" >
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+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">整合文件上传功能</h2>
+                        <span id="post_page_title_date" class="date">2023.08.11</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="结构">结构</h2>
+<p><img alt="整合文件上传功能" src="/iblog/posts/annex/images/essays/%E6%95%B4%E5%90%88%E6%96%87%E4%BB%B6%E4%B8%8A%E4%BC%A0%E5%8A%9F%E8%83%BD-01.jpg"></p>
+<h2 id="pomxml">pom.xml</h2>
+<p>fastdfs-client-java-1.27.jar：<a href="/iblog/posts/annex/jar/lib/fastdfs-client-java-1.27.jar">点击下载</a></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-xml" data-lang="xml"><span class="line"><span class="cl">    <span class="nt">&lt;dependencies&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c">&lt;!-- fastdfs --&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>org.csource<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>fastdfs-client-java<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;version&gt;</span>1.27<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;systemPath&gt;</span>${project.basedir}/lib/fastdfs-client-java-1.27.jar<span class="nt">&lt;/systemPath&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;scope&gt;</span>system<span class="nt">&lt;/scope&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c">&lt;!--aliyun oss 依赖--&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>com.aliyun.oss<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>aliyun-sdk-oss<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-web<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-test<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;scope&gt;</span>test<span class="nt">&lt;/scope&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>org.projectlombok<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>lombok<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;optional&gt;</span>true<span class="nt">&lt;/optional&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>cn.hutool<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>hutool-all<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;version&gt;</span>5.8.11<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>commons-io<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>commons-io<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;version&gt;</span>2.11.0<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependencies&gt;</span>
+</span></span></code></pre></div><h2 id="applicationyml">application.yml</h2>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yml" data-lang="yml"><span class="line"><span class="cl"><span class="nt">server</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">port</span><span class="p">:</span><span class="w"> </span><span class="m">80</span><span class="w">
+</span></span></span></code></pre></div><h2 id="公共部分">公共部分</h2>
+<h3 id="filemanagement">FileManagement</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">FileManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 设置下一个bean的对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param nextFileManagement 下一个bean对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNext</span><span class="p">(</span><span class="n">FileManagement</span><span class="w"> </span><span class="n">nextFileManagement</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="filebeanmanagement">FileBeanManagement</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FileBeanManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;uploadChain&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="nf">uploadChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">buildChain</span><span class="p">(</span><span class="n">AbstractUploadManagement</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;downloadChain&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="nf">downloadChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">buildChain</span><span class="p">(</span><span class="n">AbstractDownloadManagement</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 设置文件管理bean调用链(环状链)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param type   文件管理类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param isRing 是否形成环形链表
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param &lt;T&gt;    extends FileManagement 指定类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return bean
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">FileManagement</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">buildChain</span><span class="p">(</span><span class="n">Class</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">type</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isRing</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">beans</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">SpringUtil</span><span class="p">.</span><span class="na">getBeansOfType</span><span class="p">(</span><span class="n">type</span><span class="p">).</span><span class="na">values</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 设置调用链</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">index</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断是否到最后一个bean 如果到了最后一个bean将第一个bean设置为尾部的下一个节点 形成环状结构</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">beans</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">index</span><span class="p">).</span><span class="na">setNext</span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">isRing</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="abstractuploadmanagement">AbstractUploadManagement</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractUploadManagement</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FileManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="n">self</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNext</span><span class="p">(</span><span class="n">FileManagement</span><span class="w"> </span><span class="n">fileManagement</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">self</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">AbstractUploadManagement</span><span class="p">)</span><span class="n">fileManagement</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">allowUploadFiles</span><span class="p">(</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowFiles</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getAllowFiles</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">FileConstant</span><span class="p">.</span><span class="na">DEFAULT_ALLOWED_EXTENSION</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 判断是否是当前平台处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType 指定平台类型 {@linkplain ArchetypeFilePlatformType}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 为当前平台处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 校验允许上传的文件格式; 默认{@code  FileTypeUtils.DEFAULT_ALLOWED_EXTENSION}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileName 文件名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 允许上传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">checkAllowUploadFiles</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileName</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">fileName</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowUploadFiles</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">allowUploadFiles</span><span class="p">(</span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">allowUploadFile</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">allowUploadFiles</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">fileName</span><span class="p">.</span><span class="na">toLowerCase</span><span class="p">().</span><span class="na">endsWith</span><span class="p">(</span><span class="n">allowUploadFile</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;当前上传文件仅支持 [{}] 格式&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">allowUploadFiles</span><span class="p">.</span><span class="na">toArray</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 校验允许上传的文件大小
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param bytes 字节数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 允许上传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w">  </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">checkSingleAllowUploadSize</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">bytes</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getAllowFileSize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 前置处理 预留方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 允许上传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传成功后的路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理 预留方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileUri 上传成功后的路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 文件上传路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileUri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 多上传文件模板方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileConfig    文件上传配置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传成功后的文件uri集合
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">uploadTemplate</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">multipartFile</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">emptyList</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">filePlatformType</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getFilePlatformType</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 检索上传文件平台类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">self</span><span class="p">.</span><span class="na">isCurrentPlatform</span><span class="p">(</span><span class="n">filePlatformType</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">uploadTemplate</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 多文件上传需要加循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">fileUriList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">self</span><span class="p">.</span><span class="na">beforeCheck</span><span class="p">(</span><span class="n">file</span><span class="p">,</span><span class="n">fileConfig</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">fileUriList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">self</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">self</span><span class="p">.</span><span class="na">upload</span><span class="p">(</span><span class="n">file</span><span class="p">,</span><span class="n">fileConfig</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;上传文件=&gt; 平台类型:[{}]\t 上传路径:[{}]&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">filePlatformType</span><span class="p">,</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">fileUriList</span><span class="p">.</span><span class="na">toArray</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileUriList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件前置校验
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true校验成功允许上传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">beforeCheck</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">!</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getSize</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">checkAllowUploadFiles</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">(),</span><span class="n">fileConfig</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">checkSingleAllowUploadSize</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(),</span><span class="n">fileConfig</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">preProcessing</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="n">fileConfig</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="abstractdownloadmanagement">AbstractDownloadManagement</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractDownloadManagement</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FileManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="n">self</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNext</span><span class="p">(</span><span class="n">FileManagement</span><span class="w"> </span><span class="n">fileManagement</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">self</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">AbstractDownloadManagement</span><span class="p">)</span><span class="n">fileManagement</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 前置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          下载文件的地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true-允许执行后置操作
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          下载文件地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 下载到的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param downloadFile 下载的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 经过后置处理下载后的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 判断是否是当前平台处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType 指定平台类型 {@linkplain ArchetypeFilePlatformType}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 为当前平台处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文件下载模板方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType 平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          文件地址,支持本地和http地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return file对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">downloadTemplate</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 检索上传文件平台类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">self</span><span class="p">.</span><span class="na">isCurrentPlatform</span><span class="p">(</span><span class="n">platformType</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">downloadTemplate</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 前置下载校验</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">self</span><span class="p">.</span><span class="na">preProcessing</span><span class="p">(</span><span class="n">uri</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">CharSequenceUtil</span><span class="p">.</span><span class="na">EMPTY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 下载文件到指定路径</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">self</span><span class="p">.</span><span class="na">download</span><span class="p">(</span><span class="n">uri</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">,</span><span class="w"> </span><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">fileLength</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;下载文件平台类型: {} 文件大小为:{} MB&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DecimalFormat</span><span class="p">(</span><span class="s">&#34;0.00&#34;</span><span class="p">).</span><span class="na">format</span><span class="p">(</span><span class="n">fileLength</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">1024</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1024</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取文件名称</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">split</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">uri</span><span class="p">.</span><span class="na">split</span><span class="p">(</span><span class="n">platformType</span><span class="p">.</span><span class="na">getFileSeparator</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">fullFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">split</span><span class="o">[</span><span class="n">split</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">fileNameWithSuffix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fullFileName</span><span class="p">.</span><span class="na">split</span><span class="p">(</span><span class="s">&#34;\\.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 指定存放位置(有需求可以自定义)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">path</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;%s%s%s_%s.%s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p">.</span><span class="na">separatorChar</span><span class="p">,</span><span class="w"> </span><span class="n">fileNameWithSuffix</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">DateUtil</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(),</span><span class="w"> </span><span class="s">&#34;yyyyMMddHHmmss&#34;</span><span class="p">),</span><span class="w"> </span><span class="n">fileNameWithSuffix</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">path</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 校验文件夹目录是否存在，不存在就创建一个目录</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">file</span><span class="p">.</span><span class="na">getParentFile</span><span class="p">().</span><span class="na">exists</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">file</span><span class="p">.</span><span class="na">getParentFile</span><span class="p">().</span><span class="na">mkdirs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 写入文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@Cleanup</span><span class="w"> </span><span class="n">OutputStream</span><span class="w"> </span><span class="n">out</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Files</span><span class="p">.</span><span class="na">newOutputStream</span><span class="p">(</span><span class="n">file</span><span class="p">.</span><span class="na">toPath</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@Cleanup</span><span class="w"> </span><span class="n">BufferedInputStream</span><span class="w"> </span><span class="n">bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedInputStream</span><span class="p">(</span><span class="n">inputStream</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">buf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">2048</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bin</span><span class="p">.</span><span class="na">read</span><span class="p">(</span><span class="n">buf</span><span class="p">))</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">len</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">out</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">log</span><span class="p">.</span><span class="na">isDebugEnabled</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;下载文件 {} 进度 =&gt;{}%&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fullFileName</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">100L</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">fileLength</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;{} 文件下载成功！&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">path</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">file</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">defaultHttpDownload</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 建立 http 下载连接 建立链接从请求中获取数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HttpURLConnection</span><span class="w"> </span><span class="n">httpUrlConnection</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">HttpURLConnection</span><span class="p">)</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">URL</span><span class="p">(</span><span class="n">uri</span><span class="p">).</span><span class="na">openConnection</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">setConnectTimeout</span><span class="p">(</span><span class="n">10</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">setRequestMethod</span><span class="p">(</span><span class="s">&#34;GET&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">setRequestProperty</span><span class="p">(</span><span class="s">&#34;Charset&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;UTF-8&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">connect</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">download</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">,</span><span class="w"> </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">getInputStream</span><span class="p">(),</span><span class="w"> </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">getContentLength</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypefileconfig">ArchetypeFileConfig</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">ArchetypeFileConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文件平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="nf">getFilePlatformType</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getAllowFiles</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件大小; 单位字节
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Long</span><span class="w"> </span><span class="nf">getAllowFileSize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypefileplatformtype">ArchetypeFilePlatformType</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">enum</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 上传下载文件平台类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">LOCAL</span><span class="p">(</span><span class="s">&#34;\\\\&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ALIYUN</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">TENCEN_CLOUD</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">FAST_DFS</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件分隔符
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">fileSeparator</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="fileconstant">FileConstant</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">FileConstant</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">IMAGE_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;bmp&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;gif&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;jpg&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;jpeg&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;png&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">FLASH_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;swf&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;flv&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">MEDIA_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;swf&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;flv&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;mp3&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;wav&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;wma&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;wmv&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;mid&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;avi&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;mpg&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;asf&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;rm&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;rmvb&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">VIDEO_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;mp4&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;avi&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;rmvb&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">DEFAULT_ALLOWED_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 图片</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;bmp&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;gif&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;jpg&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;jpeg&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;png&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// word excel powerpoint</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;doc&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;docx&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;xls&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;xlsx&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;ppt&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;pptx&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;html&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;htm&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;txt&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;rar&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;zip&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;gz&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;bz2&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 视频格式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;mp4&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;avi&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;rmvb&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// pdf</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;pdf&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="filefacade">FileFacade</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">FileFacade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileConfig    文件上传配置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传后的文件地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">default</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">upload</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">UploadFileExtensions</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">uploadUriList</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">uploadUriList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileConfig    文件上传配置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传后的文件地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">default</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">,</span><span class="w"> </span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">upload</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileConfig     文件上传配置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile  上传的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileExtensions 文件扩展接口; 可在文件上传之前,上传之后进行操作
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传后的文件地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">,</span><span class="w"> </span><span class="n">UploadFileExtensions</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType 指定平台类型{@linkplain ArchetypeFilePlatformType}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          文件地址; 支持本地,http
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 下载的文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">default</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="nd">@NotNull</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="nd">@NotNull</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">download</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DownloadFileExtensions</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">public</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType   指定平台类型{@linkplain ArchetypeFilePlatformType}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri            文件地址; 支持本地,http
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileExtensions 下载文件扩展接口;可在下载上传之前,下载之后进行操作
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 下载的文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">DownloadFileExtensions</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="filemanagementbridge">FileManagementBridge</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FileManagementBridge</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FileFacade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Resource</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;uploadChain&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="n">uploadChain</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Resource</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;downloadChain&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="n">downloadChain</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">,</span><span class="w"> </span><span class="n">UploadFileExtensions</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ObjectUtil</span><span class="p">.</span><span class="na">isAllEmpty</span><span class="p">(</span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getFilePlatformType</span><span class="p">(),</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;upload file need param (platformType:[%s] multipartFile:[%s] maybe is empty.&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getFilePlatformType</span><span class="p">(),</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">fileExtensions</span><span class="p">.</span><span class="na">preProcessing</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">emptyList</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">uploadChain</span><span class="p">.</span><span class="na">uploadTemplate</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">DownloadFileExtensions</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ObjectUtil</span><span class="p">.</span><span class="na">isAllEmpty</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;download file need param ( platformType:[%s] uri:[%s] ) maybe is empty.&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">fileExtensions</span><span class="p">.</span><span class="na">preProcessing</span><span class="p">(</span><span class="n">uri</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">CharSequenceUtil</span><span class="p">.</span><span class="na">EMPTY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">downloadChain</span><span class="p">.</span><span class="na">downloadTemplate</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="downloadfileextensions">DownloadFileExtensions</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">DownloadFileExtensions</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件-前置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri 下载的uri
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true-允许下载;false-不允许下载
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件-后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          下载的uri
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param downloadFile 下载的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 经过后置处理的下载的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="uploadfileextensions">UploadFileExtensions</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">UploadFileExtensions</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件-前置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传的文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true-能继续处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件-后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uploadUriList 上传文件返回的uri地址集合
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 经过后置处理返回的uri地址集合
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">uploadUriList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="阿里云">阿里云</h2>
+<h3 id="aliyunfileconfig">AliyunFileConfig</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;aliyunFileConfig&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AliyunFileConfig</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 填写Bucket所在地域对应的Endpoint，可在创建好的Bucket概况页查看
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">endpoint</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 阿里云账号AccessKey里所对应的AccessKey ID
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">accessKeyId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 阿里云账号AccessKey里所对应的AccessKey Secret
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">accessKeySecret</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * OSS对象存储空间名
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">bucketName</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件大小; 单位字节
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">allowFileSize</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="nf">getFilePlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">ALIYUN</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypealiyundownload">ArchetypeAliyunDownload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeAliyunDownload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeAliyunDownload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypealiyunupload">ArchetypeAliyunUpload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeAliyunUpload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeAliyunUpload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">ALIYUN</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AliyunFileConfig</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">((</span><span class="n">AliyunFileConfig</span><span class="p">)</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OSS</span><span class="w"> </span><span class="n">ossClient</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">OSSClientBuilder</span><span class="p">().</span><span class="na">build</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getEndpoint</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getAccessKeyId</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getAccessKeySecret</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 上传文件流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getInputStream</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">fileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">fileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">().</span><span class="na">replaceAll</span><span class="p">(</span><span class="s">&#34;-&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">fileName</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 按照当前日期，创建文件夹，上传到创建文件夹里面 20220315/xx.jpg</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">fileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DateUtil</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="n">DateUtil</span><span class="p">.</span><span class="na">date</span><span class="p">(),</span><span class="w"> </span><span class="s">&#34;yyyyMMdd&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">ALIYUN</span><span class="p">.</span><span class="na">getFileSeparator</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">fileName</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ossClient</span><span class="p">.</span><span class="na">putObject</span><span class="p">(</span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getBucketName</span><span class="p">(),</span><span class="w"> </span><span class="n">fileName</span><span class="p">,</span><span class="w"> </span><span class="n">inputStream</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ossClient</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;https://%s.%s/%s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getBucketName</span><span class="p">(),</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getEndpoint</span><span class="p">(),</span><span class="w"> </span><span class="n">fileName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileUri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileUri</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="fastdfs">fastdfs</h2>
+<h3 id="fastdfsconfig">FastDfsConfig</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;fastDfsConfig&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FastDfsConfig</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 编码
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">charset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 连接超时事件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">connectTimeoutInSecond</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 网络超时时间
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">networkTimeoutInSeconds</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * track端口
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">httpTrackerHttpPort</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * http令牌
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">httpAntiStealToken</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 服务器地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">trackerServers</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">storageServiceIp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">storageServicePort</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">storageServicePathIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件大小; 单位字节
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">allowFileSize</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="nf">getFilePlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">FAST_DFS</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypefastdfsdownload">ArchetypeFastDfsDownload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeFastDfsDownload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@DependsOn</span><span class="p">({</span><span class="s">&#34;fastDfsConfig&#34;</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeFastDfsDownload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypefastdfsupload">ArchetypeFastDfsUpload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeFastDfsUpload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeFastDfsUpload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">FAST_DFS</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FastDfsConfig</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">FastDfsConfig</span><span class="p">)</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">init</span><span class="p">(</span><span class="n">fastDfsConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">originalFilename</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">suffix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">originalFilename</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">originalFilename</span><span class="p">.</span><span class="na">lastIndexOf</span><span class="p">(</span><span class="s">&#34;.&#34;</span><span class="p">)</span><span class="o">+</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StorageClient</span><span class="w"> </span><span class="n">storageClient</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StorageClient</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StorageServer</span><span class="p">(</span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getStorageServiceIp</span><span class="p">(),</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getStorageServicePort</span><span class="p">(),</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getStorageServicePathIndex</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">strings</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">storageClient</span><span class="p">.</span><span class="na">upload_file</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(),</span><span class="w"> </span><span class="n">suffix</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;http://%s:%s/%s&#34;</span><span class="p">,</span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getStorageServiceIp</span><span class="p">(),</span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getHttpTrackerHttpPort</span><span class="p">(),</span><span class="n">StrUtil</span><span class="p">.</span><span class="na">join</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">,</span><span class="n">strings</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">init</span><span class="p">(</span><span class="n">FastDfsConfig</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 先从容器获取如果没有在加载 fixme</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 文件服务器客户端初始化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Properties</span><span class="w"> </span><span class="n">properties</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Properties</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.connect_timeout_in_seconds&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getConnectTimeoutInSecond</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.network_timeout_in_seconds&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getNetworkTimeoutInSeconds</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.charset&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getCharset</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.http_tracker_http_port&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getHttpTrackerHttpPort</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.http_anti_steal_token&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getHttpAntiStealToken</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.tracker_servers&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getTrackerServers</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ClientGlobal</span><span class="p">.</span><span class="na">initByProperties</span><span class="p">(</span><span class="n">properties</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;fastdfs客户端初始化成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileUri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileUri</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="本地">本地</h2>
+<h3 id="localfileconfig">LocalFileConfig</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;localFileConfig&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">LocalFileConfig</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件大小; 单位字节
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">allowFileSize</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传的路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uploadPath</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件到指定路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="nf">getFilePlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypelocaldownload">ArchetypeLocalDownload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@DependsOn</span><span class="p">({</span><span class="s">&#34;localFileConfig&#34;</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeLocalDownload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeLocalDownload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">LocalFileConfig</span><span class="w"> </span><span class="n">localFileConfig</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">localFileConfig</span><span class="p">.</span><span class="na">getDownloadPath</span><span class="p">(),</span><span class="w"> </span><span class="n">Files</span><span class="p">.</span><span class="na">newInputStream</span><span class="p">(</span><span class="n">Paths</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">uri</span><span class="p">)),</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">uri</span><span class="p">).</span><span class="na">length</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypelocalupload">ArchetypeLocalUpload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeLocalUpload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeLocalUpload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">file</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LocalFileConfig</span><span class="w"> </span><span class="n">localFileConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">LocalFileConfig</span><span class="p">)</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">fileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">extractFilename</span><span class="p">(</span><span class="n">file</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">absPath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getAbsoluteFile</span><span class="p">(</span><span class="n">localFileConfig</span><span class="p">.</span><span class="na">getUploadPath</span><span class="p">(),</span><span class="w"> </span><span class="n">fileName</span><span class="p">).</span><span class="na">getAbsolutePath</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">file</span><span class="p">.</span><span class="na">transferTo</span><span class="p">(</span><span class="n">Paths</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">absPath</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;%s/%s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">localFileConfig</span><span class="p">.</span><span class="na">getUploadPath</span><span class="p">(),</span><span class="w"> </span><span class="n">fileName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 编码文件名
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">extractFilename</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">file</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">CharSequenceUtil</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;{}/{}_{}.{}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">DateUtil</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(),</span><span class="w"> </span><span class="s">&#34;yyyyMMdd&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">FilenameUtils</span><span class="p">.</span><span class="na">getBaseName</span><span class="p">(</span><span class="n">file</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">()),</span><span class="w"> </span><span class="n">IdUtil</span><span class="p">.</span><span class="na">getSnowflakeNextIdStr</span><span class="p">(),</span><span class="w"> </span><span class="n">FilenameUtils</span><span class="p">.</span><span class="na">getExtension</span><span class="p">(</span><span class="n">file</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">getAbsoluteFile</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uploadDir</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">fileName</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">desc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">uploadDir</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">File</span><span class="p">.</span><span class="na">separator</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">fileName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">desc</span><span class="p">.</span><span class="na">exists</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="o">!</span><span class="n">desc</span><span class="p">.</span><span class="na">getParentFile</span><span class="p">().</span><span class="na">exists</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">desc</span><span class="p">.</span><span class="na">getParentFile</span><span class="p">().</span><span class="na">mkdirs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileUri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileUri</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="调用测试">调用测试</h2>
+<h3 id="filetest">FileTest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RunWith</span><span class="p">(</span><span class="n">SpringRunner</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@SpringBootTest</span><span class="p">(</span><span class="n">classes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">FileApplication</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FileTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">FileFacade</span><span class="w"> </span><span class="n">fileFacade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *     aliyun:
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFiles: [ &#34;.png&#34;,&#34;.txt&#34; ]
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFileSize: 10240
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       endpoint: oss-cn-shanghai.aliyuncs.com
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       accessKeyId: 
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       accessKeySecret: 
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       bucketName: shanghai-bucketnametest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AliyunFileConfig</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFiles</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="s">&#34;.png&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;.txt&#34;</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFileSize</span><span class="p">(</span><span class="n">10240L</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setEndpoint</span><span class="p">(</span><span class="s">&#34;oss-cn-shanghai.aliyuncs.com&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAccessKeyId</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAccessKeySecret</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setBucketName</span><span class="p">(</span><span class="s">&#34;shanghai-bucketnametest&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *     local:
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFiles: [&#34;.png&#34;,&#34;.txt&#34;]
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFileSize: 10240
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       uploadPath: &#34;C:/Users/Administrator/Downloads&#34;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       downloadPath: &#34;C:/Users/Administrator/Downloads&#34;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">localFileConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LocalFileConfig</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFiles</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="s">&#34;.png&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;.txt&#34;</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFileSize</span><span class="p">(</span><span class="n">10240L</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setUploadPath</span><span class="p">(</span><span class="s">&#34;C:\\Users\\Administrator\\Downloads&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setDownloadPath</span><span class="p">(</span><span class="s">&#34;C:\\Users\\Administrator\\Downloads&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *     fastdfs:
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFiles: [ &#34;.png&#34;,&#34;.txt&#34; ]
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFileSize: 10240
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       charset: UTF-8
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       connectTimeoutInSecond: 10
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       networkTimeoutInSeconds: 30
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       httpTrackerHttpPort: 8888
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       httpAntiStealToken: no
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       trackerServers: 172.16.1.199:22122
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       fastdfsUrl: http://172.16.1.199:8888
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       storageServiceIp: 172.16.1.199
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       storageServicePort: 23000
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       storageServicePathIndex: 0
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FastDfsConfig</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFiles</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="s">&#34;.png&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;.txt&#34;</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFileSize</span><span class="p">(</span><span class="n">10240L</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setCharset</span><span class="p">(</span><span class="s">&#34;UTF-8&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setConnectTimeoutInSecond</span><span class="p">(</span><span class="s">&#34;10&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setNetworkTimeoutInSeconds</span><span class="p">(</span><span class="s">&#34;30&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setHttpTrackerHttpPort</span><span class="p">(</span><span class="s">&#34;8888&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setHttpAntiStealToken</span><span class="p">(</span><span class="s">&#34;no&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setTrackerServers</span><span class="p">(</span><span class="s">&#34;172.16.1.199:22122&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setStorageServiceIp</span><span class="p">(</span><span class="s">&#34;172.16.1.199&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setStorageServicePort</span><span class="p">(</span><span class="n">23000</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setStorageServicePathIndex</span><span class="p">(</span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">uploadTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MockMultipartFile</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;file&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;hello11.txt&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">MediaType</span><span class="p">.</span><span class="na">TEXT_PLAIN_VALUE</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;Hello, World!111111111111111111111111111&#34;</span><span class="p">.</span><span class="na">getBytes</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">uriLs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fileFacade</span><span class="p">.</span><span class="na">upload</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">MultipartFile</span><span class="o">[]</span><span class="p">{</span><span class="n">file</span><span class="p">},</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=&gt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">uriLs</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">downloadTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">fileFacade</span><span class="p">.</span><span class="na">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C:\\Users\\Administrator\\Downloads\\20230114\\hello_1614199174685622272.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
+                    <div id="post_footer" class="post_footer">
+                        <div class="meta">
+                            
+                            <div id="post_footer_info" class="info">
+                                <span class="field tags">
+                                    <i class="ri-stack-line"></i>
+                                    
+                                        
+                                        <a href="http://localhost:1313/iblog/tags/%E5%BA%94%E7%94%A8/">应用</a>
+                                    
+                                        <a href="http://localhost:1313/iblog/tags/%E8%AE%BE%E8%AE%A1/">设计</a>
+                                    
+                                    
+                                </span>
+                            </div>
+                        </div>
+                    </div>
+                </div>
+                
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+        <svg t="1688628374733" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3166" width="16" height="16"><path d="M966.4 668.8l-435.2-432c-9.6-9.6-25.6-9.6-35.2 0l-441.6 432c-9.6 9.6-9.6 25.6 0 35.2 9.6 9.6 25.6 9.6 35.2 0l425.6-416 416 416c9.6 9.6 25.6 9.6 35.2 0S976 678.4 966.4 668.8z" p-id="3167" fill="#424242"></path></svg>
+    </a>
+</div>
+    <footer class="footer">
+    <div id="footer_powered_by" class="powered_by">
+        <a href="https://varkai.com">Designed by VarKai,</a>
+        <a href="http://www.gohugo.io/">Proudly published with Hugo</a>
+    </div>
+
+    <div id="footer_slogan" class="footer_slogan">
+        <span>from 2021</span>
+    </div>
+</footer>
+    <script src="http://localhost:1313/iblog/js/jquery-3.5.1.min.js"></script>
+<link href="http://localhost:1313/iblog/css/fancybox.min.css" rel="stylesheet">
+<script src="http://localhost:1313/iblog/js/fancybox.min.js"></script>
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+<script src="//cdn1.lncld.net/static/js/3.0.4/av-min.js"></script>
+<script src="http://localhost:1313/iblog/js/busuanzi_2.3_busuanzi.pure.mini.js"></script>
+<script src="http://localhost:1313/iblog/js/html2canvas.js"></script>
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+<script src="http://localhost:1313/iblog/js/html2md.js"></script>
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+
+
+<script>
+    new Darkmode({
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+</body>
+
+</html>
\ No newline at end of file
diff --git a/docs/index.html b/docs/index.html
index 092b8b57..af75099b 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -165,7 +165,7 @@ <h2><a href='/iblog/posts/spring/java-springboot/'>SpringBoot详解</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-generics/'>Java泛型</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-generics/'>Java泛型</a></h2>
     </div>
     
     <div class="list">
@@ -229,7 +229,7 @@ <h2><a href='/iblog/posts/essays/java-syntax-sugar/'>Java中常见的语法糖</
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/javakeyword/java-keyword-synchronized/'>synchronized关键字详解</a></h2>
+        <h2><a href='/iblog/posts/javakeyword/java-keyword-synchronized/'>synchronized关键字</a></h2>
     </div>
     
     <div class="list">
@@ -264,7 +264,7 @@ <h2><a href='/iblog/posts/javakeyword/java-keyword-synchronized/'>synchronized
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/javakeyword/java-keyword-volatile/'>volatile关键字详解</a></h2>
+        <h2><a href='/iblog/posts/javakeyword/java-keyword-volatile/'>volatile关键字</a></h2>
     </div>
     
     <div class="list">
@@ -299,7 +299,7 @@ <h2><a href='/iblog/posts/javakeyword/java-keyword-volatile/'>volatile关键字
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-arraylist/'>ArrayList详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-arraylist/'>ArrayList详解</a></h2>
     </div>
     
     <div class="list">
@@ -371,7 +371,7 @@ <h2><a href='/iblog/posts/keepupd/interview-junior-javaer/'>速览Java程序员
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/sql-select-fast/'>MySQL详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/sql-select-fast/'>MySQL详解</a></h2>
     </div>
     
     <div class="list">
@@ -404,7 +404,7 @@ <h2><a href='/iblog/posts/essays/sql-select-fast/'>MySQL详解</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-always-problems/'>Java程序常见问题</a></h2>
+        <h2><a href='/iblog/posts/codeguide/java-always-problems/'>Java程序常见问题</a></h2>
     </div>
     
     <div class="list">
@@ -505,7 +505,7 @@ <h2><a href='/iblog/posts/jvm/java-memory-divide/'>JVM详解</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/distributed-lock/'>分布式锁详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/distributed-lock/'>分布式锁详解</a></h2>
     </div>
     
     <div class="list">
diff --git a/docs/index.xml b/docs/index.xml
index a4b21ee4..dcbf8411 100644
--- a/docs/index.xml
+++ b/docs/index.xml
@@ -17,9 +17,9 @@
     </item>
     <item>
       <title>Java泛型</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-generics/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-generics/</link>
       <pubDate>Mon, 15 Jul 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-generics/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-generics/</guid>
       <description>概览 在Java中，泛型是一种强大的编程特性，允许类、接口和方法在定义时声明一种参数化类型，而在使用时可以指定具体的类型参数。泛型的主要目的是提高代码的重用性和类</description>
     </item>
     <item>
@@ -30,14 +30,14 @@
       <description>概览 语法糖是指编程语言中的一种语法结构，它们并不提供新的功能，而是为了让代码更易读、更易写而设计的。 语法糖使得某些常见的编程模式或操作变得更加简洁和直观，但在底</description>
     </item>
     <item>
-      <title>synchronized关键字详解</title>
+      <title>synchronized关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</guid>
       <description>synchronized synchronized是Java提供的关键字译为同步，是Java中用于实现线程同步的一种机制。它可以确保在同一时间只有一个线程能够执行某段代码，从而避免线程</description>
     </item>
     <item>
-      <title>volatile关键字详解</title>
+      <title>volatile关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</guid>
@@ -45,9 +45,9 @@
     </item>
     <item>
       <title>ArrayList详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</link>
       <pubDate>Wed, 26 Jun 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</guid>
       <description>ArrayList 在List接口实现类中，最常用的就是ArrayList，ArrayList类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删</description>
     </item>
     <item>
@@ -59,16 +59,16 @@
     </item>
     <item>
       <title>MySQL详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/sql-select-fast/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/sql-select-fast/</link>
       <pubDate>Thu, 30 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/sql-select-fast/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/sql-select-fast/</guid>
       <description>MySQL介绍 MySQL 是一种关系型数据库，主要用于持久化存储我们系统中的一些数据。 MySQL 如此流行的原因，主要具有下面这些优点： 成熟稳定，功能完善。 开源免费。 文档丰富，既有</description>
     </item>
     <item>
       <title>Java程序常见问题</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-always-problems/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-always-problems/</link>
       <pubDate>Tue, 28 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-always-problems/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-always-problems/</guid>
       <description>CPU使用过高 一般在生产环境排查程序故障，都会查看日志什么的，但是有些故障日志是看不出来的，就比如：CPU使用过高。 那应该怎么办呢？我们需要结合linux命令和</description>
     </item>
     <item>
@@ -87,9 +87,9 @@
     </item>
     <item>
       <title>分布式锁详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/distributed-lock/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/distributed-lock/</link>
       <pubDate>Sat, 25 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/distributed-lock/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/distributed-lock/</guid>
       <description>概述 在代码里面我们常用ReetrantLock、synchronized保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。 类似这样： public</description>
     </item>
     <item>
@@ -500,9 +500,9 @@
     </item>
     <item>
       <title>前端学习路线</title>
-      <link>https://whiteppure.github.io/iblog/posts/emp/front-learning-route/</link>
+      <link>https://whiteppure.github.io/iblog/posts/intro/front-learning-route/</link>
       <pubDate>Thu, 29 Feb 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/emp/front-learning-route/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/front-learning-route/</guid>
       <description>基础知识 网络知识 HTTP DNS 域名 云服务 网络安全 HTTPS CORS 网络渗透 OWASP HTML CSS JavaScript JQuery Ajax ES6-ES11 综合应用 工程化体系 代码规范 CSS预处理器 Less Sass PostCSS Node Promise Axios 工具 包管理工具 Yarn Npm 打包工具 Webpack Parcel 代码格式化工具</description>
     </item>
     <item>
@@ -541,17 +541,17 @@
       <description>Nacos安装启动 一键傻瓜试安装即可，官网写的很清楚这里不在赘述。 这里以Window环境安装为例。 启动Nacos将模式改为单机模式。 启动成功 Nacos相关配置 demo-dev.yaml</description>
     </item>
     <item>
-      <title>整合文件上传功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/uploadfile-code/</link>
+      <title>Java整合文件上传功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</link>
       <pubDate>Fri, 11 Aug 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/uploadfile-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</guid>
       <description>结构 pom.xml fastdfs-client-java-1.27.jar：点击下载 &amp;lt;dependencies&amp;gt; &amp;lt;!-- fastdfs --&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.csource&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;fastdfs-client-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;1.27&amp;lt;/version&amp;gt; &amp;lt;systemPath&amp;gt;${project.basedir}/lib/fastdfs-client-java-1.27.jar&amp;lt;/systemPath&amp;gt; &amp;lt;scope&amp;gt;system&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;!--aliyun oss 依赖--&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.aliyun.oss&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;aliyun-sdk-oss&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt;</description>
     </item>
     <item>
-      <title>整合支付功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/pay-code/</link>
+      <title>Java整合支付功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pay-code/</link>
       <pubDate>Thu, 10 Aug 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/pay-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pay-code/</guid>
       <description>结构 完整代码：https://gitee.com/gitee_pikaqiu/easy-archetype pom.xml &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.alipay.sdk&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;alipay-sdk-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;4.9.9&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt;</description>
     </item>
     <item>
@@ -562,17 +562,17 @@
       <description>常见参数校验 在日常的接口开发中，为了防止非法参数对业务造成影响，经常需要对接口的参数做校验。最简单就是用if条件语句来判断，但是随着参数越来越多，业务越来越复杂</description>
     </item>
     <item>
-      <title>管道流设计模式结合业务</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/pipeline-business/</link>
+      <title>Java管道流设计模式结合业务</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</link>
       <pubDate>Thu, 15 Jun 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/pipeline-business/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</guid>
       <description>流程图 代码实现 完整代码：https://gitee.com/gitee_pikaqiu/easy-pipeline pom &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.plugin&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-plugin-core&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;${spring.plugin.core.version}&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt;</description>
     </item>
     <item>
       <title>重构一个程序</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-project-reconstitution/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-project-reconstitution/</link>
       <pubDate>Thu, 20 Apr 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-project-reconstitution/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-project-reconstitution/</guid>
       <description>什么是重构 摘自《重构：改善既有代码的设计》 重构(名词形式): 对软件内部结构的一种调整，目的是在不改变软件可观察行为的前提下，提高其可理解性，降低其修改成本。 重构</description>
     </item>
     <item>
@@ -583,24 +583,24 @@
       <description>SpringMVC SpringWebMVC是建立在Servlet API上的原始Web框架，从一开始就包含在Spring框架中。正式名称 &amp;ldquo;Spring Web MVC &amp;ldquo;来自其源模块的名称（s</description>
     </item>
     <item>
-      <title>分布式ID</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/distributed-id/</link>
+      <title>分布式ID详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/distributed-id/</link>
       <pubDate>Mon, 13 Mar 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/distributed-id/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/distributed-id/</guid>
       <description>分布式ID 在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。 但随着数据日渐增长，主从同步也扛不住了，</description>
     </item>
     <item>
       <title>如何减少及解决bug</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-bugs/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-bugs/</link>
       <pubDate>Fri, 10 Mar 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-bugs/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-bugs/</guid>
       <description>bug的起源: 1945年，一只小飞蛾钻进了计算机电路里，导致系统无法工作，一位名叫格蕾丝·赫柏的人把飞蛾拍死在工作日志上，写道：就是这个 bug(虫子)，害我们今</description>
     </item>
     <item>
       <title>Elasticsearch详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/elasticsearch/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/elasticsearch/</link>
       <pubDate>Tue, 14 Feb 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/elasticsearch/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/elasticsearch/</guid>
       <description>概览 Elasticsearch，简称为 ES， ES是一个开源的高扩展的分布式全文搜索引擎， 是整个 ElasticStack 技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可</description>
     </item>
     <item>
@@ -619,16 +619,16 @@
     </item>
     <item>
       <title>整洁的代码</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/clean-code/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/clean-code/</link>
       <pubDate>Thu, 01 Sep 2022 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/clean-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/clean-code/</guid>
       <description>为什么要写整洁的代码 为什么要写整洁的代码,回答这个问题之前,也许应该想想写糟糕的代码的原因 是想快点完成吗?还是要赶时间吗?有可能.或许你觉得自己要干好所需要的时</description>
     </item>
     <item>
       <title>如何做好程序设计功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-design/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-design/</link>
       <pubDate>Tue, 02 Aug 2022 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-design/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-design/</guid>
       <description>功能设计流程图 与外部系统交互、本系统模块之间流程，比较好用的画圈软件draw .io或在线的process on 数据库设计 从DDD角度界限上下文、ER图、评审表结构设</description>
     </item>
     <item>
@@ -646,17 +646,17 @@
       <description>写在前面 本文中所涉及的程序均为Java开发，如果您想要直接使用这些工具需要提前配置Java环境。所涉及到的程序均提供完整代码，如果您有兴趣可以尝试运行。 使用ja</description>
     </item>
     <item>
-      <title>数据结构与算法</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/data-structures-algorithms/</link>
+      <title>数据结构与算法详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/data-structures-algorithms/</link>
       <pubDate>Fri, 10 Dec 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/data-structures-algorithms/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/data-structures-algorithms/</guid>
       <description>数据结构 数据结构是一门研究组织数据方式的学科，有了编程语言也就有了数据结构，学好数据结构可以编写出更有效率的代码。数据结构是算法的基础，想要学好算法，就必须把数</description>
     </item>
     <item>
       <title>规范编写Java代码总结</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-code-rule/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-code-rule/</link>
       <pubDate>Thu, 25 Nov 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-code-rule/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-code-rule/</guid>
       <description>编码规范 我们为什么要遵守规范来编码？ 是因为通常在编码过程中我们不只自己进行开发，通常需要一个团队来进行，开发好之后还需要维护，所以编码规范就显的尤为重要。 代码维</description>
     </item>
     <item>
@@ -667,59 +667,59 @@
       <description>网络协议 以下内容摘自百度百科： https://baike.baidu.com/item/网络协议/328636 https://baike.baidu.com/i</description>
     </item>
     <item>
-      <title>MQ详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-mq/</link>
+      <title>Kafka详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-mq/</link>
       <pubDate>Tue, 19 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-mq/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-mq/</guid>
       <description>概览 MQ 即 messagequeue 消息队列，是分布式系统的重要组件，主要解决异步消息，应用解耦，消峰等问题。从而实现高可用，高性能，可伸缩和最终一致性的架构。使用较多的MQ有：acti</description>
     </item>
     <item>
       <title>Java集合</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-java-container/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-java-container/</link>
       <pubDate>Mon, 04 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-java-container/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-java-container/</guid>
       <description>概述 Java中的集合主要包括Collection和Map两种，Collection存储着对象的集合，而Map存储着键值对的映射表。 数组 如果你看过ArrayLis</description>
     </item>
     <item>
       <title>Java反射</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-reflect/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-reflect/</link>
       <pubDate>Sat, 02 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-reflect/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-reflect/</guid>
       <description>概述 在Java程序运行状态中，对于任意一个实体类，都能够知道这个类的所有属性和方法，对于任意一个对象，都能够调用它的任意方法和属性。这种动态获取信息以及动态调用</description>
     </item>
     <item>
       <title>Java程序常见故障排查命令及工具</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/eye-beam/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/eye-beam/</link>
       <pubDate>Wed, 08 Sep 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/eye-beam/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/eye-beam/</guid>
       <description>故障排查命令 收录Linux常用命令，以下命令来自https://www.bilibili.com/video/BV14A411378a 关机/重启/注销 常用命令 作</description>
     </item>
     <item>
       <title>分布式事务详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-transaction/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-transaction/</link>
       <pubDate>Mon, 02 Aug 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-transaction/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-transaction/</guid>
       <description>基础概念 什么是事务 什么是事务？举个例子：你去超市买东西，&amp;ldquo;一手交钱，一手交货&amp;quot;就是一个事务的例子。 交钱和交货必须同时成功，事务才算成功，其</description>
     </item>
     <item>
       <title>JavaObject类方法</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-objectclass-methods/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-objectclass-methods/</link>
       <pubDate>Sat, 10 Jul 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-objectclass-methods/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-objectclass-methods/</guid>
       <description>概览 Object类位于java.lang包中，编译时会自动导入。当我们创建一个类时，如果没有明确继承一个父类，那么它就会自动继承Object，成为Object的</description>
     </item>
     <item>
       <title>微服务治理详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-small-service/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-small-service/</link>
       <pubDate>Mon, 21 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-small-service/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-small-service/</guid>
       <description>什么是微服务架构 In short， the microservice architectural style is an approach to developing a single application as a suite of small services， each running in its own process and communicating with lightweight mechanisms， often an HTTP resource API。 These services are built around business capabilities and independently deployable</description>
     </item>
     <item>
       <title>Redis详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-redis/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-redis/</link>
       <pubDate>Thu, 17 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-redis/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-redis/</guid>
       <description>Redis概述 参考文章： https://www.runoob.com/redis/redis-intro.html https://www.redis.com.cn/redis-interview-questions.html 什么是Redis Redis(Remote Dictionary Server) Redis 是一个开源的使用 ANSI C 语言编写、遵守 BSD 协议、支持网络、可基于内存亦可持久化的日志型、Key-Value 数据库，</description>
     </item>
     <item>
@@ -738,16 +738,16 @@
     </item>
     <item>
       <title>Java多线程</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-multi-thread/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-multi-thread/</link>
       <pubDate>Wed, 05 May 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-multi-thread/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-multi-thread/</guid>
       <description>线程与进程 进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。 线程是操作系统能够进行运算调度的最小单位。它被包</description>
     </item>
     <item>
       <title>HashMap详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</link>
       <pubDate>Mon, 03 May 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</guid>
       <description>HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问</description>
     </item>
     <item>
@@ -801,16 +801,16 @@
     </item>
     <item>
       <title>JavaIO</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-io/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-io/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-io/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-io/</guid>
       <description>概览 IO，即in和out的缩写，也就是输入和输出，指应用程序和外部设备之间的数据传递，常见的外部设备包括文件、管道、网络连接。 从计算机结构的角度来看IO，IO就</description>
     </item>
     <item>
       <title>Netty详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-netty/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-netty/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-netty/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-netty/</guid>
       <description>Netty 参考文章：https://dongzl.github.io/netty-handbook/#/ 概述 Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers &amp;amp; clients. Netty 是一个异步的、基于事</description>
     </item>
     <item>
@@ -863,10 +863,10 @@
       <description>为什么要学习JVM 大部分Java开发人员，除了会在项目中使用到与Java平台相关的各种高精尖技术，对于Java技术的核心Java虚拟机了解甚少。 一些有一定工作经</description>
     </item>
     <item>
-      <title>Nginx介绍</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/nginx-start/</link>
+      <title>Nginx入门</title>
+      <link>https://whiteppure.github.io/iblog/posts/intro/nginx-start/</link>
       <pubDate>Thu, 04 Mar 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/nginx-start/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/nginx-start/</guid>
       <description>Nginx介绍 Nginx (&amp;ldquo;engine x&amp;rdquo;)是一个高性能的HTTP和反向代理服务器，特点是占有内存少，并发能力强，事实上Nginx的并发能力确实在同类型的网页服务器中表</description>
     </item>
     <item>
@@ -878,9 +878,9 @@
     </item>
     <item>
       <title>Java面向对象</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-object-oriented/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-object-oriented/</link>
       <pubDate>Mon, 15 Feb 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-object-oriented/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-object-oriented/</guid>
       <description>概览 面向对象简称OO(object-oriented)是相对面向过程(procedure-oriented)来说的，是一种编程思想，Java就是一门面向对象的语</description>
     </item>
     <item>
@@ -892,23 +892,23 @@
     </item>
     <item>
       <title>Java运算</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-operation/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-operation/</link>
       <pubDate>Sat, 30 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-operation/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-operation/</guid>
       <description>运算符与表达式 运算符 运算符指明对操作数的运算方式。组成表达式的Java操作符有很多种。 运算符按照其要求的操作数数目来分，可以有单目运算符、双目运算符和三目运算符</description>
     </item>
     <item>
       <title>Java数据类型</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-datatype/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-datatype/</link>
       <pubDate>Wed, 20 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-datatype/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-datatype/</guid>
       <description>基本类型 Java语言提供了八种基本类型。六种数值类型（四个整数型，两个浮点型），一种字符类型，还有一种布尔型，俗称4类8种。 这里只介绍称4类8种，实际上，Jav</description>
     </item>
     <item>
       <title>Java异常</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-exception/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-exception/</link>
       <pubDate>Wed, 13 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-exception/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-exception/</guid>
       <description>异常类型 Throwable可以用来表示任何可以作为异常抛出的类，分为两种：Error 和 Exception。 其中Error用来表示Java程序无法处理的错误，这类</description>
     </item>
     <item>
@@ -941,9 +941,9 @@
     </item>
     <item>
       <title>Docker入门</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/docker-start/</link>
+      <link>https://whiteppure.github.io/iblog/posts/intro/docker-start/</link>
       <pubDate>Tue, 07 Apr 2020 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/docker-start/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/docker-start/</guid>
       <description>概述 Docker属于Linux容器的一种封装，提供简单易用的容器使用接口。它是目前流行的Linux容器解决方案。Docker将应用程序与该程序的依赖，打包在一个</description>
     </item>
     <item>
@@ -962,9 +962,9 @@
     </item>
     <item>
       <title>CAS详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/cas-detail/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/cas-detail/</link>
       <pubDate>Sat, 04 Apr 2020 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/cas-detail/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/cas-detail/</guid>
       <description>CAS CAS全称为Compare and Swap被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更</description>
     </item>
     <item>
@@ -1060,30 +1060,30 @@
     </item>
     <item>
       <title></title>
-      <link>https://whiteppure.github.io/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>https://whiteppure.github.io/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>https://whiteppure.github.io/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>https://whiteppure.github.io/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
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     <item>
diff --git a/docs/page/10/index.html b/docs/page/10/index.html
index 1c2bdab0..bc56a4d7 100644
--- a/docs/page/10/index.html
+++ b/docs/page/10/index.html
@@ -130,7 +130,7 @@ <h1>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/cas-detail/'>CAS详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/cas-detail/'>CAS详解</a></h2>
     </div>
     
     <div class="list">
@@ -592,7 +592,7 @@ <h2><a href='/iblog/posts/toy/js-birthday-gift/'>Js生日礼物</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/'></a></h2>
+        <h2><a href='/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/'></a></h2>
     </div>
     
     <div class="list">
diff --git a/docs/page/11/index.html b/docs/page/11/index.html
index 31712f1f..f0047251 100644
--- a/docs/page/11/index.html
+++ b/docs/page/11/index.html
@@ -130,7 +130,7 @@ <h1>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/'></a></h2>
+        <h2><a href='/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/'></a></h2>
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@@ -154,7 +154,7 @@ <h2><a href='/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/'></a></h2>
+        <h2><a href='/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97/'></a></h2>
     </div>
     
     <div class="list">
@@ -178,7 +178,7 @@ <h2><a href='/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/'></a></h2>
+        <h2><a href='/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97/'></a></h2>
     </div>
     
     <div class="list">
diff --git a/docs/page/5/index.html b/docs/page/5/index.html
index 53b8aed9..13f5b58c 100644
--- a/docs/page/5/index.html
+++ b/docs/page/5/index.html
@@ -450,7 +450,7 @@ <h2><a href='/iblog/posts/essays/force-copy-website-text/'>如何强制复制网
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/emp/front-learning-route/'>前端学习路线</a></h2>
+        <h2><a href='/iblog/posts/intro/front-learning-route/'>前端学习路线</a></h2>
     </div>
     
     <div class="list">
diff --git a/docs/page/6/index.html b/docs/page/6/index.html
index 756f7eca..c60e90ad 100644
--- a/docs/page/6/index.html
+++ b/docs/page/6/index.html
@@ -165,7 +165,7 @@ <h2><a href='/iblog/posts/spring/springboot-nacos/'>SpringBoot整合Nacos</a></h
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/uploadfile-code/'>整合文件上传功能</a></h2>
+        <h2><a href='/iblog/posts/toy/uploadfile-code/'>Java整合文件上传功能</a></h2>
     </div>
     
     <div class="list">
@@ -189,6 +189,10 @@ <h2><a href='/iblog/posts/essays/uploadfile-code/'>整合文件上传功能</a><
                     
                     <a href="https://whiteppure.github.io/iblog/tags/%E8%AE%BE%E8%AE%A1/">设计</a>
                     
+                    <a href="https://whiteppure.github.io/iblog/tags/java/">Java</a>
+                    
+                    <a href="https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/">玩具</a>
+                    
                 </span>
                 
             </div>
@@ -198,7 +202,7 @@ <h2><a href='/iblog/posts/essays/uploadfile-code/'>整合文件上传功能</a><
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/pay-code/'>整合支付功能</a></h2>
+        <h2><a href='/iblog/posts/toy/pay-code/'>Java整合支付功能</a></h2>
     </div>
     
     <div class="list">
@@ -222,6 +226,10 @@ <h2><a href='/iblog/posts/essays/pay-code/'>整合支付功能</a></h2>
                     
                     <a href="https://whiteppure.github.io/iblog/tags/%E8%AE%BE%E8%AE%A1/">设计</a>
                     
+                    <a href="https://whiteppure.github.io/iblog/tags/java/">Java</a>
+                    
+                    <a href="https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/">玩具</a>
+                    
                 </span>
                 
             </div>
@@ -264,7 +272,7 @@ <h2><a href='/iblog/posts/spring/springboot-validator/'>SpringBoot整合Validato
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/pipeline-business/'>管道流设计模式结合业务</a></h2>
+        <h2><a href='/iblog/posts/toy/pipeline-business/'>Java管道流设计模式结合业务</a></h2>
     </div>
     
     <div class="list">
@@ -288,6 +296,10 @@ <h2><a href='/iblog/posts/essays/pipeline-business/'>管道流设计模式结合
                     
                     <a href="https://whiteppure.github.io/iblog/tags/%E8%AE%BE%E8%AE%A1/">设计</a>
                     
+                    <a href="https://whiteppure.github.io/iblog/tags/java/">Java</a>
+                    
+                    <a href="https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/">玩具</a>
+                    
                 </span>
                 
             </div>
@@ -297,7 +309,7 @@ <h2><a href='/iblog/posts/essays/pipeline-business/'>管道流设计模式结合
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-project-reconstitution/'>重构一个程序</a></h2>
+        <h2><a href='/iblog/posts/codeguide/java-project-reconstitution/'>重构一个程序</a></h2>
     </div>
     
     <div class="list">
@@ -361,7 +373,7 @@ <h2><a href='/iblog/posts/spring/java-spring-mvc-webflux/'>SpringMVC与SpringWeb
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/distributed-id/'>分布式ID</a></h2>
+        <h2><a href='/iblog/posts/detailed/distributed-id/'>分布式ID详解</a></h2>
     </div>
     
     <div class="list">
@@ -383,6 +395,8 @@ <h2><a href='/iblog/posts/essays/distributed-id/'>分布式ID</a></h2>
                     
                     <a href="https://whiteppure.github.io/iblog/tags/%E5%88%86%E5%B8%83%E5%BC%8F/">分布式</a>
                     
+                    <a href="https://whiteppure.github.io/iblog/tags/%E8%AF%A6%E8%A7%A3/">详解</a>
+                    
                 </span>
                 
             </div>
@@ -392,7 +406,7 @@ <h2><a href='/iblog/posts/essays/distributed-id/'>分布式ID</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-bugs/'>如何减少及解决bug</a></h2>
+        <h2><a href='/iblog/posts/codeguide/java-bugs/'>如何减少及解决bug</a></h2>
     </div>
     
     <div class="list">
@@ -423,7 +437,7 @@ <h2><a href='/iblog/posts/essays/java-bugs/'>如何减少及解决bug</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/elasticsearch/'>Elasticsearch详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/elasticsearch/'>Elasticsearch详解</a></h2>
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@@ -520,7 +534,7 @@ <h2><a href='/iblog/posts/essays/dev-idea/'>IDEA常用配置及使用技巧</a><
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/clean-code/'>整洁的代码</a></h2>
+        <h2><a href='/iblog/posts/codeguide/clean-code/'>整洁的代码</a></h2>
     </div>
     
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@@ -551,7 +565,7 @@ <h2><a href='/iblog/posts/essays/clean-code/'>整洁的代码</a></h2>
 
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     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-design/'>如何做好程序设计功能</a></h2>
+        <h2><a href='/iblog/posts/codeguide/java-design/'>如何做好程序设计功能</a></h2>
     </div>
     
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diff --git a/docs/page/7/index.html b/docs/page/7/index.html
index ddcac1ff..2e34897a 100644
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+++ b/docs/page/7/index.html
@@ -163,7 +163,7 @@ <h2><a href='/iblog/posts/toy/java-multi-gadget/'>Java小程序集合</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/data-structures-algorithms/'>数据结构与算法</a></h2>
+        <h2><a href='/iblog/posts/detailed/data-structures-algorithms/'>数据结构与算法详解</a></h2>
     </div>
     
     <div class="list">
@@ -185,7 +185,7 @@ <h2><a href='/iblog/posts/essays/data-structures-algorithms/'>数据结构与算
                     
                     <a href="https://whiteppure.github.io/iblog/tags/java/">Java</a>
                     
-                    <a href="https://whiteppure.github.io/iblog/tags/%E7%AE%97%E6%B3%95/">算法</a>
+                    <a href="https://whiteppure.github.io/iblog/tags/%E8%AF%A6%E8%A7%A3/">详解</a>
                     
                 </span>
                 
@@ -196,7 +196,7 @@ <h2><a href='/iblog/posts/essays/data-structures-algorithms/'>数据结构与算
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-code-rule/'>规范编写Java代码总结</a></h2>
+        <h2><a href='/iblog/posts/codeguide/java-code-rule/'>规范编写Java代码总结</a></h2>
     </div>
     
     <div class="list">
@@ -260,7 +260,7 @@ <h2><a href='/iblog/posts/essays/net-program-java/'>网络编程</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-mq/'>MQ详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-mq/'>Kafka详解</a></h2>
     </div>
     
     <div class="list">
@@ -293,7 +293,7 @@ <h2><a href='/iblog/posts/essays/java-mq/'>MQ详解</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-java-container/'>Java集合</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-java-container/'>Java集合</a></h2>
     </div>
     
     <div class="list">
@@ -326,7 +326,7 @@ <h2><a href='/iblog/posts/java/rookie-java-container/'>Java集合</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-reflect/'>Java反射</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-reflect/'>Java反射</a></h2>
     </div>
     
     <div class="list">
@@ -359,7 +359,7 @@ <h2><a href='/iblog/posts/java/rookie-reflect/'>Java反射</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/eye-beam/'>Java程序常见故障排查命令及工具</a></h2>
+        <h2><a href='/iblog/posts/codeguide/eye-beam/'>Java程序常见故障排查命令及工具</a></h2>
     </div>
     
     <div class="list">
@@ -392,7 +392,7 @@ <h2><a href='/iblog/posts/essays/eye-beam/'>Java程序常见故障排查命令
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-transaction/'>分布式事务详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-transaction/'>分布式事务详解</a></h2>
     </div>
     
     <div class="list">
@@ -425,7 +425,7 @@ <h2><a href='/iblog/posts/essays/java-transaction/'>分布式事务详解</a></h
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-objectclass-methods/'>JavaObject类方法</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-objectclass-methods/'>JavaObject类方法</a></h2>
     </div>
     
     <div class="list">
@@ -458,7 +458,7 @@ <h2><a href='/iblog/posts/java/rookie-objectclass-methods/'>JavaObject类方法<
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-small-service/'>微服务治理详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-small-service/'>微服务治理详解</a></h2>
     </div>
     
     <div class="list">
@@ -491,7 +491,7 @@ <h2><a href='/iblog/posts/essays/java-small-service/'>微服务治理详解</a><
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-redis/'>Redis详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-redis/'>Redis详解</a></h2>
     </div>
     
     <div class="list">
@@ -592,7 +592,7 @@ <h2><a href='/iblog/posts/jvm/java-garbage-collector/'>JVM中的垃圾回收器<
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-multi-thread/'>Java多线程</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-multi-thread/'>Java多线程</a></h2>
     </div>
     
     <div class="list">
diff --git a/docs/page/8/index.html b/docs/page/8/index.html
index 69cce0d6..f55239a6 100644
--- a/docs/page/8/index.html
+++ b/docs/page/8/index.html
@@ -130,7 +130,7 @@ <h1>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-hashmap/'>HashMap详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-hashmap/'>HashMap详解</a></h2>
     </div>
     
     <div class="list">
@@ -394,7 +394,7 @@ <h2><a href='/iblog/posts/jvm/java-object/'>从JVM角度理解Java对象</a></h2
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-io/'>JavaIO</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-io/'>JavaIO</a></h2>
     </div>
     
     <div class="list">
@@ -427,7 +427,7 @@ <h2><a href='/iblog/posts/java/rookie-io/'>JavaIO</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/java-netty/'>Netty详解</a></h2>
+        <h2><a href='/iblog/posts/detailed/java-netty/'>Netty详解</a></h2>
     </div>
     
     <div class="list">
diff --git a/docs/page/9/index.html b/docs/page/9/index.html
index 85200727..f5c3ac4b 100644
--- a/docs/page/9/index.html
+++ b/docs/page/9/index.html
@@ -198,7 +198,7 @@ <h2><a href='/iblog/posts/jvm/jvm-start/'>JVM介绍</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/nginx-start/'>Nginx介绍</a></h2>
+        <h2><a href='/iblog/posts/intro/nginx-start/'>Nginx入门</a></h2>
     </div>
     
     <div class="list">
@@ -231,7 +231,7 @@ <h2><a href='/iblog/posts/essays/nginx-start/'>Nginx介绍</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-object-oriented/'>Java面向对象</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-object-oriented/'>Java面向对象</a></h2>
     </div>
     
     <div class="list">
@@ -297,7 +297,7 @@ <h2><a href='/iblog/posts/jvm/jvm-classloader/'>Java类加载机制</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-operation/'>Java运算</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-operation/'>Java运算</a></h2>
     </div>
     
     <div class="list">
@@ -330,7 +330,7 @@ <h2><a href='/iblog/posts/java/rookie-operation/'>Java运算</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-datatype/'>Java数据类型</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-datatype/'>Java数据类型</a></h2>
     </div>
     
     <div class="list">
@@ -363,7 +363,7 @@ <h2><a href='/iblog/posts/java/rookie-datatype/'>Java数据类型</a></h2>
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/java/rookie-exception/'>Java异常</a></h2>
+        <h2><a href='/iblog/posts/javabasics/rookie-exception/'>Java异常</a></h2>
     </div>
     
     <div class="list">
@@ -530,7 +530,7 @@ <h2><a href='/iblog/posts/essays/thread-created-way/'>线程创建方式</a></h2
 
 <div class="post animated fadeInDown">
     <div class="post_title">
-        <h2><a href='/iblog/posts/essays/docker-start/'>Docker入门</a></h2>
+        <h2><a href='/iblog/posts/intro/docker-start/'>Docker入门</a></h2>
     </div>
     
     <div class="list">
diff --git a/docs/posts/codeguide/clean-code/index.html b/docs/posts/codeguide/clean-code/index.html
new file mode 100644
index 00000000..d2ace8a0
--- /dev/null
+++ b/docs/posts/codeguide/clean-code/index.html
@@ -0,0 +1,696 @@
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+<html lang="zh" >
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+    <meta name="description" content="为什么要写整洁的代码 为什么要写整洁的代码,回答这个问题之前,也许应该想想写糟糕的代码的原因 是想快点完成吗?还是要赶时间吗?有可能.或许你觉得自己要干好所需要的时" />
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+                        <h2 id="post_single_title">整洁的代码</h2>
+                        <span id="post_page_title_date" class="date">2022.09.01</span>
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+                    <div class="post_content markdown"><h2 id="为什么要写整洁的代码">为什么要写整洁的代码</h2>
+<p>为什么要写整洁的代码,回答这个问题之前,也许应该想想写糟糕的代码的原因</p>
+<p>是想快点完成吗?还是要赶时间吗?有可能.或许你觉得自己要干好所需要的时间不够;假使花时间清理代码,老板就会大发雷霆.或许你只是不耐烦再搞这套程序,期望早点结束.或许你看了看,自己承诺要做的其他事情,意识到得赶紧弄完手上的东西,好接着做下一件工作.这种事情我们都干过.</p>
+<p>&ldquo;只要你干过编程,就有可能曾经被某人的糟糕代码绊倒过.如果你编程不止两三年,有可能被这种代码拖过腿.进度延缓的程度非常严重.有些团队在项目初期进展迅速,但是有那么一两年的时间却慢如蜗行.如对代码的每次修改都影响到了其他两三处代码.修改无小事.每次修改或添加代码都对那对扭纹柴了然于心,这样才能网上扔更多的扭纹柴.这团乱麻越来越大,在也无法清理,最后束手无策.</p>
+<p>随着混乱的增加,团队生产力也持续下降,趋势余零.当生产力下降时,管理层就只有一件事情可做了:增加更多的人手到项目中,期望提高生产力.可新人不熟悉系统的设计.他们搞不清什么样的修改符合设计的意图,什么样的修改违背设计意图.而且,他们以及团队中的其他人都背负着提高生产力的压力.于是,他们制造了更多的混乱,驱动生产力向零的那端不断下降.</p>
+<p>最后,开发团队造反了,他们告诉管理层,再也无法在这令人生厌的代码基础上做开发.他们要求全新设计.管理层不愿意投入资源完全重启炉灶,他们也不能否认生产力低得可怕.他们只好同意开发者的要求,授权去做一套看上去很美的华丽新设计.</p>
+<p>于是就组建了一只新军.谁都想加入这个团队,因为它是张白纸.他们可以重新来过,搞出点真正漂亮的东西来.但只有最优秀,最聪明的家伙被选中.其余人则继续维护现有的系统.</p>
+<p>现在有两支队伍在竞赛.新团队必须搭建一套新系统,要求实现旧系统的所有功能.另外,还得跟得上旧系统的持续改动.在新系统功能足以对抗旧系统之前,管理层就不会替换掉旧的系统.</p>
+<p>竞赛可能会持续极长的时间.到了完成的时候,新团队的老成员已不知去向,而现有成员则需求重新设计一套新系统,因为这套系统太烂了.</p>
+<p>假如你经历过哪怕是一小段我谈到的这种事,那么你一定知道,花时间保持整洁的代码不但有关于效率,还有关于生存. &quot;</p>
+<p>有时我们抱怨需求变化背离了初期设计.哀叹进度太紧张,没法好好干活.我们把问题归咎于那些愚蠢的经理,苛刻的用户,没用的营销方式.</p>
+<p>经理和营销人员指望从我们这里得到必须的信息，然后才能做出承诺和保证；即便他们没开口问，我们也不该羞于告知自己的想法。用户指望我们验证需求是否都在系统中实现了。项目经理指望我们遵守进度。我们与项目的规划脱不了干系，对失败负有极大的责任：特别是当失败与糟糕的代码有关时尤为如此！
+“且慢！”你说。“不听经理的，我就会被炒鱿鱼。”多半不会。多数经理想要知道实情，即便他们看起来不喜欢实情。多数经理想要好代码，即便他们总是痴缠于进度。他们会奋力卫护进度和需求；那是他们该干的。你则当以同等的热情卫护代码。</p>
+<p>再说明白些，假使你是位医生，病人请求你在给他做手术前别洗手，因为那会花太多时间，你会照办吗？本该是病人说了算；但医生却绝对应该拒绝遵从。为什么？因为医生比病人更了解疾病和感染的风险。医生如果按病人说的办，就是一种不专业的态度,更别说是犯罪了。同理，程序员遵从不了解混乱风险的经理的意愿，也是不专业的做法。我们应该加强这方面的意识。</p>
+<p>程序员面临着一种基础价值谜题。有那么几年经验的开发者都知道，之前的混乱拖了自己的后腿。但开发者们背负期限的压力，只好制造混乱。简言之，他们没花时间让自己做得更快！真正的专业人士明白，这道谜题的第二部分说错了。制造混乱无助于赶上期限。混乱只会立刻拖慢你，叫你错过期限。赶上期限的唯一方法一做得快的唯一方法就是始终尽可能保持代码整洁。</p>
+<p>&ldquo;如果你不明白整洁对于代码有何意义,尝试去写整洁代码就会毫无所益.&rdquo;</p>
+<p><strong>截取自《代码整洁之道》</strong></p>
+<h2 id="什么是整洁的代码">什么是整洁的代码</h2>
+<p>每个人对于整洁的代码理解肯定不同,在我看来,满足业务场景的情况下,可读性强,运行效率高,细节处理好,易扩展的代码就是整洁代码. 抛开业务场景不谈,只谈所谓的&quot;整洁代码&quot;就是所谓的耍流氓。</p>
+<p>整洁的代码总是看起来总是像是某位特别在意它的人写的.几乎没有改进的余地.代码的作者什么都想到了.如果你想改进它,总会回到原点。</p>
+<p>代码的作用是为了解决人们的某种需求,什么语言不重要(但是总有人非要争个高低),问题解决了才重要.在规定的业务场景下,写出能解决用户需求的代码就是程序员的日常工作,而需求并不是一成不变的,需求会变代码也会改变,所以我们就需要再这个特定的业务场景中尽量把代码变得灵活起来,之后增加需求或者修改需求时,会变的容易一些。</p>
+<p>至于方法的规范命名,可读性,注释等.这些也很重要,毕竟开发的时候一般都是团队一起来开发,代码不止你自己看,还需要别人看,说简单一些就是别人好接手你的代码,即代码的维护</p>
+<h3 id="可读性">可读性</h3>
+<p>在一个产品的周期中,开发其实只占了一小段时间,绝大多数时间都在维护代码.代码写出来首先是给人看的,其次是给电脑看,所以代码的可读性至关重要.所以,如果我非要在代码的可读性和运行效率之间选择一个,非可读性莫属.一般来说,要权衡代码的可读性和运行效率,如果差距太大,要看实际的业务场景来决定,毕竟写程序的最终目的是为了解决用户的某些问题.</p>
+<p>可读性通常表现在代码易于理解</p>
+<ul>
+<li>容易理解整个应用程序的执行流程</li>
+<li>容易理解不同对象之间的协作方式</li>
+<li>容易理解每个类的作用和责任</li>
+<li>容易理解每个方法的作用</li>
+<li>容易理解每个表达式和变量的目的是什么</li>
+</ul>
+<p>如果一个方法的行数过多也会影响代码的可读性,一般控制在80行左右。过多无用的注释、API,只会加重使用者的认知负担,过多无用的信息读起来只会浪费时间，所以要尽量保持API的精简，代码注释的合理，保持规范的命名，使注释看起来没那么臃肿。要知道代码有人维护，可注释没有人维护。</p>
+<p>代码依赖性导致了变化的放大和高认知负荷。模糊性造成了未知的不可知性，导致了认知负荷。从而使得代码更加难以理解,从而不能很好的维护. 所以整洁的代码总是复杂性低的。</p>
+<h3 id="运行效率">运行效率</h3>
+<p>运行效率即代码的运行效率，包括运行所占用的时间和空间。如果数据量不是很大（单表在300w左右）可能几乎不用考虑这个问题，空间就更不用说了，现在大多数公司都是用空间来换时间的，即通过增加服务器的配置或数量来提高程序运算速度。所以很多人并不关心程序运行的效率。</p>
+<p>诚然，我也不是很关心软件的运行效率，因为软件的运行效率主要还是取决与硬件的发展水平，现在硬件发展比软件发展快了一个档次，不然现在也不能一下子涌起那么多的软件公司。</p>
+<p>但是，如果业务量非常大，电脑的运行效率也是有限的，当服务器达到一定数量后，企业就会考虑成本毕竟不能一直毫无节制的增加下去，这时候就需要考虑程序的运行效率了。</p>
+<p>作为一个好的程序员，你不得不具备这项技能。</p>
+<p>怎样提高程序的运行效率，有没有想过？程序是算法和数据结构组成的，数据结构决定一个程序的空间复杂度，算法则决定一个程序的时间复杂度。 想要程序跑的更快，空间占用更少，可以从这两个维度来进行探索。</p>
+<p>一个好的算法离不开一个好的想法，这对于一个程序来说是至关重要的，因为它是决定了程序运行速度的关键原因。可能很多人都有一个误区，就是代码越少执行效率就越高，在改进算法的时候会通过删减代码来进行。举个例子：匹配字符串，在数据量很大的情况下，暴力匹配的方式无论你怎么改，都会比那些运用了好的算法的程序慢。</p>
+<p>不整洁的代码是混乱的，代码混乱到一定程度就会对程序的运行速度产生影响。所以，代码的整洁程度一定程度上影响了代码的运行速度。</p>
+<h3 id="扩展性">扩展性</h3>
+<p>整洁的代码除了是可读性强、运行效率高还有最重要的一点是它是容易扩展的。扩展性可理解为易于修改的代码。程序的扩展性代表了维护该程序程度的难易，当然可读性也是，二者都很重要。</p>
+<p>在所有的设计模式中，几乎所有的设计模式都是为了符合开闭原则，即保持程序的扩展性，重要程度可见一斑。</p>
+<p>代码都是为了一定的需求服务的，但是这些需求并不是一成不变的，当需求变更了，如果我们代码的扩展性很好，我们可能只需要简单的添加或者删除模块就行了，如果扩展性不好，可能所有代码都需要重写，那就是一场灾难了，所以提高代码的扩展性是很重要的。</p>
+<p>衡量代码扩展性可以从高内聚，低耦合这两个方面来衡量。</p>
+<blockquote>
+<p>高内聚：一个软件单位内部的关联紧密程度；有关联的事务应该放在一起。
+低耦合：两个或多个软件单位之间的关联紧密程度；软件单位之间尽可能的不要相互影响。</p>
+</blockquote>
+<h2 id="怎么写整洁的代码">怎么写整洁的代码</h2>
+<p>好的代码是不断的迭代出来的,没有人能一下子写完整 ,需求会变代码也会改变 第一次迭代可能写的代码很糟糕,这时一定要再次回头去看之前的代码,去优化,重构,让代码变得易于维护.</p>
+<p>如何写出整洁的代码,那就看你怎么理解整洁的代码,理解的不一样写出来的肯定就不一样.下面是我的几点建议</p>
+<h3 id="注释命名">注释&amp;命名</h3>
+<p>注释只是二手的信息,它和代码所传达的信息并不等价.所以，不要写没有意义的注释(冗余注释,废弃注释,等一些没有意义的信息和不恰当的信息),要知道代码有人维护,可注释没有人维护,最好的办法就是规范变量,方法的命名,做到见名知意; 如果你的方法命名足够明确就可以不用写注释了，当然一段好的注释一定是包含代码中没有体现的信息。</p>
+<p>如果要编写一条注释,就花时间尽量保证写出最好的注释 不要画蛇添足,要保持注释的简洁。比如，无用的代码直接删掉,不要注释它,不用担心会丢,版本服务会有记录能找回。编写注释和迭代代码是一样的道理。但是一般注释是没有人来维护的，因为它不会影响程序的正常运行。</p>
+<p>同样的，命名也不会影响程序的正常运行。注释和命名是不会影响程序的执行的，但是这两个因素是会影响到开发者编写代码的。它会导致开发者的认知负荷增加，从而降低编写代码的效率。</p>
+<p>“ 好的代码本身就是注释，我们要尽量规范和美化自己的代码来减少不必要的注释。若编程语言足够有表达力，就不需要注释，尽量通过代码来阐述。”编程语言的表达力很大程度上就取决于方法的命名。</p>
+<p>那什么是好的命名呢？说实话这也是我编程一直头疼的原因，总觉得命名不够好。在网络上看到一种方法觉得很不错: 把你的变量名拎出来，问别人，你看到这个名字会想到什么，他说的和你想的一致，就用，否则就改。改到基本上不懂程序的人都能大概看懂你写的是什么，那大概就是好的命名了。</p>
+<p>程序的命名我认为是约定俗成的，最初开始编程的开发者们，他们一定会遇到这个问题的，久而久之就会建立一套规则将这些命名进行统一。到了现在一定是有很多成熟的命名规则的，所以我们可以踩着前辈们的肩膀前行。</p>
+<p>虽然是约定俗成的,但是事物的发展一定不是一成不变的,我并不知道在我写下这么多文字后是否适用于未来,或许大概只有思想会适用,而那些具体的方法是一定不会适用的,但是现在我们需要具体的解决方案,或许我能给你提点建议,如果能帮到你我会很高兴的.</p>
+<p>注释</p>
+<ul>
+<li>尽量保持代码的简洁,能不用注释尽量不用注释,切记注释应该展示代码中没有展示的信息</li>
+<li>注释代码,那么应该在注释代码的上方详细的说明,而不是简单的注释,如果没有用则应该删除</li>
+<li>注释也要随着程序的修改而不断更新，一个误导的注释往往比没有注释更糟糕</li>
+</ul>
+<p>命名</p>
+<ul>
+<li>命名尽量不要使用缩写,因为意义不明确,除非缩写是外界公认的,比如: EN,CH</li>
+<li>在Java中较为适用的是驼峰命名法,如: helloWord,HelloWord ,但是这种方法如果命名过长也不能很直观的展示信息,所以尽量不要起太长的名字,否则什么方法都不管用,如果一个方法的名字过长那么很可能这个方法不止做了一件事,这时候我们需要将它拆分.</li>
+<li>接口和类的名称首字母大写(MyClass/MyInterface) ,方法的名称首字母小写(myMethod),常量的命名全部大写(MY _CONSTANT)同时用蛇形命名法,单词的分割用下划线隔开</li>
+<li>方法的命名用动词,类的命名用名词,属性的命名用名词,接口的命名用形容词或动词,抽象类的命名应以Abstract/Base为前缀,实现类命名要以impl结尾,异常类以Exception结尾</li>
+</ul>
+<h3 id="函数类">函数&amp;类</h3>
+<p>最好的方法入参参数是0个,其次是1,最多建议不超过3个,大于三个建议封装成对象,这样做的好处是方便扩展管理;在一个方法中声明变量应该在方法的最前面,我们应该降低方法的复杂度,避免出现if..else多层嵌套的情况，当然,如果一个方法过于复杂可将该方法进行拆分；还应当注意方法中异常块的处理,一般情况下是不会写的,因为有全局异常处理,如果非要写那么可能代码看起来不是那么简洁清晰.注意方法的封装.在方法调用本地方法的时候,本地的方法尽量使用基础类型作为返回值,好处是避免空指针判断和隐式拆包和打包.当我们写方法返回值的时候,如果返回值类型是数组或集合,我们应该避免返回null,否则调用方就有可能出现空指针.可以避免不必要的空指针判断。</p>
+<p>或许我应该更加细致的标出</p>
+<ul>
+<li>减少函数的入参数量，控制在三个以内，超过三个封装成对象</li>
+<li>使用卫语句，策略模式，职责链模式来减少if..else多层嵌套和不必要的else；用三元运算符代替简单if&hellip;else（根据不同的情境使用，可能会影响代码的可读性）</li>
+<li>拆分超长函数(函数行数阈值80~100行左右就要考虑拆分)；复杂的条件表达式，循环语句，代码块，lambda匿名内部类，都可以单独将其封装成方法；如果是方法内部调用方法的返回值应尽量用基础类型 （并不是方法越多越好，方法之间的互相调用也会影响性能，增加复杂度，请根据实际情况拆分）</li>
+<li>方法的返回值如果是集合或者数组，不要返回null，尽量返回空值，这样可以避免空指针的判断，从而精简代码</li>
+</ul>
+<p>除了上述的几点以外，在写函数的时候还要遵循单一职责原则，即每个方法只做一件事，好处是方便管理,代码可读性会提高,复杂度降低 易于维护。也要遵循开闭原则，这会使你的代码更加灵活。当然这些代码肯定不是一次就写出来的，好的代码需要迭代，需要打磨。在你写完几个函数之后，可能会发现重复的地方，这时候就需要将他们抽象出来。</p>
+<p>许许多多的函数组成了类,当函数之间相互调用的时候，就会存在多个类之间的联系，所以在编写类的时候要注意类之间的依赖关系，使它们别那么耦合，一般会遵循迪米特法则。</p>
+<p>属性的存在使类中的元素更加丰富，一般情况下属性在类中都是私有的，会对外提供set，get方法供外部调用修改；这样做的好处是方便控制外部调用，假如你想公共处理某个属性给它加个前缀，就可以通过调用该类中涉及到该属性的方法进行修改，如果你直接修改属性那么改起来会很麻烦。</p>
+<p>极少数情况是公共的，比如定义一个常量类，公共的资源属性。还有多数情况下是受保护的，该种情况一般是用来给子类使用的，当然同一个包下也能访问得到。</p>
+<h3 id="代码结构">代码结构</h3>
+<p>高内聚低耦合，这是我们写代码应该遵循的标准。内聚代表着职责的专一，这是整洁的一个很重要准则。从大的方面来说，系统的使用与构造需要明确的区分开，才不会将整个结构混杂在一起。与此同时，决定了系统的数据流走向也是决定了整个系统的层级划分，不同的层级也需要明确的区分开来。</p>
+<p>那么应该怎么划分代码的结构?最简单的应该同类型的相关联的表需要放在一个类中或一个包中,写一些方法对外提供api,供其他方法调用，而不是跨层调用。</p>
+<p>一个好的结构使代码看上去更加清晰,更加容易维护,其实它更像是对系统架构的拆分。最常见的系统分层应该是MVC结构，即模型层、视图层、控制层。我们应当更加详细的将MVC进行划分，最常见的我们将控制层又分为业务层（service）和持久层（dao）。 划分的目的是规划软件系统的逻辑结构便于开发维护。但是，随着微服务的演变和不同研发的编码习惯，往往导致了代码分层不彻底导致引入了“坏味道”。</p>
+<p>划分代码我认为最重要的作用是使结构单一，减少代码之间的依赖性，降低耦合度，从而提高代码的可维护性。</p>
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diff --git a/docs/posts/codeguide/eye-beam/index.html b/docs/posts/codeguide/eye-beam/index.html
new file mode 100644
index 00000000..efca863b
--- /dev/null
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@@ -0,0 +1,2612 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
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+    <meta name="author" content="whitepure" />
+	
+	
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+	<title>Java程序常见故障排查命令及工具 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="故障排查命令 收录Linux常用命令，以下命令来自https://www.bilibili.com/video/BV14A411378a 关机/重启/注销 常用命令 作" />
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+
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+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
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+                    故障排查命令
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+            <li class="nav-item">
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+                    关机/重启/注销
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+            </li>
+            
+            
+        </ul>
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+        
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+        
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b3%bb%e7%bb%9f%e4%bf%a1%e6%81%af%e5%92%8c%e6%80%a7%e8%83%bd%e6%9f%a5%e7%9c%8b">
+                    系统信息和性能查看
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+        
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%a3%81%e7%9b%98%e5%92%8c%e5%88%86%e5%8c%ba">
+                    磁盘和分区
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+            </li>
+            
+            
+        </ul>
+        
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+        <ul class="nav">
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%88%b7%e5%92%8c%e6%88%b7%e7%bb%84">
+                    ⽤户和⽤户组
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%9c%e5%92%8c%e8%bf%9b%e7%a8%8b%e7%ae%a1%e7%90%86">
+                    ⽹络和进程管理
+                </a>
+            </li>
+            
+            
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+        
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+        
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+        
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+                    常⻅系统服务命令
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%b6%e5%92%8c%e5%bd%95%e6%93%8d%e4%bd%9c">
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+            </li>
+            
+            
+        </ul>
+        
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+                    ⽂件查看和处理
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+            </li>
+            
+            
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+        
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+        
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+        
+        
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+        
+        
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+                    打包和解压
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
+        
+        
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+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#rpm%e5%8c%85%e7%ae%a1%e7%90%86%e5%91%bd%e4%bb%a4">
+                    RPM包管理命令
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+        <ul class="nav">
+            
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#yum%e5%8c%85%e7%ae%a1%e7%90%86%e5%91%bd%e4%bb%a4">
+                    YUM包管理命令
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#dpkg%e5%8c%85%e7%ae%a1%e7%90%86%e5%91%bd%e4%bb%a4">
+                    DPKG包管理命令
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        
+        <ul class="nav">
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#apt%e8%bd%af%e4%bb%b6%e5%85%b7">
+                    APT软件⼯具
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
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+                    故障排查分析工具
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jdk%e8%87%aa%e5%b8%a6%e5%88%86%e6%9e%90%e5%b7%a5%e5%85%b7">
+                    JDK自带分析工具
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jps">
+                    jps
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
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+                <a class="nav-link text-left" href="#jstat">
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+                <a class="nav-link text-left" href="#jstack">
+                    jstack
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+                <a class="nav-link text-left" href="#jcmd">
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+                </a>
+                
+            </div>
+
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+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
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+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Java程序常见故障排查命令及工具</h2>
+                        <span id="post_page_title_date" class="date">2021.09.08</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="故障排查命令">故障排查命令</h2>
+<p>收录Linux常用命令，以下命令来自<a href="https://www.bilibili.com/video/BV14A411378a">https://www.bilibili.com/video/BV14A411378a</a></p>
+<h3 id="关机重启注销">关机/重启/注销</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>shutdown -h now</td>
+<td>即刻关机</td>
+</tr>
+<tr>
+<td>shutdown -h 10</td>
+<td>10分钟后关机</td>
+</tr>
+<tr>
+<td>shutdown -h 11:00</td>
+<td>11：00关机</td>
+</tr>
+<tr>
+<td>shutdown -h +10</td>
+<td>预定时间关机（10分钟后）</td>
+</tr>
+<tr>
+<td>shutdown -c</td>
+<td>取消指定时间关机</td>
+</tr>
+<tr>
+<td>shutdown -r now</td>
+<td>重启</td>
+</tr>
+<tr>
+<td>shutdown -r 10</td>
+<td>10分钟之后重启</td>
+</tr>
+<tr>
+<td>shutdown -r 11:00</td>
+<td>定时重启</td>
+</tr>
+<tr>
+<td>reboot</td>
+<td>重启</td>
+</tr>
+<tr>
+<td>init 6</td>
+<td>重启</td>
+</tr>
+<tr>
+<td>init 0</td>
+<td>⽴刻关机</td>
+</tr>
+<tr>
+<td>telinit 0</td>
+<td>关机</td>
+</tr>
+<tr>
+<td>poweroff</td>
+<td>⽴刻关机</td>
+</tr>
+<tr>
+<td>halt</td>
+<td>关机</td>
+</tr>
+<tr>
+<td>sync</td>
+<td>buff数据同步到磁盘</td>
+</tr>
+<tr>
+<td>logout</td>
+<td>退出登录Shell</td>
+</tr>
+</tbody>
+</table>
+<h3 id="系统信息和性能查看">系统信息和性能查看</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>uname -a</td>
+<td>查看内核/OS/CPU信息</td>
+</tr>
+<tr>
+<td>uname -r</td>
+<td>查看内核版本</td>
+</tr>
+<tr>
+<td>uname -m</td>
+<td>查看处理器架构</td>
+</tr>
+<tr>
+<td>arch</td>
+<td>查看处理器架构</td>
+</tr>
+<tr>
+<td>hostname</td>
+<td>查看计算机名</td>
+</tr>
+<tr>
+<td>who</td>
+<td>显示当前登录系统的⽤户</td>
+</tr>
+<tr>
+<td>who am i</td>
+<td>显示登录时的⽤户名</td>
+</tr>
+<tr>
+<td>whoami</td>
+<td>显示当前⽤户名</td>
+</tr>
+<tr>
+<td>cat /proc/version</td>
+<td>查看linux版本信息</td>
+</tr>
+<tr>
+<td>cat /proc/cpuinfo</td>
+<td>查看CPU信息</td>
+</tr>
+<tr>
+<td>cat /proc/interrupts</td>
+<td>查看中断</td>
+</tr>
+<tr>
+<td>cat /proc/loadavg</td>
+<td>查看系统负载</td>
+</tr>
+<tr>
+<td>uptime</td>
+<td>查看系统运⾏时间、⽤户数、负载</td>
+</tr>
+<tr>
+<td>env</td>
+<td>查看系统的环境变量</td>
+</tr>
+<tr>
+<td>lsusb -tv</td>
+<td>查看系统USB设备信息</td>
+</tr>
+<tr>
+<td>lspci -tv</td>
+<td>查看系统PCI设备信息</td>
+</tr>
+<tr>
+<td>lsmod</td>
+<td>查看已加载的系统模块</td>
+</tr>
+<tr>
+<td>grep MemTotal /proc/meminfo</td>
+<td>查看内存总量</td>
+</tr>
+<tr>
+<td>grep MemFree /proc/meminfo</td>
+<td>查看空闲内存量</td>
+</tr>
+<tr>
+<td>free -m</td>
+<td>查看内存⽤量和交换区⽤量</td>
+</tr>
+<tr>
+<td>date</td>
+<td>显示系统⽇期时间</td>
+</tr>
+<tr>
+<td>cal 2021</td>
+<td>显示2021⽇历表</td>
+</tr>
+<tr>
+<td>top</td>
+<td>动态显示cpu/内存/进程等情况</td>
+</tr>
+<tr>
+<td>vmstat 1 20</td>
+<td>每1秒采⼀次系统状态，采20次</td>
+</tr>
+<tr>
+<td>iostat</td>
+<td>查看io读写/cpu使⽤情况</td>
+</tr>
+<tr>
+<td>查看io读写/cpu使⽤情况</td>
+<td>查询cpu使⽤情况（1秒⼀次，共10次）</td>
+</tr>
+<tr>
+<td>sar -d 1 10</td>
+<td>查询磁盘性能</td>
+</tr>
+</tbody>
+</table>
+<h3 id="磁盘和分区">磁盘和分区</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>fdisk -l</td>
+<td>查看所有磁盘分区</td>
+</tr>
+<tr>
+<td>swapon -s</td>
+<td>查看所有交换分区</td>
+</tr>
+<tr>
+<td>df -h</td>
+<td>查看磁盘使⽤情况及挂载点</td>
+</tr>
+<tr>
+<td>df -hl</td>
+<td>同上</td>
+</tr>
+<tr>
+<td>du -sh /dir</td>
+<td>查看指定某个⽬录的⼤⼩</td>
+</tr>
+<tr>
+<td>du -sk * | sort -rn</td>
+<td>从⾼到低依次显示⽂件和⽬录⼤⼩</td>
+</tr>
+<tr>
+<td>mount /dev/hda2 /mnt/hda2</td>
+<td>挂载hda2盘</td>
+</tr>
+<tr>
+<td>mount -t ntfs /dev/sdc1 /mnt/usbhd1</td>
+<td>指定⽂件系统类型挂载（如ntfs）</td>
+</tr>
+<tr>
+<td>mount -o loop xxx.iso /mnt/cdrom</td>
+<td>挂 载 iso ⽂ 件</td>
+</tr>
+<tr>
+<td>umount -v /dev/sda1</td>
+<td>通过设备名卸载</td>
+</tr>
+<tr>
+<td>umount -v /mnt/mymnt</td>
+<td>通过挂载点卸载</td>
+</tr>
+<tr>
+<td>fuser -km /mnt/hda1</td>
+<td>强制卸载(慎⽤)</td>
+</tr>
+</tbody>
+</table>
+<h3 id="户和户组">⽤户和⽤户组</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>useradd codesheep</td>
+<td>创建⽤户</td>
+</tr>
+<tr>
+<td>userdel -r codesheep</td>
+<td>删除⽤户</td>
+</tr>
+<tr>
+<td>usermod -g group_name user_name</td>
+<td>修改⽤户的组</td>
+</tr>
+<tr>
+<td>usermod -aG group_name user_name</td>
+<td>将⽤户添加到组</td>
+</tr>
+<tr>
+<td>usermod -s /bin/ksh -d /home/codepig –g dev codesheep</td>
+<td>修改⽤户codesheep的登录Shell、主⽬录以及⽤户组</td>
+</tr>
+<tr>
+<td>groups test</td>
+<td>查看test⽤户所在的组</td>
+</tr>
+<tr>
+<td>groupadd group_name</td>
+<td>创建⽤户组</td>
+</tr>
+<tr>
+<td>groupdel group_name</td>
+<td>删除⽤户组</td>
+</tr>
+<tr>
+<td>groupmod -n new_name old_name</td>
+<td>重命名⽤户组</td>
+</tr>
+<tr>
+<td>su - user_name</td>
+<td>su - user_name</td>
+</tr>
+<tr>
+<td>passwd</td>
+<td>修改⼝令</td>
+</tr>
+<tr>
+<td>passwd codesheep</td>
+<td>修改某⽤户的⼝令</td>
+</tr>
+<tr>
+<td>w</td>
+<td>查看活动⽤户</td>
+</tr>
+<tr>
+<td>id codesheep</td>
+<td>查看指定⽤户codesheep信息</td>
+</tr>
+<tr>
+<td>last</td>
+<td>查看⽤户登录⽇志</td>
+</tr>
+<tr>
+<td>crontab -l</td>
+<td>查看当前⽤户的计划任务</td>
+</tr>
+<tr>
+<td>cut -d: -f1 /etc/passwd</td>
+<td>查看系统所有⽤户</td>
+</tr>
+<tr>
+<td>cut -d: -f1 /etc/group</td>
+<td>查看系统所有组</td>
+</tr>
+</tbody>
+</table>
+<h3 id="络和进程管理">⽹络和进程管理</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>ifconfig</td>
+<td>查看⽹络接⼝属性</td>
+</tr>
+<tr>
+<td>ifconfig eth0</td>
+<td>查看某⽹卡的配置</td>
+</tr>
+<tr>
+<td>route -n</td>
+<td>查看路由表</td>
+</tr>
+<tr>
+<td>netstat -lntp</td>
+<td>查看所有监听端⼝</td>
+</tr>
+<tr>
+<td>netstat -antp</td>
+<td>查看已经建⽴的TCP连接</td>
+</tr>
+<tr>
+<td>netstat -lutp</td>
+<td>查看TCP/UDP的状态信息</td>
+</tr>
+<tr>
+<td>ifup eth0</td>
+<td>启⽤eth0⽹络设备</td>
+</tr>
+<tr>
+<td>ifdown eth0</td>
+<td>禁⽤eth0⽹络设备</td>
+</tr>
+<tr>
+<td>iptables -L</td>
+<td>查看iptables规则</td>
+</tr>
+<tr>
+<td>ifconfig eth0 192.168.1.1 netmask 255.255.255.0</td>
+<td>配置ip地址</td>
+</tr>
+<tr>
+<td>dhclient eth0</td>
+<td>以dhcp模式启⽤eth0</td>
+</tr>
+<tr>
+<td>route add -net 0/0 gw Gateway_IP</td>
+<td>配置默认⽹关</td>
+</tr>
+<tr>
+<td>route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1</td>
+<td>配置静态路由到达⽹络'192.168.0.0/16'</td>
+</tr>
+<tr>
+<td>route del 0/0 gw Gateway_IP</td>
+<td>删除静态路由</td>
+</tr>
+<tr>
+<td>hostname</td>
+<td>查看主机名</td>
+</tr>
+<tr>
+<td>host <a href="http://www.baidu.com">www.baidu.com</a></td>
+<td>解析主机名</td>
+</tr>
+<tr>
+<td>nslookup <a href="http://www.baidu.com">www.baidu.com</a></td>
+<td>查询DNS记录，查看域名解析是否正常</td>
+</tr>
+<tr>
+<td>ps -ef</td>
+<td>查看所有进程</td>
+</tr>
+<tr>
+<td>ps -ef | grep codesheep</td>
+<td>过滤出你需要的进程</td>
+</tr>
+<tr>
+<td>kill -s name</td>
+<td>kill指定名称的进程</td>
+</tr>
+<tr>
+<td>kill -s pid</td>
+<td>kill指定pid的进程</td>
+</tr>
+<tr>
+<td>top</td>
+<td>实时显示进程状态</td>
+</tr>
+<tr>
+<td>vmstat 1 20</td>
+<td>每1秒采⼀次系统状态，采20次</td>
+</tr>
+<tr>
+<td>iostat</td>
+<td>iostat</td>
+</tr>
+<tr>
+<td>sar -u 1 10</td>
+<td>查询cpu使⽤情况（1秒⼀次，共10次）</td>
+</tr>
+<tr>
+<td>sar -d 1 10</td>
+<td>查询磁盘性能</td>
+</tr>
+</tbody>
+</table>
+<h3 id="常系统服务命令">常⻅系统服务命令</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>chkconfig &ndash;list</td>
+<td>列出系统服务</td>
+</tr>
+<tr>
+<td>service &lt;服务名&gt; status</td>
+<td>查看某个服务</td>
+</tr>
+<tr>
+<td>service &lt;服务名&gt; start</td>
+<td>启动某个服务</td>
+</tr>
+<tr>
+<td>service &lt;服务名&gt; stop</td>
+<td>终⽌某个服务</td>
+</tr>
+<tr>
+<td>service &lt;服务名&gt; restart</td>
+<td>重启某个服务</td>
+</tr>
+<tr>
+<td>systemctl status &lt;服务名&gt;</td>
+<td>查看某个服务</td>
+</tr>
+<tr>
+<td>systemctl start &lt;服务名&gt;</td>
+<td>启动某个服务</td>
+</tr>
+<tr>
+<td>systemctl stop &lt;服务名&gt;</td>
+<td>终⽌某个服务</td>
+</tr>
+<tr>
+<td>systemctl restart &lt;服务名&gt;</td>
+<td>重启某个服务</td>
+</tr>
+<tr>
+<td>systemctl enable &lt;服务名&gt;</td>
+<td>关闭⾃启动</td>
+</tr>
+<tr>
+<td>systemctl disable &lt;服务名&gt;</td>
+<td>关闭⾃启动</td>
+</tr>
+</tbody>
+</table>
+<h3 id="件和录操作">⽂件和⽬录操作</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>cd &lt;⽬录名&gt;</td>
+<td>进⼊某个⽬录</td>
+</tr>
+<tr>
+<td>cd ..</td>
+<td>回上级⽬录</td>
+</tr>
+<tr>
+<td>cd ../..</td>
+<td>回上两级⽬录</td>
+</tr>
+<tr>
+<td>cd</td>
+<td>进个⼈主⽬录</td>
+</tr>
+<tr>
+<td>cd -</td>
+<td>回上⼀步所在⽬录</td>
+</tr>
+<tr>
+<td>pwd</td>
+<td>显示当前路径</td>
+</tr>
+<tr>
+<td>ls</td>
+<td>查看⽂件⽬录列表</td>
+</tr>
+<tr>
+<td>ls -F</td>
+<td>查看⽬录中内容（显示是⽂件还是⽬录）</td>
+</tr>
+<tr>
+<td>ls -l</td>
+<td>查看⽂件和⽬录的详情列表</td>
+</tr>
+<tr>
+<td>ls -a</td>
+<td>查看隐藏⽂件</td>
+</tr>
+<tr>
+<td>ls -lh</td>
+<td>查看⽂件和⽬录的详情列表（增强⽂件⼤⼩易读性）</td>
+</tr>
+<tr>
+<td>ls -lSr</td>
+<td>查看⽂件和⽬录列表（以⽂件⼤⼩升序查看）</td>
+</tr>
+<tr>
+<td>tree</td>
+<td>查看⽂件和⽬录的树形结构</td>
+</tr>
+<tr>
+<td>mkdir &lt;⽬录名&gt;</td>
+<td>创建⽬录</td>
+</tr>
+<tr>
+<td>mkdir dir1 dir2</td>
+<td>同时创建两个⽬录</td>
+</tr>
+<tr>
+<td>mkdir -p /tmp/dir1/dir2</td>
+<td>创建⽬录树</td>
+</tr>
+<tr>
+<td>rm -f file1</td>
+<td>删除&rsquo;file1&rsquo;⽂件</td>
+</tr>
+<tr>
+<td>rmdir dir1</td>
+<td>删除&rsquo;dir1&rsquo;⽬录</td>
+</tr>
+<tr>
+<td>rm -rf dir1</td>
+<td>删除&rsquo;dir1&rsquo;⽬录和其内容</td>
+</tr>
+<tr>
+<td>rm -rf dir1 dir2</td>
+<td>同时删除两个⽬录及其内容</td>
+</tr>
+<tr>
+<td>mv old_dir new_dir</td>
+<td>重命名/移动⽬录</td>
+</tr>
+<tr>
+<td>cp file1 file2</td>
+<td>复制⽂件</td>
+</tr>
+<tr>
+<td>cp dir/* .</td>
+<td>复制某⽬录下的所有⽂件⾄当前⽬录</td>
+</tr>
+<tr>
+<td>cp -a dir1 dir2</td>
+<td>复制⽬录</td>
+</tr>
+<tr>
+<td>cp -a /tmp/dir1 .</td>
+<td>复制⼀个⽬录⾄当前⽬录</td>
+</tr>
+<tr>
+<td>ln -s file1 link1</td>
+<td>创建指向⽂件/⽬录的软链接</td>
+</tr>
+<tr>
+<td>ln file1 lnk1</td>
+<td>创建指向⽂件/⽬录的物理链接</td>
+</tr>
+<tr>
+<td>find / -name file1</td>
+<td>从跟⽬录开始搜索⽂件/⽬录</td>
+</tr>
+<tr>
+<td>find / -user user1</td>
+<td>搜索⽤户user1的⽂件/⽬录</td>
+</tr>
+<tr>
+<td>find /dir -name *.bin</td>
+<td>在⽬录/dir中搜带有.bin后缀的⽂件</td>
+</tr>
+<tr>
+<td>locate &lt;关键词&gt;</td>
+<td>快速定位⽂件</td>
+</tr>
+<tr>
+<td>locate *.mp4</td>
+<td>寻找.mp4结尾的⽂件</td>
+</tr>
+<tr>
+<td>whereis &lt;关键词&gt;</td>
+<td>显示某⼆进制⽂件/可执⾏⽂件的路径</td>
+</tr>
+<tr>
+<td>which &lt;关键词&gt;</td>
+<td>查找系统⽬录下某的⼆进制⽂件</td>
+</tr>
+<tr>
+<td>chmod ugo+rwx dir1</td>
+<td>设置⽬录所有者(u)、群组(g)及其他⼈(o)的读（r）写(w)执⾏(x)权限</td>
+</tr>
+<tr>
+<td>chmod go-rwx dir1</td>
+<td>移除群组(g)与其他⼈(o)对⽬录的读写执⾏权限</td>
+</tr>
+<tr>
+<td>chown user1 file1</td>
+<td>改变⽂件的所有者属性</td>
+</tr>
+<tr>
+<td>chown -R user1 dir1</td>
+<td>改变⽬录的所有者属性</td>
+</tr>
+<tr>
+<td>chgrp group1 file1</td>
+<td>改变⽂件群组</td>
+</tr>
+<tr>
+<td>chown user1:group1 file1</td>
+<td>改变⽂件的所有⼈和群组</td>
+</tr>
+</tbody>
+</table>
+<h3 id="件查看和处理">⽂件查看和处理</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>cat file1</td>
+<td>查看⽂件内容</td>
+</tr>
+<tr>
+<td>cat -n file1</td>
+<td>查看内容并标示⾏数</td>
+</tr>
+<tr>
+<td>tac file1</td>
+<td>从最后⼀⾏开始反看⽂件内容</td>
+</tr>
+<tr>
+<td>more file1</td>
+<td>more file1</td>
+</tr>
+<tr>
+<td>less file1</td>
+<td>类似more命令，但允许反向操作</td>
+</tr>
+<tr>
+<td>head -2 file1</td>
+<td>查看⽂件前两⾏</td>
+</tr>
+<tr>
+<td>tail -2 file1</td>
+<td>查看⽂件后两⾏</td>
+</tr>
+<tr>
+<td>tail -f /log/msg</td>
+<td>实时查看添加到⽂件中的内容</td>
+</tr>
+<tr>
+<td>grep codesheep hello.txt</td>
+<td>在⽂件hello.txt中查找关键词codesheep</td>
+</tr>
+<tr>
+<td>grep ^sheep hello.txt</td>
+<td>在⽂件hello.txt中查找以sheep开头的内容</td>
+</tr>
+<tr>
+<td>grep [0-9] hello.txt</td>
+<td>选择hello.txt⽂件中所有包含数字的⾏</td>
+</tr>
+<tr>
+<td>sed &rsquo;s/s1/s2/g&rsquo; hello.txt</td>
+<td>将hello.txt⽂件中的s1替换成s2</td>
+</tr>
+<tr>
+<td>sed &lsquo;/^$/d&rsquo; hello.txt</td>
+<td>从hello.txt⽂件中删除所有空⽩⾏</td>
+</tr>
+<tr>
+<td>sed &lsquo;/ *#/d; /^$/d&rsquo; hello.txt</td>
+<td>从hello.txt⽂件中删除所有注释和空⽩⾏</td>
+</tr>
+<tr>
+<td>sed -e &lsquo;1d&rsquo; hello.txt</td>
+<td>从⽂件hello.txt 中排除第⼀⾏</td>
+</tr>
+<tr>
+<td>sed -n &lsquo;/s1/p&rsquo; hello.txt</td>
+<td>查看只包含关键词&quot;s1&quot;的⾏</td>
+</tr>
+<tr>
+<td>sed -e &rsquo;s/ *$//&rsquo; hello.txt</td>
+<td>删除每⼀⾏最后的空⽩字符</td>
+</tr>
+<tr>
+<td>sed -e &rsquo;s/s1//g&rsquo; hello.txt</td>
+<td>从⽂档中只删除词汇s1并保留剩余全部</td>
+</tr>
+<tr>
+<td>sed -n &lsquo;1,5p;5q&rsquo; hello.txt</td>
+<td>查看从第⼀⾏到第5⾏内容</td>
+</tr>
+<tr>
+<td>sed -n &lsquo;5p;5q&rsquo; hello.txt</td>
+<td>查看第5⾏</td>
+</tr>
+<tr>
+<td>paste file1 file2</td>
+<td>合并两个⽂件或两栏的内容</td>
+</tr>
+<tr>
+<td>paste -d &lsquo;+&rsquo; file1 file2</td>
+<td>合并两个⽂件或两栏的内容，中间⽤&quot;+&ldquo;区分</td>
+</tr>
+<tr>
+<td>sort file1 file2</td>
+<td>排序两个⽂件的内容</td>
+</tr>
+<tr>
+<td>comm -1 file1 file2</td>
+<td>⽐较两个⽂件的内容(去除&rsquo;file1&rsquo;所含内容)</td>
+</tr>
+<tr>
+<td>comm -2 file1 file2</td>
+<td>⽐较两个⽂件的内容(去除&rsquo;file2&rsquo;所含内容</td>
+</tr>
+<tr>
+<td>comm -3 file1 file2</td>
+<td>⽐较两个⽂件的内容(去除两⽂件共有部分)</td>
+</tr>
+</tbody>
+</table>
+<h3 id="打包和解压">打包和解压</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>zip xxx.zip file</td>
+<td>压缩⾄zip包</td>
+</tr>
+<tr>
+<td>zip -r xxx.zip file1 file2 dir1</td>
+<td>将多个⽂件+⽬录压成zip包</td>
+</tr>
+<tr>
+<td>unzip xxx.zip</td>
+<td>解压zip包</td>
+</tr>
+<tr>
+<td>tar -cvf xxx.tar file</td>
+<td>创建⾮压缩tar包</td>
+</tr>
+<tr>
+<td>tar -cvf xxx.tar file1 file2 dir1</td>
+<td>将多个⽂件+⽬录打tar包</td>
+</tr>
+<tr>
+<td>tar -tf xxx.tar</td>
+<td>查看tar包的内容</td>
+</tr>
+<tr>
+<td>tar -xvf xxx.tar</td>
+<td>解压tar包</td>
+</tr>
+<tr>
+<td>tar -xvf xxx.tar -C /dir</td>
+<td>将tar包解压⾄指定⽬录</td>
+</tr>
+<tr>
+<td>tar -cvfj xxx.tar.bz2 dir</td>
+<td>创建bz2压缩包</td>
+</tr>
+<tr>
+<td>tar -jxvf xxx.tar.bz2</td>
+<td>解压bz2压缩包</td>
+</tr>
+<tr>
+<td>tar -cvfz xxx.tar.gz dir</td>
+<td>创建gzip压缩包</td>
+</tr>
+<tr>
+<td>tar -zxvf xxx.tar.gz</td>
+<td>解压gzip压缩包</td>
+</tr>
+<tr>
+<td>bunzip2 xxx.bz2</td>
+<td>解压bz2压缩包</td>
+</tr>
+<tr>
+<td>bzip2 filename</td>
+<td>压缩⽂件</td>
+</tr>
+<tr>
+<td>gunzip xxx.gz</td>
+<td>解压gzip压缩包</td>
+</tr>
+<tr>
+<td>gzip filename</td>
+<td>压缩⽂件</td>
+</tr>
+<tr>
+<td>gzip -9 filename</td>
+<td>最⼤程度压缩</td>
+</tr>
+</tbody>
+</table>
+<h3 id="rpm包管理命令">RPM包管理命令</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>rpm -qa</td>
+<td>查看已安装的rpm包</td>
+</tr>
+<tr>
+<td>rpm -q pkg_name</td>
+<td>查询某个rpm包</td>
+</tr>
+<tr>
+<td>rpm -q &ndash;whatprovides xxx</td>
+<td>显示xxx功能是由哪个包提供的</td>
+</tr>
+<tr>
+<td>rpm -q &ndash;whatrequires xxx</td>
+<td>显示xxx功能被哪个程序包依赖的</td>
+</tr>
+<tr>
+<td>rpm -q &ndash;changelog xxx</td>
+<td>显示xxx包的更改记录</td>
+</tr>
+<tr>
+<td>rpm -qi pkg_name</td>
+<td>查看⼀个包的详细信息</td>
+</tr>
+<tr>
+<td>rpm -qd pkg_name</td>
+<td>查询⼀个包所提供的⽂档</td>
+</tr>
+<tr>
+<td>rpm -qc pkg_name</td>
+<td>查看已安装rpm包提供的配置⽂件</td>
+</tr>
+<tr>
+<td>rpm -ql pkg_name</td>
+<td>查看⼀个包安装了哪些⽂件</td>
+</tr>
+<tr>
+<td>rpm -qf filename</td>
+<td>查看某个⽂件属于哪个包</td>
+</tr>
+<tr>
+<td>rpm -qR pkg_name</td>
+<td>查询包的依赖关系</td>
+</tr>
+<tr>
+<td>rpm -ivh xxx.rpm</td>
+<td>安装rpm包</td>
+</tr>
+<tr>
+<td>rpm -ivh &ndash;test xxx.rpm</td>
+<td>测试安装rpm包</td>
+</tr>
+<tr>
+<td>rpm -ivh &ndash;nodeps xxx.rpm</td>
+<td>安装rpm包时忽略依赖关系</td>
+</tr>
+<tr>
+<td>rpm -e xxx</td>
+<td>卸载程序包</td>
+</tr>
+<tr>
+<td>rpm -Fvh pkg_name</td>
+<td>升级确定已安装的rpm包</td>
+</tr>
+<tr>
+<td>rpm -Uvh pkg_name</td>
+<td>升级rpm包(若未安装则会安装)</td>
+</tr>
+<tr>
+<td>rpm -V pkg_name</td>
+<td>RPM包详细信息校验</td>
+</tr>
+</tbody>
+</table>
+<h3 id="yum包管理命令">YUM包管理命令</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>yum repolist enabled</td>
+<td>显示可⽤的源仓库</td>
+</tr>
+<tr>
+<td>yum search pkg_name</td>
+<td>搜索软件包</td>
+</tr>
+<tr>
+<td>yum install pkg_name</td>
+<td>下载并安装软件包</td>
+</tr>
+<tr>
+<td>yum install &ndash;downloadonly pkg_name</td>
+<td>只下载不安装</td>
+</tr>
+<tr>
+<td>yum list</td>
+<td>显示所有程序包</td>
+</tr>
+<tr>
+<td>yum list installed</td>
+<td>查看当前系统已安装包</td>
+</tr>
+<tr>
+<td>yum list updates</td>
+<td>查看可以更新的包列表</td>
+</tr>
+<tr>
+<td>yum check-update</td>
+<td>查看可升级的软件包</td>
+</tr>
+<tr>
+<td>yum update</td>
+<td>更新所有软件包</td>
+</tr>
+<tr>
+<td>yum update pkg_name</td>
+<td>升级指定软件包</td>
+</tr>
+<tr>
+<td>yum deplist pkg_name</td>
+<td>列出软件包依赖关系</td>
+</tr>
+<tr>
+<td>yum remove pkg_name</td>
+<td>删除软件包</td>
+</tr>
+<tr>
+<td>yum clean all</td>
+<td>清除缓存</td>
+</tr>
+<tr>
+<td>yum clean packages</td>
+<td>清除缓存的软件包</td>
+</tr>
+<tr>
+<td>yum clean headers</td>
+<td>清除缓存的header</td>
+</tr>
+</tbody>
+</table>
+<h3 id="dpkg包管理命令">DPKG包管理命令</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>dpkg -c xxx.deb</td>
+<td>列出deb包的内容</td>
+</tr>
+<tr>
+<td>dpkg -i xxx.deb</td>
+<td>安装/更新deb包</td>
+</tr>
+<tr>
+<td>dpkg -r pkg_name</td>
+<td>移除deb包</td>
+</tr>
+<tr>
+<td>dpkg -P pkg_name</td>
+<td>移除deb包(不保留配置)</td>
+</tr>
+<tr>
+<td>dpkg -l</td>
+<td>查看系统中已安装deb包</td>
+</tr>
+<tr>
+<td>dpkg -l pkg_name</td>
+<td>显示包的⼤致信息</td>
+</tr>
+<tr>
+<td>dpkg -L pkg_name</td>
+<td>查看deb包安装的⽂件</td>
+</tr>
+<tr>
+<td>dpkg -s pkg_name</td>
+<td>查看包的详细信息</td>
+</tr>
+<tr>
+<td>dpkg –unpack xxx.deb</td>
+<td>解开deb包的内容</td>
+</tr>
+</tbody>
+</table>
+<h3 id="apt软件具">APT软件⼯具</h3>
+<table>
+<thead>
+<tr>
+<th>常用命令</th>
+<th>作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>apt-cache search pkg_name</td>
+<td>搜索程序包</td>
+</tr>
+<tr>
+<td>apt-cache show pkg_name</td>
+<td>获取包的概览信息</td>
+</tr>
+<tr>
+<td>apt-get install pkg_name</td>
+<td>安装/升级软件包</td>
+</tr>
+<tr>
+<td>apt-get purge pkg_name</td>
+<td>卸载软件（包括配置）</td>
+</tr>
+<tr>
+<td>apt-get remove pkg_name</td>
+<td>卸载软件（不包括配置）</td>
+</tr>
+<tr>
+<td>apt-get update</td>
+<td>更新包索引信息</td>
+</tr>
+<tr>
+<td>apt-get upgrade</td>
+<td>更新已安装软件包</td>
+</tr>
+<tr>
+<td>apt-get clean</td>
+<td>清理缓存</td>
+</tr>
+</tbody>
+</table>
+<h2 id="故障排查分析工具">故障排查分析工具</h2>
+<h3 id="jdk自带分析工具">JDK自带分析工具</h3>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://segmentfault.com/a/1190000038209665">https://segmentfault.com/a/1190000038209665</a></li>
+<li><a href="https://www.cnblogs.com/kongzhongqijing/articles/5534624.html">https://www.cnblogs.com/kongzhongqijing/articles/5534624.html</a></li>
+</ul>
+<h4 id="jps">jps</h4>
+<p>jps查询系统内所有HotSpot进程，它位于java的bin目录下。</p>
+<table>
+<thead>
+<tr>
+<th>命令</th>
+<th>含义</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>jps</td>
+<td>输出当前运行主类名称，进程ID</td>
+</tr>
+<tr>
+<td>jps -q</td>
+<td>只列出进程ID</td>
+</tr>
+<tr>
+<td>jps -l</td>
+<td>输出当前运行主类的全称，进程ID</td>
+</tr>
+<tr>
+<td>jps -v</td>
+<td>输出虚拟机进程启动时<code>JVM</code>参数</td>
+</tr>
+</tbody>
+</table>
+<h4 id="jstat">jstat</h4>
+<p>jstat是JDK自带的一个轻量级小工具。全称“Java Virtual Machine statistics monitoring tool”，和jps一样，都在bin目录下。</p>
+<table>
+<thead>
+<tr>
+<th>命令</th>
+<th>含义</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>jstat -gc vmid 1000 10</td>
+<td>查看进程<code>pid</code>的<code>GC</code>信息，每1000毫秒 输出一次，输出10次</td>
+</tr>
+<tr>
+<td>jstat -gccause vmid 1000 10</td>
+<td>查看进程<code>pid</code>的<code>GC</code>发生的原因,每一秒（1000毫秒）输出一次，输出10次</td>
+</tr>
+<tr>
+<td>jstat -class vmid</td>
+<td>查看<code>pid</code>的加载类信息</td>
+</tr>
+<tr>
+<td>jstat -gcutil vmid</td>
+<td>对<code>java</code>垃圾回收信息的统计</td>
+</tr>
+<tr>
+<td>jstat -gcnew vmid</td>
+<td>显示新生代<code>GC</code>的情况</td>
+</tr>
+<tr>
+<td>jstat -gcold vmid</td>
+<td>显示老年代<code>GC</code>的情况</td>
+</tr>
+</tbody>
+</table>
+<h4 id="jinfo">jinfo</h4>
+<p>jinfo查看虚拟机参数信息，也可用于调整虚拟机配置参数。我们通过<code>jinfo --help</code>能看到相应的参数。</p>
+<table>
+<thead>
+<tr>
+<th>命令</th>
+<th>含义</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>jinfo pid</td>
+<td>输出关于<code>pid</code>的一堆相关信息</td>
+</tr>
+<tr>
+<td>jinfo -flags pid</td>
+<td>查看当前进程曾经赋过值的一些参数</td>
+</tr>
+<tr>
+<td>jinfo -flag name pid</td>
+<td>查看指定进程的<code>JVM</code>参数名称的参数的值</td>
+</tr>
+<tr>
+<td>jinfo -flag [+-]name pid</td>
+<td>开启或者关闭指定进程对应名称的<code>JVM</code>参数</td>
+</tr>
+<tr>
+<td>jinfo -sysprops pid</td>
+<td>来输出当前 <code>JVM</code>进行的全部的系统属性</td>
+</tr>
+</tbody>
+</table>
+<p>当使用jinfo进行修改对应进程JVM参数时，有一定的局限性。并不是所有的参数都支持修改，只有参数被标记为manageable的参数才可以被实时修改。</p>
+<p>可以使用命令查看被标记为manageable的参数：<code>java -XX:+PrintFlagsFinal -version | grep manageable</code></p>
+<h4 id="jmap">jmap</h4>
+<p>jmap全称：Java Memory Map，主要用于打印指定Java进程(或核心文件、远程调试服务器)的共享对象内存映射或堆内存细节。jmap以生成 java程序的dump文件， 也可以查看堆内对象示例的统计信息、查看ClassLoader 的信息以及 finalizer 队列。</p>
+<p>jmap命令可以获得运行中的JVM的堆的快照，从而可以离线分析堆，以检查内存泄漏，检查一些严重影响性能的大对象的创建，检查系统中什么对象最多，各种对象所占内存的大小等等。可以使用jmap生成Heap Dump。</p>
+<table>
+<thead>
+<tr>
+<th>命令</th>
+<th>含义</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>jmap -heap pid</td>
+<td>输出整个堆详细信息，包括GC的使用、堆的配置信息，以及内存的使用信息</td>
+</tr>
+<tr>
+<td>jmap -histo:live pid</td>
+<td>输出堆中对象的相关统计信息；第一列是序号，第二列是对象个数，第三列是对象大小<code>byte</code>，第四列是<code>class name</code></td>
+</tr>
+<tr>
+<td>jmap -finalizerinfo pid</td>
+<td>输出等待终结的对象信息</td>
+</tr>
+<tr>
+<td>jmap -clstats pid</td>
+<td>输出类加载器信息</td>
+</tr>
+<tr>
+<td>jmap -dump:[live],format=b,file=filename.hprof pid</td>
+<td>把进程堆内存使用情况生成到堆转储<code>dump</code>文件中,<code>live</code>子选项是可选的，假如指定<code>live</code>选项,那么只输出活的对象到文件。<code>dump</code>文件主要作用，如果发生溢出可以使用<code>dump</code>文件分析是哪些数据导致的</td>
+</tr>
+</tbody>
+</table>
+<blockquote>
+<p>Heap Dump又叫堆转储文件，指一个java进程在某一个时间点的内存快照文件。Heap Dump在触发内存快照的时候会保存以下信息：</p>
+<ul>
+<li>所有的对象</li>
+<li>所有的class</li>
+<li>GC Roots</li>
+<li>本地方法栈和本地变量</li>
+</ul>
+<p>通常在写Dump文件前会触发一次Full GC，所以Heap Dump文件里保存的对象都是Full GC后保留的对象信息。
+由于生成dump文件比较耗时，所以请耐心等待，尤其是大内存镜像生成的dump文件，则需要更长的时间来完成。</p>
+</blockquote>
+<p>可以通过参数配置当发生OOM时自动生成dump文件：<code>-XX:+HeapDumpOnOutOfMemeryError -XX:+HeapDumpPath=&lt;filename.hprof&gt;</code>,当然此种方式获取dump文件较大，如果想要获取dump文件较小可以手动获取dump文件并指定只获取存活的对象。</p>
+<h4 id="jhat">jhat</h4>
+<p>JVM Heap Analysis Tool命令是与jmap搭配使用，用来分析jmap生成的dump文件，jhat内置了一个微型的HTTP/HTML服务器，生成dump的分析结果后，可以在浏览器中查看。在此要注意，一般不会直接在服务器上进行分析，因为jhat是一个耗时并且耗费硬件资源的过程，一般把服务器生成的dump文件复制到本地或其他机器上进行分析。</p>
+<p>注意，jhat在jdk9中已经移除，官方对贱使用visualvm来配置jmap进行分析。</p>
+<table>
+<thead>
+<tr>
+<th>命令</th>
+<th>含义</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>jhat -port 9998 /tmp/dump.dat</td>
+<td>配合<code>jmap</code>命令使用，查看导出的<code>/tmp/dump.dat</code>文件，端口为9998；注意如果<code>dump</code>文件太大，可能需要加上<code>-J-Xmx512m</code>这种参数指定最大堆内存，即<code>jhat -J-Xmx512m -port 9998 /tmp/dump.dat</code></td>
+</tr>
+<tr>
+<td>jhat -baseline dump2.phrof dump1.phrof</td>
+<td>对比<code>dump2.phrof </code>与<code>dump1.phrof</code>文件</td>
+</tr>
+<tr>
+<td>jhat heapDump</td>
+<td>分析<code>dump</code>文件,默认端口为7000</td>
+</tr>
+</tbody>
+</table>
+<h4 id="jstack">jstack</h4>
+<p>jstack，全称JVM Stack Trace栈空间追踪，用于生成虚拟机指定进程当前线程快照；主要分析堆栈空间，也就是分析线程的情况，可以分析出死锁问题，以及cpu100%的问题。jstack可以定位到线程堆栈，根据堆栈信息我们可以定位到具体代码，所以它在JVM性能调优中使用得非常多。</p>
+<blockquote>
+<p>jstack主要用于生成java虚拟机当前时刻的线程快照。线程快照是当前java虚拟机内每一条线程正在执行的方法堆栈的集合，生成线程快照的主要目的是定位线程出现长时间停顿的原因，
+如线程间死锁、死循环、请求外部资源导致的长时间等待等。</p>
+</blockquote>
+<table>
+<thead>
+<tr>
+<th>命令</th>
+<th>含义</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>jstack pid</td>
+<td>打印出所有的线程，包括用户自己启动的线程和<code>JVM</code>后台线程</td>
+</tr>
+<tr>
+<td>jstack 13324 &gt;1.txt</td>
+<td>将13324进程中线程信息写入到<code>1.txt</code>文件中</td>
+</tr>
+<tr>
+<td>jstack 21711｜grep 54ee</td>
+<td>在进程21711中查找线程ID为54ee(16进制)的信息</td>
+</tr>
+<tr>
+<td>jstack -l pid</td>
+<td>除了堆栈信息外<code>-l</code>参数会显示线程锁的附加信息</td>
+</tr>
+</tbody>
+</table>
+<p>除了可以使用jstack打印栈的信息，在java层面也可以使用<code>Thread.getAllStackTraces()</code>方法获取堆栈信息。</p>
+<h4 id="jcmd">jcmd</h4>
+<p>在JDK1.7之后，新增了一个命令行工具jcmd。</p>
+<p>它是一个多功能的工具，可以实现前面除了jstat之外的所有功能。例如，导出dump文件、查看线程信息、导出线程信息、执行GC，JVM运行时间等。</p>
+<p>jcmd拥有jmap的大部分功能，并且在官方网站上也推荐使用jcmd代替jmap。</p>
+<table>
+<thead>
+<tr>
+<th>命令</th>
+<th>含义</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>jcmd -l</td>
+<td>列出所有<code>JVM</code>的进程</td>
+</tr>
+<tr>
+<td>jcmd pid help</td>
+<td>针对指定进程罗列出可执行的命令</td>
+</tr>
+<tr>
+<td>jcmd pid &lt;具体命令&gt;</td>
+<td>显示指定进程的指令命令的数据</td>
+</tr>
+</tbody>
+</table>
+<h3 id="gui分析工具">GUI分析工具</h3>
+<h4 id="jconsole">jconsole</h4>
+<p>JConsole 是一个内置 Java 性能分析器，可以从命令行（直接输入jconsole）或在 GUI shell （jdk\bin下打开）中运行。</p>
+<p>它用于对JVM中内存，线程和类等的监控。这款工具的好处在于，占用系统资源少，而且结合Jstat，可以有效监控到java内存的变动情况，以及引起变动的原因。在项目追踪内存泄露问题时，很实用。</p>
+<p><img alt="常见故障排查及程序配置-002" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-002.png"></p>
+<p><img alt="常见故障排查及程序配置-001" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-001.png"></p>
+<p><img alt="常见故障排查及程序配置-003" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-003.png"></p>
+<h4 id="visual-vm">visual vm</h4>
+<p>visual vm 是一个功能强大的多合一故障诊断和性能监控的可视化工具。它集成了多个JDK命令行工具，使用visual vm可用于显示虚拟机进程及进程的配置和环境信息，监视应用程序的CPU、GC、堆、方法区及线程的信息等，甚至代替jconsole。</p>
+<p>在JDK7，visual vm便作为JDK的一部分发布，在JDK的bin目录下，即：它完全免费。此外，visual vm也可以作为独立软件进行安装。</p>
+<p>主要功能：</p>
+<ul>
+<li>生成读取dump文件</li>
+<li>查看JVM参数和系统属性</li>
+<li>查看运行中虚拟机进程</li>
+<li>生成读取线程快照</li>
+<li>程序资源的实时监控</li>
+</ul>
+<p>visual vm 支持插件扩展，可以在visual vm上安装插件，也可以将visual vm安装在idea上：</p>
+<p><img alt="常见故障排查及程序配置-006" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-006.png"></p>
+<p><img alt="常见故障排查及程序配置-007" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-007.png"></p>
+<p>visual vm可以生成dump文件，生成的dump文件是临时的，如果想要保留该文件需要右键另存为即可：</p>
+<p><img alt="常见故障排查及程序配置-004" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-004.png"></p>
+<p><img alt="常见故障排查及程序配置-005" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-005.png"></p>
+<p>如果堆文件数据较大，排查起来很困难，可以使用OQL语句进行筛选。</p>
+<blockquote>
+<p>OQL:全称，Object Query Language 类似于SQL查询的一种语言，OQL使用SQL语法，可以在堆中进行对象的筛选。</p>
+<p>基本语法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">select &lt;JavaScript expression to select&gt; 
+</span></span><span class="line"><span class="cl">[ from (instanceof) &lt;class name&gt; &lt;identifier&gt;
+</span></span><span class="line"><span class="cl">( where &lt;JavaScript boolean expression to filter&gt; ) ]
+</span></span></code></pre></div><p>1.class name是java类的完全限定名
+2.instanceof表示也查询某一个类的子类
+3.from和where子句都是可选的
+4.可以使用obj.field_name语法访问Java字段</p>
+<p>例如</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">-- 查询长度大于等于100的字符串
+</span></span><span class="line"><span class="cl">select s from java.lang.String s where s.value.length &gt;= 100
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 显示所有File对象的文件路径 
+</span></span><span class="line"><span class="cl">select file.path.value.toString() from java.io.File file
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 显示由给定id字符串标识的Class的实例
+</span></span><span class="line"><span class="cl">select o from instanceof 0x741012748 o
+</span></span></code></pre></div></blockquote>
+<p>visual vm也可以将两个dump文件进行比较：</p>
+<p><img alt="常见故障排查及程序配置-008" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-008.png"></p>
+<p>visual vm不但可以生成堆的dump文件，也可以对线程dump：</p>
+<p><img alt="常见故障排查及程序配置-009" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-009.png"></p>
+<h4 id="eclipse-mat">eclipse MAT</h4>
+<p>MAT全称，Memory Analyzer Tool 是一款功能强大的Java堆内存分析器。可以用于查找内存泄漏以及查看内存消耗情况。</p>
+<p>MAT是eclipse开发的，不仅可以单独使用，还可以作为插件嵌入在eclipse中使用。是一款免费的性能分析工具，使用起来很方便。</p>
+<p>MAT的主要功能就是分析dump文件。分析dump最终目的是为了找出内存泄漏的疑点，防止内存泄漏。</p>
+<p>JVM内存包含信息：</p>
+<ul>
+<li>所有对象信息，包括对象实例、成员变量、存储于栈中的基本数据类型和存储于堆中的其他对象的引用值；</li>
+<li>所有的类信息，包括classloader、类名称、父类的信息、静态变量等；</li>
+<li>GCRoot到所有的这些对象的引用路径;</li>
+<li>线程信息，包括线程的调用栈及线程的局部变量;</li>
+</ul>
+<p>常见获取dump文件方式：</p>
+<ul>
+<li>通过jmap或jcmd命令行方式获取；</li>
+<li>通过配置JVM参数&rdquo;-XX:+HeapDumpOnOutOfMemoryError&quot;或&quot;-XX:+HeapDumpBeforeFullGC&quot;</li>
+<li>使用第三方工具生成dump文件，如：visual vm</li>
+</ul>
+<hr>
+<p><strong>MAT介绍</strong></p>
+<p>导入dump文件：</p>
+<p>在生成可疑泄漏报告后，会在对应的堆转储文件目录下生成一个zip文件。</p>
+<p><img alt="常见故障排查及程序配置-010" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-010.png"></p>
+<p><img alt="常见故障排查及程序配置-011" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-011.png"></p>
+<p><img alt="常见故障排查及程序配置-012" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-012.png"></p>
+<p><img alt="常见故障排查及程序配置-013" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-013.png"></p>
+<p><img alt="常见故障排查及程序配置-016" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-016.png"></p>
+<p>MAT最主要的功能是分析dump文件，其中比较重要的功能就是histogram(直方图)和dominator tree(支配树)</p>
+<hr>
+<p><strong>直方图</strong></p>
+<p><img alt="常见故障排查及程序配置-015" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-015.png"></p>
+<ul>
+<li>浅堆：一个对象结构所占用的大小，即对象头+实例数据+对齐填充，不包括内部引用对象大小；</li>
+<li>深堆：一个对象被 GC 回收后，可以真实释放的内存大小；</li>
+<li>对象的实际大小：一个对象所能触及的所有对象的浅堆大小之和；</li>
+</ul>
+<p><img alt="常见故障排查及程序配置-017" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-017.png"></p>
+<p>如上图所示：（浅堆&lt;= 深堆 &lt;= 实际大小）</p>
+<ul>
+<li>Object2浅堆大小：为Object2本身；</li>
+<li>Object2深堆大小：Object2本身加上Object6；</li>
+<li>Object2实际大小：Object2本身加上Object6加上Object5；</li>
+</ul>
+<p><img alt="常见故障排查及程序配置-014" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-014.png"></p>
+<hr>
+<p><strong>支配树对象图</strong></p>
+<p><img alt="常见故障排查及程序配置-018" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-018.png"></p>
+<p>支配树概念源自图论。它体现了对象实例之间的支配关系。在对象的引用图中，所有指向对象B的路径都要经过对象A，则认为对象A支配对象B。如果对象A是离对象B最近的一个支配对象，则认为对象A为对象B的直接支配者。</p>
+<p>支配树是基于对象间的引用图建立的，它有以下性质：</p>
+<ul>
+<li>对象A的子树，即所有被对象A支配的对象集合，表示对象A的保留集，即深堆；</li>
+<li>如果对象A支配对象B，那么对象A直接支配者也支配对象B；</li>
+<li>支配树的边与对象引用图的边不相对应；</li>
+</ul>
+<p>分配树能直观的体现对象能否被回收的情况，如图所示，左为对象的引用图，右为对象的支配图。</p>
+<ul>
+<li>C与E的关系为，C支配E，C是E的直接支配者，G和E为C的保留集；</li>
+<li>C与H不是支配关系，因为H被F引用；</li>
+</ul>
+<p><img alt="常见故障排查及程序配置-019" src="/iblog/posts/annex/images/essays/%E5%B8%B8%E8%A7%81%E6%95%85%E9%9A%9C%E6%8E%92%E6%9F%A5%E5%8F%8A%E7%A8%8B%E5%BA%8F%E9%85%8D%E7%BD%AE-019.png"></p>
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+    
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+        <a id="content_display" class="content_display">
+            <svg t="1688606941910" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="57753" width="18" height="18"><path d="M192 448c10.9 0 21.8-4.2 30.2-12.5L497 160.8c5.4-5.4 11.8-6.2 15.1-6.2 3.3 0 9.6 0.8 15.1 6.2l274.7 274.7c16.7 16.7 43.7 16.7 60.3 0 16.7-16.7 16.7-43.7 0-60.3L587.4 100.4c-41.6-41.6-109.3-41.6-150.9 0L161.8 375.2c-16.7 16.7-16.7 43.7 0 60.3 8.4 8.3 19.3 12.5 30.2 12.5zM801.8 588.5L527.1 863.2c-5.4 5.4-11.8 6.2-15.1 6.2-3.3 0-9.7-0.8-15.1-6.2L222.2 588.5c-16.7-16.7-43.7-16.7-60.3 0-16.7 16.7-16.7 43.7 0 60.3l274.8 274.8c20.8 20.8 48.1 31.2 75.4 31.2 27.3 0 54.6-10.4 75.4-31.2l274.7-274.8c16.7-16.7 16.7-43.7 0-60.3-16.7-16.7-43.7-16.7-60.4 0z" fill="#424242" p-id="57754"></path></svg>
+        </a>
+        <a id="content_hidden" class="content_hidden">
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+                mixColor: '#f7f7f7', 
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+                buttonColorDark: '#212121', 
+                buttonColorLight: '#f7f7f7', 
+                saveInCookies: false, 
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+
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diff --git a/docs/posts/codeguide/java-always-problems/index.html b/docs/posts/codeguide/java-always-problems/index.html
new file mode 100644
index 00000000..705120b0
--- /dev/null
+++ b/docs/posts/codeguide/java-always-problems/index.html
@@ -0,0 +1,1742 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java程序常见问题 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="CPU使用过高 一般在生产环境排查程序故障，都会查看日志什么的，但是有些故障日志是看不出来的，就比如：CPU使用过高。 那应该怎么办呢？我们需要结合linux命令和" />
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+    
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+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/normalize.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/animate.min.css" />
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+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/toc.css" />
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+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cpu%e4%bd%bf%e7%94%a8%e8%bf%87%e9%ab%98">
+                    CPU使用过高
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e6%9f%a5%e8%bf%87%e7%a8%8b">
+                    排查过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%ad%bb%e9%94%81">
+                    死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e6%9f%a5%e8%bf%87%e7%a8%8b-1">
+                    排查过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-1">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e8%b5%84%e6%ba%90%e6%9c%89%e5%ba%8f%e5%88%86%e9%85%8d%e6%b3%95%e9%81%bf%e5%85%8d%e6%ad%bb%e9%94%81">
+                    使用资源有序分配法避免死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e9%93%b6%e8%a1%8c%e5%ae%b6%e7%ae%97%e6%b3%95%e9%81%bf%e5%85%8d%e6%ad%bb%e9%94%81">
+                    使用银行家算法避免死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8-trylock-%e8%bf%9b%e8%a1%8c%e8%b6%85%e6%97%b6%e9%94%81%e5%ae%9a">
+                    使用 tryLock 进行超时锁定
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%85%e5%ad%98%e6%b3%84%e9%9c%b2">
+                    内存泄露
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e6%9f%a5%e8%bf%87%e7%a8%8b-2">
+                    排查过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-2">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jvm%e5%8f%82%e6%95%b0%e8%b0%83%e4%bc%98">
+                    JVM参数调优
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e4%b8%8a%e6%8e%a5%e5%8f%a3%e6%85%a2">
+                    线上接口慢
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9a%e4%bd%8d%e9%97%ae%e9%a2%98">
+                    定位问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-3">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e6%8d%ae%e5%ba%93%e6%85%a2sql">
+                    数据库慢sql
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b0%83%e7%94%a8%e7%ac%ac%e4%b8%89%e6%96%b9%e6%8e%a5%e5%8f%a3%e6%85%a2">
+                    调用第三方接口慢
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ad%e9%97%b4%e4%bb%b6%e6%85%a2">
+                    中间件慢
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%a8%8b%e5%ba%8f%e9%80%bb%e8%be%91%e6%85%a2">
+                    程序逻辑慢
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9e%b6%e6%9e%84%e4%bc%98%e5%8c%96">
+                    架构优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#transactional">
+                    @Transactional
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
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+                        <h2 id="post_single_title">Java程序常见问题</h2>
+                        <span id="post_page_title_date" class="date">2024.05.28</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
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+                    <div class="post_content markdown"><h2 id="cpu使用过高">CPU使用过高</h2>
+<p>一般在生产环境排查程序故障，都会查看日志什么的，但是有些故障日志是看不出来的，就比如：CPU使用过高。
+那应该怎么办呢？我们需要结合linux命令和JDK相关命令来排查程序故障。</p>
+<h3 id="排查过程">排查过程</h3>
+<ol>
+<li>首先使用top命令，找出CPU占比最高的Java进程，然后进一步定位后台程序，如果发现使用过高的进程ID，记录下来方便排查。</li>
+<li>定位到具体的线程，使用<code>ps -mp 进程ID -o THREAD,tid,time</code>命令可以找到有问题的线程ID。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">ps -mp 进程ID -o THREAD,tid,time 说明：
+</span></span><span class="line"><span class="cl">-m：显示所有线程；
+</span></span><span class="line"><span class="cl">-p：pid进程使用CPU的时间；
+</span></span><span class="line"><span class="cl">-o：该参数后是用户自定义参数
+</span></span></code></pre></div></li>
+<li>获取到线程ID后，需要将线程ID转化为16进制格式，如果有英文要小写格式；可以用命令<code>printf &quot;%x\n&quot; 线程ID</code>，当然也可以使用工具从10进制转16进制。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">printf &#34;%x\n&#34; 16
+</span></span></code></pre></div></li>
+<li>线程ID转成16进制后，执行最后一个命令：<code>jstack 进程ID | grep 16进制线程ID -A50</code>或者dump下来，<code>jstack pid &gt; pid.log</code>，就能看到有问题的代码。</li>
+</ol>
+<h3 id="解决方案">解决方案</h3>
+<ol>
+<li>将dump文件下载下来，上传到第三方网站，如：https://fastthread.io/ 进行分析，然后找到解决方案；</li>
+<li>确定是否新部署或有新变更： 首先需要确认是否在最近进行了新的部署或有其他相关的变更，例如代码更新、配置修改等。这些变更可能导致应用出现性能问题，特别是在高负载情况下；</li>
+<li>确定是否可重现问题：尝试重现CPU飙高的问题，可以通过模拟实际场景、使用压力测试工具或者观察日志等方式来尽量还原问题。如果能够确定问题的可重现性，将有助于后续的排查和分析；</li>
+<li>确定是否为GC造成：Java应用中频繁进行垃圾回收可能会导致CPU飙高。可以通过查看GC日志、分析堆内存使用情况以及GC时间等指标来确认是否为GC引起了性能问题；</li>
+<li>确定是否线程阻塞：线程阻塞也是常见的导致CPU飙高的原因之一。可以通过线程监控工具，如JMC、VisualVM，来检查是否存在长时间阻塞的线程，并分析造成线程阻塞的原因；</li>
+</ol>
+<h2 id="死锁">死锁</h2>
+<p>死锁是指两个或多个线程在执行过程中，由于竞争资源或者互相等待释放资源而造成的一种僵局，使得所有参与的线程无法继续执行。
+举个例子，当线程A持有锁a并尝试获取锁b，线程B持有锁b并尝试获取锁a时，就会出现死锁。简单来说，死锁问题的产生是由两个或者以上线程并行执行的时候，争夺资源而互相等待造成的。</p>
+<h3 id="排查过程-1">排查过程</h3>
+<p>死锁经常表现为程序的停顿，或者不再响应用户的请求。从操作系统上观察，对应进程的CPU占用率为零，很快会从top的输出中消失。模拟死锁代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;lockA&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;lockB&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadHolderLock</span><span class="p">(</span><span class="n">lockA</span><span class="p">,</span><span class="n">lockB</span><span class="p">),</span><span class="s">&#34;线程AAA&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadHolderLock</span><span class="p">(</span><span class="n">lockB</span><span class="p">,</span><span class="n">lockA</span><span class="p">),</span><span class="s">&#34;线程BBB&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ThreadHolderLock</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Runnable</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ThreadHolderLock</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lockA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lockA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lockB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lockB</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lockA</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 持有锁 &#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockA</span><span class="o">+</span><span class="s">&#34;, 尝试获得&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockB</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lockB</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 持有锁 &#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockB</span><span class="o">+</span><span class="s">&#34;, 尝试获得&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockA</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><ol>
+<li>使用<code>jps -l</code>命令找到程序进程；</li>
+<li>使用<code>jstack pid</code>命令打印堆栈信息；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Found one Java-level deadlock:
+</span></span><span class="line"><span class="cl">=============================
+</span></span><span class="line"><span class="cl">&#34;线程BBB&#34;:
+</span></span><span class="line"><span class="cl">  waiting to lock monitor 0x00007feb0d80b018 (object 0x000000076af2d588, a java.lang.String),
+</span></span><span class="line"><span class="cl">  which is held by &#34;线程AAA&#34;
+</span></span><span class="line"><span class="cl">&#34;线程AAA&#34;:
+</span></span><span class="line"><span class="cl">  waiting to lock monitor 0x00007feb0d80d8a8 (object 0x000000076af2d5c0, a java.lang.String),
+</span></span><span class="line"><span class="cl">  which is held by &#34;线程BBB&#34;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Java stack information for the threads listed above:
+</span></span><span class="line"><span class="cl">===================================================
+</span></span><span class="line"><span class="cl">&#34;线程BBB&#34;:
+</span></span><span class="line"><span class="cl">    at com.github.springcloud.service.ThreadHolderLock.run(MainTest.java:35)
+</span></span><span class="line"><span class="cl">    - waiting to lock &lt;0x000000076af2d588&gt; (a java.lang.String)
+</span></span><span class="line"><span class="cl">    - locked &lt;0x000000076af2d5c0&gt; (a java.lang.String)
+</span></span><span class="line"><span class="cl">    at java.lang.Thread.run(Thread.java:748)
+</span></span><span class="line"><span class="cl">&#34;线程AAA&#34;:
+</span></span><span class="line"><span class="cl">    at com.github.springcloud.service.ThreadHolderLock.run(MainTest.java:35)
+</span></span><span class="line"><span class="cl">    - waiting to lock &lt;0x000000076af2d5c0&gt; (a java.lang.String)
+</span></span><span class="line"><span class="cl">    - locked &lt;0x000000076af2d588&gt; (a java.lang.String)
+</span></span><span class="line"><span class="cl">    at java.lang.Thread.run(Thread.java:748)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Found 1 deadlock.
+</span></span></code></pre></div></li>
+</ol>
+<h3 id="解决方案-1">解决方案</h3>
+<h4 id="使用资源有序分配法避免死锁">使用资源有序分配法避免死锁</h4>
+<p>想要如何避免死锁，就要弄清楚死锁出现的原因，造成死锁必须达成的4个条件：</p>
+<ul>
+<li>互斥条件：一个资源每次只能被一个线程使用。例如，如果线程 A 已经持有的资源，不能再同时被线程 B 持有，如果线程 B 请求获取线程 A 已经占用的资源，那线程 B 只能等待，直到线程 A 释放了资源。</li>
+<li>请求与保持条件：一个线程因请求资源而阻塞时，对已获得的资源保持不放。例如，当线程 A 已经持有了资源 1，又想申请资源 2，而资源 2 已经被线程 C 持有了，所以线程 A 就会处于等待状态，但是线程 A 在等待资源 2 的同时并不会释放自己已经持有的资源 1。</li>
+<li>不剥夺条件：线程已获得的资源，在未使用完之前，不能强行剥夺。例如，当线程A已经持有了资源 ，在自己使用完之前不能被其他线程获取，线程 B 如果也想使用此资源，则只能在线程 A 使用完并释放后才能获取。</li>
+<li>循环等待条件：若干线程之间形成一种头尾相接的循环等待资源关系。比如，线程 A 已经持有资源 2，而想请求资源 1， 线程 B 已经获取了资源 1，而想请求资源 2，这就形成资源请求等待的环。</li>
+</ul>
+<p>避免死锁的产生就只需要破环其中一个条件就可以，最常见的并且可行的就是使用资源有序分配法，来破循环等待条件。
+资源有序分配法指的是，线程 A 和 线程 B 获取资源的顺序要一样，当线程 A 先尝试获取资源 A，然后尝试获取资源 B 的时候，线程 B 同样也是先尝试获取资源 A，然后尝试获取资源 B。也就是说，线程 A 和 线程 B 总是以相同的顺序申请自己想要的资源。
+给资源分配一个全局的唯一编号，进程必须按资源编号的顺序请求资源。这种方法可以避免循环等待，从而防止死锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Resource</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Resource</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Process</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="w"> </span><span class="n">resources</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Process</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">resources</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">resources</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquireResources</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 模拟处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">releaseResources</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">acquireResources</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Resource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired Resource &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">resource</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">releaseResources</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Resource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; released Resource &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">resource</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ResourceOrderingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource1</span><span class="p">,</span><span class="w"> </span><span class="n">resource2</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource2</span><span class="p">,</span><span class="w"> </span><span class="n">resource3</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource3</span><span class="p">,</span><span class="w"> </span><span class="n">resource1</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process3</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用银行家算法避免死锁">使用银行家算法避免死锁</h4>
+<p><img alt="银行家算法" src="/iblog/posts/annex/images/essays/%E9%93%B6%E8%A1%8C%E5%AE%B6%E7%AE%97%E6%B3%95.png"></p>
+<p>银行家算法：一个避免死锁的著名算法，是由艾兹格·迪杰斯特拉在1965年为T.H.E系统设计的一种避免死锁产生的算法。它以银行借贷系统的分配策略为基础，判断并保证系统的安全运行。</p>
+<p>在银行中，客户申请贷款的数量是有限的，每个客户在第一次申请贷款时要声明完成该项目所需的最大资金量，在满足所有贷款要求时，客户应及时归还。银行家在客户申请的贷款数量不超过自己拥有的最大值时，都应尽量满足客户的需要。通过判断借贷是否安全，然后决定借不借。
+举例，现有公司B、公司A、公司T，想要从银行分别贷款70亿、40亿、50亿，假设银行只有100亿供放贷，如果借不到企业最大需求的钱，钱将不会归还，怎么才能合理的放贷？</p>
+<table>
+<thead>
+<tr>
+<th>公司</th>
+<th>最大需求</th>
+<th>已借走</th>
+<th>最多还借</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>B</td>
+<td>70</td>
+<td>20</td>
+<td>50</td>
+</tr>
+<tr>
+<td>A</td>
+<td>40</td>
+<td>10</td>
+<td>30</td>
+</tr>
+<tr>
+<td>T</td>
+<td>50</td>
+<td>30</td>
+<td>20</td>
+</tr>
+</tbody>
+</table>
+<p>此时公司B、A、T已经从银行借走60亿，银行还剩40亿。此时银行可放贷金额组合：</p>
+<ul>
+<li>借给公司B10亿、公司A10亿、公司T20亿，等待公司T还钱再将10亿借给公司A，等待公司A还钱，再将钱借给公司B；</li>
+<li>借给公司T20亿，等公司T还钱再将钱借给公司A，等待公司A还钱再将钱借给公司B；</li>
+<li>借给公司A10亿，等待公司A还钱再将钱借给公司T，公司T还钱再将钱借给公司B；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Banker</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="p">;</span><span class="w">  </span><span class="c1">// 系统可用资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="p">;</span><span class="w">  </span><span class="c1">// 每个进程的最大资源需求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">allocation</span><span class="p">;</span><span class="w"> </span><span class="c1">// 每个进程当前已分配的资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">need</span><span class="p">;</span><span class="w">      </span><span class="c1">// 每个进程剩余的资源需求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Banker</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">available</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">maximum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">numProcesses</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">numResources</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">allocation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">numProcesses</span><span class="o">][</span><span class="n">numResources</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">need</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">numProcesses</span><span class="o">][</span><span class="n">numResources</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">numProcesses</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">numResources</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">need</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// 初始时，Need等于Maximum</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 请求资源的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">requestResources</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isRequestValid</span><span class="p">(</span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="n">request</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 请求不合法，拒绝请求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 试探性分配</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">allocation</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 安全性检查</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">safe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">isSafeState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">safe</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果不安全，恢复试探性分配前的状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">allocation</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">safe</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isRequestValid</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">request</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 请求超出需求或可用资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isSafeState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">work</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">finish</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">allocation</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">found</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">allocation</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">finish</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">canProceed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">work</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">need</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">work</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">canProceed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">canProceed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">work</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">work</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">allocation</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">finish</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">found</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">found</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">finish</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">f</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 存在未完成的进程，系统不安全</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w"> </span><span class="c1">// 所有进程都完成，系统安全</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>调用示例</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BankerExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Banker</span><span class="w"> </span><span class="n">banker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Banker</span><span class="p">(</span><span class="n">available</span><span class="p">,</span><span class="w"> </span><span class="n">maximum</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">request1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 1 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">request2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 2 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">request3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 3 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用-trylock-进行超时锁定">使用 tryLock 进行超时锁定</h4>
+<p>使用 <code>java.util.concurrent.locks.ReentrantLock</code> 的 <code>tryLock</code>方法可以尝试获取锁，并设置超时时间，避免长时间等待造成的死锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kn">import</span><span class="w"> </span><span class="nn">java.util.concurrent.locks.Lock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kn">import</span><span class="w"> </span><span class="nn">java.util.concurrent.locks.ReentrantLock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kn">import</span><span class="w"> </span><span class="nn">java.util.concurrent.TimeUnit</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Process</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Process</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock1</span><span class="p">.</span><span class="na">tryLock</span><span class="p">(</span><span class="n">50</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock2</span><span class="p">.</span><span class="na">tryLock</span><span class="p">(</span><span class="n">50</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired both locks&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="c1">// 模拟处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">lock2</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">lock1</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 等待一段时间再重试</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">50</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TryLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">,</span><span class="w"> </span><span class="n">lock1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="内存泄露">内存泄露</h2>
+<p>Java虚拟机是使用引用计数法和可达性分析来判断对象是否可回收，本质是判断一个对象是否还被引用，如果没有引用则回收。
+内存泄露是指，程序中己动态分配的堆内存由于某种原因程序未释放或无法释放，造成系统内存的浪费，导致程序运行速度减慢甚至系统崩溃等严重后果。
+简单来说，就是应该被垃圾回收的对象没有回收掉，导致占用的内存越来越多，最终导致内存溢出。</p>
+<p>内存泄露主要原因：</p>
+<ul>
+<li>在内存中加载过大的数据，例如从数据库取出过多数据；</li>
+<li>资源未关闭造成的内存泄漏；</li>
+<li>变量不合理的作用域，使用完毕，如果没有及时的赋值为null，则会造成内存泄露；</li>
+<li>长生命周期的对象中引用短生命周期对象，很可能会出现内存泄露；</li>
+</ul>
+<p>举个例子，创建的连接不再使用时，需要调用 close 方法关闭连接，只有连接被关闭后，GC 才会回收对应的对象（Connection，Statement，ResultSet，Session）。忘记关闭这些资源会导致持续占有内存，无法被 GC 回收。
+这样就会导致内存泄露，最终导致内存溢出。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MemoryLeak</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">try</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Class</span><span class="p">.</span><span class="na">forName</span><span class="p">(</span><span class="s">&#34;com.mysql.jdbc.Driver&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="n">DriverManager</span><span class="p">.</span><span class="na">getConnection</span><span class="p">(</span><span class="s">&#34;url&#34;</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Statement</span><span class="w"> </span><span class="n">stmt</span><span class="w"> </span><span class="o">=</span><span class="n">conn</span><span class="p">.</span><span class="na">createStatement</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">ResultSet</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">=</span><span class="n">stmt</span><span class="p">.</span><span class="na">executeQuery</span><span class="p">(</span><span class="s">&#34;....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">){</span><span class="c1">//异常日志</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 1．关闭结果集 Statement</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 2．关闭声明的对象 ResultSet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 3．关闭连接 Connection</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="排查过程-2">排查过程</h3>
+<p>根据运维之前收集到的内存数据、GC 日志尝试判断哪里出现了问题。
+结果发现老年代的内存使用就算是发生 GC 也一直居高不下，而且随着时间推移也越来越高。</p>
+<p><img alt="内存泄漏问题-01" src="/iblog/posts/annex/images/essays/%E5%86%85%E5%AD%98%E6%B3%84%E6%BC%8F%E9%97%AE%E9%A2%98-01.png"></p>
+<p>使用<code>jstat -gc &lt;vmid&gt;</code> 查看GC垃圾回收统计信息，看Full GC后堆空间使用内存还持续增长，且有增长到Xmx设定值的趋势，基本可以肯定存在内存泄露。
+如果当前完全垃圾回收后内存增长到一个值之后，又能回落，总体上处于一个动态平衡，那么内存泄漏基本可以排除；也可以隔断时间抽取老年代占用内存情况，如果老年代占用情况持续上升也很有可能存在内存泄露的情况。</p>
+<h3 id="解决方案-2">解决方案</h3>
+<ol>
+<li>内存泄漏的主要表象就是内存不足，所以首先要看一下JVM启动参数中内存空间分配是否过小，如果是这种问题调整该参数即可；</li>
+<li>确定是否新部署或有新变更，首先需要确认是否在最近进行了新的部署或有其他相关的变更，例如代码更新、配置修改等。这些变更可能导致应用出现性能问题，特别是在高负载情况下；</li>
+<li>内存泄漏解决方案，最经典的就是用MAT工具分析dump文件，但如果dump文件巨大就不建议这样，可以使用其他方案，例如：重启、本地复现、<code>jmap -histo:live &lt;pid&gt;</code>在线进行分析等其他方案解决。</li>
+</ol>
+<p>使用MAT定位内存泄漏思路：</p>
+<ol>
+<li>打开MAT中histogram，找到堆内存中占用最大的对象，内存泄漏很有可能就是由大对象导致的；
+<img alt="MAT-01" src="/iblog/posts/annex/images/essays/MAT-01.png"></li>
+<li>由大对象找被哪些线程引用，查看内存占用最大的线程；
+<img alt="MAT-02" src="/iblog/posts/annex/images/essays/MAT-02.png">
+<img alt="MAT-03" src="/iblog/posts/annex/images/essays/MAT-03.png"></li>
+<li>从线程中的堆栈信息找到项目中自定义的包和对象，从而可定位到具体的代码；
+<img alt="MAT-04" src="/iblog/posts/annex/images/essays/MAT-04.png">
+<img alt="MAT-05" src="/iblog/posts/annex/images/essays/MAT-05.png"></li>
+</ol>
+<h2 id="jvm参数调优">JVM参数调优</h2>
+<p>JVM优化是到最后不得已才采用的手段，对JVM内存的系统级的调优主要的目的是减少GC的频率和Full GC的次数。
+JVM参数说明：https://www.oracle.com/java/technologies/javase/vmoptions-jsp.html</p>
+<p>理想的情况下，一个Java程序使用JVM的默认设置也可以运行得很好，所以一般来说，没有必要设置任何JVM参数。然而，由于一些性能问题，我们需要设置合理的JVM参数。</p>
+<p>可以通过<code>java -XX:+PrintFlagsInitial</code> 命令查看JVM所有参数。</p>
+<p>常用参数：</p>
+<table>
+<thead>
+<tr>
+<th>参数</th>
+<th>含义</th>
+<th>描述</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>-Xms</td>
+<td>堆初始值</td>
+<td>Xmx和Xms设置为老年代存活对象的3-4倍，即FullGC之后的老年代内存占用的3-4倍</td>
+</tr>
+<tr>
+<td>-Xmx</td>
+<td>堆最大值</td>
+<td>为了防止自动扩容降低性能，建议将-Xms和-Xmx的值设置为相同值</td>
+</tr>
+<tr>
+<td>-XX:MaxHeapFreeRatio</td>
+<td>最大堆内存使用率</td>
+<td>默认70，当超过该比例会进行扩容堆，Xms=Xmx时该参数无效</td>
+</tr>
+<tr>
+<td>-XX:MinHeapFreeRatio</td>
+<td>最小堆内存使用率</td>
+<td>默认40，当低于该比例会缩减堆，Xms=Xmx时该参数无效</td>
+</tr>
+<tr>
+<td>-Xmn</td>
+<td>年轻代内存最大值</td>
+<td>年轻代设置的越大，老年代区域就会减少。一般不允许年轻代比老年代还大，因为要考虑GC时最坏情况，所有对象都晋升到老年代。建议设置为老年代存活对象的1-1.5倍，最大可以设置为-Xmx/2 。考虑性能，一般会通过参数 -XX:NewSize 设置年轻代初始大小。如果知道了年轻代初始分配的对象大小，可以节省新生代自动扩展的消耗。</td>
+</tr>
+<tr>
+<td>-XX:SurvivorRatio</td>
+<td>年轻代中两个Survivor区和Eden区大小比率</td>
+<td>例如： -XX:SurvivorRatio=10 表示伊甸园区是幸存者其中一个区大小的10倍，所以,伊甸园区占新生代大小的10/12, 幸存区From和幸存区To 每个占新生代的1/12</td>
+</tr>
+<tr>
+<td>-XX:NewRatio</td>
+<td>年轻生代和老年代的比率</td>
+<td>例如：-XX:NewRatio=3 指定老年代/新生代为3/1. 老年代占堆大小的 3/4 ，新生代占 1/4 。如果针对新生代,同时定义绝对值和相对值,绝对值将起作用，建议将年轻代的大小为整个堆的3/8左右。</td>
+</tr>
+<tr>
+<td>-XX:+HeapDumpOnOutOfMemoryError</td>
+<td>让JVM在发生内存溢出时自动的生成堆内存快照</td>
+<td>可以通过-XX:HeapDumpPath=path参数将生成的快照放到指定路径下</td>
+</tr>
+<tr>
+<td>-XX:OnOutOfMemoryError</td>
+<td>当内存溢发生时可以执行一些指令</td>
+<td>比如发个E-mail通知管理员或者执行一些清理工作，执行脚本</td>
+</tr>
+<tr>
+<td>-XX:ThreadStackSize</td>
+<td>每个线程栈最大值</td>
+<td>栈设置太大，会导致线程创建减少，栈设置小，会导致深入不够，深度的递归会导致栈溢出，建议栈深度设置在3000-5000k。</td>
+</tr>
+<tr>
+<td>-XX:MetaspaceSize</td>
+<td>初始化的元空间大小</td>
+<td>如果元空间大小达到了这个值，就会触发Full GC为了避免频繁的Full GC，建议将- XX：MetaspaceSize设置较大值。如果释放了空间之后，元空间还是不足，那么就会自动增加MetaspaceSize的大小</td>
+</tr>
+<tr>
+<td>-XX:MaxMetaspaceSize</td>
+<td>元空间最大值</td>
+<td>默认情况下，元空间最大的大小是系统内存的大小，元空间一直扩大，虚拟机可能会消耗完所有的可用系统内存。</td>
+</tr>
+</tbody>
+</table>
+<p>示例参数：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"># 必备
+</span></span><span class="line"><span class="cl">-XX:+PrintGCDetails 
+</span></span><span class="line"><span class="cl">-XX:+PrintGCDateStamps 
+</span></span><span class="line"><span class="cl">-XX:+PrintTenuringDistribution 
+</span></span><span class="line"><span class="cl">-XX:+PrintHeapAtGC 
+</span></span><span class="line"><span class="cl">-XX:+PrintReferenceGC 
+</span></span><span class="line"><span class="cl">-XX:+PrintGCApplicationStoppedTime
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"># 可选
+</span></span><span class="line"><span class="cl">-XX:+PrintSafepointStatistics 
+</span></span><span class="line"><span class="cl">-XX:PrintSafepointStatisticsCount=1
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"># GC日志输出的文件路径
+</span></span><span class="line"><span class="cl">-Xloggc:/path/to/gc-%t.log
+</span></span><span class="line"><span class="cl"># 开启日志文件分割
+</span></span><span class="line"><span class="cl">-XX:+UseGCLogFileRotation 
+</span></span><span class="line"><span class="cl"># 最多分割几个文件，超过之后从头文件开始写
+</span></span><span class="line"><span class="cl">-XX:NumberOfGCLogFiles=14
+</span></span><span class="line"><span class="cl"># 每个文件上限大小，超过就触发分割
+</span></span><span class="line"><span class="cl">-XX:GCLogFileSize=100M
+</span></span></code></pre></div><p>何时调优：</p>
+<ol>
+<li>Full GC 次数频繁；</li>
+<li>GC 停顿时间过长；</li>
+<li>应用出现OutOfMemory 等内存异常；</li>
+<li>堆内存持续上涨达到设置的最大内存值；</li>
+</ol>
+<p>调优原则：</p>
+<ol>
+<li>多数导致GC问题的Java应用，都不是因为我们参数设置错误，而是代码问题；</li>
+<li>在实际使用中，分析GC情况优化代码比优化JVM参数更好；</li>
+<li>减少创建对象的数量、减少使用全局变量和大对象；</li>
+</ol>
+<p>调优思路：</p>
+<ol>
+<li>分析GC日志及dump文件，判断是否需要优化，确定瓶颈问题点。如果各项参数设置合理，系统没有超时日志出现，GC频率不高，GC耗时不高，那么没有必要进行GC优化，如果GC时间超过1-3秒，或者频繁GC，则必须优化；</li>
+<li>确定JVM调优目标。如果内存分配过大或过小，或者采用的GC收集器比较慢，则应该优先调整这些参数，并且先找1台或几台机器进行测试，然后比较优化过的机器和没有优化的机器的性能对比，并有针对性的做出最后选择；</li>
+<li>不断的分析和调整，直到找到合适的JVM参数配置；</li>
+</ol>
+<h2 id="线上接口慢">线上接口慢</h2>
+<h3 id="定位问题">定位问题</h3>
+<p>首先要定位是哪里慢，定位接口哪一个环节比较慢，性能瓶颈在哪里，可以使用应用性能监控工具(APM)定位问题。常见工具: skywalking、pinpoint、cat、zipkin。</p>
+<p>如果应用程序没有接入APM，可以在生产环境装一下arthas，利用trace接口方法和火焰图，大概能分析是那一块比较慢，定位能力稍微有点粗糙，亦可以利用程序中的告警日志定位问题。</p>
+<h3 id="解决方案-3">解决方案</h3>
+<p>如果已经定位到具体是哪里的问题了，那么就可以进行解决，如果是最新的功能引起的，那么最快的办法就是回退版本。
+以下是几种常见接口慢的情况。</p>
+<h4 id="数据库慢sql">数据库慢sql</h4>
+<p>如果是数据库sql慢，可以使用执行计划去分析一下，常见sql慢的几种情况：</p>
+<ul>
+<li>锁表；先把锁表的sqlkill一波，在分析具体原因；</li>
+<li>未加索引；添加索引，有可能会锁表，引发一系列问题，需要综合评估；</li>
+<li>索引失效；分析索引失效原因，如：索引列区分度（值大都相同）很低、索引列大量空值、对所索引列加方法转换等；</li>
+<li>小表驱动大表；在连接查询时尽量过滤数据，使用小表驱动大表，使笛卡尔积尽量小一些；</li>
+<li>sql太复杂；join超过3张表或者子查询比较多，建议拆分为多个sql，接口间相互调用；比如先从某个著接口查询某个表数据，然后关联字段作为条件从另一个表查询，进行内存拼接；</li>
+<li>返回的数据量数据太多；当超过数据库一定限制的时候返回大量数据就会很慢，可以使用分页多批次完成，针对访问量不多的接口可使用多线程批量查询；</li>
+<li>单表数据量太大；（mysql超500w较慢）如果单表数据量较大，考虑在数据库设计做文章，如：分片分库、利用es存储等；</li>
+</ul>
+<h4 id="调用第三方接口慢">调用第三方接口慢</h4>
+<ul>
+<li>设置合理的超时时间；调用第三方接口一定要设置合理的超时时间，在设置时一定要大于调用接口的平均相应时间；</li>
+<li>第三方接口大量超时；可以集成sentinel或hystrix限流熔断框架，防止第三方接口拖垮自己的接口（兜底逻辑）；</li>
+<li>事务型操作根据实际情况决定是否采用补偿机制（本地消息表）；比如新增、修改等操作要考虑对方接口是否支持幂等，防止超发；</li>
+<li>循环调用，改为单次批量调用，减少IO损耗；如：调用根据id查询单条数据的接口，可优化为批量查询接口；</li>
+<li>缓存查询结果；考虑当前查询结果是否能做缓存，如用户信息等短时间内不会变化的信息，根据业务形态来决定；</li>
+</ul>
+<h4 id="中间件慢">中间件慢</h4>
+<ul>
+<li>redis慢：是否有大key、热key，可接入hotkeys监控；针对热key可以使用本地缓存来抗，针对大key可以将其拆分，采用set结构的sismember等方法</li>
+<li>kafka：生产端慢：可以使用堵塞队列接收，批量丢消息；消费端慢：消费端慢会造成消息积压，可以扩分区、增加消费节点、增加消费线程，用数据机构接受批量写入库；</li>
+</ul>
+<h4 id="程序逻辑慢">程序逻辑慢</h4>
+<ul>
+<li>非法校验逻辑前置；避免无用数据穿透小号系统资源，减少无效调用；</li>
+<li>循环调用改为单次批量调用；在查询数据库或调用第三方接口，能批量就批量，数据在内存组装处理；</li>
+<li>同步调用改为异步调用；在接口没有相互依赖的关系的时候可以将其优化为异步查询；</li>
+<li>非核心逻辑剥离；将接口的大事务拆分为小事务，一些非核心逻辑可以异步处理，可以使用mq异步解耦；</li>
+<li>线程池合理设置参数；不要使用JDK默认参数，如果在高并发的情况下容易OOM，线程池满了以后要重写拒绝策略，考虑告警加数据持久化处理；</li>
+<li>锁合理设置；本地读写锁设计使用不合理，要控制锁的力度，尽量小一些；分布式锁合理使用防止热key；</li>
+<li>优化GC参数；考虑GC是否频繁，调整GC算法，新生代老年代比例，根据长时间观察可以设置出来；</li>
+<li>只打印必要日志；当并发量比较高的时候打印日志也会损耗性能，所以日志应加上开关能不打就不打；</li>
+</ul>
+<h4 id="架构优化">架构优化</h4>
+<ul>
+<li>高并发读逻辑走redis，尽可能不要穿透到DB；redis查询不到也不要查DB，可通过定时任务，MQ写入redis。尽量不要把风险给DB，DB如果挂了整个应用就用不了了；</li>
+<li>设计写逻辑数据，尽量异步、批量处理、分库分表提升写入性能；</li>
+<li>接口接入限流熔断兜底；</li>
+<li>接入监控告警；error日志告警、接口慢查询或者不可用或限流熔断告警、DB告警、中间件告警、应用系统告警等；</li>
+<li>接口需要加动态配置开关；能够快速切断流量或降级某些非核心服务调用；</li>
+<li>设计程序自愈能力；比如如果数据有问题，用配置好的程序逻辑自动去修复；</li>
+</ul>
+<h2 id="transactional">@Transactional</h2>
+<p><code>@Transactional</code>是开发过程中使用比较频繁的注解，但是使用不当也会导致事务失效甚至导致一些其他问题，下面是使用<code>@Transactional</code>遇到的几种问题。</p>
+<h3 id="transactional失效情况">@Transactional失效情况</h3>
+<ol>
+<li>如果某个方法是非public的，那么<code>@Transactional</code>就会失效。因为事务的底层是利用<code>cglib</code>代理实现，<code>cglib</code>是基于父子类来实现的，子类是不能重载父类的private方法，所以无法很好利用代理，这种情况下会导致@Transactional失效；</li>
+<li>使用的数据库引擎不支持事务。因为Spring的事务调用的也是数据库事务的API，如果数据库都不支持事务，那么<code>@Transactional</code>注解也就失效了；</li>
+<li>添加了<code>@Transactional</code>注解的方法不能在同一个类中调用，否则会使事务失效。这是因为Spring AOP通过代理来管理事务，自调用不会经过代理；</li>
+<li><code>@Transactional</code> 注解属性 <code>propagation</code> 设置错误，若是错误的配置以下三种 <code>propagation</code>，事务将不会发生回滚：
+<ul>
+<li><code>TransactionDefinition.PROPAGATION_SUPPORTS</code>：如果当前存在事务，则加入该事务；如果当前没有事务，则以非事务的方式继续运行。</li>
+<li><code>TransactionDefinition.PROPAGATION_NOT_SUPPORTED</code>：以非事务方式运行，如果当前存在事务，则把当前事务挂起。</li>
+<li><code>TransactionDefinition.PROPAGATION_NEVER</code>：以非事务方式运行，如果当前存在事务，则抛出异常。</li>
+</ul>
+</li>
+<li><code>@Transactional</code>注解属性<code>rollbackFor</code>设置错误，<code>rollbackFor</code>可以指定能够触发事务回滚的异常类型。默认情况下，Spring仅在抛出未检查异常（继承自<code>RuntimeException</code>）时回滚事务。对于受检异常（继承自 <code>Exception</code>），事务不会回滚，除非明确配置了<code>rollbackFor</code>属性；</li>
+<li>异常被捕获了，导致<code>@Transactional</code>失效。当事务方法中抛出一个异常后，应该是需要表示当前事务需要<code>rollback</code>，如果在事务方法中手动捕获了该异常，那么事务方法则会认为当前事务应该正常提交，此时就会出现事务方法中明明有报错信息表示当前事务需要回滚，但是事务方法认为是正常，出现了前后不一致，也是因为这样就会抛出<code>UnexpectedRollbackException</code>异常；</li>
+</ol>
+<p>我们在使用<code>@Transactional</code>时，要避免出现上述情况，以确保 <code>@Transactional</code> 注解正确生效，从而实现事务管理的可靠性和一致性。</p>
+<h3 id="transactional遇到锁">@Transactional遇到锁</h3>
+<p>看到这么一段代码，原来当Transactional碰到锁，有个大坑，觉得很有意思，于是便记录下来。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ServiceOne</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 设置一把可重入的公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Transactional</span><span class="p">(</span><span class="n">rollbackFor</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Exception</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Result</span><span class="w">  </span><span class="nf">func</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">seckillId</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">userId</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行数据库操作——查询商品库存数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果 库存数量 满足要求 执行数据库操作——减少库存数量——模拟卖出货物操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>func</code>方法是原子操作，所以使用事务，为了解决并发访问的问题，用<code>lock</code>把整个代码包裹了起来，这么使用锁和事务，是会发生超卖问题的。</p>
+<p>在使用MySQL数据库的可重复读隔离机制，如果是高并发的情况下，假设真的就有多个线程同时调用<code>func</code>方法。
+要保证一定不能出现超卖的情况，那么就需要事务的开启与提交能完整的包裹在<code>lock</code>与<code>unlock</code>之间。</p>
+<p>为什么要保证事务的开启与提交，完整的包裹在<code>lock</code>与<code>unlock</code>之间呢？</p>
+<p>举个例子，假设现在库存就只有一个了，这个时候 A，B 两个线程来请求下单。A 请求先拿到锁，然后查询出库存为一，可以下单，走了下单流程，把库存减为 0 了。
+但是由于 A 先执行了 <code>unlock</code> 操作，而未提交事务，先释放了锁。B 线程看到后马上就冲过来拿到了锁，并执行了查询库存的操作。
+这个时候 A 线程还没来得及提交事务，所以 B 读取到的库存还是 1，如果程序没有做好控制，也走了下单流程，此时就造成了超卖。</p>
+<p>那怎么保证事务的开启与提交，完整的包裹在<code>lock</code>与<code>unlock</code>之间呢？</p>
+<p>先来了解一下事务的启动和结束时机，这里直接说结论。
+事务的启动时机，在执行到它们之后的第一个操作数据库表的语句，事务才算是真正启动。在上述示例代码中第一个SQL是在加锁之后执行的，所以先加锁再开启事务。
+事务的提交是在目标方法执行之后。具体代码可以参考：<code>TransactionAspectSupport.invokeWithTransaction</code>方法，从其中可以看出，<code>invocation.proceedWithInvocation</code> 是在<code>commitTransactionAfterReturning</code>前面的。</p>
+<p>所以怎样保证呢？对于声明式事务，解决办法是把锁加在方法外面。如果一定需要加在里面，也可以使用编程式事务。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">seckillId</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">userId</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">DefaultTransactionDefinition</span><span class="w"> </span><span class="n">definition</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultTransactionDefinition</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">definition</span><span class="p">.</span><span class="na">setIsolationLevel</span><span class="p">(</span><span class="n">TransactionDefinition</span><span class="p">.</span><span class="na">ISOLATION_REPEATABLE_READ</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">TransactionStatus</span><span class="w"> </span><span class="n">status</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">transactionManager</span><span class="p">.</span><span class="na">getTransaction</span><span class="p">(</span><span class="n">definition</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="c1">// 执行数据库操作——查询商品库存数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="c1">// 如果 库存数量 满足要求 执行数据库操作——减少库存数量——模拟卖出货物操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">transactionManager</span><span class="p">.</span><span class="na">commit</span><span class="p">(</span><span class="n">status</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">transactionManager</span><span class="p">.</span><span class="na">rollback</span><span class="p">(</span><span class="n">status</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ServiceOne</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 设置一把可重入的公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ServiceTwo</span><span class="w"> </span><span class="n">serviceTwo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Result</span><span class="w">  </span><span class="nf">func</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">seckillId</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">userId</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">serviceTwo</span><span class="p">.</span><span class="na">sellProduct</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ServiceTwo</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="nd">@Transactional</span><span class="p">(</span><span class="n">rollbackFor</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Exception</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sellProduct</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 执行数据库操作——查询商品库存数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 如果 库存数量 满足要求 执行数据库操作——减少库存数量——模拟卖出货物操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">如何减少及解决bug</h2>
+                        <span id="post_page_title_date" class="date">2023.03.10</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><blockquote>
+<p>bug的起源:
+1945年，一只小飞蛾钻进了计算机电路里，导致系统无法工作，一位名叫格蕾丝·赫柏的人把飞蛾拍死在工作日志上，写道：就是这个 bug(虫子)，害我们今天的工作无法完成——于是，bug一词成了电脑系统程序的专业术语，形容那些系统中的缺陷或问题。</p>
+</blockquote>
+<p>bug一词，是指“故障”、“缺陷”。了解软件开发的朋友都非常熟悉，程序员和测试人员更不用说，在工作中会常遇到。 作为一名开发人员，项目出现bug是避免不了的。无论你是一名初入职场的小白，还是拥有经验丰富的大佬，只要经常写代码，梳理业务逻辑，很难免不出bug。正所谓常在河边走，哪能不湿鞋。记得以前经常听人说，如果你没有把系统搞宕机过，就不是一名合格的CTO，成为一名出色的开发人员，经验都是一个一个积累起来的。
+所谓的bug指的是生产环境发现的问题;那么只要线上不发现问题，那就不是bug。之所以这么讲是因为一旦影响程序的正常使用便会影响公司的利益，公司利益被影响你自己的利益也会被影响;所以为了自己写程序的时候尽量多测试，将可能会应对到的情况想得全一点，减少bug的出现。</p>
+<p>程序员能为了减少bug的出现能做的可以从代码方面下手:</p>
+<ul>
+<li>在正式开发前，做好准备工作，先梳理一下业务逻辑，根据业务场景可以使用什么设计模式，是否需要缓存，列一下需要用到的框架等，尽量考虑的全面一些，考虑一下不同的情况;</li>
+<li>在编写代码的时候需要注意以下几点，供参考：
+<ul>
+<li>在关键的地方写注释，标注一些关键的信息;</li>
+<li>增加校验;如: 调用第三方程序或者使用一些中间件的时候，拿到结果不要着急使用，先做校验，这样可以很大程度上避免NPE的出现;</li>
+<li>当在程序某个功能下加一个非堵塞性功能的时候，需要考虑是否会影响到主流程的使用，有时候可能不经意的一个问题会将它的影响无限放大，随之而来的就是用户投诉，老板亏钱;</li>
+<li>当编写代码的时候尽量写一些简洁，清晰的代码，比如一个方法实现的功能较多，应把它拆开。如果代码变得易于维护起来那么bug的数量也会大大降低;</li>
+<li>尽量编写一些能测试的代码，将一个方法的职责做到最小，一个方法就干一件事情;</li>
+<li>当开发功能完成之后不要着急测试，先自己审查一下代码，确认哪些地方可以进行优化，之后再调试功能进行单元测试;</li>
+</ul>
+</li>
+<li>当开发完成之后一定要进行单元测试，这可以大大降低bug的数量; 测试的时候需要模拟线上的环境数据来测试新增或修复的功能，否则即使改完功能之后可能会由于请求次数或数据量巨大问题导致功能不能使用。</li>
+</ul>
+<p>除此之外，一方面可以借助一些工具来进行bug的规避，比如sonar，可以发现一些潜在的错误和问题。另一方面我们要不断学习和提高自己的编程技能，以提高代码质量和减少错误的发生。</p>
+<p>尽管这样bug这种东西还是不可避免的，我们只能减少bug而不能消除bug，没有人保证自己的程序一定是没有问题的。减少bug的出现只能多测多验证，哪怕单元测试通过都不能非常有效减少bug，因为受到写单元测试的人的思维角度限制，导致单元测试的片面性。</p>
+<p>关于bug的种类，最容易出现的bug是逻辑上的bug，如复杂庞大一点软件如果不是所有地方都熟悉就写代码是比较容易遗漏一些特殊情况的。除了逻辑上的bug外在开发中还有框架中存在的bug，但是这种bug是我们避免不了的。如2021年爆发的log4j堪称史诗级的bug。
+没什么好的办法可以提前避免掉，就多用一些稳定的框架吧，有apache就用apache，没有就优先使用fork，start高的，从概率上减少。</p>
+<p>一个人的力量毕竟有限必要的时候可以叫上同事，进行code review。</p>
+<p>因为bug是不可避免的，所以解决bug能力就显得尤为重要，程序员归根到底拼的是解决问题的能力。</p>
+<p>bug的解决思路:</p>
+<ul>
+<li>确认bug的存在，包括复现bug的步骤和现象;</li>
+<li>分析bug的根本原因，找到导致bug的代码或逻辑，一般通过日志查看一些栈的信息;</li>
+<li>修复bug的代码或逻辑，并重新测试确认修复成功;</li>
+<li>编写针对bug的单元测试，验证bug是否修复;</li>
+<li>记录bug修复的过程和结果，以备将来参考和验证;</li>
+</ul>
+<p>亲自复现问题，关注第一现场，确定是必现还是偶现; 区分是人的问题还是环境的问题；如果是人的问题，那是配置参数的问题还是代码逻辑的问题。如果是配置参数的问题，则通过对比正常运行的配置参数发现问题。
+如果是代码逻辑的问题，则通过commit的历史二分查找缩小出现问题的逻辑范围; 如果是机器的问题，确定是单机问题还是集群问题; 如果是单机问题，则替换机器，如果是集群问题则考虑升级硬件设备。</p>
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diff --git a/docs/posts/codeguide/java-code-rule/index.html b/docs/posts/codeguide/java-code-rule/index.html
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+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%96%e7%a0%81%e8%a7%84%e8%8c%83">
+                    编码规范
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%85%e5%ad%98%e6%b3%84%e9%9c%b2%e9%97%ae%e9%a2%98">
+                    内存泄露问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%85%e5%ad%98%e6%b3%84%e9%9c%b2%e5%8e%9f%e5%9b%a0">
+                    内存泄露原因
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%98%e9%87%8f%e4%bd%9c%e7%94%a8%e5%9f%9f%e4%b8%8d%e5%90%88%e7%90%86%e5%af%bc%e8%87%b4%e5%86%85%e5%ad%98%e6%b3%84%e9%9c%b2">
+                    变量作用域不合理导致内存泄露
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%90%91%e9%9d%99%e6%80%81%e9%9b%86%e5%90%88%e6%b7%bb%e5%8a%a0%e6%95%b0%e6%8d%ae%e5%af%bc%e8%87%b4%e5%86%85%e5%ad%98%e6%b3%84%e9%9c%b2">
+                    向静态集合添加数据导致内存泄露
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%85%e9%83%a8%e7%b1%bb%e6%8c%81%e6%9c%89%e5%a4%96%e9%83%a8%e7%b1%bb%e5%bc%95%e7%94%a8%e5%af%bc%e8%87%b4%e5%86%85%e5%ad%98%e6%b3%84%e9%9c%b2">
+                    内部类持有外部类引用导致内存泄露
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e6%8d%ae%e7%bb%93%e6%9e%84%e4%b8%ad%e7%a7%bb%e9%99%a4%e5%85%83%e7%b4%a0%e5%af%bc%e8%87%b4%e5%86%85%e5%ad%98%e6%b3%84%e9%9c%b2">
+                    数据结构中移除元素导致内存泄露
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%9e%e6%8e%a5%e6%9c%aa%e9%87%8a%e6%94%be">
+                    连接未释放
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%a3%e7%a0%81%e7%bb%93%e6%9e%84">
+                    代码结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bc%98%e9%9b%85%e5%88%a4%e7%a9%ba">
+                    优雅判空
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8spring%e6%8f%90%e4%be%9b%e7%9a%84%e5%b7%a5%e5%85%b7%e7%b1%bbassert%e5%88%a4%e7%a9%ba">
+                    使用Spring提供的工具类Assert判空
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8java8%e9%93%be%e5%bc%8f%e8%b0%83%e7%94%a8%e7%89%b9%e6%80%a7%e5%88%a4%e7%a9%ba">
+                    使用Java8链式调用特性判空
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8beanvalidator%e6%b3%a8%e8%a7%a3%e5%88%a4%e7%a9%ba">
+                    使用BeanValidator注解判空
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%87%e5%a4%9aifelse">
+                    过多if..else
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e6%9e%9a%e4%b8%be%e4%bb%a3%e6%9b%bfifelse">
+                    使用枚举代替if..else
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%94%be%e5%85%a5%e6%95%b0%e6%8d%ae%e7%bb%93%e6%9e%84%e4%b8%ad%e8%bf%9b%e8%a1%8c%e5%88%a4%e6%96%ad%e4%bb%8e%e8%80%8c%e5%87%8f%e5%b0%91ifelse">
+                    放入数据结构中进行判断从而减少if..else
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8switchcase%e4%bb%a3%e6%9b%bfifelse">
+                    使用switch..case代替if..else
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b0%bd%e6%97%a9%e7%bb%93%e6%9d%9fif%e4%bd%bf%e4%bb%a3%e7%a0%81%e7%bb%93%e6%9e%84%e6%9b%b4%e6%b8%85%e6%99%b0">
+                    尽早结束if使代码结构更清晰
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e8%81%8c%e8%b4%a3%e9%93%be%e6%a8%a1%e5%bc%8f%e4%bb%a3%e6%9b%bfifelse">
+                    使用职责链模式代替if..else
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e6%a8%a1%e6%9d%bf%e6%96%b9%e6%b3%95%e6%a8%a1%e5%bc%8f%e4%bb%a3%e6%9b%bfifelse">
+                    使用模板方法模式代替if..else
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e5%b7%a5%e5%8e%82%e6%96%b9%e6%b3%95%e6%a8%a1%e5%bc%8f%e4%bb%a3%e6%9b%bfifelse">
+                    使用工厂方法模式代替if..else
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e6%b3%a8%e8%a7%a3%e4%bb%a3%e6%9b%bfifelse">
+                    使用注解代替if..else
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
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+
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+
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+                <a href="https://whiteppure.github.io/iblog/about/">关于</a>
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+            <p class="sub_title">
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+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1688701481347" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3517" width="16" height="16"><path d="M425.610455 85.814544H149.05897A42.303635 42.303635 0 0 0 106.6274 128.075535V896.492068c0 23.326702 18.976933 42.26099 42.43157 42.26099h682.743143a42.559504 42.559504 0 0 0 42.431569-42.559504v-384.016365a42.644793 42.644793 0 0 1 85.289587 0v384.016365A127.849091 127.849091 0 0 1 831.802113 1024H149.05897A127.635867 127.635867 0 0 1 21.337813 896.449423V128.03289A127.593222 127.593222 0 0 1 149.101614 0.524957h276.466196a42.644793 42.644793 0 0 1 0 85.289587z m564.062683 158.08425l-170.579174 170.579173a42.644793 42.644793 0 1 1-60.299738-60.299738L856.578738 256.393718H618.364922a42.644793 42.644793 0 1 1 0-85.289587h238.213816l-97.784512-97.784511A42.644793 42.644793 0 1 1 819.093964 13.019882l170.579174 170.579174a42.644793 42.644793 0 0 1 0 60.299738zM149.272194 597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h51.514911c59.190973 0 107.891327 23.284057 107.976617 97.102195 0 71.003581-49.46796 102.347504-106.185536 102.347504h-31.343923v66.781747a32.282109 32.282109 0 0 1-64.606862 0V597.552066z m92.709781 100.215264c31.429213 0 46.568114-16.46089 46.568114-45.757863 0-30.064579-17.313786-40.512554-48.359196-40.512554h-26.311837v86.270417h28.145563z m232.414124-142.860058c81.878003 0 136.036891 43.710913 136.036891 147.67892S556.231457 853.420826 477.935617 853.420826h-38.16709a42.644793 42.644793 0 0 1-42.644794-42.644793v-213.223967a42.644793 42.644793 0 0 1 42.644794-42.644794h34.542282z m-4.008611 240.729859c43.32711 0 73.988717-22.047358 73.988717-93.050939 0-71.046226-30.704251-90.705476-73.988717-90.705476h-8.699538v183.79906h8.699538zM692.481573 853.420826a32.282109 32.282109 0 0 1-32.282109-32.282108V597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h99.063855a29.680776 29.680776 0 1 1 0 59.404197h-77.144431v65.374469h61.749661a29.894 29.894 0 1 1 0 59.788h-61.749661v81.66478a32.282109 32.282109 0 0 1-32.282108 32.282108z" fill="#5f5f5f" p-id="3518"></path></svg>
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+    </div>
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+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">规范编写Java代码总结</h2>
+                        <span id="post_page_title_date" class="date">2021.11.25</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="编码规范">编码规范</h2>
+<p>我们为什么要遵守规范来编码？</p>
+<p>是因为通常在编码过程中我们不只自己进行开发，通常需要一个团队来进行，开发好之后还需要维护，所以编码规范就显的尤为重要。</p>
+<p>代码维护时间比较长，那么保证代码可读性就显得很重要。作为一个程序员，咱们得有点追求和信仰。推荐<a href="https://www.w3cschool.cn/alibaba_java/">《阿里巴巴Java开发手册》</a>。</p>
+<h2 id="内存泄露问题">内存泄露问题</h2>
+<p>内存泄漏是指不使用的对象持续占有内存使得内存得不到释放，从而造成内存空间的浪费。</p>
+<p><a href="/iblog/posts/jvm/jvm-about/#%E5%86%85%E5%AD%98%E6%B3%84%E6%BC%8F">内存泄露</a>导致问题：</p>
+<ul>
+<li>最明显问题频繁GC，从而<a href="/iblog/posts/jvm/jvm-about/#stw">STW</a>次数增加,导致用户体验变差；</li>
+<li>如果内存泄露问题严重，会导致OOM，直接导致程序不能正常运行；</li>
+</ul>
+<p>内存泄露是很严重的问题，在出现内存泄露的情况下，想要解决是肯定要修改代码的，所以在编写代码的时候要避免出现内存泄露。</p>
+<h3 id="内存泄露原因">内存泄露原因</h3>
+<p>大多数内存泄露的原因是，长生命周期的对象引用了短生命周期的对象。例如，A对象引用B对象，A对象的生命周期（t1-t4）比B对象的生命周期（t2-t3）长的多。当B对象没有被应用程序使用之后，A对象仍然在引用着B对象。这样，垃圾回收器就没办法将B对象从内存中移除，从而导致内存泄露问题。</p>
+<h4 id="变量作用域不合理导致内存泄露">变量作用域不合理导致内存泄露</h4>
+<p>一个变量的定义的作用范围大于其使用范围，很有可能会造成内存泄漏</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class UsingRandom {
+</span></span><span class="line"><span class="cl">    private String msg;
+</span></span><span class="line"><span class="cl">    public void receiveMsg(){
+</span></span><span class="line"><span class="cl">        readFromNet();//从网络中接受数据保存到msg中
+</span></span><span class="line"><span class="cl">        saveDB();//把msg保存到数据库中
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>解决办法，将msg定义在receiveMsg方法中或将msg重置为null。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class UsingRandom {
+</span></span><span class="line"><span class="cl">    private String msg;
+</span></span><span class="line"><span class="cl">    public void receiveMsg(){
+</span></span><span class="line"><span class="cl">        readFromNet();//从网络中接受数据保存到msg中
+</span></span><span class="line"><span class="cl">        saveDB();//把msg保存到数据库中
+</span></span><span class="line"><span class="cl">        msg = null;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h4 id="向静态集合添加数据导致内存泄露">向静态集合添加数据导致内存泄露</h4>
+<p>HashMap、LinkedList 等集合类，如果这些集合是静态的并且向集合中添加了对象，这些对象就算不再使用，也不会被GC主动回收的，它们的生命周期与JVM程序一致，容器中的对象在程序结束之前将不能被释放，从而造成内存泄漏。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MyTest {
+</span></span><span class="line"><span class="cl">    static Map&lt;String, User&gt; map = new HashMap&lt;&gt;();
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) throws InterruptedException {
+</span></span><span class="line"><span class="cl">        User user = new User();
+</span></span><span class="line"><span class="cl">        map.put(&#34;01&#34;,user);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>解决办法是将使用完后的集合和对象重置为null，或将集合替换成弱引用集合（只要垃圾回收机制一运行，不管 JVM 的内存空间是否足够，总会回收该对象占用的内存）。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    static Map&lt;String, User&gt; map = new HashMap&lt;&gt;();
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) throws InterruptedException {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        User user = new User();
+</span></span><span class="line"><span class="cl">        map.put(&#34;01&#34;,user);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        user = null;
+</span></span><span class="line"><span class="cl">        map = null;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        System.gc();
+</span></span><span class="line"><span class="cl">        Thread.sleep(1000);
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    static Map&lt;String, User&gt; map = new WeakHashMap&lt;&gt;();
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) throws InterruptedException {
+</span></span><span class="line"><span class="cl">        User user = new User();
+</span></span><span class="line"><span class="cl">        map.put(&#34;01&#34;,user);
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><h4 id="内部类持有外部类引用导致内存泄露">内部类持有外部类引用导致内存泄露</h4>
+<p>非静态内部类，自动生成的构造方法，默认的参数是外部类的类型，因此使用非内部内部类的时候会保留一个外部类的引用。如果换成静态内部类则不会生成默认的构造方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MyClass {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) throws Throwable {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public class A{
+</span></span><span class="line"><span class="cl">        public void methed1(){
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static  class B{
+</span></span><span class="line"><span class="cl">        public void methed1(){
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>如果一个外部类的实例对象的方法返回了一个内部类的实例对象。这个内部类对象被长期引用了，即使那个外部类实例对象不再被使用，但由于内部类持有外部类的实例对象，这个外部类对象将不会被垃圾回收，这也会造成内存泄漏。</p>
+<h4 id="数据结构中移除元素导致内存泄露">数据结构中移除元素导致内存泄露</h4>
+<ul>
+<li>链表中移除元素，没有将移除的元素置为null导致的内存泄露问题</li>
+</ul>
+<p>Java容器LinkedList移除元素方法核心源码:</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">//删除指定节点并返回被删除的元素值
+</span></span><span class="line"><span class="cl">E unlink(Node&lt;E&gt; x) {
+</span></span><span class="line"><span class="cl">    //获取当前值和前后节点
+</span></span><span class="line"><span class="cl">    final E element = x.item;
+</span></span><span class="line"><span class="cl">    final Node&lt;E&gt; next = x.next;
+</span></span><span class="line"><span class="cl">    final Node&lt;E&gt; prev = x.prev;
+</span></span><span class="line"><span class="cl">    if (prev == null) {
+</span></span><span class="line"><span class="cl">        first = next; //如果前一个节点为空(如当前节点为首节点)，后一个节点成为新的首节点
+</span></span><span class="line"><span class="cl">    } else {
+</span></span><span class="line"><span class="cl">        prev.next = next;//如果前一个节点不为空，那么他先后指向当前的下一个节点
+</span></span><span class="line"><span class="cl">        x.prev = null;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    if (next == null) {
+</span></span><span class="line"><span class="cl">        last = prev; //如果后一个节点为空(如当前节点为尾节点)，当前节点前一个成为新的尾节点
+</span></span><span class="line"><span class="cl">    } else {
+</span></span><span class="line"><span class="cl">        next.prev = prev;//如果后一个节点不为空，后一个节点向前指向当前的前一个节点
+</span></span><span class="line"><span class="cl">        x.next = null;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    x.item = null; // help gc
+</span></span><span class="line"><span class="cl">    size--;
+</span></span><span class="line"><span class="cl">    modCount++;
+</span></span><span class="line"><span class="cl">    return element;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>除了修改节点间的关联关系，我们还要做的就是赋值为null的操作，不管GC何时会开始清理，我们都应及时的将无用的对象标记为可被清理的对象。</p>
+<hr>
+<ul>
+<li>在栈中将该元素出栈，没有将出栈的元素置为null导致的内存泄露问题</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public E pop(){
+</span></span><span class="line"><span class="cl">    if(size == 0)
+</span></span><span class="line"><span class="cl">        return null;
+</span></span><span class="line"><span class="cl">    else{
+</span></span><span class="line"><span class="cl">        E e = (E) elementData[--size];
+</span></span><span class="line"><span class="cl">        elementData[size] = null; // help gc
+</span></span><span class="line"><span class="cl">        return e;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><hr>
+<ul>
+<li>改变hash表中对象的属性值，再将该元素移除导致的内存泄露问题</li>
+</ul>
+<p>因为改变了对象属性的值相当于改变了改对象的hash值，删除的时候是根据对象的hash值来删除的，删除对象的时候找不到对应的hash值，所以不能删除，最终导致内存泄露。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class ChangeHashCode {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        HashSet set = new HashSet();
+</span></span><span class="line"><span class="cl">        Person p1 = new Person(1001, &#34;AA&#34;);
+</span></span><span class="line"><span class="cl">        Person p2 = new Person(1002, &#34;BB&#34;);
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">        set.add(p1);
+</span></span><span class="line"><span class="cl">        set.add(p2);
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">        p1.name = &#34;CC&#34;; // 导致了内存的泄漏
+</span></span><span class="line"><span class="cl">        set.remove(p1);  // 对象哈希值发生变化，检索不到，导致删除失败
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">        System.out.println(set);
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">        set.add(new Person(1001, &#34;CC&#34;));
+</span></span><span class="line"><span class="cl">        System.out.println(set);
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">        set.add(new Person(1001, &#34;AA&#34;));
+</span></span><span class="line"><span class="cl">        System.out.println(set);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">class Person {
+</span></span><span class="line"><span class="cl">    int id;
+</span></span><span class="line"><span class="cl">    String name;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">    public Person(int id, String name) {
+</span></span><span class="line"><span class="cl">        this.id = id;
+</span></span><span class="line"><span class="cl">        this.name = name;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public boolean equals(Object o) {
+</span></span><span class="line"><span class="cl">        if (this == o) return true;
+</span></span><span class="line"><span class="cl">        if (!(o instanceof Person)) return false;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">        Person person = (Person) o;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">        if (id != person.id) return false;
+</span></span><span class="line"><span class="cl">        return name != null ? name.equals(person.name) : person.name == null;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public int hashCode() {
+</span></span><span class="line"><span class="cl">        int result = id;
+</span></span><span class="line"><span class="cl">        result = 31 * result + (name != null ? name.hashCode() : 0);
+</span></span><span class="line"><span class="cl">        return result;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public String toString() {
+</span></span><span class="line"><span class="cl">        return &#34;Person{&#34; +
+</span></span><span class="line"><span class="cl">                &#34;id=&#34; + id +
+</span></span><span class="line"><span class="cl">                &#34;, name=&#39;&#34; + name + &#39;\&#39;&#39; +
+</span></span><span class="line"><span class="cl">                &#39;}&#39;;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h4 id="连接未释放">连接未释放</h4>
+<p>如数据库连接、网络连接和IO连接等。当不再使用时，需要调用close方法来释放连接。只有连接被关闭后，垃圾回收器才会回收对应的对象。否则，如果在连接过程中，对一些对象不显性地关闭，将会造成大量的对象无法被回收，从而引起内存泄漏。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">    try{
+</span></span><span class="line"><span class="cl">        Connection conn =null;
+</span></span><span class="line"><span class="cl">        Class.forName(&#34;com.mysql.jdbc.Driver&#34;);
+</span></span><span class="line"><span class="cl">        conn =DriverManager.getConnection(&#34;url&#34;,&#34;&#34;,&#34;&#34;);
+</span></span><span class="line"><span class="cl">        Statement stmt =conn.createStatement();
+</span></span><span class="line"><span class="cl">        ResultSet rs =stmt.executeQuery(&#34;....&#34;);
+</span></span><span class="line"><span class="cl">    } catch（Exception e）{
+</span></span><span class="line"><span class="cl">    } finally {
+</span></span><span class="line"><span class="cl">        // 1．关闭结果集 Statement
+</span></span><span class="line"><span class="cl">        // 2．关闭声明的对象 ResultSet
+</span></span><span class="line"><span class="cl">        // 3．关闭连接 Connection
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h2 id="代码结构">代码结构</h2>
+<p>编写代码最终要的原则就是要具有扩展性，如果没有扩展性那么代码维护起来会非常麻烦。</p>
+<h3 id="优雅判空">优雅判空</h3>
+<h4 id="使用spring提供的工具类assert判空">使用Spring提供的工具类Assert判空</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MyTest {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        Object obj = new Object();
+</span></span><span class="line"><span class="cl">        Assert.notNull(obj,&#34;对象不能为空&#34;);
+</span></span><span class="line"><span class="cl">        Assert.isTrue(obj != null,&#34;对象不能为空&#34;);
+</span></span><span class="line"><span class="cl">        ArrayList&lt;Object&gt; list = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">        Assert.notEmpty(list,&#34;list不能为空&#34;);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h4 id="使用java8链式调用特性判空">使用Java8链式调用特性判空</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MyTest {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        Object obj = new Object();
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;是否不为空：&#34; + Optional.of(obj).isPresent());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        User user = new User();
+</span></span><span class="line"><span class="cl">        user.setId(1);
+</span></span><span class="line"><span class="cl">        user.setName(&#34;ls&#34;);
+</span></span><span class="line"><span class="cl">        Optional&lt;User&gt; zs = Optional.of(user).filter(u -&gt; u.getName().equals(&#34;zs&#34;));
+</span></span><span class="line"><span class="cl">        System.out.println(zs.get());
+</span></span><span class="line"><span class="cl">        zs.ifPresent(item -&gt;{
+</span></span><span class="line"><span class="cl">             System.out.println(&#34;对象不等于空，做的一系列操作&#34;);
+</span></span><span class="line"><span class="cl">         });
+</span></span><span class="line"><span class="cl">        User user1 = Optional.of(zs.orElse(new User())).get();
+</span></span><span class="line"><span class="cl">        System.out.println(user1);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    static class User {
+</span></span><span class="line"><span class="cl">        private int id;
+</span></span><span class="line"><span class="cl">        private String name;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public String getName() {
+</span></span><span class="line"><span class="cl">            return name;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        public int getId() {
+</span></span><span class="line"><span class="cl">            return id;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        public void setName(String name) {
+</span></span><span class="line"><span class="cl">            this.name = name;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        public void setId(int id) {
+</span></span><span class="line"><span class="cl">            this.id = id;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        @Override
+</span></span><span class="line"><span class="cl">        public String toString() {
+</span></span><span class="line"><span class="cl">            return &#34;User{&#34; +
+</span></span><span class="line"><span class="cl">                    &#34;id=&#34; + id +
+</span></span><span class="line"><span class="cl">                    &#34;, name=&#39;&#34; + name + &#39;\&#39;&#39; +
+</span></span><span class="line"><span class="cl">                    &#39;}&#39;;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>自定义链式调用，对Optional扩展：</p>
+<ul>
+<li><a href="https://www.hollischuang.com/archives/5605">https://www.hollischuang.com/archives/5605</a></li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">@Data
+</span></span><span class="line"><span class="cl">public class User {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    private String name;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    private String gender;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    private School school;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Data
+</span></span><span class="line"><span class="cl">    public static class School {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        private String scName;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        private String adress;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="o">/**</span>
+</span></span><span class="line"><span class="cl"><span class="o">*</span> <span class="err">@</span><span class="n">author</span> <span class="n">Axin</span>
+</span></span><span class="line"><span class="cl"><span class="o">*</span> <span class="err">@</span><span class="n">since</span> <span class="mi">2020</span><span class="o">-</span><span class="mi">09</span><span class="o">-</span><span class="mi">10</span>
+</span></span><span class="line"><span class="cl"><span class="o">*</span> <span class="err">@</span><span class="n">summary</span> <span class="err">链式调用</span> <span class="n">bean</span> <span class="err">中</span> <span class="n">value</span> <span class="err">的方法</span>
+</span></span><span class="line"><span class="cl"><span class="o">*/</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="n">final</span> <span class="k">class</span> <span class="n">OptionalBean</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="k">static</span> <span class="n">final</span> <span class="n">OptionalBean</span><span class="o">&lt;</span><span class="err">?</span><span class="o">&gt;</span> <span class="n">EMPTY</span> <span class="o">=</span> <span class="n">new</span> <span class="n">OptionalBean</span><span class="o">&lt;&gt;</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="n">final</span> <span class="n">T</span> <span class="n">value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="n">OptionalBean</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="n">null</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">空值会抛出空指针</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">value</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="n">OptionalBean</span><span class="p">(</span><span class="n">T</span> <span class="n">value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="n">Objects</span><span class="o">.</span><span class="n">requireNonNull</span><span class="p">(</span><span class="n">value</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">包装一个不能为空的</span> <span class="n">bean</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">value</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">OptionalBean</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">of</span><span class="p">(</span><span class="n">T</span> <span class="n">value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">new</span> <span class="n">OptionalBean</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">value</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">包装一个可能为空的</span> <span class="n">bean</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">value</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">OptionalBean</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">ofNullable</span><span class="p">(</span><span class="n">T</span> <span class="n">value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">value</span> <span class="o">==</span> <span class="n">null</span> <span class="err">?</span> <span class="n">empty</span><span class="p">()</span> <span class="p">:</span> <span class="n">of</span><span class="p">(</span><span class="n">value</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">取出具体的值</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">fn</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="o">&lt;</span><span class="n">R</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">T</span> <span class="n">get</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">Objects</span><span class="o">.</span><span class="n">isNull</span><span class="p">(</span><span class="n">value</span><span class="p">)</span> <span class="err">?</span> <span class="n">null</span> <span class="p">:</span> <span class="n">value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">取出一个可能为空的对象</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">fn</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="o">&lt;</span><span class="n">R</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="o">&lt;</span><span class="n">R</span><span class="o">&gt;</span> <span class="n">OptionalBean</span><span class="o">&lt;</span><span class="n">R</span><span class="o">&gt;</span> <span class="n">getBean</span><span class="p">(</span><span class="n">Function</span><span class="o">&lt;</span><span class="err">?</span> <span class="n">super</span> <span class="n">T</span><span class="p">,</span> <span class="err">?</span> <span class="k">extends</span> <span class="n">R</span><span class="o">&gt;</span> <span class="n">fn</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">Objects</span><span class="o">.</span><span class="n">isNull</span><span class="p">(</span><span class="n">value</span><span class="p">)</span> <span class="err">?</span> <span class="n">OptionalBean</span><span class="o">.</span><span class="n">empty</span><span class="p">()</span> <span class="p">:</span> <span class="n">OptionalBean</span><span class="o">.</span><span class="n">ofNullable</span><span class="p">(</span><span class="n">fn</span><span class="o">.</span><span class="n">apply</span><span class="p">(</span><span class="n">value</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">如果目标值为空</span> <span class="err">获取一个默认值</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">other</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">T</span> <span class="n">orElse</span><span class="p">(</span><span class="n">T</span> <span class="n">other</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">value</span> <span class="o">!=</span> <span class="n">null</span> <span class="err">?</span> <span class="n">value</span> <span class="p">:</span> <span class="n">other</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">如果目标值为空</span> <span class="err">通过</span><span class="n">lambda表达式获取一个值</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">other</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">T</span> <span class="n">orElseGet</span><span class="p">(</span><span class="n">Supplier</span><span class="o">&lt;</span><span class="err">?</span> <span class="k">extends</span> <span class="n">T</span><span class="o">&gt;</span> <span class="n">other</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">value</span> <span class="o">!=</span> <span class="n">null</span> <span class="err">?</span> <span class="n">value</span> <span class="p">:</span> <span class="n">other</span><span class="o">.</span><span class="n">get</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">如果目标值为空</span> <span class="err">抛出一个异常</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">exceptionSupplier</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="o">&lt;</span><span class="n">X</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">throws</span> <span class="n">X</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="o">&lt;</span><span class="n">X</span> <span class="k">extends</span> <span class="n">Throwable</span><span class="o">&gt;</span> <span class="n">T</span> <span class="n">orElseThrow</span><span class="p">(</span><span class="n">Supplier</span><span class="o">&lt;</span><span class="err">?</span> <span class="k">extends</span> <span class="n">X</span><span class="o">&gt;</span> <span class="n">exceptionSupplier</span><span class="p">)</span> <span class="n">throws</span> <span class="n">X</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="n">value</span> <span class="o">!=</span> <span class="n">null</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="n">value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">throw</span> <span class="n">exceptionSupplier</span><span class="o">.</span><span class="n">get</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">boolean</span> <span class="n">isPresent</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">value</span> <span class="o">!=</span> <span class="n">null</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">ifPresent</span><span class="p">(</span><span class="n">Consumer</span><span class="o">&lt;</span><span class="err">?</span> <span class="n">super</span> <span class="n">T</span><span class="o">&gt;</span> <span class="n">consumer</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="n">value</span> <span class="o">!=</span> <span class="n">null</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">            <span class="n">consumer</span><span class="o">.</span><span class="n">accept</span><span class="p">(</span><span class="n">value</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="ne">int</span> <span class="n">hashCode</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">Objects</span><span class="o">.</span><span class="n">hashCode</span><span class="p">(</span><span class="n">value</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">空值常量</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">OptionalBean</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">empty</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="err">@</span><span class="n">SuppressWarnings</span><span class="p">(</span><span class="s2">&#34;unchecked&#34;</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">        <span class="n">OptionalBean</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">none</span> <span class="o">=</span> <span class="p">(</span><span class="n">OptionalBean</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="p">)</span> <span class="n">EMPTY</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">none</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    User axin = new User();
+</span></span><span class="line"><span class="cl">    User.School school = new User.School();
+</span></span><span class="line"><span class="cl">    axin.setName(&#34;hello&#34;);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 1. 基本调用
+</span></span><span class="line"><span class="cl">    String value1 = OptionalBean.ofNullable(axin)
+</span></span><span class="line"><span class="cl">            .getBean(User::getSchool)
+</span></span><span class="line"><span class="cl">            .getBean(User.School::getAdress).get();
+</span></span><span class="line"><span class="cl">    System.out.println(value1);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 2. 扩展的 isPresent方法 用法与 Optional 一样
+</span></span><span class="line"><span class="cl">    boolean present = OptionalBean.ofNullable(axin)
+</span></span><span class="line"><span class="cl">            .getBean(User::getSchool)
+</span></span><span class="line"><span class="cl">            .getBean(User.School::getAdress).isPresent();
+</span></span><span class="line"><span class="cl">    System.out.println(present);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 3. 扩展的 ifPresent 方法
+</span></span><span class="line"><span class="cl">    OptionalBean.ofNullable(axin)
+</span></span><span class="line"><span class="cl">            .getBean(User::getSchool)
+</span></span><span class="line"><span class="cl">            .getBean(User.School::getAdress)
+</span></span><span class="line"><span class="cl">            .ifPresent(adress -&gt; System.out.println(String.format(&#34;地址存在:%s&#34;, adress)));
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 4. 扩展的 orElse
+</span></span><span class="line"><span class="cl">    String value2 = OptionalBean.ofNullable(axin)
+</span></span><span class="line"><span class="cl">            .getBean(User::getSchool)
+</span></span><span class="line"><span class="cl">            .getBean(User.School::getAdress).orElse(&#34;家里蹲&#34;);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    System.out.println(value2);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 5. 扩展的 orElseThrow
+</span></span><span class="line"><span class="cl">    try {
+</span></span><span class="line"><span class="cl">        String value3 = OptionalBean.ofNullable(axin)
+</span></span><span class="line"><span class="cl">                .getBean(User::getSchool)
+</span></span><span class="line"><span class="cl">                .getBean(User.School::getAdress).orElseThrow(() -&gt; new RuntimeException(&#34;空指针了&#34;));
+</span></span><span class="line"><span class="cl">    } catch (Exception e) {
+</span></span><span class="line"><span class="cl">        System.out.println(e.getMessage());
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h4 id="使用beanvalidator注解判空">使用BeanValidator注解判空</h4>
+<p>思路：定义一个注解，将需要校验的参数对象都标注该注解，利用SpringAOP，拦截该注解，将其中标注的参数取出，最后通过BeanValidator进行校验。</p>
+<p>所需依赖：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">&lt;dependency&gt;
+</span></span><span class="line"><span class="cl">    &lt;groupId&gt;org.hibernate&lt;/groupId&gt;
+</span></span><span class="line"><span class="cl">    &lt;artifactId&gt;hibernate-validator&lt;/artifactId&gt;
+</span></span><span class="line"><span class="cl">&lt;/dependency&gt;
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">/**
+</span></span><span class="line"><span class="cl"> * facade接口注解， 用于统一对facade进行参数校验及异常捕获
+</span></span><span class="line"><span class="cl"> * @author whitepure
+</span></span><span class="line"><span class="cl"> */
+</span></span><span class="line"><span class="cl">@Target({ElementType.METHOD,ElementType.PARAMETER})
+</span></span><span class="line"><span class="cl">@Retention(RetentionPolicy.RUNTIME)
+</span></span><span class="line"><span class="cl">public @interface Facade {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">@Slf4j
+</span></span><span class="line"><span class="cl">@Aspect
+</span></span><span class="line"><span class="cl">@Component
+</span></span><span class="line"><span class="cl">public class FacadeAspect {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Around(&#34;@annotation(com.spring.example.annotation.Facade)&#34;)
+</span></span><span class="line"><span class="cl">    public Object facade(ProceedingJoinPoint pjp) throws Exception {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        // 获取，执行目标方法
+</span></span><span class="line"><span class="cl">        Method method = ((MethodSignature) pjp.getSignature()).getMethod();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        Object[] args = pjp.getArgs();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        log.info(&#34;获取@Facede注解参数列表,参数: {}&#34;, args);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        // 参数类型
+</span></span><span class="line"><span class="cl">        Class&lt;?&gt; returnType = ((MethodSignature) pjp.getSignature()).getMethod().getReturnType();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        //循环遍历所有参数，进行参数校验
+</span></span><span class="line"><span class="cl">        for (Object parameter : args) {
+</span></span><span class="line"><span class="cl">            try {
+</span></span><span class="line"><span class="cl">                BeanValidator.validateObject(parameter);
+</span></span><span class="line"><span class="cl">            } catch (ValidationException e) {
+</span></span><span class="line"><span class="cl">                return getFailedResponse(returnType, e);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            // 目标方法执行
+</span></span><span class="line"><span class="cl">            return pjp.proceed();
+</span></span><span class="line"><span class="cl">        } catch (Throwable throwable) {
+</span></span><span class="line"><span class="cl">            // 返回通用失败响应
+</span></span><span class="line"><span class="cl">            return getFailedResponse(returnType, throwable);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    /**
+</span></span><span class="line"><span class="cl">     * 定义并返回一个通用的失败响应
+</span></span><span class="line"><span class="cl">     */
+</span></span><span class="line"><span class="cl">    private Object getFailedResponse(Class&lt;?&gt; returnType, Throwable throwable)
+</span></span><span class="line"><span class="cl">            throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        //如果返回值的类型为BaseResponse 的子类，则创建一个通用的失败响应
+</span></span><span class="line"><span class="cl">        if (returnType.getDeclaredConstructor().newInstance() instanceof ApiResponse) {
+</span></span><span class="line"><span class="cl">            ApiResponse response = (ApiResponse) returnType.getDeclaredConstructor().newInstance();
+</span></span><span class="line"><span class="cl">            String message = throwable.getMessage();
+</span></span><span class="line"><span class="cl">            log.error(&#34;校验bean异常：&#34;, throwable);
+</span></span><span class="line"><span class="cl">            response.setMessage(message);
+</span></span><span class="line"><span class="cl">            response.setCode(Status.ERROR.getCode());
+</span></span><span class="line"><span class="cl">            return response;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        log.error(&#34;failed to getFailedResponse , returnType ({}) is not instanceof BaseResponse&#34;, returnType);
+</span></span><span class="line"><span class="cl">        return null;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">BeanValidator</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="k">static</span> <span class="n">final</span> <span class="n">Validator</span> <span class="n">validator</span> <span class="o">=</span> <span class="n">Validation</span>
+</span></span><span class="line"><span class="cl">            <span class="o">.</span><span class="n">byProvider</span><span class="p">(</span><span class="n">HibernateValidator</span><span class="o">.</span><span class="k">class</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">            <span class="o">.</span><span class="n">configure</span><span class="p">()</span><span class="o">.</span><span class="n">failFast</span><span class="p">(</span><span class="bp">true</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">            <span class="o">.</span><span class="n">buildValidatorFactory</span><span class="p">()</span><span class="o">.</span><span class="n">getValidator</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">校验对象</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">object</span> <span class="n">object</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">groups</span> <span class="n">groups</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">validateObject</span><span class="p">(</span><span class="ne">Object</span> <span class="n">object</span><span class="p">,</span> <span class="n">Class</span><span class="o">&lt;</span><span class="err">?</span><span class="o">&gt;...</span> <span class="n">groups</span><span class="p">)</span> <span class="n">throws</span> <span class="n">ValidationException</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Set</span><span class="o">&lt;</span><span class="n">ConstraintViolation</span><span class="o">&lt;</span><span class="ne">Object</span><span class="o">&gt;&gt;</span> <span class="n">constraintViolations</span> <span class="o">=</span> <span class="n">validator</span><span class="o">.</span><span class="n">validate</span><span class="p">(</span><span class="n">object</span><span class="p">,</span> <span class="n">groups</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="n">constraintViolations</span><span class="o">.</span><span class="n">stream</span><span class="p">()</span><span class="o">.</span><span class="n">findFirst</span><span class="p">()</span><span class="o">.</span><span class="n">isPresent</span><span class="p">())</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">throw</span> <span class="n">new</span> <span class="n">ValidationException</span><span class="p">(</span><span class="n">constraintViolations</span><span class="o">.</span><span class="n">stream</span><span class="p">()</span><span class="o">.</span><span class="n">findFirst</span><span class="p">()</span><span class="o">.</span><span class="n">get</span><span class="p">()</span><span class="o">.</span><span class="n">getMessage</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">校验对象</span><span class="n">bean</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">t</span>      <span class="n">bean</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">groups</span> <span class="err">校验组</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span> <span class="n">ValidResult</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">ValidResult</span> <span class="n">validateBean</span><span class="p">(</span><span class="n">T</span> <span class="n">t</span><span class="p">,</span> <span class="n">Class</span><span class="o">&lt;</span><span class="err">?</span><span class="o">&gt;...</span> <span class="n">groups</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ValidResult</span> <span class="n">result</span> <span class="o">=</span> <span class="n">new</span> <span class="n">ValidResult</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Set</span><span class="o">&lt;</span><span class="n">ConstraintViolation</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;&gt;</span> <span class="n">violationSet</span> <span class="o">=</span> <span class="n">validator</span><span class="o">.</span><span class="n">validate</span><span class="p">(</span><span class="n">t</span><span class="p">,</span> <span class="n">groups</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">boolean</span> <span class="n">hasError</span> <span class="o">=</span> <span class="n">violationSet</span> <span class="o">!=</span> <span class="n">null</span> <span class="o">&amp;&amp;</span> <span class="n">violationSet</span><span class="o">.</span><span class="n">size</span><span class="p">()</span> <span class="o">&gt;</span> <span class="mi">0</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">result</span><span class="o">.</span><span class="n">setHasErrors</span><span class="p">(</span><span class="n">hasError</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="n">hasError</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="k">for</span> <span class="p">(</span><span class="n">ConstraintViolation</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">violation</span> <span class="p">:</span> <span class="n">violationSet</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">                <span class="n">result</span><span class="o">.</span><span class="n">addError</span><span class="p">(</span><span class="n">violation</span><span class="o">.</span><span class="n">getPropertyPath</span><span class="p">()</span><span class="o">.</span><span class="n">toString</span><span class="p">(),</span> <span class="n">violation</span><span class="o">.</span><span class="n">getMessage</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">            <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">result</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">校验</span><span class="n">bean的某一个属性</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">obj</span>          <span class="n">bean</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="n">param</span> <span class="n">propertyName</span> <span class="err">属性名称</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">@</span><span class="k">return</span> <span class="n">ValidResult</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">ValidResult</span> <span class="n">validateProperty</span><span class="p">(</span><span class="n">T</span> <span class="n">obj</span><span class="p">,</span> <span class="ne">String</span> <span class="n">propertyName</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ValidResult</span> <span class="n">result</span> <span class="o">=</span> <span class="n">new</span> <span class="n">ValidResult</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Set</span><span class="o">&lt;</span><span class="n">ConstraintViolation</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;&gt;</span> <span class="n">violationSet</span> <span class="o">=</span> <span class="n">validator</span><span class="o">.</span><span class="n">validateProperty</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">propertyName</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">boolean</span> <span class="n">hasError</span> <span class="o">=</span> <span class="n">violationSet</span> <span class="o">!=</span> <span class="n">null</span> <span class="o">&amp;&amp;</span> <span class="n">violationSet</span><span class="o">.</span><span class="n">size</span><span class="p">()</span> <span class="o">&gt;</span> <span class="mi">0</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">result</span><span class="o">.</span><span class="n">setHasErrors</span><span class="p">(</span><span class="n">hasError</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="n">hasError</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="k">for</span> <span class="p">(</span><span class="n">ConstraintViolation</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">violation</span> <span class="p">:</span> <span class="n">violationSet</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">                <span class="n">result</span><span class="o">.</span><span class="n">addError</span><span class="p">(</span><span class="n">propertyName</span><span class="p">,</span> <span class="n">violation</span><span class="o">.</span><span class="n">getMessage</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">            <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">result</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">校验结果类</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Data</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="k">class</span> <span class="n">ValidResult</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="err">是否有错误</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">        <span class="n">private</span> <span class="n">boolean</span> <span class="n">hasErrors</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="err">错误信息</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">        <span class="n">private</span> <span class="n">List</span><span class="o">&lt;</span><span class="n">ErrorMessage</span><span class="o">&gt;</span> <span class="n">errors</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">public</span> <span class="n">ValidResult</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">this</span><span class="o">.</span><span class="n">errors</span> <span class="o">=</span> <span class="n">new</span> <span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">public</span> <span class="n">boolean</span> <span class="n">hasErrors</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="n">hasErrors</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">public</span> <span class="n">void</span> <span class="n">setHasErrors</span><span class="p">(</span><span class="n">boolean</span> <span class="n">hasErrors</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">this</span><span class="o">.</span><span class="n">hasErrors</span> <span class="o">=</span> <span class="n">hasErrors</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="err">获取所有验证信息</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="err">@</span><span class="k">return</span> <span class="err">集合形式</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">        <span class="n">public</span> <span class="n">List</span><span class="o">&lt;</span><span class="n">ErrorMessage</span><span class="o">&gt;</span> <span class="n">getAllErrors</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="n">errors</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="err">获取所有验证信息</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="err">@</span><span class="k">return</span> <span class="err">字符串形式</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">        <span class="n">public</span> <span class="ne">String</span> <span class="n">getErrors</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">StringBuilder</span> <span class="n">sb</span> <span class="o">=</span> <span class="n">new</span> <span class="n">StringBuilder</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">            <span class="k">for</span> <span class="p">(</span><span class="n">ErrorMessage</span> <span class="n">error</span> <span class="p">:</span> <span class="n">errors</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">error</span><span class="o">.</span><span class="n">getPropertyPath</span><span class="p">())</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="s2">&#34;:&#34;</span><span class="p">)</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">error</span><span class="o">.</span><span class="n">getMessage</span><span class="p">())</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="s2">&#34; &#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="p">}</span>
+</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="n">sb</span><span class="o">.</span><span class="n">toString</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">public</span> <span class="n">void</span> <span class="n">addError</span><span class="p">(</span><span class="ne">String</span> <span class="n">propertyName</span><span class="p">,</span> <span class="ne">String</span> <span class="n">message</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">this</span><span class="o">.</span><span class="n">errors</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">new</span> <span class="n">ErrorMessage</span><span class="p">(</span><span class="n">propertyName</span><span class="p">,</span> <span class="n">message</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Data</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="k">class</span> <span class="n">ErrorMessage</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">private</span> <span class="ne">String</span> <span class="n">propertyPath</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">private</span> <span class="ne">String</span> <span class="n">message</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">public</span> <span class="n">ErrorMessage</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">public</span> <span class="n">ErrorMessage</span><span class="p">(</span><span class="ne">String</span> <span class="n">propertyPath</span><span class="p">,</span> <span class="ne">String</span> <span class="n">message</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">this</span><span class="o">.</span><span class="n">propertyPath</span> <span class="o">=</span> <span class="n">propertyPath</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">this</span><span class="o">.</span><span class="n">message</span> <span class="o">=</span> <span class="n">message</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h3 id="过多ifelse">过多if..else</h3>
+<p>替换if..else并不会降低代码的复杂度，相反比较少见的写法可能会增加认知负荷，从而进一步增加了复杂度。之所以要替换过多的if..else是为了对代码进行解耦合，方便扩展代码，最终方便对代码的维护。</p>
+<p>以下有几种常见的方法来替换过多的if..else。</p>
+<h4 id="使用枚举代替ifelse">使用枚举代替if..else</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MyTest</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="ne">String</span><span class="p">[]</span> <span class="n">args</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">String</span> <span class="n">val</span> <span class="o">=</span> <span class="s2">&#34;FOUR&#34;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">condition</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;--------------&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">newCondition</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">condition</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="s2">&#34;ONE&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">1111111</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="s2">&#34;TWO&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">2222222</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="s2">&#34;THREE&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">3333333</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">newCondition</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ConditionEnum</span> <span class="n">conditionEnum</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">try</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">conditionEnum</span> <span class="o">=</span> <span class="n">ConditionEnum</span><span class="o">.</span><span class="n">valueOf</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="n">catch</span> <span class="p">(</span><span class="n">IllegalArgumentException</span> <span class="n">e</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="k">return</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="n">exec</span><span class="p">(</span><span class="n">conditionEnum</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">exec</span><span class="p">(</span><span class="n">ConditionEnum</span> <span class="n">conditionEnum</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">conditionEnum</span><span class="o">.</span><span class="n">context</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="k">enum</span> <span class="n">ConditionEnum</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ONE</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">            <span class="n">public</span> <span class="n">void</span> <span class="n">context</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">                <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">1111111</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="p">},</span>
+</span></span><span class="line"><span class="cl">        <span class="n">TWO</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">            <span class="n">public</span> <span class="n">void</span> <span class="n">context</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">                <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">2222222</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="p">},</span>
+</span></span><span class="line"><span class="cl">        <span class="n">THREE</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">            <span class="n">public</span> <span class="n">void</span> <span class="n">context</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">                <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">3333333</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="p">};</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">public</span> <span class="n">abstract</span> <span class="n">void</span> <span class="n">context</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>也可用枚举替换成这样：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">newCondition</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ConditionEnum</span> <span class="n">condition</span> <span class="o">=</span> <span class="n">ConditionEnum</span><span class="o">.</span><span class="n">getCondition</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="p">(</span><span class="n">condition</span> <span class="o">==</span> <span class="n">null</span> <span class="err">?</span> <span class="n">val</span> <span class="p">:</span> <span class="n">condition</span><span class="o">.</span><span class="n">value</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="k">enum</span> <span class="n">ConditionEnum</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ONE</span><span class="p">(</span><span class="s2">&#34;ONE&#34;</span><span class="p">,</span><span class="mi">1111111</span><span class="p">),</span>
+</span></span><span class="line"><span class="cl">        <span class="n">TWO</span><span class="p">(</span><span class="s2">&#34;TWO&#34;</span><span class="p">,</span><span class="mi">2222222</span><span class="p">),</span>
+</span></span><span class="line"><span class="cl">        <span class="n">THREE</span><span class="p">(</span><span class="s2">&#34;THREE&#34;</span><span class="p">,</span><span class="mi">3333333</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">private</span> <span class="ne">String</span> <span class="n">key</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">private</span> <span class="n">Integer</span> <span class="n">value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">ConditionEnum</span><span class="p">(</span><span class="ne">String</span> <span class="n">key</span><span class="p">,</span><span class="n">Integer</span> <span class="n">value</span><span class="p">){</span>
+</span></span><span class="line"><span class="cl">            <span class="n">this</span><span class="o">.</span><span class="n">key</span> <span class="o">=</span> <span class="n">key</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">this</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="n">value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">public</span>  <span class="k">static</span> <span class="n">ConditionEnum</span> <span class="n">getCondition</span><span class="p">(</span><span class="ne">String</span> <span class="n">key</span><span class="p">){</span>
+</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="n">Arrays</span><span class="o">.</span><span class="n">stream</span><span class="p">(</span><span class="n">ConditionEnum</span><span class="o">.</span><span class="n">values</span><span class="p">())</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">x</span> <span class="o">-&gt;</span> <span class="n">Objects</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">x</span><span class="o">.</span><span class="n">key</span><span class="p">,</span> <span class="n">key</span><span class="p">))</span><span class="o">.</span><span class="n">findFirst</span><span class="p">()</span><span class="o">.</span><span class="n">orElse</span><span class="p">(</span><span class="n">null</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span></code></pre></div><h4 id="放入数据结构中进行判断从而减少ifelse">放入数据结构中进行判断从而减少if..else</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MyTest {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        String val = &#34;1&#34;;
+</span></span><span class="line"><span class="cl">        condition(val);
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;--------------&#34;);
+</span></span><span class="line"><span class="cl">        newCondition(val);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    public static void condition(String val) {
+</span></span><span class="line"><span class="cl">        if (&#34;1&#34;.equals(val)){
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 1111111);
+</span></span><span class="line"><span class="cl">        }else if (&#34;2&#34;.equals(val)){
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 2222222);
+</span></span><span class="line"><span class="cl">        }else if (&#34;3&#34;.equals(val)){
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 3333333);
+</span></span><span class="line"><span class="cl">        }else {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + val);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    public static void newCondition(String val){
+</span></span><span class="line"><span class="cl">        Map&lt;String, Function&lt;?,?&gt;&gt; map = new HashMap&lt;&gt;();
+</span></span><span class="line"><span class="cl">        map.put(&#34;1&#34;,(action) -&gt; 1111111);
+</span></span><span class="line"><span class="cl">        map.put(&#34;2&#34;,(action) -&gt; 2222222);
+</span></span><span class="line"><span class="cl">        map.put(&#34;3&#34;,(action) -&gt; 3333333);
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;val:&#34; + (map.get(val) != null ? map.get(val).apply(null) : val));
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h4 id="使用switchcase代替ifelse">使用switch..case代替if..else</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MyTest {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        String val = &#34;FOUR&#34;;
+</span></span><span class="line"><span class="cl">        condition(val);
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;--------------&#34;);
+</span></span><span class="line"><span class="cl">        newCondition(val);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void condition(String val) {
+</span></span><span class="line"><span class="cl">        if (&#34;ONE&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 1111111);
+</span></span><span class="line"><span class="cl">        } else if (&#34;TWO&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 2222222);
+</span></span><span class="line"><span class="cl">        } else if (&#34;THREE&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 3333333);
+</span></span><span class="line"><span class="cl">        } else {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + val);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void newCondition(String val) {
+</span></span><span class="line"><span class="cl">        switch (val) {
+</span></span><span class="line"><span class="cl">            case &#34;ONE&#34;:
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;val:&#34; + 1111111);
+</span></span><span class="line"><span class="cl">                break;
+</span></span><span class="line"><span class="cl">            case &#34;TWO&#34;:
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;val:&#34; + 2222222);
+</span></span><span class="line"><span class="cl">                break;
+</span></span><span class="line"><span class="cl">            case &#34;THREE&#34;:
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;val:&#34; + 3333333);
+</span></span><span class="line"><span class="cl">                break;
+</span></span><span class="line"><span class="cl">            default:
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;val:&#34; + val);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h4 id="尽早结束if使代码结构更清晰">尽早结束if使代码结构更清晰</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MyTest {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        String val = &#34;222&#34;;
+</span></span><span class="line"><span class="cl">        condition(val);
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;--------------&#34;);
+</span></span><span class="line"><span class="cl">        newCondition(val);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void condition(String val) {
+</span></span><span class="line"><span class="cl">        if (&#34;ONE&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 1111111);
+</span></span><span class="line"><span class="cl">        } else if (&#34;TWO&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 2222222);
+</span></span><span class="line"><span class="cl">        } else if (&#34;THREE&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 3333333);
+</span></span><span class="line"><span class="cl">        } else {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + val);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void newCondition(String val) {
+</span></span><span class="line"><span class="cl">        if (&#34;ONE&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 1111111);
+</span></span><span class="line"><span class="cl">            return;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        if (&#34;TWO&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 2222222);
+</span></span><span class="line"><span class="cl">            return;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        if (&#34;THREE&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 3333333);
+</span></span><span class="line"><span class="cl">            return;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;val:&#34; + val);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h4 id="使用职责链模式代替ifelse">使用职责链模式代替if..else</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MyTest</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="ne">String</span><span class="p">[]</span> <span class="n">args</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">String</span> <span class="n">val</span> <span class="o">=</span> <span class="s2">&#34;1&#34;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">condition</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;--------------&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">newCondition</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">condition</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="s2">&#34;ONE&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">1111111</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="s2">&#34;TWO&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">2222222</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="s2">&#34;THREE&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">3333333</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">newCondition</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">One</span> <span class="n">one</span> <span class="o">=</span> <span class="n">new</span> <span class="n">One</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Two</span> <span class="n">two</span> <span class="o">=</span> <span class="n">new</span> <span class="n">Two</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Three</span> <span class="n">three</span> <span class="o">=</span> <span class="n">new</span> <span class="n">Three</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">//</span> <span class="err">设置调用链</span><span class="p">,</span><span class="err">可设置成死循环</span>
+</span></span><span class="line"><span class="cl">        <span class="n">one</span><span class="o">.</span><span class="n">setAbstractHandler</span><span class="p">(</span><span class="n">two</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">two</span><span class="o">.</span><span class="n">setAbstractHandler</span><span class="p">(</span><span class="n">three</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">//</span> <span class="err">执行</span>
+</span></span><span class="line"><span class="cl">        <span class="n">one</span><span class="o">.</span><span class="n">exec</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">abstract</span> <span class="k">class</span> <span class="n">AbstractHandler</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">AbstractHandler</span> <span class="n">abstractHandler</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">setAbstractHandler</span><span class="p">(</span><span class="n">AbstractHandler</span> <span class="n">abstractHandler</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">abstractHandler</span> <span class="o">=</span> <span class="n">abstractHandler</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">abstract</span> <span class="n">void</span> <span class="n">exec</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="k">class</span> <span class="n">One</span> <span class="k">extends</span> <span class="n">AbstractHandler</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">exec</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">val</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="s2">&#34;ONE&#34;</span><span class="p">)){</span>
+</span></span><span class="line"><span class="cl">            <span class="n">abstractHandler</span><span class="o">.</span><span class="n">exec</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="k">return</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">1111111</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="k">class</span> <span class="n">Two</span> <span class="k">extends</span> <span class="n">AbstractHandler</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">exec</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">val</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="s2">&#34;TWO&#34;</span><span class="p">)){</span>
+</span></span><span class="line"><span class="cl">            <span class="n">abstractHandler</span><span class="o">.</span><span class="n">exec</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="k">return</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">2222222</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="k">class</span> <span class="n">Three</span> <span class="k">extends</span> <span class="n">AbstractHandler</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">exec</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">val</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="s2">&#34;THREE&#34;</span><span class="p">)</span> <span class="err">?</span> <span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">3333333</span> <span class="p">:</span> <span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h4 id="使用模板方法模式代替ifelse">使用模板方法模式代替if..else</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MyTest</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="ne">String</span><span class="p">[]</span> <span class="n">args</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">String</span> <span class="n">val</span> <span class="o">=</span> <span class="s2">&#34;ONE&#34;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">condition</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;--------------&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">newCondition</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">condition</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="s2">&#34;ONE&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">1111111</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="s2">&#34;TWO&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">2222222</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="s2">&#34;THREE&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">3333333</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">newCondition</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">Objects</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">,</span> <span class="s2">&#34;ONE&#34;</span><span class="p">)</span> <span class="o">&amp;&amp;</span> <span class="o">!</span><span class="n">Objects</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">,</span> <span class="s2">&#34;TWO&#34;</span><span class="p">)</span> <span class="o">&amp;&amp;</span> <span class="o">!</span><span class="n">Objects</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">,</span> <span class="s2">&#34;THREE&#34;</span><span class="p">))</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="k">return</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="n">List</span><span class="o">&lt;</span><span class="n">ConditionTemplate</span><span class="o">&gt;</span> <span class="n">list</span> <span class="o">=</span> <span class="n">new</span> <span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">Arrays</span><span class="o">.</span><span class="n">asList</span><span class="p">(</span><span class="n">new</span> <span class="n">One</span><span class="p">(),</span> <span class="n">new</span> <span class="n">Two</span><span class="p">(),</span> <span class="n">new</span> <span class="n">Three</span><span class="p">()));</span>
+</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="p">(</span><span class="n">ConditionTemplate</span> <span class="n">item</span> <span class="p">:</span> <span class="n">list</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">item</span><span class="o">.</span><span class="n">template</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">abstract</span> <span class="k">class</span> <span class="n">ConditionTemplate</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">template</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">){</span>
+</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="p">(</span><span class="n">supportIns</span><span class="p">(</span><span class="n">val</span><span class="p">)){</span>
+</span></span><span class="line"><span class="cl">            <span class="n">support</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">abstract</span> <span class="n">void</span> <span class="n">support</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">abstract</span> <span class="n">boolean</span> <span class="n">supportIns</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="k">class</span> <span class="n">One</span> <span class="k">extends</span> <span class="n">ConditionTemplate</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">support</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">1111111</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">boolean</span> <span class="n">supportIns</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="s2">&#34;ONE&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="k">class</span> <span class="n">Two</span> <span class="k">extends</span> <span class="n">ConditionTemplate</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">support</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">2222222</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">boolean</span> <span class="n">supportIns</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="s2">&#34;TWO&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="k">class</span> <span class="n">Three</span> <span class="k">extends</span> <span class="n">ConditionTemplate</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">support</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;val:&#34;</span> <span class="o">+</span> <span class="mi">3333333</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">boolean</span> <span class="n">supportIns</span><span class="p">(</span><span class="ne">String</span> <span class="n">val</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="s2">&#34;THREE&#34;</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h4 id="使用工厂方法模式代替ifelse">使用工厂方法模式代替if..else</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MyTest {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        String val = &#34;ONE&#34;;
+</span></span><span class="line"><span class="cl">        condition(val);
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;--------------&#34;);
+</span></span><span class="line"><span class="cl">        newCondition(val);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void condition(String val) {
+</span></span><span class="line"><span class="cl">        if (&#34;ONE&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 1111111);
+</span></span><span class="line"><span class="cl">        } else if (&#34;TWO&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 2222222);
+</span></span><span class="line"><span class="cl">        } else if (&#34;THREE&#34;.equals(val)) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + 3333333);
+</span></span><span class="line"><span class="cl">        } else {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + val);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void newCondition(String val) {
+</span></span><span class="line"><span class="cl">         Map&lt;String, ConditionFactory&gt; operationMap = new HashMap&lt;&gt;();
+</span></span><span class="line"><span class="cl">        operationMap.put(&#34;ONE&#34;,new One());
+</span></span><span class="line"><span class="cl">        operationMap.put(&#34;TWO&#34;,new Two());
+</span></span><span class="line"><span class="cl">        operationMap.put(&#34;THREE&#34;,new Three());
+</span></span><span class="line"><span class="cl">        if (operationMap.get(val) == null) {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;val:&#34; + val);
+</span></span><span class="line"><span class="cl">        }else {
+</span></span><span class="line"><span class="cl">            operationMap.get(val).printCondition();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">interface ConditionFactory{
+</span></span><span class="line"><span class="cl">    void printCondition();
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">class One implements ConditionFactory {
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public void printCondition() {
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;val:&#34; + 1111111);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">class Two implements ConditionFactory {
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public void printCondition() {
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;val:&#34; + 2222222);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">class Three implements ConditionFactory {
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public void printCondition() {
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;val:&#34; + 3333333);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h4 id="使用注解代替ifelse">使用注解代替if..else</h4>
+<ul>
+<li><a href="https://www.zhihu.com/question/318511891/answer/1730548947">https://www.zhihu.com/question/318511891/answer/1730548947</a></li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">@Retention(RetentionPolicy.RUNTIME)  
+</span></span><span class="line"><span class="cl">@Target(ElementType.TYPE)  
+</span></span><span class="line"><span class="cl">public @interface PayCode {  
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     String value();    
+</span></span><span class="line"><span class="cl">     String name();  
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">@PayCode(value = &#34;alia&#34;, name = &#34;支付宝支付&#34;)  
+</span></span><span class="line"><span class="cl">@Service
+</span></span><span class="line"><span class="cl">public class AliaPay implements IPay {  
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     @Override
+</span></span><span class="line"><span class="cl">     public void pay() {  
+</span></span><span class="line"><span class="cl">         System.out.println(&#34;===发起支付宝支付===&#34;);  
+</span></span><span class="line"><span class="cl">     }  
+</span></span><span class="line"><span class="cl">}  
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">@PayCode(value = &#34;weixin&#34;, name = &#34;微信支付&#34;)  
+</span></span><span class="line"><span class="cl">@Service
+</span></span><span class="line"><span class="cl">public class WeixinPay implements IPay {  
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     @Override
+</span></span><span class="line"><span class="cl">     public void pay() {  
+</span></span><span class="line"><span class="cl">         System.out.println(&#34;===发起微信支付===&#34;);  
+</span></span><span class="line"><span class="cl">     }  
+</span></span><span class="line"><span class="cl">} 
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">@PayCode(value = &#34;jingdong&#34;, name = &#34;京东支付&#34;)  
+</span></span><span class="line"><span class="cl">@Service
+</span></span><span class="line"><span class="cl">public class JingDongPay implements IPay {  
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     @Override
+</span></span><span class="line"><span class="cl">     public void pay() {  
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;===发起京东支付===&#34;);  
+</span></span><span class="line"><span class="cl">     }  
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">@Service
+</span></span><span class="line"><span class="cl">public class PayService2 implements ApplicationListener&lt;ContextRefreshedEvent&gt; {  
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     private static Map&lt;String, IPay&gt; payMap = null;  
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     @Override
+</span></span><span class="line"><span class="cl">     public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {  
+</span></span><span class="line"><span class="cl">         ApplicationContext applicationContext = contextRefreshedEvent.getApplicationContext();  
+</span></span><span class="line"><span class="cl">         Map&lt;String, Object&gt; beansWithAnnotation = applicationContext.getBeansWithAnnotation(PayCode.class);  
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">         if (beansWithAnnotation != null) {  
+</span></span><span class="line"><span class="cl">             payMap = new HashMap&lt;&gt;();  
+</span></span><span class="line"><span class="cl">             beansWithAnnotation.forEach((key, value) -&gt;{  
+</span></span><span class="line"><span class="cl">                 String bizType = value.getClass().getAnnotation(PayCode.class).value();  
+</span></span><span class="line"><span class="cl">                 payMap.put(bizType, (IPay) value);  
+</span></span><span class="line"><span class="cl">             });  
+</span></span><span class="line"><span class="cl">         }  
+</span></span><span class="line"><span class="cl">     }  
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     public void pay(String code) {  
+</span></span><span class="line"><span class="cl">        payMap.get(code).pay();  
+</span></span><span class="line"><span class="cl">     }  
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></div>
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+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">如何做好程序设计功能</h2>
+                        <span id="post_page_title_date" class="date">2022.08.02</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="功能设计流程图">功能设计流程图</h2>
+<p>与外部系统交互、本系统模块之间流程，比较好用的画圈软件draw .io或在线的process on</p>
+<h2 id="数据库设计">数据库设计</h2>
+<p>从DDD角度界限上下文、ER图、评审表结构设计是否合理，表的关联关系是否合理、是否创建索引、是否大数据量表考虑放到分片库以及分片字段设计</p>
+<h2 id="缓存设计">缓存设计</h2>
+<ul>
+<li>缓存结构是否合理 redis结构选择(string、hash、 list、set)：
+<ul>
+<li>对于C端高并发接口，hash结构要慎重用，key不能用固定的key，防止key倾 斜，可以采用string结构，value尽可能压缩下，比如 {&ldquo;groupId:&rdquo;:&ldquo;536363737&rdquo;， &ldquo;groupId&rdquo;:&ldquo;989898989&rdquo;}改为&quot;536363737#989898989&quot;，大大节省redis空间。</li>
+<li>对于数据量很大，单条valve报文很大的业务，如果经常判断某个值是否存在，可以考虑采用set结构，利用sismember方法，时间复杂度O(1)</li>
+</ul>
+</li>
+<li>缓存过期时间是否合理：不能怕脑袋胡乱给一个时间，如果存放的数量，过期时间一定要给短一些，比如2日分钟或半小时，否则增长很长，打爆redis</li>
+<li>缓存是否设计考虑预热和重建机制</li>
+<li>缓存中尽可能不能使用delete命令；delete会阻塞redis，特别是存放数量很大的hash、set、list， 容易阻塞redis，引1发事故，替换方案：expire -1</li>
+<li>是否是否设计二级缓存；本地缓存+分布式缓存，实现方式caffine或quavatredis，对于数据量不大热点数据（一般1W条以下，单条报文10kb以下，比如网点数据、航线数据)可以放本地缓存，这些热点数据查询非常频繁，容易造成redis倾斜，本地缓存可以抗这种高井发流量.</li>
+<li>防穿透处理
+<ul>
+<li>提供c端的接口，查询不到数据，尽可能不要穿透到数据库，防止打爆数据库，查不到一定记得打印告營日志，及时人工千预</li>
+<li>提前将数据预热到缓存中(系统启动预热或者运营后台有手动刷新缓存按钮或者有个job刷缓存)</li>
+</ul>
+</li>
+</ul>
+<h2 id="job设计">job设计</h2>
+<ul>
+<li>job逻辑要考虑幂等设计</li>
+<li>job逻辑尽可能轻量级，不要太重，导致执行逻辑很久(如果确实逻辑比较复杂，可以分拆job或者从代码层面优化，例如：分批井行处理、减少单次处理数据〕</li>
+<li>构建数据到缓存类似的job，尽可能选择时间在晚上12点以后，尽量不要白天进行，因为白天流量很大，重建缓存容易引起接口抖动</li>
+<li>对于定时执行的job，设计执行时间的时候，要慎重考虑线上整个job执行的时间，根据这个时间配置cron表达式，不要拍脑袋随意设置，</li>
+<li>不然本次job没执行完，下一次job执行的时候容易错过。</li>
+<li>对于大表数据（百万、千万甚至亿级），可以利用xxjob、saturn等分布式调度框架的分片处理能力，并行刷数据，提供处理速度。</li>
+</ul>
+<h2 id="接口设计">接口设计</h2>
+<ul>
+<li>高并发接口必须在测试环境压测，清楚的知道接口支持的QPS，另外根据压测报告给出的优化建议，及时调整线上的配置、代码优化。</li>
+<li>提供给C端的接口，要清楚曝光位省、然后根据接口可能预计调用的流量、压测的接口最大支持的QPS，决定是否扩容、是否需要限流及兜底逻镇、是否熔断</li>
+<li>程序中涉及的异常信息，及时配置错误监控告警，遇事做到心中有数。</li>
+<li>对于业务关键位置，及时打印info级别的业务追踪日志，如果是高并发接口，要做好开关，能秒级关闭，因为打印日志也特别耗性能。</li>
+<li>程序设计方面，高井发接口，尽可能使用缓存、能异步就异步 （一般用mq，不要用多线程异步）、 尽可能采用无锁设计防止线程Lock CPU冲高，批量写库</li>
+<li>接口前置逻铜提前，尽早过滤掉不合规運银，缩短接口整个调用链路时长，提升接口整体吞吐量。</li>
+<li>接口要考虑无状态设计、昇等设计(考虑分布式锁唯—key)、安全设计(接口方法签名、是否接第三方防刷服务判断是否黑产用户）
+<blockquote>
+<p>无状态服务：客户端的每次请求必须具备自描述信息，通过这些信息识别客户端身份。服务端不保存任何客户端请求者信息
+有状态服务: 即服务端需要记录每次会话的客户端信息，从而识别客户端身份，根据用户身份进行请求的处理，典型的设计如 tomcat 中的 session</p>
+</blockquote>
+</li>
+<li>对第三方服务做到零信任，考虑降级、熔断，与业务方确认好兜底逻辑处理。</li>
+<li>工具类尽可能使用apache、google等出的、 一些github小众的开源框架很多在高井发场最有bug和性能瓶颈。</li>
+<li>接口的时间复杂度，部分在设计的时候尽可能保证是0 (1），例如调用第三方接口，for循环调用的，是否可以提到缩环外，传多个id批量调用一次，时间复杂度从0（n）降为0(1)</li>
+</ul>
+<h2 id="监控设计">监控设计</h2>
+<ul>
+<li>核心接西做好监控，例如：调用量上涨/下跌80%、接口健康度监控 （5分钟error超过100次、5分钟接口超过1s 100日次、5分钟不可用次数超过1000次）</li>
+<li>应用监控，例如：应用cpu、内存层、gc、繁忙线程数、数据库连接池连接数监控告警</li>
+<li>中间件监控，例如：redis可用性、cpu-内存-流量-大key-热key-慢查询监控、kafka可用性-消息积压情况-丢失率监控告警</li>
+<li>数据库监控，例如：mysql cpu、慢sql监控告警</li>
+<li>业务监控，例如：发券量暴涨或暴跌、活动注册人数同比或环比异常</li>
+</ul>
+<h2 id="预案设计">预案设计</h2>
+<p>设计预案减少损失</p>
+<ul>
+<li>设计全局开关（系统接近不可用，通过配置中心全局开关快速切断接口流量，保证系統可用）</li>
+<li>遇到系统故障，非核心功能通过配置中心开关下线，保证整体服务可用</li>
+<li>应用能自动扩容（这里就要求应用做到无状态设计，比如：我们之间有一些应用有调用加密机，但是新应用节点需要申请白名单，这种设计方式就没法自动扩容</li>
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diff --git a/docs/posts/codeguide/java-project-reconstitution/index.html b/docs/posts/codeguide/java-project-reconstitution/index.html
new file mode 100644
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+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>重构一个程序 ｜ 脚踏实地</title>
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+    <meta name="description" content="什么是重构 摘自《重构：改善既有代码的设计》 重构(名词形式): 对软件内部结构的一种调整，目的是在不改变软件可观察行为的前提下，提高其可理解性，降低其修改成本。 重构" />
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+        
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+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
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+        <ul class="nav">
+            
+            
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+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af%e9%87%8d%e6%9e%84">
+                    什么是重构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
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+                    为什么重构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8d%e6%9e%84%e5%9c%ba%e6%99%af">
+                    重构场景
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%8e%e4%b9%88%e9%87%8d%e6%9e%84">
+                    怎么重构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%a3%e7%a0%81%e5%91%bd%e5%90%8d">
+                    代码命名
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+            
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+        <ul class="nav">
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+            <li class="nav-item">
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+                    复杂度与依赖传递
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
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+        
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
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+                    过度设计
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+                    没有时间重构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+
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+                        <h2 id="post_single_title">重构一个程序</h2>
+                        <span id="post_page_title_date" class="date">2023.04.20</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
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+                    <div class="post_content markdown"><h2 id="什么是重构">什么是重构</h2>
+<blockquote>
+<p>摘自《重构：改善既有代码的设计》</p>
+<ul>
+<li>重构(名词形式): 对软件内部结构的一种调整，目的是在不改变软件可观察行为的前提下，提高其可理解性，降低其修改成本。</li>
+<li>重构(动词形式): 使用一些列重构手法，在不改变软件可观察行为的前提下，调整其结构。</li>
+</ul>
+<p>重构的目的是使软件更容易被理解和修改。可以在软件内部做很多修改，但必须对软件可观察的外部行为只造成很小的变化，甚至不造成变化。与之形成对比的是性能优化，和重构一样，性能优化通常不会改变组件的行为，只会改变其内部结构。但是两者的出发点不同：性能优化往往使代码较难理解，但为了得到所需的性能你不得不这么做。</p>
+<p>重构不会改变软件可观察的行为，重构之后的软件功能一往如此。</p>
+</blockquote>
+<p>重构代码更像是整理代码，重构可以重构但是不要改变代码原本的功能，需要修改其内部结构，在不改变软件可观测行为的前提下，调整代码结构，当然这种修改肯定是有利的一面。提高软件的可理解性，降低变更成本。</p>
+<h2 id="为什么重构">为什么重构</h2>
+<p>首先需要明确的一点是,重构是一种经济适用性行为，而非道德使然，重构只有一个目的，就是让我们更快更好的开发代码，为什么需要重构，是因为现有的代码不能够提高开发效率，有时不但不能提高，还会降低很多很多。</p>
+<p>其次重构是保证代码质量的一个极其有效的手段，不至于让代码腐化到无可救药的地步。项目在演进，代码不停地在堆砌。如果没有人为代码的质量负责任，代码总是会往越来越混乱的方向演进。当混乱到一定程度之后，量变引起质变，项目的维护成本已经高过重新开发一套新代码的成本，想要再去重构，已经没有人能做到了。</p>
+<p>当我们遇到这段代码实在是太恶心了，花了很长时间才看懂，并且代码非常僵硬，而正好这个需求需要改动到这里，代码真的就像一坨屎。而最后是怎么处理的，我们通常是又给它加了一坨。</p>
+<p>我们为什么会这么去做？因为重构会减慢当前任务速度，所以保持最快速度。</p>
+<p>为什么这么做能干得又多又快？因为他将成本放到了未来。软件工程最大的成本在于维护，我们每一次代码的改动，都应该是对历史代码的一次整理，而非单一的功能堆积。
+这样虽然能赢得现在，但终将失去未来，而这个失败的未来或许需要全团队与他一起买单。 这或许就是我们重构的最根本原因。</p>
+<p>优秀的代码或架构不是一开始就能完全设计好的，就像优秀的公司和产品也都是迭代出来的。所以当我们做一个需求一定要回过头整理代码，保证代码的质量。傻瓜都能写出计算机可以理解的代码。唯有能写出人类容易理解的代码的，才是优秀的程序员。</p>
+<p>除此之外重构对程序员本身的意义：</p>
+<ol>
+<li>更快速的定位问题，节省调试时间。</li>
+<li>最小化变更风险，提高代码质量，减少修复事故的时间，提高ROI。</li>
+<li>得到程序员同行的认可，更好的发展机会。</li>
+</ol>
+<h2 id="重构场景">重构场景</h2>
+<p>因为重构是一种经济实用性行为，所以重构的时候需要考虑成本，仅对必要的代码进行重构，某个工作行为如果重复三次就可以认为未来也会存在重复，因此通过重构使得下次工作更加高效，这是一种务实的作法。</p>
+<p>举例，在添加一个新功能时，看之前的旧代码，如果有一些公共的功能可以提取出来，而这个功能，你新开发的功能又恰好用的上，那么重构这个功能可以帮助你梳理、理解代码，程序如果如此迭代下去，长久下来会提高团队的开发效率。</p>
+<p>在《重构：改善既有代码的设计》一书中提到持续重构的理念。重构本来就不是一件应该特别拨出时间来做的事，重构应该随时随地的进行。重构不一定是需要大规模的展开的任务，重构应该是不断持续进行的，将任务拆解为多个具有完备性的任务，每周完成一个，每个任务的上线都不会引起问题，并使项目变得更好，这是一种持续重构的精神态度，是高效能程序员最应该具有的工作习惯。</p>
+<p>不要代码烂到一定程度之后才去重构。当代码真的烂到出现开发效率低，招了很多人，天天加班，出活却不多，线上 bug 频发，领导发飙，中层束手无策，工程师抱怨不断，查找 bug 困难的时候，基本上重构也无法解决问题了。</p>
+<p>我们要正确地看待代码质量和重构这件事情。技术在更新、需求在变化、人员在流动，代码质量总会在下降，代码总会存在不完美，重构就会持续在进行。应当时刻具有持续重构意识，才能避免开发初期就过度设计，避免代码维护的过程中质量的下降。</p>
+<h2 id="怎么重构">怎么重构</h2>
+<p>通读代码，分析现状，找到可重构代码。列出重构计划，确定重构目标，不要盲目的重构，明确的描述出重构后能达到的预期是什么。重构计划中必须给出测试验证方案，保证代码的可测试性，保证重构前与重构后软件的行为一致。
+将重构任务当作项目来管理，对指定任务的人明确的排期和进度同步。这是重构大体上基本的步骤。</p>
+<p>在重构项目时，我们可以借鉴分治思想，将重构任务拆分成每周都能见到效果的小任务，形成正反馈，定期开会同步进度，不断加强团队的重构意识。</p>
+<p>下面是重构代码的一些常见问题和重构的一些建议</p>
+<h3 id="代码命名">代码命名</h3>
+<ul>
+<li>见名知意；避免增加认知负荷；</li>
+<li>考虑命名对整体架构的影响，要与整体的风格保持一致；</li>
+</ul>
+<p>见<a href="/iblog/posts/essays/clean-code/#%E6%B3%A8%E9%87%8A%E5%91%BD%E5%90%8D">注释命名</a></p>
+<h3 id="复杂度与依赖传递">复杂度与依赖传递</h3>
+<blockquote>
+<p>所谓复杂性，就是任何使得软件难于理解和修改的因素。</p>
+</blockquote>
+<p>模糊性与依赖性是引起复杂性的2个主要因素，模糊性产生了最直接的复杂度，让我们很难读懂代码真正想表达的含义，无法读懂这些代码，也就意味着我们更难去改变它。而依赖性又导致了复杂性不断传递，不断外溢的复杂性最终导致系统的无限腐化，一旦代码变成意大利面条，几乎不可能修复，成本将成指数倍增长。</p>
+<p>我们可以找到很多因素导致系统腐化的原因：</p>
+<ul>
+<li>想简单图省事，没有及时治理不合理的内容</li>
+<li>缺少匠心追求，对肮脏代码视而不见</li>
+<li>技术能力不够，无法应对复杂系统</li>
+</ul>
+<p>除了上述内容外，还可以想到很多理由。但我们发现他们好像有一个共同的指向点 - 软件工程师，似乎所有复杂的源头就是软件工程师的不合格导致，所以其实一些罪恶的根因是我们自己？</p>
+<blockquote>
+<p>软件复杂才是常态，不复杂才不正常。软件的复杂性是固有的，包括问题域的复杂性、管理开发过程的困难性、通过软件可能实现的灵活性与刻画离散系统行为的问题，这4个方面来分析了软件的发展一定伴随着复杂，这是软件工程这本科学所必然伴随的一个特性。
+所以所有的软件架构万变不离其宗，都在致力解决软件的复杂性。</p>
+</blockquote>
+<blockquote>
+<p>世间万物都需要额外的能量和秩序来维持自身，无一例外。没有外部力量的注入事物就会逐渐崩溃，这是世间万物的规律，而非我们哪里做得不对。所以我们才需要对系统进行维护甚至重构，降低系统的复杂度来保障系统的正常运行及降低维护的成本。</p>
+</blockquote>
+<h3 id="过度设计">过度设计</h3>
+<p>过度设计就是增加复杂度的一种。</p>
+<p>在初学编程的时候,只管埋头写程序,浑浑噩噩的进行开发。然而很快便发现事先做好设计可以节省返工的成本。许多人把设计看作软件开发的关键环节，而把编程看成是机械式的劳动。他们认为设计就像画工程图纸而编码就像施工。
+因此需要把更更多得精力放在预先设计上，以免日后修改。</p>
+<p>但是当过分的考虑程序未来所要面对的需求时，将陷入过度设计的陷阱，为了当下用不上的能力，而使程序变得复杂，这些设计很可能是现在未来都不需要的。</p>
+<p>过度设计是一种负面的设计，所以要合理的进行设计，避免过度设计，把握好设计的尺度，适度设计。下面是避免过度设计的几点建议：</p>
+<ul>
+<li>将注意力集中在应用程序的核心功能上，以满足用户的基本需求。避免在边缘功能上过度设计和开发，这些功能可能会增加程序的复杂性和难度。尽量采用简单的解决方案，而不是过度复杂的设计。</li>
+<li>设计的目的之一是为产品和用户带来更多的价值和服务，因此必须保证所有的设计都有其存在的“价值”，这个“价值”可以是为用户带来更好的体验，也可以是是为产品带来更多的收益。任何没有“价值”的设计，就是“过度设计”，可以直接删除。</li>
+</ul>
+<p>要明确一点，设计是产品实现用户需求之间的一种手段，不是最终的目的，不能为了设计而设计，添加一些乱七八糟的功能，那样产品的用户体验也是很差的。在设计中应当确保应用程序的核心功能得到优先关注，避免过度边缘化。</p>
+<h3 id="没有时间重构">没有时间重构</h3>
+<p>这是重构所面临最多的借口，是自己也是团队的借口。</p>
+<p>为此必须要明确重构是经济行为而不是一种道德行为，重构使得开发效率变得更高，因此仅对必要的代码进行重构，某个工作行为如果重复三次就可以认为未来也会存在重复，因此通过重构使得下次工作更加高效，这是一种务实的作法，而重构不一定是需要大规模的展开的任务，重构应该是不断持续进行的，将任务拆解为多个具有完备性的任务，每周完成一个，每个任务的上线都不会引起问题，并使项目变得更好，这是一种持续重构的精神态度，是高效能程序员最应该具有的工作习惯。</p>
+<p>如果你在给项目添加新的特性，发现当前的代码不能高效的完成这个任务，并且同样的任务出现三次以上，那么这时你应该先重构，再开发新特性。</p>
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+                        <h2 id="post_single_title">CAS详解</h2>
+                        <span id="post_page_title_date" class="date">2020.04.04</span>
+                        
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+                    <div class="post_content markdown"><h2 id="cas">CAS</h2>
+<p>CAS全称为<code>Compare and Swap</code>被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更新为新值。
+CAS操作是原子的，这意味着在多个线程同时执行CAS操作时，不会发生竞争条件。</p>
+<h3 id="使用示例">使用示例</h3>
+<p><code>java.util.concurrent.atomic</code>并发包下的所有原子类都是基于CAS来实现的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">atomicInteger</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">result</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;更新成功，当前值：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;更新失败，当前值：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>CAS一些常见使用场景：</p>
+<ul>
+<li>使用CAS实现线程安全的计数器，避免传统锁的开销。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">oldValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">counter</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">counter</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">oldValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">newValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>使用CAS来实现无锁队列、栈等数据结构。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASQueue</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">enqueue</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">dequeue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentHead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentHead</span><span class="p">,</span><span class="w"> </span><span class="n">nextNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在数据库中，CAS可以用于实现乐观锁机制，避免长时间持有锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">OptimisticLocking</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">version</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">updateWithOptimisticLock</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedVersion</span><span class="p">,</span><span class="w"> </span><span class="n">Runnable</span><span class="w"> </span><span class="n">updateTask</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">currentVersion</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentVersion</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedVersion</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">updateTask</span><span class="p">.</span><span class="na">run</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentVersion</span><span class="p">,</span><span class="w"> </span><span class="n">currentVersion</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getVersion</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OptimisticLocking</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">OptimisticLocking</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">updateTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Performing update&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">version</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">getVersion</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">success</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">updateWithOptimisticLock</span><span class="p">(</span><span class="n">version</span><span class="p">,</span><span class="w"> </span><span class="n">updateTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">success</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Update successful.&#34;</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Update failed.&#34;</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在实现线程池时，CAS可以用于安全地管理线程状态和任务队列。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASThreadPool</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">submitTask</span><span class="p">(</span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Runnable</span><span class="w"> </span><span class="nf">getTask</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentHead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentHead</span><span class="p">,</span><span class="w"> </span><span class="n">nextNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="unsafe">Unsafe</h3>
+<p><code>Unsafe</code>是CAS的核心类，Java无法直接访问底层操作系统，而是通过<code>native</code>方法来访问。不过尽管如此，JVM还是开了一个后门，JDK中有一个类<code>Unsafe</code>，它提供了硬件级别的原子操作。</p>
+<p><code>Unsafe</code>类位于<code>sun.misc</code>包中，它提供了访问底层操作系统的特定功能，如直接内存访问、CAS 操作等。
+由于其提供了直接操作内存的能力，使用不当可能导致内存泄漏、数据损坏等问题，应谨慎使用。
+<code>Unsafe</code>类包含了许多不安全的操作，所以它并不是Java标准的一部分，而且在Java9开始已经标记为受限制的API。</p>
+<p>Java中CAS操作的执行依赖于<code>Unsafe</code>类的方法，<code>Unsafe</code>类中的所有方法都是<code>native</code>修饰的，也就是说<code>Unsafe</code>类中的方法都直接调用操作系统底层资源执行相应任务。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">UnsafeExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Unsafe</span><span class="w"> </span><span class="n">unsafe</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Field</span><span class="w"> </span><span class="n">field</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Unsafe</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;theUnsafe&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">field</span><span class="p">.</span><span class="na">setAccessible</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">unsafe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Unsafe</span><span class="p">)</span><span class="w"> </span><span class="n">field</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">valueOffset</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">objectFieldOffset</span><span class="p">(</span><span class="n">UnsafeExample</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;value&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">current</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">unsafe</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="实现原理">实现原理</h3>
+<p>以<code>AtomicInteger</code>原子整型类为例，来看一下CAS实现原理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">().</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">compareAndSet
+</span></span><span class="line"><span class="cl">    --&gt; unsafe.compareAndSwapInt
+</span></span><span class="line"><span class="cl">    ---&gt; unsafe.compareAndSwapInt
+</span></span><span class="line"><span class="cl">    --&gt; (C++) cmpxchg
+</span></span></code></pre></div><p><code>AtomicInteger</code>内部方法都是基于<code>Unsafe</code>类实现的。</p>
+<blockquote>
+<p><code>Unsafe</code>是CAS的核心类，Java无法直接访问底层操作系统，而是通过<code>native</code>方法来访问。不过尽管如此，JVM还是开了一个后门，JDK中有一个类<code>Unsafe</code>，它提供了硬件级别的原子操作。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// setup to use Unsafe.compareAndSwapInt for updates</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Unsafe</span><span class="w"> </span><span class="n">unsafe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Unsafe</span><span class="p">.</span><span class="na">getUnsafe</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">valueOffset</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">objectFieldOffset</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">(</span><span class="n">AtomicInteger</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;value&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="n">ex</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSet</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expect</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">update</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">expect</span><span class="p">,</span><span class="w"> </span><span class="n">update</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>compareAndSwapInt</code>方法参数：</p>
+<ul>
+<li><code>this</code>：<code>Unsafe</code>对象本身，需要通过这个类来获取 <code>value</code> 的内存偏移地址；</li>
+<li><code>valueOffset</code>： <code>valueOffset</code> 表示的是变量值在内存中的偏移地址，因为 <code>Unsafe</code> 就是根据内存偏移地址获取数据的原值的。</li>
+<li><code>expect</code>：当前预期的值；</li>
+<li><code>update</code>：要设置的新值；</li>
+</ul>
+<p>继续向底层深入，就会看到<code>Unsafe</code>类中的一些其他方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Unsafe</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapObject</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapLong</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>对应查看<code>openjdk</code>的<code>hotspot</code>源码，<code>src/share/vm/prims/unsafe.cpp</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">#define FN_PTR(f) CAST_FROM_FN_PTR(void*, &amp;f)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapObject&#34;, CC&#34;(&#34;OBJ&#34;J&#34;OBJ&#34;&#34;OBJ&#34;)Z&#34;,  FN_PTR(Unsafe_CompareAndSwapObject)},
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapInt&#34;,  CC&#34;(&#34;OBJ&#34;J&#34;&#34;I&#34;&#34;I&#34;&#34;)Z&#34;,      FN_PTR(Unsafe_CompareAndSwapInt)},
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapLong&#34;, CC&#34;(&#34;OBJ&#34;J&#34;&#34;J&#34;&#34;J&#34;&#34;)Z&#34;,      FN_PTR(Unsafe_CompareAndSwapLong)},
+</span></span></code></pre></div><p>最终在<code>hotspot</code>源码实现<code>/src/share/vm/runtime/Atomic.cpp</code>中都会调用统一的<code>cmpxchg</code>函数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-cpp" data-lang="cpp"><span class="line"><span class="cl"><span class="n">jbyte</span> <span class="n">Atomic</span><span class="o">::</span><span class="n">cmpxchg</span><span class="p">(</span><span class="n">jbyte</span> <span class="n">exchange_value</span><span class="p">,</span> <span class="k">volatile</span> <span class="n">jbyte</span><span class="o">*</span><span class="n">dest</span><span class="p">,</span> <span class="n">jbyte</span> <span class="n">compare_value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">     <span class="n">assert</span> <span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="n">jbyte</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span><span class="p">,</span><span class="s">&#34;assumption.&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="n">uintptr_t</span> <span class="n">dest_addr</span> <span class="o">=</span> <span class="p">(</span><span class="n">uintptr_t</span><span class="p">)</span> <span class="n">dest</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">uintptr_t</span> <span class="n">offset</span> <span class="o">=</span> <span class="n">dest_addr</span> <span class="o">%</span> <span class="k">sizeof</span><span class="p">(</span><span class="n">jint</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="k">volatile</span> <span class="n">jint</span><span class="o">*</span><span class="n">dest_int</span> <span class="o">=</span> <span class="p">(</span> <span class="k">volatile</span> <span class="n">jint</span><span class="o">*</span><span class="p">)(</span><span class="n">dest_addr</span> <span class="o">-</span> <span class="n">offset</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 对象当前值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jint</span> <span class="n">cur</span> <span class="o">=</span> <span class="o">*</span><span class="n">dest_int</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 当前值cur的地址
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jbyte</span> <span class="o">*</span> <span class="n">cur_as_bytes</span> <span class="o">=</span> <span class="p">(</span><span class="n">jbyte</span> <span class="o">*</span><span class="p">)</span> <span class="p">(</span> <span class="o">&amp;</span> <span class="n">cur</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// new_val地址
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jint</span> <span class="n">new_val</span> <span class="o">=</span> <span class="n">cur</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">jbyte</span> <span class="o">*</span> <span class="n">new_val_as_bytes</span> <span class="o">=</span> <span class="p">(</span><span class="n">jbyte</span> <span class="o">*</span><span class="p">)</span> <span class="p">(</span> <span class="o">&amp;</span> <span class="n">new_val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">      <span class="c1">// new_val存exchange_value，后面修改则直接从new_val中取值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">new_val_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">=</span> <span class="n">exchange_value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 比较当前值与期望值，如果相同则更新，不同则直接返回
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="k">while</span> <span class="p">(</span><span class="n">cur_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">==</span> <span class="n">compare_value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="c1">// 调用汇编指令cmpxchg执行CAS操作，期望值为cur，更新值为new_val
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>         <span class="n">jint</span> <span class="n">res</span> <span class="o">=</span> <span class="n">cmpxchg</span><span class="p">(</span><span class="n">new_val</span><span class="p">,</span> <span class="n">dest_int</span><span class="p">,</span> <span class="n">cur</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">         <span class="k">if</span> <span class="p">(</span><span class="n">res</span> <span class="o">==</span> <span class="n">cur</span><span class="p">)</span> <span class="k">break</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">cur</span> <span class="o">=</span> <span class="n">res</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">new_val</span> <span class="o">=</span> <span class="n">cur</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">new_val_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">=</span> <span class="n">exchange_value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="p">}</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 返回当前值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="k">return</span> <span class="n">cur_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">];</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>从上述源码可以看出CAS操作通过CPU提供的原子指令<code>cmpxchg</code>来实现无锁操作，这个指令会保证在多个处理器同时访问和修改数据时的正确性。</p>
+<p>CPU处理器速度远远大于在主内存中的速度，为了加快访问速度，现代CPU引入了多级缓存，如L1、L2、L3 级别的缓存，这些缓存离CPU越近就越快。
+这些缓存存储了频繁使用的数据，但在多处理器环境中，缓存的一致性成为了下一个问题。
+当CPU中某个处理器对缓存中的共享变量进行了操作后，其他处理器会有个嗅探机制。即将其他处理器共享变量的缓存失效，当其他线程读取时会重新从主内存中读取最新的数据，这是基于<code>MESI</code>缓存一致性协议来实现的。</p>
+<p>在多线程环境中，CAS就是比较当前线程工作内存中的值和主内存中的值，如果相同则执行规定操作，否则继续比较，直到主内存和当前线程工作内存中的值一致为止。
+每个CPU核心都有自己的缓存，用于存储频繁访问的数据。当一个线程在某个CPU核心上修改了共享变量的值时，其他CPU核心上缓存中的该变量会被标记为无效，这样其他线程再访问该变量时就会重新从主内存中获取最新值，从而保证了数据的一致性。
+CAS操作通过CPU提供的原子指令<code>cmpxchg</code>来比较和交换变量的值，它的原子性和线程安全性依赖于CPU的硬件支持和缓存一致性协议的保障。</p>
+<p><img alt="CPU多级缓存" src="/iblog/posts/annex/images/essays/CPU%E5%A4%9A%E7%BA%A7%E7%BC%93%E5%AD%98.jpg"></p>
+<p>所以当执行CAS方法时，读取变量当前的值，并与预期值进行比较。如果变量的当前值等于预期值，则将其更新为新值。如果变量的当前值不等于预期值，则不执行更新操作。
+注意CAS操作是原子的，即整个过程不会被其他线程打断。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="cas问题">CAS问题</h3>
+<ul>
+<li>循环时间长开销：CAS操作在失败时会进行自旋重试，即反复尝试CAS操作直到成功或达到一定的重试次数。自旋次数过多可能会影响性能，因此在使用CAS时需要权衡自旋次数和性能之间的关系。
+例如<code>getAndAddInt</code>方法执行，如果CAS失败会一直会进行尝试，如果CAS长时间不成功，可能会给CPU带来很大的开销。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>原子性问题：CAS操作本身是原子的，即在执行过程中不会被中断。但需要注意的是，CAS操作是针对单个变量的原子操作，而对于判断某个变量的值并根据结果进行另外的操作，需要额外的控制确保整体的原子性。
+这个时候就可以用锁来保证原子性，但是Java从1.5开始JDK提供了<code>AtomicReference</code>类来保证引用对象之间的原子性，可以把多个变量放在一个对象里来进行CAS操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AtomicReferenceSimpleExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DataObject</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">var2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="nf">DataObject</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">var2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 AtomicReference 实例，并初始化为一个 DataObject 对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">DataObject</span><span class="o">&gt;</span><span class="w"> </span><span class="n">atomicRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">DataObject</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Initial&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行 CAS 操作，修改 DataObject 对象的属性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">updateAndGet</span><span class="p">(</span><span class="n">data</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="p">.</span><span class="na">setVar1</span><span class="p">(</span><span class="n">data</span><span class="p">.</span><span class="na">getVar1</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="p">.</span><span class="na">setVar2</span><span class="p">(</span><span class="s">&#34;Updated&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取修改后的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DataObject</span><span class="w"> </span><span class="n">updatedObject</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Updated var1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">updatedObject</span><span class="p">.</span><span class="na">getVar1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Updated var2: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">updatedObject</span><span class="p">.</span><span class="na">getVar2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>ABA问题：ABA问题指的是，在CAS操作过程中，如果一个变量的值从A变成了B，然后再变回A，那么CAS操作会错误地认为变量的值未改变过。
+比如，线程1从内存位置V取出A，线程2同时也从内存取出A，并且线程2进行一些操作将值改为B，然后线程2又将V位置数据改成A，这时候线程1进行CAS操作发现内存中的值依然时A，然后线程1操作成功。尽管线程1的CAS操作成功，但是不代表这个过程没有问题。
+简而言之就是只比较结果，不比较过程。解决ABA问题的常见方法是使用版本号或者标记来跟踪变量的变化。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ABASolutionWithVersion</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始值为100，初始版本号为0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicStampedReference</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">atomicRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicStampedReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">100</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">stampHolder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// 用于获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w"> </span><span class="c1">// 期望值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">200</span><span class="p">;</span><span class="w"> </span><span class="c1">// 新值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟一个线程进行 ABA 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">getStamp</span><span class="p">();</span><span class="w"> </span><span class="c1">// 获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// 修改值和版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 再次修改回原值和新版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 其他线程进行 CAS 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">getStamp</span><span class="p">();</span><span class="w"> </span><span class="c1">// 获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;CAS Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出CAS操作结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
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+
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+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e6%8d%ae%e7%bb%93%e6%9e%84">
+                    数据结构
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+                <a class="nav-link text-left" href="#%e5%8d%95%e5%90%91%e9%93%be%e8%a1%a8">
+                    单向链表
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+            </li>
+            
+            
+        </ul>
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+        </ul>
+        
+        </ul>
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+        </ul>
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+        
+        
+        
+        
+        
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+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
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+        <ul class="nav">
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8c%e5%90%91%e9%93%be%e8%a1%a8">
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+            
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+            
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+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a0%88">
+                    栈
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a0%88%e5%ae%9e%e7%8e%b0%e4%b8%ad%e7%bc%80%e8%a1%a8%e8%be%be%e5%bc%8f">
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a0%88%e5%ae%9e%e7%8e%b0%e5%90%8e%e7%bc%80%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    栈实现后缀表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ad%e7%bc%80%e8%a1%a8%e8%be%be%e5%bc%8f%e8%bd%ac%e5%90%8e%e7%bc%80%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    中缀表达式转后缀表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%93%88%e5%b8%8c%e8%a1%a8">
+                    哈希表
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%8c%e5%8f%89%e6%a0%91">
+                    二叉树
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%8c%e5%8f%89%e6%a0%91%e7%9a%84%e9%81%8d%e5%8e%86%e5%8f%8a%e6%9f%a5%e6%89%be">
+                    二叉树的遍历及查找
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%8c%e5%8f%89%e6%a0%91%e7%9a%84%e5%88%a0%e9%99%a4">
+                    二叉树的删除
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%a1%ba%e5%ba%8f%e5%ad%98%e5%82%a8%e4%ba%8c%e5%8f%89%e6%a0%91">
+                    顺序存储二叉树
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%b4%a2%e5%8c%96%e4%ba%8c%e5%8f%89%e6%a0%91">
+                    线索化二叉树
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%93%88%e5%a4%ab%e6%9b%bc%e6%a0%91">
+                    哈夫曼树
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%8c%e5%8f%89%e6%8e%92%e5%ba%8f%e6%a0%91">
+                    二叉排序树
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b9%b3%e8%a1%a1%e4%ba%8c%e5%8f%89%e6%a0%91">
+                    平衡二叉树
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%9a%e8%b7%af%e6%9f%a5%e6%89%be%e6%a0%91">
+                    多路查找树
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#2-3%e6%a0%91">
+                    2-3树
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+        
+        </ul>
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+        <ul class="nav">
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+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#b%e6%a0%91-2">
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+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9b%be">
+                    图
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ae%97%e6%b3%95">
+                    算法
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ae%97%e6%b3%95%e5%a4%8d%e6%9d%82%e5%ba%a6">
+                    算法复杂度
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
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+            
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+                <a class="nav-link text-left" href="#%e6%97%b6%e9%97%b4%e5%a4%8d%e6%9d%82%e5%ba%a6">
+                    时间复杂度
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%a9%ba%e9%97%b4%e5%a4%8d%e6%9d%82%e5%ba%a6">
+                    空间复杂度
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
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+                    递归
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+                <a class="nav-link text-left" href="#%e8%bf%b7%e5%ae%ab%e5%9b%9e%e6%ba%af">
+                    迷宫回溯
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+                <a class="nav-link text-left" href="#%e5%85%ab%e7%9a%87%e5%90%8e%e9%97%ae%e9%a2%98">
+                    八皇后问题
+                </a>
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e5%ba%8f%e7%ae%97%e6%b3%95">
+                    排序算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%92%e6%b3%a1%e6%8e%92%e5%ba%8f">
+                    冒泡排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%89%e6%8b%a9%e6%8e%92%e5%ba%8f">
+                    选择排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8f%92%e5%85%a5%e6%8e%92%e5%ba%8f">
+                    插入排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%8c%e5%b0%94%e6%8e%92%e5%ba%8f">
+                    希尔排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bf%ab%e9%80%9f%e6%8e%92%e5%ba%8f">
+                    快速排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
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+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bd%92%e5%b9%b6%e6%8e%92%e5%ba%8f">
+                    归并排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
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+        
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+        
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e6%95%b0%e6%8e%92%e5%ba%8f">
+                    基数排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a0%86%e6%8e%92%e5%ba%8f">
+                    堆排序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9f%a5%e6%89%be%e7%ae%97%e6%b3%95">
+                    查找算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e6%80%a7%e6%9f%a5%e6%89%be">
+                    线性查找
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%8c%e5%88%86%e6%9f%a5%e6%89%be">
+                    二分查找
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8f%92%e5%80%bc%e6%9f%a5%e6%89%be">
+                    插值查找
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%90%e6%b3%a2%e9%82%a3%e5%a5%91%e6%9f%a5%e6%89%be">
+                    斐波那契查找
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%93%88%e5%a4%ab%e6%9b%bc%e7%bc%96%e7%a0%81">
+                    哈夫曼编码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e6%b2%bb%e7%ae%97%e6%b3%95">
+                    分治算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8a%a8%e6%80%81%e8%a7%84%e5%88%92%e7%ae%97%e6%b3%95">
+                    动态规划算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#kmp%e7%ae%97%e6%b3%95">
+                    KMP算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b4%aa%e5%bf%83%e7%ae%97%e6%b3%95">
+                    贪心算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%99%ae%e9%87%8c%e5%a7%86%e7%ae%97%e6%b3%95">
+                    普里姆算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%8b%e9%b2%81%e6%96%af%e5%8d%a1%e5%b0%94%e7%ae%97%e6%b3%95">
+                    克鲁斯卡尔算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%aa%e6%9d%b0%e6%96%af%e7%89%b9%e6%8b%89%e7%ae%97%e6%b3%95">
+                    迪杰斯特拉算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%97%e6%b4%9b%e4%bc%8a%e5%be%b7%e7%ae%97%e6%b3%95">
+                    弗洛伊德算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%a9%ac%e8%b8%8f%e6%a3%8b%e7%9b%98%e7%ae%97%e6%b3%95">
+                    马踏棋盘算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
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+                        <h2 id="post_single_title">数据结构与算法详解</h2>
+                        <span id="post_page_title_date" class="date">2021.12.10</span>
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+                    <div class="post_content markdown"><h2 id="数据结构">数据结构</h2>
+<p>数据结构是一门研究组织数据方式的学科，有了编程语言也就有了数据结构，学好数据结构可以编写出更有效率的代码。数据结构是算法的基础，想要学好算法，就必须把数据结构学到位。</p>
+<p>数据结构包括：线性结构、非线性结构。</p>
+<p>线性结构作为最常用的数据结构，其特点是数据元素之间存在一对一的线性存储关系。线性结构有两种不同的存储结构，即顺序存储和链式存储。顺序存储的线性表被称为顺序表，顺序表中存储元素的地址是连续的；链式存储的线性表被称为链表，链表中存储元素的地址不一定是连续的，元素结点中存放数据元素以及相邻元素地址信息。</p>
+<p>常见的线性结构有：数组、链表、队列、栈；常见非线性结构有：多维数组、广义表、树结构、图结构。</p>
+<h3 id="稀疏数组">稀疏数组</h3>
+<p>使用稀疏数组可以用来压缩数据。稀疏数组的第一行依次记录原数组一共有几行几列，有多少个不为零的值，之后的每行记录原数组中不为零的值所在的行数、列数以及数组中元素该值。如图所示：</p>
+<p><img alt="数据结构与算法-001" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-001.png"></p>
+<p>二维数组转稀疏数组</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">TwoDimensionArrayDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 将二维数组转换为稀疏数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="nf">twoDimensionArrayToSparseArray</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">array</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 记录棋盘中有效值的数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">sum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">column</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ints</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">array</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">column</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ints</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">item</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">ints</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">item</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">sum</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 创建稀疏数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">sparseArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">3</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">row</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">column</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sum</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 给稀疏数组赋值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">array</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">array</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">array</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">count</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">count</span><span class="o">][</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">j</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">count</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;稀疏数组====》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">sparseArray</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%d\t%d\t%d\t\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">1</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">sparseArray</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>稀疏数组转二维数组</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">TwoDimensionArrayDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 稀疏数组转二维数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="nf">sparseArrayToTwoDimensionArray</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">sparseArray</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">toTwoDimensionArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">0</span><span class="o">]][</span><span class="n">sparseArray</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">1</span><span class="o">]]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 给二维数组赋值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">sparseArray</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">toTwoDimensionArray</span><span class="o">[</span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">0</span><span class="o">]][</span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">1</span><span class="o">]]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sparseArray</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;二维数组====》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">toTwoDimensionArray</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">row</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%d\t&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">data</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">toTwoDimensionArray</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="队列">队列</h3>
+<p>队列是一个有序列表，可以使用数组或链表来实现。队列遵循先入先出的原则。即，先存入队列的数据，要先取出。后存入的要后取出。</p>
+<p>使用数组模拟队列示意图：</p>
+<p><img alt="数据结构与算法-002" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-002.png"></p>
+<p>数组模拟单向队列</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayQueue</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 队列容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存队列中的数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 头部指针</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">front</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 尾部指针</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="nf">ArrayQueue</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">capacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">capacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">capacity</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">front</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">rear</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isFull</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">capacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isFull</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列已经满了，不能在继续添加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[++</span><span class="n">rear</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">get</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列为空，不能获取元素&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">arr</span><span class="o">[++</span><span class="n">front</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示队列的所有数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">show</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列空的，没有数据~~&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始遍历队列：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;arr[%d]=%d\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示队列的头数据， 注意不是取出数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">peek</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;队列空的，没有数据~~&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">front</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>数组模拟环形队列</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kd">class</span> <span class="nc">CircleArrayQueue</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 队列容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存队列中的数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 头部指针</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">front</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 尾部指针</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="nf">CircleArrayQueue</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">capacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">capacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">capacity</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rear</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isFull</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 此处+1 是因为存储元素从0算起</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">rear</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="w">  </span><span class="o">==</span><span class="w"> </span><span class="n">front</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isFull</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列已经满了，不能在继续添加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">rear</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">rear</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">rear</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">get</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列为空，不能获取元素&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">front</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">front</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">front</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示队列的所有数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">show</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;队列空的，没有数据~~&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始遍历队列：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">front</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">((</span><span class="n">rear</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">capacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">front</span><span class="p">)</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">);</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;arr[%d]=%d\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示队列的头数据， 注意不是取出数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">peek</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;队列空的，没有数据~~&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">front</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="链表">链表</h3>
+<p>链表属于线性结构，存储空间不连续。</p>
+<p>链表特点：</p>
+<ul>
+<li>链表是以节点的方式来存储，是链式存储；data 域存放数据，next 域指向下一个节点；</li>
+<li>链表分带头节点的链表和没有头节点的链表，根据实际的需求来确定；</li>
+</ul>
+<p><img alt="数据结构与算法-003" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-003.png"></p>
+<h4 id="单向链表">单向链表</h4>
+<p>操作单向链表：对于插入、删除操作，只能定位至待操作节点的前一个节点，如果定位至当前节点，那么其上一个节点的信息便会丢失。</p>
+<p>单向链表，链表的增、删、查、改</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">SingleLinkedList</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 头结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">headNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 指向下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 退出循环意味着tmpNode.next == null 即找到最后一个结点了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 顺序添加</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addByOrder</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将新插入的结点num跟链表中已经存在的num进行比较，如果 &lt; 链表中的结点 则说明找到了该位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果num相同则不能添加</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">flag</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;需要添加的结点编号：%d已经存在了&#34;</span><span class="p">,</span><span class="n">node</span><span class="p">.</span><span class="na">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历除了头结点外的所有结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;链表为空！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">tmpNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 指向下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;num=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>反转单向链表</p>
+<p><img alt="数据结构与算法-004" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-004.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">LinkedListDemo</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 反转链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">reserve</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">head</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Node</span><span class="w"> </span><span class="n">reserve</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Node</span><span class="w"> </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 遍历链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 遍历原来的链表，每遍历一个节点，就将其取出，并放在新的链表reverseHead 的最前端</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">cur</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存当前结点的下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cur</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将cur的下一个节点指向新的链表的最前端（覆盖掉）保证将最新的结点放到reseve的最前面</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cur</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reserve</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将cur 连接到新的链表上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">reserve</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cur</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将之前保存好的结点赋值给当前结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>利用栈逆序打印单向链表</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">LinkedListDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">reservePrint</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">head</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">nodes</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">tmp</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 从stack中取出结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">nodes</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">nodes</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="双向链表">双向链表</h4>
+<p>对比单向链表：</p>
+<ul>
+<li>单向链表，查找的方向只能是一个方向，而双向链表可以向前或者向后查找；</li>
+<li>单向链表不能自我删除，需要靠辅助节点，而双向链表，则可以自我删除；</li>
+</ul>
+<p><img alt="数据结构与算法-005" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-005.png"></p>
+<p>双向链表，增、删、改、查</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">DoubleLinkedList</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 头结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">headNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">getHeadNode</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">headNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 指向下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 退出循环意味着tmpNode.next == null 即找到最后一个结点了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">node</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 双向链表修改</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">headNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmp</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 双向链表删除</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;链表为空，无法删除！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">num</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmp</span><span class="p">.</span><span class="na">prev</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 最后一个结点的next 为null null.pre会出现空指针异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">prev</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历除了头结点外的所有结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">headNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;链表为空！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpNode</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">tmpNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 指向下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">prev</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;num=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="约瑟夫问题">约瑟夫问题</h4>
+<blockquote>
+<p>约瑟夫问题为：设编号为 1，2，…n的n个人围坐一圈，约定编号为 k（1&lt;=k&lt;=n） 的人从 1 开始报数,数到 m 的那个人出列，它的下一位又从 1 开始报数，数到 m 的那个人又出列， 依次类推，直到所有人出列为止，由此产生一个出队编号的序列。</p>
+</blockquote>
+<p>用一个不带头结点的循环链表来处理约瑟夫问题：先构成一个有 n 个结点的单循环链表，然后由 k 结点起从 1 开始计数，计到 m 时，对应结点从链表中删除，然后再从被删除结点的下一个结点又从 1 开始计数，直到最后一个结点从链表中删除算法结束。</p>
+<p><img alt="数据结构与算法-006" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-006.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">JoesphSingletonLinkedList</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 向单向链表添加数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">nums</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nums</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;nums的值不正确&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">nums</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">first</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">cur</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">node</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">cur</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历单向循环链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;当前结点为：%d\n&#34;</span><span class="p">,</span><span class="n">tmp</span><span class="p">.</span><span class="na">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">first</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 约瑟夫问题</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">joseph</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">startNum</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">countNum</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">sum</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">startNum</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">sum</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">startNum</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">countNum</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;输入的参数不正确！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建辅助指针，将该指针指向 first 的前一个</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">helper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">first</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">helper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将first 和 help指针循环 （startNum - 1）次；因为从startNum开始，需要减一</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">startNum</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">helper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当环形链表中只存在一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">first</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">helper</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 因为是环形链表，所以需要循环挨个出链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">countNum</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">helper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当前 first 就是出圈的结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;当前出队列的结点编号为：%d\n&#34;</span><span class="p">,</span><span class="n">first</span><span class="p">.</span><span class="na">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">helper</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;最后的结点为：%d\n&#34;</span><span class="p">,</span><span class="n">first</span><span class="p">.</span><span class="na">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;num=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="栈">栈</h3>
+<p>栈的英文为stack，是一个先入后出(FILO-First In Last Out)的有序列表，最先放入栈中元素在栈底，最后放入的元素在栈顶，而删除元素刚好相反，最后放入的元素最先删除，最先放入的元素最后删除。</p>
+<p>栈是限制线性表中元素的插入和删除只能在线性表的同一端进行的一种特殊线性表。允许插入和删除的一端，为变化的一端，称为栈顶(Top)，另一端为固定的一端，称为栈底(Bottom)。</p>
+<p>下图是出栈和入栈</p>
+<p><img alt="数据结构与算法-007" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-007.png"></p>
+<p>栈的应用场景：</p>
+<ul>
+<li>子程序的调用： 在跳往子程序前， 会先将下个指令的地址存到堆栈中， 直到子程序执行完后再将地址取出， 以回到原来的程序中；</li>
+<li>处理递归调用： 和子程序的调用类似， 只是除了储存下一个指令的地址外， 也将参数、 区域变量等数据存入栈中；</li>
+<li>表达式的转换：中缀表达式转后缀表达式与求值；</li>
+<li>二叉树的遍历；</li>
+<li>图形的深度优先(depth 一 first)搜索法；</li>
+</ul>
+<p>数组模拟栈</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">ArrayStack</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">top</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">stack</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ArrayStack</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[</span><span class="n">size</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">top</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isFull</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">top</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">top</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 入栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">push</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isFull</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;栈已经满了，不能继续添加！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">top</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">stack</span><span class="o">[</span><span class="n">top</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 出栈操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">pop</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;栈已经为空，不能继续pop&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">T</span><span class="w"> </span><span class="n">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="p">)</span><span class="k">this</span><span class="p">.</span><span class="na">stack</span><span class="o">[</span><span class="n">top</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">top</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">val</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;栈为空不能继续遍历！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;遍历栈==》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">top</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&gt;=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">--</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">stack</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="栈实现中缀表达式">栈实现中缀表达式</h4>
+<p><img alt="数据结构与算法-008" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-008.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">CalcInfixExpressions</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calcInfixExpressions</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">expression</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 定义变量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">chars</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">expression</span><span class="p">.</span><span class="na">toCharArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">chars</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">numStack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">Character</span><span class="o">&gt;</span><span class="w"> </span><span class="n">oprStack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">chars</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断字符是否为数字,如果是数字就放入数栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Character</span><span class="p">.</span><span class="na">isDigit</span><span class="p">(</span><span class="n">ch</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 接收多位数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ch</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 从当前字符开始遍历，如果下一位字符不是数字，则将该数字压入栈中并退出循环，如果是数字，则需要拼接起来</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Character</span><span class="p">.</span><span class="na">isDigit</span><span class="p">(</span><span class="n">expression</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">String</span><span class="w"> </span><span class="n">strNum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">expression</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">parseInt</span><span class="p">(</span><span class="n">strNum</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">j</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">num</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">48</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">numStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 非数字，即运算符,如果为空直接加入栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oprStack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">oprStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">ch</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果运算符栈不为空，需要比较运算符的优先级，如果当前运算符的优先级 &lt;= 栈顶的运算符的优先级，需要计算在压入栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oprPriority</span><span class="p">(</span><span class="n">oprStack</span><span class="p">.</span><span class="na">peek</span><span class="p">())</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">oprPriority</span><span class="p">(</span><span class="n">ch</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">numStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">calc</span><span class="p">(</span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="w"> </span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="w"> </span><span class="n">oprStack</span><span class="p">.</span><span class="na">pop</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将字符压入操作符栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oprStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">ch</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将处理好的数据按照顺序弹出，进行计算，得到数栈中最后一个数就是最终的结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">oprStack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">numStack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">calc</span><span class="p">(</span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="w"> </span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="w"> </span><span class="n">oprStack</span><span class="p">.</span><span class="na">pop</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">numStack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取字符的优先级</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">oprPriority</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ch</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">&#39;*&#39;</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">&#39;/&#39;</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ch</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calc</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num1</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">num2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">num1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;*&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">num2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;/&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">num1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="栈实现后缀表达式">栈实现后缀表达式</h4>
+<p>后缀表达式又称逆波兰表达式，与前缀表达式相似，只是运算符位于操作数之后。例如： (3+4)×5-6 对应的后缀表达式就是 3 4 + 5 × 6 –</p>
+<p>思路：从左至右扫描表达式，遇到数字时，将数字压入堆栈，遇到运算符时，弹出栈顶的两个数，用运算符对它们做相应的计算（次顶元素 和 栈顶元素），并将结果入栈；重复上述过程直到表达式最右端，最后运算得出的值即为表达式的结果。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">PolandNotation</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算后缀表达式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calcSuffixExceptions</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">suffixExpres</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">chars</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">suffixExpres</span><span class="p">.</span><span class="na">toCharArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">chars</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">suffixExpres</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">Character</span><span class="p">.</span><span class="na">isDigit</span><span class="p">(</span><span class="n">ch</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">calc</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">(),</span><span class="n">ch</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">res</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">ch</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">48</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calc</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">num1</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">num2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">num1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;*&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">num2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;/&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">num1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">default</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;运算符有误&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="中缀表达式转后缀表达式">中缀表达式转后缀表达式</h4>
+<p><img alt="数据结构与算法-009" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-009.png"></p>
+<p>中缀表达式转后缀表达式代码实现</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">InfixToPolandNotation</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 根据ASCII 判断是否为数字</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isNumber</span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">&gt;=</span><span class="n">48</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">57</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取字符的优先级</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">oprPriority</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">opr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">opr</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;*&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">opr</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">opr</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;+&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">opr</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;-&#34;</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将中缀表达式字符串转成中缀表达式集合</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">toInfixExceptionList</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">number</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="w"> </span><span class="n">c</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">length</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isNumber</span><span class="p">((</span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">index</span><span class="p">)))){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">c</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">isNumber</span><span class="p">((</span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">index</span><span class="p">)))){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">number</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">number</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">list</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将中缀表达式转为后缀表达式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">infixExpressionToSuffixExpress</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">finalList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">item</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果是数字或者为（ 将该值压入栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">item</span><span class="p">.</span><span class="na">matches</span><span class="p">(</span><span class="s">&#34;\\d+&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">finalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">item</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;(&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果是 ）则将 ()中间的数重新压入list中，最后将 ） 移除掉</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">item</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;)&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">().</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;(&#34;</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">finalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 如果不是 ）则判断运算符的优先级，如果符号栈栈顶的优先级 &gt;= 当前的优先级，则将该运算符加入数字栈中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">oprPriority</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">oprPriority</span><span class="p">(</span><span class="n">item</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">finalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将operStack中剩余的运算符依次弹出并加入tempList</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">finalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">finalList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>完整逆波兰表达式代码，支持小数、支持消除空格</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReversePolishMultiCalc</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">	 </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 匹配 + - * / ( ) 运算符
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">SYMBOL</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;\\+|-|\\*|/|\\(|\\)&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">LEFT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;(&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">RIGHT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;)&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">ADD</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;+&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">MINUS</span><span class="o">=</span><span class="w"> </span><span class="s">&#34;-&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">TIMES</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;*&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">DIVISION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 加減 + -
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">LEVEL_01</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 乘除 * /
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">LEVEL_02</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 括号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">synchronizedList</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 去除所有空白符
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">replaceAllBlank</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// \\s+ 匹配任何空白字符，包括空格、制表符、换页符等等, 等价于[ \f\n\r\t\v]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">replaceAll</span><span class="p">(</span><span class="s">&#34;\\s+&#34;</span><span class="p">,</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 判断是不是数字 int double long float
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isNumber</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Pattern</span><span class="w"> </span><span class="n">pattern</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern</span><span class="p">.</span><span class="na">compile</span><span class="p">(</span><span class="s">&#34;^[-\\+]?[.\\d]*$&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">pattern</span><span class="p">.</span><span class="na">matcher</span><span class="p">(</span><span class="n">s</span><span class="p">).</span><span class="na">matches</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 判断是不是运算符
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isSymbol</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">matches</span><span class="p">(</span><span class="n">SYMBOL</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 匹配运算等级
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calcLevel</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="s">&#34;+&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;-&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">LEVEL_01</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="s">&#34;*&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;/&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">LEVEL_02</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 匹配
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">doMatch</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">trim</span><span class="p">()))</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;data is empty&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="o">!</span><span class="n">isNumber</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">0</span><span class="p">)</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">))</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;data illeagle,start not with a number&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">replaceAllBlank</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">each</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">isSymbol</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">each</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">//栈为空，(操作符，或者 操作符优先级大于栈顶优先级 &amp;&amp; 操作符优先级不是( )的优先级 及是 ) 不能直接入栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">LEFT</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="o">||</span><span class="w"> </span><span class="p">((</span><span class="n">calcLevel</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">()))</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">each</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="w"> </span><span class="o">!</span><span class="n">stack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">//栈非空，操作符优先级小于等于栈顶优先级时出栈入列，直到栈为空，或者遇到了(，最后操作符入栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">stack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">each</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())</span><span class="w"> </span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="p">(</span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">data</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="n">each</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="n">RIGHT</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">each</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// ) 操作符，依次出栈入列直到空栈或者遇到了第一个)操作符，此时)出栈</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">stack</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">LEVEL_HIGH</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="p">(</span><span class="n">LEVEL_HIGH</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">calcLevel</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">peek</span><span class="p">())){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">data</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">;</span><span class="w">    </span><span class="c1">//前一个运算符的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="o">-</span><span class="n">1</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">isSymbol</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">)</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">)</span><span class="w"> </span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">each</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">start</span><span class="p">,</span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">start</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="p">(</span><span class="n">isNumber</span><span class="p">(</span><span class="n">each</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">data</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">each</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;data not match number&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//如果栈里还有元素，此时元素需要依次出栈入列，可以想象栈里剩下栈顶为/，栈底为+，应该依次出栈入列，可以直接翻转整个stack 添加到队列</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Collections</span><span class="p">.</span><span class="na">reverse</span><span class="p">(</span><span class="n">stack</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">data</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">stack</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">data</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 算出结果
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Double</span><span class="w"> </span><span class="nf">doCalc</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Double</span><span class="w"> </span><span class="n">d</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0d</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="n">list</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">d</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">d</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">isSymbol</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">))){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Double</span><span class="w"> </span><span class="n">d1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">doTheMath</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">),</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">),</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list1</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list1</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">i</span><span class="o">-</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list1</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">i</span><span class="o">-</span><span class="n">2</span><span class="p">,</span><span class="n">d1</span><span class="o">+</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list1</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">subList</span><span class="p">(</span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">doCalc</span><span class="p">(</span><span class="n">list1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">d</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 运算
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s1
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param s2
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param symbol
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Double</span><span class="w"> </span><span class="nf">doTheMath</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s1</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">s2</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">symbol</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Double</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">symbol</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">ADD</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">MINUS</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s1</span><span class="p">)</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">TIMES</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s1</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">DIVISION</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s1</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">default</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//String math = &#34;9+(3-1)*3+10/2&#34;;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">math</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;12.8 + (2 - 3.55)*4+10/5.0&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">doCalc</span><span class="p">(</span><span class="n">doMatch</span><span class="p">(</span><span class="n">math</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="哈希表">哈希表</h3>
+<p>哈希表也叫散列表，是根据关键码值(Key value)而直接进行访问的数据结构。</p>
+<p>它通过把关键码值映射到表中一个位置来访问记录，以加快查找的速度。这个映射函数叫做散列函数，存放记录的数组叫做散列表。</p>
+<p>手写模拟哈希表</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HashTableDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashTab</span><span class="w"> </span><span class="n">hashTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashTab</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;zs&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;lx&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;ex&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;as&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">node5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;we&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;添加元素后===》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">hashTab</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;删除后===》&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashTab</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">hashTab</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HashTab</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">NodeList</span><span class="o">[]</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">HashTab</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NodeList</span><span class="o">[</span><span class="n">size</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">nodes</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NodeList</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">put</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 放入hash表的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">nodes</span><span class="o">[</span><span class="n">getPosition</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">id</span><span class="p">)</span><span class="o">]</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">nodes</span><span class="o">[</span><span class="n">getPosition</span><span class="p">(</span><span class="n">id</span><span class="p">)</span><span class="o">]</span><span class="p">.</span><span class="na">delete</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getPosition</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;HashTab{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;nodes=\n&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;}&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">NodeList</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 头结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 头结点不要动，将添加的结点放到链表的最后一个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 当下一个结点等于null时，找到最后一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 展示当前链表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前链表为空&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 辅助结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">tmp</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 根据ID删除链表中的某个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">delete</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前链表为空&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断删除的是否是头结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">preNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">curNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">preNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">curNode</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">curNode</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">preNode</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">curNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;删除成功，删除的是: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">curNode</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;,&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">curNode</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">curNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">preNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">preNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">curNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">curNode</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;删除失败，节点不存在&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;NodeList{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;head=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;}\n&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;id=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, next=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;}&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="二叉树">二叉树</h3>
+<blockquote>
+<p>二叉树（Binary tree）是树形结构的一个重要类型。许多实际问题抽象出来的数据结构往往是二叉树形式，即使是一般的树也能简单地转换为二叉树，而且二叉树的存储结构及其算法都较为简单，因此二叉树显得特别重要。二叉树特点是每个结点最多只能有两棵子树，且有左右之分。</p>
+</blockquote>
+<p>二叉树是n个有限元素的集合，该集合或者为空、或者由一个称为根的元素及两个不相交的、被分别称为左子树和右子树的二叉树组成，是有序树。当集合为空时，称该二叉树为空二叉树。在二叉树中，一个元素也称作一个结点。</p>
+<p>如果该二叉树的所有叶子节点都在最后一层，并且结点总数为 2^n -1， n 为层数，则称为满二叉树。</p>
+<p>如果该二叉树的所有叶子节点都在最后一层或者倒数第二层，而且最后一层的叶子节点在左边连续，倒数第二层的叶子节点在右边连续，我们称为完全二叉树。</p>
+<blockquote>
+<p>PS: 二叉树中结点等价于节点</p>
+</blockquote>
+<p><img alt="数据结构与算法-022" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-022.png"></p>
+<h4 id="二叉树的遍历及查找">二叉树的遍历及查找</h4>
+<p>对于二叉树来讲最主要、最基本的运算是遍历。遍历二叉树 是指以一定的次序访问二叉树中的每个结点。所谓访问结点是指对结点进行各种操作的简称。</p>
+<p>例如，查询结点数据域的内容，或输出它的值，或找出结点位置，或是执行对结点的其他操作。遍历二叉树的过程实质是把二叉树的结点进行线性排列的过程。</p>
+<p>二叉树的遍历方法：</p>
+<ul>
+<li>前序遍历：先访问根结点，然后前序遍历左子树，在前序遍历右子树；</li>
+<li>中序遍历：中序遍历根结点的左子树，然后访问根结点，最后遍历右子树；</li>
+<li>后序遍历：后序遍历左子树，然后后序遍历右子树，最后访问根结点；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BinaryTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="s">&#34;zs&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="s">&#34;ls&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="s">&#34;ww&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="s">&#34;zq&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">5</span><span class="p">,</span><span class="s">&#34;111&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">root</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">binaryTreeObj2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">root</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">binaryTreeObj3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTreeObj3</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">binaryTreeObj4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTreeObj3</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">binaryTreeObj5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTree</span><span class="w"> </span><span class="n">binaryTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTree</span><span class="p">.</span><span class="na">setRoot</span><span class="p">(</span><span class="n">root</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTree</span><span class="p">.</span><span class="na">preOrderShow</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">binaryTree</span><span class="p">.</span><span class="na">preOrderSearch</span><span class="p">(</span><span class="n">11</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;没有找到该结点～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;找到当前结点：id: %d, name: %s&#34;</span><span class="p">,</span><span class="n">binaryTreeObj</span><span class="p">.</span><span class="na">getId</span><span class="p">(),</span><span class="n">binaryTreeObj</span><span class="p">.</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BinaryTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRoot</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preOrderShow</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postOrderShow</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">postOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">midOrderShow</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">midOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">preOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">preOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">infixOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">infixOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">postOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">postOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BinaryTreeObj</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">BinaryTreeObj</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setLeft</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">left</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRight</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 前序遍历：根结点 =》 左结点 =》 右结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preOrder</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 后序遍历： 左结点 =》 右结点 =》 根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postOrder</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">postOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">postOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历： 左结点 =》 根结点 =》 右结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">midOrder</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">midOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">midOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 前序查找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">preOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">preOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">preOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序查找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">infixOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">infixOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">infixOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 后序查找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">postOrderSearch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">postOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">binaryTreeObj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">postOrderSearch</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">binaryTreeObj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;BinaryTreeObj{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;id=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="二叉树的删除">二叉树的删除</h4>
+<p><img alt="数据结构与算法-023" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-023.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BinaryTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">del</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">getId</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">delNo</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BinaryTreeObj</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 根据ID删除结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">delNo</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 找到当前结点的左子树结点是否为指定结点，如果是则将其置空</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 与上面同理删除右子树结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">id</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前左结点或右结点 不是要删除的结点 则进行递归删除</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">delNo</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">delNo</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="顺序存储二叉树">顺序存储二叉树</h4>
+<p>二叉树的顺序存储，指的是使用顺序表（数组）存储二叉树。</p>
+<p>需要注意的是，顺序存储只适用于完全二叉树。换句话说，只有完全二叉树才可以使用顺序表存储。因此，如果我们想顺序存储普通二叉树，需要提前将普通二叉树转化为完全二叉树。</p>
+<blockquote>
+<p>顺序存储二叉树应用实例：八大排序算法中的堆排序，就会使用到顺序存储二叉树。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrBinaryTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrBinaryTree</span><span class="w"> </span><span class="n">arrBinaryTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrBinaryTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arrBinaryTree</span><span class="p">.</span><span class="na">setArrayTree</span><span class="p">(</span><span class="n">arr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arrBinaryTree</span><span class="p">.</span><span class="na">preArrBinaryTree</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ArrBinaryTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setArrayTree</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preArrBinaryTree</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">nextLeftIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">nextRightIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nextLeftIndex</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">preArrBinaryTree</span><span class="p">(</span><span class="n">nextLeftIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nextRightIndex</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">preArrBinaryTree</span><span class="p">(</span><span class="n">nextRightIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="线索化二叉树">线索化二叉树</h4>
+<p>n 个结点的二叉链表中含有 n+1【公式 2n-(n-1)=n+1】个空指针域。利用二叉链表中的空指针域，存放指向该结点在 <strong>某种遍历次序</strong> 下的<strong>前驱</strong>和<strong>后继</strong>结点的指针，这种附加的指针称为&quot;线索&quot;。这种加上了线索的二叉链表称为线索链表，相应的二叉树称为线索二叉树。</p>
+<p>根据线索性质的不同，线索二叉树可分为前序线索二叉树、中序线索二叉树和后序线索二叉树三种。</p>
+<p>如图，按照前序遍历可以得到数组 {1, 2, 4, 5, 3, 6} 其中</p>
+<ul>
+<li>【2】的前驱结点为【1】，后继结点为【4】</li>
+<li>【6】的前驱结点为【3】，后继结点为 null</li>
+</ul>
+<p><img alt="数据结构与算法-024" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-024.png"></p>
+<p>中序线索化二叉树示意图</p>
+<p><img alt="数据结构与算法-025" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-025.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ThreadedBinaryTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="s">&#34;zs&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="s">&#34;ls&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="s">&#34;ww&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="s">&#34;zq&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">binaryTreeObj5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="p">(</span><span class="n">5</span><span class="p">,</span><span class="s">&#34;111&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">root</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">binaryTreeObj2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">root</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">binaryTreeObj3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTreeObj3</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">binaryTreeObj4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">binaryTreeObj3</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">binaryTreeObj5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 中序线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ThreadedBinaryTree</span><span class="w"> </span><span class="n">threadedBinaryTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadedBinaryTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threadedBinaryTree</span><span class="p">.</span><span class="na">infixThreadedBinaryTree</span><span class="p">(</span><span class="n">root</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历中序线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threadedBinaryTree</span><span class="p">.</span><span class="na">forEachInfixThreadedBinaryTree</span><span class="p">(</span><span class="n">root</span><span class="p">);</span><span class="w"> </span><span class="c1">// 2,1,4,3,5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ThreadedBinaryTree</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">pre</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixThreadedBinaryTree</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">node</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 左递归线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">infixThreadedBinaryTree</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getLeft</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线索化核心代码 将左结点线索化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getLeft</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">setLeft</span><span class="p">(</span><span class="n">pre</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">setLeftType</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将右结点线索化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pre</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">pre</span><span class="p">.</span><span class="na">getRight</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">pre</span><span class="p">.</span><span class="na">setRight</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">pre</span><span class="p">.</span><span class="na">setRightType</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使辅助结点指针指向当前结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pre</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 右递归线索化二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">infixThreadedBinaryTree</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getRight</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历中序线索二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">forEachInfixThreadedBinaryTree</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 用辅助结点保存根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 向左子树遍历,直到找到 leftType=1 的结点，等于1代表该结点为前驱结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getLeftType</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">getLeft</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 向右子树遍历，直到找到 rightType=0 的结点， 等于0代表该结点为右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">getRightType</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">getRight</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// node 结点向右边找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">getRight</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BinaryTreeObj</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果leftType == 0 表示指向的是左子树, 如果 1 则表示指向前驱结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果rightType == 0 表示指向是右子树, 如果 1 表示指向后继结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">leftType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rightType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">BinaryTreeObj</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">getLeft</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="nf">getRight</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setLeft</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">left</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRight</span><span class="p">(</span><span class="n">BinaryTreeObj</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setLeftType</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">leftType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">leftType</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leftType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRightType</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">rightType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">rightType</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rightType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getLeftType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">leftType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getRightType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">rightType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="哈夫曼树">哈夫曼树</h3>
+<p>哈夫曼树重要概念：</p>
+<ul>
+<li>路径和路径长度：在一棵树中，从一个结点往下可以达到的孩子或孙子结点之间的通路，称为路径。通路中分支的数目称为路径长度。若规定根结点的层数为 1，则从根结点到第 L 层结点的路径长度为 L-1；</li>
+<li>结点的权及带权路径长度：若将树中结点赋给一个有着某种含义的数值，则这个数值称为该结点的权。结点的带权路径长度为：从根结点到该结点之间的路径长度与该结点的权的乘积；</li>
+<li>树的带权路径长度：树的带权路径长度规定为所有叶子结点的带权路径长度之和，记为WPL(weighted path length) ，权值越大的结点离根结点越近的二叉树才是最优二叉树。WPL 最小的就是赫夫曼树；</li>
+</ul>
+<p>给定n个权值作为n个叶子结点，构造一棵二叉树，若该树的带权路径长度(wpl)达到最小，称这样的二叉树为最优二叉树，称为哈夫曼树，有些资料也译为赫夫曼树。</p>
+<p><img alt="数据结构与算法-028" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-028.png"></p>
+<p>WPL最小的就是哈夫曼树，如上图，中间的树就是哈夫曼树。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HuffmanTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HuffmanTree</span><span class="w"> </span><span class="n">huffmanTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanTree</span><span class="p">.</span><span class="na">buildHuffmanTree</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">13</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">29</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;前序遍历huffman树：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">huffmanTree</span><span class="p">.</span><span class="na">preOrder</span><span class="p">(</span><span class="n">root</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HuffmanTree</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preOrder</span><span class="p">(</span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">root</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">root</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="nf">buildHuffmanTree</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">HuffmanTreeNode</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanTreeNode</span><span class="p">(</span><span class="n">value</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果集合中的元素大于1则继续循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从大到小进行排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Collections</span><span class="p">.</span><span class="na">sort</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取集合中两个较小的元素进行构建 huffman 树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">leftNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">rightNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">parentNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanTreeNode</span><span class="p">(</span><span class="n">leftNode</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">rightNode</span><span class="p">.</span><span class="na">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leftNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rightNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 构建后将 leftNode， rightNode 移除集合；将parentNode加入集合；然后重新排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">leftNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">rightNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">parentNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HuffmanTreeNode</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Comparable</span><span class="o">&lt;</span><span class="n">HuffmanTreeNode</span><span class="o">&gt;</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">HuffmanTreeNode</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">preOrder</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">preOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">compareTo</span><span class="p">(</span><span class="n">HuffmanTreeNode</span><span class="w"> </span><span class="n">o</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 从小到大排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">o</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;HuffmanTreeNode{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;value=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="二叉排序树">二叉排序树</h3>
+<p>二叉排序树（Binary Sort Tree），又称二叉查找树（Binary Search Tree），亦称二叉搜索树。是数据结构中的一类。在一般情况下，查询效率比链表结构要高。</p>
+<p>对于二叉排序树的任何一个非叶子节点，要求左子节点的值比当前节点的值小，右子节点的值比当前节点的值大。如果有相同的值，可以将该节点放在左子节点或右子节点，二叉排序树的中序遍历为有序数列。</p>
+<p><img alt="数据结构与算法-030" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-030.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BinarySortTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRoot</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查找结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">search</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查找当前结点的父结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">searchParentNode</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">searchParentNode</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 删除结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">delNode</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果删除的结点是根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">targetNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取当前结点的父结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">parentNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">searchParentNode</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除的结点是叶子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断是左结点还是右结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除的结点有两个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从右子树找到最小的值并删除，将该值赋值给targetNode</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">targetNode</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">delRightTreeMin</span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除只有一颗子树的结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">parentNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当前结点存在左子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">parentNode</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当前结点存在右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parentNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetNode</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">delRightTreeMin</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">target</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 循环的查找左子节点，就会找到最小值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">target</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">target</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 此时 target就指向了最小结点 删除最小结点（该节点肯定是左叶子节点）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">delNode</span><span class="p">(</span><span class="n">target</span><span class="p">.</span><span class="na">val</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">target</span><span class="p">.</span><span class="na">val</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">val</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">val</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">val</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查找结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">search</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">search</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查找当前结点的父结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">searchParentNode</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">searchParentNode</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">searchParentNode</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前待插入结点的值小于当前结点，将其插入在左子树中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">val</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">val</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将当前结点插入右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;val=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">val</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="平衡二叉树">平衡二叉树</h3>
+<p>二叉搜索树一定程度上可以提高搜索效率，但是当序列构造二叉搜索树，可能会将二叉树退化成单链表，从而降低搜索效率。</p>
+<p>平衡二叉树也叫平衡二叉搜索树（Self-balancing binary search tree）又被称为AVL树，可以保证查询效率较高。</p>
+<p>平衡二叉树的特点：</p>
+<ul>
+<li>平衡二叉树一定是二叉排序；</li>
+<li>是一棵空树或它的左右两个子树的高度差的绝对值不超过1，并且左右两个子树都是一棵平衡二叉树；</li>
+</ul>
+<p><img alt="数据结构与算法-031" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-031.gif"></p>
+<p>将有序二叉树变为平衡二叉树代码</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AVLTreeDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AVLTree</span><span class="w"> </span><span class="n">avlTree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AVLTree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">11</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">avlTree</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前树高度：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">avlTree</span><span class="p">.</span><span class="na">height</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前根结点：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">avlTree</span><span class="p">.</span><span class="na">getRoot</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前左子树高度：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">avlTree</span><span class="p">.</span><span class="na">getRoot</span><span class="p">().</span><span class="na">leftHeight</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前右子树高度：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">avlTree</span><span class="p">.</span><span class="na">getRoot</span><span class="p">().</span><span class="na">rightHeight</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">AVLTree</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setRoot</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">getRoot</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">root</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">height</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">height</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">root</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前左子树的高度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">leftHeight</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">height</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前结点右子树的高度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">rightHeight</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">height</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前结点的高度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">height</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">height</span><span class="p">()),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">height</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">leftRote</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个新结点，并设置值等于当前结点的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使新结点的左结点指向当前结点的左结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 新结点的右结点指向当前结点的右结点的左结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使当前结点的值指向新结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使当前结点的右结点指向当前结点的右结点的右结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使当前结点的左结点指向新结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 右旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">rightRote</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newNode</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newNode</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">.</span><span class="na">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">.</span><span class="na">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 添加结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前待插入结点的值小于当前结点，将其插入在左子树中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将当前结点插入右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果左子树的高度-右子树的高度 &gt; 1 进行右旋转 反之进行左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">leftHeight</span><span class="p">()</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">rightHeight</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果当前结点的左子树的右子树的高度&gt;当前结点左子树的左子树的高度 则进行左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">rightHeight</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">leftHeight</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 对当前结点的左结点进行左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">leftRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 对当前结点右旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">rightRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">rightRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">rightHeight</span><span class="p">()</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">leftHeight</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">leftHeight</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">rightHeight</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 对当前结点的右结点进行右旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">rightRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 对当前结点进行左旋转</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">leftRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">leftRote</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 中序遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">infixOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">infixOrder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;value=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="多路查找树">多路查找树</h3>
+<p>在二叉树中，每个节点有数据项，最多有两个子节点。如果允许每个节点可以有更多的数据项和更多的子节点，就是多叉树（multiway tree）。多叉树通过重新组织节点，减少树的高度，能对二叉树进行优化。典型的多叉树有：2-3树、2-3-4树、红黑树和B树。</p>
+<p>多叉树的前提是有序二叉树。</p>
+<h4 id="2-3树">2-3树</h4>
+<p>2-3树是由二节点和三节点构成的树，是最简单的B树结构，2-3树的所有叶子节点都在同一层(只要是B树都满足这个条件)。</p>
+<ul>
+<li>有两个子节点的节点叫二节点，二节点要么没有子节点，要么有两个子节点；</li>
+<li>有三个子节点的节点叫三节点，三节点要么没有子节点，要么有三个子节点；</li>
+</ul>
+<p><img alt="数据结构与算法-032" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-032.png"></p>
+<p>2-3-4树，与2-3树类似。</p>
+<p><img alt="数据结构与算法-033" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-033.png"></p>
+<h4 id="b树">B树</h4>
+<p>B-tree 树即 B 树，B 即 Balanced ，平衡的意思。 B树通过重新组织节点，降低树的高度，并且减少i/o读写次数来提升效率。</p>
+<p>文件系统及数据库系统的设计者利用了磁盘预读原理，将一个节点的大小设为等于一个页(页的大小通常为4k)，这样每个节点只需要一次I/O就可以完全载入。</p>
+<blockquote>
+<p>B树的阶（度）：节点的最多子节点个数。比如2-3树的阶是3，2-3-4树的阶是4。</p>
+</blockquote>
+<p>B树的搜索，从根结点开始，对结点内的关键字（有序）序列进行二分查找，如果命中则结束，否则进入查询关键字所属范围的儿子结点；重复，直到所对应的儿子指针为空，或已经是叶子结点。</p>
+<p>B树的关键字集合分布在整颗树中，即叶子节点和非叶子节点都存放数据，搜索有可能在非叶子结点结束，其搜索性能等价于在关键字全集内做一次二分查找。</p>
+<p><img alt="数据结构与算法-034" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-034.png"></p>
+<h4 id="b树-1">B+树</h4>
+<p>B+树是B树的变体，也是一种多路搜索树。</p>
+<p>B+树的搜索与B树也基本相同，区别是B+树只有达到叶子结点才命中（B树可以在非叶子结点命中），其性能也等价于在关键字全集做一次二分查找。</p>
+<p>B+树所有关键字都出现在叶子结点的链表中（即数据只能在叶子节点【也叫稠密索引】），且链表中的关键字(数据)恰好是有序的。所以不可能在非叶子结点命中。</p>
+<p>B+树的所有叶结点构成一个有序链表，可以按照关键码排序的次序遍历全部记录， B+树更适合文件索引系统，B树和B+树各有自己的应用场景，不能说B+树完全比B树好，反之亦然。</p>
+<p><img alt="数据结构与算法-035" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-035.png"></p>
+<h4 id="b树-2">B*树</h4>
+<p>B* 树是B+树的变体，在B+树的非根和非叶子结点再增加指向兄弟的指针。</p>
+<p><img alt="数据结构与算法-036" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-036.png"></p>
+<h3 id="图">图</h3>
+<p>图是一种数据结构，其中结点可以具有零个或多个相邻元素。两个结点之间的连接称为边。结点也可以称为顶点。</p>
+<p>如果给图的每条边规定一个方向，那么得到的图称为有向图。在有向图中，与一个节点相关联的边有出边和入边之分。相反，边没有方向的图称为无向图。</p>
+<p><img alt="数据结构与算法-037" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-037.png"></p>
+<p>可用二维数组表示图（邻接矩阵）；或链表表示（邻接表）。</p>
+<p><img alt="数据结构与算法-038" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-038.png"></p>
+<p><img alt="数据结构与算法-039" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-039.png"></p>
+<p>用java模拟图，包括图的深度遍历，广度遍历。</p>
+<p><img alt="数据结构与算法-040" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-040.gif"></p>
+<p><img alt="数据结构与算法-041" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-041.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GraphDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">vertexes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;A&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;B&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;D&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;E&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertexes</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Graph</span><span class="w"> </span><span class="n">graph</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Graph</span><span class="p">(</span><span class="n">n</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">vertexes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">graph</span><span class="p">.</span><span class="na">addVertex</span><span class="p">(</span><span class="n">vertex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// A-B</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// A-C</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// B-C</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// B-D</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">addEdge</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// B-E</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 展示图转换的矩阵</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">showEdges</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 图的深度遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">dfs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 图的广度遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">graph</span><span class="p">.</span><span class="na">bfs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Graph</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 保存顶点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">vertexList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 保存边的数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">sideNums</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 保存图的矩阵</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">edges</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">isVisited</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="nf">Graph</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">vertexList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">n</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">edges</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">n</span><span class="o">][</span><span class="n">n</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sideNums</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取第一个结点的下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getFirstNeighbor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">index</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取当前结点的下一个结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getNextNeighbor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">index</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 图的深度遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dfs</span><span class="p">(</span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">getVertexValByIndex</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将当前遍历后的顶点标记为true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">isVisited</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前结点的下一个结点的索引位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">firstNeighborIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getFirstNeighbor</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果 ！= -1 代表当前结点没有找到下一个结点，需要向下移动</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">firstNeighborIndex</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 判断该结点是否被遍历过</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isVisited</span><span class="o">[</span><span class="n">firstNeighborIndex</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dfs</span><span class="p">(</span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="n">firstNeighborIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 当前结点向后移动，否则是死循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">firstNeighborIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNextNeighbor</span><span class="p">(</span><span class="n">firstNeighborIndex</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dfs</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">isVisited</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">getVertexCount</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isVisited</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dfs</span><span class="p">(</span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 一个结点的广度优先遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">bfs</span><span class="p">(</span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 队列头结点下标索引</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">headIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 相邻结点下标索引</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">neighborIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">LinkedList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">queue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">getVertexValByIndex</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">isVisited</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">queue</span><span class="p">.</span><span class="na">addLast</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果队列不等于空 则需要遍历循环查找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">queue</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">headIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">queue</span><span class="p">.</span><span class="na">removeFirst</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 得到第一个邻接结点的下标</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">neighborIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getFirstNeighbor</span><span class="p">(</span><span class="n">headIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">neighborIndex</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 是否访问过</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isVisited</span><span class="o">[</span><span class="n">neighborIndex</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">getVertexValByIndex</span><span class="p">(</span><span class="n">neighborIndex</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">isVisited</span><span class="o">[</span><span class="n">neighborIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">queue</span><span class="p">.</span><span class="na">addLast</span><span class="p">(</span><span class="n">neighborIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// neighborIndex 向下找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">neighborIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNextNeighbor</span><span class="p">(</span><span class="n">headIndex</span><span class="p">,</span><span class="w"> </span><span class="n">neighborIndex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 广度优先遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">bfs</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">isVisited</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">getVertexCount</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isVisited</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bfs</span><span class="p">(</span><span class="n">isVisited</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 添加顶点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addVertex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">vertex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">vertexList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">vertex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 添加边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addEdge</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">vertex1</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">vertex2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">edges</span><span class="o">[</span><span class="n">vertex1</span><span class="o">][</span><span class="n">vertex2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">edges</span><span class="o">[</span><span class="n">vertex2</span><span class="o">][</span><span class="n">vertex1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sideNums</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取边的数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getSideNums</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">sideNums</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 遍历矩阵</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showEdges</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">edge</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">edges</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">edge</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取顶点数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getVertexCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">vertexList</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 获取边之间的权值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getVertexWeight</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">vertex1</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">vertex2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">vertex1</span><span class="o">][</span><span class="n">vertex2</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 根据下标获取结点的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getVertexValByIndex</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">vertexList</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="算法">算法</h2>
+<p>英文对应的单词是Algorithm，它的本意为：解决问题的方法，所以算法的直接理解就是解决问题的方法。在计算机领域定义的话就是：一系列解决问题的、清晰、可执行的计算机指令。</p>
+<p>一个算法的优劣可以用空间复杂度与时间复杂度来衡量。</p>
+<h3 id="算法复杂度">算法复杂度</h3>
+<h4 id="时间复杂度">时间复杂度</h4>
+<p>度量一个算法执行时间的两种方法：</p>
+<ul>
+<li>
+<p>事后统计法：即直接运行程序，统计需要的时间和空间。但是，这种方法有两个问题：</p>
+<ol>
+<li>结果非常依赖于测试环境。比如，用i3和用i8运行程序所需的时间是不同的;</li>
+<li>结果受测试规模的影响特别大。比如，对有序数组进行排序的时间比对逆序数组排序的时间短；对于小规模数据而言，插入排序所需时间比快速排序要短;</li>
+</ol>
+<p>所以，就需要有一种不用具体测试数据，也能估计算法执行效率的方法，就是算法复杂度分析，包括时间、空间复杂度分析。</p>
+</li>
+<li>
+<p>事前估算法：通过分析某个算法的时间复杂度来判断那个算法更优;</p>
+</li>
+</ul>
+<p>一般情况下，算法中的基本操作语句的重复执行次数是问题规模 n 的某个函数， 用<code>T(n)</code>表示，若有某个辅助函数<code>f(n)</code>，使得当 n 趋近于无穷大时，<code>T(n)/f(n)</code>的极限值为不等于零的常数，则称<code>f(n)</code>是<code>T(n)</code>的同数量级函数。记作 <code>T(n)=Ｏ(f(n))</code>， 称<code>Ｏ(f(n))</code>为算法的渐进时间复杂度，简称时间复杂度。</p>
+<p>例如，T(n) = n + 1 与 T(n) = n 就是同数量级函数，因为 n+1/n 的极限值为不等于零的常数。
+T(n) 不同，但时间复杂度可能相同: T(n)=n²+7n+6 与 T(n)=3n²+2n+2 它们的 T(n) 不同， 但时间复杂度相同，都为 O(n²)。</p>
+<p>计算时间复杂度的方法：</p>
+<ul>
+<li>用常数 1 代替运行时间中的所有加法常数： T(n)=n²+7n+6 =&gt; T(n)=n²+7n+1</li>
+<li>修改后的运行次数函数中，只保留最高阶项： T(n)=n²+7n+1 =&gt; T(n) = n²</li>
+<li>去除最高阶项的系数：T(n) = n² =&gt; T(n) = n² =&gt; O(n²)</li>
+</ul>
+<hr>
+<p><strong>时间频度</strong></p>
+<p>一个算法花费的时间与算法中的语句的执行次数成正比例,哪个算法执行次数多,他花费的时间就多.一个算法中的语句执行次数称为语句频度或时间频度.记为T(n)。</p>
+<p>随着时间的推移，一些复杂度花费时间无限接近：</p>
+<ol>
+<li>忽略常数项:</li>
+</ol>
+<ul>
+<li>2n+20 和 2n 随着 n 变大，执行曲线无限接近,20 可以忽略</li>
+<li>3n+10 和 3n 随着 n 变大，执行曲线无限接近,10 可以忽略</li>
+</ul>
+<ol start="2">
+<li>忽略低次项:</li>
+</ol>
+<ul>
+<li>2n²+3n+10 和 2n² 随着 n 变大, 执行曲线无限接近,可以忽略 3n+10</li>
+<li>n²+5n+20 和 n² 随着 n 变大,执行曲线无限接近,可以忽略 5n+20</li>
+</ul>
+<ol start="3">
+<li>忽略系数:</li>
+</ol>
+<ul>
+<li>随着 n 值变大， 5n²+7n 和 3n² + 2n ，执行曲线重合, 说明这种情况下, 5 和 3 可以忽略</li>
+<li>对于 n^3+5n 和 6n^3+4n，执行曲线分离，不能忽略系数，说明多少次方是关键</li>
+</ul>
+<hr>
+<p><strong>常见的时间复杂度</strong></p>
+<ul>
+<li>
+<p>常数阶 O(1): 无论代码执行了多少行，只要是没有循环等复杂结构，这个代码的时间复杂度就都是O(1)；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">int i = 1;
+</span></span><span class="line"><span class="cl">int j = 2;
+</span></span><span class="line"><span class="cl">++i;
+</span></span><span class="line"><span class="cl">j++;
+</span></span><span class="line"><span class="cl">int m = i + j;
+</span></span></code></pre></div></li>
+<li>
+<p>对数阶 O(log2n)</p>
+<p><img alt="数据结构与算法-012" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-012.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">int i = 1;
+</span></span><span class="line"><span class="cl">while(i&lt;n){
+</span></span><span class="line"><span class="cl">    i = i*2;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>线性阶 O(n): 它消耗的时间是随着n的变化而变化的,与n成正比或反比；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(int i=1; i&lt;=n; ++i){
+</span></span><span class="line"><span class="cl">    j = i;
+</span></span><span class="line"><span class="cl">    j++;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>线性对数阶 O(nlog2n): 将时间复杂度为O(logn)的代码循环n遍，那么它的时间复杂度就是 n * O(logN)，也就是了O(nlogN);</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(int m=1; m&lt;=n; ++m){
+</span></span><span class="line"><span class="cl">    int i = 1;
+</span></span><span class="line"><span class="cl">    while(i&lt;n){
+</span></span><span class="line"><span class="cl">        i = i*2;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>平方阶 O(n^2): 如果把 O(n) 的代码再嵌套循环一遍，它的时间复杂度就是 O(n²)，这段代码其实就是嵌套了2层n循环，它的时间复杂度就是 <code>O(n*n)</code>，即 O(n²) 如果将其中一层循环的n改成m，那它的时间复杂度就变成了 <code>O(m*n)</code>;</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(int i=1; i&lt;=n; ++i){
+</span></span><span class="line"><span class="cl">    for(int j=1; j&lt;=n; ++j){
+</span></span><span class="line"><span class="cl">        j=i;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>立方阶 O(n^3)</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(int i=1; i&lt;=n; ++i){
+</span></span><span class="line"><span class="cl">    for(int j=1; j&lt;=n; ++j){
+</span></span><span class="line"><span class="cl">        for(int x=1; x&lt;=n; ++x){
+</span></span><span class="line"><span class="cl">            int m = 0;
+</span></span><span class="line"><span class="cl">            i = x+j;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>
+<p>k 次方阶 O(n^k)</p>
+</li>
+<li>
+<p>指数阶 O(2^n)</p>
+</li>
+</ul>
+<p>常见的算法时间复杂度由小到大依次为：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Ο (1)＜Ο (log2n)＜Ο (n)＜Ο (nlog2n)＜Ο (n2)＜Ο (n3)＜ Ο (nk) ＜ Ο (2n)
+</span></span></code></pre></div><p>随着问题规模 n 的不断增大，上述时间复杂度不断增大，算法的执行效率越低。</p>
+<h4 id="空间复杂度">空间复杂度</h4>
+<p>类似于时间复杂度的讨论，一个算法的空间复杂度(Space Complexity)定义为该算法所耗费的存储空间，它也是问题规模 n 的函数。</p>
+<p>空间复杂度全称为渐进空间复杂度，是对一个算法在运行过程中临时占用存储空间大小的量度。 有的算法需要占用的临时工作单元数与解决问题的规模 n 有关， 它随着 n 的增大而增大， 当 n 较大时， 将占用较多的存储单元， 例如快速排序和归并排序算法, 基数排序就属于这种情况
+在做算法分析时， 主要讨论的是时间复杂度。 从用户使用体验上看， 更看重的程序执行的速度。 一些缓存产品(redis, memcache)和算法(基数排序)本质就是用空间换时间</p>
+<p>空间复杂度较为简单，常见的空间复杂度为 O(1)，O(n) 和 O(n ^ 2)。</p>
+<h3 id="递归">递归</h3>
+<p>递归就是方法自己调用自己，每次调用时传入不同的变量，递归有助于编程者解决复杂的问题，同时可以让代码变得简洁。</p>
+<p><strong>递归能解决什么问题？</strong></p>
+<ul>
+<li>各种数学问题如: 8 皇后问题，汉诺塔，阶乘问题，迷宫问题，球和篮子的问题(google 编程大赛)；</li>
+<li>各种算法中也会使用到递归， 比如快排， 归并排序， 二分查找， 分治算法等；</li>
+<li>用栈解决的问题，使用递归替换代码更佳简洁；</li>
+</ul>
+<p>使用递归遵守的规则：</p>
+<ul>
+<li>执行一个方法时，就创建一个新的受保护的独立空间(一个线程有自己独立的一个栈空间，每个方法调用对应着一个栈帧)；</li>
+<li>方法的局部变量是独立的，不会相互影响；</li>
+<li>如果方法中使用的是引用类型变量，就会共享该引用类型的数据，比如数组；</li>
+<li>递归必须向退出递归的条件逼近，否则就是无限递归，出现 StackOverflowError；</li>
+<li>当一个方法执行完毕，或者遇到return，就会返回，遵守谁调用，就将结果返回给谁，同时当方法执行完毕或者返回时，该方法也就执行完毕；</li>
+</ul>
+<h4 id="迷宫回溯">迷宫回溯</h4>
+<p>迷宫回溯问题，寻找最短路径可以通过改变策略，将每个策略都经过的路保存在集合中，最后看哪个集合最小即最小路径。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Mazeback</span><span class="w"> </span><span class="n">mazeback</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Mazeback</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mazeback</span><span class="p">.</span><span class="na">createMap</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mazeback</span><span class="p">.</span><span class="na">list</span><span class="p">(</span><span class="n">map</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;自动寻找路线：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mazeback</span><span class="p">.</span><span class="na">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mazeback</span><span class="p">.</span><span class="na">list</span><span class="p">(</span><span class="n">map</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Mazeback</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 创建地图</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="nf">createMap</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 地图</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">7</span><span class="o">][</span><span class="n">8</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">7</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">7</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">6</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="o">[</span><span class="n">3</span><span class="o">][</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="o">[</span><span class="n">3</span><span class="o">][</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">map</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 遍历地图</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">list</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">map</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">map</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">map</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 寻找路径</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 1：墙；2：通路，3：死路</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">setWay</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">column</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="o">[</span><span class="n">5</span><span class="o">][</span><span class="n">6</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 先假设是通路</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">map</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 寻找路径顺序：下，右，上，左</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">setWay</span><span class="p">(</span><span class="n">map</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 当标记为3时，说明是死路走不通</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">map</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="八皇后问题">八皇后问题</h4>
+<p>八皇后问题，是一个古老而著名的问题，是回溯算法的典型案例。该问题是国际西洋棋棋手马克斯·贝瑟尔于1848 年提出：在 8 × 8 格的国际象棋上摆放八个皇后，使其不能互相攻击， 即： 任意两个皇后都不能处于同一行、同一列或同一斜线上，问有多少种摆法。</p>
+<blockquote>
+<p>八皇后问题共92中解法</p>
+</blockquote>
+<p><img alt="数据结构与算法-010" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-010.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EightQueens</span><span class="w"> </span><span class="n">eightQueens</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EightQueens</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">eightQueens</span><span class="p">.</span><span class="na">exec</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">EightQueens</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">max</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">EightQueens</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">8</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">max</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 算法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">position</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前位置等于max说明解法成立，需要回溯</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">position</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">max</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">print</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">max</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">check</span><span class="p">(</span><span class="n">position</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">exec</span><span class="p">(</span><span class="n">position</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 判断皇后位置是否冲突</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">check</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">position</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">position</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断是否在同一列或在同一斜线上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">abs</span><span class="p">(</span><span class="n">position</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">abs</span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 打印数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">print</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="排序算法">排序算法</h3>
+<p>排序也称排序算法，是将一组数据，依指定的顺序进行排列的过程。</p>
+<p>排序算法分类：</p>
+<ul>
+<li>内部排序：指将需要处理的所有数据都加载到内部存储器(内存)中进行排序；</li>
+<li>外部排序法：数据量过大，无法全部加载到内存中，需要借助外部存储(文件等)进行排序；</li>
+</ul>
+<p><img alt="数据结构与算法-011" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-011.png"></p>
+<p>常见内排序算法复杂度比较</p>
+<p><img alt="数据结构与算法-013" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-013.png"></p>
+<p>名词解释：</p>
+<ul>
+<li>n：数据规模</li>
+<li>k：&ldquo;桶&quot;的个数</li>
+<li>In-place：占用常数内存，不占用额外内存</li>
+<li>Out-place：占用额外内存</li>
+<li>稳定性：排序后两个相等键值的顺序和排序之前它们的顺序相同，不稳定性则相反</li>
+<li>时间复杂度：一个算法执行所耗费的时间</li>
+<li>空间复杂度：运行完一个程序所需内存的大小</li>
+</ul>
+<h4 id="冒泡排序">冒泡排序</h4>
+<p>冒泡排序的基本思想是：通过对待排序序列从前向后（从下标较小的元素开始），依次比较相邻元素的值，若发现逆序（当前值大于比较的值）则交换，使值较大的元素逐渐从前移向后部，就像水底下的气泡一样逐渐向上冒。</p>
+<p><img alt="数据结构与算法-014" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-014.gif"></p>
+<p>优化：因为排序的过程中， 各元素不断接近自己的位置，如果一趟比较下来没有进行过交换，就说明序列有序，因此要在排序过程中设置一个标志 flag 判断元素是否进行过交换。 从而减少不必要的比较。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BubbleSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="n">len</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将当前值与next值进行比较，如果当前值大于next值则交换两者之间的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">1</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 加入标志为进行判断，如果整个循环下啦都没有交换位置，说明该数组是有序的，所以直接退出循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">flag</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="选择排序">选择排序</h4>
+<p>选择式排序也属于内部排序法，是从欲排序的数据中，按指定的规则选出某一元素，再依规定交换位置后达到排序的目的。</p>
+<p>首先在未排序序列中找到最小元素，存放到排序序列的起始位置，然后，再从剩余未排序元素中继续寻找最小元素，然后放到排序序列末尾。以此类推，直到所有元素均排序完毕。</p>
+<p><img alt="数据结构与算法-015" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-015.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">SelectSorting</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="o">+</span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 如果next值大于当前值，则记录该值和该值的位置，等全部比较完毕后，将最大的一个与数据的末尾进行替换</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">j</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将每次循环中的最小的值，调整到最前面</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">min</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">i</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">min</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">data</span><span class="o">[</span><span class="n">min</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="插入排序">插入排序</h4>
+<p>插入排序（Insertion Sorting） 的基本思想是：把 n 个待排序的元素看成为一个有序表和一个无序表;</p>
+<p>开始时有序表中只包含一个元素，无序表中包含有 n-1 个元素，排序过程中每次从无序表中取出第一个元素，把它的排序码依次与有序表元素的排序码进行比较， 将它插入到有序表中的适当位置，使之成为新的有序表。</p>
+<p>对于未排序数据，在已排序序列中从后向前扫描，找到相应位置并插入。插入排序在实现上，通常在从后向前扫描过程中，需要反复把已排序元素逐步向后挪位，为最新元素提供插入空间。</p>
+<p><img alt="数据结构与算法-016" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-016.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">InsertSorting</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果当前要插入的值 data[i] &gt; 有序队列中最后一个，则将其直接插入到最后一个</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果当前位置的值【tmp】小于 上一个位置的值【data[index]】说明当前值需要插入到有序队列中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">index</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="希尔排序">希尔排序</h4>
+<p>希尔排序是希尔（Donald Shell） 于1959年提出的一种排序算法。希尔排序也是一种插入排序，它是简单插入排序经过改进之后的一个更高效的版本，也称为缩小增量排序。</p>
+<p>希尔排序按照增量将数组进行分组，对每组使用直接插入排序算法排序；随着增量逐渐减少，每组包含的关键词越来越多，当增量减至1时，整个文件恰被分成一组，算法便终止。</p>
+<p><img alt="数据结构与算法-017" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-017.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">ShellSorting</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 希尔排序，交换法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sortSwap</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数据分组，分组数量：data.length/2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;&gt;=</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">gap</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 遍历每组中的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">gap</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">gap</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 将每组中的元素进行排序（交换元素）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">gap</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">gap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">data</span><span class="o">[</span><span class="n">j</span><span class="o">+</span><span class="n">gap</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 插入法，融入 插入排序 思想</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数据分组，分组数量：data.length/2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;&gt;=</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">gap</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 如果当前位置的值【tmp】小于 上一个位置的值【data[index]】说明当前值需要插入到有序队列中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">gap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">gap</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">gap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">index</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">gap</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">data</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="快速排序">快速排序</h4>
+<p>快速排序是由东尼·霍尔所发展的一种排序算法。在平均状况下，排序n个项目要 Ο(nlogn) 次比较。在最坏状况下则需要 Ο(n2) 次比较，但这种状况并不常见。事实上，快速排序通常明显比其他 Ο(nlogn) 算法更快，因为它的内部循环可以在大部分的架构上很有效率地被实现出来。</p>
+<p>快速排序又是一种分而治之思想在排序算法上的典型应用。本质上来看，快速排序应该算是在冒泡排序基础上的递归分治法。快速排序思路：</p>
+<ul>
+<li>选定pivot基准数</li>
+<li>将大于pivot基准数放在基准数右边</li>
+<li>将小于pivot基准数放在基准数左边</li>
+</ul>
+<p><img alt="数据结构与算法-018" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-018.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">QuickSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">r</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果开始的位置大于等于结束的位置则不用进行比较直接退出</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">l</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">r</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">l</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">r</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 基准数值，将小于该数值的放在该数字的左边，大于该数值的放在右边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">pivot</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从右向左开始比较，如果此数大于等于基准数则将right索引向前移动，否则，将该值覆盖到对应的 data[left] 中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">right</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">pivot</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">--</span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">right</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从左向右开始比较，如果此数小于等于基准数则将left索引向后移动，否则，将该值覆盖到对应的 data[right] 中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">pivot</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">++</span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="o">[</span><span class="n">right</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 此时left与right指向重合的位置为基准所在的位置，需要将该位置覆盖掉为基准的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">data</span><span class="o">[</span><span class="n">left</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pivot</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 递归排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sort</span><span class="p">(</span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="n">left</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sort</span><span class="p">(</span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="n">r</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w"> 
+</span></span></span></code></pre></div><h4 id="归并排序">归并排序</h4>
+<p>归并排序是利用归并的思想实现的排序方法， 该算法采用经典的分治（divide-and-conquer）策略；分治法将问题分成一些小的问题然后递归求解， 而治的阶段则将分的阶段得到的各答案&quot;修补&quot;在一起，即分而治之。</p>
+<p>归并排序算法思路：采用分治算法思想，首先将序列使用递归进行拆分，然后进行合并；合并思路，将两个有序队列中的元素分别按顺序进行比较，将结果保存在一个临时数组中，最后将临时数组合并到最后的队列中。</p>
+<p><img alt="数据结构与算法-019" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-019.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MergeSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 递归拆分算法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 分别向左向右递归</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">divide</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="p">,</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">divide</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 拆分一次合并一次</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">merge</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 合并算法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">merge</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">tmpArr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">leftIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">start</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">rightIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmpArrIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断是否超出范围</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">leftIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">rightIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将两组数据进行比较，按照从小到大的顺序将两组数据填入 tmpArr 中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">leftIndex</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">rightIndex</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">leftIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">++</span><span class="n">leftIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">rightIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">++</span><span class="n">rightIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpArrIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断两组数据是否还有剩余，如果有剩余数据，则直接将数据追加到 tmpArr 数组后边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">leftIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">mid</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">leftIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">leftIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpArrIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">rightIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">rightIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">rightIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpArrIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将两组数据进行合并</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tmpArrIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmpLeftIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leftIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">tmpLeftIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">tmpLeftIndex</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmpArr</span><span class="o">[</span><span class="n">tmpArrIndex</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpLeftIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">++</span><span class="n">tmpArrIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="基数排序">基数排序</h4>
+<p>基数排序是 1887 年赫尔曼·何乐礼发明的。基数排序属于“分配式排序”，又称“桶子法”或 bin sort，顾名思义，它是通过键值的各个位的值，将要排序的元素分配至某些“桶”中，达到排序的作用,基数排序法是属于稳定性的排序， 基数排序法的是效率高的稳定性排序法。</p>
+<p>基数排序是桶排序的扩展，它是这样实现的： 将所有待比较数值统一为同样的数位长度，数位较短的数前面补零；然后， 从最低位开始， 依次进行一次排序。这样从最低位排序一直到最高位排序完成以后, 数列就变成一个有序序列。</p>
+<p><img alt="数据结构与算法-020" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-020.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BucketSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 求数组中最大数的长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">maxNum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">maxNum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">maxNum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">maxNumLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">maxNum</span><span class="p">).</span><span class="na">length</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 桶，用于保存数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">buckets</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">][</span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存放每个桶的保存数据的索引</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">bucketElementIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数组中的元素 按照 个、十、百、千 …… 的顺序依次放入桶中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">maxNumLen</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">*=</span><span class="w"> </span><span class="n">10</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 遍历二维数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 计算放入的桶的下标</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">buckets</span><span class="o">[</span><span class="n">index</span><span class="o">][</span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">index</span><span class="o">]]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">index</span><span class="o">]++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 从桶中依次取出元素并放入原数组中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">bucketElementIndex</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">f</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 判断桶中是否保存数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">f</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">f</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="n">h</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">arr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buckets</span><span class="o">[</span><span class="n">f</span><span class="o">][</span><span class="n">h</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">bucketElementIndex</span><span class="o">[</span><span class="n">f</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="堆排序">堆排序</h4>
+<p>堆排序是利用堆这种数据结构而设计的一种排序算法，堆排序是一种选择排序，它的最坏、最好、平均时间复杂度均为O(nlogn)，它也是不稳定排序。</p>
+<p>堆排序的基本思想是：将待排序序列构造成一个大顶堆，此时，整个序列的最大值就是堆顶的根节点。将其与末尾元素进行交换，此时末尾就为最大值。然后将剩余n-1个元素重新构造成一个堆，这样会得到n个元素的次小值。如此反复执行，便能得到一个有序序列了。</p>
+<blockquote>
+<p>大顶堆：每个节点的值都大于或等于其子节点的值，在堆排序算法中用于升序排列；
+小顶堆：每个节点的值都小于或等于其子节点的值，在堆排序算法中用于降序排列；</p>
+</blockquote>
+<p><img alt="数据结构与算法-027" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-027.png"></p>
+<p><img alt="数据结构与算法-026" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-026.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">HeapSorting</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 计算树中的叶子结点位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">leafNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 构建大顶堆，此处需要注意 i &gt;= 0 需要算根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leafNode</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">--</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">buildMaxHeap</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 构建大顶堆后，将根元素与树中的最后一个进行交换，再循环构建大顶堆</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">--</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">buildMaxHeap</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 堆排序核心代码 构建大顶堆
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param arr 需要调整的数组
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param i   非叶子结点的索引位置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param len 每次调整的长度
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">buildMaxHeap</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存非叶子结点的位置如果该结点的值小于子结点的值，则需要进行交换</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 从上至下，从左至右 遍历. 从第一个左子结点开始遍历</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果左子结点 &lt; 右结点，则需要将 n 指向右结点，即后移</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">n</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">n</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 当前非叶子结点 &lt; 当前子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">n</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">tmp</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将当前非叶子结点指向叶子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">n</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将i指向当前叶子结点，待最后将其变为 非叶子结点的值 即tmp的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 与前面互相呼应</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="查找算法">查找算法</h3>
+<h4 id="线性查找">线性查找</h4>
+<p>线性查找又称顺序查找，是一种最简单的查找方法，它的基本思想是从第一个记录开始，逐个比较记录的关键字，直到和给定的K值相等，则查找成功；若比较结果与文件中n个记录的关键字都不等，则查找失败。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">LinearSearch</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="二分查找">二分查找</h4>
+<p>二分查找也称折半查找，它是一种效率较高的查找方法。但是，折半查找要求线性表必须采用顺序存储结构，而且表中元素按关键字有序排列。</p>
+<p><strong>二分查找算法的前提，数组必须是有序数组，如果没有有序列表，请使用<a href="/iblog/posts/essays/data-structures-algorithms/#%E6%8E%92%E5%BA%8F%E7%AE%97%E6%B3%95">排序算法</a>对列表进行排序。</strong></p>
+<p>递归实现二分查找</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">BinarySearch</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 使用二分查找时，arr必须为有序列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 在 {@param arr} 中 没有查到 {@param value}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">end</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">start</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取中间值，用于分割列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">end</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">midVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果 查找的值&lt; 中间值，说明该值可能在mid的左边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">midVal</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 相反如果 查找的值 &gt; 中间值，说明该值可能在mid的右边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">midVal</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用递归不停的向下细分，当 value == arr[mid] 时 返回该值，说明此时已经找到了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>非递归实现二分查找</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BinarySearchDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">10</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BinarySearch</span><span class="p">().</span><span class="na">search</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BinarySearch</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 使用二分查找时，arr必须为有序列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">mid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果目标值小于中间值则向左边找，反之向右边找</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="插值查找">插值查找</h4>
+<p>插值查找算法类似于二分查找，与二分查找不同的是插值查找每次从自适应 mid 处开始查找，而不是像二分查找那样每次都从中间开始找。</p>
+<p><img alt="数据结构与算法-021" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-021.png"></p>
+<p>注意：对于数据量较大，关键字分布比较均匀（最好是线性分布）的查找表来说，采用插值查找，速度较快；对于关键字分布不均匀的情况下，该方法不一定比二分查找要好。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">InsertValueSearch</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 与二分查找基本相同，只是查找 mid 值发生了变动</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 在 {@param arr} 中 没有查到 {@param value}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">start</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">end</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">start</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">start</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="n">arr</span><span class="o">[</span><span class="n">end</span><span class="o">]</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">start</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p">(</span><span class="n">end</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">start</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">midVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">mid</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">midVal</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="n">mid</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">midVal</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">mid</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="斐波那契查找">斐波那契查找</h4>
+<p>斐波那契查找是基于【黄金分割】的二分查找。即在斐波那契队列中，将二分查找中的分割点替换为黄金分割点，来查找。</p>
+<blockquote>
+<p>黄金分割是指将整体一分为二，较大部分与整体部分的比值等于较小部分与较大部分的比值，其 比值 约为 0.618。这个比例被公认为是最能引起美感的 比例，因此被称为黄金分割。</p>
+</blockquote>
+<p>斐波那契查找特点：</p>
+<ul>
+<li>平均性能「斐波那契查找」好于「二分查找」；</li>
+<li>「斐波那契查找」计算 mid 的时候 使用加减法而不是除法，会微弱提升效率；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">FibonacciSearch</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// lookupTable,需要传入斐波那契数列,例如：{1,1,2,3,5,8,13,21,34,55};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">lookupTable</span><span class="p">,</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">f</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">target</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">low</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">high</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lookupTable</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// k 是 Fibonacci 分割数组下标</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">middle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="o">[</span><span class="n">k</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">high</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">k</span><span class="w"> </span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//利用 java 工具类构造 f[k] 长度的查找表，解决原有查找表元素不够的问题</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">temp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">lookupTable</span><span class="p">,</span><span class="n">f</span><span class="o">[</span><span class="n">k</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">low</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">high</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">middle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">low</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">f</span><span class="o">[</span><span class="n">k</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">lookupTable</span><span class="o">[</span><span class="n">middle</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">high</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">middle</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">k</span><span class="w"> </span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">lookupTable</span><span class="o">[</span><span class="n">middle</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">low</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">middle</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">k</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="k">else</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">middle</span><span class="p">,</span><span class="n">high</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="哈夫曼编码">哈夫曼编码</h3>
+<p>赫夫曼编码也翻译为哈夫曼编码(Huffman Coding)，又称霍夫曼编码，是一种编码方式，属于一种程序算法。</p>
+<p>哈夫曼编码是哈夫曼树在电讯通信中的经典的应用之一。哈夫曼编码广泛地用于数据文件压缩。其压缩率通常在20%～90%之间。哈夫曼码是可变字长编码的一种。Huffman于1952年提出一种编码方法，称之为最佳编码。</p>
+<blockquote>
+<p>定长编码与变长编码，以字符串like like为例：</p>
+<ul>
+<li>定长编码：</li>
+</ul>
+<ol>
+<li>将上述字符串转换对应的ASCII： 108 105 107 101 32 108 105 107 101</li>
+<li>ASCII转换为二进制：01101100 01101001 01101011 01100101 00100000 01101100 01101001 01101011 01100101
+<br></li>
+</ol>
+<ul>
+<li>变长编码：</li>
+</ul>
+<ol>
+<li>统计上述字符串出现的各字符出现的次数：l：2 i：2 k：2 e：2 ：1</li>
+<li>按照各个字符出现的次数进行编码，原则是出现次数越多的，则编码越小：0=l 1=i 10=k 11=e 100=</li>
+<li>最终转换为变长编码为：011011100011011</li>
+</ol>
+</blockquote>
+<p>上述的变长编码 011011100011011 在解码的时候会出现多意现象，比如当匹配到数字1，是把1解成i还是按照10来进行解码。因为这种现象的存在，所以在进行变长编码时，编码要符合前缀编码。</p>
+<blockquote>
+<p>字符的编码都不能是其他字符编码的前缀，符合此要求的编码叫做前缀编码， 即不能匹配到重复的编码。</p>
+</blockquote>
+<p>构建哈夫曼编码思路：</p>
+<ol>
+<li>统计字节数组中各个数据的权重,即字符出现的次数；</li>
+<li>将统计好的字符出现的次数，<a href="/iblog/posts/essays/data-structures-algorithms/#%E5%93%88%E5%A4%AB%E6%9B%BC%E6%A0%91">构建成哈夫曼树</a>；</li>
+<li>根据上面创建的哈夫曼树获得每个数值对应的可变长编码值，规定结点的左边为0 ，右边为1；</li>
+<li>以每个数值新的编码重新对字符数组进行编码，即可得到赫夫曼编码后的值；</li>
+</ol>
+<p>假如一段信息里只有A，B，C，D，E，F这6个字符，他们出现的次数依次是2次，3次，7次，9次，18次，25次，最终构建成哈夫曼编树为下图所示：</p>
+<p><img alt="数据结构与算法-029" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-029.png"></p>
+<p>得到哈夫曼编码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">A=11100 B=11101 C=1111 D=110 E=10 F=0
+</span></span></code></pre></div><p>利用哈夫曼编码，压缩解压文件：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HuffmanCodeTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 测试压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">srcFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/Desktop/1.png&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">dstFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/Desktop/1.zip&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">zipFile</span><span class="p">(</span><span class="n">srcFile</span><span class="p">,</span><span class="w"> </span><span class="n">dstFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;压缩文件成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 测试解压文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">srcFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/Desktop/1.zip&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dstFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/Desktop/1copy.png&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">unZipFile</span><span class="p">(</span><span class="n">srcFile</span><span class="p">,</span><span class="w"> </span><span class="n">dstFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;解压成功!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将一个文件进行压缩</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">zipFile</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">srcFile</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">dstFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建输出流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OutputStream</span><span class="w"> </span><span class="n">os</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建文件的输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FileInputStream</span><span class="w"> </span><span class="n">is</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建文件的输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">is</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">srcFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建一个和源文件大小一样的byte[]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">is</span><span class="p">.</span><span class="na">available</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 读取文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">is</span><span class="p">.</span><span class="na">read</span><span class="p">(</span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanCode</span><span class="w"> </span><span class="n">huffmanCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 直接对源文件压缩</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanCode</span><span class="p">.</span><span class="na">encode</span><span class="p">(</span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建文件的输出流, 存放压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">os</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="n">dstFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建一个和文件输出流关联的ObjectOutputStream</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="n">os</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 把 赫夫曼编码后的字节数组写入压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">huffmanBytes</span><span class="p">);</span><span class="w"> </span><span class="c1">// 我们是把</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 这里我们以对象流的方式写入 赫夫曼编码，是为了以后我们恢复源文件时使用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 注意一定要把赫夫曼编码 写入压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">huffmanCode</span><span class="p">.</span><span class="na">getHuffmanCodes</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// TODO: handle exception</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">is</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">oos</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">os</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// TODO: handle exception</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 完成对压缩文件的解压</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unZipFile</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">zipFile</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">dstFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 定义文件输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">InputStream</span><span class="w"> </span><span class="n">is</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 定义一个对象输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 定义文件的输出流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OutputStream</span><span class="w"> </span><span class="n">os</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建文件输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">is</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">zipFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建一个和 is关联的对象输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ois</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="n">is</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 读取byte数组 huffmanBytes</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 读取赫夫曼编码表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HuffmanCode</span><span class="w"> </span><span class="n">huffmanCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HuffmanCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 解码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanCode</span><span class="p">.</span><span class="na">decode</span><span class="p">(</span><span class="n">huffmanCodes</span><span class="p">,</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将bytes 数组写入到目标文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">os</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="n">dstFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 写数据到 dstFile 文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">os</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="n">bytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// TODO: handle exception</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">os</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">ois</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">is</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// TODO: handle exception</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e2</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HuffmanCode</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getHuffmanCodes</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 生成 huffman 编码 压缩</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="nf">encode</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildHuffmanNodes</span><span class="p">(</span><span class="n">bytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">huffmanTreeRoot</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildHuffmanTree</span><span class="p">(</span><span class="n">nodes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">huffmanTreeRoot</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">zip</span><span class="p">(</span><span class="n">bytes</span><span class="p">,</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将 huffman编码 解码 解压缩</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="nf">decode</span><span class="p">(</span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">,</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">stringBuilder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将byte数组转成二进制的字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">strToAppend</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">byteToBitString</span><span class="p">(</span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断是不是最后一个字节</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isLastByte</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isLastByte</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 得到最后一个字节的有效位数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">byte</span><span class="w"> </span><span class="n">validBits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">huffmanBytes</span><span class="o">[</span><span class="n">huffmanBytes</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">strToAppend</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">strToAppend</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">validBits</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">strToAppend</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 把字符串按照指定的赫夫曼编码进行解码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 把赫夫曼编码表进行调换，因为反向查询 a-&gt;100 100-&gt;a</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Byte</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">huffmanCodes</span><span class="p">.</span><span class="na">forEach</span><span class="p">((</span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建要给集合，存放byte</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Byte</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// i 可以理解成就是索引,扫描 stringBuilder</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 递增的取出 key</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">String</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">count</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">b</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 没有匹配到</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 匹配到</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">i</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">IntStream</span><span class="p">.</span><span class="na">range</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">.</span><span class="na">length</span><span class="p">).</span><span class="na">forEach</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">b</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算字符串中每个字符出现的次数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">buildHuffmanNodes</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 利用map记录集合中元素出现的次数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">counts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">counts</span><span class="p">.</span><span class="na">merge</span><span class="p">(</span><span class="n">b</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">::</span><span class="n">sum</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 把每一个键值对转成一个Node 对象，并加入到nodes集合</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">counts</span><span class="p">.</span><span class="na">forEach</span><span class="p">((</span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构建Huffman树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">buildHuffmanTree</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">nodes</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 排序, 从小到大</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Collections</span><span class="p">.</span><span class="na">sort</span><span class="p">(</span><span class="n">nodes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 取出第一颗最小的二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">leftNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 取出第二颗最小的二叉树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">rightNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 创建一颗新的二叉树,它的根节点 没有data, 只有权值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="w"> </span><span class="n">parent</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">leftNode</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">rightNode</span><span class="p">.</span><span class="na">weight</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">parent</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">leftNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">parent</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rightNode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将已经处理的两颗二叉树从nodes删除</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">nodes</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">leftNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">nodes</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">rightNode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将新的二叉树，加入到nodes</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">nodes</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">parent</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// nodes 最后的结点，就是赫夫曼树的根结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 重载 getCodes</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">root</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">root</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理root的左子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">root</span><span class="p">.</span><span class="na">left</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;0&#34;</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理root的右子树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">root</span><span class="p">.</span><span class="na">right</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取huffman编码表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">code</span><span class="p">,</span><span class="w"> </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">curNodeCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">(</span><span class="n">stringBuilder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">curNodeCode</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">code</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断当前node 是叶子结点还是非叶子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">data</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// 非叶子结点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 向左递归</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">left</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;0&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">curNodeCode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 向右递归</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">buildHuffmanCodeTab</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">right</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">curNodeCode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 表示找到某个叶子结点的最后</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">huffmanCodes</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">node</span><span class="p">.</span><span class="na">data</span><span class="p">,</span><span class="w"> </span><span class="n">curNodeCode</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 压缩传入字节（将传入字符串转成字节类型）将待压缩字节转换为字节数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="nf">zip</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">,</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">huffmanCodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 利用 huffmanCodes 将 bytes 转成 赫夫曼编码对应的字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">stringBuilder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历bytes 数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">huffmanCodes</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">b</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 统计返回 byte[] huffmanCodeBytes 长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 等同于 int len = (stringBuilder.length() + 7) / 8;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="w"> </span><span class="n">countToEight</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">countToEight</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">3</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 后面补零</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">countToEight</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">8</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="s">&#34;0&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建 存储压缩后的 byte数组，huffmanCodeBytes[len]记录赫夫曼编码最后一个字节的有效位数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">huffmanCodeBytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">len</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">huffmanCodeBytes</span><span class="o">[</span><span class="n">len</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">countToEight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 因为是每8位对应一个byte,所以步长 +8</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">8</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">strByte</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">strByte</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stringBuilder</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">8</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将strByte 转成一个byte,放入到 huffmanCodeBytes</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">huffmanCodeBytes</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">parseInt</span><span class="p">(</span><span class="n">strByte</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">huffmanCodeBytes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将 byte 转换为对应的字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">byteToBitString</span><span class="p">(</span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">temp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果是正数我们需要将高位补零</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">temp</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">0x100</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 转换为二进制字符串，正数：高位补 0 即可，然后截取低八位即可；负数直接截取低八位即可</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 负数在计算机内存储的是补码，补码转原码：先 -1 ，再取反</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">binaryStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">toBinaryString</span><span class="p">(</span><span class="n">temp</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">binaryStr</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">binaryStr</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">8</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Node</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Comparable</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Byte</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Node</span><span class="p">(</span><span class="n">Byte</span><span class="w"> </span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">compareTo</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">o</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 从小到大排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">o</span><span class="p">.</span><span class="na">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Node [data = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; weight=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">weight</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;]&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="分治算法">分治算法</h3>
+<p>分治法是一种很重要的算法。字面上的解释是“分而治之”，就是把一个复杂的问题分成两个或更多的相同或相似的子问题，再把子问题分成更小的子问题……直到最后子问题可以简单的直接求解，原问题的解即子问题的解的合并。这个技巧是很多高效算法的基础，如排序算法(快速排序，归并排序)，傅立叶变换(快速傅立叶变换)……</p>
+<p>分治法的设计思想是：将一个难以直接解决的大问题，分割成一些规模较小的相同问题，以便各个击破，分而治之。</p>
+<p>使用分治算饭解决汉诺塔问题</p>
+<blockquote>
+<p>汉诺塔（又称河内塔）问题是源于印度一个古老传说的益智玩具。大梵天创造世界的时候做了三根金刚石柱子，在一根柱子上从下往上按照大小顺序摞着64片黄金圆盘。大梵天命令婆罗门把圆盘从下面开始按大小顺序重新摆放在另一根柱子上。并且规定，在小圆盘上不能放大圆盘，在三根柱子之间一次只能移动一个圆盘。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HanoiTowerDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HanoiTower</span><span class="w"> </span><span class="n">hanoiTower</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HanoiTower</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hanoiTower</span><span class="p">.</span><span class="na">hanoiTower</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HanoiTower</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">hanoiTower</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">b</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">c</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将a塔上面除了底盘外的所有盘移动到b塔</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hanoiTower</span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">c</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将a塔遗留的底盘移动到c塔</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-&gt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将b塔上面的所有盘移动到c塔</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hanoiTower</span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="动态规划算法">动态规划算法</h3>
+<p>动态规划(Dynamic Programming)算法的核心思想是：将大问题划分为小问题进行解决，从而一步步获取最优解的处理算法。</p>
+<p>动态规划算法与分治算法类似，其基本思想也是将待求解问题分解成若干个子问题，先求解子问题，然后从这些子问题的解得到原问题的解。与分治法不同的是，适合于用动态规划求解的问题，经分解得到子问题往往不是互相独立的。 ( 即下一个子阶段的求解是建立在上一个子阶段的解的基础上，进行进一步的求解 )</p>
+<p>关于动态规划最经典的问题当属背包问题。</p>
+<blockquote>
+<p>背包问题主要是指一个给定容量的背包、若干具有一定价值和重量的物品，如何选择物品放入背包使物品的价值最大。其中又分01背包和完全背包(完全背包指的是：每种物品都有无限件可用)这里的问题属于01背包，即每个物品最多放一个。而无限背包可以转化为01背包。</p>
+<table>
+<thead>
+<tr>
+<th>物品</th>
+<th>重量</th>
+<th>价格</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>吉他(G)</td>
+<td>1</td>
+<td>1500</td>
+</tr>
+<tr>
+<td>音响(S)</td>
+<td>4</td>
+<td>3000</td>
+</tr>
+<tr>
+<td>电脑(L)</td>
+<td>3</td>
+<td>2000</td>
+</tr>
+</tbody>
+</table>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">KnapsackProblemDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">KnapsackProblem</span><span class="w"> </span><span class="n">knapsackProblem</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">KnapsackProblem</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">knapsackProblem</span><span class="p">.</span><span class="na">knapsackProblem</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">KnapsackProblem</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">knapsackProblem</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 物品的重量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">w</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 物品的价值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1500</span><span class="p">,</span><span class="w"> </span><span class="n">3000</span><span class="p">,</span><span class="w"> </span><span class="n">2000</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 背包的容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 物品的个数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">val</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 物品规划表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">m</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将v[][] 第一列和第一行重置为0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">v</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">v</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="o">[</span><span class="n">0</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理 生成物品价格表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">v</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">v</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 如果当前商品的重量 是否能写入当前表格中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">w</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">val</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">v</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">][</span><span class="n">j</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">w</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理完后 v[][] 表中数值最大的就是最后的结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ints</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">v</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">ints</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">anInt</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">ints</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">anInt</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">max</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">anInt</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">max</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="kmp算法">KMP算法</h3>
+<blockquote>
+<p>KMP算法是一种改进的字符串匹配算法，由D.E.Knuth，J.H.Morris和V.R.Pratt提出的，因此人们称它为克努特—莫里斯—普拉特操作（简称KMP算法）。KMP算法的核心是利用匹配失败后的信息，尽量减少模式串与主串的匹配次数以达到快速匹配的目的。具体实现就是通过一个next()函数实现，函数本身包含了模式串的局部匹配信息。KMP算法的时间复杂度O(m+n)。</p>
+</blockquote>
+<ul>
+<li>
+<p>常规算法匹配字符串</p>
+<p><img alt="数据结构与算法-042" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-042.gif"></p>
+<p>从主串的起始位置（或指定位置）开始与模式串的第一个字符比较，若相等，则继续逐个比较后续字符；否则从主串的下一个字符再重新和模式串的字符比较。依次类推，直到模式串成功匹配，返回主串中第一次出现模式串字符的位置，或者模式串匹配不成功，这里约定返回-1。</p>
+</li>
+<li>
+<p>KMP算法匹配字符串</p>
+<p><img alt="数据结构与算法-043" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-043.gif"></p>
+<p>主要就是改进了暴力匹配中i回溯的操作，KMP算法中当一趟匹配过程中出现字符比较不等时，不直接回溯i，而是利用已经得到的“部分匹配”的结果将模式串向右移动（j-next[j-1]）的距离。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">KMPDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">KMP</span><span class="w"> </span><span class="n">kmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">KMP</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;BBC ABCDAB ABCDABCDABDE&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;ABCDABD&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">kmp</span><span class="p">.</span><span class="na">getMatchTab</span><span class="p">(</span><span class="n">str2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">next</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">kmp</span><span class="p">.</span><span class="na">kmpSearch</span><span class="p">(</span><span class="n">str1</span><span class="p">,</span><span class="w"> </span><span class="n">str2</span><span class="p">,</span><span class="w"> </span><span class="n">next</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">KMP</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取KMP 部分匹配表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="nf">getMatchTab</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">dest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">dest</span><span class="p">.</span><span class="na">length</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 部分匹配表第一个值始终为0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">result</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">result</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// KMP 核心（特点，公式）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">j</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">dest</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">dest</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">j</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">result</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">dest</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">dest</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">j</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">result</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">j</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * KMP查找算法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param str1 原字符串
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param str2 子字符串
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param next 部分匹配表
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 匹配到字符串的第一个索引位置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">kmpSearch</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">next</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">str1</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">j</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">str1</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">str2</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">j</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">str1</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str2</span><span class="p">.</span><span class="na">charAt</span><span class="p">(</span><span class="n">j</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">j</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">j</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str2</span><span class="p">.</span><span class="na">length</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="贪心算法">贪心算法</h3>
+<p>贪心算法又称贪婪算法，是指在对问题进行求解时，在每一步选择中都采取最好或者最优(即最有利)的选择，从而希望能够导致结果是最好或者最优的算法。贪婪算法所得到的结果不一定是最优的结果(有时候会是最优解)，但是都是相对近似(接近)最优解的结果。</p>
+<p>举例，假设存在下面需要付费的广播台，以及广播台信号可以覆盖的地区。 如何选择最少的广播台，让所有的地区都可以接收到信号。</p>
+<table>
+<thead>
+<tr>
+<th>广播台</th>
+<th>覆盖地区</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>K1</td>
+<td>“北京”, “上海”, “天津”</td>
+</tr>
+<tr>
+<td>K2</td>
+<td>“广州”, “北京”, “深圳”</td>
+</tr>
+<tr>
+<td>K3</td>
+<td>“成都”, “上海”, “杭州”</td>
+</tr>
+<tr>
+<td>K4</td>
+<td>“上海”, “天津”</td>
+</tr>
+<tr>
+<td>K5</td>
+<td>“杭州”, “大连”</td>
+</tr>
+</tbody>
+</table>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GreedyAlgorithmDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">broadcasts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;北京&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;上海&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;天津&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet2</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;广州&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet2</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;北京&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet2</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;深圳&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet3</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;成都&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet3</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;上海&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet3</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;杭州&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet4</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;上海&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet4</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;天津&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet5</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;杭州&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashSet5</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;大连&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K1&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K2&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K3&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K4&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;K5&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">hashSet5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// allAreas 存放所有的地区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allAreas</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Map</span><span class="p">.</span><span class="na">Entry</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">broadcast</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">entrySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">allAreas</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">broadcast</span><span class="p">.</span><span class="na">getValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">GreedyAlgorithm</span><span class="p">().</span><span class="na">getRadioByGreedyAlgorithm</span><span class="p">(</span><span class="n">allAreas</span><span class="p">,</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">GreedyAlgorithm</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getRadioByGreedyAlgorithm</span><span class="p">(</span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allAreas</span><span class="p">,</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存放选择的电台</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">selects</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存放每次选择最优的电台</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">maxKey</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 临时集合 从 broadcasts 中选出能覆盖的电台，即存放 allAreas 与 broadcasts 的交集</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">tmpSet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">allAreas</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 每次需要清空</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">maxKey</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">keySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpSet</span><span class="p">.</span><span class="na">clear</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpSet</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">broadcasts</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 计算覆盖的电台 并赋值给tmpSet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tmpSet</span><span class="p">.</span><span class="na">retainAll</span><span class="p">(</span><span class="n">allAreas</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 此处进行比较 体现贪心算法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tmpSet</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">maxKey</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">tmpSet</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">broadcasts</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">maxKey</span><span class="p">).</span><span class="na">size</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">maxKey</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 每进行一次循环最后需要移除选中的maxKey对应的电台城市</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">maxKey</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">selects</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">maxKey</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">allAreas</span><span class="p">.</span><span class="na">removeAll</span><span class="p">(</span><span class="n">broadcasts</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">maxKey</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">selects</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="普里姆算法">普里姆算法</h3>
+<p>普里姆算法（Prim算法），图论中的一种算法，可在加权连通图里搜索<strong>最小生成树</strong>。意即由此算法搜索到的边子集所构成的树中，不但包括了连通图里的所有顶点，且其所有边的权值之和亦为最小。</p>
+<blockquote>
+<p>最小生成树：给定一个带权的无向连通图，如何选取一棵生成树，使树上所有边上权的总和为最小，这叫最小生成树。简称MST。
+求最小生成树的算法主要是普里姆算法和克鲁斯卡尔算法。</p>
+<ul>
+<li>普里姆算法：O(n^2),适合稠密图（边多的图）</li>
+<li>克鲁斯卡尔算法:O,适合稀疏图（边少的图）</li>
+</ul>
+</blockquote>
+<p>普利姆(Prim)算法求最小生成树，也就是在包含n个顶点的连通图中，找出只有(n-1)条边包含所有n个顶点的连通子图，也就是所谓的极小连通子图。</p>
+<p><img alt="数据结构与算法-044" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-044.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class PrimAlgorithmDemo {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        char[] data = new char[]{&#39;A&#39;, &#39;B&#39;, &#39;C&#39;, &#39;D&#39;, &#39;E&#39;, &#39;F&#39;, &#39;G&#39;};
+</span></span><span class="line"><span class="cl">        int vertex = data.length;
+</span></span><span class="line"><span class="cl">        //邻接矩阵的关系使用二维数组表示,10000这个大数，表示两个点不联通
+</span></span><span class="line"><span class="cl">        int[][] weight = new int[][]{
+</span></span><span class="line"><span class="cl">                {10000, 5, 7, 10000, 10000, 10000, 2},
+</span></span><span class="line"><span class="cl">                {5, 10000, 10000, 9, 10000, 10000, 3},
+</span></span><span class="line"><span class="cl">                {7, 10000, 10000, 10000, 8, 10000, 10000},
+</span></span><span class="line"><span class="cl">                {10000, 9, 10000, 10000, 10000, 4, 10000},
+</span></span><span class="line"><span class="cl">                {10000, 10000, 8, 10000, 10000, 5, 4},
+</span></span><span class="line"><span class="cl">                {10000, 10000, 10000, 4, 5, 10000, 6},
+</span></span><span class="line"><span class="cl">                {2, 3, 10000, 10000, 4, 6, 10000}
+</span></span><span class="line"><span class="cl">        };
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        MGraph graph = new MGraph(vertex);
+</span></span><span class="line"><span class="cl">        PrimAlgorithm minTree = new PrimAlgorithm();
+</span></span><span class="line"><span class="cl">        graph.create(graph, vertex, data, weight);
+</span></span><span class="line"><span class="cl">        graph.show(graph);
+</span></span><span class="line"><span class="cl">        minTree.prim(graph, 0);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">class PrimAlgorithm {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    /**
+</span></span><span class="line"><span class="cl">     * 最小生成树问题 prim算法
+</span></span><span class="line"><span class="cl">     *
+</span></span><span class="line"><span class="cl">     * @param graph  图对象
+</span></span><span class="line"><span class="cl">     * @param vertex 开始的顶点
+</span></span><span class="line"><span class="cl">     */
+</span></span><span class="line"><span class="cl">    public void prim(MGraph graph, int vertex) {
+</span></span><span class="line"><span class="cl">        int i = 0, j = 0;
+</span></span><span class="line"><span class="cl">        int row = -1, column = -1;
+</span></span><span class="line"><span class="cl">        // 存放已经访问过的顶点
+</span></span><span class="line"><span class="cl">        int[] visited = new int[graph.vertex];
+</span></span><span class="line"><span class="cl">        // 用1表示两点之间已经连接， 0表示未连接
+</span></span><span class="line"><span class="cl">        visited[vertex] = 1;
+</span></span><span class="line"><span class="cl">        int minWeight = 10000;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        for (int k = 1; k &lt; graph.vertex; k++){
+</span></span><span class="line"><span class="cl">            // 比较两点之间的权值，每次都获取最小的权值
+</span></span><span class="line"><span class="cl">            for (i = 0; i &lt; graph.vertex; i++) {
+</span></span><span class="line"><span class="cl">                for(j = 0; j &lt; graph.vertex; j++){
+</span></span><span class="line"><span class="cl">                    if (visited[i] == 1 &amp;&amp; visited[j] == 0 &amp;&amp; graph.weight[i][j] &lt; minWeight){
+</span></span><span class="line"><span class="cl">                        minWeight = graph.weight[i][j];
+</span></span><span class="line"><span class="cl">                        row = i;
+</span></span><span class="line"><span class="cl">                        column = j;
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;边&lt;&#34; + graph.data[row] + &#34;,&#34; + graph.data[column] + &#34;&gt; 权值:&#34; + minWeight);
+</span></span><span class="line"><span class="cl">            // 将顶点标记为已经访问过
+</span></span><span class="line"><span class="cl">            visited[column] = 1;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 每次比较完后需要将minWeight重置
+</span></span><span class="line"><span class="cl">            minWeight = 10000;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">class MGraph {
+</span></span><span class="line"><span class="cl">    int vertex;
+</span></span><span class="line"><span class="cl">    char[] data;
+</span></span><span class="line"><span class="cl">    int[][] weight;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public MGraph(int vertex) {
+</span></span><span class="line"><span class="cl">        this.vertex = vertex;
+</span></span><span class="line"><span class="cl">        data = new char[vertex];
+</span></span><span class="line"><span class="cl">        weight = new int[vertex][vertex];
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    /**
+</span></span><span class="line"><span class="cl">     * 创建图的邻接矩阵
+</span></span><span class="line"><span class="cl">     *
+</span></span><span class="line"><span class="cl">     * @param graph  图对象
+</span></span><span class="line"><span class="cl">     * @param vertex 图对应的顶点个数
+</span></span><span class="line"><span class="cl">     * @param data   图的各个顶点的值
+</span></span><span class="line"><span class="cl">     * @param weight 图的邻接矩阵
+</span></span><span class="line"><span class="cl">     */
+</span></span><span class="line"><span class="cl">    public void create(MGraph graph, int vertex, char[] data, int[][] weight) {
+</span></span><span class="line"><span class="cl">        int i, j;
+</span></span><span class="line"><span class="cl">        for (i = 0; i &lt; vertex; i++) {
+</span></span><span class="line"><span class="cl">            graph.data[i] = data[i];
+</span></span><span class="line"><span class="cl">            for (j = 0; j &lt; vertex; j++) {
+</span></span><span class="line"><span class="cl">                graph.weight[i][j] = weight[i][j];
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 显示图的邻接矩阵
+</span></span><span class="line"><span class="cl">    public void show(MGraph graph) {
+</span></span><span class="line"><span class="cl">        for (int[] link : graph.weight) {
+</span></span><span class="line"><span class="cl">            System.out.println(Arrays.toString(link));
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="克鲁斯卡尔算法">克鲁斯卡尔算法</h3>
+<p>克鲁斯卡尔算法是求连通网的最小生成树的另一种方法。基本思想是， 将所有边按照权值的大小进行升序排序，然后从小到大一一判断，条件为：如果这个边不会与之前选择的所有边组成回路，就可以作为最小生成树的一部分；反之，舍去。 直到具有 n 个顶点的连通网筛选出来 n-1（n为顶点个数） 条边为止。</p>
+<blockquote>
+<p>判断是否构成回路: 当每次需要将一条边添加到最小生成树时，判断该边的两个顶点终点是否相同，相同就会构成回路。</p>
+<p>关于终点的说明：就是将所有顶点按照从小到大的顺序排列好之后；某个顶点的终点就是与它连通的最大顶点。 就是将所有顶点按照从小到大的顺序排列好之后；某个顶点的终点就是与它连通的最大顶点。</p>
+<p>举例</p>
+<ul>
+<li>首先ABCDEFG这7个顶点，在顶点集合中是按照顺序存放的；</li>
+<li>第一次选择的是EF，毫无疑问这一条边的终点是F；</li>
+<li>第二次选择的CD的终点D；</li>
+<li>第三次选择的DE，终点是F，因为此时D和E相连，D又和F相连，所以D的终点是F。而且，因为C和D是相连的，D和E相连，E和F也是相连的，所以C的终点此时变成了F。也就是说，当选择了EF、CD、DE这三条边后，C、D、E的终点都是F。当然F的终点也是F，因为F还没和后面的哪个顶点连接。</li>
+<li>本来接下来应该选择CE的，但是由于C和E的终点都是F，所以就会形成回路；</li>
+</ul>
+</blockquote>
+<p><img alt="数据结构与算法-045" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-045.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">KruskalCaseDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//使用 INF 表示两个顶点不能连通</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">INF</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertexs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;D&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;E&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;F&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;G&#39;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">matrix</span><span class="o">[][]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*A*//*B*//*C*//*D*//*E*//*F*//*G*/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*A*/</span><span class="w"> </span><span class="p">{</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">12</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">16</span><span class="p">,</span><span class="w"> </span><span class="n">14</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*B*/</span><span class="w"> </span><span class="p">{</span><span class="n">12</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*C*/</span><span class="w"> </span><span class="p">{</span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*D*/</span><span class="w"> </span><span class="p">{</span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*E*/</span><span class="w"> </span><span class="p">{</span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*F*/</span><span class="w"> </span><span class="p">{</span><span class="n">16</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="cm">/*G*/</span><span class="w"> </span><span class="p">{</span><span class="n">14</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">INF</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">}};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">KruskalCase</span><span class="w"> </span><span class="n">kruskalCase</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">KruskalCase</span><span class="p">(</span><span class="n">vertexs</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">kruskalCase</span><span class="p">.</span><span class="na">print</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">kruskalCase</span><span class="p">.</span><span class="na">kruskal</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">KruskalCase</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//使用 INF 表示两个顶点不能连通</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">INF</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">edgeNum</span><span class="p">;</span><span class="w"> </span><span class="c1">//边的个数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertexs</span><span class="p">;</span><span class="w"> </span><span class="c1">//顶点数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="p">;</span><span class="w"> </span><span class="c1">//邻接矩阵</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构造器</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">KruskalCase</span><span class="p">(</span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertexs</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始化顶点数和边的个数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">vlen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始化顶点, 复制拷贝的方式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">vertexs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">char</span><span class="o">[</span><span class="n">vlen</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">vertexs</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertexs</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始化边, 使用的是复制拷贝的方式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">matrix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">vlen</span><span class="o">][</span><span class="n">vlen</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vlen</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vlen</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 统计边的条数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vlen</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vlen</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">INF</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">edgeNum</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">print</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;邻接矩阵为: \n&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%12d&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能：对边进行排序处理, 冒泡排序
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param edges 边的集合
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sortEdges</span><span class="p">(</span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="n">edges</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">edges</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">edges</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">.</span><span class="na">weight</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">EdgeData</span><span class="w"> </span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">edges</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param ch 顶点的值，比如&#39;A&#39;,&#39;B&#39;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回ch顶点对应的下标，如果找不到，返回-1
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getPosition</span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">vertexs</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 找不到,返回-1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 获取图中边，放到EData[] 数组中，后面我们需要遍历该数组
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 是通过matrix 邻接矩阵来获取
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * EData[] 形式 [[&#39;A&#39;,&#39;B&#39;, 12], [&#39;B&#39;,&#39;F&#39;,7], .....]
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="nf">getEdges</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="n">edges</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EdgeData</span><span class="o">[</span><span class="n">edgeNum</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">INF</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">edges</span><span class="o">[</span><span class="n">index</span><span class="o">++]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EdgeData</span><span class="p">(</span><span class="n">vertexs</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">vertexs</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">edges</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 获取下标为i的顶点的终点, 用于后面判断两个顶点的终点是否相同
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param ends ： 数组就是记录了各个顶点对应的终点是哪个,ends 数组是在遍历过程中，逐步形成
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param i    : 表示传入的顶点对应的下标
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回的就是 下标为i的这个顶点对应的终点的下标, 一会回头还有来理解
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getEnd</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ends</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// i = 4 [0,0,0,0,5,0,0,0,0,0,0,0]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">ends</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ends</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">kruskal</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 用于保存&#34;已有最小生成树&#34; 中的每个顶点在最小生成树中的终点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ends</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">vertexs</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建结果数组, 保存最后的最小生成树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="n">rets</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EdgeData</span><span class="o">[</span><span class="n">edgeNum</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取图中 所有的边的集合 ， 一共有12边</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EdgeData</span><span class="o">[]</span><span class="w"> </span><span class="n">edges</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getEdges</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 按照边的权值大小进行排序(从小到大)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sortEdges</span><span class="p">(</span><span class="n">edges</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 遍历edges 数组，将边添加到最小生成树中时，判断是准备加入的边否形成了回路，如果没有，就加入 rets, 否则不能加入</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">edgeNum</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取到第i条边的第一个顶点(起点)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">point1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getPosition</span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">.</span><span class="na">start</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取到第i条边的第2个顶点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">point2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getPosition</span><span class="p">(</span><span class="n">edges</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">.</span><span class="na">end</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取p1这个顶点在已有最小生成树中的终点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">endPointOfPoint1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getEnd</span><span class="p">(</span><span class="n">ends</span><span class="p">,</span><span class="w"> </span><span class="n">point1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取p2这个顶点在已有最小生成树中的终点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">endPointOfPoint2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getEnd</span><span class="p">(</span><span class="n">ends</span><span class="p">,</span><span class="w"> </span><span class="n">point2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 克鲁斯卡尔核心点：判断是否构成回路</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">endPointOfPoint1</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">endPointOfPoint2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 假设没有构成回路</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将该边上终点上的值赋值给起点位置的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">ends</span><span class="o">[</span><span class="n">endPointOfPoint1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">endPointOfPoint2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将该边保存起来</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">rets</span><span class="o">[</span><span class="n">index</span><span class="o">++]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">edges</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;最小生成树为&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">rets</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">EdgeData</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">char</span><span class="w"> </span><span class="n">start</span><span class="p">;</span><span class="w"> </span><span class="c1">// 边的一个点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">char</span><span class="w"> </span><span class="n">end</span><span class="p">;</span><span class="w"> </span><span class="c1">// 边的另外一个点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w"> </span><span class="c1">// 边的权值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">EdgeData</span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">end</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">weight</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">start</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">end</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">end</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">weight</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">weight</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 重写toString, 便于输出边信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;EData [&lt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&gt;= &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">weight</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;]&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="迪杰斯特拉算法">迪杰斯特拉算法</h3>
+<p>迪杰斯特拉算法是典型最短路径算法，用于计算一个结点到其他结点的最短路径。迪杰斯特拉算法是基于贪心思想，从起始位置触发，每次寻找与起点位置距离且未访问过的顶点，以该顶点作为中间结点，更新从起点到其他顶点的距离，直到全部顶点都作为了中间结点，并完成了路径更新，算法结束。 它的主要特点是以起始点为中心向外层层扩展，即图的广度优先搜索思想，直到扩展到终点为止。</p>
+<p>视频讲解：<a href="https://www.bilibili.com/video/BV1uX4y137Hf">bilibili</a></p>
+<p><img alt="数据结构与算法-046" src="/iblog/posts/annex/images/essays/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E4%B8%8E%E7%AE%97%E6%B3%95-046.gif"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DijkstraAlgorithmDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;D&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;E&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;F&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;G&#39;</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="o">][</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 表示不可以连接</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">65535</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">3</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">4</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">6</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Graph</span><span class="w"> </span><span class="n">graph</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Graph</span><span class="p">(</span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">graph</span><span class="p">.</span><span class="na">showGraph</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">graph</span><span class="p">.</span><span class="na">dsj</span><span class="p">(</span><span class="n">6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Graph</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">VisitedVertex</span><span class="w"> </span><span class="n">vv</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构造器</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Graph</span><span class="p">(</span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">matrix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">matrix</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 显示结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showDijkstra</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vv</span><span class="p">.</span><span class="na">showArrays</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 显示图</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showGraph</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">link</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">matrix</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">link</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%8d&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 迪杰斯特拉算法实现
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index 表示出发顶点对应的下标
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dsj</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vv</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">VisitedVertex</span><span class="p">(</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">update</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vv</span><span class="p">.</span><span class="na">showArrays</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vv</span><span class="p">.</span><span class="na">findNextStartPoint</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">update</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">vv</span><span class="p">.</span><span class="na">showArrays</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 更新index下标顶点到周围顶点的距离和周围顶点的前驱顶点,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 根据遍历我们的邻接矩阵的 matrix[index]行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// len 含义是 : 出发顶点到index顶点的距离 + 从index顶点到j顶点的距离的和</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vv</span><span class="p">.</span><span class="na">getDis</span><span class="p">(</span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">matrix</span><span class="o">[</span><span class="n">index</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果j顶点没有被访问过，并且 len 小于出发顶点到j顶点的距离，就需要更新</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">vv</span><span class="p">.</span><span class="na">isVisited</span><span class="p">(</span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">vv</span><span class="p">.</span><span class="na">getDis</span><span class="p">(</span><span class="n">j</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">vv</span><span class="p">.</span><span class="na">updatePre</span><span class="p">(</span><span class="n">j</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">vv</span><span class="p">.</span><span class="na">updateDis</span><span class="p">(</span><span class="n">j</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">VisitedVertex</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">alreadyArr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">preVisited</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">dis</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param length :表示顶点的个数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index: 出发顶点对应的下标, 比如G顶点，下标就是6
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">VisitedVertex</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">alreadyArr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">preVisited</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dis</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始化 dis数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Arrays</span><span class="p">.</span><span class="na">fill</span><span class="p">(</span><span class="n">dis</span><span class="p">,</span><span class="w"> </span><span class="n">65535</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dis</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">alreadyArr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 判断index顶点是否被访问过
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 如果访问过，就返回true, 否则访问false
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isVisited</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alreadyArr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 更新出发顶点到index顶点的距离
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">updateDis</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dis</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能: 更新pre这个顶点的前驱顶点为index顶点
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">updatePre</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">pre</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">preVisited</span><span class="o">[</span><span class="n">pre</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 功能:返回出发顶点到index顶点的距离
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getDis</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 继续选择并返回新的访问顶点， 比如这里的G 完后，就是 A点作为新的访问顶点(注意不是出发顶点)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">findNextStartPoint</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">65535</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">alreadyArr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alreadyArr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">min</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 更新 index 顶点被访问过</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alreadyArr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//显示最后的结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showArrays</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;核心数组的值如下：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">alreadyArr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">dis</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">preVisited</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;D&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;E&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;F&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;G&#39;</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">dis</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">65535</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">vertex</span><span class="o">[</span><span class="n">count</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;(&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;) &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;N &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="弗洛伊德算法">弗洛伊德算法</h3>
+<p>弗洛伊德算法又称为插点法，是一种利用动态规划的思想寻找给定的加权图中多源点之间最短路径的算法，与迪杰斯特拉算法类似。</p>
+<blockquote>
+<p>迪杰斯特拉算法对比弗洛伊德算法：
+迪杰斯特拉算法通过选定的被访问顶点，求出从出发访问顶点到其他顶点的最短路径；弗洛伊德算法中每一个顶点都是出发访问点，所以需要将每一个顶点看做被访问顶点，求出从每一个顶点到其他顶点的最短路径。</p>
+<ul>
+<li>弗洛伊德算法计算图中各个顶点之间的最短路径</li>
+<li>迪杰斯特拉算法用于计算图中某一个顶点到其他顶点的最短路径</li>
+</ul>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FloydAlgorithmDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="sc">&#39;A&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;B&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;C&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;D&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;E&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;F&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;G&#39;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">matrix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="o">][</span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">65535</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">3</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">4</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">8</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">matrix</span><span class="o">[</span><span class="n">6</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FloydGraph</span><span class="w"> </span><span class="n">graph</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FloydGraph</span><span class="p">(</span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="n">vertex</span><span class="p">.</span><span class="na">length</span><span class="p">,</span><span class="w"> </span><span class="n">matrix</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">graph</span><span class="p">.</span><span class="na">floyd</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">graph</span><span class="p">.</span><span class="na">show</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">FloydGraph</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">pre</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">dis</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">FloydGraph</span><span class="p">(</span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">vertex</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">dis</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">vertex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">vertex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dis</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dis</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">pre</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">length</span><span class="o">][</span><span class="n">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Arrays</span><span class="p">.</span><span class="na">fill</span><span class="p">(</span><span class="n">pre</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">show</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">k</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 先将pre数组输出的一行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">vertex</span><span class="o">[</span><span class="n">pre</span><span class="o">[</span><span class="n">k</span><span class="o">][</span><span class="n">i</span><span class="o">]]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 输出dis数组的一行数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;(&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">vertex</span><span class="o">[</span><span class="n">k</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;到&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">vertex</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;的最短路径是&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">k</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;) &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">floyd</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">m</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">a</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">b</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">a</span><span class="o">][</span><span class="n">m</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">m</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">len</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">dis</span><span class="o">[</span><span class="n">a</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">dis</span><span class="o">[</span><span class="n">a</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">len</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">pre</span><span class="o">[</span><span class="n">a</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pre</span><span class="o">[</span><span class="n">m</span><span class="o">][</span><span class="n">b</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="马踏棋盘算法">马踏棋盘算法</h3>
+<p>马踏棋盘算法也被称为骑士周游问题。将马随机放在国际象棋的8×8棋盘0～7的某个方格中，马按走棋规则(马走日字)进行移动。要求每个方格只进入一次，走遍棋盘上全部64个方格。</p>
+<p>马踏棋盘问题实际上是图的深度优先搜索(DFS)的应用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HouseChessBoardDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HouseChessBoard</span><span class="w"> </span><span class="n">houseChessBoard</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HouseChessBoard</span><span class="p">(</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">houseChessBoard</span><span class="p">.</span><span class="na">showChessBoard</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">HouseChessBoard</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 表示棋盘的列
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 表示棋盘的行
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 创建一个数组，标记棋盘的各个位置是否被访问过，true表示已经访问过
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">visited</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 使用一个属性，标记是否棋盘的所有位置都被访问 如果为true,表示成功
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">finished</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">chessboard</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">HouseChessBoard</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">y</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">column</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">visited</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">x</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">y</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">chessboard</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">x</span><span class="o">][</span><span class="n">y</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">traversalChess</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">chessboard</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="o">-</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">column</span><span class="o">-</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showChessBoard</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">ints</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">chessboard</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">anInt</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">ints</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">anInt</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">traversalChess</span><span class="p">(</span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">chessboard</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">column</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">step</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">chessboard</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">step</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将当前位置标记为已经访问过</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">visited</span><span class="o">[</span><span class="n">row</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取当前位置的下一个可走通的位置的集合</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextPos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNext</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">column</span><span class="p">,</span><span class="w"> </span><span class="n">row</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sort</span><span class="p">(</span><span class="n">nextPos</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">nextPos</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取当前可走通的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Point</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nextPos</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断当前该点是否被访问过,如果没有被访问过则继续向下访问</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">visited</span><span class="o">[</span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">traversalChess</span><span class="p">(</span><span class="n">chessboard</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="p">,</span><span class="w"> </span><span class="n">step</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 当遍历完可走的位置集合后，如果发现该路不通，则进行回溯，否则标记为完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">step</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">y</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="o">!</span><span class="n">finished</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">chessboard</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">visited</span><span class="o">[</span><span class="n">row</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">finished</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将可走通路根据回溯次数进行从小到大排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sort</span><span class="p">(</span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="w"> </span><span class="n">points</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">points</span><span class="p">.</span><span class="na">sort</span><span class="p">((</span><span class="n">o1</span><span class="p">,</span><span class="w"> </span><span class="n">o2</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">next1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNext</span><span class="p">(</span><span class="n">o1</span><span class="p">).</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">next2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNext</span><span class="p">(</span><span class="n">o2</span><span class="p">).</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">next1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">next2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取下一个可走的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getNext</span><span class="p">(</span><span class="n">Point</span><span class="w"> </span><span class="n">current</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="w"> </span><span class="n">ps</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Point</span><span class="w"> </span><span class="n">p1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 表示马儿可以走5这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走6这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走7这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走0这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走1这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">y</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走2这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">y</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走3这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">y</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断马儿可以走4这个位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p1</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current</span><span class="p">.</span><span class="na">y</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">y</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ps</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Point</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ps</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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diff --git a/docs/posts/detailed/distributed-id/index.html b/docs/posts/detailed/distributed-id/index.html
new file mode 100644
index 00000000..e4312210
--- /dev/null
+++ b/docs/posts/detailed/distributed-id/index.html
@@ -0,0 +1,560 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>分布式ID详解 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="分布式ID 在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。 但随着数据日渐增长，主从同步也扛不住了，" />
+    
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+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/normalize.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8fid">
+                    分布式ID
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a9%e7%94%a8%e6%95%b0%e6%8d%ae%e5%ba%93%e8%87%aa%e5%a2%9eid">
+                    利用数据库自增id
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a9%e7%94%a8redis%e8%87%aa%e5%a2%9e">
+                    利用Redis自增
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a9%e7%94%a8uuid%e4%bd%9c%e4%b8%ba%e4%b8%bb%e9%94%ae">
+                    利用UUID作为主键
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a9%e7%94%a8%e7%b3%bb%e7%bb%9f%e5%bd%93%e5%89%8d%e6%97%b6%e9%97%b4">
+                    利用系统当前时间
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9b%aa%e8%8a%b1%e7%ae%97%e6%b3%95">
+                    雪花算法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
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+
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+
+
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+                        <h2 id="post_single_title">分布式ID详解</h2>
+                        <span id="post_page_title_date" class="date">2023.03.13</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="分布式id">分布式ID</h2>
+<p>在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。
+但随着数据日渐增长，主从同步也扛不住了，就需要对数据库进行分库分表。在分库之后， 数据遍布在不同服务器上的数据库，数据库的自增主键已经没办法满足生成的主键唯一了，这个时候就需要生成分布式 ID了。</p>
+<p>分布式ID一般都需要满足这些条件：</p>
+<ul>
+<li>全局唯一：必须保证ID是全局性唯一的，基本要求；</li>
+<li>高性能：高可用低延时，ID生成响应要块，否则反倒会成为业务瓶颈；</li>
+<li>高可用：100%的可用性是骗人的，但是也要无限接近于100%的可用性；</li>
+<li>趋势递增：如果要把 ID 存放在数据库的话，ID 的有序性可以提升数据库写入速度。并且，很多时候 ，我们还很有可能会直接通过 ID 来进行排序；</li>
+<li>安全：ID 中不包含敏感信息；</li>
+</ul>
+<p>常见分布式ID解决方案如下：</p>
+<h3 id="利用数据库自增id">利用数据库自增id</h3>
+<p>往一个库的一个表里插入一条没什么业务含义的数据，获取一个数据库自增的一个 id，拿到这个 id 之后再往对应的分库分表里去写入。缺点是高并发存在瓶颈；优点是简单方便；适用于并发不高，但是数据量太大导致的分库分表扩容，可能每秒最高并发最多就几百，那么就走单独的一个库和表生成自增主键即可。</p>
+<h3 id="利用redis自增">利用Redis自增</h3>
+<p>基于对数据库自增的改进，原理就是利用redis的incr命令实现ID的原子性自增。不依赖于数据库，灵活方便，且性能优于数据库，但是如果系统中没有Redis，还需要引入新的组件，会增加系统复杂度。</p>
+<h3 id="利用uuid作为主键">利用UUID作为主键</h3>
+<p>UUID一般不会作为主键使用，因为UUID 太长了、占用空间大，作为主键性能太差了，且UUID 不具有有序性，会导致 B+ 树索引在写的时候有过多的随机写操作，总之就是无序的性能开销大；适合于随机生成个什么文件名、编号之类的。</p>
+<h3 id="利用系统当前时间">利用系统当前时间</h3>
+<p>一般如果用这个方案，是将当前时间跟很多其他的业务字段拼接起来，作为一个 id，如果业务上你觉得可以接受，那么也是可以的。你可以将别的业务字段值跟当前时间拼接起来，组成一个全局唯一的编号。</p>
+<h3 id="雪花算法">雪花算法</h3>
+<p>算法思路是是把一个 64 位的 long 型的 id，1 个 bit 是不用的，用其中的 41 bits 作为毫秒数，用 10 bits 作为工作机器 id，12 bits 作为序列号。</p>
+<ul>
+<li>1 bit：不用，为啥呢？因为二进制里第一个 bit 为如果是 1，那么都是负数，但是我们生成的 id 都是正数，所以第一个 bit 统一都是 0；</li>
+<li>41 bits：表示的是时间戳，单位是毫秒。41 bits 可以表示的数字多达 2^41 - 1 ，也就是可以标识 2^41 - 1 个毫秒值，换算成年就是表示 69 年的时间；</li>
+<li>10 bits：记录工作机器 id，代表的是这个服务最多可以部署在 2^10 台机器上，也就是 1024 台机器。但是 10 bits 里 5 个 bits 代表机房 id，5 个 bits 代表机器 id。意思就是最多代表 2^5 个机房（32 个机房），每个机房里可以代表 2^5 个机器（32 台机器）；</li>
+<li>12 bits：这个是用来记录同一个毫秒内产生的不同 id，12 bits 可以代表的最大正整数是 2^12 - 1 = 4096 ，也就是说可以用这个 12 bits 代表的数字来区分同一个毫秒内的 4096 个不同的 id；</li>
+</ul>
+<p>雪花算法相对来说还是比较靠谱的，毫秒数在高位，自增序列在低位，整个ID都是趋势递增的。不依赖数据库等第三方系统，以服务的方式部署，稳定性更高，生成ID的性能也是非常高的，能达到百万计QPS。但是雪花算法强依赖时钟，如果机器上时钟回拨，会导致发号重复或者服务会处于不可用状态。</p>
+<p>为了规避雪花算法的缺点，一些国内的大厂做了改进，像美团的<a href="https://github.com/Meituan-Dianping/Leaf">Leaf</a>，百度的<a href="https://github.com/baidu/uid-generator">uid-generator</a>，都是基于雪花算法来实现的。</p>
+<p>所以你要真是搞分布式 id 生成，如果是高并发啥的，那么用这个应该性能比较好，一般每秒几万并发的场景，也足够用了。</p>
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+	<title>分布式锁详解 ｜ 脚踏实地</title>
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+    
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+    <meta name="description" content="概述 在代码里面我们常用ReetrantLock、synchronized保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。 类似这样： public" />
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%bf%b0">
+                    概述
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+                    基于Redis的分布式锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
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+        
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+                <a class="nav-link text-left" href="#redis%e5%88%86%e5%b8%83%e5%bc%8f%e9%94%81%e6%bc%94%e8%bf%9b">
+                    Redis分布式锁演进
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%b8%80">
+                    方式一
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+                    方式二
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%b8%89">
+                    方式三
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+                    方式四
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%ba%94">
+                    方式五
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+        
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+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e5%85%ad">
+                    方式六
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%b8%83">
+                    方式七
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+                    基于Zookeeper的分布式锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">分布式锁详解</h2>
+                        <span id="post_page_title_date" class="date">2024.05.25</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概述">概述</h2>
+<p>在代码里面我们常用<code>ReetrantLock、synchronized</code>保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。</p>
+<p>类似这样：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MainTest {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    private static final  ReentrantLock lock = new ReentrantLock();
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        lock.lock();
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            System.out.println(&#34;hello world&#34;);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            lock.unlock();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>但是，当项目采用分布式部署方式之后，再使用<code>ReetrantLock、synchronized</code>就不能保证数据的准确性，可能会出现严重bug。
+<img alt="Redis详解-010" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-010.png"></p>
+<p>举个例子，当很多个请求过来的时候，会先经过<code>Nginx</code>,然后<code>Nginx</code>再根据算法分发请求，到哪些服务器的程序上。
+此时商品的库存为一件，有两个请求，到达不同服务器上的不同程序的相同代码，先后执行了查询SQL，查出来的数据是相同的，然后依次执行库存减一操作，此时库存会变成-1件。这就造成了超卖问题。</p>
+<h2 id="基于redis的分布式锁">基于Redis的分布式锁</h2>
+<p>针对超卖问题，我们可以使用Redis分布式锁来解决。</p>
+<h3 id="redis分布式锁演进">Redis分布式锁演进</h3>
+<h4 id="方式一">方式一</h4>
+<p>使用Redis，<code>setnx</code>：</p>
+<blockquote>
+<p>SETNX 是SET IF NOT EXISTS的简写.日常命令格式是SETNX key value，如果 key不存在，则SETNX成功返回1，如果这个key已经存在了，则返回0。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value);
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>需要注意的是<code>redisTemplate.delete()</code>方法要加在<code>finally</code>中是为了程序出现异常不释放锁。</p>
+<p>但是这种写法会有一个问题，如果Redis服务器宕机了，或Redis服务被其他人kill掉了，此时恰好没有执行<code>finally</code>中的代码，就会造成Redis中永远都会存在这把锁，不会释放。</p>
+<h4 id="方式二">方式二</h4>
+<p>针对上面Redis宕机的问题，我们可以对这个key加一个过期时间，来解决：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {   
+</span></span><span class="line"><span class="cl">            // 加锁
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value);
+</span></span><span class="line"><span class="cl">            // 设置过期时间，假设为10s
+</span></span><span class="line"><span class="cl">            redisTemplate.expire(REDIS_LOCK,10, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>上面的代码虽然解决了Redis宕机的问题，但是也带来了一个新的问题：设置过期时间和加锁并不再一行，即是非原子操作。</p>
+<p>举个例子，如果执行完<code>setnx</code>加锁，正要执行<code>expire</code>设置过期时间时，进程要重启维护了，那么这个锁就“长生不老”了，别的线程永远获取不到锁了。</p>
+<h4 id="方式三">方式三</h4>
+<p>针对上面加锁和设置过期时间的问题，我们可以使用Redis提供的一个方法，使其具备原子性：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value, 10, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>加过期时间释放锁的这种方式会带来另一个问题，某个线程加锁，然后执行业务代码，业务代码执行的时间超过了限定时间，此时Redis会释放锁，然后第二个请求就进来了，此时第一个线程业务代码执行完毕，执行释放锁步骤。这就造成误删除其他线程的锁。</p>
+<p>简单说就是，张冠李戴，当前线程删除了其他线程的锁。</p>
+<h4 id="方式四">方式四</h4>
+<p>针对方式三带来的问题，需要加一个判断，来避免误删除其他线程的锁：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value, 10, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            // 判断是否是当前线程，如果是当前线程则允许释放锁
+</span></span><span class="line"><span class="cl">            if (redisTemplate.opsForvalue().get(REDIS_LOCK).equalsIgnoreCase(value)){
+</span></span><span class="line"><span class="cl">                redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>实际上这种方式判断和删除的操作不是原子的，不是原子性的就会出现问题。即该锁没有保存持有者的唯一标识，可能被别的客户端解锁。</p>
+<h4 id="方式五">方式五</h4>
+<p>针对方式四的问题，Redis官网有推荐的解决方法，即，使用<a href="http://www.redis.cn/commands/set">Lua脚本</a>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">if redis.call(&#39;setnx&#39;,KEYS[1],ARGV[1]) == 1 then
+</span></span><span class="line"><span class="cl">   redis.call(&#39;expire&#39;,KEYS[1],ARGV[2])
+</span></span><span class="line"><span class="cl">else
+</span></span><span class="line"><span class="cl">   return 0
+</span></span><span class="line"><span class="cl">end;
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            Boolean flag =  redisTemplate.opsForValue().setIfAbsent(REDIS_LOCK,value, 10, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (!flag) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;抢锁失败！&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            // 伪代码
+</span></span><span class="line"><span class="cl">            JRedis = jedis = JRedisUtils.getJRedis();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            String lua_scripts =
+</span></span><span class="line"><span class="cl">                    &#34;if redis.call(&#39;setnx&#39;,KEYS[1],ARGV[1]) == 1 then\n&#34; +
+</span></span><span class="line"><span class="cl">                    &#34;   redis.call(&#39;expire&#39;,KEYS[1],ARGV[2])\n&#34; +
+</span></span><span class="line"><span class="cl">                    &#34;else\n&#34; +
+</span></span><span class="line"><span class="cl">                    &#34;   return 0\n&#34; +
+</span></span><span class="line"><span class="cl">                    &#34;end;&#34;;
+</span></span><span class="line"><span class="cl">            Object result = jedis.eval(lua_scripts, Collections.singletonList(REDIS_LOCK), Collections.singletonList(value))
+</span></span><span class="line"><span class="cl">            if (result.equals(&#34;1&#34;)) {
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;删除key成功&#34;);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">                    
+</span></span><span class="line"><span class="cl">            if (jedis != null) {
+</span></span><span class="line"><span class="cl">                jedis.close();
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (redisTemplate.opsForvalue().get(REDIS_LOCK).equalsIgnoreCase(value)){
+</span></span><span class="line"><span class="cl">                redisTemplate.delete(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>除了用这中方式，也可以用Redis事务来处理方式四带来的问题。</p>
+<p>对于上面的解决方法，其实并没有真正的解决缓存续期的问题，还是会带来能存在锁过期释放，业务没执行完的问题。</p>
+<h4 id="方式六">方式六</h4>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.cnblogs.com/yunlongn/p/14609443.html">https://www.cnblogs.com/yunlongn/p/14609443.html</a></li>
+</ul>
+<p>针对缓存续期的问题，我们可以开一个守护线程，每隔一段时间检查锁是否还存在，存在则对锁的过期时间延长，防止锁过期提前释放。</p>
+<p><code>Redisson</code>框架解决了这个问题：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedissonClient redisson;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">        RLock lock = redisson.getLock(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            lock.lock(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            lock.unlock();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p><code>Redisson</code>大致工作原理：只要线程一加锁成功，就会启动一个<code>watch dog</code>看门狗，它是一个后台线程，会每隔10秒检查一下，如果线程一还持有锁，那么就会不断的延长锁key的生存时间。
+因此，<code>Redisson</code>解决了锁过期释放，业务没执行完问题。</p>
+<p><img alt="Redis详解-011" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-011.png"></p>
+<p>看似完美的解决方案，但是在高并发下可能也会出现下面的异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Caused by: java.lang.IllegalMonitorStateException: attempt to unlock lock, not locked by current thread by node id: 32caba49-5799-491b-aa7b-47d789dbca93 thread-id: 1
+</span></span></code></pre></div><p>异常出现的原因，加锁和解锁的线程不是同一个。</p>
+<h4 id="方式七">方式七</h4>
+<p>针对上面的异常，需要判断当前线程是否持有锁，如果还持有，则释放，如果未持有，则说明已被释放:</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedisTemplate redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Autowired
+</span></span><span class="line"><span class="cl">    private RedissonClient redisson;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    final String REDIS_LOCK = &#34;redis_lock_demo&#34;;
+</span></span><span class="line"><span class="cl">    // 保证value值唯一,这里是伪代码
+</span></span><span class="line"><span class="cl">    final String value = &#34;&#34;;
+</span></span><span class="line"><span class="cl">    public void context(){
+</span></span><span class="line"><span class="cl">         RLock lock = redisson.getLock(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            lock.lock(REDIS_LOCK);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            String redisKey =  redisTemplate.opsForvalue().get(&#34;redis_key&#34;);
+</span></span><span class="line"><span class="cl">            int num0 = redisKey == null ? 0 : Integer.parseInt(redisKey);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            if (num0 &lt;= 0){
+</span></span><span class="line"><span class="cl">                System.out.println(&#34;商品已售完！&#34;);
+</span></span><span class="line"><span class="cl">                return;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 卖出商品，存入Redis中
+</span></span><span class="line"><span class="cl">            int num1  = num0 - 1;
+</span></span><span class="line"><span class="cl">            redisTemplate.opsForvalue().set(&#34;redis_key&#34;,num1);
+</span></span><span class="line"><span class="cl">        }finally {
+</span></span><span class="line"><span class="cl">            // 查询当前线程是否持有此锁
+</span></span><span class="line"><span class="cl">            if (lock.isLocked() &amp;&amp; lock.isHeldByCurrentThread()) {
+</span></span><span class="line"><span class="cl">                lock.unlock();
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><p>这样写，程序的健壮性会更好，代码会更加严谨。</p>
+<h2 id="基于zookeeper的分布式锁">基于Zookeeper的分布式锁</h2>
+<p>Redis 实现分布式锁性能较高，ZooKeeper 实现分布式锁可靠性更高。实际项目中，我们应该根据业务的具体需求来选择。</p>
+<p>ZooKeeper 分布式锁是基于 临时顺序节点 和 Watcher（事件监听器） 实现的。</p>
+<p>获取锁：</p>
+<ol>
+<li>首先我们要有一个持久节点/locks，客户端获取锁就是在locks下创建临时顺序节点。</li>
+<li>假设客户端 1 创建了/locks/lock1节点，创建成功之后，会判断 lock1是否是 /locks 下最小的子节点。</li>
+<li>如果 lock1是最小的子节点，则获取锁成功。否则，获取锁失败。</li>
+<li>如果获取锁失败，则说明有其他的客户端已经成功获取锁。客户端 1 并不会不停地循环去尝试加锁，而是在前一个节点比如/locks/lock0上注册一个事件监听器。
+这个监听器的作用是当前一个节点释放锁之后通知客户端 1（避免无效自旋），这样客户端 1 就加锁成功了。</li>
+</ol>
+<p>释放锁：</p>
+<ol>
+<li>成功获取锁的客户端在执行完业务流程之后，会将对应的子节点删除。</li>
+<li>成功获取锁的客户端在出现故障之后，对应的子节点由于是临时顺序节点，也会被自动删除，避免了锁无法被释放。</li>
+<li>我们前面说的事件监听器其实监听的就是这个子节点删除事件，子节点删除就意味着锁被释放。</li>
+</ol>
+<p>实际项目中，推荐使用 Curator 来实现 ZooKeeper 分布式锁。
+Curator 是 Netflix 公司开源的一套 ZooKeeper Java 客户端框架，相比于 ZooKeeper 自带的客户端 zookeeper 来说，Curator 的封装更加完善，各种 API 都可以比较方便地使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">CuratorFramework</span><span class="w"> </span><span class="n">client</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ZKUtils</span><span class="p">.</span><span class="na">getClient</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">client</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 分布式可重入排它锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">InterProcessLock</span><span class="w"> </span><span class="n">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InterProcessMutex</span><span class="p">(</span><span class="n">client</span><span class="p">,</span><span class="w"> </span><span class="n">lockPath1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 分布式不可重入排它锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">InterProcessLock</span><span class="w"> </span><span class="n">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InterProcessSemaphoreMutex</span><span class="p">(</span><span class="n">client</span><span class="p">,</span><span class="w"> </span><span class="n">lockPath2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 将多个锁作为一个整体</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">InterProcessMultiLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InterProcessMultiLock</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">lock</span><span class="p">.</span><span class="na">acquire</span><span class="p">(</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">SECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalStateException</span><span class="p">(</span><span class="s">&#34;不能获取多锁&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;已获取多锁&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;是否有第一个锁: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">lock1</span><span class="p">.</span><span class="na">isAcquiredInThisProcess</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;是否有第二个锁: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">lock2</span><span class="p">.</span><span class="na">isAcquiredInThisProcess</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 资源操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">resource</span><span class="p">.</span><span class="na">use</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;释放多个锁&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">lock</span><span class="p">.</span><span class="na">release</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;是否有第一个锁: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">lock1</span><span class="p">.</span><span class="na">isAcquiredInThisProcess</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;是否有第二个锁: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">lock2</span><span class="p">.</span><span class="na">isAcquiredInThisProcess</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">client</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>如果对性能要求比较高的话，建议使用 Redis 实现分布式锁（优先选择 Redisson 提供的现成的分布式锁，而不是自己实现）。
+如果对可靠性要求比较高的话，建议使用 ZooKeeper 实现分布式锁（推荐基于 Curator 框架实现）。不过，现在很多项目都不会用到 ZooKeeper，如果单纯是因为分布式锁而引入 ZooKeeper 的话，那是不太可取的，不建议这样做，为了一个小小的功能增加了系统的复杂度。</p>
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diff --git a/docs/posts/detailed/elasticsearch/index.html b/docs/posts/detailed/elasticsearch/index.html
new file mode 100644
index 00000000..98f62c57
--- /dev/null
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+<html lang="zh" >
+<head>
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+
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+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
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+                    与ES交互
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%a8%e6%9f%a5%e8%af%a2">
+                    全查询
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+            </li>
+            
+            
+        </ul>
+        
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+        
+        </ul>
+        
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+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b4%e5%90%88springboot">
+                    整合SpringBoot
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#pom%e4%be%9d%e8%b5%96">
+                    pom依赖
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#applicationyml">
+                    application.yml
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#elasticsearchautoconfiguration">
+                    ElasticsearchAutoConfiguration
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#elasticsearchproperties">
+                    ElasticsearchProperties
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#elasticsearchconstant">
+                    ElasticsearchConstant
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#person">
+                    Person
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#searchpagehelper">
+                    SearchPageHelper
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#personservice">
+                    PersonService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+        
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+        
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#baseelasticsearchservice">
+                    BaseElasticsearchService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#personserviceimpl">
+                    PersonServiceImpl
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#elasticsearchapplicationtests">
+                    ElasticsearchApplicationTests
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
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+                    读数据流程
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8e%9f%e7%90%86">
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+                <a class="nav-link text-left" href="#%e5%80%92%e6%8e%92%e7%b4%a2%e5%bc%95">
+                    倒排索引
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+            
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+                <a class="nav-link text-left" href="#%e5%88%86%e6%9e%90%e5%99%a8">
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+                <a class="nav-link text-left" href="#%e6%96%87%e6%a1%a3%e6%90%9c%e7%b4%a2">
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+                <a class="nav-link text-left" href="#%e8%bf%91%e5%ae%9e%e6%97%b6%e6%90%9c%e7%b4%a2">
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+                <a class="nav-link text-left" href="#%e4%bc%98%e5%8c%96">
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+                <a class="nav-link text-left" href="#%e5%90%88%e7%90%86%e8%ae%be%e7%bd%ae%e5%88%86%e7%89%87%e6%95%b0">
+                    合理设置分片数
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+            
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+        
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+                <a class="nav-link text-left" href="#%e6%96%87%e4%bb%b6%e7%bc%93%e5%86%b2%e5%8c%bahttpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance">
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+        
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+        
+        
+        
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+            
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+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e6%8d%ae%e9%a2%84%e7%83%adhttpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance">
+                    数据预热
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+        
+        
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+            
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%b7%e7%83%ad%e5%88%86%e7%a6%bbhttpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance">
+                    冷热分离
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+                <a class="nav-link text-left" href="#document%e6%a8%a1%e5%9e%8b%e8%ae%be%e8%ae%a1httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance">
+                    document模型设计
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+            
+            
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+        
+        </ul>
+        
+        
+        
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+                        <svg t="1689246982401" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="6825" width="16" height="16"><path d="M270.76864 608.32h180.8a31.68 31.68 0 0 0 0-62.976H270.76864a31.68 31.68 0 0 0 0 62.976zM271.34464 458.56h457.92a33.472 33.472 0 0 0 31.552-34.752 33.28 33.28 0 0 0-31.552-34.624H271.34464a34.816 34.816 0 0 0 0 69.376zM271.34464 293.504h457.92a33.344 33.344 0 0 0 31.552-34.688 33.216 33.216 0 0 0-31.552-34.624H271.34464a33.28 33.28 0 0 0-31.616 34.624 33.28 33.28 0 0 0 31.616 34.688z" p-id="6826" fill="#424242"></path><path d="M869.87264 0H153.77664A70.4 70.4 0 0 0 84.65664 70.912V953.6A69.952 69.952 0 0 0 153.77664 1024h370.048a32 32 0 0 0 0-63.68H147.12064V64h729.6v468.672a31.296 31.296 0 1 0 62.528 0V70.912A70.4 70.4 0 0 0 869.87264 0z" p-id="6827" fill="#424242"></path><path d="M482.16064 730.624h337.664L715.82464 625.216a28.864 28.864 0 0 1-7.936-28.736 29.184 29.184 0 0 1 20.608-21.184 29.632 29.632 0 0 1 29.12 8.128l174.784 177.216-174.784 176.96a29.184 29.184 0 0 1-49.728-13.312 29.248 29.248 0 0 1 8-28.8l103.936-105.344H482.16064a29.696 29.696 0 0 1-29.504-29.76 29.632 29.632 0 0 1 29.504-29.76z" p-id="6828" fill="#424242"></path></svg>
+                    </a>
+                </span>
+                <a  id="icon_more" title="更多" >
+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
+                </a>
+                <a  id="icon_less" class="display_none">
+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Elasticsearch详解</h2>
+                        <span id="post_page_title_date" class="date">2023.02.14</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>Elasticsearch，简称为 ES， ES是一个开源的高扩展的分布式全文搜索引擎， 是整个 ElasticStack 技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可以扩展到上百台服务器，处理 PB 级别的数据。</p>
+<blockquote>
+<p>Elastic Stack, 包括 Elasticsearch、 Kibana、 Beats 和 Logstash（也称为 ELK Stack）。能够安全可靠地获取任何来源、任何格式的数据，然后实时地对数据进行搜索、分析和可视化。</p>
+</blockquote>
+<p>Elasticsearch 是面向文档型数据库，一条数据在这里就是一个文档。 Elasticsearch 里存储文档数据和关系型数据库 MySQL 存储数据的概念进行一个类比,如图:
+<img alt="Elasticsearch详解-01" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-01.png"></p>
+<p>ES 里的 Index 可以看做一个库，而 Types 相当于表， Documents 则相当于表的行。这里 Types 的概念已经被逐渐弱化， Elasticsearch 6.X 中，一个 index 下已经只能包含一个type， Elasticsearch 7.X 中, Type 的概念已经被删除了。</p>
+<p>官网下载地址: <a href="https://www.elastic.co/cn/downloads/past-releases">https://www.elastic.co/cn/downloads/past-releases</a></p>
+<h2 id="使用">使用</h2>
+<h3 id="与es交互">与ES交互</h3>
+<h4 id="索引创建">索引创建</h4>
+<p>发送put请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname
+</span></span></span></code></pre></div><h4 id="索引查询">索引查询</h4>
+<p>发送get请求,查询单条</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname
+</span></span></span></code></pre></div><p>查询所有索引,发送get请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_cat/indices
+</span></span></span></code></pre></div><h4 id="索引删除">索引删除</h4>
+<p>发送delete请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname
+</span></span></span></code></pre></div><h4 id="文档创建修改">文档创建修改</h4>
+<p>发送post请求,第一次为创建,再一次发送为修改</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_docname/idstr
+</span></span></span></code></pre></div><p>请求参数</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-json" data-lang="json"><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;title&#34;</span><span class="p">:</span><span class="s2">&#34;华为手机&#34;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;category&#34;</span><span class="p">:</span><span class="s2">&#34;小米&#34;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;images&#34;</span><span class="p">:</span><span class="s2">&#34;http://www.gulixueyuan.com/xm.jpg&#34;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;price&#34;</span><span class="p">:</span><span class="mf">3999.00</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h4 id="文档局部修改">文档局部修改</h4>
+<p>发送post请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_update/idstr
+</span></span></span></code></pre></div><p>请求参数</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-json" data-lang="json"><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;doc&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;title&#34;</span><span class="p">:</span><span class="s2">&#34;小米手机&#34;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;category&#34;</span><span class="p">:</span><span class="s2">&#34;小米&#34;</span>
+</span></span><span class="line"><span class="cl">  <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h4 id="文档查询">文档查询</h4>
+<p>发送get请求,查询单条</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_docname/idstr
+</span></span></span></code></pre></div><h4 id="文档删除">文档删除</h4>
+<p>发送delete请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_docname/idstr
+</span></span></span></code></pre></div><h4 id="全查询">全查询</h4>
+<p>发送get请求,能看到全部数据</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_search
+</span></span></span></code></pre></div><p>url带参查询,发get请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_search?q=category:小米
+</span></span></span></code></pre></div><p>请求体带参查询,发送get请求</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-http" data-lang="http"><span class="line"><span class="cl"><span class="err">http://127.0.0.1:9200/_indexname/_search
+</span></span></span></code></pre></div><p>查询category是华为和小米的,price大于2000,只显示title,显示第一页,每页显示两个,根据price降序</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-json" data-lang="json"><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;query&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;bool&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="nt">&#34;should&#34;</span><span class="p">:</span> <span class="p">[{</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&#34;match&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">          <span class="nt">&#34;category&#34;</span><span class="p">:</span> <span class="s2">&#34;小米&#34;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">      <span class="p">},</span>
+</span></span><span class="line"><span class="cl">        <span class="p">{</span>
+</span></span><span class="line"><span class="cl">          <span class="nt">&#34;match&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&#34;category&#34;</span><span class="p">:</span> <span class="s2">&#34;华为&#34;</span>
+</span></span><span class="line"><span class="cl">          <span class="p">}</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}]</span>
+</span></span><span class="line"><span class="cl">    <span class="p">},</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;filter&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="nt">&#34;range&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&#34;price&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">          <span class="nt">&#34;gt&#34;</span><span class="p">:</span> <span class="mi">2000</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">      <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">  <span class="p">},</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;_source&#34;</span><span class="p">:</span> <span class="p">[</span><span class="s2">&#34;title&#34;</span><span class="p">],</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;from&#34;</span><span class="p">:</span> <span class="mi">0</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;size&#34;</span><span class="p">:</span> <span class="mi">2</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">  <span class="nt">&#34;sort&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&#34;price&#34;</span><span class="p">:</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="nt">&#34;order&#34;</span><span class="p">:</span> <span class="s2">&#34;desc&#34;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">  <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h3 id="整合springboot">整合SpringBoot</h3>
+<h4 id="pom依赖">pom依赖</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-xml" data-lang="xml"><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.elasticsearch.client<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>elasticsearch-rest-high-level-client<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>7.5.2<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.elasticsearch.client<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>elasticsearch-rest-client<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>7.5.2<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.elasticsearch<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>elasticsearch<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>7.5.2<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;exclusions&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;exclusion&gt;</span>
+</span></span><span class="line"><span class="cl">                <span class="nt">&lt;groupId&gt;</span>org.elasticsearch.client<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">                <span class="nt">&lt;artifactId&gt;</span>elasticsearch-rest-client<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;/exclusion&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;exclusion&gt;</span>
+</span></span><span class="line"><span class="cl">                <span class="nt">&lt;groupId&gt;</span>org.elasticsearch<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">                <span class="nt">&lt;artifactId&gt;</span>elasticsearch<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;/exclusion&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/exclusions&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span></code></pre></div><h4 id="applicationyml">application.yml</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="nt">demo</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">data</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">elasticsearch</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="nt">cluster-name</span><span class="p">:</span><span class="w"> </span><span class="l">elasticsearch</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="nt">cluster-nodes</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="m">127.0.0.1</span><span class="p">:</span><span class="m">1001</span><span class="p">,</span><span class="m">127.0.0.1</span><span class="p">:</span><span class="m">1002</span><span class="p">,</span><span class="m">127.0.0.1</span><span class="p">:</span><span class="m">1003</span><span class="p">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="nt">index</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nt">number-of-replicas</span><span class="p">:</span><span class="w"> </span><span class="m">0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nt">number-of-shards</span><span class="p">:</span><span class="w"> </span><span class="m">3</span><span class="w">
+</span></span></span></code></pre></div><h4 id="elasticsearchautoconfiguration">ElasticsearchAutoConfiguration</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * ElasticsearchAutoConfiguration
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 22:59
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="p">(</span><span class="n">onConstructor_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nd">@Autowired</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@EnableConfigurationProperties</span><span class="p">(</span><span class="n">ElasticsearchProperties</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ElasticsearchAutoConfiguration</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ElasticsearchProperties</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">HttpHost</span><span class="o">&gt;</span><span class="w"> </span><span class="n">httpHosts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@ConditionalOnMissingBean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">RestHighLevelClient</span><span class="w"> </span><span class="nf">restHighLevelClient</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">clusterNodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getClusterNodes</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">clusterNodes</span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">parts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StringUtils</span><span class="p">.</span><span class="na">split</span><span class="p">(</span><span class="n">node</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Assert</span><span class="p">.</span><span class="na">notNull</span><span class="p">(</span><span class="n">parts</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Must defined&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Assert</span><span class="p">.</span><span class="na">state</span><span class="p">(</span><span class="n">parts</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Must be defined as &#39;host:port&#39;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">httpHosts</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HttpHost</span><span class="p">(</span><span class="n">parts</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">parseInt</span><span class="p">(</span><span class="n">parts</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="p">),</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getSchema</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalStateException</span><span class="p">(</span><span class="s">&#34;Invalid ES nodes &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;property &#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&#39;&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RestClientBuilder</span><span class="w"> </span><span class="n">builder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestClient</span><span class="p">.</span><span class="na">builder</span><span class="p">(</span><span class="n">httpHosts</span><span class="p">.</span><span class="na">toArray</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HttpHost</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">getRestHighLevelClient</span><span class="p">(</span><span class="n">builder</span><span class="p">,</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * get restHistLevelClient
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param builder                 RestClientBuilder
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param elasticsearchProperties elasticsearch default properties
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@link org.elasticsearch.client.RestHighLevelClient}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">RestHighLevelClient</span><span class="w"> </span><span class="nf">getRestHighLevelClient</span><span class="p">(</span><span class="n">RestClientBuilder</span><span class="w"> </span><span class="n">builder</span><span class="p">,</span><span class="w"> </span><span class="n">ElasticsearchProperties</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Callback used the default {@link RequestConfig} being set to the {@link CloseableHttpClient}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">setRequestConfigCallback</span><span class="p">(</span><span class="n">requestConfigBuilder</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">requestConfigBuilder</span><span class="p">.</span><span class="na">setConnectTimeout</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getConnectTimeout</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">requestConfigBuilder</span><span class="p">.</span><span class="na">setSocketTimeout</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getSocketTimeout</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">requestConfigBuilder</span><span class="p">.</span><span class="na">setConnectionRequestTimeout</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getConnectionRequestTimeout</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">requestConfigBuilder</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Callback used to customize the {@link CloseableHttpClient} instance used by a {@link RestClient} instance.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">setHttpClientConfigCallback</span><span class="p">(</span><span class="n">httpClientBuilder</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">httpClientBuilder</span><span class="p">.</span><span class="na">setMaxConnTotal</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getMaxConnectTotal</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">httpClientBuilder</span><span class="p">.</span><span class="na">setMaxConnPerRoute</span><span class="p">(</span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getMaxConnectPerRoute</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">httpClientBuilder</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Callback used the basic credential auth</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ElasticsearchProperties</span><span class="p">.</span><span class="na">Account</span><span class="w"> </span><span class="n">account</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getAccount</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">(</span><span class="n">account</span><span class="p">.</span><span class="na">getUsername</span><span class="p">())</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="o">!</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">(</span><span class="n">account</span><span class="p">.</span><span class="na">getUsername</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">final</span><span class="w"> </span><span class="n">CredentialsProvider</span><span class="w"> </span><span class="n">credentialsProvider</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BasicCredentialsProvider</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">credentialsProvider</span><span class="p">.</span><span class="na">setCredentials</span><span class="p">(</span><span class="n">AuthScope</span><span class="p">.</span><span class="na">ANY</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">UsernamePasswordCredentials</span><span class="p">(</span><span class="n">account</span><span class="p">.</span><span class="na">getUsername</span><span class="p">(),</span><span class="w"> </span><span class="n">account</span><span class="p">.</span><span class="na">getPassword</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RestHighLevelClient</span><span class="p">(</span><span class="n">builder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="elasticsearchproperties">ElasticsearchProperties</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * ElasticsearchProperties
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 22:58
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Builder</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@NoArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@ConfigurationProperties</span><span class="p">(</span><span class="n">prefix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;demo.data.elasticsearch&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ElasticsearchProperties</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 请求协议
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">schema</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;http&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 集群名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">clusterName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;elasticsearch&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 集群节点
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@NotNull</span><span class="p">(</span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;集群节点不允许为空&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">clusterNodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 连接超时时间(毫秒)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">connectTimeout</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * socket 超时时间
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">socketTimeout</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">30000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 连接请求超时时间
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">connectionRequestTimeout</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">500</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 每个路由的最大连接数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">maxConnectPerRoute</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 最大连接总数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">maxConnectTotal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">30</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 索引配置信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Index</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Index</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 认证账户
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Account</span><span class="w"> </span><span class="n">account</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Account</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 索引配置信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Index</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 分片数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">numberOfShards</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 副本数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">numberOfReplicas</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 认证账户
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Account</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 认证用户
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 认证密码
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">password</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="elasticsearchconstant">ElasticsearchConstant</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * ElasticsearchConstant
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 23:03
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">ElasticsearchConstant</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 索引名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">INDEX_NAME</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;person&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文档名称(字段名称)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_1&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_2&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_3&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_4&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">COLUMN_NAME_5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;column_5&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 高亮标签
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">TAG_HIGH_LIGHT_START</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;&lt;label style=&#39;color:red&#39;&gt;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">TAG_HIGH_LIGHT_END</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;&lt;/label&gt;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="person">Person</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Person
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 23:04
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Builder</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@NoArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Person</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">serialVersionUID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">8510634155374943623L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 主键
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 名字
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 国家
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">country</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 年龄
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 生日
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="n">birthday</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 介绍
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">remark</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="searchpagehelper">SearchPageHelper</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @author: whitepure
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @date: 2023/1/6 11:25
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @description: SearchPageHelper
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SearchPageHelper</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">current</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">pageSize</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">total</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">records</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="personservice">PersonService</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * PersonService
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 23:07
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PersonService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * create Index
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">createIndex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * delete Index
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteIndex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * insert document source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param list  data source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">insert</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * update document source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param list  data source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * delete document source
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param person delete data source and allow null object
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">delete</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="nd">@Nullable</span><span class="w"> </span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * search all doc records
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return person list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">searchList</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 分页查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param searchRequest search condition
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return search list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SearchPageHelper</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">searchPage</span><span class="p">(</span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="baseelasticsearchservice">BaseElasticsearchService</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * BaseElasticsearchService
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version 1.0v
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-16 15:44
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BaseElasticsearchService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Resource</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">RestHighLevelClient</span><span class="w"> </span><span class="n">client</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Resource</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ElasticsearchProperties</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">RequestOptions</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RequestOptions</span><span class="p">.</span><span class="na">Builder</span><span class="w"> </span><span class="n">builder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RequestOptions</span><span class="p">.</span><span class="na">DEFAULT</span><span class="p">.</span><span class="na">toBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 默认缓冲限制为100MB，此处修改为30MB。</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">setHttpAsyncResponseConsumerFactory</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HttpAsyncResponseConsumerFactory</span><span class="p">.</span><span class="na">HeapBufferedResponseConsumerFactory</span><span class="p">(</span><span class="n">30</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1024</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1024</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">COMMON_OPTIONS</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">builder</span><span class="p">.</span><span class="na">build</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * create elasticsearch index (asyc)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">createIndexRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">CreateIndexRequest</span><span class="w"> </span><span class="n">request</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CreateIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// Settings for this index</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">request</span><span class="p">.</span><span class="na">settings</span><span class="p">(</span><span class="n">Settings</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;index.number_of_shards&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getIndex</span><span class="p">().</span><span class="na">getNumberOfShards</span><span class="p">()).</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;index.number_of_replicas&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">elasticsearchProperties</span><span class="p">.</span><span class="na">getIndex</span><span class="p">().</span><span class="na">getNumberOfReplicas</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">CreateIndexResponse</span><span class="w"> </span><span class="n">createIndexResponse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">client</span><span class="p">.</span><span class="na">indices</span><span class="p">().</span><span class="na">create</span><span class="p">(</span><span class="n">request</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34; whether all of the nodes have acknowledged the request : {}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">createIndexResponse</span><span class="p">.</span><span class="na">isAcknowledged</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34; Indicates whether the requisite number of shard copies were started for each shard in the index before timing out :{}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">createIndexResponse</span><span class="p">.</span><span class="na">isShardsAcknowledged</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;创建索引 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 失败&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * delete elasticsearch index
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteIndexRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DeleteIndexRequest</span><span class="w"> </span><span class="n">deleteIndexRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildDeleteIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">client</span><span class="p">.</span><span class="na">indices</span><span class="p">().</span><span class="na">delete</span><span class="p">(</span><span class="n">deleteIndexRequest</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;删除索引 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 失败&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * build DeleteIndexRequest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">DeleteIndexRequest</span><span class="w"> </span><span class="nf">buildDeleteIndexRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DeleteIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * build IndexRequest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index  elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param id     request object id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param object request object
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@link org.elasticsearch.action.index.IndexRequest}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">IndexRequest</span><span class="w"> </span><span class="nf">buildIndexRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">object</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">id</span><span class="p">).</span><span class="na">source</span><span class="p">(</span><span class="n">BeanUtil</span><span class="p">.</span><span class="na">beanToMap</span><span class="p">(</span><span class="n">object</span><span class="p">),</span><span class="w"> </span><span class="n">XContentType</span><span class="p">.</span><span class="na">JSON</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * exec updateRequest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index  elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param id     Document id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param object request object
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">updateRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">object</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">UpdateRequest</span><span class="w"> </span><span class="n">updateRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">UpdateRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">id</span><span class="p">).</span><span class="na">doc</span><span class="p">(</span><span class="n">BeanUtil</span><span class="p">.</span><span class="na">beanToMap</span><span class="p">(</span><span class="n">object</span><span class="p">),</span><span class="w"> </span><span class="n">XContentType</span><span class="p">.</span><span class="na">JSON</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">client</span><span class="p">.</span><span class="na">update</span><span class="p">(</span><span class="n">updateRequest</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;更新索引 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 数据 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">object</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 失败&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * exec deleteRequest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param index elasticsearch index name
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param id    Document id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @author fxbin
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteRequest</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">DeleteRequest</span><span class="w"> </span><span class="n">deleteRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DeleteRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">client</span><span class="p">.</span><span class="na">delete</span><span class="p">(</span><span class="n">deleteRequest</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;删除索引 {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 数据id {&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;} 失败&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 查询全部
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param indices elasticsearch 索引名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@link SearchResponse}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">SearchResponse</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="n">String</span><span class="p">...</span><span class="w"> </span><span class="n">indices</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SearchRequest</span><span class="p">(</span><span class="n">indices</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchSourceBuilder</span><span class="w"> </span><span class="n">searchSourceBuilder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SearchSourceBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">searchSourceBuilder</span><span class="p">.</span><span class="na">query</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">matchAllQuery</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">searchRequest</span><span class="p">.</span><span class="na">source</span><span class="p">(</span><span class="n">searchSourceBuilder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 查询全部
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param searchRequest 查询条件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@link SearchResponse}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">SearchResponse</span><span class="w"> </span><span class="nf">search</span><span class="p">(</span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchResponse</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">searchResponse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">client</span><span class="p">.</span><span class="na">search</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">org</span><span class="p">.</span><span class="na">elasticsearch</span><span class="p">.</span><span class="na">ElasticsearchException</span><span class="p">(</span><span class="s">&#34;查询索引 %s 失败&#34;</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">,</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">stream</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">.</span><span class="na">indices</span><span class="p">()).</span><span class="na">toArray</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="personserviceimpl">PersonServiceImpl</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * PersonServiceImpl
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @version v1.0
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @since 2019-09-15 23:08
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PersonServiceImpl</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">BaseElasticsearchService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PersonService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">createIndex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">createIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteIndex</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">deleteIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">insert</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">IndexRequest</span><span class="w"> </span><span class="n">request</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildIndexRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">person</span><span class="p">.</span><span class="na">getId</span><span class="p">()),</span><span class="w"> </span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">client</span><span class="p">.</span><span class="na">index</span><span class="p">(</span><span class="n">request</span><span class="p">,</span><span class="w"> </span><span class="n">COMMON_OPTIONS</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">person</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">updateRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">person</span><span class="p">.</span><span class="na">getId</span><span class="p">()),</span><span class="w"> </span><span class="n">person</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">delete</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ObjectUtils</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">(</span><span class="n">person</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果person 对象为空，则删除全量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">searchList</span><span class="p">(</span><span class="n">index</span><span class="p">).</span><span class="na">forEach</span><span class="p">(</span><span class="n">p</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">deleteRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">p</span><span class="p">.</span><span class="na">getId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">deleteRequest</span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">person</span><span class="p">.</span><span class="na">getId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">searchList</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">toSearchList</span><span class="p">(</span><span class="n">search</span><span class="p">(</span><span class="n">index</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">SearchPageHelper</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">searchPage</span><span class="p">(</span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchResponse</span><span class="w"> </span><span class="n">searchResponse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">search</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TotalHits</span><span class="w"> </span><span class="n">totalHits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">.</span><span class="na">getHits</span><span class="p">().</span><span class="na">getTotalHits</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SearchPageHelper</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setTotal</span><span class="p">(</span><span class="n">totalHits</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">totalHits</span><span class="p">.</span><span class="na">value</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setRecords</span><span class="p">(</span><span class="n">toSearchList</span><span class="p">(</span><span class="n">searchResponse</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setPageSize</span><span class="p">(</span><span class="n">20L</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">toSearchList</span><span class="p">(</span><span class="n">SearchResponse</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchHit</span><span class="o">[]</span><span class="w"> </span><span class="n">hits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">searchResponse</span><span class="p">.</span><span class="na">getHits</span><span class="p">().</span><span class="na">getHits</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">searchList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Arrays</span><span class="p">.</span><span class="na">stream</span><span class="p">(</span><span class="n">hits</span><span class="p">).</span><span class="na">forEach</span><span class="p">(</span><span class="n">hit</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="o">&gt;</span><span class="w"> </span><span class="n">sourceAsMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hit</span><span class="p">.</span><span class="na">getSourceAsMap</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 处理高亮数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">HighlightField</span><span class="o">&gt;</span><span class="w"> </span><span class="n">highlightFields</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hit</span><span class="p">.</span><span class="na">getHighlightFields</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">highlightFields</span><span class="p">.</span><span class="na">forEach</span><span class="p">((</span><span class="n">k</span><span class="p">,</span><span class="w"> </span><span class="n">v</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">v</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">v</span><span class="p">.</span><span class="na">getFragments</span><span class="p">().</span><span class="na">length</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">sourceAsMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">k</span><span class="p">,</span><span class="w"> </span><span class="n">StrUtil</span><span class="p">.</span><span class="na">strip</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">v</span><span class="p">.</span><span class="na">getFragments</span><span class="p">()),</span><span class="w"> </span><span class="s">&#34;[]&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Person</span><span class="w"> </span><span class="n">search</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeanUtil</span><span class="p">.</span><span class="na">mapToBean</span><span class="p">(</span><span class="n">sourceAsMap</span><span class="p">,</span><span class="w"> </span><span class="n">Person</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">searchList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">search</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">searchList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="elasticsearchapplicationtests">ElasticsearchApplicationTests</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@RunWith</span><span class="p">(</span><span class="n">SpringRunner</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@SpringBootTest</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ElasticsearchApplicationTests</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PersonService</span><span class="w"> </span><span class="n">personService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试删除索引
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteIndexTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">deleteIndex</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试创建索引
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">createIndexTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">createIndex</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试新增
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">insertTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">age</span><span class="p">(</span><span class="n">11</span><span class="p">).</span><span class="na">birthday</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">()).</span><span class="na">country</span><span class="p">(</span><span class="s">&#34;CN&#34;</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">1L</span><span class="p">).</span><span class="na">name</span><span class="p">(</span><span class="s">&#34;哈哈&#34;</span><span class="p">).</span><span class="na">remark</span><span class="p">(</span><span class="s">&#34;test1&#34;</span><span class="p">).</span><span class="na">build</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">age</span><span class="p">(</span><span class="n">22</span><span class="p">).</span><span class="na">birthday</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">()).</span><span class="na">country</span><span class="p">(</span><span class="s">&#34;US&#34;</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">2L</span><span class="p">).</span><span class="na">name</span><span class="p">(</span><span class="s">&#34;hiahia&#34;</span><span class="p">).</span><span class="na">remark</span><span class="p">(</span><span class="s">&#34;test2&#34;</span><span class="p">).</span><span class="na">build</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">age</span><span class="p">(</span><span class="n">33</span><span class="p">).</span><span class="na">birthday</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">()).</span><span class="na">country</span><span class="p">(</span><span class="s">&#34;ID&#34;</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">3L</span><span class="p">).</span><span class="na">name</span><span class="p">(</span><span class="s">&#34;呵呵&#34;</span><span class="p">).</span><span class="na">remark</span><span class="p">(</span><span class="s">&#34;test3&#34;</span><span class="p">).</span><span class="na">build</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">insert</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试更新
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">updateTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">age</span><span class="p">(</span><span class="n">33</span><span class="p">).</span><span class="na">birthday</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">()).</span><span class="na">country</span><span class="p">(</span><span class="s">&#34;ID_update&#34;</span><span class="p">).</span><span class="na">id</span><span class="p">(</span><span class="n">3L</span><span class="p">).</span><span class="na">name</span><span class="p">(</span><span class="s">&#34;呵呵update&#34;</span><span class="p">).</span><span class="na">remark</span><span class="p">(</span><span class="s">&#34;test3_update&#34;</span><span class="p">).</span><span class="na">build</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">update</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试删除
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deleteTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">personService</span><span class="p">.</span><span class="na">delete</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">Person</span><span class="p">.</span><span class="na">builder</span><span class="p">().</span><span class="na">id</span><span class="p">(</span><span class="n">1L</span><span class="p">).</span><span class="na">build</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">searchListTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">personList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">personService</span><span class="p">.</span><span class="na">searchList</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">personList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 测试分页查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">searchPageTest</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">pageSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">maxCurrent</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">500</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 此处最大页数设置为500 为es浅分页; 如需深度分页需更换分页方法并移除此条件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">current</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">maxCurrent</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 构造查询条件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchRequest</span><span class="w"> </span><span class="n">searchRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SearchRequest</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">INDEX_NAME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">searchRequest</span><span class="p">.</span><span class="na">source</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">SearchSourceBuilder</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">trackTotalHits</span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 查询条件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">query</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">boolQuery</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// and</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">.</span><span class="na">must</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">termQuery</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_2</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// or</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">.</span><span class="na">must</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">boolQuery</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">.</span><span class="na">should</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">matchQuery</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">.</span><span class="na">should</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">matchQuery</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">.</span><span class="na">should</span><span class="p">(</span><span class="n">QueryBuilders</span><span class="p">.</span><span class="na">matchQuery</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 分页</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">from</span><span class="p">((</span><span class="n">current</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">pageSize</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">size</span><span class="p">(</span><span class="n">pageSize</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 相关度排序: SortBuilders.scoreSort()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">sort</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 字段排序 可根据时间</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">SortBuilders</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">.</span><span class="na">fieldSort</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_2</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">.</span><span class="na">order</span><span class="p">(</span><span class="n">SortOrder</span><span class="p">.</span><span class="na">DESC</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 高亮字段</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">highlighter</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">HighlightBuilder</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">requireFieldMatch</span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">preTags</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">TAG_HIGH_LIGHT_START</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">field</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_1</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">field</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_2</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">field</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">COLUMN_NAME_3</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">postTags</span><span class="p">(</span><span class="n">ElasticsearchConstant</span><span class="p">.</span><span class="na">TAG_HIGH_LIGHT_END</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SearchPageHelper</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">personSearchPageHelper</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">personService</span><span class="p">.</span><span class="na">searchPage</span><span class="p">(</span><span class="n">searchRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">personSearchPageHelper</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="集群架构">集群架构</h2>
+<p>一个运行中的 Elasticsearch 实例称为一个节点，而集群是由一个或者多个拥有相同 cluster.name 配置的节点组成， 它们共同承担数据和负载的压力。 当有节点加入集群中或者从集群中移除节点时，集群将会重新平均分布所有的数据。</p>
+<p>当一个节点被选举成为主节点时， 它将负责管理集群范围内的所有变更，例如增加、 删除索引，或者增加、删除节点等。 而主节点并不需要涉及到文档级别的变更和搜索等操作，所以当集群只拥有一个主节点的情况下，即使流量的增加它也不会成为瓶颈。 任何节点都可以成为主节点。我们的示例集群就只有一个节点，所以它同时也成为了主节点。</p>
+<p>作为用户，我们可以将请求发送到集群中的任何节点 ，包括主节点。 每个节点都知道任意文档所处的位置，并且能够将我们的请求直接转发到存储我们所需文档的节点。 无论我们将请求发送到哪个节点，它都能负责从各个包含我们所需文档的节点收集回数据，并将最终结果返回给客户端。</p>
+<h3 id="搭建集群">搭建集群</h3>
+<ol>
+<li>
+<p>创建 elasticsearch-cluster 文件夹，在内部复制三个 elasticsearch 服务。
+<img alt="Elasticsearch详解-02" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-02.png"></p>
+</li>
+<li>
+<p>修改节点配置; config/elasticsearch.yml 文件</p>
+<ul>
+<li>node-1001 节点
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="c">#集群名称，节点之间要保持一致</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">cluster.name</span><span class="p">:</span><span class="w"> </span><span class="l">my-elasticsearch</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#节点名称，集群内要唯一</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.name</span><span class="p">:</span><span class="w"> </span><span class="l">node-1001</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.master</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.data</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#ip 地址</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">network.host</span><span class="p">:</span><span class="w"> </span><span class="l">localhost</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#http 端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.port</span><span class="p">:</span><span class="w"> </span><span class="m">1001</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#tcp 监听端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">transport.tcp.port</span><span class="p">:</span><span class="w"> </span><span class="m">9301</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#discovery.seed_hosts: [&#34;localhost:9301&#34;, &#34;localhost:9302&#34;,&#34;localhost:9303&#34;]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#discovery.zen.fd.ping_timeout: 1m</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#discovery.zen.fd.ping_retries: 5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#集群内的可以被选为主节点的节点列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#cluster.initial_master_nodes: [&#34;node-1&#34;, &#34;node-2&#34;,&#34;node-3&#34;]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#跨域配置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#action.destructive_requires_name: true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.cors.enabled</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.cors.allow-origin</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;*&#34;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>node-1002 节点
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="w"> </span><span class="c">#集群名称，节点之间要保持一致</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">cluster.name</span><span class="p">:</span><span class="w"> </span><span class="l">my-elasticsearch</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#节点名称，集群内要唯一</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">node.name</span><span class="p">:</span><span class="w"> </span><span class="l">node-1002</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">node.master</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">node.data</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#ip 地址</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">network.host</span><span class="p">:</span><span class="w"> </span><span class="l">localhost</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#http 端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">http.port</span><span class="p">:</span><span class="w"> </span><span class="m">1002</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#tcp 监听端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">transport.tcp.port</span><span class="p">:</span><span class="w"> </span><span class="m">9302</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">discovery.seed_hosts</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="s2">&#34;localhost:9301&#34;</span><span class="p">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">discovery.zen.fd.ping_timeout</span><span class="p">:</span><span class="w"> </span><span class="l">1m</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">discovery.zen.fd.ping_retries</span><span class="p">:</span><span class="w"> </span><span class="m">5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#集群内的可以被选为主节点的节点列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#cluster.initial_master_nodes: [&#34;node-1&#34;, &#34;node-2&#34;,&#34;node-3&#34;]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#跨域配置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c">#action.destructive_requires_name: true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">http.cors.enabled</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nt">http.cors.allow-origin</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;*&#34;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>node-1003 节点
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="c">#集群名称，节点之间要保持一致</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">cluster.name</span><span class="p">:</span><span class="w"> </span><span class="l">my-elasticsearch</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#节点名称，集群内要唯一</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.name</span><span class="p">:</span><span class="w"> </span><span class="l">node-1003</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.master</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">node.data</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#ip 地址</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">network.host</span><span class="p">:</span><span class="w"> </span><span class="l">localhost</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#http 端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.port</span><span class="p">:</span><span class="w"> </span><span class="m">1003</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#tcp 监听端口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">transport.tcp.port</span><span class="p">:</span><span class="w"> </span><span class="m">9303</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#候选主节点的地址，在开启服务后可以被选为主节点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">discovery.seed_hosts</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="s2">&#34;localhost:9301&#34;</span><span class="p">,</span><span class="w"> </span><span class="s2">&#34;localhost:9302&#34;</span><span class="p">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">discovery.zen.fd.ping_timeout</span><span class="p">:</span><span class="w"> </span><span class="l">1m</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">discovery.zen.fd.ping_retries</span><span class="p">:</span><span class="w"> </span><span class="m">5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#集群内的可以被选为主节点的节点列表</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#cluster.initial_master_nodes: [&#34;node-1&#34;, &#34;node-2&#34;,&#34;node-3&#34;]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#跨域配置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c">#action.destructive_requires_name: true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.cors.enabled</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">http.cors.allow-origin</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;*&#34;</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+</li>
+<li>
+<p>启动集群; 点击 bin\elasticsearch.bat
+<img alt="Elasticsearch详解-03" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-03.png"></p>
+</li>
+</ol>
+<p>如果启动不起来可能原因是分配内存不足，需要修改 config\jvm.options 文件中的内存属性</p>
+<p>启动之后使用ES可视化工具查看,可使用<a href="https://github.com/mobz/elasticsearch-head">elasticsearch-head</a>,<a href="https://gitee.com/farmerx/ElasticHD">ElasticHD</a></p>
+<h3 id="分布式架构原理">分布式架构原理</h3>
+<p>ElasticSearch 设计的理念就是分布式搜索引擎，底层其实还是基于 lucene 的。核心思想就是在多台机器上启动多个 ES 进程实例，组成了一个 ES 集群。</p>
+<p>ES分布式架构实际上就是对index的拆分,将index拆分成多个分片(shard),将分片分别放到不同的ES上实现集群部署.</p>
+<p><img alt="Elasticsearch详解-05" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-05.png"></p>
+<p>分片优点:</p>
+<ul>
+<li>支持横向扩展: 比如你数据量是 3T，3 个 shard，每个 shard 就 1T 的数据，若现在数据量增加到 4T,怎么扩展，很简单，重新建一个有 4 个 shard 的索引，将数据导进去;</li>
+<li>提高性能: 数据分布在多个 shard，即多台服务器上，所有的操作，都会在多台机器上并行分布式执行，提高了吞吐量和性能;</li>
+</ul>
+<p>分片的数据实际上是有多个备份存在的,会存在一个主分片,还有几个副本分片. 当写入数据的时候先写入主分片,然后并行将数据同步到副本分片上;当读数据的时候会获取到所有分片,负载均衡轮询读取.</p>
+<p>当某个节点宕机了,还有其他分片副本保存在其他的机器上,从而实现了高可用. 如果是非主节点宕机了，那么会由主节点，让那个宕机节点上的主分片的数据转移到其他机器上的副本数据。接着你要是修复了那个宕机机器，重启了之后，主节点会控制将缺失的副本数据分配过去，同步后续修改的数据之类的，让集群恢复正常. 如果是主节点宕机,那么会重新选举一个节点为主节点.</p>
+<h3 id="故障转移">故障转移</h3>
+<p>在一个网络环境里，失败随时都可能发生，在某个分片/节点不知怎么的就处于离线状态，或者由于任何原因消失了，这种情况下，有一个故障转移机制是非常有用并且是强烈推荐的。为此目的，Elasticsearch 允许你创建分片的一份或多份拷贝，这些拷贝叫做复制分片。</p>
+<p>当集群中只有一个节点在运行时，意味着会有一个单点故障问题——没有冗余。 幸运的是，我们只需再启动一个节点即可防止数据丢失。当你在同一台机器上启动了第二个节点时，只要它和第一个节点有同样的 cluster.name 配置，它就会自动发现集群并加入到其中。</p>
+<p>ES最好部署3个以上的节点，并且配置仲裁数大于一半节点，防止master选举的脑裂问题。</p>
+<ul>
+<li>当一个节点掉线，如果该节点是master节点，则通过比较node ID，选择较小ID的节点为master；</li>
+<li>然后由master节点决定分片如何重新分配。同理，新加入节点也是由master决定如何分配分片；</li>
+</ul>
+<blockquote>
+<p>关于master的选举:
+主要是由ZenDiscovery模块负责,包含Ping(节点之间通过这个RPC来发现彼此)和Unicast（单播模块包含-一个主机列表以控制哪些节点需要ping通）这两部分.
+首先对所有可以成为master的节点(可以配置)根据nodeId排序,每次选举每个节点都把自己所知道节点排一次序,然后选出第一个,暂且认为它是master节点
+如果对某个节点的投票数达到一定的值（可以成为master节点数n/2+1）并且该节点自己也选举自己,那这个节点就是master。否则重新选举一直到满足上述条件</p>
+</blockquote>
+<blockquote>
+<p>ES在主节点上产生分歧，产生多个主节点，从而使集群分裂，使得集群处于异常状态。这个现象叫做脑裂。脑裂问题其实就是同一个集群的不同节点对于整个集群的状态有不同的理解，导致操作错乱，类似于精神分裂。</p>
+</blockquote>
+<h3 id="分片控制">分片控制</h3>
+<p>当写入一个文档的时候，文档会被存储到一个主分片中。 Elasticsearch 集群如何知道一个文档应该存放到哪个分片中呢？</p>
+<p>Elasticsearch 集群路由计算公式:</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">shard = hash(routing) % number_of_primary_shards
+</span></span></code></pre></div><p>routing 是一个可变值，默认是文档的 _id ，也可以设置成一个自定义的值。 routing 通过hash 函数生成一个数字，然后这个数字再除以 number_of_primary_shards （主分片的数量）后得到余数 。这个分布在 0 到 number_of_primary_shards-1 之间的余数，就是我们所寻求的文档所在分片的位置。</p>
+<p>这也就是创建索引的时候主分片的数量永远也不会改变的原因,如果数量变化了,那么所有之前路由的值都会无效,文档也再也找不到了.</p>
+<p>用户可以访问任何一个节点获取数据,因为存放的规则一致(副本和主分片存放的数据一致),这个节点称之为协调节点.如果当前节点访问量较大可能被转到其他节点上,所以当发送请求的时候,为了扩展负载,更好的做法是轮询集群中所有的节点.</p>
+<h3 id="写数据流程">写数据流程</h3>
+<p><img alt="Elasticsearch详解-06" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-06.png"></p>
+<ol>
+<li>客户端请请求任意集群节点(协调节点);</li>
+<li>协调节点将请求转换到指定节点(路由计算);</li>
+<li>主分片需要将数据保存;</li>
+<li>主分片将保存数据的请求发送到各个副本;</li>
+<li>各个副本保存后,进行响应;</li>
+<li>主分片进行响应;</li>
+<li>客户端获取响应;</li>
+</ol>
+<p>在客户端收到成功响应时，文档变更已经在主分片和所有副本分片执行完成，变更是安全的。有一些可选的请求参数允许您影响这个过程，可能以数据安全为代价提升性能。</p>
+<p>设置 consistency 参数值会影响写入操作.consistency 参数的值可以设为:</p>
+<ul>
+<li>one ：只要主分片状态 ok 就允许执行写操作;</li>
+<li>all：必须要主分片和所有副本分片的状态没问题才允许执行写操作;</li>
+<li>quorum：默认值为quorum , 即大多数的分片副本状态没问题就允许执行写操作;</li>
+</ul>
+<p>当consistency值设置为quorum时,如果没有足够的副本分片Elasticsearch 会等待.默认情况下,它最多等待 1 分钟,可以使用timeout参数使它更早终止.</p>
+<h3 id="读数据流程">读数据流程</h3>
+<ol>
+<li>客户端发送查询请求到协调节点;</li>
+<li>协调节点计算数据所在的分片及全部的副本位置,为了能负载均衡要轮询所有的分片;</li>
+<li>将请求转发给具体的节点;</li>
+<li>节点返回查询结果,将结果返回给客户端;</li>
+</ol>
+<p>在处理读取请求时，协调结点在每次请求的时候都会通过轮询所有的副本分片来达到负载均衡。在文档被检索时，已经保存的数据可能已经存在于主分片上但是还没有复制到副本分片。 在这种情况下，副本分片可能会报告文档不存在，但是主分片可能成功返回文档。 一旦索引请求成功返回给用户，文档在主分片和副本分片都是可用的。</p>
+<h3 id="搜索数据过程">搜索数据过程</h3>
+<ol>
+<li>客户端发送请求到一个协调节点;</li>
+<li>协调节点计算数据所在的分片及全部的副本位置;</li>
+<li>每个分片将自己的搜索结果（其实就是一些 doc id ）返回给协调节点，由协调节点进行数据的合并、排序、分页等操作，产出最终结果;</li>
+<li>接着由协调节点根据 doc id 去各个节点上拉取实际的 document 数据，最终返回给客户端;</li>
+</ol>
+<h3 id="更新流程">更新流程</h3>
+<ol>
+<li>客户端向某一节点发送更新请求;</li>
+<li>将请求转发到主分片所在的节点;</li>
+<li>从主分片检索文档，修改_source字段中的JSON，并且尝试重新索引主分片的文档。如果文档已经被另一个进程修改,它会重试步骤3 ,超过retry_on_conflict次后放弃;</li>
+<li>如果主节点成功地更新文档，它将新版本的文档并行转发到副本分片，重新建立索引。一旦所有副本分片都返回成功，主节点向协调节点也返回成功，协调节点向客户端返回成功;</li>
+</ol>
+<p>在步骤4中,主分片把更改转发到副本分片时， 它不会转发更新请求。 相反，它转发完整文档的新版本。请记住，这些更改将会异步转发到副本分片，并且不能保证它们以发送它们相同的顺序到达。 如果 Elasticsearch 仅转发更改请求，则可能以错误的顺序应用更改，导致得到损坏的文档。</p>
+<h2 id="原理">原理</h2>
+<p>分片是Elasticsearch最小的工作单元。传统的数据库每个字段存储单个值，但这对全文检索并不够。文本字段中的每个单词需要被搜索，对数据库意味着需要单个字段有索引多值的能力。最好的支持是一个字段多个值需求的数据结构是倒排索引。</p>
+<h3 id="倒排索引">倒排索引</h3>
+<p>Elasticsearch 使用一种称为 倒排索引 的结构，它适用于快速的全文搜索。一个倒排索引由文档中所有不重复词的列表构成，对于其中每个词，有一个包含它的文档列表。 倒排索引（Inverted Index）也叫反向索引，有反向索引必有正向索引。通俗地来讲，正向索引是通过key找value，反向索引则是通过value找key。</p>
+<p>倒排索引示例:</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">| value    | key               |  
+</span></span><span class="line"><span class="cl">|----------|-------------------|   
+</span></span><span class="line"><span class="cl">| my name is zhangsan   | 1001 |  
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">| key     | value|
+</span></span><span class="line"><span class="cl">|---------|------|
+</span></span><span class="line"><span class="cl">| name    | 1001 |
+</span></span><span class="line"><span class="cl">| zhang   | 1001 |
+</span></span><span class="line"><span class="cl">| zhangsan| 1001 |
+</span></span></code></pre></div><p>倒排索引搜索过程: 查询单词是否在词典中,如果不在搜索结束,如果在词典中需要查询单词在倒排列表中的指针,获取单词对应的文档ID,根据文档ID查询时哪一条数据</p>
+<p>词条: 索引中最小的存储和查询单元
+词典: 词条的集合;一般用hash表或B+tree存储
+倒排表: 记录了出现过某个单词的所有文档的文档列表及单词在该文档中出现的位置信息,每条记录称为一个倒排项.根据倒排列表,即可获知哪些文档包含某个单词.</p>
+<h3 id="分析器">分析器</h3>
+<p>倒排索引总是和分词分不开的,中文分词和英文分词是不一样的,所以就需要分析器.</p>
+<p>分析器的主要功能是将一块文本分成适合于倒排索引的独立词条,分析器组成:</p>
+<ul>
+<li>字符过滤器: 在分词前整理字符串,一个字符过滤器可以用来去掉 HTML,或者将 &amp; 转化成 and;</li>
+<li>分词器: 字符串被分词器分为单个的词条,一个简单的分词器遇到空格和标点的时候,可能会将文本拆分成词条;</li>
+<li>词单元过滤器: 按顺序通过每个过滤器,这个过程可能会改变词条（例如，小写化Quick ），删除词条（例如， 像 a， and， the 等无用词），或者增加词条（例如，像jump和leap这种同义词）;</li>
+</ul>
+<p>Elasticsearch附带了可以直接使用的预包装的分析器:</p>
+<ul>
+<li>标准分析器: 默认使用的分析器。它是分析各种语言文本最常用的选择。它根据Unicode 联盟定义的单词边界划分文本。删除绝大部分标点;</li>
+<li>简单分析器: 在任何不是字母的地方分隔文本，将词条小写;</li>
+<li>空格分析器: 在空格的地方划分文本;</li>
+<li>语言分析器: 考虑指定语言的特点,根据语法进行分词; 例如，英语分析器附带了一组英语无用词（常用单词，例如and或者the ,它们对相关性没有多少影响），它们会被删除;</li>
+</ul>
+<p>常用中文分词器: <a href="https://github.com/medcl/elasticsearch-analysis-ik/releases/tag/v7.8.0">ik分词器</a>, 将解压后的后的文件夹放入 ES 根目录下的 plugins 目录下，重启 ES 即可使用.</p>
+<h3 id="文档搜索">文档搜索</h3>
+<p>早期的全文检索会为整个文档集合建立一个很大的倒排索引并将其写入到磁盘。 被写入的索引不可变化,一旦新的索引就绪，旧的就会被其替换.如果你需要让一个新的文档可被搜索，你需要重建整个索引。这要么对一个索引所能包含的数据量造成了很大的限制，要么对索引可被更新的频率造成了很大的限制。</p>
+<p>如何在保留不变性的前提下实现倒排索引的更新?</p>
+<p>用更多的索引。通过增加新的补充索引来反映新的修改，而不是直接重写整个倒排索引。每一个倒排索引都会被轮流查询到,从最早的开始查询完后再对结果进行合并。</p>
+<p>当一个文档被删除时，它实际上只是在文件中被标记删除。一个被标记删除的文档仍然可以被查询匹配到，但它会在最终结果被返回前从结果集中过滤掉。 文档更新也是类似的操作方式:当一个文档被更新时，旧版本文档被标记删除，文档的新版本被索引到一个新的段中。可能两个版本的文档都会被一个查询匹配到，但被删除的那个旧版本文档在结果集返回前就已经被移除。
+当一个查询被触发，所有已知的段按顺序被查询。词项统计会对所有段的结果进行聚合,此时会将标记删除的数据真正的删除.</p>
+<h3 id="近实时搜索">近实时搜索</h3>
+<p>Elasticsearch 的主要功能就是搜索,但是Elasticsearch的搜索功能不是实时的,而是近实时的,主要原因在于ES搜索是分段搜索.</p>
+<p>ES中的每一段就是一个倒排索引,最新的数据更新会体现在最新的段中,而最新的段落盘之后ES才能进行搜索,所以磁盘性能极大影响了ES软件的搜索.ES的主要作用就是快速准确的获取想要的数据,所以降低处理数据的延迟就显得尤为重要.</p>
+<p>ES近实时搜索实现:
+<img alt="Elasticsearch详解-04" src="/iblog/posts/annex/images/essays/Elasticsearch%E8%AF%A6%E8%A7%A3-04.png"></p>
+<ol>
+<li>一个文档被索引之后，就会被添加到内存缓冲区，并且追加到了 translog 事务日志中;(先写入索引中,再写入到日志中,目的防止数据丢失,类似数据库中的事务日志)</li>
+<li>将内存缓冲区中的分片刷新到磁盘中(refresh);此时缓冲区的数据可被搜索,当完全将数据写入磁盘会清空缓冲区中的数据;</li>
+<li>随着不断的刷写,磁盘中的文件会越来越多,此时需要文件段合并;当一个新的索引文件产生之后,文件的更新,删除便会体现出,此时在合并文件的时候便会真正的将数据删除;小的段被合并到大的段，然后这些大的段再被合并到更大的段;</li>
+</ol>
+<h2 id="优化">优化</h2>
+<p>Elasticsearch 在数据量很大的情况下（数十亿级别）如何提高查询效率？</p>
+<h3 id="合理设置分片数">合理设置分片数</h3>
+<p>分片和副本的设计为 ES 提供了支持分布式和故障转移的特性，但并不意味着分片和副本是可以无限分配的。而且索引的分片完成分配后由于索引的路由机制，我们是不能重新修改分片数的.否则将无法找到对应的数据.</p>
+<ul>
+<li>控制每个分片占用的硬盘容量不超过 ES 的最大 JVM 的堆空间设置，因此，如果索引的总容量在 500G 左右，那分片大小在 16 个左右即可;</li>
+<li>考虑一下 node 数量，一般一个节点有时候就是一台物理机，如果分片数过多，大大超过了节点数，很可能会导致一个节点上存在多个分片，一旦该节点故障，即使保持了 1 个以上的副本，同样有可能会导致数据丢失，集群无法恢复。所以， 一般都设置分片数不超过节点数的 3 倍;</li>
+<li>主分片，副本和节点最大数之间数量，我们分配的时候可以参考： 节点数&lt;=主分片数 *（副本数+1）;</li>
+</ul>
+<h3 id="文件缓冲区httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance"><a href="https://doocs.github.io/advanced-java/#/docs/high-concurrency/es-optimizing-query-performance">文件缓冲区</a></h3>
+<p>往 ES 里写的数据，实际上都写到磁盘文件里去了，查询的时候，操作系统会将磁盘文件里的数据自动缓存到 filesystem cache 里面去;ES 的搜索引擎严重依赖于底层的 filesystem cache ，你如果给 filesystem cache 更多的内存，尽量让内存可以容纳所有的 idx segment file  索引数据文件，那么你搜索的时候就基本都是走内存的，性能会非常高。</p>
+<blockquote>
+<p>案例: 某个公司 ES 节点有 3 台机器，每台机器看起来内存很多，64G，总内存就是 64 * 3 = 192G 。每台机器给 ES jvm heap 是 32G ，那么剩下来留给 filesystem cache 的就是每台机器才 32G ，总共集群里给 filesystem cache 的就是 32 * 3 = 96G 内存。而此时，整个磁盘上索引数据文件，在 3 台机器上一共占用了 1T 的磁盘容量，ES 数据量是 1T ，那么每台机器的数据量是 300G 。这样性能好吗？ filesystem cache 的内存才 100G，十分之一的数据可以放内存，其他的都在磁盘，然后你执行搜索操作，大部分操作都是走磁盘，性能肯定差。</p>
+</blockquote>
+<p>归根结底，你要让 ES 性能要好，最佳的情况下，就是你的机器的内存，至少可以容纳你的总数据量的一半。</p>
+<p>根据生产环境实践经验，最佳的情况下，是仅仅在 ES 中就存少量的数据，就是你要用来搜索的那些索引，如果内存留给 filesystem cache 的是 100G，那么你就将索引数据控制在 100G 以内，这样的话，你的数据几乎全部走内存来搜索，性能非常之高，一般可以在 1 秒以内。</p>
+<p>比如说你现在有一行数据。 id,name,age &hellip;. 30 个字段。但是你现在搜索，只需要根据 id,name,age 三个字段来搜索。如果你傻乎乎往 ES 里写入一行数据所有的字段，就会导致说 90% 的数据是不用来搜索的，结果硬是占据了 ES 机器上的 filesystem cache 的空间，单条数据的数据量越大，就会导致 filesystem cahce 能缓存的数据就越少。其实，仅仅写入 ES 中要用来检索的少数几个字段就可以了，比如说就写入 ES id,name,age 三个字段，然后你可以把其他的字段数据存在 mysql/hbase 里，我们一般是建议用 ES + hbase 这么一个架构。</p>
+<p>写入 ES 的数据最好小于等于，或者是略微大于 ES 的 filesystem cache 的内存容量。然后你从 ES 检索可能就花费 20ms，然后再根据 ES 返回的 id 去 hbase 里查询，查 20 条数据，可能也就耗费个 30ms，可能你原来那么玩儿，1T 数据都放 es，会每次查询都是 5~10s，现在可能性能就会很高，每次查询就是 50ms。</p>
+<h3 id="数据预热httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance"><a href="https://doocs.github.io/advanced-java/#/docs/high-concurrency/es-optimizing-query-performance">数据预热</a></h3>
+<p>假如说，哪怕是你就按照上述的方案去做了，ES 集群中每个机器写入的数据量还是超过了 filesystem cache 一倍，比如说你写入一台机器 60G 数据，结果 filesystem cache 就 30G，还是有 30G 数据留在了磁盘上。</p>
+<p>其实可以做数据预热。</p>
+<p>举个例子，拿微博来说，你可以把一些大 V，平时看的人很多的数据，你自己提前后台搞个系统，每隔一会儿，自己的后台系统去搜索一下热数据，刷到 filesystem cache 里去，后面用户实际上来看这个热数据的时候，他们就是直接从内存里搜索了，很快。</p>
+<p>或者是电商，你可以将平时查看最多的一些商品，比如说 iphone 8，热数据提前后台搞个程序，每隔 1 分钟自己主动访问一次，刷到 filesystem cache 里去。</p>
+<p>对于那些你觉得比较热的、经常会有人访问的数据，最好做一个专门的缓存预热子系统，就是对热数据每隔一段时间，就提前访问一下，让数据进入 filesystem cache 里面去。这样下次别人访问的时候，性能一定会好很多。</p>
+<h3 id="冷热分离httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance"><a href="https://doocs.github.io/advanced-java/#/docs/high-concurrency/es-optimizing-query-performance">冷热分离</a></h3>
+<p>ES 可以做类似于 mysql 的水平拆分，就是说将大量的访问很少、频率很低的数据，单独写一个索引，然后将访问很频繁的热数据单独写一个索引。最好是将冷数据写入一个索引中，然后热数据写入另外一个索引中，这样可以确保热数据在被预热之后，尽量都让他们留在 filesystem os cache 里，别让冷数据给冲刷掉。</p>
+<p>假设你有 6 台机器，2 个索引，一个放冷数据，一个放热数据，每个索引 3 个 shard。3 台机器放热数据 index，另外 3 台机器放冷数据 index。然后这样的话，你大量的时间是在访问热数据 index，热数据可能就占总数据量的 10%，此时数据量很少，几乎全都保留在 filesystem cache 里面了，就可以确保热数据的访问性能是很高的。但是对于冷数据而言，是在别的 index 里的，跟热数据 index 不在相同的机器上，大家互相之间都没什么联系了。如果有人访问冷数据，可能大量数据是在磁盘上的，此时性能差点，就 10% 的人去访问冷数据，90% 的人在访问热数据，也无所谓了。</p>
+<h3 id="document模型设计httpsdoocsgithubioadvanced-javadocshigh-concurrencyes-optimizing-query-performance"><a href="https://doocs.github.io/advanced-java/#/docs/high-concurrency/es-optimizing-query-performance">document模型设计</a></h3>
+<p>对于 MySQL，我们经常有一些复杂的关联查询。在 ES 里该怎么玩儿，ES 里面的复杂的关联查询尽量别用，一旦用了性能一般都不太好。</p>
+<p>最好是先在 Java 系统里就完成关联，将关联好的数据直接写入 ES 中。搜索的时候，就不需要利用 ES 的搜索语法来完成 join 之类的关联搜索了。</p>
+<p>document 模型设计是非常重要的，很多操作，不要在搜索的时候才想去执行各种复杂的乱七八糟的操作。ES 能支持的操作就那么多，不要考虑用 ES 做一些它不好操作的事情。如果真的有那种操作，尽量在 document 模型设计的时候，写入的时候就完成。另外对于一些太复杂的操作，比如 join/nested/parent-child 搜索都要尽量避免，性能都很差的。</p>
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diff --git a/docs/posts/detailed/java-arraylist/index.html b/docs/posts/detailed/java-arraylist/index.html
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+                        <h2 id="post_single_title">ArrayList详解</h2>
+                        <span id="post_page_title_date" class="date">2024.06.26</span>
+                        
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+                    <div class="post_content markdown"><h2 id="arraylist">ArrayList</h2>
+<p>在<code>List</code>接口实现类中，最常用的就是<code>ArrayList</code>，<code>ArrayList</code>类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删除元素。
+<code>ArrayList</code>继承了<code>AbstractList</code>，并实现了<code>List</code>、<code>RandomAccess</code>，<code>Cloneable</code>接口：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">RandomAccess</span><span class="p">,</span><span class="n">Cloneable</span><span class="p">,</span><span class="n">Serializable</span><span class="p">{}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="randomaccess">RandomAccess</h3>
+<p><code>Random</code>是随机的意思，<code>Access</code>是访问的意思，合起来<code>RandomAccess</code>就是随机访问的意思。
+<code>RandomAccess</code>接口是一个标记接口，用来标记实现的<code>List</code>集合具备快速随机访问的能力。
+所有的<code>List</code>实现都支持随机访问的，只是基于基本结构的不同，实现的速度不同罢了。</p>
+<p>当一个<code>List</code>拥有快速访问功能时，其遍历方法采用随机访问速度最快，而没有快速随机访问的<code>List</code>采用顺序访问的速度最快。
+如果集合中的数据量过大需要遍历时，此时需要格外注意，因为不同的遍历方式会影响很大，可以使用<code>instanceof</code>关键字来判断该类有没有<code>RandomAccess</code>标记：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 假设 list 数据量非常大,推荐写法
+</span></span><span class="line"><span class="cl">List&lt;Object&gt; list = ...;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">if(list instanceof RandomAccess){
+</span></span><span class="line"><span class="cl">    // 随机访问
+</span></span><span class="line"><span class="cl">    for (int i = 0;i&lt; list.size();i++) {
+</span></span><span class="line"><span class="cl">        System.out.println(list.get(i));
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}else {
+</span></span><span class="line"><span class="cl">    // 顺序访问
+</span></span><span class="line"><span class="cl">    for(Object obj: list) {
+</span></span><span class="line"><span class="cl">        System.out.println(obj);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在<code>List</code>中<code>ArrayList</code>被<code>RandomAccess</code>接口标记，而<code>LinkedList</code>没有被<code>RandomAccess</code>接口标记，所以<code>ArrayList</code>适合随机访问，而<code>LinkedList</code>适合顺序访问。</p>
+<h3 id="cloneable">Cloneable</h3>
+<p><code>Cloneable</code>接口是Java开发中常用的一个接口，它是一个标记接口。
+如果一个想要拷贝一个对象，就需要重写<code>Object</code>中的<code>clone</code>方法并让其实现<code>Cloneable</code>接口。如果只重写<code>clone</code>方法，不实现<code>Cloneable</code>接口就会报<code>CloneNotSupportedException</code>异常。</p>
+<p><code>clone</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>应当注意的是，<code>clone()</code>方法并不是<code>Cloneable</code>接口的方法，而是<code>Object</code>的一个<code>protected</code>方法。
+<code>Cloneable</code>接口只是规定，如果一个类没有实现<code>Cloneable</code>接口又调用了<code>clone</code>方法，就会抛出<code>CloneNotSupportedException</code>。
+换言之，<code>clone</code>方法规定了想要拷贝对象，就需要实现<code>Cloneable</code>方法，<code>clone</code>方法让<code>Cloneable</code>接口变得有意义。</p>
+<p>拷贝分为浅拷贝与深拷贝：</p>
+<ul>
+<li>浅拷贝：被复制对象的所有值属性都含有与原来对象的相同，而所有的对象引用属性仍然指向原来的对象；</li>
+<li>深拷贝：在浅拷贝的基础上，所有引用其他对象的变量也进行了<code>clone</code>，并指向被复制过的新对象；</li>
+</ul>
+<p>如果一个被复制的属性都是基本类型，那么只需要实现当前类的<code>Cloneable</code>机制就可以了，此为浅拷贝。
+如果被复制对象的属性包含其他实体类对象引用，那么这些实体类对象都需要实现<code>Cloneable</code>接口并覆盖<code>clone</code>方法。
+<code>ArrayList</code>中<code>clone</code>方法可以创建一个浅拷贝。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// ArrayList类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">transient</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elementData</span><span class="p">;</span><span class="w">     
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Returns a shallow copy of this &lt;tt&gt;ArrayList&lt;/tt&gt; instance.  (The
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * elements themselves are not copied.)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return a clone of this &lt;tt&gt;ArrayList&lt;/tt&gt; instance
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 调用Object类的clone方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ArrayList</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">ArrayList</span><span class="o">&lt;?&gt;</span><span class="p">)</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将集合中的元素进行拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="p">.</span><span class="na">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="p">.</span><span class="na">modCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">v</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// this shouldn&#39;t happen, since we are Cloneable</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InternalError</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// Arrays类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Arrays</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="nf">copyOf</span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newLength</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">copyOf</span><span class="p">(</span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="n">newLength</span><span class="p">,</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">getClass</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="p">,</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="nf">copyOf</span><span class="p">(</span><span class="n">U</span><span class="o">[]</span><span class="w"> </span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newLength</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">T</span><span class="o">[]&gt;</span><span class="w"> </span><span class="n">newType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">copy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">((</span><span class="n">Object</span><span class="p">)</span><span class="n">newType</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p">(</span><span class="n">Object</span><span class="p">)</span><span class="n">Object</span><span class="o">[]</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">?</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="o">[</span><span class="n">newLength</span><span class="o">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">Array</span><span class="p">.</span><span class="na">newInstance</span><span class="p">(</span><span class="n">newType</span><span class="p">.</span><span class="na">getComponentType</span><span class="p">(),</span><span class="w"> </span><span class="n">newLength</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">copy</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">original</span><span class="p">.</span><span class="na">length</span><span class="p">,</span><span class="w"> </span><span class="n">newLength</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">copy</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>ArrayList</code>中核心方法最终调用<code>Arrays.copyOf</code>方法，其中调用<code>Arrays.newInstance</code>方法或者创建一个新数组，<code>Arrays.newInstance</code>方法作用，是创建具有指定组件类型和长度的新数组。
+所以不论怎样都会创建一个<code>Object</code>数组。最后使用<code>System.arraycopy</code>方法将之前的旧数组中的元素拷贝到新创建的数组中，然后赋值给<code>ArrayList.elementData</code>对象并返回。</p>
+<p>如果需要深拷贝，即复制对象及其引用的所有对象，需要手动实现拷贝逻辑，通常涉及遍历列表并复制每个元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Item</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Item</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayListCopy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建并初始化一个ArrayList</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Item</span><span class="o">&gt;</span><span class="w"> </span><span class="n">originalList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;C&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 深拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Item</span><span class="o">&gt;</span><span class="w"> </span><span class="n">deepCopy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Item</span><span class="w"> </span><span class="n">item</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">originalList</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">deepCopy</span><span class="p">.</span><span class="na">add</span><span class="p">((</span><span class="n">Item</span><span class="p">)</span><span class="w"> </span><span class="n">item</span><span class="p">.</span><span class="na">clone</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 修改原始列表的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">).</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Z&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Original List: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">originalList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Deep Copy: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">deepCopy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="arraylist扩容">ArrayList扩容</h3>
+<p>因为<code>ArrayList</code>底层使用数组保存数据的，而数组一旦被创建就不能改变大小，但是<code>ArrayList</code>的长度是可以改变的，所以可以通过<code>ArrayList</code>类中的<code>add</code>方法找到数组扩容方法。
+<code>add</code>方法调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">add 
+</span></span><span class="line"><span class="cl">    -&gt; ensureCapacityInternal()
+</span></span><span class="line"><span class="cl">    -&gt; calculateCapacity()
+</span></span><span class="line"><span class="cl">    -&gt; ensureExplicitCapacity()
+</span></span><span class="line"><span class="cl">    -&gt; grow()
+</span></span></code></pre></div><p>通过<code>add</code>方法，最终找到了<code>grow</code>方法，也就是扩容的核心方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">grow</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">minCapacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// overflow-conscious code</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elementData</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">minCapacity</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">minCapacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">MAX_ARRAY_SIZE</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hugeCapacity</span><span class="p">(</span><span class="n">minCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// minCapacity is usually close to size, so this is a win:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>ArrayList</code>如果没有指定容量创建数组，默认会创建一个长度为10的数组用来保存元素，之后通过<code>grow</code>方法中的这段代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p><code>&gt;&gt;</code>右移几位就是相当于除以2的几次幂，所以每次扩容都是原容量的1.5倍。最后通过<code>Arrays.copyOf</code>方法将之前的数组中元素，全部移到新创建的数组上。</p>
+<p>由于频繁的扩容数组会对性能产生影响，如果在<code>ArrayList</code>中要存储很大的数据，需要在<code>ArrayList</code>的有参构造中指定数组的长度，来减少扩容的次数。
+需要注意的是创建指定长度的<code>ArrayList</code>，在没有<code>add</code>之前<code>ArrayList</code>中的数组已经初始化了，但是<code>List</code>的大小没变，因为<code>List</code>的大小是由<code>size</code>决定的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="p">(</span><span class="n">1000000</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><h3 id="arraylist与linkedlist">ArrayList与LinkedList</h3>
+<p><code>ArrayList</code>与<code>LinkedList</code>性能比较是一道经典的面试题，先说答案<code>ArrayList</code>查找快，增删慢，而<code>LinkedList</code>增删快，查找慢。
+造成这种原因是因为底层的数据结构不一样。<code>ArrayList</code>底层是数组，而数组的中的元素内存分配都是连续的，并且数组中的元素只能存放一种，这就造成了数组中的元素地址是有规律的，数组中查找元素快速的原因正是利用了这一特点。
+查询方式为: 首地址＋(元素类型长度*下标)。例如：<code>new int arr[5]; arr</code>数组的地址假设为<code>0x1000</code>，那么<code>arr[3]</code>地址可看作为 <code>0x1000 + (3 * 4)</code>，3为数组下标，4为int元素类型长度。</p>
+<p>而<code>LinkedList</code>在Java中的底层结构是对象，每一个对象结点中都保存了下一个结点的位置形成的链表结构，由于<code>LinkedList</code>元素的地址是不连续的，所以没办法按照数组那样去查找，所以就比较慢。</p>
+<p>由于数组一旦分配了大小就不能改变，所以<code>ArrayList</code>在进行添加操作时会创建新的数组，如果要添加到<code>ArrayList</code>中的指定的位置，是通过<code>System.arraycopy</code>方法将数组进行复制，新的数组会将待插入的指定位置空余出来，最后在将元素添加到集合中。
+在进行删除操作时是通过<code>System.arraycopy</code>方法，将待删除元素后面剩余元素复制到待删除元素的位置。当<code>ArrayList</code>里有大量数据时，这时候去频繁插入或删除元素会触发底层数组频繁拷贝，所以效率不高，还会造成内存空间的浪费。</p>
+<p><code>LinkedList</code>在进行添加，删除操作时，会用二分查找法找到将要添加或删除的元素，之后再设置对象的下一个结点来进行添加或删除操作，所以增加删除的效率高。</p>
+<blockquote>
+<p>二分查找法：也称为折半查找法，是一种适用于大量数据查找的方法，但是要求数据必须的排好序的，每次以中间的值进行比较，根据比较的结果可以直接舍去一半的值，直至全部找完（可能会找不到）或者找到数据为止。
+此处LinkedList会比较查找的元素是距离头结点比较近，还是尾结点比较近，距离哪边较近则从哪边开始查找。</p>
+</blockquote>
+<p><code>ArrayList</code>获取元素效率非常的高，时间复杂度是<code>O(1)</code>，而查找、插入和删除元素效率似乎不太高，时间复杂度为<code>O(n)</code>。
+<code>LinkedList</code>与<code>ArrayList</code>相反，获取第几个元素依次遍历复杂度<code>O(n)</code>，添加到末尾复杂度<code>O(1)</code>，添加到指定位置复杂度<code>O(n)</code>，删除元素直接指针指向操作复杂度<code>O(1)</code>。</p>
+<p>注意，<code>ArrayList</code>的增删不一定比<code>LinkedList</code>效率低，但是<code>ArrayList</code>查找效率一定比<code>LinkedList</code>高。
+如果在靠近末尾的地方插入，那么<code>ArrayList</code>只需要移动较少的数据，而<code>LinkedList</code>则需要一直查找到列表尾部，反而耗费较多时间，这时<code>ArrayList</code>就比<code>LinkedList</code>要快。</p>
+<p>所以在实际开发中，<code>ArrayList</code>适用于需要快速随机访问和较少插入删除操作的场景，而<code>LinkedList</code>适用于频繁插入删除操作和需要实现队列或双端队列的场景。</p>
+<h3 id="线程安全">线程安全</h3>
+<p>众所周知，<code>ArrayList</code>是线程不安全的，因为它不保证在多线程环境下的同步操作，当多个线程同时访问和修改同一个<code>ArrayList</code>对象时可能会导致数据不一致或抛出异常。
+多线程下抛出<code>ConcurrentModificationException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果没有报错，需要多试几次</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrayList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">arrayList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">arrayList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>出现该异常的原因是集合中的<code>fail-fast</code>机制。在查看源码的时候，发现调用<code>remove</code>方法时，会执行<code>checkForComodification</code>方法。
+若<code>modCount</code>不等于<code>expectedModCount</code>，则抛出<code>ConcurrentModificationException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkForComodification</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那为什么会抛出<code>ConcurrentModificationException</code>异常呢？
+在调用<code>add</code>方法时，会修改<code>modCount++</code>。一个线程调用<code>add</code>方法，一个线程调用<code>next</code>遍历方法，都共同读取<code>modCount</code>变量的值。
+因为是多线程操作，<code>expectedModCount</code>、<code>modCount</code>变量为公共的，所以很容易出现<code>modCount != expectedModCount</code>，所以便抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 添加元素到指定的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">element</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IndexOutOfBoundsException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;Index: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Size: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 修改modCount</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ensureCapacity</span><span class="p">(</span><span class="n">size</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">  </span><span class="c1">// Increments modCount!!</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">element</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">size</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>因此，在多线程环境中使用<code>ArrayList</code>时，需要手动同步操作，或者使用线程安全的集合类。保证<code>ArrayList</code>线程安全有以下几种方法：</p>
+<ol>
+<li>可以使用 <code>Vector</code> 来代替 <code>ArrayList</code>。<code>Vector</code>是线程安全的<code>ArrayList</code>，但是由于底层是加了<code>synchronized</code>，性能略差不推荐使用；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List list = new Vector();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+<li>使用<code>Collections.synchronizedArrayList()</code> 来创建 <code>ArrayList</code>。使用<code>Collections</code>工具类来创建<code>ArrayList</code>的思路是，在<code>ArrayList</code>的外边套了一个<code>synchronized</code>外壳，来保证<code>ArrayList</code>线程安全；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List list = Collections.synchronizedArrayList();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+<li>使用<code>CopyOnWriteArrayList()</code>来保证 <code>ArrayList</code> 线程安全。<code>CopyWriteArrayList</code>字面意思就是在写的时候复制，主要思想就是读写分离的思想。
+<code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>，所以保证了某个线程在写的时候不会被打断；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">CopyOnWriteArrayList&lt;String&gt; list = new CopyOnWriteArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+</ol>
+<p>其中比较推荐的解决方案是使用<code>CopyOnWriteArrayList</code>。
+<code>CopyWriteArrayList</code>字面意思就是在写的时候复制，思想就是读写分离的思想。它的基本原理是每次修改操作都会创建该列表的一个新副本，因此读操作不需要加锁，可以并发执行。
+以下是<code>CopyOnWriteArrayList</code>的<code>add()</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The array, accessed only via getArray/setArray. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The lock protecting all mutators */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Gets the array.  Non-private so as to also be accessible
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * from CopyOnWriteArraySet class.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="nf">getArray</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Appends the specified element to the end of this list.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param e element to be appended to this list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@code true}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">lock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elements</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">newElements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elements</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newElements</span><span class="o">[</span><span class="n">len</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setArray</span><span class="p">(</span><span class="n">newElements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>保证了某个线程在写的时候不会被打断。
+可以看到源码开始先是复制了一份数组，同一时刻只有一个线程写，其余的线程会读。在复制的数组上边进行写操作，写好以后在返回<code>true</code>。
+这样就把读写进行了分离，写好以后因为<code>array</code>加了<code>volatile</code>修饰，所以该数组是对于其他的线程是可见的，就会读取到最新的值。
+由于每次写操作都会创建一个数组的新副本，所以写操作的开销较大。但是读取操作非常高效且不需要加锁，因此适用于读操作远多于写操作的场景，例如缓存、白名单等。</p>
+<h3 id="arraylist安全删除">ArrayList安全删除</h3>
+<p>在<code>ArrayList</code>中删除元素时，&ldquo;安全删除&rdquo; 指的是在删除元素过程中避免出现异常或错误，并确保集合的结构和元素的状态保持一致。
+在使用增强型<code>for-each</code>循环遍历<code>ArrayList</code>时，如果尝试删除元素，会抛出<code>ConcurrentModificationException</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayListError</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;C&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;D&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">element</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">element</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">element</span><span class="p">);</span><span class="w"> </span><span class="c1">// 这会抛出 ConcurrentModificationException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在前面讲过<code>add</code>方法，会操作<code>modCount</code>变量的值，在查看源码的时候，发现调用<code>remove</code>方法时，也会操作<code>modCount</code>变量的值。
+当调用<code>remove</code>方法时执行了<code>modCount++</code>，此时<code>modCount</code>变成了<code>N+1</code>。然后接着再循环中遍历调用<code>next</code>方法，调用<code>checkForComodification</code>比较<code>expectedModCount</code>和<code>modCount</code>的大小，此时<code>modCount != expectedModCount</code>，便抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkForComodification</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c1">// 删除指定位置的元素 </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RangeCheck</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 修改modCount</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">modCount</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">E</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">E</span><span class="p">)</span><span class="w"> </span><span class="n">elementData</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">numMoved</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">numMoved</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">numMoved</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="o">[--</span><span class="n">size</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="c1">// Let gc do its work</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">oldValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>安全删除的关键在于，确保在遍历和删除操作中不会同时对集合的结构造成不一致性，从而导致程序运行时出现异常或者结果不符合预期。</p>
+<p>最经典的解决方案是使用<code>Iterator</code>遍历集合，在遍历过程中删除元素。在使用迭代器遍历<code>ArrayList</code>时，迭代器会维护一个<code>expectedModCount</code>，它记录了迭代开始时的<code>modCount</code>。
+每次调用迭代器的<code>next</code>方法时，都会检查当前的<code>modCount</code>是否与<code>expectedModCount</code>相等，如果不相等就抛出<code>ConcurrentModificationException</code>异常。使用迭代器的<code>remove()</code>方法能够确保在删除元素时，同步更新，从而避免异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ArrayList&lt;String&gt; list = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 添加元素到列表中
+</span></span><span class="line"><span class="cl">Iterator&lt;String&gt; iterator = list.iterator();
+</span></span><span class="line"><span class="cl">while (iterator.hasNext()) {
+</span></span><span class="line"><span class="cl">    String element = iterator.next();
+</span></span><span class="line"><span class="cl">    if (/* 满足删除条件 */) {
+</span></span><span class="line"><span class="cl">        iterator.remove(); // 使用迭代器的 remove 方法安全删除元素
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></div>
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diff --git a/docs/posts/detailed/java-hashmap/index.html b/docs/posts/detailed/java-hashmap/index.html
new file mode 100644
index 00000000..7cbb8eaf
--- /dev/null
+++ b/docs/posts/detailed/java-hashmap/index.html
@@ -0,0 +1,1060 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>HashMap详解 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问" />
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+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap">
+                    HashMap
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e7%bb%93%e6%9e%84">
+                    HashMap结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hash%e5%86%b2%e7%aa%81">
+                    Hash冲突
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e5%ae%b9%e9%87%8f">
+                    HashMap容量
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e6%89%a9%e5%ae%b9">
+                    HashMap扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#17%e6%89%a9%e5%ae%b9">
+                    1.7扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#18%e6%89%a9%e5%ae%b9">
+                    1.8扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
+        
+        
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e8%80%83%e6%96%87%e7%ab%a0">
+                    参考文章
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
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+
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+                        <h2 id="post_single_title">HashMap详解</h2>
+                        <span id="post_page_title_date" class="date">2021.05.03</span>
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+                    <div class="post_content markdown"><h2 id="hashmap">HashMap</h2>
+<p><code>HashMap</code>是一个散列表，它存储的内容是键值对(<code>key-value</code>)映射。
+<code>HashMap</code>实现了<code>Map</code>接口，根据键的<code>HashCode</code>值存储数据，具有很快的访问速度，最多允许一条记录的键为<code>null</code>，不支持线程同步。<code>HashMap</code>是无序的，即不会记录插入的顺序。</p>
+<p>相关操作：</p>
+<ul>
+<li>存储：通过<code>key</code>的<code>hashcode</code>方法找到在<code>hashMap</code>存储的位置，如果该位置有元素则通过<code>equals</code>方法进行比较，如果<code>equals</code>返回值为<code>true</code>，则覆盖<code>value</code>；
+如果<code>equals</code>返回值为<code>false</code>则在该数组元素的头部追加该元素，形成一个链表结构；</li>
+<li>读取：通过<code>key</code>的<code>hashcode</code>方法获取元素存在该数组的位置，然后通过<code>equals</code>拿到该值；</li>
+</ul>
+<p>总的来说<code>hashMap</code>底层将<code>key-value</code>当成一个整体来处，<code>hashMap</code>底层采用一个<code>Entry</code>数组保存所有的键值对。
+当存储一个<code>entry</code>对象时，会根据<code>key</code>的<code>hashCode</code>来决定存放在数组中的位置，再根据<code>equals</code>方法来确定在链表中的位置，读取一个<code>entry</code>对象。
+<code>equals</code>和<code>hashCode</code>在<code>hashMap</code>中就像一个坐标一样，来定位<code>hashMap</code>中的值。</p>
+<h3 id="hashmap结构">HashMap结构</h3>
+<p><img alt="HashMap结构" src="/iblog/posts/annex/images/essays/HashMap%E7%BB%93%E6%9E%84.png"></p>
+<p>在JDK1.7及之前结构为<code>数组+单向链表</code>，JDK1.8及之后结构为<code>数组 + 单向链表/红黑树</code>。
+在JDK1.8时，如果存储<code>Map</code>中数组元素对应的索引的每个链表超过8，就将单向链表转化为红黑树，当红黑树的节点少于6个的时候又开始使用链表。</p>
+<p>那么为什么要使用红黑树？
+当有发生大量的<code>hash</code>冲突时，因为链表遍历效率很慢，为了提升查询的效率，所以使用了红黑树的数据结构。</p>
+<p>为什么不一开始就用红黑树代替链表结构？</p>
+<blockquote>
+<p>Because TreeNodes are about twice the size of regular nodes, we use them only when bins contain enough nodes to warrant use  (see TREEIFY_THRESHOLD).
+And when they become too small (due to removal or resizing) they are converted back to plain bins.</p>
+</blockquote>
+<p>这是JDK文档注释，大意为：单个<code>TreeNode</code>需要占用的空间大约是普通<code>Node</code>的两倍，所以只有当包含足够多的<code>Nodes</code>时才会转成<code>TreeNodes</code>，而是否足够多就是由<code>TREEIFY_THRESHOLD</code>的值(默认值8)决定的。
+而当桶中节点数由于移除或者<code>resize</code>变少后，又会变回普通的链表的形式，以便节省空间，这个阈值是<code>UNTREEIFY_THRESHOLD</code>(默认值6)。</p>
+<p>为什么树化阈值要设置为8？
+如果<code>hashCode</code>分布良好，也就是<code>hash</code>计算的结果离散好的话，那么红黑树这种形式是很少会被用到的，因为各个值都均匀分布，很少出现链表很长的情况。
+在理想情况下，链表长度符合泊松分布，各个长度的命中概率依次递减，当长度为8的时候，概率仅为0.00000006。
+这是一个小于千万分之一的概率，通常我们的<code>Map</code>里面是不会存储这么多的数据的，所以通常情况下，并不会发生从链表向红黑树的转换。</p>
+<p><code>HashMap</code>是通过<code>hash</code>算法来判断对象应该放在哪个桶里面的。JDK并不能阻止我们用户实现自己的哈希算法，如果我们故意把哈希算法变得不均匀，那么每次存放对象很容易造成<code>hash</code>冲突。
+链表长度超过8就转为红黑树的设计，更多的是为了防止用户自己实现了不好的哈希算法时导致链表过长，从而导致查询效率低，而此时转为红黑树更多的是一种保底策略，用来保证极端情况下查询的效率。
+红黑树的引入保证了在大量<code>hash</code>冲突的情况下，<code>HashMap</code>还具有良好的查询性能。</p>
+<p>那么在JDK1.8引入红黑树后，如果单链表节点个数超过8个是否一定会树化？
+这是不一定的，在进行树化之前会进行判断<code>(n = tab.length) &lt; MIN_TREEIFY_CAPACITY)</code>是否需要扩容，如果表中数组元素小于这个阈值（默认是64），就会进行扩容。
+因为扩容不仅能增加表中的容量，还能缩短单链表的节点数，从而更长远的解决链表遍历慢问题。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Replaces all linked nodes in bin at index for given hash unless
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * table is too small, in which case resizes instead.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">treeifyBin</span><span class="p">(</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tab</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MIN_TREEIFY_CAPACITY</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">tl</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">replacementTreeNode</span><span class="p">(</span><span class="n">e</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tl</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">hd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">p</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tl</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tl</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">tab</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hd</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">hd</span><span class="p">.</span><span class="na">treeify</span><span class="p">(</span><span class="n">tab</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hash冲突">Hash冲突</h3>
+<p>在<code>HashMap</code>中，哈希冲突，也叫<code>Hash</code>碰撞，是指两个不同的键通过同一散列函数计算得到的哈希值相同，从而映射到同一个桶中。
+当插入<code>HashMap</code>中元素的<code>key</code>出现重复时，这个时候就发生了<code>Hash</code>冲突了。哈希冲突是哈希表必须处理的问题。</p>
+<p>链地址法是处理哈希冲突的常见方法之一，它在每个桶中使用一个链表来存储所有映射到该桶的键值对。具体插入步骤：</p>
+<ol>
+<li>计算键的哈希值并确定其在数组中的位置；</li>
+<li>如果桶为空，直接将键值对存储在该桶中；</li>
+<li>如果桶不为空，则遍历桶中的链表，检查是否存在相同的键；</li>
+</ol>
+<ul>
+<li>如果存在相同的键，更新对应的值；</li>
+<li>如果不存在相同的键，将新的键值对添加到链表的末尾；</li>
+</ul>
+<p>在Java8及更高版本中，为了提高性能，当单个桶中的链表长度超过一定阈值（默认是 8）时，会将链表转换为红黑树。
+这种方法在大量冲突的情况下提供了更高效的查找和插入性能。具体插入步骤：</p>
+<ol>
+<li>计算键的哈希值确定存储位置；</li>
+<li>如果存储位置为空，则直接插入新键值对；</li>
+<li>如果存储位置已有节点，当链表长度超过阈值（默认为 8），将链表转换为红黑树，否则继续用链表存储；</li>
+<li>如果当前结点为红黑树结点，则根据节点的哈希值和键值比较，找到合适的插入位置；插入后，根据红黑树的性质进行调整，保持平衡；</li>
+<li>当桶中元素数量减少到一定阈值以下时（默认是 6），会将红黑树转换回链表，以减少内存开销；</li>
+</ol>
+<h3 id="hashmap容量">HashMap容量</h3>
+<p><code>HashMap</code>在创建时需要指定初始容量，如果不指定默认是16。初始容量指的是<code>HashMap</code>中桶的数量，即存储键值对的数组大小。
+如果能预估要存储的键值对数量，可以在创建<code>HashMap</code>时指定初始容量，以避免频繁的扩容操作。</p>
+<p>如果指定容量大小为10，那么实际大小是多少？
+先说答案，实际大小是16，其容量为不小于指定容量的2的N次方。</p>
+<p>为什么容量始终是2的N次方？
+为了减少<code>Hash</code>碰撞，尽量使<code>Hash</code>算法的结果均匀分布。</p>
+<p>当使用<code>put</code>方法时，到底存入<code>HashMap</code>的哪个数组中？
+这是通过<code>hash</code>算法决定的，如果某一个数组中的链表过长旧会影响查询的效率。为了避免出现<code>hash</code>碰撞，让<code>hash</code>尽可能的散列分布，就需要在<code>hash</code>算法上做文章。</p>
+<p>JDK1.7通过逻辑与运算，判断这个元素该进入哪个数组。在下面的代码中<code>length</code>的长度始终为不小于指定容量的2的N次方。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">indexFor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">h</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为了更好的理解这个方法，举个例子，假设<code>h=2</code>或<code>h=3</code>，<code>length=15</code>，执行<code>indexFor</code>方法，最终逻辑与运算后的结果是一致的，因为最终结果是一致的所以就导致了<code>hash</code>碰撞。
+这种问题多了以后会造成容器中的元素分布不均匀，都分配在同一个数组上，在查询的时候就减慢了查询的效率，另一方面也造成空间的浪费。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">-- 2转换为2进制与15-1进行&amp;运算
+</span></span><span class="line"><span class="cl">  0000 0010
+</span></span><span class="line"><span class="cl">&amp; 0000 1110 
+</span></span><span class="line"><span class="cl">———————————— 
+</span></span><span class="line"><span class="cl">  0000 1110
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 3转换为2进制与15-1进行&amp;运算
+</span></span><span class="line"><span class="cl">  0000 0011
+</span></span><span class="line"><span class="cl">&amp; 0000 1110 
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0000 1110
+</span></span></code></pre></div><p>为了避免上面<code>length=15</code>这类问题出现，所以集合的容量采用必须是2的N次幂这种方式。
+因为2的N次幂的结果减一转换为二进制后都是以<code>...1111</code>结尾的，所以在进行逻辑与运算时碰撞几率小。</p>
+<p>在JDK1.8中，在<code>putVal</code>方法中通过<code>i = (n - 1) &amp; hash</code>来计算key的散列地址：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">putVal</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">onlyIfAbsent</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">evict</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 此处省略了代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// i = (n - 1) &amp; hash]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 省略了代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这里的&quot;&amp;&ldquo;等同于&rdquo;%&quot;，但是&quot;%&ldquo;运算的速度并没有&rdquo;&amp;&ldquo;的操作速度快。
+&ldquo;&amp;&ldquo;操作能代替&rdquo;%&ldquo;运算，但必须满足一定的条件，即<code>a%b=a&amp;(b-1)</code>仅当b是2的n次方的时候才成立。</p>
+<p>容器容量怎么保持始终为2的N次方？
+<code>HashMap</code>的<code>tableSizeFor</code>方法做了处理，能保证永远都是2的N次幂。
+如果用户指定了初始容量，那么<code>HashMap</code>会计算出比该数大的第一个2的幂作为初始容量。另外就是在扩容的时候，也是进行成倍的扩容，即4变成8、8变成16。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Returns a power of two size for the given target capacity.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">tableSizeFor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">cap</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 假设n=17</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = 00010001 - 00010000 = 00010000 = 16</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cap</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00010000 | 00001000) = 00011000 = 24</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011000 | 00000110) = 00011110 = 30</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011110 | 00000001) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011111 | 00000000) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">8</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011111 | 00000000) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">16</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = 00011111 = 31，MAXIMUM_CAPACITY：Integer的最大长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// (31 &lt; 0) ? 1 : (31 &gt;= Integer的最大长度) ? Integer的最大长度 : 31 + 1 ;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 即最终返回 32 = 2 的 (n=5)次方</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>发现上面在进行<code>&gt;&gt;&gt;</code>操作时会将<code>cap</code>变量的二进制值变为最高位后边全是1，即<code>00010001 -&gt; 00011111</code>，所以这个算法就导致了任意传入一个数值，会将该数字变为它的2倍减1，因为任何尾数全为1的在加1都为2的倍数。
+至于开头减1，是因为如果给定的n已经是2的次幂，但是不进行减1操作的话，那么得到的值就是大于给定值的最小2的次幂值，例如，传入4就会返回8。
+这里面最大右移到16位，因为最大值是32个1，这是int类型存储变量的最大值，在往后就没意义了。</p>
+<p><code>HashMap</code>默认初始化容量为什么是16？
+这个问题没有找到相关解释。我推断这应该就是个经验值，既然一定要设置一个默认的<code>2^n</code>作为初始值，那么就需要在效率和内存使用上做一个权衡。
+这个值既不能太小，也不能太大，太小了就有可能频繁发生扩容，影响效率；太大了又浪费空间，不划算。所以16就作为一个经验值被采用了。</p>
+<p>关于默认容量的定义，故意把16写成<code>1 &lt;&lt; 4</code>这种形式，就是提醒开发者，这个地方要是2的次幂，与上面呼应。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * The default initial capacity - MUST be a power of two.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w"> </span><span class="c1">// aka 16</span><span class="w">
+</span></span></span></code></pre></div><p>那么<code>HashMap</code>初始化容量设置多少合适？
+当我们使用<code>HashMap(int initialCapacity)</code>来初始化容量的时候，<code>HashMap</code>并不会使用我们传进来的<code>initialCapacity</code>直接作为初始容量。
+JDK会默认帮我们计算一个相对合理的值当做初始容量，所谓合理值，其实是找到第一个比用户传入的值大的2的幂。
+如果创建<code>HashMap</code>初始化容量设置为7，那么<code>HashMap</code>通过计算会创建一个初始化为8的<code>HashMap</code>。当<code>HashMap</code>中的元素到<code>0.75 * 8 = 6</code>就会进行<strong>扩容</strong>，这明显是我们不希望看到的。</p>
+<blockquote>
+<p>负载因子，表示HashMap满的程度，默认值为0.75f，也就是说默认情况下，当HashMap中元素个数达到了容量的3/4的时候就会进行自动扩容；</p>
+</blockquote>
+<p>设置多少合适，可以参考JDK8中<code>putAll</code>方法中的实现：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">(int) ((float) expectedSize / 0.75F + 1.0F);
+</span></span></code></pre></div><p>通过<code>expectedSize/0.75F+1.0F</code>计算，将初始化容量设置为7带入，得到<code>7/0.75+1=10</code>，10经过JDK处理之后，会被设置成16，这就大大的减少了扩容的几率。
+当我们明确知道<code>HashMap</code>中元素的个数的时候，把默认容量设置成<code>expectedSize/0.75F+1.0F</code> 是一个在性能上相对好的选择，但同时也会牺牲些内存。</p>
+<p>这个算法在<code>guava</code>中也有实现，开发的时候，可以直接通过<code>Maps</code>类创建一个<code>HashMap</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Maps</span><span class="p">.</span><span class="na">newHashMapWithExpectedSize</span><span class="p">(</span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">newHashMapWithExpectedSize</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedSize</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="p">(</span><span class="n">capacity</span><span class="p">(</span><span class="n">expectedSize</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">capacity</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedSize</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">expectedSize</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">3</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CollectPreconditions</span><span class="p">.</span><span class="na">checkNonnegative</span><span class="p">(</span><span class="n">expectedSize</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;expectedSize&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">expectedSize</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">expectedSize</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1073741824</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)((</span><span class="kt">float</span><span class="p">)</span><span class="n">expectedSize</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">75F</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">.</span><span class="na">0F</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">2147483647</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hashmap扩容">HashMap扩容</h3>
+<p>随着<code>HashMap</code>中的元素增加，<code>Hash</code>碰撞导致获取元素方法的效率就会越来越低。为了保证获取元素方法的效率，所以针对<code>HashMap</code>中的数组进行扩容。
+扩容数组的方式只能再去开辟一个新的数组，并把之前的元素转移到新数组上。</p>
+<p><code>HashMap</code>的容量是有上限的，必须小于<code>1&lt;&lt;30</code>，即<code>1073741824</code>。如果容量超出了这个数，则不再增长，且阈值会被设置为<code>Integer.MAX_VALUE</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// Java8
+</span></span><span class="line"><span class="cl">if (oldCap &gt;= MAXIMUM_CAPACITY) {
+</span></span><span class="line"><span class="cl">    threshold = Integer.MAX_VALUE;
+</span></span><span class="line"><span class="cl">    return oldTab;
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// Java7
+</span></span><span class="line"><span class="cl">if (oldCapacity == MAXIMUM_CAPACITY) { 
+</span></span><span class="line"><span class="cl">    threshold = Integer.MAX_VALUE;
+</span></span><span class="line"><span class="cl">    return;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在<code>HashMap</code>中有一个概念叫<code>loadFactor</code>，即负载因子，它表示<code>HashMap</code>满的程度，默认值为<code>0.75f</code>，也就是说默认情况下，当<code>HashMap</code>中元素个数达到了容量的3/4的时候就会进行自动扩容。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>为什么负载因子默认设置为0.75？</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * The load factor used when none specified in constructor.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">DEFAULT_LOAD_FACTOR</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">75f</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>在<a href="https://docs.oracle.com/javase/6/docs/api/java/util/HashMap.html">JDK的官方文档</a>中解释如下：</p>
+<blockquote>
+<p>As a general rule, the default load factor (.75) offers a good tradeoff between time and space costs.
+Higher values decrease the space overhead but increase the lookup cost (reflected in most of the operations of the HashMap class, including get and put).
+The expected number of entries in the map and its load factor should be taken into account when setting its initial capacity, so as to minimize the number of rehash operations.
+If the initial capacity is greater than the maximum number of entries divided by the load factor, no rehash operations will ever occur.</p>
+</blockquote>
+<p>文档大意：一般来说，默认的负载因子(0.75)在时间和空间成本之间提供了很好的权衡。
+更高的值减少了空间开销，但增加了查找成本(反映在<code>HashMap</code>类的大多数操作中，包括<code>get</code>和<code>put</code>)。
+在设置映射的初始容量时，应该考虑映射中预期的条目数及其负载因子，以便最小化重哈希操作的数量。如果初始容量大于最大条目数除以负载因子，则不会发生重新散列操作。</p>
+<p>负载因子和<code>HashMap</code>中的扩容有关，当<code>HashMap</code>中的元素大于临界值（<code>threshold = loadFactor * capacity</code>）就会扩容。
+所以负载因子的大小决定了什么时机扩容，扩容又影响到了hash碰撞的频率，所以设置一个合理的负载因子可以有效的避免<code>hash</code>碰撞。</p>
+<p>设置为0.75的其他解释：</p>
+<ul>
+<li>根据数学公式推算，这个值在<code>log(2)</code>的时候比较合理；</li>
+<li>为了提升扩容效率，<code>HashMap</code>的容量有一个固定的要求，那就是一定是2的幂。如果负载因子是3/4的话，那么和容量的乘积结果就可以是一个整数；</li>
+</ul>
+<h4 id="17扩容">1.7扩容</h4>
+<p>扩容步骤：</p>
+<ol>
+<li>当插入新的键值对使得元素数量超过阈值时，<code>HashMap</code>会进行扩容；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">addEntry</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">bucketIndex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//size：The number of key-value mappings contained in this map.  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//threshold：The next size value at which to resize (capacity * load factor)  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//数组扩容条件：1.已经存在的key-value mappings的个数大于等于阈值  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//             2.底层数组的bucketIndex坐标处不等于null  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="kc">null</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">table</span><span class="o">[</span><span class="n">bucketIndex</span><span class="o">]</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">(</span><span class="n">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">table</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="c1">//扩容之后，数组长度变了  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hash</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kc">null</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">hash</span><span class="p">(</span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="c1">//为什么要再次计算一下hash值呢？  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bucketIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">indexFor</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">table</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="c1">//扩容之后，数组长度变了，在数组的下标跟数组长度有关，得重算。  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">createEntry</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="n">bucketIndex</span><span class="p">);</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w"> 
+</span></span></span></code></pre></div></li>
+<li>创建一个新的数组，新的容量是原来的两倍，新阈值=新容量*负载因子；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">resize</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">   </span><span class="c1">//传入新的容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">oldTable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">    </span><span class="c1">//引用扩容前的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldTable</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  </span><span class="c1">//扩容前的数组大小如果已经达到最大(2^30)了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w"> </span><span class="c1">//修改阈值为int的最大值(2^31-1)，这样以后就不会扩容了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">newTable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Entry</span><span class="o">[</span><span class="n">newCapacity</span><span class="o">]</span><span class="p">;</span><span class="w">  </span><span class="c1">//初始化一个新的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">transfer</span><span class="p">(</span><span class="n">newTable</span><span class="p">);</span><span class="w">                         </span><span class="c1">//！！将数据转移到新的Entry数组里</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">table</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="p">;</span><span class="w">                           </span><span class="c1">//HashMap的table属性引用新的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">);</span><span class="c1">//修改阈值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>将旧表中的所有元素重新计算哈希值，并放入新表中：通过<code>transfer</code>方法将旧数组上的元素转移到扩容后的新数组上。遍历旧表中的每个桶，对于每个桶中的每个节点，重新计算它们在新表中的索引位置，将节点放入新表的相应位置；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">transfer</span><span class="p">(</span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">newTable</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">src</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">                   </span><span class="c1">//src引用了旧的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">src</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">//遍历旧的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">src</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">             </span><span class="c1">//取得旧Entry数组的每个元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">src</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="c1">//释放旧Entry数组的对象引用（for循环后，旧的Entry数组不再引用任何对象）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">indexFor</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="p">,</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">);</span><span class="w"> </span><span class="c1">//！！重新计算每个元素在数组中的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">//标记[1]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">newTable</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">      </span><span class="c1">//将元素放在数组上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">             </span><span class="c1">//访问下一个Entry链上的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>将旧表引用指向新表；</li>
+</ol>
+<h4 id="18扩容">1.8扩容</h4>
+<p>Java1.8的<code>HashMap</code>扩容原理与1.7类似，但有一些重要改进。
+在1.8时做了一些优化，文档注释写的很清楚：&ldquo;元素的位置要么是在原位置，要么是在原位置再移动<strong>2次幂的位置</strong>&quot;。也就是对比1.7的迁移到新的数组上省去了重新计算<code>hash</code>值的时间。</p>
+<p>这里的&quot;2次幂的位置&quot;是指长度为原来数组元素两倍的位置。
+假设旧容量是16，那么其二进制表示是<code>10000</code>，扩容后的新容量是32，其二进制表示是<code>100000</code>。<code>HashMap</code>通过<code>h &amp; (length - 1)</code>计算索引。
+在扩容之前，容量为16，根据公式<code>hash &amp; (oldCapacity - 1)</code>计算，因为<code>oldCapacity - 1</code>的二进制是<code>0000 1111</code>，那么计算索引时使用的是哈希值的低四位。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">扩容之前的位置：
+</span></span><span class="line"><span class="cl">  0101 0101
+</span></span><span class="line"><span class="cl">&amp; 0000 1111
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0000 0101
+</span></span></code></pre></div><p>扩容后，新的索引还是通过<code>hash &amp; (newCapacity - 1)</code>计算的，若容量为32，因为<code>newCapacity - 1</code>的二进制是<code>0001 1111</code>，那么计算索引时使用的是哈希值的低五位。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">扩容之后的位置：
+</span></span><span class="line"><span class="cl">  0101 0101
+</span></span><span class="line"><span class="cl">&amp; 0001 1111
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0001 0101
+</span></span></code></pre></div><p>扩容后，新的索引位置只受到哈希值高位的影响，所以叫高位优化。
+高位优化的关键在于，如果一个哈希值在旧容量下的索引是<code>index</code>，那么在新容量下，这个哈希值要么在<code>index</code>位置，要么在<code>index + oldCapacity</code>位置。
+例如上面的例子，容量为16，扩容之前的位置为<code>0000 0101</code>即5，扩容之后的位置为<code>0001 0101</code>即21（16+5）。
+通过这种高位优化技术，Java1.8中的<code>HashMap</code>在扩容时无需重新计算所有元素的哈希值，只需根据哈希值的高位来判断元素的新位置，所以提高了扩容的效率。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Initializes or doubles table size.  If null, allocates in
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * accord with initial capacity target held in field threshold.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Otherwise, because we are using power-of-two expansion, the
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * elements from each bin must either stay at same index, or move
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * with a power of two offset in the new table.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return the table
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="nf">resize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">oldTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">oldTab</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">oldTab</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">threshold</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newCap</span><span class="p">,</span><span class="w"> </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">oldTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCap</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                     </span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldThr</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// double threshold</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldThr</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="c1">// initial capacity was placed in threshold</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldThr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">               </span><span class="c1">// zero initial threshold signifies using defaults</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)(</span><span class="n">DEFAULT_LOAD_FACTOR</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newThr</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">float</span><span class="w"> </span><span class="n">ft</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="n">newCap</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">newCap</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">ft</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">?</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                      </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">ft</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newThr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">({</span><span class="s">&#34;rawtypes&#34;</span><span class="p">,</span><span class="s">&#34;unchecked&#34;</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">newTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">[</span><span class="n">newCap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">table</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldTab</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">oldCap</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">oldTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 单个节点，直接移动到新表中的新位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">newTab</span><span class="o">[</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">newCap</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 红黑树节点，处理红黑树的拆分逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">((</span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">e</span><span class="p">).</span><span class="na">split</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">newTab</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="p">,</span><span class="w"> </span><span class="n">oldCap</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// preserve order</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 处理链表节点，使用高位优化技术重新分配节点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">loHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">loTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hiHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">hiTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                           </span><span class="c1">// 判断节点在新表中的位置，高位优化的关键</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">oldCap</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                               </span><span class="c1">// 保持在原位置（低位链表）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">loHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">loTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">loTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                               </span><span class="c1">// 移动到新位置（高位链表）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">hiTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">hiHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">hiTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">hiTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 将低位链表和高位链表分别放入新表中的相应位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loTail</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">loTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">newTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">loHead</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">hiTail</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">hiTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">newTab</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">oldCap</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hiHead</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">newTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="线程安全">线程安全</h3>
+<p><code>HashMap</code>是线程不安全的集合类。因为<code>HashMap</code>中的方法大多没有同步，这意味着如果一个线程在遍历<code>HashMap</code>的同时，另一个线程修改了<code>HashMap</code>，例如添加或删除元素，可能会导致<code>ConcurrentModificationException</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="n">Object</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">(),</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">map</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>更严重的是，当多个线程中的<code>HashMap</code>同时扩容时，再使用<code>put</code>方法添加元素，如果<code>hash</code>值相同，可能出现同时在同一数组下用链表表示，造成闭环，导致在<code>get</code>时会出现死循环，CPU飙升到100%。</p>
+<p>在大多数并发场景中，推荐使用<code>ConcurrentHashMap</code>，因为它设计用于高并发环境，并且在大多数情况下性能优于使用同步包装或手动同步的<code>HashMap</code>。
+<code>ConcurrentHashMap</code>是Java中的一种线程安全的哈希表实现，用来替代传统的<code>HashMap</code>，来解决在多线程环境中并发修改带来的问题。
+与<code>Hashtable</code>不同，<code>ConcurrentHashMap</code>不对整个表进行全局加锁。相反它只对具体操作涉及的部分进行加锁，减少了线程之间的竞争。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConcurrentHashMapExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ConcurrentHashMap</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentHashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;One&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Two&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Value for key 1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">keySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Key: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Value: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="参考文章">参考文章</h2>
+<ul>
+<li><a href="https://blog.csdn.net/u010841296/article/details/82832166">https://blog.csdn.net/u010841296/article/details/82832166</a></li>
+<li><a href="https://blog.csdn.net/Elliot_Elliot/article/details/115610387">https://blog.csdn.net/Elliot_Elliot/article/details/115610387</a></li>
+<li><a href="https://blog.csdn.net/pange1991/article/details/82347284">https://blog.csdn.net/pange1991/article/details/82347284</a></li>
+<li><a href="https://blog.csdn.net/xiewenfeng520/article/details/107119970">https://blog.csdn.net/xiewenfeng520/article/details/107119970</a></li>
+<li><a href="https://zhuanlan.zhihu.com/p/114363420">https://zhuanlan.zhihu.com/p/114363420</a></li>
+<li><a href="https://www.yuque.com/renyong-jmovm/kb/vso1h5">https://www.yuque.com/renyong-jmovm/kb/vso1h5</a></li>
+<li><a href="https://juejin.cn/post/6844903554264596487">https://juejin.cn/post/6844903554264596487</a></li>
+<li><a href="http://hollischuang.gitee.io/tobetopjavaer/#/basics/java-basic/hashmap-init-capacity">http://hollischuang.gitee.io/tobetopjavaer/#/basics/java-basic/hashmap-init-capacity</a></li>
+</ul>
+</div>
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+                                        <a href="https://whiteppure.github.io/iblog/tags/%E9%9B%86%E5%90%88/">集合</a>
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diff --git a/docs/posts/detailed/java-mq/index.html b/docs/posts/detailed/java-mq/index.html
new file mode 100644
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+	<title>Kafka详解 ｜ 脚踏实地</title>
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+    <meta name="description" content="概览 MQ 即 messagequeue 消息队列，是分布式系统的重要组件，主要解决异步消息，应用解耦，消峰等问题。从而实现高可用，高性能，可伸缩和最终一致性的架构。使用较多的MQ有：acti" />
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+    
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+
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+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
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+        
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+        
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%a7%88">
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mq%e4%bc%98%e7%82%b9">
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+            
+            <li class="nav-item">
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+                    MQ缺点
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+                <a class="nav-link text-left" href="#%e5%b8%b8%e8%a7%81mq%e5%af%b9%e6%af%94">
+                    常见MQ对比
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+            </li>
+            
+            
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+        
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+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85%e6%95%b0%e6%8d%ae%e5%8f%af%e9%9d%a0%e6%80%a7%e4%bf%9d%e8%af%81">
+                    生产者数据可靠性保证
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
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+            
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+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85%e6%95%b0%e6%8d%ae%e4%b8%80%e8%87%b4%e6%80%a7%e4%bf%9d%e8%af%81">
+                    生产者数据一致性保证
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85ack%e6%9c%ba%e5%88%b6">
+                    生产者ack机制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#exactlyonce">
+                    ExactlyOnce
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
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+            
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+                <a class="nav-link text-left" href="#%e7%94%9f%e4%ba%a7%e8%80%85%e5%8f%91%e9%80%81%e6%b6%88%e6%81%af%e6%b5%81%e7%a8%8b">
+                    生产者发送消息流程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b6%88%e8%b4%b9%e8%80%85">
+                    消费者
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
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+                <a class="nav-link text-left" href="#%e6%b6%88%e8%b4%b9%e8%80%85%e5%88%86%e5%8c%ba%e5%88%86%e9%85%8d%e7%ad%96%e7%95%a5">
+                    消费者分区分配策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+                <a class="nav-link text-left" href="#%e6%b6%88%e8%b4%b9%e8%80%85%e6%b6%88%e8%b4%b9%e6%95%b0%e6%8d%ae%e9%97%ae%e9%a2%98">
+                    消费者消费数据问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+                <a class="nav-link text-left" href="#kafka%e4%ba%8b%e5%8a%a1">
+                    kafka事务
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
+        
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+                <a class="nav-link text-left" href="#%e6%b6%88%e6%81%af%e7%a7%af%e5%8e%8b">
+                    消息积压
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
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+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
+                
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+
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+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
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+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Kafka详解</h2>
+                        <span id="post_page_title_date" class="date">2021.10.19</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>MQ 即 messagequeue 消息队列，是分布式系统的重要组件，主要解决异步消息，应用解耦，消峰等问题。从而实现高可用，高性能，可伸缩和最终一致性的架构。使用较多的MQ有：activeMQ，rabbitMQ，kafka，metaMQ。</p>
+<h2 id="mq优点">MQ优点</h2>
+<ul>
+<li><strong>异步消息处理</strong>：可以将一些非核心流程，如日志，短信，邮件等，通过MQ的方式异步去处理。这样做的好处是缩短主流程的响应时间，提升用户体验；</li>
+<li><strong>应用解耦合</strong>：商品服务和订单服务之间。用户下单后，订单服务会通知商品服务。不使用MQ的情况是订单服务调用商品服务的接口，这样订单服务和商品服务之间是耦合的；使用MQ，订单服务完成持久化处理，将消息写入MQ消息队列中，返回用户订单下单成功，商品服务来订阅这个下单的消息，采用拉或推的方式获得下单信息，商品服务根据商品下单信息进行商品库存信息修改，这样当下单时商品服务不可用时，也不影响正常下单，这就完成了订单服务和商品服务之间的解耦；</li>
+<li><strong>流量消峰</strong>：秒杀活动流量过大，导致流量暴增，最终可能导致应用挂掉。一般会在应用前端加入消息队列来控制活动人数，假如消息队列超过最大数量，应该直接抛弃用户请求或者跳转到错误页面。秒杀业务根据消息队列中的请求信息在做后续的业务处理。比如在抢购时，可能一下子过来了10万个请求，但MQ只接受前100个用户的请求，超过100个不接收了。这样就成功限制了用户请求；</li>
+</ul>
+<h2 id="mq缺点">MQ缺点</h2>
+<ul>
+<li>系统可用性降低: 系统引入的外部依赖越多，越容易挂掉;</li>
+<li>系统复杂度提高: 加个 MQ 进来，你怎么保证消息没有重复消费？怎么处理消息丢失的情况？怎么保证消息传递的顺序性？头大头大，问题一大堆，痛苦不已;</li>
+<li>一致性问题: A 系统处理完了直接返回成功了，人都以为你这个请求就成功了；但是问题是，要是 BCD 三个系统那里，BD 两个系统写库成功了，结果 C 系统写库失败了，你这数据就不一致了;</li>
+</ul>
+<h2 id="常见mq对比">常见MQ对比</h2>
+<table>
+<thead>
+<tr>
+<th>特性</th>
+<th>ActiveMQ</th>
+<th>RabbitMQ</th>
+<th>RocketMQ</th>
+<th>Kafka</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>单机吞吐量</td>
+<td>万级，比 RocketMQ、Kafka 低一个数量级</td>
+<td>同 ActiveMQ</td>
+<td>10 万级，支撑高吞吐</td>
+<td>10 万级，高吞吐，一般配合大数据类的系统来进行实时数据计算、日志采集等场景</td>
+</tr>
+<tr>
+<td>topic 数量对吞吐量的影响</td>
+<td></td>
+<td></td>
+<td>topic 可以达到几百/几千的级别，吞吐量会有较小幅度的下降，这是 RocketMQ 的一大优势，在同等机器下，可以支撑大量的 topic</td>
+<td>topic 从几十到几百个时候，吞吐量会大幅度下降，在同等机器下，Kafka 尽量保证 topic 数量不要过多，如果要支撑大规模的 topic，需要增加更多的机器资源</td>
+</tr>
+<tr>
+<td>时效性</td>
+<td>ms 级</td>
+<td>微秒级，这是 RabbitMQ 的一大特点，延迟最低</td>
+<td>ms 级</td>
+<td>延迟在 ms 级以内</td>
+</tr>
+<tr>
+<td>可用性</td>
+<td>高，基于主从架构实现高可用</td>
+<td>同 ActiveMQ</td>
+<td>非常高，分布式架构</td>
+<td>非常高，分布式，一个数据多个副本，少数机器宕机，不会丢失数据，不会导致不可用</td>
+</tr>
+<tr>
+<td>消息可靠性</td>
+<td>有较低的概率丢失数据</td>
+<td>基本不丢</td>
+<td>经过参数优化配置，可以做到 0 丢失</td>
+<td>同 RocketMQ</td>
+</tr>
+<tr>
+<td>功能支持</td>
+<td>MQ 领域的功能极其完备</td>
+<td>基于 erlang 开发，并发能力很强，性能极好，延时很低</td>
+<td>MQ 功能较为完善，还是分布式的，扩展性好</td>
+<td>功能较为简单，主要支持简单的 MQ 功能，在大数据领域的实时计算以及日志采集被大规模使用</td>
+</tr>
+</tbody>
+</table>
+<p>一般的业务系统要引入 MQ，最早大家都用 ActiveMQ，但是现在确实大家用的不多了，没经过大规模吞吐量场景的验证，社区也不是很活跃，所以大家还是算了吧，我个人不推荐用这个了。</p>
+<p>后来大家开始用 RabbitMQ，但是确实 erlang 语言阻止了大量的 Java 工程师去深入研究和掌控它，对公司而言，几乎处于不可控的状态，但是确实人家是开源的，比较稳定的支持，活跃度也高。</p>
+<p>不过现在确实越来越多的公司会去用 RocketMQ，确实很不错，毕竟是阿里出品，但社区可能有突然黄掉的风险,目前 RocketMQ 已捐给 Apache，但 GitHub 上的活跃度其实不算高,对自己公司技术实力有绝对自信的，推荐用 RocketMQ，否则回去老老实实用 RabbitMQ 吧，人家有活跃的开源社区，绝对不会黄。</p>
+<p>所以中小型公司，技术实力较为一般，技术挑战不是特别高，用 RabbitMQ 是不错的选择；大型公司，基础架构研发实力较强，用 RocketMQ 是很好的选择。</p>
+<p>如果是大数据领域的实时计算、日志采集等场景，用 Kafka 是业内标准的，绝对没问题，社区活跃度很高，绝对不会黄，何况几乎是全世界这个领域的事实性规范。</p>
+<h2 id="jms消息模型">JMS消息模型</h2>
+<p>JMS即JavaMessageService，Java消息服务应用程序接口，是一个Java平台中关于面向消息中间件的API，用于在两个应用程序之间，或分布式系统中发送消息，进行异步通信。</p>
+<p>JMS是基于JVM的消息代理规范，ActiveMQ、HornetMQ等是JMS的实现。</p>
+<p>Java消息服务是一个与具体平台无关的API，绝大多数MOM提供商都对JMS提供支持。我们可以简单的理解：两个应用程序之间需要进行通信，我们使用一个JMS服务，进行中间的转发，通过JMS的使用，我们可以解除两个程序之间的耦合。</p>
+<h3 id="点对点模式">点对点模式</h3>
+<p>消息发送者发送消息，消息代理将其放入消息队列中，消息接受者从队列中获取消息，消息读取后被移除消息队列。每个消息都被发送到一个特定的队列，接收者从队列中获取消息。队列保留着消息，直到它们被消费或超时。</p>
+<p><img alt="MQ详解-001" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-001.png"></p>
+<p>虽然可能有多个客户端在队列中侦听消息，但只有一个可以读取到消息，之后消息将不存在，其他消费者将无法读取。也就是说消息队列只有唯一一个发送者和<em>接受者</em>，但是并不能说只有一个<em>接收者</em>。</p>
+<p>特点：</p>
+<ul>
+<li>每个消息只有一个消费者，即消息一旦被消费，消息就不在消息队列中；</li>
+<li>发送者和接收者之间在时间上没有依赖性，也就是说当发送者发送了消息之后，不管接收者有没有正在运行，它不会影响到消息被发送到队列；</li>
+<li>接收者在成功接收消息之后需向队列应答成功；</li>
+</ul>
+<h3 id="发布订阅模式">发布订阅模式</h3>
+<p>发布者将消息发送到主题Topic中，多个订阅者订阅这个主题，订阅者不断的去轮询监听消息队列中的消息，那么就会在消息到达的同时接收消息。</p>
+<p><img alt="MQ详解-002" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-002.png"></p>
+<p>特点：</p>
+<ul>
+<li>每个消息可以有多个消费者，消费完消息之后消息不会清除；</li>
+<li>发布者和订阅者之间有时间上的依赖性：针对某个主题(Topic)的订阅者，它必须创建一个订阅之后，才能消费发布者的消息，而且为了消费消息，订阅者必须保持运行的状态。当然，为了缓和这种严格的时间相关性，JMS允许订阅者创建一个可持久化的订阅。这样即使订阅者没有运行，它也能接收到发布者的消息；</li>
+</ul>
+<h2 id="kafka">kafka</h2>
+<p>kafka是一个分布式的基于发布/订阅模式的消息队列，主要应用于大数据实时处理领域。</p>
+<h3 id="基础架构">基础架构</h3>
+<p><img alt="MQ详解-003" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-003.png"></p>
+<ul>
+<li>Producer：消息生产者，向kafka推送消息；</li>
+<li>Consumer：消息消费者，向kafka中broker获取消息的客户端；</li>
+<li>Topic：主题，可以理解为一个队列，生产者和消费者面向的都是一个topic；</li>
+<li>Broker：经纪人，一台kafka服务器就是一个broker。一个集群由多个broker组成。一个broker可以容纳多个topic；</li>
+<li>Partition：分区，为了实现扩展性，一个非常大的topic可以分布到多个服务器上，一个主题可以分为多个分区，每个分区是一个有序的队列；</li>
+<li>ConsumerGroup：消费者组，由多个消费者组成。消费者组内每个消费者负责消费不同分区的数据，一个分区只能由一个消费者组内的一个消费者消费；消费者组之间互不影响。所有的消费者都属于某个消费者组，即消费者组是逻辑上的一个订阅者；</li>
+<li>Replica：副本，为保证集群中的某个节点发生故障时，该节点上的分区数据不丢失，且kafka仍然能够继续工作，kafka提供了副本机制，一个topic的每个分区都有若干个副本，一个leader和若干个follower；</li>
+<li>Leader：每个分区多个副本的“主”，生产者发送数据的对象，以及消费者消费数据的对象都是leader。leader是针对topic的，而不是broker的，即不同的kafka服务区中会出现同一个leader；</li>
+<li>Follower：每个分区多个副本中的“从”，实时从leader中同步数据，保持和leader数据的同步。leader发生故障时，某个Follower会成为新的leader；</li>
+<li>Controller：Kafka 集群中有一个broker会被选举为Controller，负责管理集群broker的上下线，所有topic的分区副本分配和leader选举等工作，Controller的管理工作都是依赖于Zookeeper的；</li>
+</ul>
+<p>消费者组的作用为了提高消费能力，即提高并发。</p>
+<p>解耦合是消息队列作用之一，当消费者宕机后，再次启动的时候会继续消费消息，而不是从头消费消息。因为这个特性所以消费者会保存一些消费的进度信息，被称为offset，保存的位置在kafka0.9之前保存在zookpeer当中，在此之后保存在kafka本地。即最终kafka会将消息保存在本地磁盘中，默认保留168个小时，即7天。</p>
+<p>kafka中消息是以topic进行分类的，producer生产消息，consumer消费消息，都是面向topic的。topic是逻辑上的概念，而partition是物理上的概念，每个partition对应于一个log文件，该log文件中存储的就是producer生产的数据。</p>
+<p>Producer生产的数据会被不断追加到该log文件末端，且每条数据都有自己的offset。consumer组中的每个consumer，都会实时记录自己消费到了哪个offset，以便出错恢复时，从上次的位置继续消费。</p>
+<h3 id="发布订阅工作流程">发布订阅工作流程</h3>
+<p><img alt="MQ详解-004" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-004.png"></p>
+<ol>
+<li>生产者定期向主题发送消息；</li>
+<li>kafka代理将所有消息存储在为特定主题配置的分区中。它确保消息在分区之间平均共享。如果生产者发送了两个消息，并且有两个分区，kafka将在第一个分区中存储一个消息，在第二个分区中存储第二个消息；</li>
+<li>消费者订阅主题后，kafka将向消费者提供该主题的当前偏移量，并将偏移量保存在Zookeeper集合中；</li>
+<li>消费者将定期向kafka请求新消息,一旦kafka从生产者那里收到消息，它将把这些消息转发给消费者，消费者将收到消息并进行处理；</li>
+<li>消息处理后，消费者将向kafka代理发送确认；</li>
+<li>一旦kafka收到确认，它将偏移量更改为新值并在Zookeeper中对其进行更新。由于在Zookeeper中保留了偏移量，因此即使在服务器出现故障时，使用者也可以正确读取下一条消息；</li>
+<li>4、5、6步骤流程将重复进行，直到消费者停止请求为止；</li>
+</ol>
+<p>消费者可以选择随时倒退或跳至所需的主题偏移量并阅读所有后续消息。</p>
+<h3 id="生产者">生产者</h3>
+<h4 id="生产者文件存储">生产者文件存储</h4>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.jianshu.com/p/3e54a5a39683">https://www.jianshu.com/p/3e54a5a39683</a></li>
+</ul>
+<p><img alt="MQ详解-005" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-005.png"></p>
+<p>由于生产者生产的消息会不断追加到log文件末尾，为防止log文件过大导致数据定位效率低下，kafka采取了分片和索引机制，将每个partition分为多个segment。
+每个segment对应两个文件：“.index”文件和“.log”文件。这些文件位于一个文件夹下，该文件夹的命名规则为：topic名称+分区序号。例如，first这个topic有三个分区，则其对应的文件夹为 first-0,first-1,first-2。其中，每个segment中的日志数据文件大小均相等。</p>
+<blockquote>
+<p>该日志数据文件的大小可以通过在kafka Broker的config/server.properties配置文件的中的“log.segment.bytes”进行设置，默认为1G大小（1073741824字节），在顺序写入消息时如果超出该设定的阈值，将会创建一组新的日志数据和索引文件。</p>
+</blockquote>
+<p>“.index”文件存储大量的索引信息，“.log”文件存储大量的数据，索引文件中的元数据指向对应数据文件中message的物理偏移地址。其中文件的命名是以第一个数据的偏移量来命名的。</p>
+<p><strong>kafka如何通过index文件快速找到log文件中的数据？</strong></p>
+<p>根据指定的偏移量，使用二分法查询定位出该偏移量对应的消息所在的分段索引文件和日志数据文件。然后通过二分查找法，继续查找出小于等于指定偏移量的最大偏移量，同时也得出了对应的position即实际物理位置。</p>
+<p>根据该物理位置在分段的日志数据文件中顺序扫描查找偏移量与指定偏移量相等的消息。由于index文件中的每条对应log文件中存储内容大小都相同，所以想要找到指定的消息，只需要用index文件中的该条的大小加上该条的偏移量即可得出log文件中指定消息的位置。</p>
+<p><img alt="MQ详解-006" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-006.png"></p>
+<h4 id="生产者分区策略">生产者分区策略</h4>
+<p>分区的原因：</p>
+<ul>
+<li>方便在集群中扩展，每个Partition可以通过调整以适应它所在的机器，而一个topic又可以有多个Partition组成，因此整个集群就可以适应适合的数据了；</li>
+<li>可以提高并发，因为可以以Partition为单位读写了，每个partition在不同的服务区上；</li>
+</ul>
+<p><img alt="MQ详解-007" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-007.png"></p>
+<ul>
+<li>在指明partition的情况下，直接将指明的值直接作为partiton值；</li>
+<li>在没有指明partition值但有key的情况下，将key的hash 值与topic的partition数进行取余得到partition值；</li>
+<li>既没有partition值又没有key值的情况下，第一次调用时随机生成一个整数（后面每次调用在这个整数上自增），将这个值与topic可用的partition总数取余得到partition值，也就是常说的round-robin算法；</li>
+</ul>
+<h4 id="生产者数据可靠性保证">生产者数据可靠性保证</h4>
+<p>为保证 producer 发送的数据，能可靠的发送到指定的 topic，topic 的每个 partition 收到 producer 发送的数据后，都需要向 producer 发送 ack(acknowledgement 确认收到)，如果 producer 收到 ack，就会进行下一轮的发送，否则重新发送数据。</p>
+<p><img alt="MQ详解-008" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-008.png"></p>
+<table>
+<thead>
+<tr>
+<th>方案</th>
+<th>优点</th>
+<th>缺点</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>半数以上完成同步，就发 送 ack</td>
+<td>延迟低</td>
+<td>选举新的 leader 时，容忍 n 台 节点的故障，需要 2n+1 个副本</td>
+</tr>
+<tr>
+<td>全部完成同步，才发送ack</td>
+<td>选举新的 leader 时，容忍 n 台 节点的故障，需要 n+1 个副 本</td>
+<td>延迟高</td>
+</tr>
+</tbody>
+</table>
+<blockquote>
+<p>理解 2n+1：
+半数以上完成同步才可以发ACK，如果挂了n台有副本的服务器，那么就需要有另外n台正常发送（这样正常发送的刚好是总数（挂的和没挂的）的一半（n（挂的）+n（正常的）=2n））,因为是半数以上所以2n+1.(所以总数2n+1的时候最多只能容忍n台有故障)</p>
+<p>即，如果挂了n台有副本的服务器，那么存在副本的服务器的总和为 2n+1</p>
+</blockquote>
+<p>kafka选择了第二种方案，原因如下:
+1.同样为了容忍 n 台节点的故障，第一种方案需要 2n+1 个副本，而第二种方案只需要 n+1 个副本，而 kafka 的每个分区都有大量的数据，第一种方案会造成大量数据的冗余；
+2.虽然第二种方案的网络延迟会比较高，但网络延迟对 kafka 的影响较小；</p>
+<p>采用第二种方案之后，设想以下情景： leader 收到数据，所有 follower 都开始同步数据，但有一个 follower，因为某种故障，迟迟不能与 leader 进行同步，那 leader 就要一直等下去，直到它完成同步，才能发送 ack。这个问题怎么解决呢？</p>
+<p>Leader 维护了一个动态的 in-sync replica set 即ISR。</p>
+<p>当和 leader 保持同步的 follower 集合。当 ISR 中的 follower 完成数据的同步之后，就会给 leader 发送 ack。如果 follower长时间未向leader同步数据，则该follower将被踢出ISR，该时间阈值由replica.lag.time.max.ms参数设定。 Leader 发生故障之后，就会从 ISR 中选举新的 leader。</p>
+<blockquote>
+<p>kafka是通过消息条数差值(replica.lag.time.max.messages) 加 通信时间长短(同步时间replica.lag.time.max.ms) 两个条件来选副本进ISR，在高版本中不再关注副本的消息条数最大条件。</p>
+</blockquote>
+<p>为何会去掉消息条数差值参数？</p>
+<p>因为kafka一般是按batch批量发数据到leader, 如果批量条数12条，replica.lag.time.max.messages参数设置是10条，那么当一个批次消息发到kafka leader，此时，ISR中就要踢掉所有的follower，很快follower同步完所有数据后，follower又要被加入到ISR，而且要加入到zookeeper中频繁操作，所以去除掉该条件。</p>
+<h4 id="生产者数据一致性保证">生产者数据一致性保证</h4>
+<p><img alt="MQ详解-009" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-009.png"></p>
+<ul>
+<li>
+<p>LEO：（Log End offset）每个副本的最后一个offset；</p>
+</li>
+<li>
+<p>HW：（High Watermark）高水位，指的是消费者能见到的最大的 offset， ISR 队列中最小的 LEO；</p>
+</li>
+<li>
+<p>follower 故障：follower 发生故障后会被临时踢出 ISR，待该 follower 恢复后， follower 会读取本地磁盘记录的上次的 HW，并将 log 文件高于 HW 的部分截取掉，从 HW 开始向 leader 进行同步。等该 follower 的 LEO 大于等于该 Partition 的 HW，即 follower 追上 leader 之后，就可以重新加入 ISR 了。</p>
+</li>
+<li>
+<p>leader 故障：leader 发生故障之后，会从 ISR 中选出一个新的 leader，之后，为保证多个副本之间的数据一致性， 其余的 follower 会先将各自的 log 文件高于 HW 的部分截掉，然后从新的 leader同步数据；如果少于 leader 中的数据则会从 leader 中进行同步。</p>
+</li>
+</ul>
+<h4 id="生产者ack机制">生产者ack机制</h4>
+<p>对于某些不太重要的数据，对数据的可靠性要求不是很高，能够容忍数据的少量丢失，所以没必要等 ISR 中的 follower 全部接收成功。kafka为生产者提供了三种ack可靠性级别配置：</p>
+<ul>
+<li>0：producer 不等待 broker 的 ack，这一操作提供了一个最低的延迟，broker 一接收到还没有写入磁盘就已经返回，当 broker 故障时有可能丢失数据；</li>
+<li>1： producer 等待 broker 的 ack， partition 的 leader 落盘成功后返回 ack，如果在 follower同步成功之前 leader 故障，那么将会丢失数据；</li>
+<li>-1/all：producer 等待 broker 的 ack， ISR队列中 partition 的 leader 和 ISR 的follower 全部落盘成功后才返回 ack。但是如果在 follower 同步完成后，broker 发送 ack 之前， leader 发生故障，那么会造成数据重复；</li>
+</ul>
+<h4 id="exactlyonce">ExactlyOnce</h4>
+<p>将服务器的 ACK 级别设置为-1，可以保证 Producer 到 Server 之间不会丢失数据，即 At Least Once 语义，至少发送一次；相对的，将服务器 ACK 级别设置为 0，可以保证生产者每条消息只会被发送一次，即 At Most Once 语义，至多发送一次。</p>
+<p>至少发送一次可以保证数据不丢失，但是不能保证数据不重复；相对的，至多发送一次可以保证数据不重复，但是不能保证数据不丢失。 但是，对于一些非常重要的信息，比如说交易数据，下游数据消费者要求数据既不重复也不丢失，即 Exactly Once 语义，准确发送一次。</p>
+<p>在0.11 版本的 Kafka，引入了一项重大特性：幂等性。所谓的幂等性就是指生产者不论向 Server 发送多少次重复数据， Server 端都只会持久化一条。幂等性结合 At Least Once 语义，就构成了 Kafka 的 Exactly Once 语义。</p>
+<p>要启用幂等性，只需要将 Producer 的参数中 <code>enable.idempotence</code> 设置为 true 即可。</p>
+<p>Kafka的幂等性实现其实就是将原来下游需要做的去重放在了数据上游。开启幂等性的 Producer 在初始化的时候会被分配一个 PID，发往同一 Partition 的消息会附带 Sequence Number。而Broker 端会对&lt;PID, Partition, SeqNumber&gt;做缓存，当具有相同主键的消息提交时， Broker 只会持久化一条。但是 PID 重启就会变化，同时不同的 Partition 也具有不同主键，所以幂等性无法保证跨分区跨会话的 Exactly Once。</p>
+<h4 id="生产者发送消息流程">生产者发送消息流程</h4>
+<p>kafka的生产者发送消息采用的是异步发送的方式。在消息发送的过程中，涉及到了两个线程——main 线程和 Sender 线程，以及一个线程共享变量——RecordAccumulator。</p>
+<p><img alt="MQ详解-010" src="/iblog/posts/annex/images/essays/MQ%E8%AF%A6%E8%A7%A3-010.png"></p>
+<p>在生产者发送消息时，main线程将消息发送给 RecordAccumulator，当数据积累到 batch.size 之后，sender线程才会不断从 RecordAccumulator 中拉取消息发送到 kafka的broker；如果数据迟迟未达到 batch.size，sender 线程等待 linger.time 之后就会发送数据。</p>
+<h3 id="消费者">消费者</h3>
+<h4 id="消费者分区分配策略">消费者分区分配策略</h4>
+<p>一个消费者组中有多个消费者，一个主题有多个分区，所以必然会涉及到分区的分配问题，即确定哪个分区由哪个消费者来消费。</p>
+<p>消费分配策略：</p>
+<ul>
+<li>round-robin：会采用轮询的方式将当前所有的分区依次分配给所有的消费者；</li>
+<li>range：首先会计算每个消费者可以消费的分区个数，然后按照顺序将指定个数范围的分区分配给各个消费者；</li>
+<li>sticky：这种分区策略是最新版本中新增的一种策略，将现有的分区尽可能均衡的分配给各个消费者，存在此目的的原因在于Round-Robin和Range分配策略实际上都会导致某几个消费者承载过多的分区，从而导致消费压力不均衡；</li>
+</ul>
+<p>轮询就不必说了，就是把分区按照hash排序，然后分配。range按范围分配，先将所有的分区放到一起然后排序，按照平均分配的方式计算每个消费者会得到多少个分区，如果没有除尽，则会将多出来的分区依次计算到前面几个消费者。
+比如这里是三个分区和两个消费者，那么每个消费者至少会得到1个分区，而3除以2后还余1，那么就会将多余的部分依次算到前面几个消费者，也就是这里的1会分配给第一个消费者，</p>
+<p>如果按照Range分区方式进行分配，其本质上是依次遍历每个topic，然后将这些topic的分区按照其所订阅的消费者数量进行平均的范围分配。这种方式从计算原理上就会导致排序在前面的消费者分配到更多的分区，从而导致各个消费者的压力不均衡。</p>
+<h4 id="消费者消费数据问题">消费者消费数据问题</h4>
+<p>消费者在消费的时候，需要维护一个offset，用于记录消费的位置，当offset提交时会有两个问题：重复消费和漏消费：</p>
+<ul>
+<li>当提交的offset小于当前程序处理的最后一条消息的offset,会造成重复消费。情景：先消费，后提交offset,如果消费成功、提交失败，消费者下次获取的offset还是以前的，所以会造成重复消费。</li>
+<li>当提交的offset大于当前程序处理的最后一条消息的offset,会造成漏消费。情景：先提交offset，后消费,如果提交成功、消费失败，消费者下次获取的offset已经是新的，所以会造成漏消费。</li>
+</ul>
+<p>这里就需要注意offset的提交方式，offset默认是自动提交，当然这会造成消费的不准确。offset提交方式：</p>
+<ul>
+<li>异步提交当前offset；</li>
+<li>同步提交当前offset；</li>
+<li>同步和异步组合提交；</li>
+<li>提交指定的offset；</li>
+</ul>
+<p>建议将offset保存在数据库中，使当前业务与offset提交绑定起来，这样可以一定程度避免重复消费问题，重复消费的问题，一方面需要消息中间件来进行保证。另一方面需要自己的处理逻辑来保证消息的幂等性。</p>
+<h3 id="kafka事务">kafka事务</h3>
+<p>kafka从0.11版本开始引入了事务支持。事务可以保证kafka在<a href="/iblog/posts/detailed/java-mq/#exactlyonce">Exactly Once</a>语义的基础上，生产和消费可以跨分区和会话，要么全部成功，要么全部失败。</p>
+<ul>
+<li>生产者：为了实现跨分区跨会话的事务，需要引入一个全局唯一的事务ID，并将生产者获得的PID和事务ID绑定。这样当生产者重启后就可以通过正在进行的事务ID获得原来的PID，进而保证精准发送一次；</li>
+</ul>
+<blockquote>
+<p>为了管理 Transaction， Kafka 引入了一个新的组件 Transaction Coordinator。 Producer 就是通过和 Transaction Coordinator 交互获得 Transaction ID 对应的任务状态。 Transaction Coordinator 还负责将事务所有写入 Kafka 的一个内部 Topic，这样即使整个服务重启，由于事务状态得到保存，进行中的事务状态可以得到恢复，从而继续进行。</p>
+</blockquote>
+<ul>
+<li>消费者：对于消费者而言，事务的保证就会相对较弱，尤其时无法保证提交的信息被精确消费。这是由于消费者可以通过offset访问任意信息，而且不同的<a href="/iblog/posts/detailed/java-mq/#文件存储">Segment File</a>生命周期不同，同一事务的消息可能会出现重启后被删除的情况；</li>
+</ul>
+<h3 id="消息积压">消息积压</h3>
+<p>如果线上遇到大量消息积压,那就是线上故障了.最可能是消费者出现故障</p>
+<p>一般这个时候，只能临时紧急扩容了:</p>
+<ul>
+<li>先修复消费者的问题，确保其恢复消费速度，然后将现有消费者都停掉</li>
+<li>新建一个 topic，partition 是原来的 10 倍，临时建立好原先 10 倍的 queue 数量;</li>
+<li>然后写一个临时的分发数据的 consumer 程序，这个程序部署上去消费积压的数据，消费之后不做耗时的处理，直接均匀轮询写入临时建立好的 10 倍数量的 queue;</li>
+<li>接着临时征用 10 倍的机器来部署 consumer，每一批 consumer 消费一个临时 queue 的数据。这种做法相当于是临时将 queue 资源和 consumer 资源扩大 10 倍，以正常的 10 倍速度来消费数据;</li>
+<li>等快速消费完积压数据之后，得恢复原先部署的架构，重新用原先的 consumer 机器来消费消息;</li>
+</ul>
+<p>如果没有消费者没有出现问题,而出现了消费积压的情况可以参考以下思路:</p>
+<ul>
+<li>提高消费并行度</li>
+<li>批量方式消费</li>
+<li>跳过非重要方式消费</li>
+<li>优化消息消费业务处理过程,简化过程</li>
+</ul>
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+        <ul class="nav">
+            
+        <ul class="nav">
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+                <a class="nav-link text-left" href="#netty">
+                    Netty
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+            
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+        
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+                    概述
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+        
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+                    线程模型演变
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+                <a class="nav-link text-left" href="#%e4%bc%a0%e7%bb%9f-io-%e6%a8%a1%e5%9e%8b">
+                    传统 IO 模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+        
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#reactor-%e6%a8%a1%e5%9e%8b">
+                    Reactor 模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+        
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#netty-%e6%a8%a1%e5%9e%8b">
+                    Netty 模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+                    简单使用
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+            </li>
+            
+            
+        </ul>
+        
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+                    任务队列
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+            </li>
+            
+            
+        </ul>
+        
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+                    异步模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#netty%e6%90%ad%e5%bb%bahttp%e6%9c%8d%e5%8a%a1">
+                    Netty搭建Http服务
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+                    TCP粘包、拆包及解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
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+                        <h2 id="post_single_title">Netty详解</h2>
+                        <span id="post_page_title_date" class="date">2021.04.09</span>
+                        
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+                    <div class="post_content markdown"><h2 id="netty">Netty</h2>
+<p>参考文章：https://dongzl.github.io/netty-handbook/#/</p>
+<h3 id="概述">概述</h3>
+<blockquote>
+<p><a href="https://netty.io">Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers &amp; clients.</a></p>
+</blockquote>
+<ol>
+<li>Netty 是一个异步的、基于事件驱动的网络应用框架，用以快速开发高性能、高可靠性的网络 IO 程序。</li>
+<li>Netty 主要针对在 TCP 协议下，面向 Client 端的高并发应用，或者 Peer-to-Peer 场景下的大量数据持续传输的应用。</li>
+<li>Netty 本质是一个 NIO 框架，适用于服务器通讯相关的多种应用场景。</li>
+<li>Netty 是由 JBoss 提供的一个 Java 开源框架，现为 Github 上的独立项目。</li>
+</ol>
+<h3 id="线程模型演变">线程模型演变</h3>
+<p>目前存在的线程模型有：</p>
+<ul>
+<li>传统阻塞 I/O 服务模型</li>
+<li>Reactor 模式
+<ul>
+<li>单 Reactor 单线程</li>
+<li>单 Reactor 多线程</li>
+<li>主从 Reactor多线程</li>
+</ul>
+</li>
+</ul>
+<p>Netty 主要基于主从 Reactor 多线程模型做了一定的改进。</p>
+<h4 id="传统-io-模型">传统 IO 模型</h4>
+<p><img alt="传统IO模型" src="/iblog/posts/annex/images/essays/%E4%BC%A0%E7%BB%9FIO%E6%A8%A1%E5%9E%8B.png"></p>
+<p>采用阻塞 IO 模式获取输入的数据，每个连接都需要独立的线程完成数据的输入，业务处理，数据返回。
+当并发数很大，就会创建大量的线程，占用很大系统资源，连接创建后，如果当前线程暂时没有数据可读，该线程会阻塞在 read 操作，造成线程资源浪费。</p>
+<h4 id="reactor-模型">Reactor 模型</h4>
+<p>基于 I/O 复用模型，多个连接共用一个阻塞对象，应用程序只需要在一个阻塞对象等待，无需阻塞等待所有连接。 当某个连接有新的数据可以处理时，操作系统通知应用程序，线程从阻塞状态返回，开始进行业务处理。</p>
+<p><img alt="Reactor模式" src="/iblog/posts/annex/images/essays/Reactor%E6%A8%A1%E5%BC%8F.png"></p>
+<p>为了避免浪费可以创建一个线程池，当客户端发起请求时，通过<code>DispatcherHandler</code>进行分发请求处理到线程池，线程池中在使用具体的线程进行事件处理。 服务器端程序处理传入的多个请求,并将它们同步分派到相应的处理线程，因此 Reactor 模式也叫 Dispatcher 模式。</p>
+<p>Reactor 模式使用 IO 复用监听事件，收到事件后，分发给某个线程（进程），这点就是网络服务器高并发处理关键。</p>
+<h5 id="单-reactor-单线程">单 Reactor 单线程</h5>
+<p><img alt="单Reactor单线程" src="/iblog/posts/annex/images/essays/%E5%8D%95Reactor%E5%8D%95%E7%BA%BF%E7%A8%8B.png"></p>
+<p>步骤：</p>
+<ul>
+<li>Reactor 对象通过 Select 监控客户端请求事件，收到事件后通过 Dispatch 进行分发</li>
+<li>如果是建立连接请求事件，则由 Acceptor 通过 Accept 处理连接请求，然后创建一个 Handler 对象处理连接完成后的后续业务处理</li>
+<li>如果不是建立连接事件，则 Reactor 会分发调用连接对应的 Handler 来响应</li>
+<li>Handler 会完成 <code>Read → 业务处理 → Send</code> 的完整业务流程</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>性能问题，只有一个线程，无法完全发挥多核 CPU 的性能</li>
+<li>如果线程意外终止，或者进入死循环，会导致整个系统通信模块不可用，不能接收和处理外部消息</li>
+</ul>
+<p>优点：</p>
+<ul>
+<li>模型简单，没有多线程、进程通信、竞争的问题，全部都在一个线程中完成</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>客户端的数量有限，业务处理非常快速的情况</li>
+</ul>
+<h5 id="单-reactor-多线程">单 Reactor 多线程</h5>
+<p><img alt="单Reactor多线程" src="/iblog/posts/annex/images/essays/%E5%8D%95Reactor%E5%A4%9A%E7%BA%BF%E7%A8%8B.png"></p>
+<p>步骤：</p>
+<ul>
+<li>Reactor 对象通过对 select 监听请求事件，收到请求事件后交给 dispath 进行转发</li>
+<li>如果是建立连接请求，则通过 accept 处理连接请求，然后创建一个handler对象处理完成连接后的事件</li>
+<li>如果不是建立连接请求，则直接交给 handler 对象</li>
+<li>handler 只负责响应事件，不做具体的业务处理，通过 read 读取完后，分发给下面的 worker线程池中某个线程处理</li>
+<li>worker 线程负责处理具体业务，处理完成后会将具体的结果返回给 handler</li>
+<li>handler 线程通过send方法返回给客户端</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>多线程访问比较复杂，需要处理线程之间的竞争，资源共享</li>
+<li>Reactor 对象在处理所有事件的监听和响应都是单线程的，在高并发场景容易出现性能瓶颈</li>
+</ul>
+<p>优点：</p>
+<ul>
+<li>可以充分利用CPU资源</li>
+</ul>
+<h5 id="主从-reactor-多线程">主从 Reactor 多线程</h5>
+<p><img alt="主从Reactor线程" src="/iblog/posts/annex/images/essays/%E4%B8%BB%E4%BB%8EReactor%E7%BA%BF%E7%A8%8B.png"></p>
+<p>Reactor 主线程可以对应多个 Reactor 子线程，即 MainRecator 可以关联多个 SubReactor，从而解决了Reactor 在单线程中运行，高并发场景下容易成为性能瓶颈。
+步骤：</p>
+<ul>
+<li>Reactor 主线程 MainReactor 对象通过 select 监听连接事件，收到事件后，通过 Acceptor 处理连接事件</li>
+<li>当 Acceptor 处理连接事件后，MainReactor 将连接分配给 SubReactor</li>
+<li>SubReactor 将连接加入到连接队列进行监听，并创建 handler 进行各种事件处理</li>
+<li>当有新事件发生时，SubReactor 就会调用对应的 handler 处理</li>
+<li>handler 只负责响应事件，不做具体的业务处理，通过 read 读取完后，分发给下面的 worker线程池中某个线程处理</li>
+<li>worker 线程负责处理具体业务，处理完成后会将具体的结果返回给 handler</li>
+<li>handler 线程通过send方法返回给客户端</li>
+</ul>
+<p>优点：</p>
+<ul>
+<li>父线程与子线程的数据交互简单，Reactor 主线程只需要把新连接传给子线程，子线程无需返回数据</li>
+<li>父线程与子线程的数据交互简单职责明确，父线程只需要接收新连接，子线程完成后续的业务处理</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>编程复杂度较高</li>
+</ul>
+<p>这种模型在许多项目中广泛使用，包括 Nginx 主从 Reactor 多进程模型，Memcached 主从多线程，Netty 主从多线程模型的支持。</p>
+<h4 id="netty-模型">Netty 模型</h4>
+<p><img alt="Netty模型" src="/iblog/posts/annex/images/essays/Netty%E6%A8%A1%E5%9E%8B.png"></p>
+<p><img alt="netty结构" src="/iblog/posts/annex/images/essays/netty%E7%BB%93%E6%9E%84.png"></p>
+<ul>
+<li>Netty 抽象出两组线程池 <code>BossGroup</code> 专门负责接收客户端的连接，<code>WorkerGroup</code> 专门负责网络的读写；<code>BossGroup</code> 和 <code>WorkerGroup</code> 类型都是 <code>NioEventLoopGroup</code></li>
+<li><code>NioEventLoopGroup</code> 相当于一个事件循环组，这个组中含有多个事件循环，每一个事件循环是 <code>NioEventLoop</code>，每个 <code>NioEventLoop</code> 都有一个 <code>Selector</code>，用于监听绑定在其上的 <code>socket</code> 的网络通讯</li>
+<li><code>NioEventLoopGroup</code> 可指定多个 <code>NioEventLoop</code></li>
+<li>每个 <code>BossNioEventLoop</code> 循环执行的步骤
+<ul>
+<li>轮询 accept 事件</li>
+<li>处理 <code>accept</code> 事件，与 client 建立连接，生成 <code>NioSocketChannel</code>，并将其注册到某个 <code>workerNioEventLoop</code> 上的 <code>Selector</code></li>
+<li>处理任务队列的任务，即 <code>runAllTasks</code></li>
+</ul>
+</li>
+<li>每个 <code>WorkerNioEventLoop</code> 循环执行的步骤
+<ul>
+<li>轮询 <code>read，write</code> 事件</li>
+<li>处理 I/O 事件，即 <code>read，write</code> 事件，在对应 <code>NioSocketChannel</code> 处理</li>
+<li>处理任务队列的任务，即 <code>runAllTasks</code></li>
+</ul>
+</li>
+<li>每个 <code>WorkerNioEventLoop</code> 处理业务时，会使用 <code>pipeline</code>（管道），<code>pipeline</code> 中包含了 <code>channel</code>(通道)，即通过 <code>pipeline</code> 可以获取到对应通道，管道中维护了很多的处理器</li>
+</ul>
+<h3 id="简单使用">简单使用</h3>
+<p>1.<a href="https://netty.io/downloads.html">导入依赖</a></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">&lt;dependency&gt;
+</span></span><span class="line"><span class="cl">    &lt;groupId&gt;io.netty&lt;/groupId&gt;
+</span></span><span class="line"><span class="cl">    &lt;artifactId&gt;netty-all&lt;/artifactId&gt;
+</span></span><span class="line"><span class="cl">    &lt;version&gt;4.1.36.Final&lt;/version&gt;
+</span></span><span class="line"><span class="cl">&lt;/dependency&gt;
+</span></span><span class="line"><span class="cl">&lt;dependency&gt;
+</span></span><span class="line"><span class="cl">    &lt;groupId&gt;org.projectlombok&lt;/groupId&gt;
+</span></span><span class="line"><span class="cl">    &lt;artifactId&gt;lombok&lt;/artifactId&gt;
+</span></span><span class="line"><span class="cl">&lt;/dependency&gt;
+</span></span></code></pre></div><p>2.服务器端代码演示</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">/**
+</span></span><span class="line"><span class="cl"> * netty 服务端测试
+</span></span><span class="line"><span class="cl"> */
+</span></span><span class="line"><span class="cl">public class MainTestServer {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        // 启动器， 负责组装netty组件 启动服务器
+</span></span><span class="line"><span class="cl">        new ServerBootstrap()
+</span></span><span class="line"><span class="cl">                // BossEventLoop WorkEventLoop 每个 EventLoop 就是 一个选择器 + 一个线程
+</span></span><span class="line"><span class="cl">                .group(new NioEventLoopGroup())
+</span></span><span class="line"><span class="cl">                // 选择服务器 ServerSocketChannel 具体实现
+</span></span><span class="line"><span class="cl">                .channel(NioServerSocketChannel.class)
+</span></span><span class="line"><span class="cl">                // 决定了 workEventLoop 能做那些操作
+</span></span><span class="line"><span class="cl">                .childHandler(
+</span></span><span class="line"><span class="cl">                        // 建立连接后会被调用； 作用： 初始化 + 添加其他的 handler
+</span></span><span class="line"><span class="cl">                        new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">                    // 当客户端请求发过来时 才会调用
+</span></span><span class="line"><span class="cl">                    @Override 
+</span></span><span class="line"><span class="cl">                    protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(new StringDecoder());
+</span></span><span class="line"><span class="cl">                        // 自定义handler 
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(new ChannelInboundHandlerAdapter() {
+</span></span><span class="line"><span class="cl">                            @Override
+</span></span><span class="line"><span class="cl">                            public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
+</span></span><span class="line"><span class="cl">                                System.out.println(&#34;服务器端接收数据：&#34; + msg);
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">                        });
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                })
+</span></span><span class="line"><span class="cl">                // 绑定监听端口
+</span></span><span class="line"><span class="cl">                .bind(8090);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>3.客户端代码演示</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">/**
+</span></span><span class="line"><span class="cl"> * netty 客户端测试
+</span></span><span class="line"><span class="cl"> */
+</span></span><span class="line"><span class="cl">public class MainTestClient {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) throws InterruptedException {
+</span></span><span class="line"><span class="cl">        new Bootstrap()
+</span></span><span class="line"><span class="cl">                .group(new NioEventLoopGroup())
+</span></span><span class="line"><span class="cl">                .channel(NioSocketChannel.class)
+</span></span><span class="line"><span class="cl">                .handler(new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">                    // 初始化 在与服务器建立链接的时候 调用
+</span></span><span class="line"><span class="cl">                    @Override
+</span></span><span class="line"><span class="cl">                    protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                        // 添加编码器 只有当向服务端发送请求数据时 才会执行
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(new StringEncoder());
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                })
+</span></span><span class="line"><span class="cl">                .connect(new InetSocketAddress(&#34;127.0.0.1&#34;, 8090))
+</span></span><span class="line"><span class="cl">                //阻塞方法，直到与服务器端连接建立
+</span></span><span class="line"><span class="cl">                .sync()
+</span></span><span class="line"><span class="cl">                .channel()
+</span></span><span class="line"><span class="cl">                // 向服务器端发送数据
+</span></span><span class="line"><span class="cl">                .writeAndFlush(&#34;hello word&#34;);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="任务队列">任务队列</h3>
+<ul>
+<li>用户程序自定义的普通任务</li>
+<li>用户自定义定时任务</li>
+<li>非当前 Reactor 线程调用 Channel 的各种方法 例如在推送系统的业务线程里面，根据用户的标识，找到对应的 Channel 引用，然后调用 Write 类方法向该用户推送消息，就会进入到这种场景。
+最终的 Write 会提交到任务队列中后被异步消费</li>
+</ul>
+<p>客户端</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">/**
+</span></span><span class="line"><span class="cl"> * netty 客户端测试
+</span></span><span class="line"><span class="cl"> */
+</span></span><span class="line"><span class="cl">public class MainTestClient {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) throws InterruptedException {
+</span></span><span class="line"><span class="cl">        new Bootstrap()
+</span></span><span class="line"><span class="cl">                .group(new NioEventLoopGroup())
+</span></span><span class="line"><span class="cl">                .channel(NioSocketChannel.class)
+</span></span><span class="line"><span class="cl">                .handler(new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                    // 初始化 在与服务器建立链接的时候 调用
+</span></span><span class="line"><span class="cl">                    @Override
+</span></span><span class="line"><span class="cl">                    protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                        // 添加编码器 只有当向服务端发送请求数据时 才会执行
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(&#34;decoder&#34;, new StringDecoder());
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(&#34;encoder&#34;, new StringEncoder());
+</span></span><span class="line"><span class="cl">                        channel.pipeline().addLast(new ChannelInboundHandlerAdapter(){
+</span></span><span class="line"><span class="cl">                            @Override
+</span></span><span class="line"><span class="cl">                            public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
+</span></span><span class="line"><span class="cl">                                System.out.println(&#34;服务端响应数据：&#34; + msg);
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                            @Override
+</span></span><span class="line"><span class="cl">                            public void channelActive(ChannelHandlerContext ctx) throws Exception {
+</span></span><span class="line"><span class="cl">                                System.out.println(&#34;客户端Active .....&#34;);
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                            /**
+</span></span><span class="line"><span class="cl">                             * 客户端异常时触发
+</span></span><span class="line"><span class="cl">                             */
+</span></span><span class="line"><span class="cl">                            @Override
+</span></span><span class="line"><span class="cl">                            public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
+</span></span><span class="line"><span class="cl">                                cause.printStackTrace();
+</span></span><span class="line"><span class="cl">                                ctx.close();
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                        });
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                })
+</span></span><span class="line"><span class="cl">                .connect(new InetSocketAddress(&#34;127.0.0.1&#34;, 8090))
+</span></span><span class="line"><span class="cl">                //阻塞方法，直到与服务器端连接建立
+</span></span><span class="line"><span class="cl">                .sync()
+</span></span><span class="line"><span class="cl">                .channel()
+</span></span><span class="line"><span class="cl">                // 向服务器端发送数据
+</span></span><span class="line"><span class="cl">                .writeAndFlush(&#34;hello word&#34;);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>服务端</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">/**
+</span></span><span class="line"><span class="cl"> * netty 服务端测试
+</span></span><span class="line"><span class="cl"> */
+</span></span><span class="line"><span class="cl">public class MainTestServer {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        //new 一个主线程组
+</span></span><span class="line"><span class="cl">        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
+</span></span><span class="line"><span class="cl">        //new 一个工作线程组
+</span></span><span class="line"><span class="cl">        EventLoopGroup workGroup = new NioEventLoopGroup(200);
+</span></span><span class="line"><span class="cl">        // 启动器， 负责组装netty组件 启动服务器
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            ServerBootstrap serverBootstrap = new ServerBootstrap()
+</span></span><span class="line"><span class="cl">                    // BossEventLoop WorkEventLoop 每个 EventLoop 就是 一个选择器 + 一个线程
+</span></span><span class="line"><span class="cl">                    .group(bossGroup, workGroup)
+</span></span><span class="line"><span class="cl">                    // 选择服务器 ServerSocketChannel 具体实现
+</span></span><span class="line"><span class="cl">                    .channel(NioServerSocketChannel.class)
+</span></span><span class="line"><span class="cl">                    //设置队列大小
+</span></span><span class="line"><span class="cl">                    .option(ChannelOption.SO_BACKLOG, 1024)
+</span></span><span class="line"><span class="cl">                    // 两小时内没有数据的通信时,TCP会自动发送一个活动探测数据报文
+</span></span><span class="line"><span class="cl">                    .childOption(ChannelOption.SO_KEEPALIVE, true)
+</span></span><span class="line"><span class="cl">                    // 决定了 workEventLoop 能做那些操作
+</span></span><span class="line"><span class="cl">                    .childHandler(
+</span></span><span class="line"><span class="cl">                            // 建立连接后会被调用； 作用： 初始化 + 添加其他的 handler
+</span></span><span class="line"><span class="cl">                            new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">                                // 当客户端请求发过来时 才会调用
+</span></span><span class="line"><span class="cl">                                @Override
+</span></span><span class="line"><span class="cl">                                protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(&#34;decoder&#34;, new StringDecoder(CharsetUtil.UTF_8));
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(&#34;encoder&#34;, new StringEncoder(CharsetUtil.UTF_8));
+</span></span><span class="line"><span class="cl">                                    // 自定义handler
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(new ChannelInboundHandlerAdapter() {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                        /**
+</span></span><span class="line"><span class="cl">                                         * 客户端连接会触发
+</span></span><span class="line"><span class="cl">                                         */
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
+</span></span><span class="line"><span class="cl">                                            System.out.println(&#34;服务端 Active......&#34;);
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                        /**
+</span></span><span class="line"><span class="cl">                                         * 客户端发消息会触发
+</span></span><span class="line"><span class="cl">                                         */
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
+</span></span><span class="line"><span class="cl">                                            System.out.println(&#34;服务器收到消息: &#34; + msg.toString());
+</span></span><span class="line"><span class="cl">                                            // 比如这里我们有一个非常耗时长的业务-&gt; 应该一步执行 -&gt; 提交该对应的channel
+</span></span><span class="line"><span class="cl">                                            // 将任务放在 taskQueue 中
+</span></span><span class="line"><span class="cl">                                            ctx.channel().eventLoop().execute(() -&gt; {
+</span></span><span class="line"><span class="cl">                                                try {
+</span></span><span class="line"><span class="cl">                                                    Thread.sleep(10 * 1000);
+</span></span><span class="line"><span class="cl">                                                    ctx.writeAndFlush(&#34;业务1处理完成&#34;);
+</span></span><span class="line"><span class="cl">                                                } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">                                                    e.printStackTrace();
+</span></span><span class="line"><span class="cl">                                                }
+</span></span><span class="line"><span class="cl">                                            });
+</span></span><span class="line"><span class="cl">                                            // 放在TaskQueue 中的任务是由一个线程来进行处理的 所以执行完上一个任务才会执行下一个任务 时间是累加的
+</span></span><span class="line"><span class="cl">                                            ctx.channel().eventLoop().execute(() -&gt; {
+</span></span><span class="line"><span class="cl">                                                try {
+</span></span><span class="line"><span class="cl">                                                    Thread.sleep(20 * 1000);
+</span></span><span class="line"><span class="cl">                                                    ctx.writeAndFlush(&#34;业务2处理完成&#34;);
+</span></span><span class="line"><span class="cl">                                                } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">                                                    e.printStackTrace();
+</span></span><span class="line"><span class="cl">                                                }
+</span></span><span class="line"><span class="cl">                                            });
+</span></span><span class="line"><span class="cl">                                             // 用户自定义定时任务 -》 该任务是提交到 scheduleTaskQueue中
+</span></span><span class="line"><span class="cl">                                        
+</span></span><span class="line"><span class="cl">                                            ctx.channel().eventLoop().schedule(new Runnable() {
+</span></span><span class="line"><span class="cl">                                                @Override
+</span></span><span class="line"><span class="cl">                                                public void run() {
+</span></span><span class="line"><span class="cl">                                    
+</span></span><span class="line"><span class="cl">                                                    try {
+</span></span><span class="line"><span class="cl">                                                        Thread.sleep(5 * 1000);
+</span></span><span class="line"><span class="cl">                                                        ctx.writeAndFlush(Unpooled.copiedBuffer(&#34;hello, 客户端~(&gt;^ω^&lt;)喵4&#34;, CharsetUtil.UTF_8));
+</span></span><span class="line"><span class="cl">                                                        System.out.println(&#34;channel code=&#34; + ctx.channel().hashCode());
+</span></span><span class="line"><span class="cl">                                                    } catch (Exception ex) {
+</span></span><span class="line"><span class="cl">                                                        System.out.println(&#34;发生异常&#34; + ex.getMessage());
+</span></span><span class="line"><span class="cl">                                                    }
+</span></span><span class="line"><span class="cl">                                                }
+</span></span><span class="line"><span class="cl">                                            }, 5, TimeUnit.SECONDS);
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                        /**
+</span></span><span class="line"><span class="cl">                                         * 给客户端发送消息
+</span></span><span class="line"><span class="cl">                                         */
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
+</span></span><span class="line"><span class="cl">                                            ctx.writeAndFlush(&#34;over&#34;);
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                        /**
+</span></span><span class="line"><span class="cl">                                         * 发生异常触发
+</span></span><span class="line"><span class="cl">                                         */
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
+</span></span><span class="line"><span class="cl">                                            cause.printStackTrace();
+</span></span><span class="line"><span class="cl">                                            ctx.close();
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                    });
+</span></span><span class="line"><span class="cl">                                }
+</span></span><span class="line"><span class="cl">                            });
+</span></span><span class="line"><span class="cl">                    // 绑定监听端口
+</span></span><span class="line"><span class="cl">            ChannelFuture future = serverBootstrap.bind(8090).sync();
+</span></span><span class="line"><span class="cl">            // 对关闭通道进行监听
+</span></span><span class="line"><span class="cl">            future.channel().closeFuture().sync();
+</span></span><span class="line"><span class="cl">        } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        } finally {
+</span></span><span class="line"><span class="cl">            //关闭主线程组
+</span></span><span class="line"><span class="cl">            bossGroup.shutdownGracefully();
+</span></span><span class="line"><span class="cl">            //关闭工作线程组
+</span></span><span class="line"><span class="cl">            workGroup.shutdownGracefully();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="异步模型">异步模型</h3>
+<p>异步的概念和同步相对。当一个异步过程调用发出后，调用者不能立刻得到结果。实际处理这个调用的组件在完成后，通过状态、通知和回调来通知调用者。</p>
+<p><code>Netty</code> 中的 I/O 操作是异步的，包括 <code>Bind、Write、Connect</code> 等操作会简单的返回一个 <code>ChannelFuture</code>。 调用者并不能立刻获得结果，而是通过 <code>Future-Listener</code> 机制，用户可以方便的主动获取或者通过通知机制获得 IO 操作结果。</p>
+<p>当 <code>Future</code> 对象刚刚创建时，处于非完成状态，调用者可以通过返回的 <code>ChannelFuture</code> 来获取操作执行的状态，注册监听函数来执行完成后的操作。</p>
+<p>常见有如下操作：</p>
+<ul>
+<li>通过 <code>isDone</code> 方法来判断当前操作是否完成；</li>
+<li>通过 <code>isSuccess</code> 方法来判断已完成的当前操作是否成功；</li>
+<li>通过 <code>getCause</code> 方法来获取已完成的当前操作失败的原因；</li>
+<li>通过 <code>isCancelled</code> 方法来判断已完成的当前操作是否被取消；</li>
+<li>通过 <code>addListener</code> 方法来注册监听器，当操作已完成（isDone方法返回完成），将会通知指定的监听器；如果 <code>Future</code> 对象已完成，则通知指定的监听器</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">//绑定一个端口并且同步,生成了一个ChannelFuture对象
+</span></span><span class="line"><span class="cl">//启动服务器(并绑定端口)
+</span></span><span class="line"><span class="cl">ChannelFuture cf = bootstrap.bind(6668).sync();
+</span></span><span class="line"><span class="cl">//给cf注册监听器，监控我们关心的事件
+</span></span><span class="line"><span class="cl">cf.addListener(new ChannelFutureListener() {
+</span></span><span class="line"><span class="cl">   @Override
+</span></span><span class="line"><span class="cl">   public void operationComplete (ChannelFuture future) throws Exception {
+</span></span><span class="line"><span class="cl">      if (cf.isSuccess()) {
+</span></span><span class="line"><span class="cl">         System.out.println(&#34;监听端口6668成功&#34;);
+</span></span><span class="line"><span class="cl">      } else {
+</span></span><span class="line"><span class="cl">         System.out.println(&#34;监听端口6668失败&#34;);
+</span></span><span class="line"><span class="cl">      }
+</span></span><span class="line"><span class="cl">   }
+</span></span><span class="line"><span class="cl">});
+</span></span></code></pre></div><h3 id="netty搭建http服务">Netty搭建Http服务</h3>
+<p>服务端</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MainTestServer {
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        //new 一个主线程组
+</span></span><span class="line"><span class="cl">        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
+</span></span><span class="line"><span class="cl">        //new 一个工作线程组
+</span></span><span class="line"><span class="cl">        EventLoopGroup workGroup = new NioEventLoopGroup(200);
+</span></span><span class="line"><span class="cl">        // 启动器， 负责组装netty组件 启动服务器
+</span></span><span class="line"><span class="cl">        try {
+</span></span><span class="line"><span class="cl">            ServerBootstrap serverBootstrap = new ServerBootstrap()
+</span></span><span class="line"><span class="cl">                    // BossEventLoop WorkEventLoop 每个 EventLoop 就是 一个选择器 + 一个线程
+</span></span><span class="line"><span class="cl">                    .group(bossGroup, workGroup)
+</span></span><span class="line"><span class="cl">                    // 选择服务器 ServerSocketChannel 具体实现
+</span></span><span class="line"><span class="cl">                    .channel(NioServerSocketChannel.class)
+</span></span><span class="line"><span class="cl">                    //设置队列大小
+</span></span><span class="line"><span class="cl">                    .option(ChannelOption.SO_BACKLOG, 1024)
+</span></span><span class="line"><span class="cl">                    // 两小时内没有数据的通信时,TCP会自动发送一个活动探测数据报文
+</span></span><span class="line"><span class="cl">                    .childOption(ChannelOption.SO_KEEPALIVE, true)
+</span></span><span class="line"><span class="cl">                    // 决定了 workEventLoop 能做那些操作
+</span></span><span class="line"><span class="cl">                    .childHandler(
+</span></span><span class="line"><span class="cl">                            // 建立连接后会被调用； 作用： 初始化 + 添加其他的 handler
+</span></span><span class="line"><span class="cl">                            new ChannelInitializer&lt;NioSocketChannel&gt;() {
+</span></span><span class="line"><span class="cl">                                // 当客户端请求发过来时 才会调用
+</span></span><span class="line"><span class="cl">                                @Override
+</span></span><span class="line"><span class="cl">                                protected void initChannel(NioSocketChannel channel) throws Exception {
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(&#34;MyHttpServerCodec&#34;, new HttpServerCodec());
+</span></span><span class="line"><span class="cl">                                    // 自定义handler
+</span></span><span class="line"><span class="cl">                                    channel.pipeline().addLast(new SimpleChannelInboundHandler&lt;HttpObject&gt;() {
+</span></span><span class="line"><span class="cl">                                        @Override
+</span></span><span class="line"><span class="cl">                                        protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {
+</span></span><span class="line"><span class="cl">                                            System.out.println(&#34;对应的channel=&#34; + ctx.channel() + &#34; pipeline=&#34; + ctx.pipeline() + &#34; 通过pipeline获取channel&#34; + ctx.pipeline().channel());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                            System.out.println(&#34;当前ctx的handler=&#34; + ctx.handler());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                            //判断 msg 是不是 httprequest请求
+</span></span><span class="line"><span class="cl">                                            if (msg instanceof HttpRequest) {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                System.out.println(&#34;ctx 类型=&#34; + ctx.getClass());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                System.out.println(&#34;pipeline hashcode&#34; + ctx.pipeline().hashCode() + &#34; TestHttpServerHandler hash=&#34; + this.hashCode());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                System.out.println(&#34;msg 类型=&#34; + msg.getClass());
+</span></span><span class="line"><span class="cl">                                                System.out.println(&#34;客户端地址&#34; + ctx.channel().remoteAddress());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                //获取到
+</span></span><span class="line"><span class="cl">                                                HttpRequest httpRequest = (HttpRequest) msg;
+</span></span><span class="line"><span class="cl">                                                //获取uri, 过滤指定的资源
+</span></span><span class="line"><span class="cl">                                                URI uri = new URI(httpRequest.uri());
+</span></span><span class="line"><span class="cl">                                                if (&#34;/favicon.ico&#34;.equals(uri.getPath())) {
+</span></span><span class="line"><span class="cl">                                                    System.out.println(&#34;请求了 favicon.ico, 不做响应&#34;);
+</span></span><span class="line"><span class="cl">                                                    return;
+</span></span><span class="line"><span class="cl">                                                }
+</span></span><span class="line"><span class="cl">                                                //回复信息给浏览器 [http协议]
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                ByteBuf content = Unpooled.copiedBuffer(&#34;hello, 我是服务器&#34;, CharsetUtil.UTF_8);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                //构造一个http的相应，即 httpresponse
+</span></span><span class="line"><span class="cl">                                                FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, content);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                response.headers().set(HttpHeaderNames.CONTENT_TYPE, &#34;text/plain&#34;);
+</span></span><span class="line"><span class="cl">                                                response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.readableBytes());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">                                                //将构建好 response返回
+</span></span><span class="line"><span class="cl">                                                ctx.writeAndFlush(response);
+</span></span><span class="line"><span class="cl">                                            }
+</span></span><span class="line"><span class="cl">                                        }
+</span></span><span class="line"><span class="cl">                                    });
+</span></span><span class="line"><span class="cl">                                }
+</span></span><span class="line"><span class="cl">                            });
+</span></span><span class="line"><span class="cl">                    // 绑定监听端口
+</span></span><span class="line"><span class="cl">            ChannelFuture future = serverBootstrap.bind(8090).sync();
+</span></span><span class="line"><span class="cl">            future.addListener( future1 -&gt; {
+</span></span><span class="line"><span class="cl">                if (future.isSuccess()) {
+</span></span><span class="line"><span class="cl">                    System.out.println(&#34;监听端口8090成功&#34;);
+</span></span><span class="line"><span class="cl">                }else{
+</span></span><span class="line"><span class="cl">                    System.out.println(&#34;监听端口8090失败&#34;);
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            });
+</span></span><span class="line"><span class="cl">            // 对关闭通道进行监听
+</span></span><span class="line"><span class="cl">            future.channel().closeFuture().sync();
+</span></span><span class="line"><span class="cl">        } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        } finally {
+</span></span><span class="line"><span class="cl">            //关闭主线程组
+</span></span><span class="line"><span class="cl">            bossGroup.shutdownGracefully();
+</span></span><span class="line"><span class="cl">            //关闭工作线程组
+</span></span><span class="line"><span class="cl">            workGroup.shutdownGracefully();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="tcp粘包拆包及解决方案">TCP粘包、拆包及解决方案</h3>
+<p>TCP 是面向连接的，面向流的，提供高可靠性服务。收发两端（客户端和服务器端）都要有一一成对的 socket，因此，发送端为了将多个发给接收端的包，更有效的发给对方，使用了优化方法（Nagle 算法），将多次间隔较小且数据量小的数据，合并成一个大的数据块，然后进行封包。这样做虽然提高了效率，但是接收端就难于分辨出完整的数据包了，由于 TCP 无消息保护边界,需要在接收端处理消息边界问题，也就是我们所说的粘包、拆包问题。</p>
+<p>拆包和粘包是在socket编程中经常出现的情况，在socket通讯过程中，如果通讯的一端一次性连续发送多条数据包，tcp协议会将多个数据包打包成一个tcp报文发送出去，这就是所谓的粘包。而如果通讯的一端发送的数据包超过一次tcp报文所能传输的最大值时，就会将一个数据包拆成多个最大tcp长度的tcp报文分开传输，这就叫做拆包。</p>
+<p>对于粘包的情况，要对粘在一起的包进行拆包。对于拆包的情况，要对被拆开的包进行粘包，即将一个被拆开的完整应用包再组合成一个完整包。比较通用的做法就是每次发送一个应用数据包前在前面加上四个字节的包长度值，指明这个应用包的真实长度。</p>
+<p>使用netty解决拆包、粘包问题代码示例：</p>
+<p>客户端代码</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="err">@</span><span class="n">SpringBootApplication</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyClientApplication</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="ne">String</span><span class="p">[]</span> <span class="n">args</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">SpringApplication</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">NettyClientApplication</span><span class="o">.</span><span class="k">class</span><span class="p">,</span> <span class="n">args</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Component</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">StartNetty</span> <span class="n">implements</span> <span class="n">CommandLineRunner</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="n">final</span> <span class="n">NettyClient</span> <span class="n">nettyClient</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">StartNetty</span><span class="p">(</span><span class="n">NettyClient</span> <span class="n">nettyClient</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">nettyClient</span> <span class="o">=</span> <span class="n">nettyClient</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">run</span><span class="p">(</span><span class="ne">String</span><span class="o">...</span> <span class="n">args</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;启动netty客户端 ...&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">nettyClient</span><span class="o">.</span><span class="n">start</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Component</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyClient</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="n">Netty客户端启动</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">start</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">EventLoopGroup</span> <span class="n">group</span> <span class="o">=</span> <span class="n">new</span> <span class="n">NioEventLoopGroup</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Bootstrap</span> <span class="n">bootstrap</span> <span class="o">=</span> <span class="n">new</span> <span class="n">Bootstrap</span><span class="p">()</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">group</span><span class="p">(</span><span class="n">group</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">//</span><span class="err">该参数的作用就是禁止使用</span><span class="n">Nagle算法</span><span class="err">，使用于小数据即时传输</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">option</span><span class="p">(</span><span class="n">ChannelOption</span><span class="o">.</span><span class="n">TCP_NODELAY</span><span class="p">,</span> <span class="bp">true</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">channel</span><span class="p">(</span><span class="n">NioSocketChannel</span><span class="o">.</span><span class="k">class</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">handler</span><span class="p">(</span><span class="n">new</span> <span class="n">NettyClientInitializer</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">try</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">ChannelFuture</span> <span class="n">future</span> <span class="o">=</span> <span class="n">bootstrap</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">&#34;127.0.0.1&#34;</span><span class="p">,</span> <span class="mi">9000</span><span class="p">)</span><span class="o">.</span><span class="n">sync</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">            <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;客户端成功....&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span><span class="err">发送消息</span>
+</span></span><span class="line"><span class="cl">            <span class="n">future</span><span class="o">.</span><span class="n">channel</span><span class="p">()</span><span class="o">.</span><span class="n">writeAndFlush</span><span class="p">(</span><span class="s2">&#34;客户端请求数据&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span> <span class="err">等待连接被关闭</span>
+</span></span><span class="line"><span class="cl">            <span class="n">future</span><span class="o">.</span><span class="n">channel</span><span class="p">()</span><span class="o">.</span><span class="n">closeFuture</span><span class="p">()</span><span class="o">.</span><span class="n">sync</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="n">catch</span> <span class="p">(</span><span class="n">InterruptedException</span> <span class="n">e</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">e</span><span class="o">.</span><span class="n">printStackTrace</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="n">finally</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">group</span><span class="o">.</span><span class="n">shutdownGracefully</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyClientInitializer</span> <span class="k">extends</span> <span class="n">ChannelInitializer</span><span class="o">&lt;</span><span class="n">SocketChannel</span><span class="o">&gt;</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">initChannel</span><span class="p">(</span><span class="n">SocketChannel</span> <span class="n">socketChannel</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="s2">&#34;decoder&#34;</span><span class="p">,</span> <span class="n">new</span> <span class="n">MyMessageDecoder</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="s2">&#34;encoder&#34;</span><span class="p">,</span> <span class="n">new</span> <span class="n">MyMessageEncoder</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="n">new</span> <span class="n">NettyClientHandler</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyClientHandler</span> <span class="k">extends</span> <span class="n">ChannelInboundHandlerAdapter</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelActive</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;客户端Active .....&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span> <span class="err">模拟</span><span class="n">tcp粘包</span>
+</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="p">(</span><span class="ne">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="mi">5</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="ne">String</span> <span class="n">mes</span> <span class="o">=</span> <span class="s2">&#34;今天天气冷，吃火锅&#34;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span> <span class="o">=</span> <span class="n">mes</span><span class="o">.</span><span class="n">getBytes</span><span class="p">(</span><span class="n">Charset</span><span class="o">.</span><span class="n">forName</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">            <span class="ne">int</span> <span class="n">length</span> <span class="o">=</span> <span class="n">mes</span><span class="o">.</span><span class="n">getBytes</span><span class="p">(</span><span class="n">Charset</span><span class="o">.</span><span class="n">forName</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">))</span><span class="o">.</span><span class="n">length</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="o">//</span>  <span class="err">解决</span><span class="n">tcp粘包问题</span>
+</span></span><span class="line"><span class="cl">            <span class="n">MessageProtocol</span> <span class="n">messageProtocol</span> <span class="o">=</span> <span class="n">new</span> <span class="n">MessageProtocol</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">            <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setLen</span><span class="p">(</span><span class="n">length</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setContent</span><span class="p">(</span><span class="n">content</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">            <span class="n">ctx</span><span class="o">.</span><span class="n">writeAndFlush</span><span class="p">(</span><span class="n">messageProtocol</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">收到服务端的消息</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelRead</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="ne">Object</span> <span class="n">msg</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;客户端收到消息: {}&#34;</span><span class="p">,</span> <span class="n">msg</span><span class="o">.</span><span class="n">toString</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">MessageProtocol</span> <span class="n">mp</span> <span class="o">=</span> <span class="p">(</span><span class="n">MessageProtocol</span><span class="p">)</span><span class="n">msg</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">int</span> <span class="n">len</span> <span class="o">=</span> <span class="n">mp</span><span class="o">.</span><span class="n">getLen</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span> <span class="o">=</span> <span class="n">mp</span><span class="o">.</span><span class="n">getContent</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;客户端接收到消息如下&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;长度=&#34;</span> <span class="o">+</span> <span class="n">len</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;内容=&#34;</span> <span class="o">+</span> <span class="n">new</span> <span class="ne">String</span><span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">StandardCharsets</span><span class="o">.</span><span class="n">UTF_8</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">客户端异常时触发</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">exceptionCaught</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">Throwable</span> <span class="n">cause</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">cause</span><span class="o">.</span><span class="n">printStackTrace</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ctx</span><span class="o">.</span><span class="n">close</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>服务端代码</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="err">@</span><span class="n">SpringBootApplication</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyServerApplication</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="ne">String</span><span class="p">[]</span> <span class="n">args</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">SpringApplication</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">NettyServerApplication</span><span class="o">.</span><span class="k">class</span><span class="p">,</span> <span class="n">args</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Component</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">StartNetty</span> <span class="n">implements</span> <span class="n">CommandLineRunner</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="n">final</span> <span class="n">NettyServer</span> <span class="n">nettyServer</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">StartNetty</span><span class="p">(</span><span class="n">NettyServer</span> <span class="n">nettyServer</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">nettyServer</span> <span class="o">=</span> <span class="n">nettyServer</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">启动</span><span class="n">netty</span> <span class="err">让</span><span class="n">netty随着项目一起启动</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">run</span><span class="p">(</span><span class="ne">String</span><span class="o">...</span> <span class="n">args</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;netty 服务端启动 ...&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">nettyServer</span><span class="o">.</span><span class="n">start</span><span class="p">(</span><span class="n">new</span> <span class="n">InetSocketAddress</span><span class="p">(</span><span class="s2">&#34;127.0.0.1&#34;</span><span class="p">,</span> <span class="mi">9000</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Component</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyServer</span>  <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="n">Netty服务启动</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">start</span><span class="p">(</span><span class="n">InetSocketAddress</span> <span class="n">socketAddress</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="n">new</span> <span class="err">一个主线程组</span>
+</span></span><span class="line"><span class="cl">        <span class="n">EventLoopGroup</span> <span class="n">bossGroup</span> <span class="o">=</span> <span class="n">new</span> <span class="n">NioEventLoopGroup</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="n">new</span> <span class="err">一个工作线程组</span>
+</span></span><span class="line"><span class="cl">        <span class="n">EventLoopGroup</span> <span class="n">workGroup</span> <span class="o">=</span> <span class="n">new</span> <span class="n">NioEventLoopGroup</span><span class="p">(</span><span class="mi">200</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">ServerBootstrap</span> <span class="n">bootstrap</span> <span class="o">=</span> <span class="n">new</span> <span class="n">ServerBootstrap</span><span class="p">()</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">group</span><span class="p">(</span><span class="n">bossGroup</span><span class="p">,</span> <span class="n">workGroup</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">channel</span><span class="p">(</span><span class="n">NioServerSocketChannel</span><span class="o">.</span><span class="k">class</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">childHandler</span><span class="p">(</span><span class="n">new</span> <span class="n">ServerChannelInitializer</span><span class="p">())</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">localAddress</span><span class="p">(</span><span class="n">socketAddress</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">//</span><span class="err">设置队列大小</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">option</span><span class="p">(</span><span class="n">ChannelOption</span><span class="o">.</span><span class="n">SO_BACKLOG</span><span class="p">,</span> <span class="mi">1024</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">                <span class="o">//</span> <span class="err">两小时内没有数据的通信时</span><span class="p">,</span><span class="n">TCP会自动发送一个活动探测数据报文</span>
+</span></span><span class="line"><span class="cl">                <span class="o">.</span><span class="n">childOption</span><span class="p">(</span><span class="n">ChannelOption</span><span class="o">.</span><span class="n">SO_KEEPALIVE</span><span class="p">,</span> <span class="bp">true</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">绑定端口</span><span class="p">,</span><span class="err">开始接收进来的连接</span>
+</span></span><span class="line"><span class="cl">        <span class="n">try</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span> <span class="err">绑定端口</span> <span class="err">生成一个</span><span class="n">ChannelFuture</span> <span class="err">对象</span> <span class="err">启动服务器</span>
+</span></span><span class="line"><span class="cl">            <span class="n">ChannelFuture</span> <span class="n">future</span> <span class="o">=</span> <span class="n">bootstrap</span><span class="o">.</span><span class="n">bind</span><span class="p">(</span><span class="n">socketAddress</span><span class="p">)</span><span class="o">.</span><span class="n">sync</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">            <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;服务器启动开始监听端口: {}&#34;</span><span class="p">,</span> <span class="n">socketAddress</span><span class="o">.</span><span class="n">getPort</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span> <span class="err">对关闭通道进行监听</span>
+</span></span><span class="line"><span class="cl">            <span class="n">future</span><span class="o">.</span><span class="n">channel</span><span class="p">()</span><span class="o">.</span><span class="n">closeFuture</span><span class="p">()</span><span class="o">.</span><span class="n">sync</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="n">catch</span> <span class="p">(</span><span class="n">InterruptedException</span> <span class="n">e</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">e</span><span class="o">.</span><span class="n">printStackTrace</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span> <span class="n">finally</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span><span class="err">关闭主线程组</span>
+</span></span><span class="line"><span class="cl">            <span class="n">bossGroup</span><span class="o">.</span><span class="n">shutdownGracefully</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">            <span class="o">//</span><span class="err">关闭工作线程组</span>
+</span></span><span class="line"><span class="cl">            <span class="n">workGroup</span><span class="o">.</span><span class="n">shutdownGracefully</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">ServerChannelInitializer</span> <span class="k">extends</span> <span class="n">ChannelInitializer</span><span class="o">&lt;</span><span class="n">SocketChannel</span><span class="o">&gt;</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">initChannel</span><span class="p">(</span><span class="n">SocketChannel</span> <span class="n">socketChannel</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="s2">&#34;decoder&#34;</span><span class="p">,</span> <span class="n">new</span> <span class="n">MyMessageDecoder</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="s2">&#34;encoder&#34;</span><span class="p">,</span> <span class="n">new</span> <span class="n">MyMessageEncoder</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">socketChannel</span><span class="o">.</span><span class="n">pipeline</span><span class="p">()</span><span class="o">.</span><span class="n">addLast</span><span class="p">(</span><span class="n">new</span> <span class="n">NettyServerHandler</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="err">@</span><span class="n">Slf4j</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">NettyServerHandler</span> <span class="k">extends</span> <span class="n">ChannelInboundHandlerAdapter</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">客户端连接会触发</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelActive</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;服务端 Active......&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">客户端发消息会触发</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelRead</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="ne">Object</span> <span class="n">msg</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="nb">log</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="s2">&#34;服务器收到消息: {}&#34;</span><span class="p">,</span> <span class="n">msg</span><span class="o">.</span><span class="n">toString</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">MessageProtocol</span> <span class="n">mp</span> <span class="o">=</span> <span class="p">(</span><span class="n">MessageProtocol</span><span class="p">)</span><span class="n">msg</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">int</span> <span class="n">len</span> <span class="o">=</span> <span class="n">mp</span><span class="o">.</span><span class="n">getLen</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span> <span class="o">=</span> <span class="n">mp</span><span class="o">.</span><span class="n">getContent</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;服务器接收到信息如下&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;长度=&#34;</span> <span class="o">+</span> <span class="n">len</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;内容=&#34;</span> <span class="o">+</span> <span class="n">new</span> <span class="ne">String</span><span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">Charset</span><span class="o">.</span><span class="n">forName</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">)));</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">回复消息</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">String</span> <span class="n">responseContent</span> <span class="o">=</span> <span class="n">UUID</span><span class="o">.</span><span class="n">randomUUID</span><span class="p">()</span><span class="o">.</span><span class="n">toString</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">int</span> <span class="n">responseLen</span> <span class="o">=</span> <span class="n">responseContent</span><span class="o">.</span><span class="n">getBytes</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">)</span><span class="o">.</span><span class="n">length</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">byte</span><span class="p">[]</span> <span class="n">responseContent2</span> <span class="o">=</span> <span class="n">responseContent</span><span class="o">.</span><span class="n">getBytes</span><span class="p">(</span><span class="s2">&#34;utf-8&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">构建一个协议包</span>
+</span></span><span class="line"><span class="cl">        <span class="n">MessageProtocol</span> <span class="n">messageProtocol</span> <span class="o">=</span> <span class="n">new</span> <span class="n">MessageProtocol</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setLen</span><span class="p">(</span><span class="n">responseLen</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setContent</span><span class="p">(</span><span class="n">responseContent2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">ctx</span><span class="o">.</span><span class="n">writeAndFlush</span><span class="p">(</span><span class="n">messageProtocol</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">给客户端发送消息</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">channelReadComplete</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ctx</span><span class="o">.</span><span class="n">writeAndFlush</span><span class="p">(</span><span class="s2">&#34;hello client&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*</span> <span class="err">发生异常触发</span>
+</span></span><span class="line"><span class="cl">     <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">exceptionCaught</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">Throwable</span> <span class="n">cause</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">cause</span><span class="o">.</span><span class="n">printStackTrace</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">ctx</span><span class="o">.</span><span class="n">close</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>公共代码部分</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MessageProtocol</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="ne">int</span> <span class="n">len</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="ne">int</span> <span class="n">getLen</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">len</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">setLen</span><span class="p">(</span><span class="ne">int</span> <span class="n">len</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">len</span> <span class="o">=</span> <span class="n">len</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">byte</span><span class="p">[]</span> <span class="n">getContent</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">content</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">void</span> <span class="n">setContent</span><span class="p">(</span><span class="n">byte</span><span class="p">[]</span> <span class="n">content</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">content</span> <span class="o">=</span> <span class="n">content</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="ne">String</span> <span class="n">toString</span><span class="p">()</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="s2">&#34;MessageProtocol{&#34;</span> <span class="o">+</span>
+</span></span><span class="line"><span class="cl">                <span class="s2">&#34;len=&#34;</span> <span class="o">+</span> <span class="n">len</span> <span class="o">+</span>
+</span></span><span class="line"><span class="cl">                <span class="s2">&#34;, content=&#34;</span> <span class="o">+</span> <span class="n">new</span> <span class="ne">String</span><span class="p">(</span><span class="n">content</span><span class="p">)</span> <span class="o">+</span>
+</span></span><span class="line"><span class="cl">                <span class="s1">&#39;}&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MyMessageDecoder</span> <span class="k">extends</span> <span class="n">ReplayingDecoder</span><span class="o">&lt;</span><span class="n">Void</span><span class="o">&gt;</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">decode</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">ByteBuf</span> <span class="ow">in</span><span class="p">,</span> <span class="n">List</span><span class="o">&lt;</span><span class="ne">Object</span><span class="o">&gt;</span> <span class="n">out</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">需要将得到二进制字节码</span><span class="o">-&gt;</span> <span class="n">MessageProtocol</span> <span class="err">数据包</span><span class="p">(</span><span class="err">对象</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl">        <span class="ne">int</span> <span class="n">length</span> <span class="o">=</span> <span class="ow">in</span><span class="o">.</span><span class="n">readInt</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">byte</span><span class="p">[]</span> <span class="n">content</span> <span class="o">=</span> <span class="n">new</span> <span class="n">byte</span><span class="p">[</span><span class="n">length</span><span class="p">];</span>
+</span></span><span class="line"><span class="cl">        <span class="ow">in</span><span class="o">.</span><span class="n">readBytes</span><span class="p">(</span><span class="n">content</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="o">//</span><span class="err">封装成</span> <span class="n">MessageProtocol</span> <span class="err">对象，放入</span> <span class="n">out</span><span class="err">，</span> <span class="err">传递下一个</span><span class="n">handler业务处理</span>
+</span></span><span class="line"><span class="cl">        <span class="n">MessageProtocol</span> <span class="n">messageProtocol</span> <span class="o">=</span> <span class="n">new</span> <span class="n">MessageProtocol</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">        <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setLen</span><span class="p">(</span><span class="n">length</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">messageProtocol</span><span class="o">.</span><span class="n">setContent</span><span class="p">(</span><span class="n">content</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">out</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">messageProtocol</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MyMessageEncoder</span> <span class="k">extends</span> <span class="n">MessageToByteEncoder</span><span class="o">&lt;</span><span class="n">MessageProtocol</span><span class="o">&gt;</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">void</span> <span class="n">encode</span><span class="p">(</span><span class="n">ChannelHandlerContext</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">MessageProtocol</span> <span class="n">msg</span><span class="p">,</span> <span class="n">ByteBuf</span> <span class="n">out</span><span class="p">)</span> <span class="n">throws</span> <span class="n">Exception</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;MyMessageEncoder encode 方法被调用&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">out</span><span class="o">.</span><span class="n">writeInt</span><span class="p">(</span><span class="n">msg</span><span class="o">.</span><span class="n">getLen</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">out</span><span class="o">.</span><span class="n">writeBytes</span><span class="p">(</span><span class="n">msg</span><span class="o">.</span><span class="n">getContent</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div></div>
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diff --git a/docs/posts/detailed/java-redis/index.html b/docs/posts/detailed/java-redis/index.html
new file mode 100644
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+
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+<div id="post_content_toc" class="toc">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e6%a6%82%e8%bf%b0">
+                    Redis概述
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%afredis">
+                    什么是Redis
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
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+                    非关系型数据库
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e7%9b%b8%e5%85%b3%e7%9f%a5%e8%af%86">
+                    Redis相关知识
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+            </li>
+            
+            
+        </ul>
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+        </ul>
+        
+        
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+        <ul class="nav">
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e5%9f%ba%e7%a1%80%e5%91%bd%e4%bb%a4">
+                    Redis基础命令
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+            
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+                <a class="nav-link text-left" href="#redis%e6%95%b0%e6%8d%ae%e7%b1%bb%e5%9e%8b">
+                    Redis数据类型
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+                <a class="nav-link text-left" href="#string">
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+                <a class="nav-link text-left" href="#redis%e5%8f%91%e5%b8%83%e4%b8%8e%e8%ae%a2%e9%98%85">
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+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b9%90%e8%a7%82%e9%94%81">
+                    乐观锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e4%b8%8e%e7%bc%93%e5%ad%98">
+                    Redis与缓存
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%ad%98%e7%a9%bf%e9%80%8f">
+                    缓存穿透
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%ad%98%e5%87%bb%e7%a9%bf">
+                    缓存击穿
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%ad%98%e9%9b%aa%e5%b4%a9">
+                    缓存雪崩
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e9%83%a8%e7%bd%b2%e7%ad%96%e7%95%a5">
+                    Redis部署策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e4%b8%bb%e4%bb%8e%e5%a4%8d%e5%88%b6">
+                    Redis主从复制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%90%ad%e5%bb%ba%e4%b8%bb%e4%bb%8e%e5%a4%8d%e5%88%b6">
+                    搭建主从复制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%bb%e4%bb%8e%e5%a4%8d%e5%88%b6%e8%bf%87%e7%a8%8b">
+                    主从复制过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%80%e4%b8%bb%e4%ba%8c%e4%bb%86">
+                    一主二仆
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%96%aa%e7%81%ab%e7%9b%b8%e4%bc%a0">
+                    薪火相传
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%ae%a2%e4%b8%ba%e4%b8%bb">
+                    反客为主
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e5%93%a8%e5%85%b5%e6%a8%a1%e5%bc%8f">
+                    Redis哨兵模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%90%ad%e5%bb%ba%e5%93%a8%e5%85%b5%e6%a8%a1%e5%bc%8f">
+                    搭建哨兵模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%8d%e5%88%b6%e5%bb%b6%e6%97%b6">
+                    复制延时
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%89%e4%b8%be%e6%9c%ba%e5%88%b6">
+                    选举机制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e9%9b%86%e7%be%a4">
+                    Redis集群
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e9%9b%86%e7%be%a4%e6%95%b0%e6%8d%ae%e5%88%86%e7%89%87">
+                    Redis集群数据分片
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%90%ad%e5%bb%baredis%e9%9b%86%e7%be%a4">
+                    搭建Redis集群
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%93%8d%e4%bd%9credis%e9%9b%86%e7%be%a4">
+                    操作Redis集群
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e5%86%85%e5%ad%98%e6%b7%98%e6%b1%b0%e7%ad%96%e7%95%a5">
+                    Redis内存淘汰策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%a0%e9%99%a4%e7%ad%96%e7%95%a5">
+                    删除策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b7%98%e6%b1%b0%e7%ad%96%e7%95%a5">
+                    淘汰策略
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#lru%e7%ae%97%e6%b3%95%e5%8f%8a%e5%ae%9e%e7%8e%b0">
+                    LRU算法及实现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%b8%80">
+                    方式一
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e5%bc%8f%e4%ba%8c">
+                    方式二
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e6%8c%81%e4%b9%85%e5%8c%96">
+                    Redis持久化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#rdb%e6%8c%81%e4%b9%85%e5%8c%96">
+                    RDB持久化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%9b%b8%e5%85%b3%e9%85%8d%e7%bd%ae">
+                    相关配置
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%89%a7%e8%a1%8c%e8%bf%87%e7%a8%8b">
+                    执行过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#aof%e6%8c%81%e4%b9%85%e5%8c%96">
+                    AOF持久化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%9b%b8%e5%85%b3%e9%85%8d%e7%bd%ae-1">
+                    相关配置
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%89%a7%e8%a1%8c%e8%bf%87%e7%a8%8b-1">
+                    执行过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e6%af%94%e5%8f%8a%e4%bd%bf%e7%94%a8">
+                    对比及使用
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e5%a4%a7key%e9%97%ae%e9%a2%98">
+                    Redis大key问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#redis%e6%95%b0%e6%8d%ae%e5%ba%93%e5%8f%8c%e5%86%99%e4%b8%80%e8%87%b4%e6%80%a7%e9%97%ae%e9%a2%98">
+                    Redis数据库双写一致性问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9c%ba%e6%99%af1">
+                    场景1
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9c%ba%e6%99%af2">
+                    场景2
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
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+                        <h2 id="post_single_title">Redis详解</h2>
+                        <span id="post_page_title_date" class="date">2021.06.17</span>
+                        
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+                    <div class="post_content markdown"><h2 id="redis概述">Redis概述</h2>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.runoob.com/redis/redis-intro.html">https://www.runoob.com/redis/redis-intro.html</a></li>
+<li><a href="https://www.redis.com.cn/redis-interview-questions.html">https://www.redis.com.cn/redis-interview-questions.html</a></li>
+</ul>
+<h3 id="什么是redis">什么是Redis</h3>
+<p>Redis(<strong>Remote Dictionary Server</strong>) Redis 是一个开源的使用 ANSI C 语言编写、遵守 BSD 协议、支持网络、可基于内存亦可持久化的日志型、Key-Value 数据库，并提供多种语言的 API 的<strong>非关系型数据库</strong>。</p>
+<p><strong>简而言之，Redis是一个可基于内存亦可持久化的日志型、Key-Value非关系型数据库。</strong></p>
+<h3 id="非关系型数据库">非关系型数据库</h3>
+<p>非关系型数据库，简称NoSql，是Not Only SQL 的缩写，是对不同于传统的关系型数据库的数据库管理系统的统称，泛指非关系型的数据库。
+NoSql 不依赖业务逻辑方式存储，而以简单的key-value模式存储。因此大大的增加了数据库的扩展能力。</p>
+<p>NoSql特点:</p>
+<ul>
+<li>不遵循SQL标准;</li>
+<li>不支持ACID;</li>
+<li>远超于SQL的性能;</li>
+</ul>
+<p>NoSql适用场景:</p>
+<ul>
+<li>对数据高并发的读写;</li>
+<li>海量数据的读写;</li>
+<li>对数据高可扩展性的;</li>
+</ul>
+<p>NoSql不适用场景:</p>
+<ul>
+<li>需要事务支持;</li>
+<li>基于sql的结构化查询存储，处理复杂的关系,需要及时查询;</li>
+<li>用不着sql的和用了sql也不行的情况，请考虑用NoSql；</li>
+</ul>
+<p>传统数据库遵循 ACID 规则。而 Nosql 一般为分布式,而分布式一般遵循 <a href="/iblog/posts/essays/java-transaction/#cap%E7%90%86%E8%AE%BA">CAP</a> 定理。</p>
+<h3 id="redis相关知识">Redis相关知识</h3>
+<p>Redis 默认16个数据库，类似数组下标从0开始，初始默认使用0号库。可使用命令 <code>select  &lt;dbid&gt;</code>来切换数据库。如: <code>select 8</code> 。</p>
+<p>Redis是单线程+<a href="/iblog/posts/rookie/rookie-io/#reactor-%E6%A8%A1%E5%9E%8B">多路IO复用技术</a></p>
+<p><strong>多路复用：</strong>
+指使用一个线程来检查多个文件描述符（Socket）的就绪状态，比如调用select和poll函数，传入多个文件描述符，如果有一个文件描述符就绪，则返回，否则阻塞直到超时。得到就绪状态后进行真正的操作可以在同一个线程里执行，也可以启动线程执行，比如使用线程池。</p>
+<p><strong>Redis与原子性：</strong>
+所谓原子操作是指不会被线程调度机制打断的操作；这种操作一旦开始，就一直运行到结束，中间不会有任何 context switch （切换到另一个线程）。
+在单线程中，能够在单条指令中完成的操作都可以认为是&quot;原子操作&quot;，因为中断只能发生于指令之间；在多线程中，不能被其它进程或线程打断的操作就叫原子操作；
+<strong>Redis命令的原子性主要得益于Redis的单线程机制。</strong></p>
+<p>Redis使用场景：</p>
+<ul>
+<li>配合关系型数据库做高速缓存
+<ul>
+<li>高频次，热门访问的数据，放入Redis中可降低数据库IO</li>
+<li>分布式架构，做session共享</li>
+</ul>
+</li>
+<li>多样的数据结构存储持久化数据
+<ul>
+<li>利用zset排序，做排行榜功能、大数据去重；</li>
+<li>利用Redis key的实效性数据，如将手机验证码放入Redis；</li>
+<li>发布订阅消息系统，构建队列；</li>
+<li>利用Redis的原子性来做计数器、秒杀等；</li>
+</ul>
+</li>
+</ul>
+<p>Redis特点：</p>
+<ul>
+<li>Redis 支持数据的持久化，可以将内存中的数据保存在磁盘中，重启的时候可以再次加载进行使用;</li>
+<li>Redis 支持数据的备份，即master-slave模式的数据备份;</li>
+<li>Redis 可以存储键与不同数据结构类型之间的映射:</li>
+</ul>
+<p>Redis优点：</p>
+<ul>
+<li>性能极高 – 因为是纯内存操作，Redis能读的速度是110000次/s,写的速度是81000次/s；</li>
+<li>丰富的特性 – Redis还支持 publish/subscribe, 通知, key 过期等等特性；</li>
+<li>丰富的数据类型 – Redis支持二进制案例的 Strings, Lists, Hashes, Sets 及 Ordered Sets 数据类型操作；</li>
+<li>原子 – Redis的所有操作都是原子性的，意思就是要么成功执行要么失败完全不执行。单个操作是原子性的。多个操作也支持事务，即原子性，通过MULTI和EXEC指令包起来；</li>
+</ul>
+<p>Redis缺点：</p>
+<ul>
+<li>Redis 的主要缺点是数据库容量受到物理内存的限制，不能用作海量数据的高性能读写，因此Redis适合的场景主要局限在较小数据量的高性能操作和运算上。</li>
+</ul>
+<h3 id="redis基础命令">Redis基础命令</h3>
+<blockquote>
+<p>如果你使用docker可以先启动Redis容器再用<code>docker exec -it &lt;容器ID&gt; redis-cli</code>命令进入redis客户端。</p>
+</blockquote>
+<p>基础命令：</p>
+<ul>
+<li>查看当前库所有key：<code>keys *</code></li>
+<li>判断某个key是否存在：<code>exists &lt;key&gt;</code></li>
+<li>查看key是什么类型：<code>type &lt;key&gt;</code></li>
+<li>删除指定的key数据：<code>del &lt;key&gt;</code></li>
+<li>根据value选择非阻塞删除,异步删除：<code>unlink &lt;key&gt;</code></li>
+<li>为给定的key设置过期时间：<code>expire key &lt;time&gt;</code></li>
+<li>查看还有多少秒过期，-1表示永不过期，-2表示已过期：<code>ttl &lt;key&gt;</code></li>
+<li>切换数据库：<code>select &lt;dbid&gt;</code></li>
+<li>查看当前数据库的key的数量：<code>dbsize</code></li>
+<li><strong>清空当前库(慎用)：<code>flushdb</code></strong></li>
+<li><strong>清空全部库(慎用)：<code>flushall</code></strong></li>
+</ul>
+<p>更多命令详见：</p>
+<ul>
+<li><a href="http://www.redis.cn/commands.html">http://www.redis.cn/commands.html</a></li>
+<li><a href="https://www.redis.com.cn/commands.html">https://www.redis.com.cn/commands.html</a></li>
+</ul>
+<h3 id="redis数据类型">Redis数据类型</h3>
+<p>Redis 可以存储键和不同类型的值之间的映射。键的类型只能为字符串，值常见有五种数据类型：字符串、列表、集合、散列表、有序集合，Redis后续的更新中又新添加了位图、地理位置等数据类型。</p>
+<table>
+<thead>
+<tr>
+<th>名称</th>
+<th>使用场景</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#string">string-字符串</a></td>
+<td>作为常规的key-value缓存应用</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#hash">hash-哈希</a></td>
+<td>主要用来存储对象信息</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#list">list-列表</a></td>
+<td>缓存一些列表数据：关注列表、粉丝列表等</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#set">set-集合</a></td>
+<td>去重；提供了求交集、并集、差集等操作，可以用来做共同关注、共同好友</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#zset">sorted set-有序集合</a></td>
+<td>用来做排行榜</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#bitmaps">bitmaps-位图</a></td>
+<td>可以用来统计状态，如日活是否浏览过某个东西</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#hyperloglog">hyperloglog-基数统计</a></td>
+<td>用来做统计独立IP数、搜索记录数</td>
+</tr>
+<tr>
+<td><a href="/iblog/posts/detailed/java-redis/#geospatial">geospatial-地理位置</a></td>
+<td>可以用来做附近的人、地图的一些推送接口</td>
+</tr>
+</tbody>
+</table>
+<h4 id="string">String</h4>
+<p>String是Redis最基本的类型，一个key对应一个value。String类型是二进制安全的。意味着Redis的string可以包含任何数据。比如jpg图片或者序列化的对象。String类型是Redis最基本的数据类型，一个Redis中字符串value最多可以是512M。</p>
+<p><img alt="Redis详解-001" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-001.png"></p>
+<p>String的数据结构为简单动态字符串(Simple Dynamic String,缩写SDS)。是可以修改的字符串，内部结构实现上类似于Java的ArrayList，采用预分配冗余空间的方式来减少内存的频繁分配.</p>
+<p>如图中所示,内部为当前字符串实际分配的空间capacity一般要高于实际字符串长度len。当字符串长度小于1M时，扩容都是加倍现有的空间，如果超过1M，扩容时一次只会多扩1M的空间。需要注意的是字符串最大长度为512M。</p>
+<p>常用命令：</p>
+<ul>
+<li>添加键值对：<code>set &lt;key&gt; &lt;value&gt;</code></li>
+<li>查询对应键值：<code>get &lt;key&gt;</code></li>
+<li>将给定的<value>追加到原值的末尾：<code>append &lt;key&gt; &lt;value&gt;</code></li>
+<li>获得值的长度：<code>strlen &lt;key&gt;</code></li>
+<li>只有在<key>不存在时设置<key>的值：<code>setnx &lt;key&gt; &lt;value&gt;</code></li>
+<li>将<key>中储存的数字值增1,只能对数字值操作，如果为空，新增值为1：<code>incr &lt;key&gt;</code></li>
+<li>将<key>中储存的数字值减1,只能对数字值操作，如果为空，新增值为-1：<code>decr &lt;key&gt;</code></li>
+<li>将<key>中储存的数字值增减，自定义步长：<code>incrby/decrby &lt;key&gt;&lt;步长&gt;</code></li>
+</ul>
+<h4 id="list">List</h4>
+<p>Redis列表是简单的字符串列表，按照插入顺序排序。你可以添加一个元素到列表的头部（左边）或者尾部（右边）,单键多值。它的底层实际是个双向链表，对两端的操作性能很高，通过索引下标的操作中间的节点性能会较差。</p>
+<p><img alt="Redis详解-002" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-002.png"></p>
+<p>List的数据结构为快速链表quickList。首先在列表元素较少的情况下会使用一块连续的内存存储，这个结构是ziplist，也即是压缩列表。它将所有的元素紧挨着一起存储，分配的是一块连续的内存。当数据量比较多的时候才会改成quicklist。</p>
+<p>常用命令：</p>
+<ul>
+<li>从左边/右边插入一个或多个值：<code>lpush/rpush &lt;key&gt;&lt;value1&gt;&lt;value2&gt;&lt;value3&gt;</code></li>
+<li>从左边/右边吐出一个值：<code>lpop/rpop &lt;key&gt;</code></li>
+<li>从<key1>列表右边吐出一个值，插到<key2>列表左边：<code>rpoplpush &lt;key1&gt;&lt;key2&gt;</code></li>
+<li>按照索引下标获得元素，从左到右，<code>0 -1</code>表示获取所有：<code>lrange &lt;key&gt;&lt;start&gt;&lt;stop&gt;</code></li>
+<li>获得列表长度：<code>llen &lt;key&gt;</code></li>
+<li>在<value>的后面插入<newvalue>插入值：<code>linsert &lt;key&gt; before &lt;value&gt;&lt;newvalue&gt;</code></li>
+<li>从左边删除n个<value>：<code>lrem &lt;key&gt;&lt;n&gt;&lt;value&gt;</code></li>
+<li>将列表key下标为<index>的值替换成value：<code>lset &lt;key&gt;&lt;index&gt;&lt;value&gt;</code></li>
+</ul>
+<h4 id="set">Set</h4>
+<p>Redis set对外提供的功能与list类似是一个列表的功能，特殊之处在于set是可以<strong>自动去重的</strong>，当你需要存储一个列表数据，又不希望出现重复数据时，set是一个很好的选择，并且set提供了判断某个成员是否在一个set集合内的重要接口，这个也是list所不能提供的。</p>
+<p>Redis的Set是string类型的无序集合。它底层其实是一个value为null的hash表，所以添加，删除，查找的复杂度都是O(1)。</p>
+<blockquote>
+<p>复杂度O(1)：数据增加，查找数据的时间不变。</p>
+</blockquote>
+<p>Set数据结构是dict字典，字典是用哈希表实现的。在Java中HashSet的内部实现使用的是HashMap，只不过所有的value都指向同一个对象。Redis的set结构也是一样，它的内部也使用hash结构，所有的value都指向同一个内部值。</p>
+<p>常用命令：</p>
+<ul>
+<li>将一个或多个元素加入到集合key中，已经存在的元素将被忽略：<code>sadd &lt;key&gt;&lt;value1&gt;&lt;value2&gt;</code></li>
+<li>取出该集合的所有值：<code>smembers &lt;key&gt;</code></li>
+<li>判断集合<key>是否为含有该<value>值，有1，没有0：<code>sismember &lt;key&gt;&lt;value&gt;</code></li>
+<li>返回该集合的元素个数：<code>scard&lt;key&gt;</code></li>
+<li>删除集合中的某个元素：<code>srem &lt;key&gt;&lt;value1&gt;&lt;value2&gt;</code></li>
+<li>随机从该集合中吐出一个值，可指定key，会从集合中删除：<code>spop &lt;key&gt;</code></li>
+<li>随机从该集合中取出n个值，不会从集合中删除：<code>srandmember &lt;key&gt;&lt;n&gt;</code></li>
+<li>把集合中一个值从一个集合移动到另一个集合：<code>smove &lt;source Key&gt;&lt;destination Key&gt;&lt;value&gt;</code></li>
+<li>返回两个集合的交集元素：<code>sinter &lt;key1&gt;&lt;key2&gt;</code></li>
+<li>返回两个集合的并集元素：<code>sunion &lt;key1&gt;&lt;key2&gt;</code></li>
+<li>返回两个集合的差集元素(key1中的，不包含key2中的)：<code>sdiff &lt;key1&gt;&lt;key2&gt;</code></li>
+</ul>
+<h4 id="hash">Hash</h4>
+<p>Redis hash 是一个键值对集合。Redis hash是一个string类型的field和value的映射表，hash特别适合用于存储对象。类似Java里面的Map&lt;String,Object&gt;。</p>
+<p>Hash类型对应的数据结构是两种：ziplist（压缩列表），hashtable（哈希表）。当field-value长度较短且个数较少时，使用ziplist，否则使用hashtable。</p>
+<p>常用命令：</p>
+<ul>
+<li>给<key>集合中的<field>键赋值<value>：<code>hset &lt;key&gt;&lt;field&gt;&lt;value&gt;</code></li>
+<li>从<key1>集合<field>取出 value：<code>hget &lt;key1&gt;&lt;field&gt;</code></li>
+<li>批量设置hash的值：<code>hmset &lt;key1&gt;&lt;field1&gt;&lt;value1&gt;&lt;field2&gt;&lt;value2&gt;...</code></li>
+<li>查看哈希表<key>中，给定域<field>是否存在：<code>hexists&lt;key1&gt;&lt;field&gt;</code></li>
+<li>列出该hash集合的所有<field>：<code>hkeys &lt;key&gt;</code></li>
+<li>列出该hash集合的所有<value>：<code>hvals &lt;key&gt;</code></li>
+<li>为哈希表<key>中的域<field>的值加上增量1：<code>hincrby &lt;key&gt;&lt;field&gt;&lt;increment&gt;</code></li>
+<li>将哈希表<key>中的域<field> 的值设置为<value>,当且仅当域<field>不存在：<code>hsetnx &lt;key&gt;&lt;field&gt;&lt;value&gt;</code></li>
+</ul>
+<h4 id="zset">ZSet</h4>
+<p>sorted set 有序集合也称为 zset，Redis有序集合zset与普通集合set非常相似，是一个没有重复元素的字符串集合。不同之处是有序集合的每个成员都关联了一个评分（score）,这个评分被用来按照从最低分到最高分的方式排序集合中的成员。集合的成员是唯一的，但是评分可以是重复了 。</p>
+<p>因为元素是有序的, 所以你也可以很快的根据评分（score）或者次序（position）来获取一个范围的元素。
+访问有序集合的中间元素也是非常快的,因此你能够使用有序集合作为一个没有重复成员的智能列表。</p>
+<p>SortedSet(zset)是Redis提供的一个非常特别的数据结构，一方面它等价于Java的数据结构Map&lt;String, Double&gt;，可以给每一个元素value赋予一个权重score，另一方面它又类似于TreeSet，内部的元素会按照权重score进行排序，可以得到每个元素的名次，还可以通过score的范围来获取元素的列表。</p>
+<p>zset底层使用了两个数据结构:</p>
+<ul>
+<li>hash，hash的作用就是关联元素value和权重score，保障元素value的唯一性，可以通过元素value找到相应的score值;</li>
+<li>跳跃表，跳跃表的目的在于给元素value排序，根据score的范围获取元素列表;</li>
+</ul>
+<blockquote>
+<p>跳跃表：<br>
+有序集合在生活中比较常见，例如根据成绩对学生排名，根据得分对玩家排名等。对于有序集合的底层实现，可以用数组、平衡树、链表等。数组不便元素的插入、删除；平衡树或红黑树虽然效率高但结构复杂；链表查询需要遍历所有效率低。Redis采用的是跳跃表。跳跃表效率堪比红黑树，实现远比红黑树简单。
+<br>
+举例：对比有序链表和跳跃表，从链表中查询出51</p>
+<p>有序链表: 查找值为51的元素，需要从第一个元素开始依次查找、比较才能找到;共需要6次比较。
+<img alt="Redis详解-003" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-003.png"></p>
+<p>跳跃表:从第2层开始，1节点比51节点小，向后比较；21节点比51节点小，继续向后比较，后面就是NULL了，所以从21节点向下到第1层；在第1层，41节点比51节点小，继续向后，61节点比51节点大，所以从41向下；在第0层，51节点为要查找的节点，节点被找到，共查找4次。
+<img alt="Redis详解-004" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-004.png"></p>
+<p>可以看出跳跃表比有序链表效率要高。</p>
+</blockquote>
+<p>常用命令：</p>
+<ul>
+<li>将一个或多个元素及其score值加入到有序集key当中：<code>zadd  &lt;key&gt;&lt;score1&gt;&lt;value1&gt;&lt;score2&gt;&lt;value2&gt;...</code></li>
+<li>返回有序集 key 中，下标在<start><stop>之间的元素,带withscores，可以让分数一起和值返回到结果集：<code>zrange &lt;key&gt;&lt;start&gt;&lt;stop&gt; [WITHSCORES]</code></li>
+<li>返回有序集 key 中，所有 score 值介于 min 和 max 之间(包括等于 min 或 max )的成员;有序集成员按 score 值递增(从小到大)次序排列：<code>zrangebyscore key minmax [withscores] [limit offset count]</code></li>
+<li>为元素的 score 加上增量：<code>zincrby &lt;key&gt;&lt;increment&gt;&lt;value&gt;</code></li>
+<li>删除该集合下，指定值的元素：<code>zrem &lt;key&gt;&lt;value&gt;</code></li>
+<li>统计该集合，分数区间内的元素个数：<code>zcount &lt;key&gt;&lt;min&gt;&lt;max&gt;</code></li>
+<li>返回该值在集合中的排名，从0开始：<code>zrank &lt;key&gt;&lt;value&gt;</code></li>
+</ul>
+<h4 id="bitmaps">Bitmaps</h4>
+<p>Bitmaps 并不是一种数据结构，实际上它就是字符串，但是可以对字符串的位进行操作。</p>
+<blockquote>
+<p>bit（位）简介：<br>
+现代计算机用二进制（位） 作为信息的基础单位， 1个字节等于8位， 例如“abc”字符串是由3个字节组成， 但实际在计算机存储时将其用二进制表示， “abc”分别对应的ASCII码分别是97、 98、 99， 对应的二进制分别是01100001、 01100010和01100011。</p>
+</blockquote>
+<p>Bitmaps单独提供了一套命令， 所以在Redis中使用Bitmaps和使用字符串的方法不太相同。 可以把Bitmaps想象成一个以位为单位的数组， 数组的每个单元只能存储0和1， 数组的下标在Bitmaps中叫做偏移量。</p>
+<p><img alt="Redis详解-009" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-009.png"></p>
+<p>常用命令：</p>
+<ul>
+<li>设置Bitmaps中某个偏移量的值(0或1),offset偏移量从0开始：<code>setbit &lt;key&gt;&lt;offset&gt;&lt;value&gt;</code></li>
+<li>获取Bitmaps中某个偏移量的值,获取键的第offset位的值,offset偏移量从0开始，不存在则返回0：<code>getbit &lt;key&gt;&lt;offset&gt;</code></li>
+<li>统计字符串从start字节到end字节bit值为1的数量：<code>bitcount &lt;key&gt;[start end]</code></li>
+</ul>
+<p>虽然使用位操作能够极大提高内存使用效率，但也并非总是如此，合理地使用操作位能才能够有效地提高内存使用率和开发效率。</p>
+<p>假设网站有1亿用户， 每天独立访问的用户有5千万， 如果每天用集合类型和Bitmaps分别存储活跃用户可以得到表：</p>
+<p>Set和Bitmaps存储一天活跃用户对比：</p>
+<blockquote>
+<ul>
+<li><strong>Set每个用户id占用空间</strong>：假设用户id用的是long存储占8字节，所以Set用户id占用空间是8*8bit=64bit。</li>
+<li><strong>Bitmaps需要存储的用户量</strong>：因为Bitmaps 并不是一种数据结构，实际上是字符串，所以在存储的时候需要存储全部的用户，此处为1亿。</li>
+</ul>
+</blockquote>
+<table>
+<thead>
+<tr>
+<th>数据类型</th>
+<th>每个用户id占用空间</th>
+<th>需要存储的用户量</th>
+<th>全部内存量</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>Set</td>
+<td>64bit</td>
+<td>50000000</td>
+<td>64位*50000000 = 400MB</td>
+</tr>
+<tr>
+<td>Bitmaps</td>
+<td>1bit</td>
+<td>100000000</td>
+<td>1位*100000000 = 12.5MB</td>
+</tr>
+</tbody>
+</table>
+<p>但Bitmaps并不是万金油，假如该网站每天的独立访问用户很少，例如只有10万，这时候使用Bitmaps就不太合适了，两者的对比如下表所示：</p>
+<table>
+<thead>
+<tr>
+<th>数据类型</th>
+<th>每个用户id占用空间</th>
+<th>需要存储的用户量</th>
+<th>全部内存量</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>Set</td>
+<td>64位</td>
+<td>100000</td>
+<td>64位*100000 = 800KB</td>
+</tr>
+<tr>
+<td>Bitmaps</td>
+<td>1位</td>
+<td>100000000</td>
+<td>1位*100000000 = 12.5MB</td>
+</tr>
+</tbody>
+</table>
+<h4 id="hyperloglog">HyperLogLog</h4>
+<p>Redis 在 2.8.9 版本添加了 HyperLogLog 结构。Redis HyperLogLog 是用来做<strong>基数</strong>统计的算法，HyperLogLog 的优点是，在输入元素的数量或者体积非常非常大时，计算基数所需的空间总是固定的、并且是很小的。</p>
+<blockquote>
+<p>HyperLogLog中的基数：比如数据集 {1, 3, 5, 7, 5, 7, 8}， 那么这个数据集的基数集为 {1, 3, 5 ,7, 8}, 不重复元素为5个，5就是基数。 基数估计就是在误差可接受的范围内，快速计算基数。</p>
+</blockquote>
+<p>在 Redis 里面，每个 HyperLogLog 键只需要花费 12 KB 内存，就可以计算接近 2^64 个不同元素的基数。这和计算基数时，元素越多耗费内存就越多的集合形成鲜明对比。</p>
+<p>但是，因为 HyperLogLog 只会根据输入元素来计算基数，而不会储存输入元素本身，所以 HyperLogLog 不能像集合那样，返回输入的各个元素。</p>
+<p>常用命令：</p>
+<ul>
+<li>添加指定元素到 HyperLogLog 中,估计的近似基数发生变化，则返回1，否则返回0：<code>pfadd &lt;key&gt;&lt; element&gt; [element ...]</code></li>
+<li>计算<key>的近似基数：<code>pfcount&lt;key&gt; [key ...]</code></li>
+<li>将一个或多个<key>合并后的结果存储在另一个<key>中：<code>pfmerge &lt;destkey&gt;&lt;sourcekey&gt; [sourcekey ...]</code></li>
+</ul>
+<h4 id="geospatial">Geospatial</h4>
+<p>GEO，Geographic，地理信息的缩写。该类型，就是元素的2维坐标，在地图上就是经纬度。redis基于该类型，提供了经纬度设置、查询、范围查询、距离查询、经纬度Hash等常见操作。</p>
+<p>常用命令：</p>
+<ul>
+<li>添加地理位置，key名称、经度、纬度、名称：<code>geoadd &lt;key&gt;&lt; longitude&gt;&lt;latitude&gt;&lt;member&gt; [longitude latitude member...]</code></li>
+</ul>
+<blockquote>
+<p>两极无法直接添加，一般会下载城市数据，直接通过 Java 程序一次性导入。有效的经度从 -180 度到 180 度。有效的纬度从 -85.05112878 度到 85.05112878 度。当坐标位置超出指定范围时，该命令将会返回一个错误。已经添加的数据，是无法再次往里面添加的。</p>
+</blockquote>
+<ul>
+<li>获得指定地区的坐标值：<code>geopos  &lt;key&gt;&lt;member&gt; [member...]</code></li>
+<li>获取两个位置之间的直线距离,默认单位，米、km表示单位为千米、mi表示单位为英里、ft表示单位为英尺。：<code>geodist &lt;key&gt;&lt;member1&gt;&lt;member2&gt;  [m|km|ft|mi ]</code></li>
+<li>以给定的经纬度为中心，找出某一半径内的元素：<code>georadius &lt;key&gt;&lt;longitude&gt;&lt;latitude&gt;&lt;radius&gt;&lt;m|km|ft|mi&gt; [withcoord]</code></li>
+</ul>
+<h2 id="redis发布与订阅">Redis发布与订阅</h2>
+<p>Redis 发布订阅 (pub/sub) 是一种消息通信模式：发送者 (pub) 发送消息，订阅者 (sub) 接收消息。Redis 客户端可以订阅任意数量的频道。</p>
+<p>客户端可以订阅频道：</p>
+<p><img alt="Redis详解-005" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-005.png"></p>
+<p>给这个频道发布消息后，消息就会发送给订阅的客户端：</p>
+<p><img alt="Redis详解-006" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-006.png"></p>
+<p><strong>实现Redis发布订阅模式：</strong></p>
+<ol>
+<li>
+<p>打开两个Redis客户端;</p>
+</li>
+<li>
+<p>在其中一个客户端输入：<code>subscribe &lt;channel&gt;</code>,channel为订阅的频道名称：
+<img alt="Redis详解-008" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-008.png"></p>
+</li>
+<li>
+<p>在另外一个客户端输入：<code>publish &lt;channel&gt; &lt;message&gt;</code>,channel为订阅的频道名称,message为推送的消息，返回的1是订阅者数量：
+<img alt="Redis详解-007" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-007.png"></p>
+</li>
+</ol>
+<h2 id="redis事务">Redis事务</h2>
+<p>Redis事务是一个单独的隔离操作：事务中的所有命令都会序列化、按顺序地执行。事务在执行的过程中，不会被其他客户端发送来的命令请求所打断。</p>
+<p>Redis事务的主要作用就是<strong>串联多个命令防止别的命令插队</strong>。</p>
+<p>Redis事务操作相关命令：Multi、Exec、discard</p>
+<p><img alt="Redis详解-014" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-014.png"></p>
+<p>从输入Multi命令开始，输入的命令都会依次进入命令队列中，但不会执行，直到输入Exec后，Redis会将之前的命令队列中的命令依次执行。组队的过程中可以通过discard来放弃组队。
+可以将exec命令理解为提交操作，discard理解为回滚操作。</p>
+<p>multi，exec组队成功，提交成功举例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">127.0.0.1:6379&gt; multi
+</span></span><span class="line"><span class="cl">OK
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k1 v1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k2 v2
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k3 v3
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; exec
+</span></span><span class="line"><span class="cl">1) OK
+</span></span><span class="line"><span class="cl">2) OK
+</span></span><span class="line"><span class="cl">3) OK
+</span></span></code></pre></div><p>multi，discard组队失败举例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">127.0.0.1:6379&gt; multi
+</span></span><span class="line"><span class="cl">OK
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k1 v1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k2 v2
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k3 v3
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; discard
+</span></span><span class="line"><span class="cl">OK
+</span></span></code></pre></div><p>如果在组队过程中执行某个命令失败了，则认为组队失败整个队列都会被取消：</p>
+<p><img alt="Redis详解-015" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-015.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">127.0.0.1:6379&gt; multi
+</span></span><span class="line"><span class="cl">OK
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k1 v1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k2
+</span></span><span class="line"><span class="cl">(error) ERR wrong number of arguments for &#39;set&#39; command
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; exec
+</span></span><span class="line"><span class="cl">(error) EXECABORT Transaction discarded because of previous errors.
+</span></span></code></pre></div><p>如果执行阶段某个命令出了错，则只有报错的命令不会被执行，而其他的命令都会执行且不会回滚：</p>
+<p><img alt="Redis详解-016" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-016.png"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">127.0.0.1:6379&gt; multi 
+</span></span><span class="line"><span class="cl">OK
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k1 v1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; incr k1
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; set k2 v2
+</span></span><span class="line"><span class="cl">QUEUED
+</span></span><span class="line"><span class="cl">127.0.0.1:6379(TX)&gt; exec
+</span></span><span class="line"><span class="cl">1) OK
+</span></span><span class="line"><span class="cl">2) (error) ERR value is not an integer or out of range
+</span></span><span class="line"><span class="cl">3) OK
+</span></span></code></pre></div><h3 id="redis事务特性">Redis事务特性</h3>
+<ul>
+<li>单独的隔离操作：事务中的所有命令都会序列化、按顺序地执行。事务在执行的过程中，不会被其他客户端发送来的命令请求所打断。</li>
+<li>没有隔离级别的概念：队列中的命令没有提交之前都不会实际被执行，因为事务提交前任何指令都不会被实际执行</li>
+<li>不保证原子性：事务中如果有一条命令执行失败，其后的命令仍然会被执行，没有回滚</li>
+</ul>
+<h3 id="事务冲突">事务冲突</h3>
+<p><strong>为什么要使用事务？</strong></p>
+<p>想想一个场景：有很多人有你的账户,同时去参加抢购。一个请求想给金额减8000、一个请求想给金额减5000、一个请求想给金额减1000。</p>
+<p>如果不加事务，有可能一个线程在减8000后，还没有写入数据库，此时另一个线程执行减5000操作写入数据库，然后再将减8000的操作写入数据库，就会造成数据异常。针对于高并发这种情况下我们就需要用事务来控制，可以用加锁来处理。</p>
+<p>在Redis中可以使用<a href="/iblog/posts/rookie/rookie-multi-thread/#%E6%82%B2%E8%A7%82%E9%94%81%E4%B8%8E%E4%B9%90%E8%A7%82%E9%94%81">悲观锁、乐观锁</a>的思想来处理。</p>
+<h4 id="悲观锁">悲观锁</h4>
+<p><img alt="Redis详解-017" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-017.png"></p>
+<p>悲观锁(Pessimistic Lock), 顾名思义，就是很悲观，每次去拿数据的时候都认为别人会修改，所以每次在拿数据的时候都会上锁，这样别人想拿这个数据就会block直到它拿到锁。传统的关系型数据库里边就用到了很多这种锁机制，比如行锁，表锁等，读锁，写锁等，都是在做操作之前先上锁。</p>
+<p>悲观锁实现：在Redis中没有悲观锁，但是可以通过调用lua脚本来实现。</p>
+<blockquote>
+<p>Lua 是一个小巧的脚本语言，Lua脚本可以很容易的被C/C++ 代码调用，也可以反过来调用C/C++的函数，Lua并没有提供强大的库，一个完整的Lua解释器不过200k，所以Lua不适合作为开发独立应用程序的语言，而是作为嵌入式脚本语言。
+很多应用程序、游戏使用LUA作为自己的嵌入式脚本语言，以此来实现可配置性、可扩展性。</p>
+</blockquote>
+<p>LUA脚本在Redis中的优势：</p>
+<ul>
+<li>将复杂的或者多步的redis操作，写为一个脚本，一次提交给redis执行，减少反复连接redis的次数。提升性能。</li>
+<li>LUA脚本是类似redis事务，有一定的原子性，不会被其他命令插队，可以完成一些redis事务性的操作。</li>
+</ul>
+<h4 id="乐观锁">乐观锁</h4>
+<p><img alt="Redis详解-018" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-018.png"></p>
+<p>乐观锁(Optimistic Lock), 顾名思义，就是很乐观，每次去拿数据的时候都认为别人不会修改，所以不会上锁，但是在更新的时候会判断一下在此期间别人有没有去更新这个数据，可以使用版本号等机制。乐观锁适用于多读的应用类型，这样可以提高吞吐量。Redis就是利用这种check-and-set机制实现事务的。</p>
+<p>乐观锁实现：在Redis中如果涉及到了操作数据需要用事务控制的情况可以用 WATCH key &hellip; 命令来监控,可以监控多个key。如果在事务执行之前这个key被其他命令所改动，那么事务将被打断。</p>
+<p><img alt="Redis详解-019" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-019.gif"></p>
+<p>UNWATCH 取消 WATCH 命令对所有 key 的监视。如果在执行 WATCH 命令之后，EXEC 命令或DISCARD命令先被执行了的话，那么就不需要再执行UNWATCH了。</p>
+<h2 id="redis与缓存">Redis与缓存</h2>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://cloud.tencent.com/developer/article/1847904">https://cloud.tencent.com/developer/article/1847904</a></li>
+<li><a href="https://blog.csdn.net/qq_27391133/article/details/80364658">https://blog.csdn.net/qq_27391133/article/details/80364658</a></li>
+</ul>
+<p>因为Redis操作的是纯内存所以性能极高，常用来做缓存，来存放一些热点数据。</p>
+<p>用户第一次访问数据库中的某些数据。整个过程会比较慢，因为是从硬盘上读取的。如果将该用户访问的数据存在数缓存中，这样下一次再访问这些数据的时候就可以直接从缓存中获取了。操作缓存就是直接操作内存，所以速度相当快，但随之而来的也会存在一些问题。</p>
+<h3 id="缓存穿透">缓存穿透</h3>
+<p><img alt="Redis详解-027" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-027.png"></p>
+<p>Redis中的key对应的数据在数据源并不存在，每次针对此key的请求从缓存获取不到，请求都会压到数据源，从而可能压垮数据源。简单理解为,避开缓存,疯狂请求数据库里没有的数据.从而造成服务器宕机。</p>
+<p><strong>解决方法</strong></p>
+<ul>
+<li>对空值缓存：如果一个查询返回的数据为空，不管是数据是否不存在，我们仍然把这个空结果进行缓存，设置空结果的过期时间会很短，最长不超过五分钟；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private RedisTemplate&lt;Long, String&gt; redisTemplate;
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private TestMapper testMapper;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public Test findById(Long id) {
+</span></span><span class="line"><span class="cl">        String testStr = redisTemplate.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">        //判断缓存是否存在，是否为空对象
+</span></span><span class="line"><span class="cl">        if (StringUtils.isEmpty(testStr)) {
+</span></span><span class="line"><span class="cl">            // 这里的锁，使用的时候注意锁的力度，这里建议换成分布式锁，这里做演示
+</span></span><span class="line"><span class="cl">            synchronized (TestServiceImpl.class){
+</span></span><span class="line"><span class="cl">                testStr = redisTemplate.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">                if (StringUtils.isEmpty(testStr)) {
+</span></span><span class="line"><span class="cl">                    Test test = testMapper.findById(id);
+</span></span><span class="line"><span class="cl">                    if(test == null){
+</span></span><span class="line"><span class="cl">                        //构建一个空对象
+</span></span><span class="line"><span class="cl">                        test= new Test();
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                    testStr = JSON.toJSONString(test);
+</span></span><span class="line"><span class="cl">                    // 存入Redis中，下次再次访问就不访问数据库
+</span></span><span class="line"><span class="cl">                    redisTemplate.opsForValue().set(id, testStr);
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        Test test = JSON.parseObject(testStr, Test.class);
+</span></span><span class="line"><span class="cl">        //空对象处理
+</span></span><span class="line"><span class="cl">        if(test.getId() == null){
+</span></span><span class="line"><span class="cl">            return null;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        return JSON.parseObject(testStr, Test.class);
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><ul>
+<li>设置可访问的白名单：使用bitmaps类型定义一个可以访问的名单，名单id作为bitmaps的偏移量，每次访问和bitmap里面的id进行比较，如果访问id不在bitmaps里面，进行拦截，不允许访问。</li>
+<li>使用布隆过滤器：布隆过滤器（Bloom Filter）是1970年由布隆提出的。它实际上是一个很长的二进制向量(位图)和一系列随机映射函数（哈希函数）。布隆过滤器可以用于检索一个元素是否在一个集合中。它的优点是空间效率和查询时间都远远超过一般的算法，缺点是有一定的误识别率和删除困难。将所有可能存在的数据哈希到一个足够大的bitmaps中，一个一定不存在的数据会被 这个bitmaps拦截掉，从而避免了对底层存储系统的查询压力。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private TestMapper testMapper;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private RedisTemplate&lt;Long, String&gt; redisTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    private static BloomFilter&lt;Long&gt; bloomFilter = BloomFilter.create(Funnels.longFunnel(), 1000000000L);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public Test findById(Long id) {
+</span></span><span class="line"><span class="cl">        String testStr = redisTemplate.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">        if (StringUtils.isEmpty(testStr)) {
+</span></span><span class="line"><span class="cl">            //校验是否在布隆过滤器中
+</span></span><span class="line"><span class="cl">            if(bloomFilter.mightContain(id)){
+</span></span><span class="line"><span class="cl">                return null;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            // 这里的锁，使用的时候注意锁的力度，这里建议换成分布式锁，这里做演示
+</span></span><span class="line"><span class="cl">            synchronized (TestServiceImpl.class){
+</span></span><span class="line"><span class="cl">                testStr = redisTemplate.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">                if (StringUtils.isEmpty(testStr) ) {
+</span></span><span class="line"><span class="cl">                    if(bloomFilter.mightContain(id)){
+</span></span><span class="line"><span class="cl">                        return null;
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                    Test test = testMapper.findById(id);
+</span></span><span class="line"><span class="cl">                    if(test == null){
+</span></span><span class="line"><span class="cl">                        //放入布隆过滤器中
+</span></span><span class="line"><span class="cl">                        bloomFilter.put(id);
+</span></span><span class="line"><span class="cl">                        return null;
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                    testStr = JSON.toJSONString(test);
+</span></span><span class="line"><span class="cl">                    redisTemplate.opsForValue().set(id, testStr);
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        return JSON.parseObject(testStr, Test.class);
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><h3 id="缓存击穿">缓存击穿</h3>
+<p><img alt="Redis详解-028" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-028.png"></p>
+<p>key对应的数据存在，但在redis中过期，此时若有大量并发请求过来，这些请求发现缓存过期一般都会从后端数据库加载数据并回设到缓存，大并发集中对这一个点进行访问，当这个key在失效的瞬间，持续的大并发就穿破缓存，直接请求数据库，就像在一个屏障上凿开了一个洞。这个时候大并发的请求可能会瞬间把后端数据源压垮。</p>
+<p><strong>解决方法</strong></p>
+<ul>
+<li>预先设置热门数据：在redis高峰访问之前，把一些热门数据提前存入到redis里面，加大这些热门数据key的时长；</li>
+<li>实时调整：现场监控哪些数据热门，实时调整key的过期时长；</li>
+<li>使用锁：在缓存失效的时候判断拿出来的值为空，先使用缓存工具的某些带成功操作返回值的操作,去set一个mutex key,而不是立即去访问数据源；当操作返回成功时，再进行访问数据库的操作，并回设缓存,最后删除mutex key；当操作返回失败，证明有线程在访问数据源，当前线程睡眠一段时间再重试整个get缓存的方法；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private RedisTemplate&lt;String,Long&gt; template;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private TestMapper testMapper;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> public Long findById(Long id){
+</span></span><span class="line"><span class="cl">     Long value = template.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">     
+</span></span><span class="line"><span class="cl">     if (StringUtils.isEmpty(value)){
+</span></span><span class="line"><span class="cl">         String key = id + &#34;:nx&#34;;
+</span></span><span class="line"><span class="cl">         // 使用 redis setnx 命令如果设置为 1 则代表成功
+</span></span><span class="line"><span class="cl">         if (template.opsForValue().setIfAbsent(key, 1L, 3 * 60, TimeUnit.SECONDS)){
+</span></span><span class="line"><span class="cl">             value = testMapper.findById(id);
+</span></span><span class="line"><span class="cl">             template.opsForValue().set(id.toString(),value,30 * 60);
+</span></span><span class="line"><span class="cl">             template.delete(key);
+</span></span><span class="line"><span class="cl">         }else {
+</span></span><span class="line"><span class="cl">             try {
+</span></span><span class="line"><span class="cl">                 // 睡眠50ms后重试
+</span></span><span class="line"><span class="cl">                 Thread.sleep(50);
+</span></span><span class="line"><span class="cl">                 value = template.opsForValue().get(id);
+</span></span><span class="line"><span class="cl">             } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">                 Thread.interrupted();
+</span></span><span class="line"><span class="cl">             }
+</span></span><span class="line"><span class="cl">         }
+</span></span><span class="line"><span class="cl">         return value;
+</span></span><span class="line"><span class="cl">     }else {
+</span></span><span class="line"><span class="cl">         return value;
+</span></span><span class="line"><span class="cl">     }
+</span></span><span class="line"><span class="cl"> }
+</span></span></code></pre></div><h3 id="缓存雪崩">缓存雪崩</h3>
+<p><img alt="Redis详解-029" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-029.png"></p>
+<p>key对应的数据存在，但在redis中过期，此时若有大量并发请求过来，这些请求发现缓存过期一般都会从后端数据源加载数据并回设到缓存，这个时候大并发的请求可能会瞬间把后端数据源压垮，简单理解为,在某一个时间段,缓存key大面积失效,集中过期.可能会导致服务器宕机。</p>
+<p><strong>解决方法</strong></p>
+<ul>
+<li>构建多级缓存架构：nginx缓存 + redis缓存 + 其他缓存等；</li>
+<li>使用锁或队列：限流降级,在同一时间段,只允许某个线程访问，性能较差；</li>
+<li>设置缓存key永不过期，异步更新；虽然这种方式不会堵塞线程，但是不保证数据一致性，代码复杂度较大，容易堆积垃圾数据；</li>
+<li>将缓存失效时间分散开：比如我们可以在原有的失效时间基础上增加一个随机值，比如1-5分钟随机，这样每一个缓存的过期时间的重复率就会降低，就很难引发集体失效的事件；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">    @Resource
+</span></span><span class="line"><span class="cl">    private RedisTemplate&lt;String,Long&gt; template;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public void setKeys(){
+</span></span><span class="line"><span class="cl">        template.opsForValue().set(&#34;k1&#34;,1L,30 * 60 + (new Random().nextInt(9999)));
+</span></span><span class="line"><span class="cl">        template.opsForValue().set(&#34;k2&#34;,2L,30 * 60 + (new Random().nextInt(9999)));
+</span></span><span class="line"><span class="cl">    }
+</span></span></code></pre></div><h2 id="redis部署策略">Redis部署策略</h2>
+<h3 id="redis主从复制">Redis主从复制</h3>
+<p><img alt="Redis详解-022" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-022.png"></p>
+<p>主从复制，是指将一台Redis服务器的数据，复制到其他的Redis服务器。前者称为主节点(master)，后者称为从节点(slave)；数据的复制是单向的，只能由主节点到从节点。Master以写为主，Slave以读为主。</p>
+<p>主从复制的作用：</p>
+<ul>
+<li>读写分离，性能扩展</li>
+<li>负载均衡</li>
+<li>容灾快速恢复</li>
+</ul>
+<h4 id="搭建主从复制">搭建主从复制</h4>
+<ol>
+<li>至少启动三个redis服务器，并分别连接其客户端；</li>
+<li>在客户端使用命令<code>info replication</code> 查看主从相关信息；</li>
+<li>选定从服务器，并在其客户端执行<code>slaveof &lt;ip&gt; &lt;port&gt;</code>命令将该服务器设置为从服务器；</li>
+<li>在客户端使用命令<code>info replication</code> 查看主从相关信息，查看是否生效；</li>
+<li>在主从服务器上测试读写；</li>
+</ol>
+<h4 id="主从复制过程">主从复制过程</h4>
+<p><img alt="Redis详解-023" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-023.png"></p>
+<ol>
+<li>当从服务器连接到主服务器后，从服务器会向主服务器发送同步数据请求；</li>
+<li>主服务器接收到从服务器发送过来的请求，首先会把主服务器数据进行持久化，变为rdb文件，把rdb文件发送到从服务器，从服务器拿到rdb文件进行读取；</li>
+<li>每次主服务器进行写操作后，会向从服务器进行数据同步；</li>
+</ol>
+<p>全量复制：用于初次复制或其他无法进行部分复制的情况，将主节点中的所有数据都发送给从节点，是一个非常重型的操作。</p>
+<p>部分复制：用于网络中断等情况后的复制，只将中断期间主节点执行的写命令发送给从节点，与全量复制相比更加高效。需要注意的是，如果网络中断时间过长，导致主节点没有能够完整地保存中断期间执行的写命令，则无法进行部分复制，仍使用全量复制。</p>
+<h3 id="一主二仆">一主二仆</h3>
+<p><img alt="Redis详解-024" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-024.png"></p>
+<p>特点：</p>
+<ul>
+<li>当主服务挂掉之后，从服务器不会上位；</li>
+<li>当从服务器挂掉之后，主服务器再次写入数据，此时从服务器再次启动，数据与主服务器保持一致；</li>
+<li>从服务器不能执行写操作；</li>
+</ul>
+<h3 id="薪火相传">薪火相传</h3>
+<p><img alt="Redis详解-025" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-025.png"></p>
+<p>特点：</p>
+<ul>
+<li>当主服务挂掉之后，从服务器不会上位；</li>
+<li>上一个slaver可以是下一个slaver的master，可以有效减轻master的写压力,去中心化降低风险；</li>
+<li>一旦某个slave宕机，后面的slave都没法备份，主机挂了，从机还是从机，都无法写数据了；</li>
+</ul>
+<p>可以使用命令<code>slaveof &lt;ip&gt; &lt;port&gt;</code>将该服务器设置为某服务器的从机。</p>
+<h3 id="反客为主">反客为主</h3>
+<p>当一个master宕机后，后面的slave可以立刻升为master，其后面的slave不用做任何修改，手动执行命令<code>slaveof  no one</code> 将从机变为主机。可以使用哨兵模式让&quot;反客为主&quot;模式变为自动。</p>
+<h3 id="redis哨兵模式">Redis哨兵模式</h3>
+<p><img alt="Redis详解-026" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-026.png"></p>
+<p>反客为主的自动版，能够后台监控主机是否故障，如果故障了根据投票数自动将从库转换为主库。当主机挂掉，从机选举中产生新的主机,当之前的主机再次启动，会变为从机。</p>
+<h4 id="搭建哨兵模式">搭建哨兵模式</h4>
+<ol>
+<li>搭建<a href="/iblog/posts/detailed/java-redis/#搭建主从复制">主从模式</a></li>
+<li>新建哨兵配置<code>sentinel.conf</code>文件：</li>
+</ol>
+<blockquote>
+<ul>
+<li>sentinel：哨兵模式</li>
+<li>monitor：监控</li>
+<li>mymaster：主服务器别名</li>
+<li>127.0.0.1 6379：ip端口</li>
+<li>1：至少有多少个哨兵同意迁移的数量
+<br>
+sentinel monitor mymaster 127.0.0.1 6379 1</li>
+</ul>
+</blockquote>
+<ol start="3">
+<li>执行<code>redis-sentinel ./sentinel.conf</code>启动哨兵</li>
+</ol>
+<h4 id="复制延时">复制延时</h4>
+<p>由于所有的写操作都是先在Master上操作，然后同步更新到Slave上，所以从Master同步到Slave机器有一定的延迟，当系统很繁忙的时候，延迟问题会更加严重，Slave机器数量的增加也会使这个问题更加严重。</p>
+<h4 id="选举机制">选举机制</h4>
+<ol>
+<li>优先选择优先级靠前的；
+<blockquote>
+<p>优先级在redis.conf中默认：slave-priority 100，值越小优先级越高。</p>
+</blockquote>
+</li>
+<li>选择偏移量最大的;
+<blockquote>
+<p>偏移量是指获得原主机数据最全的。</p>
+</blockquote>
+</li>
+<li>选择runid最小的服务；
+<blockquote>
+<p>每个redis实例启动后都会随机生成一个40位的runid,这里也就是随机选择。</p>
+</blockquote>
+</li>
+</ol>
+<h3 id="redis集群">Redis集群</h3>
+<p>Redis 集群是 Redis 提供的分布式数据库方案，集群通过分片来实现数据共享，并提供复制和故障转移。</p>
+<p>Redis集群模式是哨兵模式的一种拓展，在没有Redis 集群的时候，人们使用哨兵模式，所有的数据都存在 master 上面，master 的压力越来越大，垂直扩容再多的 salve 已经不能分担 master 的压力的，因为所有的写操作集中都集中在 master 上。所以人们就想到了水平扩容，就是搭建多个 master 节点。客户端进行分片，手动的控制访问其中某个节点。但是这几个节点之间的数据是不共享的。并且如果增加一个节点，需要手动的将数据进行迁移，维护起来很麻烦。
+另外，主从模式，薪火相传模式，主机宕机，导致ip地址发生变化，应用程序中配置需要修改对应的主机地址、端口等信息。所以才产生了 Redis 集群。</p>
+<p>Redis集群是无中心化集群，即每个结点都是入口。Redis 集群通过分区来提供一定程度的可用性;即使集群中有一部分节点失效或者无法进行通讯，集群也可以继续处理命令请求。</p>
+<p>Redis集群故障恢复：</p>
+<ul>
+<li>如果主节点挂掉后，从结点会上位，主节点恢复后，变为从结点；</li>
+<li>如果某一段插槽的主从节点都宕掉，redis服务是否能运行，这个与redis.conf中的参数<code>cluster-require-full-coverage</code>相关；如果为yes则可以继续使用，为no，那么，该插槽数据全都不能使用，也无法存储；</li>
+</ul>
+<p>Redis集群优点：</p>
+<ul>
+<li>实现扩容；</li>
+<li>分摊服务器压力；</li>
+<li>无中心配置相对简单；</li>
+</ul>
+<p>Redis集群缺点：</p>
+<ul>
+<li>多键操作是不被支持、多键的Redis事务是不被支持、lua脚本不被支持；</li>
+<li>由于集群方案出现较晚，很多公司已经采用了其他的集群方案，而代理或者客户端分片的方案想要迁移至redis cluster，需要整体迁移而不是逐步过渡，复杂度较大；</li>
+</ul>
+<h4 id="redis集群数据分片">Redis集群数据分片</h4>
+<p>Redis 集群没有使用一致性hash, 而是引入了 哈希槽的概念. Redis cluster 有固定的 16384 个 hash slot，对每个 key 计算 CRC16 值，然后对 16384 取模，可以获取来决定放置哪个槽.</p>
+<p>集群的每个节点负责一部分hash槽,举个例子,比如当前集群有3个节点,那么:</p>
+<ul>
+<li>节点 A 包含 0 到 5500号哈希槽.</li>
+<li>节点 B 包含5501 到 11000 号哈希槽.</li>
+<li>节点 C 包含11001 到 16384号哈希槽.</li>
+</ul>
+<p>这种结构很容易添加或者删除节点. 比如如果我想新添加个节点D, 我需要从节点 A, B, C中得部分槽到D上. 如果我想移除节点A,需要将A中的槽移到B和C节点上,然后将没有任何槽的A节点从集群中移除即可. 由于从一个节点将哈希槽移动到另一个节点并不会停止服务,所以无论添加删除或者改变某个节点的哈希槽的数量都不会造成集群不可用的状态.</p>
+<h4 id="搭建redis集群">搭建Redis集群</h4>
+<ol>
+<li>修改<code>redis.conf</code>配置文件，修改前建议备份，修改之后启动redis服务；
+<blockquote>
+<p>redis.conf:
+// 引入原始配置文件
+include /home/bigdata/redis.conf
+// 端口
+port 6379
+// pid文件名称
+pidfile &ldquo;/var/run/redis_6379.pid&rdquo;
+// rdb文件名称
+dbfilename &ldquo;dump6379.rdb&rdquo;
+// 日志文件
+logfile &ldquo;/home/bigdata/redis_cluster/redis_err_6379.log&rdquo;
+// 启用集群模式
+cluster-enabled yes
+// 设定节点配置文件名，启动后会自动生成
+cluster-config-file nodes-6379.conf
+// 设定节点失联时间，超过该时间（毫秒），集群自动进行主从切换
+cluster-node-timeout 15000</p>
+</blockquote>
+</li>
+<li>确保所有redis实例启动后,<code>nodes-xxxx.conf</code>文件都正常生成；</li>
+<li><code>cd /opt/redis-6.2.1/src</code>进入redis的src目录，执行：
+<blockquote>
+<p>此处不要用127.0.0.1,请用真实IP地址
+redis-cli &ndash;cluster create &ndash;cluster-replicas 1 192.168.11.101:6379 192.168.11.101:6380 192.168.11.101:6381 192.168.11.101:6389 192.168.11.101:6390 192.168.11.101:6391</p>
+</blockquote>
+</li>
+<li>使用命令<code>redis-cli -c -p&lt;port&gt;</code>登陆redis集群；</li>
+<li>在客户端使用命令<code>cluster nodes</code>查看集群信息；</li>
+</ol>
+<h4 id="操作redis集群">操作Redis集群</h4>
+<ul>
+<li>执行写入一个键值操作：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">set k1 v1
+</span></span><span class="line"><span class="cl">-&gt;Redirected to slot [12706] located at 192.168.137.3:6381
+</span></span><span class="line"><span class="cl">OK
+</span></span></code></pre></div><blockquote>
+<p>这里的slot是插槽：
+一个 Redis 集群包含 16384 个插槽（hash slot），数据库中的每个键都属于这 16384 个插槽的其中一个；集群使用公式 CRC16(key) % 16384 来计算键 key 属于哪个槽， 其中 CRC16(key) 语句用于计算键 key 的 CRC16 校验和。集群中的每个节点负责处理一部分插槽。
+在redis客户端每次录入、查询键值，redis都会计算出该key应该送往的插槽。</p>
+<p>举个例子，如果一个集群可以有主节点，其中：节点 A 负责处理 0 号至 5460 号插槽;节点 B 负责处理 5461 号至 10922 号插槽;节点 C 负责处理 10923 号至 16383 号插槽。</p>
+</blockquote>
+</li>
+<li>执行写入多个键值操作：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">mset k1 v1 k2 v2 k3 v3
+</span></span><span class="line"><span class="cl">(error) CORSSSLOT Keys in request don&#39;t hash to the same slot 
+</span></span></code></pre></div>不在一个slot下的键值，是不能使用mget,mset等多键操作,但是可以可以通过{}来定义组的概念，从而使key中{}内相同内容的键值对放到一个slot中去：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">mset k1{cust} v1 k2{cust} v2 k3{cust} v3
+</span></span></code></pre></div></li>
+<li>查询集群中的值：
+<ul>
+<li>查询count个slot槽中的键：<code>cluster getkeysinslot &lt;slot&gt; &lt;count&gt;</code></li>
+<li>计算key的插槽值：<code>cluster keyslot &lt;key&gt;</code></li>
+<li>计算插槽值有几个key：<code>cluster countkeysinslot &lt;slot&gt;</code></li>
+</ul>
+</li>
+</ul>
+<h2 id="redis内存淘汰策略">Redis内存淘汰策略</h2>
+<p>长期把Redis做缓存用，总有一天Redis内存总会满的。有没有相关这个问题，Redis内存满了会怎么样？</p>
+<p>在<code>redis.conf</code>中把Redis内存设置为1个字节，做一个测试：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">// 默认单位就是字节
+</span></span><span class="line"><span class="cl">maxmemory 1 
+</span></span></code></pre></div><p>设置完之后重启为了确保测试的准确性，重启一下Redis，之后在用下面的命令，向Redis中存入键值对,模拟Redis打满的情况：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">set k1 v1
+</span></span></code></pre></div><p>执行完后会看到下面的信息：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">(error) OOM command not allowed when used memory &gt; &#39;maxmemory&#39;.
+</span></span></code></pre></div><p>大意：OOM，当当前内存大于最大内存时，这个命令不允许被执行。</p>
+<p>是的，Redis也会出现OOM，正因如此，我们才要避免这种情况发生，正常情况下，不考虑极端业务，Redis不是MySql数据库，不能什么都往里边写，一般情况下Redis只存放热点数据。</p>
+<p>Redis默认最大内存是全部的内存，我们在实际配置的时候，一般配实际服务器内存的3/4也就足够了。</p>
+<h3 id="删除策略">删除策略</h3>
+<p>正因为Redis内存打满后报OOM，为了避免出现该情况所以要设置Redis的删除策略。思考一个问题，一个键到了过期时间之后是不是马上就从内存中被删除的？</p>
+<p>当然不是的，那过期之后到底什么时候被删除？是个什么操作？</p>
+<p>Redis提供了三种删除策略：</p>
+<ol>
+<li>定时删除：创建一个定时器，定时随机的对key执行删除操作；</li>
+<li>惰性删除：类似与懒加载，每次只有用到key的时候才会检查，该key是否已经过期，如果过期进行删除操作；</li>
+<li>定期删除：每隔一段时间，就会检查删除掉过期的key；</li>
+</ol>
+<p>定时删除，即用时间换空间；它对于内存来说是友好的，定时清理出干净的空间，但是对于CPU来说并不是友好的，程序需要维护一个定时器，这就会占用CPU资源。</p>
+<p>惰性的删除，即用空间换时间；它对于CPU来说是友好的，CPU不需要维护其它额外的操作，但是对于内存来说是不友好的，因为要是有些key一直没有被访问到，就会一直占用着内存。</p>
+<p>定期删除，是上面两种方案的折中方案，它每隔一段时间删除过期的key，也就是根据具体的业务，合理的取一个时间定期的删除key。</p>
+<p>若果在数据量很大的情况下，定时删除时，key从来没有被检查到过；惰性删除时，key从来没有被使用过，这样就会造成内存泄漏，大量的key堆积在内存中，导致Redis内存空间紧张。</p>
+<p>所以我们必须有一个兜底方案，即Redis的内存淘汰策略。</p>
+<h3 id="淘汰策略">淘汰策略</h3>
+<p>在 <code>Redis 4.0</code> 版本之前有 6 种策略，4.0 增加了 2种，主要新增了 <code>LFU</code> 算法。下图为 <code>Redis 6.2.0</code> 版本的配置文件：</p>
+<p><img alt="Redis详解-012" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-012.png"></p>
+<p>淘汰策略默认,使用<code>noeviction</code>，意思是不再驱逐的，即等着内存被打满。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">The default is:
+</span></span><span class="line"><span class="cl">maxmemory-policy noeviction
+</span></span></code></pre></div><table>
+<thead>
+<tr>
+<th>策略名称</th>
+<th>描述</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td><code>noeviction</code>(默认策略)</td>
+<td>不会驱逐任何key，即内存满了就报错。</td>
+</tr>
+<tr>
+<td><code>allkeys-lru</code></td>
+<td>所有key都是使用<strong>LRU算法</strong>进行淘汰。</td>
+</tr>
+<tr>
+<td><code>volatile-lru</code></td>
+<td>所有<strong>设置了过期时间的key使用LRU算法</strong>进行淘汰。</td>
+</tr>
+<tr>
+<td><code>allkeys-random</code></td>
+<td>所有的key使用<strong>随机淘汰</strong>的方式进行淘汰。</td>
+</tr>
+<tr>
+<td><code>volatile-random</code></td>
+<td>所有<strong>设置了过期时间的key使用随机淘汰</strong>的方式进行淘汰。</td>
+</tr>
+<tr>
+<td><code>volatile-ttl</code></td>
+<td>所有设置了过期时间的key<strong>根据过期时间进行淘汰，越早过期就越快被淘汰</strong>。</td>
+</tr>
+</tbody>
+</table>
+<p>假如在Redis中的数据有一部分是热点数据，而剩下的数据是冷门数据，或者我们不太清楚我们应用的缓存访问分布状况，这时可以使用<code>allkeys-lru</code>。</p>
+<p>可以在<code>redis.conf</code>配置文件中配置:</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">maxmemory-policy allkeys-lru   // 淘汰策略名字
+</span></span></code></pre></div><p>当然也可以动态的配置，在Redis运行时修改：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">// 设置内存淘汰策略
+</span></span><span class="line"><span class="cl">config set maxmemory-policy allkeys-lru
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 查看内存淘汰策略
+</span></span><span class="line"><span class="cl">config get maxmemory-policy
+</span></span></code></pre></div><h3 id="lru算法及实现">LRU算法及实现</h3>
+<p>LRU是，<code>Least Recently Used</code>的缩写，即最近最少使用，是一种常用的页面置换算法。</p>
+<blockquote>
+<p>页面置换算法：
+进程运行时，若其访问的页面不在内存而需将其调入，但内存已无空闲空间时，就需要从内存中调出一页程序或数据，送入磁盘的对换区，其中选择调出页面的算法就称为页面置换算法。</p>
+</blockquote>
+<p>这个算法的思想就是： 如果一个数据在最近一段时间没有被访问到，那么在将来它被访问的可能性也很小。所以，当指定的空间已存满数据时，应当把最久没有被访问到的数据淘汰。</p>
+<p>明白了思想之后，要实现LRU算法，首先要确定数据结构，再确定实现思路。如果对算法有要求，查询和插入的时间复杂度都是<code>O(1)</code>，可以选用链表+哈希的结构来存储：</p>
+<p><img alt="Redis详解-013" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-013.png"></p>
+<h4 id="方式一">方式一</h4>
+<p>链表+哈希，我们不难想到JDK中的<code>LinkedHashMap</code>,在<code>LinkedHashMap</code>文档注释中找到关于LRU算法的相关描述：</p>
+<blockquote>
+<p>A special {@link #LinkedHashMap(int,float,boolean) constructor} is provided to create a linked hash map whose order of iteration is the order  in which its entries were last accessed,from least-recently accessed to most-recently (<i>access-order</i>).  This kind of map is well-suited to building LRU caches.</p>
+</blockquote>
+<p>大意：<code>{@link #LinkedHashMap(int,float,boolean)}</code>提供了一个特殊的构造器来创建一个链表散列映射，其迭代顺序为其条目最后访问的顺序，从最近最少访问到最近最近(<code>access-order</code>)。这种映射非常适合构建LRU缓存。</p>
+<p>参照<code>LinkedHashMap</code>实现LRU算法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="n">public</span> <span class="k">class</span> <span class="n">MainTest</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="ne">String</span><span class="p">[]</span> <span class="n">args</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">LRUDemo</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="ne">String</span><span class="o">&gt;</span> <span class="n">list0</span> <span class="o">=</span> <span class="n">new</span> <span class="n">LRUDemo</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="bp">true</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;-------------accessOrder等于true-------------&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">context</span><span class="p">(</span><span class="n">list0</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="s2">&#34;-------------accessOrder等于false-------------&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">LRUDemo</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="ne">String</span><span class="o">&gt;</span> <span class="n">list1</span> <span class="o">=</span> <span class="n">new</span> <span class="n">LRUDemo</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="bp">false</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">context</span><span class="p">(</span><span class="n">list1</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">context</span><span class="p">(</span><span class="n">LRUDemo</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="ne">String</span><span class="o">&gt;</span> <span class="n">list</span><span class="p">){</span>
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="s2">&#34;a&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="s2">&#34;b&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s2">&#34;c&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="s2">&#34;d&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s2">&#34;123&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s2">&#34;1234&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s2">&#34;12345&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">();</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">list</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span><span class="s2">&#34;123456&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="n">out</span><span class="o">.</span><span class="n">println</span><span class="p">(</span><span class="n">list</span><span class="o">.</span><span class="n">keySet</span><span class="p">());</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="k">class</span> <span class="n">LRUDemo</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span> <span class="k">extends</span> <span class="n">LinkedHashMap</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">private</span> <span class="ne">int</span> <span class="n">capacity</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">public</span> <span class="n">LRUDemo</span><span class="p">(</span><span class="ne">int</span> <span class="n">capacity</span><span class="p">,</span> <span class="n">boolean</span> <span class="n">accessOrder</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="o">/**</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="n">accessOrder</span> <span class="n">the</span> <span class="n">ordering</span> <span class="n">mode</span> <span class="o">-</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="o">&lt;</span><span class="n">tt</span><span class="o">&gt;</span><span class="bp">true</span><span class="o">&lt;/</span><span class="n">tt</span><span class="o">&gt;</span> <span class="k">for</span> <span class="n">access</span><span class="o">-</span><span class="n">order</span> <span class="err">存取顺序</span><span class="p">:</span><span class="err">如果存贮集合中有相同的元素，再次插入时先删除在插入</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*</span> <span class="o">&lt;</span><span class="n">tt</span><span class="o">&gt;</span><span class="bp">false</span><span class="o">&lt;/</span><span class="n">tt</span><span class="o">&gt;</span> <span class="k">for</span> <span class="n">insertion</span><span class="o">-</span><span class="n">order</span> <span class="err">插入顺序：不会因为集合中有相同元素，再次插入该元素就会打乱位置</span>
+</span></span><span class="line"><span class="cl">         <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">        <span class="n">super</span><span class="p">(</span><span class="n">capacity</span><span class="p">,</span><span class="mf">0.75</span><span class="n">f</span><span class="p">,</span><span class="n">accessOrder</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">        <span class="n">this</span><span class="o">.</span><span class="n">capacity</span> <span class="o">=</span> <span class="n">capacity</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="err">@</span><span class="n">Override</span>
+</span></span><span class="line"><span class="cl">    <span class="n">protected</span> <span class="n">boolean</span> <span class="n">removeEldestEntry</span><span class="p">(</span><span class="n">Map</span><span class="o">.</span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span> <span class="n">V</span><span class="o">&gt;</span> <span class="n">eldest</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">super</span><span class="o">.</span><span class="n">size</span><span class="p">()</span> <span class="o">&gt;</span> <span class="n">capacity</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><h4 id="方式二">方式二</h4>
+<p>除了可以参照<code>LinkedHashMap</code>，也可以自己手动实现：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class MainTest {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        LRUDemo&lt;Integer,String&gt; list0 = new LRUDemo&lt;&gt;(3);
+</span></span><span class="line"><span class="cl">        context(list0);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public static void context(LRUDemo&lt;Integer,String&gt; list){
+</span></span><span class="line"><span class="cl">        list.put(1,&#34;a&#34;);
+</span></span><span class="line"><span class="cl">        list.put(2,&#34;b&#34;);
+</span></span><span class="line"><span class="cl">        list.put(3,&#34;c&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(4,&#34;d&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">        System.out.println();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(3,&#34;123&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(3,&#34;1234&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(3,&#34;12345&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">        System.out.println();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        list.put(5,&#34;123456&#34;);
+</span></span><span class="line"><span class="cl">        System.out.println(list.getMap().keySet());
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">class LRUDemo&lt;K, V&gt; {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    static class Node&lt;K,V&gt;{
+</span></span><span class="line"><span class="cl">        K key;
+</span></span><span class="line"><span class="cl">        V value;
+</span></span><span class="line"><span class="cl">        Node&lt;K,V&gt; prev;
+</span></span><span class="line"><span class="cl">        Node&lt;K, V&gt; next;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public Node(){
+</span></span><span class="line"><span class="cl">            prev = next = null;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public Node(K key,V value){
+</span></span><span class="line"><span class="cl">            this.key = key;
+</span></span><span class="line"><span class="cl">            this.value = value;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    static class DoubleLinkedList&lt;K,V&gt;{
+</span></span><span class="line"><span class="cl">        Node&lt;K,V&gt; head;
+</span></span><span class="line"><span class="cl">        Node&lt;K, V&gt; tail;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public DoubleLinkedList(){
+</span></span><span class="line"><span class="cl">            head = new Node&lt;&gt;();
+</span></span><span class="line"><span class="cl">            tail = new Node&lt;&gt;();
+</span></span><span class="line"><span class="cl">            
+</span></span><span class="line"><span class="cl">            // 如果变成尾插法，需要调换头、尾指针的指向
+</span></span><span class="line"><span class="cl">            head.next = tail;
+</span></span><span class="line"><span class="cl">            tail.prev = head;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public void putHead(Node&lt;K, V&gt; node){
+</span></span><span class="line"><span class="cl">            node.next = head.next;
+</span></span><span class="line"><span class="cl">            node.prev = head; // 将新结点插到头部
+</span></span><span class="line"><span class="cl">            head.next.prev = node;
+</span></span><span class="line"><span class="cl">            head.next = node;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public void remove(Node&lt;K, V&gt; node){
+</span></span><span class="line"><span class="cl">            node.prev.next = node.next;
+</span></span><span class="line"><span class="cl">            node.next.prev = node.prev;
+</span></span><span class="line"><span class="cl">            node.prev = node.next = null;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        public Node&lt;K,V&gt; getLastNode(){
+</span></span><span class="line"><span class="cl">            return tail.prev;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    private int capacity;
+</span></span><span class="line"><span class="cl">    private Map&lt;K, Node&lt;K,V&gt;&gt; map;
+</span></span><span class="line"><span class="cl">    private DoubleLinkedList&lt;K,V&gt; doubleLinkedList;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public Map&lt;K, Node&lt;K, V&gt;&gt; getMap() {
+</span></span><span class="line"><span class="cl">        return map;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public LRUDemo(int capacity){
+</span></span><span class="line"><span class="cl">        this.capacity = capacity;
+</span></span><span class="line"><span class="cl">        this.map = new HashMap&lt;&gt;();
+</span></span><span class="line"><span class="cl">        doubleLinkedList = new DoubleLinkedList&lt;&gt;();
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public void put(K key,V val){
+</span></span><span class="line"><span class="cl">        if (key == null || val == null){
+</span></span><span class="line"><span class="cl">            return;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        // 如果集合中key已经存在，则先删除
+</span></span><span class="line"><span class="cl">        if (map.containsKey(key)){
+</span></span><span class="line"><span class="cl">            Node&lt;K, V&gt; node = map.get(key);
+</span></span><span class="line"><span class="cl">            node.value = val;
+</span></span><span class="line"><span class="cl">            map.put(key,node);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            // 刷新node
+</span></span><span class="line"><span class="cl">            doubleLinkedList.remove(node);
+</span></span><span class="line"><span class="cl">            doubleLinkedList.putHead(node);
+</span></span><span class="line"><span class="cl">        }else {
+</span></span><span class="line"><span class="cl">            // 删除最少使用的key
+</span></span><span class="line"><span class="cl">            if (map.size() == capacity){
+</span></span><span class="line"><span class="cl">                Node&lt;K, V&gt; lastNode = doubleLinkedList.getLastNode();
+</span></span><span class="line"><span class="cl">                doubleLinkedList.remove(lastNode);
+</span></span><span class="line"><span class="cl">                map.remove(lastNode.key);
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            Node&lt;K, V&gt; newNode = new Node&lt;&gt;(key,val);
+</span></span><span class="line"><span class="cl">            map.put(key,newNode);
+</span></span><span class="line"><span class="cl">            doubleLinkedList.putHead(newNode);
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public V get(K key){
+</span></span><span class="line"><span class="cl">        if (!map.containsKey(key)){
+</span></span><span class="line"><span class="cl">            return null;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        Node&lt;K, V&gt; node = map.get(key);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        // 刷新结点位置，将该key移动到队列头部
+</span></span><span class="line"><span class="cl">        doubleLinkedList.remove(node);
+</span></span><span class="line"><span class="cl">        doubleLinkedList.putHead(node);
+</span></span><span class="line"><span class="cl">        return node.value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h2 id="redis持久化">Redis持久化</h2>
+<p><strong>什么是Redis持久化？</strong> 持久化就是把内存的数据写到磁盘中去，防止服务宕机了内存数据丢失。Redis 提供了两种持久化方式:RDB（默认） 和AOF。</p>
+<ul>
+<li>RDB，简而言之，就是在指定的时间间隔内，将 redis 存储的数据生成快照并存储到磁盘等介质上；</li>
+<li>AOF，则是换了一个角度来实现持久化，那就是将 redis 执行过的所有写指令记录下来，在下次 redis 重新启动时，只要把这些写指令从前到后再重复执行一遍，就可以实现数据恢复了；</li>
+</ul>
+<p>其实 RDB 和 AOF 两种方式也可以同时使用，在这种情况下，则会<strong>优先采用 AOF 方式来进行数据恢复</strong>，这是因为 AOF 方式的数据恢复完整度更高。如果你没有数据持久化的需求，也完全可以关闭 RDB 和 AOF 方式，这样的话，redis 将变成一个纯内存数据库，就像 <code>memcache</code> 一样。</p>
+<h3 id="rdb持久化">RDB持久化</h3>
+<p>RDB （Redis DataBase）方式，是将 redis 某一时刻的数据持久化到磁盘中，是一种快照式的持久化方法。</p>
+<h4 id="相关配置">相关配置</h4>
+<ul>
+<li>在redis.conf中配置文件名称,默认是dump.rdb：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">dbfilename dump.rdb
+</span></span></code></pre></div></li>
+<li>rdb文件的保存路径，也可以修改。默认为Redis启动时命令行所在的目录下：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">dir ./
+</span></span></code></pre></div></li>
+<li>默认的快照配置：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">save 3600 1
+</span></span><span class="line"><span class="cl">save 30 10
+</span></span><span class="line"><span class="cl">save 60 10000
+</span></span></code></pre></div></li>
+<li>当Redis无法写入磁盘的话，直接关掉Redis的写操作,默认yes：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">stop-writes-on-bgsave-error yes
+</span></span></code></pre></div></li>
+<li>对于存储到磁盘中的快照，可以设置是否进行压缩存储。如果是的话，redis会采用LZF算法进行压缩：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">rdbcompression yes
+</span></span></code></pre></div></li>
+<li>检查数据完整性,在存储快照后，还可以让redis使用CRC64算法来进行数据校验，但是这样做会增加大约10%的性能消耗，如果希望获取到最大的性能提升，可以关闭此功能，推荐yes：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">rdbchecksum yes
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="执行过程">执行过程</h4>
+<p>redis 在进行数据持久化的过程中，会先将数据写入到一个临时文件中，待持久化过程都结束了，才会用这个临时文件替换上次持久化好的文件。正是这种特性，让我们可以随时来进行备份，因为快照文件总是完整可用的。对于 RDB 方式，redis 会单独创建（fork）一个子进程来进行持久化，而主进程是不会进行任何 IO 操作的，这样就确保了 redis 极高的性能。</p>
+<blockquote>
+<p>fork：</p>
+<ul>
+<li>在Linux程序中，fork()会产生一个和父进程完全相同的子进程，但子进程在此后多会exec系统调用，出于效率考虑，Linux中引入了“写时复制技术”；</li>
+<li>一般情况父进程和子进程会共用同一段物理内存，只有进程空间的各段的内容要发生变化时，才会将父进程的内容复制一份给子进程；</li>
+</ul>
+</blockquote>
+<p><img alt="Redis详解-020" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-020.png"></p>
+<p>如果需要进行大规模数据的恢复，且对于数据恢复的完整性不是非常敏感，那 RDB 方式要比 AOF 方式更加的高效。虽然 RDB 有不少优点，但它的缺点也是不容忽视的：丢失数据风险较大，fork进程在保存rdb文件时会先复制旧文件，如果文件较大则耗时较多。如果你对数据的完整性非常敏感，那么 RDB 方式就不太适合你，因为即使你每 5 分钟都持久化一次，当 redis 故障时，仍然会有近 5 分钟的数据丢失。所以，redis 还提供了另一种持久化方式，那就是 AOF。</p>
+<h3 id="aof持久化">AOF持久化</h3>
+<p>AOF，英文是 Append Only File，即只允许追加不允许改写的文件。如前面介绍的，AOF 方式是<strong>将执行过的写指令记录下来</strong>，在数据恢复时按照从前到后的顺序再将指令都执行一遍。</p>
+<h4 id="相关配置-1">相关配置</h4>
+<ul>
+<li>
+<p>在redis中AOF默认时不开启的：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendonly no
+</span></span></code></pre></div></li>
+<li>
+<p>AOF文件名称,文件路径与rdb保持一致：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendfilename &#34;appendonly.aof&#34;
+</span></span></code></pre></div></li>
+<li>
+<p>AOF同步频率设置：默认的 AOF 持久化策略是每秒钟 fsync 一次（fsync 是指把缓存中的写指令记录到磁盘中），因为在这种情况下，redis 仍然可以保持很好的处理性能，即使 redis 故障，也只会丢失最近 1 秒钟的数据。</p>
+<ol>
+<li>始终同步，每次Redis的写入都会立刻记入日志；性能较差但数据完整性比较好：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendfsync always
+</span></span></code></pre></div><ol start="2">
+<li>每秒同步，每秒记入日志一次，如果宕机，本秒的数据可能丢失：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendfsync everysec
+</span></span></code></pre></div><ol start="3">
+<li>redis不主动进行同步，把同步时机交给操作系统：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">appendfsync no
+</span></span></code></pre></div></li>
+<li>
+<p>Rewrite压缩：AOF采用文件追加方式，文件会越来越大为避免出现此种情况，新增了重写机制,当AOF文件的大小超过所设定的阈值时，Redis就会启动AOF文件的内容压缩，只保留可以恢复数据的最小指令集。举个例子或许更形象，假如我们调用了 100 次 INCR 指令，在 AOF 文件中就要存储 100 条指令，但这明显是很低效的，完全可以把这 100 条指令合并成一条 SET 指令，这就是重写机制的原理。在进行 AOF 重写时，仍然是采用先写临时文件，全部完成后再替换的流程，所以断电、磁盘满等问题都不会影响 AOF 文件的可用性。</p>
+<ol>
+<li>设置重写的基准值，文件达到100%时开始重写：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">auto-aof-rewrite-percentage
+</span></span></code></pre></div><ol start="2">
+<li>设置重写的基准值，最小文件64MB。达到这个值开始重写：</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">auto-aof-rewrite-min-size
+</span></span></code></pre></div><blockquote>
+<p>例如：文件达到70MB开始重写，降到50MB，下次什么时候开始重写？
+系统载入时或者上次重写完毕时，Redis会记录此时AOF大小，设为base_size,如果Redis的AOF文件当前大小&gt;= base_size +base_size*100% (默认)且当前大小&gt;=64mb(默认)的情况下，Redis会对AOF进行重写。</p>
+<p>当前base_size为50MB，根据公式：base_size +base_size*100% = 100MB</p>
+</blockquote>
+</li>
+<li>
+<p>如果在追加日志时，恰好遇到磁盘空间满或断电等情况导致日志写入不完整，也没有关系，可以进行恢复：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">redis-check-aof --fix AOP文件名称
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="执行过程-1">执行过程</h4>
+<p><img alt="Redis详解-021" src="/iblog/posts/annex/images/essays/Redis%E8%AF%A6%E8%A7%A3-021.png"></p>
+<ul>
+<li>客户端的请求写命令会被append追加到AOF缓冲区内；</li>
+<li>AOF缓冲区根据AOF持久化策略[always,everysec,no]将操作sync同步到磁盘的AOF文件中；</li>
+<li>AOF文件大小超过重写策略或手动重写时，会对AOF文件rewrite重写，压缩AOF文件容量；</li>
+<li>Redis服务重启时，会重新load加载AOF文件中的写操作达到数据恢复的目的；</li>
+</ul>
+<p>AOF 方式的一个好处，我们通过一个“场景再现”来说明。某同学在操作 redis 时，不小心执行了 FLUSHALL，导致 redis 内存中的数据全部被清空了，这是很悲剧的事情。不过这也不是世界末日，只要 redis 配置了 AOF 持久化方式，且 AOF 文件还没有被重写（rewrite），我们就可以用最快的速度暂停 redis 并编辑 AOF 文件，将最后一行的 FLUSHALL 命令删除，然后重启 redis，就可以恢复 redis 的所有数据到 FLUSHALL 之前的状态了。这就是 AOF 持久化方式的好处之一。但是如果 AOF 文件已经被重写了，那就无法通过这种方法来恢复数据了。</p>
+<p>虽然优点多多，但 AOF 方式也同样存在缺陷，比如在同样数据规模的情况下，AOF 文件要比 RDB 文件的体积大。而且 AOF 方式的恢复速度也要慢于 RDB 方式。</p>
+<h3 id="对比及使用">对比及使用</h3>
+<p>官方推荐两个都启用，如果对数据不敏感，可以选单独用RDB，如果对数据不敏感，可以选单独用RDB，如果只是做纯内存缓存，可以都不用。</p>
+<table>
+<thead>
+<tr>
+<th></th>
+<th>RDB</th>
+<th>AOF</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>定义</td>
+<td>在指定的时间间隔能对你的数据进行快照存储</td>
+<td>记录每次对服务器的写操作,当服务器重启的时候会重新执行这些命令来恢复原始的数据,AOF命令以redis协议追加保存每次写的操作到文件末尾</td>
+</tr>
+<tr>
+<td>优先级</td>
+<td>低</td>
+<td>高</td>
+</tr>
+<tr>
+<td>数据完整性</td>
+<td>易丢失</td>
+<td>不易丢失</td>
+</tr>
+<tr>
+<td>恢复数据速度</td>
+<td>较快</td>
+<td>较慢</td>
+</tr>
+<tr>
+<td>数据文件损坏</td>
+<td>不能修复</td>
+<td>可使用命令进行修复</td>
+</tr>
+<tr>
+<td>数据文件大小</td>
+<td>较小</td>
+<td>较大，但是可压缩</td>
+</tr>
+</tbody>
+</table>
+<h2 id="redis大key问题">Redis大key问题</h2>
+<p>所谓的大key问题是某个key的value比较大，所以本质上是大value问题.因为key往往是程序可以自行设置的，value往往不受程序控制，因此可能导致value很大。</p>
+<p>因为Redis是单线程的,单线程中请求任务的处理是串行的，前面完不成，后面处理不了，同时也导致分布式架构中内存数据和CPU的不平衡.所以大key问题最典型的就是阻塞线程，并发量下降，导致客户端超时，服务端业务成功率下降。</p>
+<p>大key问题一般是由于业务方案设计不合理,没有预见value的动态增长问题产生的.一直往value塞数据，没有删除机制，迟早要爆炸或数据没有合理做分片，将大key变成小key. 在线上一般通过集成<a href="https://www.redis.com.cn/clients.html">Redis可视化工具</a>,来发现和定位大key问题.</p>
+<p>解决大key问题,根据大key的实际用途可以分为两种情况：可删除和不可删除。如果发现某些大key并非热key就可以在DB中查询使用，则可以在Redis中删掉.</p>
+<ul>
+<li>
+<p>删除</p>
+<ol>
+<li>当Redis版本大于4.0时，可使用UNLINK命令安全地删除大Key，该命令能够以非阻塞的方式，逐步地清理传入的Key。</li>
+<li>当Redis版本小于4.0时，避免使用阻塞式命令KEYS，而是建议通过SCAN命令执行增量迭代扫描key，然后判断进行删除。</li>
+</ol>
+</li>
+<li>
+<p>不可删除</p>
+<ol>
+<li>当value是string时，比较难拆分，则使用序列化、压缩算法将key的大小控制在合理范围内，但是序列化和反序列化都会带来更多时间上的消耗。</li>
+<li>当value是string，压缩之后仍然是大key，则需要进行拆分，一个大key分为不同的部分，记录每个部分的key，使用 multi get 等操作实现事务读取。</li>
+</ol>
+</li>
+</ul>
+<h2 id="redis数据库双写一致性问题">Redis数据库双写一致性问题</h2>
+<p>你只要用缓存，就可能会涉及到缓存与数据库双存储双写，你只要是双写，就一定会有数据一致性的问题.</p>
+<p>一般来说，如果允许缓存可以稍微的跟数据库偶尔有不一致的情况，也就是说如果你的系统不是严格要求 “缓存+数据库” 必须保持一致性的话，最好不要做这个方案，即：读请求和写请求串行化，串到一个内存队列里去。</p>
+<p>串行化可以保证一定不会出现不一致的情况，但是它也会导致系统的吞吐量大幅度降低，用比正常情况下多几倍的机器去支撑线上的一个请求。</p>
+<p>最经典的Redis使用方案:</p>
+<ul>
+<li>读的时候，先读缓存，缓存没有的话，就读数据库，然后取出数据后放入缓存，同时返回响应;</li>
+<li>更新的时候，先更新数据库，然后再删除缓存;</li>
+</ul>
+<h3 id="场景1">场景1</h3>
+<p>先更新数据库，再删除缓存。如果删除缓存失败了，那么会导致数据库中是新数据，缓存中是旧数据，数据就出现了不一致</p>
+<p>解决思路:</p>
+<ul>
+<li>先删除缓存，再更新数据库。如果数据库更新失败了，那么数据库中是旧数据，缓存中是空的，那么数据不会不一致。因为读的时候缓存没有，所以去读了数据库中的旧数据，然后更新到缓存中。(删除缓存失败会导致程序运行终止的情况下)</li>
+<li>延时双删。依旧是先更新数据库，再删除缓存，唯一不同的是，我们把这个删除的动作，在不久之后再执行一次，比如 5s 之后。
+<blockquote>
+<p>延迟双删的主要思路为异步重试,一般会把重试的步骤放在MQ中进行不断尝试</p>
+</blockquote>
+</li>
+<li>订阅数据库变更日志。 我们可以通过工具（canal）订阅这个日志，拿到具体操作的数据，然后再根据这条数据，去删除对应的缓存。</li>
+</ul>
+<h3 id="场景2">场景2</h3>
+<p>并发,数据发生了变更，先删除了缓存，然后要去修改数据库，此时还没修改。一个请求过来，去读缓存，发现缓存空了，去查询数据库，查到了修改前的旧数据，放到了缓存中。随后数据变更的程序完成了数据库的修改</p>
+<blockquote>
+<p>这种场景一般只会在数据在并发的进行读写的时候，才可能会出现这种问题,如果说你的并发量很低的话，特别是读并发很低，每天访问量就 1 万次，那么很少的情况下，会出现刚才描述的那种不一致的场景</p>
+</blockquote>
+<p>解决思路: 当第二个请求进来的时候,第一个请求删除了缓存,正要去修改数据库,此时把第二个请求加入到一个队列中,让其等待第一个请求执行完毕,在从队列中获取第二个请求,让其执行.</p>
+<p>该解决方案，最大的风险点在于说，可能数据更新很频繁，导致队列中积压了大量更新操作在里面，然后读请求会发生大量的超时，最后导致大量的请求直接走数据库。 如果一个内存队列中可能积压的更新操作特别多，那么你就要加机器，让每个机器上部署的服务实例处理更少的数据，那么每个内存队列中积压的更新操作就会越少.</p>
+<p>粗略测算,如果一秒有 500 的写操作，如果分成 5 个时间片，每 200ms 就 100 个写操作，放到 20 个内存队列中，每个内存队列，可能就积压 5 个写操作。每个写操作性能测试后，一般是在 20ms 左右就完成，那么针对每个内存队列的数据的读请求，也就最多 hang 一会儿，200ms 以内肯定能返回了.</p>
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+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af%e5%be%ae%e6%9c%8d%e5%8a%a1%e6%9e%b6%e6%9e%84">
+                    什么是微服务架构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ba%e4%bb%80%e4%b9%88%e8%a6%81%e4%bd%bf%e7%94%a8%e5%be%ae%e6%9c%8d%e5%8a%a1">
+                    为什么要使用微服务
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%8e%e5%8d%95%e4%bd%93%e6%9e%b6%e6%9e%84%e8%bf%81%e7%a7%bb%e5%88%b0%e5%be%ae%e6%9c%8d%e5%8a%a1%e6%9e%b6%e6%9e%84">
+                    从单体架构迁移到微服务架构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e6%b2%bb%e7%90%86">
+                    服务治理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e6%b2%bb%e7%90%86%e6%b2%bb%e7%9a%84%e6%98%af%e4%bb%80%e4%b9%88">
+                    服务治理治的是什么
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e6%b3%a8%e5%86%8c%e5%8f%91%e7%8e%b0">
+                    服务注册发现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e7%86%94%e6%96%ad%e9%99%8d%e7%ba%a7">
+                    服务熔断降级
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e7%bd%91%e5%85%b3">
+                    服务网关
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e8%b0%83%e7%94%a8">
+                    服务调用
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e8%b4%9f%e8%bd%bd">
+                    服务负载
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%8d%e5%8a%a1%e9%85%8d%e7%bd%ae%e4%b8%ad%e5%bf%83">
+                    服务配置中心
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#springcloud%e4%bd%93%e7%b3%bb">
+                    SpringCloud体系
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#eureka">
+                    Eureka
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hystrix">
+                    Hystrix
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#spring-cloud-gateway">
+                    Spring Cloud Gateway
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#openfeign">
+                    OpenFeign
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#ribbon">
+                    Ribbon
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#springcloud-config">
+                    SpringCloud Config
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#springboot">
+                    SpringBoot
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#dubbo%e4%bd%93%e7%b3%bb">
+                    Dubbo体系
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#zookeeper">
+                    ZooKeeper
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#springcloud-alibaba%e4%bd%93%e7%b3%bb">
+                    SpringCloud Alibaba体系
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#nacos">
+                    Nacos
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#sentinel">
+                    Sentinel
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
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+
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+                        <h2 id="post_single_title">微服务治理详解</h2>
+                        <span id="post_page_title_date" class="date">2021.06.21</span>
+                        
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+                    <div class="post_content markdown"><h2 id="什么是微服务架构">什么是微服务架构</h2>
+<blockquote>
+<p>In short， the microservice architectural style is an approach to developing a single application as a suite of small services，
+each running in its own process and communicating with lightweight mechanisms， often an HTTP resource API。
+These services are built around business capabilities and independently deployable by fully automated deployment machinery。
+There is a bare minimum of centralized management of these services， which may be written in different programming languages and use different data storage technologies。 ——<a href="https://martinfowler.com/articles/microservices.html">James Lewis and Martin Fowler (2014)</a></p>
+</blockquote>
+<p>大意：简而言之，微服务体系结构风格是一种将单个应用程序开发为一套小型服务的方法，每个服务运行在自己的进程中，并与轻量级机制(通常是HTTP资源API)通信。
+这些服务是围绕业务功能构建的，可以通过全自动部署机制进行独立部署。对这些服务的集中管理是最低限度的，这些服务可能用不同的编程语言编写，并使用不同的数据存储技术。</p>
+<p>微服务是一种架构风格，将服务围绕业务功能拆分，一个应用拆分为一组小型服务，每个服务运行在自己的进程内，也就是可独立部署和升级，服务之间使用轻量级HTTP交互，可以由全自动部署机制独立部署，去中心化，服务自治。服务可以使用不同的语言、不同的存储技术。</p>
+<h2 id="为什么要使用微服务">为什么要使用微服务</h2>
+<p>说起微服务就不得不说微服务之前的单体应用，有对比才能看的出微服务对比之前的单体应用到底强在哪？为什么我们要抛弃单体应用？</p>
+<ul>
+<li>单体应用往往所有的功能打包在一个包里，包含了 DO/DAO，Service，UI等所有逻辑，如果要修改一部分代码就需要全部重新部署，所以改动影响大，风险高。微服务模式弥补了这个缺陷，它将应用合理的拆分，实现敏捷开发和快速部署。</li>
+<li>单体应用只能通过在负载均衡器后面放置整个应用程序的多个实例来进行水平扩展，如果想要扩展特定的程序，显然是不行的，则需要使用到微服务模式实现。</li>
+<li>因为单体应用所有的功能全部都达到一个包里面，所以耦合性比较强，对于程序员来说代码维护会收到影响，出现了什么问题也不太方便进行排查。</li>
+<li>如果没有正确的设计，单体应用的一部分失败可能会级联并导致整个系统崩溃。而这种情况可以使用微服务的熔断、降级的思想来解决。</li>
+</ul>
+<p>微服务虽然好处多多，但是缺点就是服务众多，不好管理，这也就是为什么要治理微服务，治理成本高，不利于维护系统，项目成本会升高，所以项目架构设计时应综合考量。</p>
+<p>建议设计的原则是业务驱动、设计保障、演进式迭代、保守治疗的方式。搞不清楚，有争议的地方先尽量不要拆，如果确实要拆，要经过业务分析后慎重设计，把真正相对独立的部分拆分出来，可以借鉴 <strong>DDD</strong> 的方式。拆了以后要观察微服务的接口是否稳定，针对业务需求的变更微服务的模块是否可以保持相对稳定，是否可以独立演进。</p>
+<blockquote>
+<p>DDD: Domain-driven design的简称，译为领域驱动设计，是一种通过将实现连接到持续进化的模型来满足复杂需求的软件开发方法。
+<br>
+核心思想：DDD其实是面向对象方法论的一个升华。无外乎是通过划分领域（聚合根、实体、值对象）、领域行为封装到领域对象（充血模式）、内外交互封装到防腐层、职责封装到对应的模块和分层，从而实现了高内聚低耦合。
+链接：<a href="https://blog.csdn.net/qq_31960623/article/details/119840131">https://blog.csdn.net/qq_31960623/article/details/119840131</a></p>
+</blockquote>
+<h2 id="从单体架构迁移到微服务架构">从单体架构迁移到微服务架构</h2>
+<p>重写代码，但是不要大规模重写代码，重写代码听起来很好但风险较大，如果大规模重写代码可能会导致程序出现各种各样的bug;(当你承担重建一套全新基于微服务的应用程序不需要使用时候，可以采用重写这种方法)</p>
+<p>逐步迁移单体应用的功能，独立出来形成新的微服务，同时需要与旧的单体应用集成，这可以保证系统的正常运行，单体式应用在整个架构中比例逐渐下降直到消失或者成为微服务架构一部分;</p>
+<p>虽然在逐步的迁移功能，但是也会有源源不断的需求需要开发，此时该停止让单体式应用继续变大，也就是说当开发新功能时不应该为旧单体应用添加新代码，应该是将新功能开发成独立微服务;</p>
+<p>一个巨大的复杂单体应用由成十上百个模块构成，每个都是被抽取对象。决定第一个被抽取模块一般都是挑战，一般最好是从最容易抽取的模块开始，这会让开发者积累足够经验，这些经验可以为后续模块化工作带来巨大好处。</p>
+<p>转换模块成为微服务一般很耗费时间，一般可以根据获益程度来排序，一般从经常变化模块开始会获益最大。一旦转换一个模块为微服务，就可以将其开发部署成独立模块，从而加速开发进程。比如，抽取一些消耗内存资源较大的代码，将其弄成一个服务，然后可以将其部署在大内存主机上。同样的，将对计算资源很敏感的算法应用抽取出来也是非常有益的，这种服务可以被部署在有很多 CPU 的主机上。
+有三种策略可以考虑：将新功能以微服务方式实现；将表现层与业务数据访问层分离；将现存模块抽取变成微服务。</p>
+<p>首先要将抽离的相关功能,封装成相关几个方法,几个类,几个包中;定义好模块和单体应用之间的几个大概的接口,从程序内部开始调用; 一旦完成相关的接口,也就将此模块转换成独立微服务。为了实现，必须写代码使得单体应用和微服务之间通过使用进程间通信机制的API来交换信息;服务和单体应用整合的API代码就成为了容灾层;</p>
+<p>然后,将抽离的功能,转化为独立的服务进行部署,将其整合成一个微服务基础框架; 每抽取一个服务，就朝着微服务方向前进一步，随着时间推移，单体应用将会越来越简单，用户就可以增加更多独立的微服务。</p>
+<h2 id="服务治理">服务治理</h2>
+<h3 id="服务治理治的是什么">服务治理治的是什么</h3>
+<p>摘自《微服务设计》:</p>
+<blockquote>
+<p>在进行城市交通规划之前首先要做的第一个事情是收集信息，要能够知道这个城市发生了什么，所以在各个路口需要安装采集探头，记录车来车往的信息。有了信息以后就需要对信息进行分析了，那么就需要可视化的图形界面，能够一眼就看出什么地方出了问题，通往哪个工厂的路坏了。发现了问题就要解决问题了，限制一下拥堵路段的流量，把去往一个公园的车辆导向到另外一个类似的公园。最后，如果把城市作为一个国家来考虑，那么每个进入这个城市的车辆都需要进行检查，看看有没有携带违禁品，最后给这些不熟悉道路的外地车规划路线。通过上面这个思考的过程，我们发现要对一个城市进行治理的时候，第一要采集信息，然后要能够对采集的信息进行监控和分析，最后根据分析的结果采取对应的治理策略。另外从整体安全的角度考虑还需要一个守门人</p>
+</blockquote>
+<p>我们也用同样的思路来思考服务治理，网关就是整个整体的守门人，日志采集，追踪工具，服务注册发现都是用来采集信息的，然后需要监控平台来展现这些采集的信息，并进行监控和分析。
+最后根据分析的结果采取治理策略，有的服务快撑不住了要限流，有的服务坏了要熔断，并且还能够及时的调整这些服务的配置。</p>
+<p><img alt="分布式架构-011" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-011.png"></p>
+<h3 id="服务注册发现">服务注册发现</h3>
+<p>服务注册与发现是微服务架构中的核心概念。在微服务架构中，服务数量众多，服务间通信变得尤为重要。为了实现动态的服务间通信，每个服务都需要将自己的信息注册到注册中心，以便其他服务能够发现并调用。</p>
+<ul>
+<li>服务注册：服务提供者在启动时将自己的信息（如IP地址、端口号等）注册到注册中心。</li>
+<li>服务发现：服务消费者从注册中心查询所需服务的地址信息，实现动态调用。</li>
+</ul>
+<p>当服务器启动的时候，会把当前自己服务器的信息，比如：服务地址通讯地址等，以别名方式注册到注册中心上。另一方消费者服务提供者，以该别名的方式去注册中心上获取到实际的服务通讯地址，然后再实现本地RPC调用。
+RPC远程调用框架核心设计思想在于注册中心，因为使用注册中心管理每个服务与服务之间的一个依赖关系。在任何RPC远程框架中，都会有一个注册中心存放服务地址相关信息。</p>
+<h3 id="服务熔断降级">服务熔断降级</h3>
+<p>由于分布式架构中应用程序依赖关系可能非常多，每个依赖关系在某些时候将不可避免地失败，针对服务调用失败，为了缩小调用失败的影响，引入了服务熔断降级的思想。</p>
+<p>多个微服务之间调用的时候，假设微服务A调用微服务B和微服务C，微服务B和微服务C又调用其它的微服务，这就是所谓的“扇出”。如果扇出的链路上某个微服务的调用响应时间过长或者不可用，对微服务A的调用就会占用越来越多的系统资源，进而引起系统崩溃，所谓的“雪崩效应”。</p>
+<ul>
+<li>服务熔断：熔断机制是应对雪崩效应的一种微服务链路保护机制，当链路的某个微服务不可用或者响应时间太长时，将快速的返回设置好的提示信息。</li>
+<li>服务降级：服务降级一般是指在服务器压力剧增的时候，根据实际业务使用情况以及流量，对一些服务和页面有策略的不处理或者用一种简单的方式进行处理，从而释放服务器资源的资源以保证核心业务的正常高效运行。</li>
+</ul>
+<p>服务熔断是应对系统服务雪崩的一种保险措施，给出的一种特殊降级措施。而服务降级则是更加宽泛的概念，主要是对系统整体资源的合理分配以应对压力。服务熔断可看作特殊降级。</p>
+<h3 id="服务网关">服务网关</h3>
+<p>微服务背景下，一个系统被拆分为多个服务，但是像安全认证、流量控制、日志、监控等功能是每个服务都需要的，没有网关的话，我们就需要在每个服务中单独实现，这使得我们做了很多重复的事情并且没有一个全局的视图来统一管理这些功能。</p>
+<p><img alt="分布式架构-005" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-005.png"></p>
+<p>网关的角色是作为一个 API 架构，用来保护、增强和控制对于 API 服务的访问。API 网关是一个处于应用程序或服务（提供 REST API 接口服务）之前的系统，用来管理授权、访问控制和流量限制等，这样 REST API 接口服务就被 API 网关保护起来，对所有的调用者透明。
+因此，隐藏在 API 网关后面的业务系统就可以专注于创建和管理服务，而不用去处理这些策略性的基础设施。</p>
+<p>网关作用：</p>
+<ul>
+<li>作为所有API接口服务的请求接入点；</li>
+<li>作为所有后端业务服务的聚合点；</li>
+<li>实现安全、验证、路由、过滤、流量等策略；</li>
+<li>对所有API服务和策略进行统一管理；</li>
+</ul>
+<h3 id="服务调用">服务调用</h3>
+<p>服务调用可以说是微服务中最关键的，如果没有服务调用不会出现熔断降级、也不会出现服务负载、服务注册，分布式的服务治理可以说是围绕服务调用展开的。</p>
+<p>常见的服务之间的调用方式有两种：</p>
+<ul>
+<li>RPC远程过程调用：定义数据式，基于原生TCP通信，速度快，效率高。早期的wedservice，现在热门的dubbo，都是RPC的典型代表；</li>
+<li>Http：http其实是一种网络传输协议，基于TCP，规定了数据传输的格式。现在客户端浏览器与服务器端通信基本都是采用HTTP协议，也可以用来进行远程服务调用。缺点是消息封装臃肿，优势是对服务的提供和调用方没有任何技术限定，自由灵活，更符合为服务理念；</li>
+</ul>
+<p>现在热门的Rest风格，就可以通过HTTP协议来实现，如果公司全部采用Java技术栈，那么使用Dubbo作为微服务框架是一个不错的选择；如果公司的技术栈多样化，而且你更青睐Spring家族，那么SpringCloud搭建微服务是不二之选。</p>
+<h3 id="服务负载">服务负载</h3>
+<blockquote>
+<p>负载均衡，英文名称为Load Balance，其含义就是指将工作任务进行平衡、分摊到多个操作单元上进行运行，例如FTP服务器、Web服务器、企业核心应用服务器和其它主要任务服务器等，从而协同完成工作任务。</p>
+</blockquote>
+<p>当前服务与服务之间进行相互调用时，在分布式架构下应用都是集群部署，所以这个时候就需要进行服务负载，即将收到的请求分摊到对应的服务器上，从而达到系统的高可用。</p>
+<p>常见负载均衡算法：</p>
+<ul>
+<li>随机分配：随机选择一台服务器来分配任务。它保证了请求的分散性达到了均衡的目的。同时它是没有状态的不需要维持上次的选择状态和均衡因子。但是随着任务量的增大，它的效果趋向轮询后也会具有轮询算法的部分缺点；</li>
+<li>轮询分配：将任务分配给此时具有最小连接数的节点，因此它是动态负载均衡算法。一个节点收到一个任务后连接数就会加1，当节点故障时就将节点权值设置为0，不再给节点分配任务；</li>
+<li>最小连接分配：将任务分配给此时具有最小连接数的节点，因此它是动态负载均衡算法。一个节点收到一个任务后连接数就会加1，当节点故障时就将节点权值设置为0，不再给节点分配任务；</li>
+<li>hash分配：对请求中的关键信息进行hash计算，hash值相同的请求分配到同一台服务器，具体原理可查看HashMap分配原理；</li>
+<li>根据性能分配：根据服务器的响应时间来进行任务分配，优先将新任务分配给响应最快的服务器；</li>
+</ul>
+<h3 id="服务配置中心">服务配置中心</h3>
+<p>在分布式微服务意味着要将单体应用中的业务拆分成一个个子服务，每个服务的粒度相对较小，因此系统中会出现大量的服务。由于每个服务都需要必要的配置信息才能运行，所以一套集中式的、动态的配置管理设施是必不可少的。</p>
+<p>配置中心应运而生。配置中心，顾名思义，就是来统一管理项目中所有配置的系统。对于单机版，我们称之为配置文件；对于分布式集群系统，我们称之为配置中心。</p>
+<p>配置中心作用：</p>
+<ul>
+<li>统一管理不同环境、不同集群的配置；</li>
+<li>将配置与应用分离、解耦合；</li>
+<li>版本发布管理；</li>
+</ul>
+<h2 id="springcloud体系">SpringCloud体系</h2>
+<p>随着微服务模式的使用，服务之间的调用带来的问题有很多，例如：数据一致性、网络波动、缓存、事务等问题，针对这一系列的问题就要有对应的框架来解决，目前主流一站式微服务解决方案有<code>Spring Cloud</code>、<code>Spring Cloud Alibaba</code>。</p>
+<p><code>Spring Cloud</code>它并不是一个框架，而是很多个框架。它是分布式微服务架构的一站式解决方案，是多种微服务架构落地技术的集合体，俗称微服务全家桶。</p>
+<p><img alt="分布式架构-001" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-001.png"></p>
+<p><img alt="分布式架构-010" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-010.png"></p>
+<h3 id="eureka">Eureka</h3>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.jianshu.com/p/cb7fa0aa47a8">https://www.jianshu.com/p/cb7fa0aa47a8</a></li>
+</ul>
+<blockquote>
+<p>Eureka is a REST (Representational State Transfer) based service that is primarily used in the AWS cloud for locating services for the purpose of load balancing and failover of middle-tier servers。 We call this service， the Eureka Server。 Eureka also comes with a Java-based client component，the Eureka Client， which makes interactions with the service much easier。 The client also has a built-in load balancer that does basic round-robin load balancing。 &mdash;<a href="https://github.com/Netflix/eureka">https://github.com/Netflix/eureka</a></p>
+</blockquote>
+<p>大意：Eureka是一个REST (Representational State Transfer)服务，它主要用于AWS云，用于定位服务，以实现中间层服务器的负载平衡和故障转移，我们称此服务为Eureka服务器。Eureka也有一个基于java的客户端组件，Eureka客户端，这使得与服务的交互更加容易，同时客户端也有一个内置的负载平衡器，它执行基本的循环负载均衡。</p>
+<p>Eureka采用了Client / Server 的设计架构，提供了完整的服务注册和服务发现，可以和 Spring Cloud 无缝集成。Eureka Sever作为服务注册功能的服务器，它是服务注册中心。而系统中的其他微服务，使用Eureka的客户端连接到 Eureka Server并维持心跳连接。这样系统的维护人员就可以通过Eureka Server来监控系统中各个微服务是否正常运行。</p>
+<p><img alt="分布式架构-002" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-002.png"></p>
+<ul>
+<li>Eureka Server 提供服务注册服务；各个微服务节点通过配置启动后，会在EurekaServer中进行注册，这样EurekaServer中的服务注册表中将会存储所有可用服务节点的信息，服务节点的信息可以在界面中直观看到。</li>
+<li>Eureka Client 通过注册中心进行访问；它是一个Java客户端，用于简化Eureka Server的交互，客户端同时也具备一个内置的使用轮询负载算法的负载均衡器。在应用启动后，将会向Eureka Server发送心跳默认周期为30秒。如果Eureka Server在多个心跳周期内没有接收到某个节点的心跳，Eureka Server将会从服务注册表中把这个服务节点移除，默认90秒。
+<ul>
+<li>Service Provider：服务提供方，将自身服务注册到Eureka，从而使服务消费方能够找到；</li>
+<li>Service Consumer：服务消费方，从Eureka获取注册服务列表，从而能够消费服务；</li>
+</ul>
+</li>
+</ul>
+<p><strong>Eureka的自我保护机制：</strong></p>
+<p>默认情况下，如果Eureka Server在一定时间内（默认90秒）没有接收到某个微服务实例的心跳，Eureka Server将会移除该实例。但是当网络分区故障发生时，微服务与Eureka Server之间无法正常通信，而微服务本身是正常运行的，此时不应该移除这个微服务，所以引入了自我保护机制。</p>
+<blockquote>
+<p>自我保护模式正是一种针对网络异常波动的安全保护措施，使用自我保护模式能使Eureka集群更加的健壮、稳定的运行。</p>
+</blockquote>
+<p>如果在15分钟内超过85%的客户端节点都没有正常的心跳，那么Eureka就认为客户端与注册中心出现了网络故障，Eureka Server自动进入自我保护机制：</p>
+<ul>
+<li>Eureka Server不再从注册列表中移除因为长时间没收到心跳而应该过期的服务；</li>
+<li>Eureka Server仍然能够接受新服务的注册和查询请求，但是不会被同步到其它节点上，保证当前节点依然可用；</li>
+<li>当网络稳定时，当前Eureka Server新的注册信息会被同步到其它节点中；</li>
+</ul>
+<p>简而言之，某时刻某一个微服务不可用了，Eureka不会立刻清理，依旧会对该微服务的信息进行保存。所以Eureka属于<a href="https://blog.csdn.net/white_pure/article/details/119806058">AP</a>。</p>
+<h3 id="hystrix">Hystrix</h3>
+<p>当微服务系统的一个服务出现故障时，故障会沿着服务的调用链路在系统中疯狂蔓延，最终导致整个微服务系统的瘫痪，这就是“雪崩效应”。为了防止此类事件的发生，微服务架构引入了“断路器”的一系列服务容错和保护机制。</p>
+<blockquote>
+<p>&ldquo;断路器”本身是一种开关装置，当某个服务单元发生故障之后，通过断路器的故障监控（类似熔断保险丝)，向调用方返回一个符合预期的、可处理的备选响应（FallBack)，而不是长时间的等待或者抛出调用方无法处理的异常，这样就保证了服务调用方的线程不会被长时间、不必要地占用，从而避免了故障在分布式系统中的蔓延，乃至雪崩。</p>
+</blockquote>
+<p>&ldquo;断路器&quot;思想：<a href="https://martinfowler.com/bliki/CircuitBreaker.html">https://martinfowler.com/bliki/CircuitBreaker.html</a></p>
+<p>Spring Cloud Hystrix 是基于 Netflix 公司的开源组件 Hystrix 实现的，它提供了熔断器功能，能够有效地阻止分布式微服务系统中出现联动故障，以提高微服务系统的弹性。Spring Cloud Hystrix 具有服务降级、服务熔断、线程隔离、请求缓存、请求合并以及实时故障监控等强大功能。</p>
+<p>熔断机制是为了应对雪崩效应而出现的一种微服务链路保护机制。</p>
+<p>当微服务系统中的某个微服务不可用或响应时间太长时，为了保护系统的整体可用性，熔断器会暂时切断请求对该服务的调用，并快速返回一个友好的错误响应。这种熔断状态不是永久的，在经历了一定的时间后，熔断器会再次检测该微服务是否恢复正常，若服务恢复正常则恢复其调用链路。</p>
+<p><img alt="分布式架构-003" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-003.png"></p>
+<p>在熔断机制中涉及了三种熔断状态：</p>
+<ul>
+<li>熔断打开：请求不再进行调用当前服务，内部定时一般为MTTR(平均故障处理时间)，当打开时长达到所设的时长则进入半熔断状态；</li>
+<li>熔断半开：部分请求根据规则调用当前服务，如果请求成功且符合规则则认为当前服务恢复正常，关闭熔断；</li>
+<li>熔断关闭：熔断关闭不会对服务进行熔断；</li>
+</ul>
+<p>Hystrix 实现服务熔断的步骤如下：</p>
+<ol>
+<li>当服务的调用出错率达到或超过 Hystix 规定的比率（默认为 50%）后，熔断器进入熔断开启状态。</li>
+<li>熔断器进入熔断开启状态后，Hystrix 会启动一个休眠时间窗，在这个时间窗内，该服务的降级逻辑会临时充当业务主逻辑，而原来的业务主逻辑不可用。</li>
+<li>当有请求再次调用该服务时，会直接调用降级逻辑快速地返回失败响应，以避免系统雪崩。</li>
+<li>当休眠时间窗到期后，Hystrix 会进入半熔断转态，允许部分请求对服务原来的主业务逻辑进行调用，并监控其调用成功率。</li>
+<li>如果调用成功率达到预期，则说明服务已恢复正常，Hystrix 进入熔断关闭状态，服务原来的主业务逻辑恢复；否则 Hystrix 重新进入熔断开启状态，休眠时间窗口重新计时，继续重复第 2 到第 5 步。</li>
+</ol>
+<p><strong><a href="https://github.com/Netflix/Hystrix/wiki/How-it-Works#Flow">Hystrix工作流程</a>：</strong></p>
+<p><img alt="分布式架构-004" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-004.png"></p>
+<ol>
+<li>创建<code>HystrixCommand</code>或<code>HystrixObserableCommand</code>对象。</li>
+<li>命令执行:
+<ul>
+<li>其中<code>HystrixCommand</code>实现了下面前两种执行方式:
+<ul>
+<li><code>execute</code>：同步执行，从依赖的服务返回一个单一的结果对象或是在发生错误的时候抛出异常。</li>
+<li><code>queue</code>：异步执行，直接返回一个Future对象，其中包含了服务执行结束时要返回的单一结果对象。</li>
+</ul>
+</li>
+<li><code>HystrixObservableCommand</code>实现了后两种执行方式：
+<ul>
+<li><code>obseve()</code>：返回Observable对象，它代表了操作的多个结果，它是一个Hot Observable，不论“事件源”是否有“订阅者”，都会在创建后对事件进行发布，所以对于Hot Observable的每一个“订阅者”都有可能是从“事件源”的中途开始的，并可能只是看到了整个操作的局部过程。</li>
+<li><code>toObservable()</code>：同样会返回Observable对象，也代表了操作的多个结果，但它返回的是一个Cold Observable，没有“订间者”的时候并不会发布事件，而是进行等待，直到有“订阅者&quot;之后才发布事件，所以对于Cold Observable 的订阅者，它可以保证从一开始看到整个操作的全部过程。</li>
+</ul>
+</li>
+</ul>
+</li>
+<li>判断当前命令的请求缓存功能是被启用的，并且该命令缓存命中，那么缓存的结果会立即以Observable对象的形式返回。</li>
+<li>检查断路器是否为打开状态。如果断路器是打开的，那么Hystrix不会执行命令，而是转接到fallback处理逻辑(第8步)；如果断路器是关闭的，检查是否有可用资源来执行命令(第5步)。</li>
+<li>判断线程池/请求队列信号量是否占满。如果命令依赖服务的专有线程地和请求队列，或者信号量已经被占满，那么Hystrix也不会执行命令，而是转接到fallback处理理辑(第8步) 。</li>
+<li>Hystrix会根据我们编写的方法来决定采取什么样的方式去请求依赖服务:
+<ul>
+<li><code>HystrixCommand.run()</code>：返回一个单一的结果，或者抛出异常。</li>
+<li><code>HystrixObservableCommand.construct()</code>：返回一个Observable对象来发射多个结果，或通过onError发送错误通知。</li>
+</ul>
+</li>
+<li>Hystrix会将“成功”、“失败”、“拒绝”、“超时” 等信息报告给断路器，而断路器会维护一组计数器来统计这些数据。断路器会使用这些统计数据来决定是否要将断路器打开，来对某个依赖服务的请求进行&quot;熔断/短路&rdquo;。</li>
+<li>当命令执行失败的时候，Hystrix会进入fallback尝试回退处理，我们通常也称波操作为“服务降级”。而能够引起服务降级处理的情况有下面几种：
+<ul>
+<li>第4步∶当前命令处于“熔断/短路”状态，断路器是打开的时候。</li>
+<li>第5步∶当前命令的线程池、请求队列或者信号量被占满的时候。</li>
+<li>第6步∶<code>HystrixObsevableCommand.construct()</code>或<code>HytrixCommand.run()</code>抛出异常的时候。</li>
+</ul>
+</li>
+<li>当Hystrix命令执行成功之后，它会将处理结果直接返回或是以Observable的形式返回给调用方。</li>
+</ol>
+<h3 id="spring-cloud-gateway">Spring Cloud Gateway</h3>
+<p>Spring Cloud Gateway 属于 Spring Cloud 生态系统中的网关，其诞生的目标是为了替代老牌网关 Zuul。准确点来说，应该是 Zuul 1.x。Spring Cloud Gateway 起步要比 Zuul 2.x 更早。
+为了提升网关的性能，Spring Cloud Gateway 基于 Spring WebFlux 。Spring WebFlux 使用 Reactor 库来实现响应式编程模型，底层基于 Netty 实现同步非阻塞的 I/O。</p>
+<p><img alt="分布式架构-012" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-012.png"></p>
+<p>核心组件：</p>
+<ul>
+<li>Route - 路由是构建网关的基本模块，它由ID，目标URI，一系列的断言和过滤器组成，如断言为true则匹配该路由；</li>
+<li>Predicate - 断言参考的是Java8的<code>java.util.function。Predicate</code>，开发人员可以匹配HTTP请求中的所有内容，例如请求头或请求参数，如果请求与断言相匹配则进行路由；</li>
+<li>Filter - 过滤指的是Spring框架中GatewayFilter的实例，使用过滤器，可以在请求被路由前或者之后对请求进行修改；</li>
+</ul>
+<p><a href="https://spring.io/blog/2022/08/26/creating-a-custom-spring-cloud-gateway-filter">工作流程</a>：
+<img alt="分布式架构-013" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-013.png"></p>
+<ul>
+<li>路由判断：客户端的请求到达网关后，先经过 Gateway Handler Mapping 处理，这里面会做断言（Predicate）判断，看下符合哪个路由规则，这个路由映射后端的某个服务。</li>
+<li>请求过滤：然后请求到达 Gateway Web Handler，这里面有很多过滤器，组成过滤器链（Filter Chain），这些过滤器可以对请求进行拦截和修改，比如添加请求头、参数校验等等，有点像净化污水。然后将请求转发到实际的后端服务。这些过滤器逻辑上可以称作 Pre-Filters，Pre 可以理解为“在&hellip;之前”。</li>
+<li>服务处理：后端服务会对请求进行处理。</li>
+<li>响应过滤：后端处理完结果后，返回给 Gateway 的过滤器再次做处理，逻辑上可以称作 Post-Filters，Post 可以理解为“在&hellip;之后”。</li>
+<li>响应返回：响应经过过滤处理后，返回给客户端。</li>
+</ul>
+<p>客户端的请求先通过匹配规则找到合适的路由，就能映射到具体的服务。然后请求经过过滤器处理后转发给具体的服务，服务处理后，再次经过过滤器处理，最后返回给客户端。</p>
+<p>对于公司业务以 Java 为主要开发语言的情况下，Spring Cloud Gateway 通常是个不错的选择，其优点有：简单易用、成熟稳定、与 Spring Cloud 生态系统兼容、Spring 社区成熟等等。
+不过，Spring Cloud Gateway 也有一些局限性和不足之处， 一般还需要结合其他网关一起使用比如 OpenResty。
+并且，其性能相比较于 Kong 和 APISIX，还是差一些。如果对性能要求比较高的话，Spring Cloud Gateway 不是一个好的选择。</p>
+<h3 id="openfeign">OpenFeign</h3>
+<blockquote>
+<p>Feign is a declarative web service client。 It makes writing web service clients easier。 To use Feign create an interface and annotate it。 It has pluggable annotation support including Feign annotations and JAX-RS annotations。 Feign also supports pluggable encoders and decoders。 Spring Cloud adds support for Spring MVC annotations and for using the same HttpMessageConverters used by default in Spring Web。 Spring Cloud integrates Ribbon and Eureka， as well as Spring Cloud LoadBalancer to provide a load-balanced http client when using Feign。</p>
+</blockquote>
+<p>大意：Feign是一个声明式WebService客户端。使用Feign能让编写Web Service客户端更加简单。它的使用方法是定义一个服务接口然后在上面添加注解。Feign也支持可拔插式的编码器和解码器。Spring Cloud对Feign进行了封装，使其支持了Spring MVC标准注解和HttpMessageConverters。Feign可以与Eureka和Ribbon组合使用以支持负载均衡。</p>
+<p>Feign和OpenFeign:</p>
+<ul>
+<li>Feign是Spring Cloud组件中的一个轻量级RESTful的HTTP服务客户端Feign内置了Ribbon，用来做客户端负载均衡，去调用服务注册中心的服务。Feign的使用方式是:使用Feign的注解定义接口，调用这个接口，就可以调用服务注册中心的服务；</li>
+<li>OpenFeign是Spring Cloud在Feign的基础上支持了SpringMVC的注解，如@RequesMapping等等。OpenFeign的@Feignclient可以解析SpringMVc的@RequestMapping注解下的接口，并通过动态代理的方式产生实现类，实现类中做负载均衡并调用其他服务；</li>
+</ul>
+<p>通过使用<code>OpenFeign</code>可以使代码变得更加简洁，减轻程序员负担：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> // 伪代码
+</span></span><span class="line"><span class="cl"> @Component
+</span></span><span class="line"><span class="cl"> // 括号中，为在注册中心注册的服务名称
+</span></span><span class="line"><span class="cl"> @FeignClient(&#34;CLOUD-PAYMENT-SERVICE&#34;)
+</span></span><span class="line"><span class="cl"> public interface PaymentFeignService {
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">     @GetMapping(&#34;/payment/get/{id}&#34;)
+</span></span><span class="line"><span class="cl">     CommonResult&lt;Payment&gt; getPayment(@PathVariable(&#34;id&#34;) Long id);
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">     @PostMapping(&#34;/payment/timeout&#34;)
+</span></span><span class="line"><span class="cl">     String feignTimeoutTest();
+</span></span><span class="line"><span class="cl"> }
+</span></span></code></pre></div><p>openFeign工作原理：</p>
+<p><img alt="分布式架构-008" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-008.png"></p>
+<ol>
+<li>使用注解<code>@FeignClient</code>注册<code>FactoryBean</code>到IOC容器， 最终产生了一个虚假的实现类代理;</li>
+<li>使用Feign调用接口的地方，最终拿到的都是一个假的代理实现类；</li>
+<li>所有发生在代理实现类上的调用，都被转交给Feign框架，翻译成HTTP的形式发送出去，并得到返回结果，再翻译回接口定义的返回值形式；</li>
+</ol>
+<h3 id="ribbon">Ribbon</h3>
+<p>Spring Cloud Ribbon是基于Netflix Ribbon实现的一套客户端负载均衡的工具，是一个内置软件负载平衡器的进程间通信（远程过程调用）库。主要功能是提供客户端的软件负载均衡算法和服务调用。Ribbon客户端组件提供一系列完善的配置项，如连接超时、重试等。</p>
+<p>本地负载与服务端负载：</p>
+<ul>
+<li>Nginx是服务器负载均衡，客户端所有请求都会交给nginx，然后由nginx实现转发请求。即负载均衡是由服务端实现的；</li>
+<li>Ribbon是本地负载均衡，在调用微服务接口时候，会在注册中心上获取注册信息服务列表之后缓存到JVM本地，从而在本地实现RPC远程服务调用技术；</li>
+</ul>
+<p>Ribbon其实是一个软负载均衡的客户端组件，它可以和其他所需请求的客户端结合使用，例如与Eureka结合：</p>
+<p><img alt="分布式架构-007" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-007.png"></p>
+<p>消费方和服务方在注册中心注册服务，当消费方发起请求时，Ribbon会去注册中心寻找请求的服务名，即服务方集群，Ribbon默认负载算法会根据<code>接口第几次请求 % 服务器集群总数量</code>算出实际消费方服务器的位置，每次服务重启动后rest接口计数从1开始。</p>
+<p>模拟Ribbon默认负载均衡算法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public interface ILoadBalance {
+</span></span><span class="line"><span class="cl">    ServiceInstance instance(List&lt;ServiceInstance&gt; instances); 
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">@Component
+</span></span><span class="line"><span class="cl">public class MyLoadBalance implements ILoadBalance{
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    /**
+</span></span><span class="line"><span class="cl">     * 轮询索引
+</span></span><span class="line"><span class="cl">     */
+</span></span><span class="line"><span class="cl">    private final AtomicInteger index = new AtomicInteger(0);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    /**
+</span></span><span class="line"><span class="cl">     * 负载均衡算法：rest接口第几次请求数 % 服务器集群总数量 = 实际调用服务器位置下标，每次服务重启动后rest接口计数从1开始。
+</span></span><span class="line"><span class="cl">     * @param instances 服务器集群数量
+</span></span><span class="line"><span class="cl">     * @return 实际服务器的下标
+</span></span><span class="line"><span class="cl">     */
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    public ServiceInstance instance(List&lt;ServiceInstance&gt; instances) {
+</span></span><span class="line"><span class="cl">        return instances.get(incrementAndGet() % instances.size());
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public final int incrementAndGet() {
+</span></span><span class="line"><span class="cl">        int current = 0;
+</span></span><span class="line"><span class="cl">        int next = 0;
+</span></span><span class="line"><span class="cl">        do {
+</span></span><span class="line"><span class="cl">            current = index.get();
+</span></span><span class="line"><span class="cl">            // 当最大数量超过 Integer。MAX_VALUE 归0
+</span></span><span class="line"><span class="cl">            next = current &gt;= 2147483647 ? 0 : current + 1;
+</span></span><span class="line"><span class="cl">        }while (!index.compareAndSet(current，next));
+</span></span><span class="line"><span class="cl">        return next;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private RestTemplate restTemplate;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private DiscoveryClient discoveryClient;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> @Resource
+</span></span><span class="line"><span class="cl"> private ILoadBalance iLoadBalance;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> @GetMapping(&#34;/myLoadBalance&#34;)
+</span></span><span class="line"><span class="cl"> public String myLoadBalanceTest() {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     List&lt;ServiceInstance&gt; instances = discoveryClient.getInstances(&#34;CLOUD-PAYMENT-SERVICE&#34;);
+</span></span><span class="line"><span class="cl">     ServiceInstance instance = iLoadBalance.instance(instances);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     URI uri = instance.getUri();
+</span></span><span class="line"><span class="cl">     String finalUri = String.format(&#34;%s/%s&#34;， uri， PaymentConstant。PAYMENT_GETPORT_API);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     log.info(&#34;自定义负载均衡，请求地址：{}&#34;， finalUri);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     return restTemplate.getForObject(finalUri， String.class);
+</span></span><span class="line"><span class="cl"> }
+</span></span></code></pre></div><h3 id="springcloud-config">SpringCloud Config</h3>
+<p>参考文章：</p>
+<ul>
+<li><a href="https://www.springcloud.cc/spring-cloud-config.html">https://www.springcloud.cc/spring-cloud-config.html</a></li>
+<li><a href="https://cloud.spring.io/spring-cloud-static/spring-cloud-config/2.2.1.RELEASE/reference/html">https://cloud.spring.io/spring-cloud-static/spring-cloud-config</a></li>
+</ul>
+<p>SpringCloud Config为微服务架构中的微服务提供集中化的外部配置支持，配置服务器为各个不同微服务应用的所有环境提供了一个中心化的外部配置。</p>
+<p><img alt="分布式架构-009" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-009.png"></p>
+<p><code>SpringCloud Config</code>是配置中心的一种，它分为服务端和客户端两部分：</p>
+<ul>
+<li>服务端也称为分布式配置中心，它是一个独立的微服务应用，用来连接配置服务器并为客户端提供获取配置信息，加密/解密信息等访问接口；Config-Server端集中式存储/管理配置文件，并对外提供接口方便Config-Client访问，接口使用HTTP的方式对外提供访问；</li>
+<li>客户端则是通过指定的配置中心来管理应用资源，以及与业务相关的配置内容，并在启动的时候从配置中心获取和加载配置信息配置服务器默认采用git来存储配置信息，这样就有助于对环境配置进行版本管理，并且可以通过git客户端工具来方便的管理和访问配置内容；</li>
+</ul>
+<p>使用<code>SpringCloud Config</code>非常简单，需要在服务端和客户端分别进行改造：</p>
+<ol>
+<li>引入依赖就不说了，首先将分布式中系统中的配置放到git或svn上，在服务端配置文件里配置好git或svn用户名密码、配置文件所在的分支及配置文件的目录，再将服务端启动类加上<code>@EnableConfigServer</code>注解，就大功告成了；</li>
+<li>放在git或svn上的配置文件名称要符合规则，才能通过配置中心访问得到该文件。一些常用的配置文件规则，其中，label：分支、profiles：环境(dev/test/prod)、application：服务名：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> ## http://127.0.0.1:3344/master/config-dev.yml
+</span></span><span class="line"><span class="cl"> 1. /{label}/{application}-{profile}.yml
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> ## http://127.0.0.1:3344/config-dev.yml
+</span></span><span class="line"><span class="cl"> 2. /{application}-{profile}.yml
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> ## http://127.0.0.1:3344/config/dev/master
+</span></span><span class="line"><span class="cl"> 3. /{application}/{profile}[/{label}]
+</span></span></code></pre></div></li>
+<li>在客户端也要引入依赖和进行相关配置：配置中心地址、分支名称、配置文件名称、环境，需要注意的是要将客户端模块下的<code>application.yml</code>文件改为<code>bootstrap.yml</code>，再将主启动类加上<code>@EnableEurekaClient</code>注解；
+<blockquote>
+<p>当配置客户端启动时，它绑定到配置服务器(通过spring.cloud.config.uri引导配置属性)，并使用远程属性源初始化Spring Environment。
+这种行为的最终结果是，所有想要使用Config Server的客户端应用程序都需要bootstrap.yml或一个环境变量</p>
+<p>applicaiton.yml是用户级的资源配置项，而bootstrap.yml是系统级的，优先级更加高，在加载配置时优先加载bootstrap.yml</p>
+</blockquote>
+</li>
+</ol>
+<p>当将<code>SpringCloud Config</code>客户端服务端都配置好之后，修改配置时会发现修改的配置文件不能实时生效；针对这个问题，可以将服务重启或者调用<code>actuator</code>的刷新接口使其生效，使用之前需要引入<code>actuator</code>的依赖：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> # 使用SpringCloud Config修改完配置后，调用刷新接口使客户端配置生效
+</span></span><span class="line"><span class="cl"> curl -X POST &#34;http://localhost:3355/actuator/refresh&#34;
+</span></span></code></pre></div><p>为了避免手动的调用刷新接口，可以使用<code>SpringCloud Bus</code>配合<code>SpringCloud Config</code>实现配置的动态刷新。</p>
+<h3 id="springboot">SpringBoot</h3>
+<p>长期以来Java的开发一直让人所诟病，项目开发复杂度极其高、项目的维护非常困难；即便使用了大量的开发框架，发现我们的开发也没少多少。为了解决让开发更佳简单，项目更容易管理，<code>SpringBoot</code>诞生了。
+<code>SpringBoot</code>是一个广泛用来构建Java微服务的框架，它基于Spring依赖注入框架来进行工作。</p>
+<p>官网地址：<a href="https://spring.io/projects/spring-boot">https://spring.io/projects/spring-boot</a></p>
+<blockquote>
+<p><code>SpringBoot</code>是由<code>Pivotal</code>团队提供的全新框架，其设计目的是用来简化新<code>Spring</code>应用的初始搭建以及开发过程。
+该框架使用了特定的方式来进行配置，从而使开发人员不再需要定义样板化的配置。<code>SpringBoot</code> 提供了一种新的编程范式，可以更加快速便捷地开发 <code>Spring</code> 项目，在开发过程当中可以专注于应用程序本身的功能开发，而无需在 <code>Spring</code> 配置上花太大的工夫。</p>
+</blockquote>
+<p><code>SpringBoot</code> 基于 <code>Sring4</code> 进行设计，继承了原有 <code>Spring</code> 框架的优秀基因。
+<code>SpringBoot</code> 准确的说并不是一个框架，而是一些类库的集合。
+<code>maven</code> 或者 <code>gradle</code> 项目导入相应依赖即可使用 <code>SpringBoot</code>，而无需自行管理这些类库的版本。</p>
+<p>特点：</p>
+<ul>
+<li>独立运行的 <code>Spring</code> 项目：
+<code>SpringBoot</code> 可以以 jar 包的形式独立运行，运行一个 <code>SpringBoot</code> 项目只需通过 <code>java–jar xx.jar</code> 来运行。</li>
+<li>内嵌 <code>Servlet</code> 容器：
+<code>SpringBoot</code> 可选择内嵌 <code>Tomcat</code>、<code>Jetty</code> 或者 <code>Undertow</code>，这样我们无须以 <code>war</code> 包形式部署项目。</li>
+<li>提供 <code>starter</code> 简化 <code>Maven</code> 配置：
+<code>Spring</code> 提供了一系列的 <code>starter</code> pom 来简化 <code>Maven</code> 的依赖加载，例如，当你使用了<code>spring-boot-starter-web</code> 时，会自动加入依赖包。</li>
+<li>自动配置 <code>Spring</code>：
+<code>SpringBoot</code> 会根据在类路径中的 jar 包、类，为 jar 包里的类自动配置 Bean，这样会极大地减少我们要使用的配置。当然，<code>SpringBoot</code> 只是考虑了大多数的开发场景，并不是所有的场景，若在实际开发中我们需要自动配置 <code>Bean</code>，而 <code>SpringBoot</code> 没有提供支持，则可以自定义自动配置。</li>
+<li>准生产的应用监控：
+<code>SpringBoot</code> 提供基于 <code>http、ssh、telnet</code> 对运行时的项目进行监控。</li>
+<li>无代码生成和 xml 配置：
+<code>SpringBoot</code> 的神奇的不是借助于代码生成来实现的，而是通过条件注解来实现的，这是 <code>Spring 4.x</code> 提供的新特性。<code>Spring 4.x</code> 提倡使用 Java 配置和注解配置组合，而 <code>SpringBoot</code> 不需要任何 xml 配置即可实现 <code>Spring</code> 的所有配置。</li>
+</ul>
+<h2 id="dubbo体系">Dubbo体系</h2>
+<p>Apache Dubbo 是一款易用、高性能的 WEB 和 RPC 框架，同时为构建企业级微服务提供服务发现、流量治理、可观测、认证鉴权等能力、工具与最佳实践。
+官网：<a href="https://cn.dubbo.apache.org/zh-cn/">https://cn.dubbo.apache.org/zh-cn/</a></p>
+<p>Dubbo 不光可以帮助我们调用远程服务，还提供了一些其他开箱即用的功能比如智能负载均衡。</p>
+<p>Dubbo工作原理:</p>
+<p>从下至上分为十层，各层均为单向依赖。左边淡蓝背景的为服务消费方使用的接口，右边淡绿色背景的为服务提供方使用的接口，位于中轴线上的为双方都用到的接口。</p>
+<p><img alt="分布式架构-014" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E6%9E%B6%E6%9E%84-014.png"></p>
+<ul>
+<li>config 配置层：Dubbo 相关的配置。支持代码配置，同时也支持基于 Spring 来做配置，以 ServiceConfig, ReferenceConfig 为中心</li>
+<li>proxy 服务代理层：调用远程方法像调用本地的方法一样简单的一个关键，真实调用过程依赖代理类，以 ServiceProxy 为中心。</li>
+<li>registry 注册中心层：封装服务地址的注册与发现。</li>
+<li>cluster 路由层：封装多个提供者的路由及负载均衡，并桥接注册中心，以 Invoker 为中心。</li>
+<li>monitor 监控层：RPC 调用次数和调用时间监控，以 Statistics 为中心。</li>
+<li>protocol 远程调用层：封装 RPC 调用，以 Invocation, Result 为中心。</li>
+<li>exchange 信息交换层：封装请求响应模式，同步转异步，以 Request, Response 为中心。</li>
+<li>transport 网络传输层：抽象 mina 和 netty 为统一接口，以 Message 为中心。</li>
+<li>serialize 数据序列化层：对需要在网络传输的数据进行序列化。</li>
+</ul>
+<h3 id="zookeeper">ZooKeeper</h3>
+<p>Dubbo是个微服务整体架构的框架，提供的功能包括服务注册发现，远程调用，监控等等，对标的项目大概是spring cloud。Dubbo的服务发现模块基于zookeeper实现。</p>
+<p>ZooKeeper 是一个开源的分布式协调服务，它的设计目标是将那些复杂且容易出错的分布式一致性服务封装起来，构成一个高效可靠的原语集，并以一系列简单易用的接口提供给用户使用。</p>
+<ul>
+<li>ZooKeeper 本身就是一个分布式程序（只要半数以上节点存活，ZooKeeper 就能正常服务）。</li>
+<li>为了保证高可用，最好是以集群形态来部署 ZooKeeper，这样只要集群中大部分机器是可用的（能够容忍一定的机器故障），那么 ZooKeeper 本身仍然是可用的。</li>
+<li>ZooKeeper 将数据保存在内存中，这也就保证了 高吞吐量和低延迟（但是内存限制了能够存储的容量不太大，此限制也是保持 znode 中存储的数据量较小的进一步原因）。</li>
+<li>ZooKeeper 是高性能的。 在“读”多于“写”的应用程序中尤其地明显，因为“写”会导致所有的服务器间同步状态。（“读”多于“写”是协调服务的典型场景。）ZooKeeper 有临时节点的概念。</li>
+<li>当创建临时节点的客户端会话一直保持活动，瞬时节点就一直存在。而当会话终结时，瞬时节点被删除。持久节点是指一旦这个 znode 被创建了，除非主动进行 znode 的移除操作，否则这个 znode 将一直保存在 ZooKeeper 上。</li>
+<li>ZooKeeper 底层其实只提供了两个功能：① 管理（存储、读取）用户程序提交的数据；② 为用户程序提供数据节点监听服务。</li>
+</ul>
+<h2 id="springcloud-alibaba体系">SpringCloud Alibaba体系</h2>
+<p>Spring Cloud Alibaba 致力于提供微服务开发的一站式解决方案。此项目包含开发分布式应用服务的必需组件，方便开发者通过 Spring Cloud 编程模型轻松使用这些组件来开发分布式应用服务。</p>
+<h3 id="nacos">Nacos</h3>
+<p>Nacos 是一个 Alibaba 开源的、易于构建云原生应用的动态服务发现、配置管理和服务管理平台。
+使用 Spring Cloud Alibaba Nacos Discovery，可基于 Spring Cloud 的编程模型快速接入 Nacos 服务注册功能。</p>
+<h3 id="sentinel">Sentinel</h3>
+<p>随着微服务的流行，服务和服务之间的稳定性变得越来越重要。 Sentinel 以流量为切入点，从流量控制、熔断降级、系统负载保护等多个维度保护服务的稳定性。</p>
+<p>Sentinel 具有以下特征:</p>
+<ul>
+<li>丰富的应用场景： Sentinel 承接了阿里巴巴近 10 年的双十一大促流量的核心场景，例如秒杀（即突发流量控制在系统容量可以承受的范围）、消息削峰填谷、实时熔断下游不可用应用等。</li>
+<li>完备的实时监控： Sentinel 同时提供实时的监控功能。您可以在控制台中看到接入应用的单台机器秒级数据，甚至 500 台以下规模的集群的汇总运行情况。</li>
+<li>广泛的开源生态： Sentinel 提供开箱即用的与其它开源框架/库的整合模块，例如与 Spring Cloud、Dubbo、gRPC 的整合。您只需要引入相应的依赖并进行简单的配置即可快速地接入 Sentinel。</li>
+<li>完善的 SPI 扩展点： Sentinel 提供简单易用、完善的 SPI 扩展点。您可以通过实现扩展点，快速的定制逻辑。例如定制规则管理、适配数据源等。</li>
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+                <a class="nav-link text-left" href="#%e6%9c%ac%e5%9c%b0%e4%ba%8b%e5%8a%a1">
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+                    分布式事务产生场景
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cap%e7%90%86%e8%ae%ba">
+                    CAP理论
+                </a>
+            </li>
+            
+            
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+        
+        </ul>
+        
+        </ul>
+        
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+        
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%90%86%e8%a7%a3cap">
+                    理解CAP
+                </a>
+            </li>
+            
+            
+        </ul>
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+        </ul>
+        
+        </ul>
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cap%e7%bb%84%e5%90%88%e6%96%b9%e5%bc%8f">
+                    CAP组合方式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#base%e7%90%86%e8%ae%ba">
+                    BASE理论
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-2pc">
+                    分布式事务解决方案-2PC
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af2pc">
+                    什么是2PC
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#xa%e6%96%b9%e6%a1%88">
+                    XA方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#seata%e6%96%b9%e6%a1%88">
+                    Seata方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-tcc">
+                    分布式事务解决方案-TCC
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%aftcc">
+                    什么是TCC
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-1">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-%e5%8f%af%e9%9d%a0%e6%b6%88%e6%81%af%e6%9c%80%e7%bb%88%e4%b8%80%e8%87%b4%e6%80%a7">
+                    分布式事务解决方案-可靠消息最终一致性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af%e5%8f%af%e9%9d%a0%e6%b6%88%e6%81%af%e6%9c%80%e7%bb%88%e4%b8%80%e8%87%b4%e6%80%a7">
+                    什么是可靠消息最终一致性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-2">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%ac%e5%9c%b0%e6%b6%88%e6%81%af%e8%a1%a8%e6%96%b9%e6%a1%88">
+                    本地消息表方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#rocketmq%e4%ba%8b%e5%8a%a1%e6%b6%88%e6%81%af%e6%96%b9%e6%a1%88">
+                    RocketMQ事务消息方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e4%ba%8b%e5%8a%a1%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-%e6%9c%80%e5%a4%a7%e5%8a%aa%e5%8a%9b%e9%80%9a%e7%9f%a5">
+                    分布式事务解决方案-最大努力通知
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%80%e4%b9%88%e6%98%af%e6%9c%80%e5%a4%a7%e5%8a%aa%e5%8a%9b%e9%80%9a%e7%9f%a5">
+                    什么是最大努力通知
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88-3">
+                    解决方案
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e6%a1%881">
+                    方案1
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%96%b9%e6%a1%882">
+                    方案2
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%86%e5%b8%83%e5%bc%8f%e8%a7%a3%e5%86%b3%e6%96%b9%e6%a1%88%e5%af%b9%e6%af%94">
+                    分布式解决方案对比
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
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+        <div class="nav_container animated fadeInDown">
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+        <div class="site_title">
+            <h1>
+                <a href="https://whiteppure.github.io/iblog/">
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+                        <h2 id="post_single_title">分布式事务详解</h2>
+                        <span id="post_page_title_date" class="date">2021.08.02</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
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+                    </div>
+                    <div class="post_content markdown"><h2 id="基础概念">基础概念</h2>
+<h3 id="什么是事务">什么是事务</h3>
+<p>什么是事务？举个例子：你去超市买东西，&ldquo;一手交钱，一手交货&quot;就是一个事务的例子。
+交钱和交货必须同时成功，事务才算成功，其中有一个环节失败，事务将会撤销所有已成功的活动。</p>
+<p>所以事务可以看作是一次重大的活动，它由不同的小活动组成，这些活动要么全部成功，要么全部失败。</p>
+<h3 id="本地事务">本地事务</h3>
+<p>在计算机系统中，更多的是通过关系型数据库来控制事务，这是利用数据库本身的事务特性来实现的，因此叫做数据库事务。
+由于应用程序主要靠关系型数据库来控制事务，而数据库通常和应用在同一个服务器上，所以基于关系型数据库的事务又叫做本地事务。</p>
+<p>数据库事务的四大特性：ACID：</p>
+<ul>
+<li>A（Atomic）：原子性，构成事务的所有操作，要么都执行完，要么全不执行，不可能出现部分成功部分失败的情况。</li>
+<li>C（Consistency）：一致性，在事务执行前后，数据库的一致性约束没有被破坏。比如：张三向李四转100元，转账前和转账后的数据正确状态这叫一致性，如果出现张三转100元，李四账户没有增加100元这就出现了数据错误，就没有达到一致性。</li>
+<li>I（Isolation）：隔离性，数据库中事务都是并发的，隔离性是指并发的两个事务的执行互不干扰，一个事务不能看到其他事务运行过程的中间状态。通过配置事务的隔离级别可以避免脏读、重复读等问题。</li>
+<li>D（Durability）：持久性，事务执行完毕后，该事务对数据的更改会被持久化到数据库，且不会被回滚。</li>
+</ul>
+<p>数据库事务在实现时，会将一次事务涉及的所有操作全部纳入到一个不可分割的执行单元，该执行单元中的所有操作要么都成功，要么都失败，只要其中任一操作执行失败，都将会导致事务回滚。</p>
+<h3 id="分布式事务">分布式事务</h3>
+<p>随着互联网的发展，软件系统由原来的单体应用转变为分布式应用。分布式系统会把一个应用系统拆分为多个可独立部署的程序，因此需要服务与服务之间的远程协作才能完成事务操作，这种分布式系统环境下由不同服务之间通过网络协作完成的事务被称为分布式事务。
+例如：用户注册送积分事务、创建订单减少库存、银行转账事务。</p>
+<p>本地事务与分布式事务理解：</p>
+<p>1.本地事务：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">begin transation;
+</span></span><span class="line"><span class="cl">// 1.本地数据库操作：张三减少金额
+</span></span><span class="line"><span class="cl">// 2.本地数据库操作：李四增加金额
+</span></span><span class="line"><span class="cl">commit transation;
+</span></span></code></pre></div><p>2.分布式事务：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">begin transation;
+</span></span><span class="line"><span class="cl">// 1.本地数据库操作：张三减少金额
+</span></span><span class="line"><span class="cl">// 2.远程调用：李四增加金额
+</span></span><span class="line"><span class="cl">commit transation;
+</span></span></code></pre></div><p>在<code>2.分布式事务</code>中如果李四增加金额成功，但是由于网络原因，远程调用并没有返回，此时本地事务提交失败就会回滚张三减少金额的操作，此时张三李四的金额就不一致了。</p>
+<p>因此在分布式架构的基础上，传统数据库事务就无法使用了，张三和李四的账户不在同一个数据库中甚至不在一个系统中，实现转账事务需要通过远程调用，由于网络的问题就会导致分布式事务的问题。</p>
+<h3 id="分布式事务产生场景">分布式事务产生场景</h3>
+<ol>
+<li>
+<p>最典型的是微服务架构，微服务之间通过远程调用完成事务操作。比如：订单微服务和库存微服务，下单的同时订单微服务请求库存微服务减少库存。简而言之，就是跨JVM进程产生的分布式事务。</p>
+</li>
+<li>
+<p>单体系统访问多个数据库实例，就会产生分布式事务。比如：用户和订单信息分别存储在两个MySQL中，用户管理系统删除用户信息，需要分别删除用户信息及用户的订单信息，由于数据分布在不同的数据库，就需要通过不同的数据库连接去操作数据，此时产生分布式事务。</p>
+</li>
+<li>
+<p>多个微服务访问同一个数据库实例。比如：订单微服务和库存微服务即使访问同一个数据库也会产生分布式事务，原因是跨JVM进程，两个微服务持有了不同的数据库连接进行数据库操作，此时产生分布式事务。</p>
+</li>
+</ol>
+<h2 id="分布式事务基础理论">分布式事务基础理论</h2>
+<p>分布式事务之所以叫做分布式事务，是因为提供服务的各个结点分布在不同的机器上，相互之间通过网络交互。不能因为有网络问题就导致整个系统无法提供服务，网络因素成了分布式事务的考量标准之一。因此，分布式事务需要更进一步的理论支持。</p>
+<h3 id="cap理论">CAP理论</h3>
+<p>CAP是Consistency、Availability、Partition tolerance三个词语的缩写，分别表示一致性、可用性、分区容忍性。</p>
+<h4 id="理解cap">理解CAP</h4>
+<p>为了方便对CAP理论的理解，结合电商系统中的一些业务场景来理解CAP；如下图是商品信息管理的执行流程：</p>
+<p><img alt="分布式事务-001" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-001.png"></p>
+<p>整体执行流程：</p>
+<ul>
+<li>商品服务请求主数据库写入商品信息（增、删、改）</li>
+<li>主数据库向商品服务响应写入成功</li>
+<li>商品服务请求从数据库获取商品信息</li>
+</ul>
+<p><strong>C-Consistency：</strong>
+一致性是指写操作后的读操作可以读取到最新的数据状态，当数据分布在多个结点上，从任意结点读取到的数据都是最新状态。</p>
+<p>上图中，商品的信息的读写要满足一致性就是要实现如下目标：</p>
+<ul>
+<li>商品服务写入主数据库成功，则向从数据查询新数据也成功</li>
+<li>商品服务写入主数据库失败，则向从数据查询新数据也失败</li>
+</ul>
+<p>这里一致性指的就是主从数据库数据的一致性。</p>
+<p>如何实现一致性：</p>
+<ul>
+<li>写入主数据库后要将数据<strong>同步</strong>到从数据库</li>
+<li>写入主数据库后，在向从数据库同步期间要将从数据库数据锁定，待同步完成后在释放锁，以免在新数据写入成功之后，向从数据库查询到旧数据库的数据</li>
+</ul>
+<p>分布式系统一致性的特点：</p>
+<ul>
+<li>由于存在数据库同步的过程中，写操作的响应会有一定的延迟</li>
+<li>为了保证数据一致性会对资源暂时锁定，待数据同步完成后释放锁定的资源</li>
+</ul>
+<p><strong>A-Availability:</strong>
+可用性是指任何事务操作都可以获得响应结果，且不会出现响应超时或响应错误。</p>
+<p>上图中，商品信息的读取满足可用性就是要实现如下目标：</p>
+<ul>
+<li>从数据库接收到数据查询的请求则立即能够响应数据的查询结果</li>
+<li>从数据库不允许出现响应超时或响应错误的情况</li>
+</ul>
+<p>如何实现可用性：</p>
+<ul>
+<li>写入主数据库后要将数据数据同步到从数据库</li>
+<li>由于要保证从数据库的可用性，不可将从数据库中的资源进行锁定</li>
+<li>即使数据还没有从主数据库同步过来，从数据库也要返回查询的数据，哪怕是旧数据，如果连旧数据也没有则可以按照约定返回一个默认信息，但不能返回错误或超时</li>
+</ul>
+<p>分布式系统可用性的特点：</p>
+<ul>
+<li>所有请求都要有响应，且不会出现响应超时或响应错误</li>
+</ul>
+<p><strong>P-Partition tolerance:</strong>
+分布式系统的各个结点部署在不同的子网，这就是网络分区，不可避免的会出现由于网络问题而导致结点之间的通信失败，此时仍可以对外提供服务，这就是分区容忍性。</p>
+<p>上图中，商品信息的读写满足分区容忍性就是要实现如下目标：</p>
+<ul>
+<li>主数据库向从数据库同步数据失败，不影响读写操作</li>
+<li>其中一个结点挂掉不影响另外一个结点提供服务</li>
+</ul>
+<p>如何实现分区容忍性：</p>
+<ul>
+<li>尽量使用异步取代同步操作，例如使用异步的方法将数据从数据库同步到从数据库，这样的结点之间才能有效的解耦合</li>
+<li>添加从数据库结点，其中一个从数据结点挂掉其他从结点来提供服务</li>
+</ul>
+<p>分布式分区容忍性特点：</p>
+<ul>
+<li>分区容忍性是分布式系统具备的基本的能力</li>
+</ul>
+<h4 id="cap组合方式">CAP组合方式</h4>
+<p>在所有分布式事务场景中不会同时具备CAP三个特征，因为在具备了P的前提下C和A是不能共存的。</p>
+<p>例如，下图满足了P分区容忍性</p>
+<p><img alt="分布式事务-001" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-001.png"></p>
+<p>上图分区容忍性含义：</p>
+<ul>
+<li>主数据库通过网络向从数据库同步数据，可以认为是主从数据库部署在不同的网络分区，通过网络进行交互</li>
+<li>当主数据库和从数据库之间网络出现问题，不影响主数据库和从数据库对外提供服务</li>
+<li>其中一台结点挂掉后，不影响另外一个结点对外提供服务</li>
+</ul>
+<p>在分区容忍性存在的前提下，一致性和可用性存在矛盾：</p>
+<ul>
+<li>如果要实现 <strong>(C)一致性</strong> ,则必须保证数据一致性，在数据同步的时候防止向从数据库查询不一致的数据则需要将从数据库数据锁定，待同步完成后解锁，如果同步失败，从数据库必须要返回错误信息或者超时信息。</li>
+<li>如果要实现 <strong>(A)可用性</strong> 则必须保证数据可用性，即不管任何时候都可以向从数据库查询数据，且不会响应超时信息或错误信息。</li>
+</ul>
+<p>在分布式的环境下，一致性和可用性只能存在一种，即AP、CP。</p>
+<ul>
+<li>AP：放弃一致性，追求分区容忍性和可用性。这是很多分布式系统设计时的选择。</li>
+<li>CP：放弃可用性，追求一致性和分区容忍性。zookeeper就是一个追求强一致性的例子；例如，跨行转账，一次转账请求需要等待双方银行都完成整个事务才算完成。</li>
+</ul>
+<p>如果不在分布式的环境下，一致性和可用性其实是不矛盾的：</p>
+<ul>
+<li>CA：放弃分区容忍性，即不进行分区，不考虑网络结点不通畅或者结点挂掉的情况，则可以实现一致性和可用性。那么系统将不是一个标准的分布式系统，最常用的关系型数据库就满足了CA。</li>
+</ul>
+<p>CAP是一个已经被证实的理论：一个分布式系统最多只能同时满足一致性、可用性、分区容忍性中的两种。它可以作为我们进行架构设计、技术选型的考量标准。对于大型互联网应用场景来说，结点众多、部署分散，而且现在的集群规模越来越大，所以结点故障、网络故障是常态，而且要保证服务可用性达到N个9（99.99..%）,并要达到良好的响应性能来提高用户的体验，因此一般都会做出以下选择：保证可用性和分区容忍性即AP，舍弃C，强一致性，保证最终一致性。</p>
+<h3 id="base理论">BASE理论</h3>
+<blockquote>
+<p>理解强一致性与最终一致性：
+CAP理论说明一个分布式系统最多能同时满足一致性、可用性、分区容忍性这三项中的两项；其中AP在实际应用中比较多，AP舍弃一致性，保证可用性和分区容忍性，但是在实际生产中很多场景都要实现一致性，比如前边的例子，主数据库向从数据库同步数据，即使不要一致性，但是最终也要将数据同步成功来保证数据一致，这种一致性和CAP中的一致性不同，CAP中的一致性要求在任何时间查询每个结点数据都必须保证一致，它强调的是一致性；
+但是最终一致性是允许可以在一段时间内每个结点数据不一致，但是经过一段时间后每个结点的数据必须一致，它强调的是数据的最终一致性。</p>
+</blockquote>
+<p>BASE是Basically Available(基本可用)、Soft state(软状态)、Eventually consistent(最终一致性) 这三个短语的缩写。
+BASE理论是对于CAP中AP的一个扩展，通过牺牲强一致性来获得可用性，当出现故障允许的部分不可用但要保证核心功能可用，允许数据在一段时间内是不一致的，但最终达到一致的状态。满足BASE理论的事务，我们称之为柔性事务。</p>
+<ul>
+<li>基本可用：分布式系统出现故障时，允许损失部分可用的功能，保证核心功能可用。例如，电商网站交易付款出现问题，商品依然可以正常浏览。</li>
+<li>软状态：由于不要求强一致性，所以BASE允许系统中存在<strong>中间状态（软状态）</strong>，这个状态不影响系统的可用性。例如，订单的&quot;支付中、数据同步中&quot;等状态，待数据最终一致后状态改为&quot;成功&quot;状态。</li>
+<li>最终一致性：最终一致是指经过一段时间后，所有的结点数据将会达到一致。例如，订单的&quot;支付中&quot;状态，最终会变为&quot;支付成功&quot;或&quot;支付失败&rdquo;，使订单状态与交易结果达成一致，但需要一定的时间等待。</li>
+</ul>
+<h2 id="分布式事务解决方案-2pc">分布式事务解决方案-2PC</h2>
+<p>针对不同的分布式场景常见的解决方案有2PC、TCC、可靠消息最终一致性、最大努力通知这几种。</p>
+<h3 id="什么是2pc">什么是2PC</h3>
+<p>2PC即两阶段提交协议，是将整个事务流程分为两个阶段：准备阶段（Prepare）、提交阶段（Commit），2是指两个阶段，P是准备阶段，C是提交阶段。</p>
+<p>举例，张三，李四聚餐，饭店老板要求先买单才能出票。张三李四都不愿请客，只能AA。只有张三和李四都付款，老板才能出票安排就餐。</p>
+<ul>
+<li>准备阶段：老板要求张三付款，张三付款；老板要求李四付款，李四付款。</li>
+<li>提交阶段：老板出票，两人拿票纷纷入座就餐。</li>
+</ul>
+<p>例子中形成了一个事务，若张三或李四其中一人拒绝付款，或者钱不够，老板都不会出票，并且把已收的钱退回。</p>
+<p>整个事务过程由<strong>事务管理器</strong>和参与者组成，老板就是事务管理器，张三、李四就是事务参与者，事务管理器负责抉择整个分布式事务的提交和回滚，事务参与者负责自己的本地事务提交和回滚。</p>
+<p>在计算机中部分关系型数据库如oracle、mysql支持两阶段提交协议：</p>
+<ol>
+<li>准备阶段：事务管理器给每个参与者发送Prepare消息,每个数据库参与者执行本地事务，并写本地的Undo/Redo日志，此时事务还没有提交。</li>
+</ol>
+<blockquote>
+<p>Undo日志是记录修改前的数据，用于数据库回滚；Redo日志是记录修改后的数据，用于提交事务后写入数据文件。</p>
+</blockquote>
+<ol start="2">
+<li>提交阶段：如果事务管理器收到了参与者的执行失败或超时的消息，那么直接给每个参与者发送回滚消息；否则，发送提交消息。参与者根据事务管理器的指令执行提交或回滚的操作，并释放事务处理过程中使用的锁资源。</li>
+</ol>
+<blockquote>
+<p>注意：必须在最后释放锁资源</p>
+</blockquote>
+<p>成功情况：
+<img alt="分布式事务-002" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-002.png"></p>
+<p>失败情况：
+<img alt="分布式事务-003" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-003.png"></p>
+<h3 id="解决方案">解决方案</h3>
+<p>2PC具体解决方案.</p>
+<h4 id="xa方案">XA方案</h4>
+<p>2PC的传统方案是在数据库层面实现的,如:oracle、mysql都支持2PC协议，为了统一标准减少行业内不必要的对接成本，需要制定标准化的处理模型即接口标准，国际开放标准组织OpenGroup定义了分布式处理模型DTP(<code>Distributed Transaction Processing Reference Model</code>)。</p>
+<p>DTP模型定义如下角色：</p>
+<ul>
+<li>AP：<code>Application Program</code>即应用程序，可以理解为使用分布式事务的程序。</li>
+<li>RM：<code>Resource Manager</code>即资源管理器，可理解为事务的参与者，一般情况是指一个数据库实例，通过资源管理器对该数据库进行控制，资源管理器控制这分支事务。</li>
+<li>TM：<code>Transacition Manager</code>即事务管理器，负责协调事务和事务管理，它控制着全局的事务，管理事务的生命周期，并协调各个资源管理器。</li>
+</ul>
+<blockquote>
+<p>全局事务是指分布式处理事务环境中，需要操作多个数据库共同完成一个动作，这个工作即是一个全局事务。</p>
+</blockquote>
+<p>以新用户注册送积分为例：
+<img alt="分布式事务-004" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-004.png"></p>
+<p>执行流程如下：</p>
+<ol>
+<li>
+<p>应用程序持有数据库和积分库两个数据源。</p>
+</li>
+<li>
+<p>应用程序通过事务管理器通知用户库的资源管理器新增用户，同时也通知积分库的资源管理器为该用户增加积分，资源管理器此时并未提交事务，此时用户和积分资源锁定。</p>
+</li>
+<li>
+<p>事务管理器收到执行回复，只要有一方失败则分别向其他方发起事务回滚，回滚完毕，资源释放锁；或事务管理器收到执行回复，全部成功，此时向所有资源管理器发起提交事务，提交完毕，资源释放。</p>
+</li>
+</ol>
+<p><strong>DTP模型定义TM和RM之间通讯的接口规范叫XA，简单理解为数据库提供的2PC接口协议，基于数据库的XA协议来实现2PC又称为XA方案。</strong></p>
+<p>以上三个角色之间的交互方式如下：</p>
+<ul>
+<li>TM向AP提供程序编程接口，AP通过TM提交或回滚事务</li>
+<li>TM交易中间件通过XA接口来通知RM数据库事务的开始、结束以及提交、回滚等</li>
+</ul>
+<p>整个2PC的事务管理流程涉及到三个角色：AP、RM、TM。AP指的是使用2PC分布式事务的应用程序；RM指的是资源管理器，它控制这分支事务；TM指的是事务管理器，它控制着全局事务。</p>
+<p>在准备阶段RM执行实际的业务操作，但是不提交事务，资源锁定；在提交阶段TM会接受RM在准备阶段的执行回复，只要任何一个RM执行失败，TM会通知所有的RM进行回滚操作，否则TM将会通知RM提交事务。提交阶段结束释放资源。</p>
+<p>XA方案存在的问题：</p>
+<ul>
+<li>需要本地数据库支持XA协议</li>
+<li>资源锁需要等到准备阶段和提交阶段结束才释放，性能较差</li>
+</ul>
+<h4 id="seata方案">Seata方案</h4>
+<p>Seata是由阿里中间件团队发起的开源项目Fescar，后更名为Seata，它是一个开源的分布式事务框架。</p>
+<p>传统2PC的问题在Seata中的到了解决，它通过对本地关系型数据库的分支事务的协调来驱动完成全局事务，是工作在应用层的中间件。主要优点是性能较好，且不长时间占用连接资源，它以高效并对业务0入侵的方式解决微服务场景下面临的分布式事务问题，目前提供AT模式（即2PC）和TCC模式的分布式事务解决方案。</p>
+<p><strong>Seata的设计思想:</strong></p>
+<p>Seata的设计目标其一是对业务零侵入，因此从业务无侵入的2PC入手，在传统方案2PC的基础上演进，并解决2PC方案面临的问题。</p>
+<p>Seata把一个分布式的事务理解为一个包含了若干分支事务的全局事务。全局事务的职责是协调其下管辖的分支事务达成一致，要么一起成功提交事务，要么一起回滚失败。此外，通常分支事务本身就是一个关系型数据库的本地事务。</p>
+<p><img alt="分布式事务-005" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-005.png"></p>
+<p>与传统2PC的模型类似，Seata定义了3个组件来协调分布式事务的处理过程：</p>
+<p><img alt="分布式事务-006" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-006.png"></p>
+<ul>
+<li>TM：<code>Transaction Manager</code>事务管理器，需要嵌入（jar包）应用程序中工作，负责开启一个全局事务，并最终向TC发起全局提交或全局回滚的指令。</li>
+<li>RM：<code>Resource Manager</code>资源管理器，控制分支事务，负责分支事务注册，状态回报，并接收事务调节器的指令，驱动分支事务的提交和回滚。</li>
+<li>TC：<code>Transaction Coordinator</code>事务协调器，它是独立的中间件，需要独立运行部署，它维护全局事务的运行状态，接收TM指令发起全局事务的提交与回滚，负责与RM通信协调各个分支事务的提交回滚。</li>
+</ul>
+<p>以新用户注册送积分举例：
+<img alt="分布式事务-007" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-007.png"></p>
+<p>具体执行流程：</p>
+<ol>
+<li>用户服务器的事务管理器向事务协调器申请开启一个全局事务，全局事务的创建成功并生成一个全局唯一XID。</li>
+<li>用户服务器的资源管理器向事务协调器注册分支事务，该分支事务在用户服务执行新增用户逻辑，并将其纳入XID对应全局事务的管辖。</li>
+</ol>
+<blockquote>
+<p>注意：在执行注册分支事务的时候，这里事务已经提交了，提交后可以释放资源，从而提升程序性能。</p>
+</blockquote>
+<ol start="3">
+<li>用户服务器执行分支事务，向用户表插入一条记录。</li>
+<li>逻辑执行到远程分布式调用积分服务时，XID在微服务调用链路的上下文中传播。积分服务的资源管理器向事务协调器注册了分支事务，该分支事务执行增加积分的逻辑，并将其纳入XID对应的全局事务的管辖。</li>
+<li>积分服务执行分支事务，向积分记录表插入一条记录，执行完毕后，返回用户服务。</li>
+<li>用户服务分支事务执行完毕。</li>
+<li>事务管理器向事务协调器针对XID的全局提交或者回滚决策。</li>
+<li>事务协调器调度XID下管辖的全部分支事务完成提交或回滚的请求。</li>
+</ol>
+<p>Seata实现2PC与传统2PC的差别：</p>
+<ul>
+<li>
+<p>架构方面，传统2PC方案的RM实际上是在数据库层，RM本质上就是数据库自身，通过XA协议实现，而Seata的RM则是以jar包的形式作为中间件层部署在应用程序这一侧的。</p>
+</li>
+<li>
+<p>两阶段提交方面，传统2PC无论第二阶段的决策是commit还是rollback，事务性资源的锁都要保持到第二阶段才释放。而Seata的做法是在第一阶段就将本地事务提交，这样可以省去第二阶段持有锁的时间，提高整体效率。</p>
+</li>
+</ul>
+<p><strong>Seata原理简介:</strong></p>
+<blockquote>
+<p>两阶段提交协议的演变：</p>
+<ul>
+<li>一阶段：业务数据和回滚日志记录在同一个本地事务中提交，释放本地锁和连接资源。</li>
+<li>二阶段：
+<ul>
+<li>提交异步化，非常快速地完成。</li>
+<li>回滚通过一阶段的回滚日志进行反向补偿。</li>
+</ul>
+</li>
+</ul>
+</blockquote>
+<p>一阶段：seata会拦截,解析SQL语义,找到SQL要更新的数据,在业务员数据更新前,将其保存为before image,随后执行业务SQL,在业务数据更新后,将其保存为after image,插入UNDO LOG回滚日志；提交前，向 TC 注册分支生成行锁。
+随后本地事务提交，将本地事务提交的结果上报给 TC，由TC协调。</p>
+<p><img alt="分布式事务-008" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-008.png"></p>
+<p>二阶段-提交：执行提交操作，说明SQL执行顺利，因业务SQL在一阶段已经提交至数据库，所以Seata框架只需将一阶段保存的快照数据和行锁删掉，完成数据清理即可。</p>
+<p><img alt="分布式事务-009" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-009.png"></p>
+<p>二阶段-回滚：要执行回滚操作，说明SQL执行不顺利，Seata需要回滚一阶段已经执行的业务SQL还原数据。回滚方式是用before image还原数据，但是在还原前还要校验脏写，对比数据库当前业务数据和after image。
+对比数据库当前业务数据和after image。</p>
+<p><img alt="分布式事务-010" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-010.png"></p>
+<h2 id="分布式事务解决方案-tcc">分布式事务解决方案-TCC</h2>
+<p>针对不同的分布式场景常见的解决方案有2PC、TCC、可靠消息最终一致性、最大努力通知这几种。</p>
+<h3 id="什么是tcc">什么是TCC</h3>
+<p>TCC是Try、Confirm、Cancel三个词语的缩写，TCC要求每个分支事务实现三个操作：预处理Try、确认Confirm、撤销Cancel。
+Try操作做业务检查及资源预留，Confirm做业务确认操作，Cancel实现一个与Try相反的操作，即回滚操作。TM首先发起所有分支事务的try操作，任何一个分支事务的try操作执行失败，TM将会发起所有分支事务的Cancel操作，若try操作全部成功，TM将发起所有分支事务的Confirm操作，其中Confirm或Cancel操作失败，TM会重试。</p>
+<p><img alt="分布式事务-011" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-011.png"></p>
+<p>分布式事务执行失败情况：</p>
+<p><img alt="分布式事务-012" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-012.png"></p>
+<p>TCC的三个阶段：</p>
+<ul>
+<li>Try阶段是做业务检查一致性及资源预留，此阶段仅是一个初步操作，它和后续的Confirm一起才能真正的构成一个完整的业务逻辑；</li>
+<li>Confirm阶段是确认提交，Try阶段所有的分支事务执行成功后开始执行Confirm。通常情况下，采用TCC则认为Confirm阶段是不会出错的。即：只要Try成功，Confirm一定成功。若Confirm阶段真的出错了，需要引入重试机制或进行人工处理；</li>
+<li>Cancel阶段是在业务执行错误需要回滚的状态下，执行分支事务的业务取消了，预留资源释放。通常情况下，采用TCC则认为Cancel阶段也是一定成功的。如果Cancel阶段真的出错了，需要引入重试机制或进行人工处理；</li>
+</ul>
+<p>TM事务管理器：</p>
+<ul>
+<li>TM事务管理器可以实现为独立的服务，也可以让全局事务发起方充当TM的角色，TM独立出来是为了成为公用的组件，为了考虑系统结构和软件复用。</li>
+</ul>
+<p>TM发起全局事务时生成全局事务记录，全局事务ID贯穿整个分布式事务调用链，用来记录事务上下文，追踪和记录状态，由于Confirm和Cancel失败需要进行重试或人工处理，因此实现为幂等，幂等性是指同一个操作无论请求多少次，其结果都相同。</p>
+<h3 id="解决方案-1">解决方案</h3>
+<p>Hmily是一个高性能分布式事务TCC开源框架。基于Java语言来开发（JDK1.8），支持Dubbo，Spring Cloud等RPC框架进行分布式事务。
+目前支持以下特性：</p>
+<ul>
+<li>支持嵌套事务(Nested transaction support);</li>
+<li>采用disruptor框架进行事务日志的异步读写，与RPC框架的性能毫无差别;</li>
+<li>支持SpringBoot-starter 项目启动，使用简单;</li>
+<li>RPC框架支持 : dubbo,motan,springcloud;</li>
+<li>本地事务存储支持 : redis,mongodb,zookeeper,file,mysql;</li>
+<li>事务日志序列化支持：java，hessian，kryo，protostuff;</li>
+<li>采用Aspect AOP 切面思想与Spring无缝集成，天然支持集群;</li>
+<li>RPC事务恢复，超时异常恢复等;</li>
+</ul>
+<p>Hmily利用AOP对参与分布式事务的本地方法与远程方法进行拦截处理，通过多方拦截，事务参与者能透明的调用到另一方的Try、Confirm、Cancel方法；
+传递事务上下文；并记录事务日志，酌情进行补偿，重试等。</p>
+<p>Hmily是一个轻量级的TCC事务框架不需要部署独立的事务协调服务，但需要提供一个数据库来进行日志存储。</p>
+<p>Hmily实现的TCC服务与普通的服务一样，只需要暴露一个接口，也就是它的Try业务。Confirm/Cancel业务逻辑，只是因为全局事务提交/回滚的需要才提供的，因此Confirm/Cancel业务只需要被Hmily TCC事务框架发现即可，不需要被调用它的其他业务服务所感知。</p>
+<blockquote>
+<p>要实现TCC协议，必须要实现三个方法：Try、Confirm、Cancel，其中最关键的方法是Try方法，Try方法是一个事务的起点。三个方法会由不同的线程来分别调用。</p>
+</blockquote>
+<p><strong>TCC需要注意三种异常处理：空回滚、幂等、悬挂：</strong></p>
+<ol>
+<li>
+<p><strong>空回滚</strong>:在没有调用TCC资源Try方法的情况下,调用了二阶段的Cancel方法，Cancel方法需要识别出这是一个空回滚，然后直接返回成功。
+<br>
+出现原因是当一个分支事务所在的服务器宕机或网络异常，分支事务调用记录为失败,这个时候其实是没有执行Try阶段，当故障恢复后，分布式事务进行回滚则会调用二阶段的Cancel方法，从而形成空回滚。
+<br>
+解决思路关键就是要标识这个空回滚,就是要知道try阶段是否已经执行了，如果执行了那就是正常回滚；如果没执行,那就是空回滚。可以在try阶段执行完毕后向表里插入一条记录进行标识，如果记录存在则try阶段执行了，如果不存在try阶段则未执行。</p>
+</li>
+<li>
+<p><strong>幂等</strong>:为了保证TCC二阶段提交重试机制不会引发数据不一致，要求TCC二阶段Try、Confirm、Cancel接口保证幂等性，这样不会重复使用或示释放资源。如果幂等控制没有做好，很有可能导致数据不一致等严重问题。</p>
+</li>
+<li>
+<p><strong>悬挂</strong>:悬挂就是对于一个分布式事务,其二阶段Cancel接口对比Try接口先执行。</p>
+</li>
+</ol>
+<p>出现原因是在RPC调用分支事务时,先注册分支事务，在执行RPC调用,如果此时RPC调用的网络发生错误，RPC超时后，TM就会通知RM回滚该分布式事务，可能回滚完成后,RPC请求才到达，然后执行，而一个try方法预留的业务资源，只有该分布式事务才能使用，该分布式事务第一阶段预留的业务资源也就在也没有人能够处理，对于这种情况就称为悬挂，即业务资源预留后没办法处理。</p>
+<h2 id="分布式事务解决方案-可靠消息最终一致性">分布式事务解决方案-可靠消息最终一致性</h2>
+<p>针对不同的分布式场景常见的解决方案有2PC、TCC、可靠消息最终一致性、最大努力通知这几种。</p>
+<h3 id="什么是可靠消息最终一致性">什么是可靠消息最终一致性</h3>
+<p>可靠消息最终一致性是指当事务发起方执行完本地事务后并发出一条消息，事务参与方（消息消费者）一定能接收到消息并成功处理事务，此方案强调的是只要消息发给事务参与方最终事务要达到一致。</p>
+<p>此方案利用消息中间件完成，事务发起方将消息发送给消息中间件，事务参与方从消息中间件接收消息，事务发起方和消息中间件之间，事务参与方和消息中间件之间都是通过网络进行通信，由于网络通信的不稳定会导致分布式事务问题。</p>
+<p><img alt="分布式事务-013" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-013.png"></p>
+<p>因此可靠消息最终一致性方案要解决几个问题：</p>
+<ul>
+<li><strong>本地事务与消息发送的原子性</strong> 即：事务发起方在本地事务执行成功后消息必须发出去，否则就丢弃消息。即实现本地事务和消息发送的原子性，要么都成功，要么都失败。本地事务与消息发送的原子性问题是实现可靠消息最终一致性方案的关键。</li>
+<li><strong>事务参与方接收消息的可靠性</strong> 事务参与方必须能够从消息队列接收消息，如果接收消息失败可以重复接收消息。</li>
+<li><strong>消息重复消费问题</strong> 由于网络存在问题，若某一个消费结点超时但是消费成功，此时消息中间件会重复投递此消息，就导致了消息重复消费问题。要解决消息重复消费问题就要实现事务参与方的方法的幂等性。</li>
+</ul>
+<h3 id="解决方案-2">解决方案</h3>
+<h4 id="本地消息表方案">本地消息表方案</h4>
+<p>本地消息表该方案最初是eBay提出，此方案的核心是通过本地事务保证数据业务操作和消息的一致性，然后通过定时任务将消息发送至消息中间件，待确认消息发送给消费方成功后在将消息删除。</p>
+<p>以用户注册送积分举例：用户服务负责添加用户，积分服务负责添加积分</p>
+<p><img alt="分布式事务-014" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-014.png"></p>
+<p>执行流程：</p>
+<ul>
+<li>用户注册，用户服务在本地新增用户和增加积分消息日志。用户表和消息表本地事务保持一致，这种情况下本地数据库操作与存储积分消息日志处于同一个事务中，本地数据库操作记录与记录消息日志操作具备原子性。</li>
+</ul>
+<p><strong>如何保证将消息发送给消息队列？</strong></p>
+<ul>
+<li>当消息已经写入到消息日志中去后，可以启动独立的线程，定时对消息日志表中的消息进行扫描并发送至消息中间件，在消息中间件反馈发送成功后删除该消息日志，否则等待定时任务下一周期重试。</li>
+</ul>
+<p><strong>如何保证消费者一定能消费到消息？</strong></p>
+<ul>
+<li>可以使用MQ的ACK机制即消息确认机制，消费这监听MQ，如果消费者接收到消息并且业务处理完成后想MQ发送ACK，此时说明消费者正常消费消息完成，MQ将不再向消费者推送消息，否则生产者会不断重试向消费者发送消息。</li>
+</ul>
+<p>由于消息会重复投递，积分服务的增加积分操作功能要实现幂等性。</p>
+<h4 id="rocketmq事务消息方案">RocketMQ事务消息方案</h4>
+<p>RocketMQ是阿里巴巴的分布式消息中间件，于2012年开源并在2017年正式称为apache的项目。ApacheRocketMQ4.3之后的版本正式支持事务消息，并为分布式事务提供了便利性支持。</p>
+<p>RocketMQ事务消息设计则主要是为了解决生产者端的消息发送与本地事务执行的原子性问题，RockerMQ设计中broker与生产者端的双向通信能力，使得broker天生可以作为一个事务协调者存在；RockerMQ的高可用机制以及可靠消息设计原则则为事务消息在系统发生异常时依然能够保证达成事务的最终一致性。</p>
+<p><img alt="分布式事务-015" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-015.png"></p>
+<p>执行流程：</p>
+<ol>
+<li>MQ的发起方会向MQ发送一条消息，MQ发起方会监听MQ是否响应；</li>
+<li>MQ收到该消息会响应消息发起方，代表发送给MQ成功；但是此时MQ并未发送消息给消费者；</li>
+<li>MQ发起方开始执行本地事务，执行完本地事务后，给MQ发送commit消息，此时MQ将该消息更改为可消费状态，消费者可以消费该消息；如果消费者执行本地事务失败，给MQ发送rollback消息，MQ会将该消息丢弃；</li>
+<li>消费者方利用MQ的ACK机制来保证消息一定被消费到；</li>
+</ol>
+<p><strong>注意：发起方与MQ之间的网络出现问题，但此时MQ里的消息不会一直存着；MQ服务会定回查消费者方本地事务状态（实现MQ事务回查接口），如果事务已经提交了消费者仍然可以接收到该消息，如果没有提交MQ则丢弃该消息。</strong></p>
+<h2 id="分布式事务解决方案-最大努力通知">分布式事务解决方案-最大努力通知</h2>
+<p>针对不同的分布式场景常见的解决方案有2PC、TCC、可靠消息最终一致性、最大努力通知这几种。</p>
+<h3 id="什么是最大努力通知">什么是最大努力通知</h3>
+<p>顾名思义，发起通知方通过一定机制最大努力的将业务处理结果通知到接收方。</p>
+<p>举个例子：</p>
+<p><img alt="分布式事务-016" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-016.png"></p>
+<p>账户系统调用充值系统接口，充值系统完成处理后向账户账户接口发起充值结果通知，如果通知失败则充值充值系统则按策略进行重复通知；账户系统接收到充值系统的通知后修改充值状态。如果账户系统未接受到通知，账户系统会主动调用充值系统接口进行结果查询。</p>
+<p>最大努力通知特点：</p>
+<ul>
+<li>有一定的消息重复通知机制。因接收方可能没有收到通知，此时要有一定的机制对消息重复通知。</li>
+<li>消息校对机制。如果发起方尽最大努力也没有通知到接收方，或接收方消费消息后要再次消费，此时可由接收方主动向通知方查询处理结果来满足需求。</li>
+</ul>
+<p><strong>最大努力通知与可靠消息一致性不同点</strong></p>
+<ul>
+<li>解决方案思想不同：
+<ul>
+<li>可靠消息一致性，发起通知方需要保证将消息发送出去，并且将消息发送到接收方，消息的可靠性关键由发起方来保证。</li>
+<li>最大努力通知，发起通知尽最大努力的将业务处理结果通知接收方，但是消息可能接收不到，此时需要接收通知方主动调用发起方的查询业务处理结果接口，通知的可靠性关键在接收方。</li>
+</ul>
+</li>
+<li>业务场景不同：
+<ul>
+<li>可靠消息一致性关注的是交易过程事务的一致性，以异步的方式完成交易。</li>
+<li>最大努力通知关注的是交易后的通知事务，即将交易结果可靠的通知出去。</li>
+</ul>
+</li>
+<li>技术解决方向不同：
+<ul>
+<li>可靠消息一致性要解决消息从发出到接收的一致性，即发出消息并且被接收到。</li>
+<li>最大努力通知无法保证发出到接收的一致性，只提供消息接收的可靠性机制。消息接收可靠机制指，最大努力的将通知发送给接收方，当消息无法被接收方接收时，由接收方主动查询该消息。</li>
+</ul>
+</li>
+</ul>
+<h3 id="解决方案-3">解决方案</h3>
+<p>通过对最大努力通知的理解，采用MQ的ack机制可以实现最大努力通知。</p>
+<h4 id="方案1">方案1</h4>
+<p><img alt="分布式事务-017" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-017.png"></p>
+<p>执行流程：</p>
+<ul>
+<li>发起通知方将通知发送给MQ；</li>
+<li>接收方监听MQ；</li>
+<li>接收通知方接收消息，业务处理完成回应ack，接收方若没有回应ack则MQ重复通知；</li>
+<li>如果消息没有发送出去可由接收方主动请求发起方查询业务结果接口，通过该接口校对消息的一致性；</li>
+</ul>
+<p>方案1中接收通知方MQ接口，即接收通知方监听MQ，此方案主要应用于应用与内部应用之间的通知。</p>
+<h4 id="方案2">方案2</h4>
+<p><img alt="分布式事务-018" src="/iblog/posts/annex/images/essays/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1-018.png"></p>
+<p>交互流程：</p>
+<ul>
+<li>发起通知方将消息通知给MQ。使用可靠消息一致方案中的事务消息保证本地事务与消息的原子性，最终将通知先发给MQ；</li>
+<li>通知程序监听MQ，接收MQ消息。通知程序如果没有回应ack则MQ会重复通知；</li>
+<li>通知程序通过互联网接口协议调用接收通知方接口，完成通知。通知程序调用接收方接口成功就表示通知成功，即MQ消费成功，MQ将不再向通知程序投递消息；</li>
+<li>接收通知方可通过消息校对接口来校对消息的一致性；</li>
+</ul>
+<p>方案2中由于通知程序与MQ接口，通知程序监听MQ，收到MQ消息后由通知程序通过互联网接口协议调用接收通知方。此方案主要应用于外部应用之间的通知。</p>
+<h2 id="分布式解决方案对比">分布式解决方案对比</h2>
+<p><strong>2PC</strong>最大的诟病是一个阻塞协议。RM在执行分支事务后需要等待MT决定，此时服务会堵塞并锁定资源，由于其堵塞机制和最差时间复杂度较高，因此这种设计不能适应随着事务涉及的服务数量增多而扩展的需要，很难用于并发较高以及事务生命周期较长的分布式服务中。</p>
+<p>如果拿<strong>TCC</strong>的事务处理流程与2PC做比较，2PC通常都是在跨库的DB层面，而TCC则在应用层面的处理，需要通过业务逻辑来实现。这种分布式事务的实现方式优势在于，可以让应用自己定义数据库操作的粒度，使得降低锁冲突、提高吞吐量。不足之处是对应用的侵入性非常强，业务逻辑的每个分支都要实现try、confirm、cancel三个操作；此外实现难度也比较大，需要按照网络状态、系统故障的等不同失败原因进行不同回滚策略。</p>
+<p><strong>可靠消息最终一致性</strong>适合执行周期长且实时性要求不高的业务场景。引入消息机制后，同步的事务操作变为基于消息执行的异步操作，避免了分布式事务中同步堵塞操作的影响，并实现了两个服务之间的解耦。</p>
+<p><strong>最大努力通知</strong>是分布式事务中要求最低的一种，适用于一些最终一致性时间敏感度低的业务；允许发起通知方处理失败，在接收通知方收到失败通知后积极进行失败处理，无论发起通知方如何处理结果都不会影响到接收方的后续处理；发起通知方需要提供查询执行情况的接口，用于接收通知方校对结果。</p>
+<table>
+<thead>
+<tr>
+<th></th>
+<th>2PC</th>
+<th>TCC</th>
+<th>可靠消息最终一致性</th>
+<th>最大努力通知</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>一致性</td>
+<td>强一致性</td>
+<td>最终一致性</td>
+<td>最终一致性</td>
+<td>最终一致性</td>
+</tr>
+<tr>
+<td>吞吐量</td>
+<td>低</td>
+<td>中</td>
+<td>高</td>
+<td>高</td>
+</tr>
+<tr>
+<td>实现复杂度</td>
+<td>易</td>
+<td>难</td>
+<td>中</td>
+<td>易</td>
+</tr>
+</tbody>
+</table>
+</div>
+                    <div id="post_footer" class="post_footer">
+                        <div class="meta">
+                            
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\ No newline at end of file
diff --git a/docs/posts/detailed/sql-select-fast/index.html b/docs/posts/detailed/sql-select-fast/index.html
new file mode 100644
index 00000000..c3afc243
--- /dev/null
+++ b/docs/posts/detailed/sql-select-fast/index.html
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+
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+
+<div id="post_content_toc" class="toc">
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e4%bb%8b%e7%bb%8d">
+                    MySQL介绍
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+            
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+        <ul class="nav">
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e9%80%bb%e8%be%91%e6%9e%b6%e6%9e%84">
+                    MySQL逻辑架构
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+            </li>
+            
+            
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+        
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+        
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+        
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+            
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e5%ad%98%e5%82%a8%e5%bc%95%e6%93%8e">
+                    MySQL存储引擎
+                </a>
+            </li>
+            
+            
+        </ul>
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+        
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+        <ul class="nav">
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e4%ba%8b%e5%8a%a1">
+                    MySQL事务
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
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+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%8b%e7%89%a9%e7%9a%84%e5%ae%9e%e7%8e%b0">
+                    事物的实现
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+            </li>
+            
+            
+        </ul>
+        
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+            
+            <li class="nav-item">
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
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+        </ul>
+        
+        
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+        
+        
+        
+        
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+        <ul class="nav">
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+            
+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#consistency%e4%b8%80%e8%87%b4%e6%80%a7">
+                    Consistency一致性
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+        
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+                <a class="nav-link text-left" href="#isolation%e9%9a%94%e7%a6%bb%e6%80%a7">
+                    Isolation隔离性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+                    Durability持久性
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+                    MySQL中的日志
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
+        
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+            <li class="nav-item">
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+                    MVCC并发控制机制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%93%8d%e4%bd%9c%e4%ba%8b%e7%89%a9">
+                    操作事物
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e7%b4%a2%e5%bc%95">
+                    MySQL索引
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e6%95%b0%e6%8d%ae%e7%bb%93%e6%9e%84">
+                    索引数据结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e7%9a%84%e5%ae%9e%e7%8e%b0">
+                    索引的实现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#myisam%e7%b4%a2%e5%bc%95%e7%9a%84%e5%ae%9e%e7%8e%b0">
+                    MyISAM索引的实现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#innodb%e7%b4%a2%e5%bc%95%e7%9a%84%e5%ae%9e%e7%8e%b0">
+                    InnoDB索引的实现
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e7%9a%84%e4%bc%98%e7%bc%ba%e7%82%b9">
+                    索引的优缺点
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e5%88%86%e7%b1%bb">
+                    索引分类
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%93%8d%e4%bd%9c%e7%b4%a2%e5%bc%95">
+                    操作索引
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%80%e5%b7%a6%e5%89%8d%e7%bc%80%e5%8c%b9%e9%85%8d%e5%8e%9f%e5%88%99">
+                    最左前缀匹配原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e8%a6%86%e7%9b%96">
+                    索引覆盖
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b4%a2%e5%bc%95%e5%bb%ba%e7%ab%8b%e5%8e%9f%e5%88%99">
+                    索引建立原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%81%bf%e5%85%8d%e7%b4%a2%e5%bc%95%e5%a4%b1%e6%95%88%e5%8e%9f%e5%88%99">
+                    避免索引失效原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e6%89%a7%e8%a1%8c%e8%ae%a1%e5%88%92">
+                    MySQL执行计划
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#idtable">
+                    id、table
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#select_type">
+                    select_type
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#type">
+                    type
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#possible_keyskey">
+                    possible_keys、key
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#key_len">
+                    key_len
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#ref">
+                    ref
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#rows">
+                    rows
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#extra">
+                    Extra
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e4%bc%98%e5%8c%96">
+                    MySQL优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#sql%e6%89%a7%e8%a1%8c%e8%bf%87%e7%a8%8b">
+                    SQL执行过程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bc%98%e5%8c%96%e6%80%9d%e8%b7%af">
+                    优化思路
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%92%e6%9f%a5%e6%85%a2sql">
+                    排查慢SQL
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%85%a2sql%e6%97%a5%e5%bf%97%e8%ae%be%e7%bd%ae">
+                    慢SQL日志设置
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9f%a5%e7%9c%8b%e6%85%a2sql%e6%97%a5%e5%bf%97">
+                    查看慢SQL日志
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a8%a1%e6%8b%9f%e6%95%b0%e6%8d%ae%e5%b9%b6%e5%88%86%e6%9e%90sql">
+                    模拟数据并分析SQL
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%a8%e5%b1%80%e6%9f%a5%e8%af%a2%e6%97%a5%e5%bf%97">
+                    全局查询日志
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#sql%e4%bc%98%e5%8c%96%e6%96%b9%e6%b3%95">
+                    SQL优化方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#exist%e5%92%8cin%e9%80%89%e6%8b%a9">
+                    exist和in选择
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#order-by%e4%bc%98%e5%8c%96">
+                    order by优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#sql%e4%bc%98%e5%8c%96%e6%a1%88%e4%be%8b">
+                    SQL优化案例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8d%95%e8%a1%a8%e4%bc%98%e5%8c%96">
+                    单表优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%a4%e8%a1%a8%e4%bc%98%e5%8c%96">
+                    两表优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#mysql%e9%94%81%e6%9c%ba%e5%88%b6">
+                    MySQL锁机制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a1%a8%e9%94%81">
+                    表锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a1%8c%e9%94%81">
+                    行锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
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+                        <h2 id="post_single_title">MySQL详解</h2>
+                        <span id="post_page_title_date" class="date">2024.05.30</span>
+                        
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+                    <div class="post_content markdown"><h2 id="mysql介绍">MySQL介绍</h2>
+<p>MySQL 是一种关系型数据库，主要用于持久化存储我们系统中的一些数据。</p>
+<p>MySQL 如此流行的原因，主要具有下面这些优点：</p>
+<ul>
+<li>成熟稳定，功能完善。</li>
+<li>开源免费。</li>
+<li>文档丰富，既有详细的官方文档，又有非常多优质文章可供参考学习。</li>
+<li>开箱即用，操作简单，维护成本低。</li>
+<li>兼容性好，支持常见的操作系统，支持多种开发语言。</li>
+<li>社区活跃，生态完善。</li>
+<li>事务支持优秀， InnoDB 存储引擎默认使用 REPEATABLE-READ 并不会有任何性能损失，并且，InnoDB 实现的 REPEATABLE-READ 隔离级别其实是可以解决幻读问题发生的。</li>
+<li>支持分库分表、读写分离、高可用。</li>
+</ul>
+<h2 id="mysql逻辑架构">MySQL逻辑架构</h2>
+<p>主要分为：连接层，服务层，引擎层，存储层。</p>
+<p>客户端执行一条select命令的流程如下：</p>
+<p><img alt="MySqlSQL优化及锁机制-001" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-001.png"></p>
+<ul>
+<li>连接层：最上层是一些客户端和连接服务，包含本地sock通信和大多数基于客户端/服务端工具实现的类似于tcplip的通信。主要完成一些类似于连接处理、授权认证、及相关的安全方案。在该层上引入了线程池的概念，为通过认证安全接入的客户端提供线程。同样在该层上可以实现基于SSL的安全链接。服务器也会为安全接入的每个客户端验证它所具有的操作权限。</li>
+<li>服务层：第二层架构主要完成大多少的核心服务功能，如SQL接口，并完成缓存的查询，SQL的分析和优化及部分内置函数的执行。所有跨存储引擎的功能也在这一层实现，如过程、函数等。在该层，服务器会解析查询并创建相应的内部解析树，并对其完成相应的优化如确定查询表的顺序是否利用索引等，最后生成相应的执行操作。如果是select语句，服务器还会查询内部的缓存。如果缓存空间足够大，这样在解决大量读操作的环境中能够很好的提升系统的性能。</li>
+<li>引擎层：存储引擎层，存储引擎真正的负责了MySQL中数据的存储和提取，服务器通过API与存储引擎进行通信。不同的存储引擎具有的功能不同这样我们可以根据自己的实际需要进行选取，后面介绍MyISAM和InnoDB。</li>
+<li>存储层：数据存储层，主要是将数据存储在运行于裸设备的文件系统之上，并完成与存储引擎的交互。</li>
+</ul>
+<p>详细一点：</p>
+<p><img alt="MySQL基础架构" src="/iblog/posts/annex/images/essays/MySQL%E5%9F%BA%E7%A1%80%E6%9E%B6%E6%9E%84.png"></p>
+<ul>
+<li>连接器： 登录 MySQL 的时候需要身份权限认证。</li>
+<li>查询缓存： 执行查询语句的时候，会先查询缓存，不过在MySQL 8.0 版本后移除。</li>
+<li>分析器： 没有命中缓存的话，SQL 语句就会经过分析器，分析器说白了就是要先看你的 SQL 语句要干嘛，再检查你的 SQL 语句语法是否正确。</li>
+<li>优化器： 按照 MySQL 认为最优的方案去执行。</li>
+<li>执行器： 执行语句，然后从存储引擎返回数据。执行语句之前会先判断是否有权限，如果没有权限的话，就会报错。</li>
+<li>插件式存储引擎：主要负责数据的存储和读取，采用的是插件式架构，支持 InnoDB、MyISAM、Memory 等多种存储引擎。</li>
+</ul>
+<h2 id="mysql存储引擎">MySQL存储引擎</h2>
+<p>MySQL 核心在于存储引擎，MySQL 5.5.5 之前，MyISAM 是 MySQL 的默认存储引擎。5.5.5 版本之后，InnoDB 是 MySQL 的默认存储引擎。</p>
+<p>可以使用<code>show engines;</code>来查看。</p>
+<p><img alt="MySQL存储引擎" src="/iblog/posts/annex/images/essays/MySQL%E5%AD%98%E5%82%A8%E5%BC%95%E6%93%8E.png"></p>
+<table>
+<thead>
+<tr>
+<th>特性</th>
+<th>InnoDB</th>
+<th>MyISAM</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>事务支持</td>
+<td>支持</td>
+<td>不支持</td>
+</tr>
+<tr>
+<td>锁类型</td>
+<td>行级锁</td>
+<td>表级锁</td>
+</tr>
+<tr>
+<td>外键支持</td>
+<td>支持</td>
+<td>不支持</td>
+</tr>
+<tr>
+<td>崩溃恢复</td>
+<td>支持</td>
+<td>不支持</td>
+</tr>
+<tr>
+<td>数据存储</td>
+<td>表和索引存储在表空间中</td>
+<td>数据和索引存储在不同文件中</td>
+</tr>
+<tr>
+<td>全文索引</td>
+<td>MySQL 5.6及以上版本支持</td>
+<td>支持</td>
+</tr>
+<tr>
+<td>适用场景</td>
+<td>高并发和事务性要求高的应用</td>
+<td>读操作多、写操作少的应用</td>
+</tr>
+<tr>
+<td>性能</td>
+<td>写性能较好，读性能较好</td>
+<td>读性能高，写性能相对较差</td>
+</tr>
+<tr>
+<td>数据完整性</td>
+<td>高</td>
+<td>低</td>
+</tr>
+</tbody>
+</table>
+<p>选择 InnoDB 还是 MyISAM 取决于具体的应用需求。InnoDB 适合需要高并发、高数据完整性和事务支持的应用，而 MyISAM 适合读操作多、数据一致性要求不高的应用。</p>
+<p>尽管 MyISAM 在特定场景下仍然有其应用价值，但随着 MySQL 版本的更新和 InnoDB 性能的不断提升，大多数新应用和系统都选择了 InnoDB 作为主要存储引擎。
+遗留系统可能继续使用 MyISAM，但在新开发中，使用 InnoDB 已成为主流和最佳实践。</p>
+<h2 id="mysql事务">MySQL事务</h2>
+<p>什么是事务？举个例子：你去超市买东西，&ldquo;一手交钱，一手交货&quot;就是一个事务的例子。
+交钱和交货必须同时成功，事务才算成功，其中有一个环节失败，事务将会撤销所有已成功的活动。</p>
+<p>所以事务可以看作是一次重大的活动，它由不同的小活动组成，这些活动要么全部成功，要么全部失败。</p>
+<p>所有的存储引擎中只有 <code>InnoDB</code>、<code>NDB</code> 是事务性存储引擎，也就是说只有 <code>InnoDB</code>、<code>NDB</code> 支持事务。</p>
+<h3 id="事物的实现">事物的实现</h3>
+<p>只要对数据库稍有了解的人都知道事务具有 ACID 四个基本属性，而我们不知道的可能就是数据库是如何实现这四个属性的。
+简单来说，事务是通过事务日志来实现的，事务日志包括：redo log和undo log，下面详细介绍。</p>
+<h4 id="atomicity原子性">Atomicity原子性</h4>
+<p>要么全部都执行，要都不执行，不可能出现部分成功部分失败的情况，这是对原子性最简单的描述。</p>
+<p>事务其实和一个操作没有什么太大的区别，它是一系列的数据库操作（可以理解为 SQL）的集合，如果事务不具备原子性，那么就没办法保证同一个事务中的所有操作都被执行或者未被执行了，整个数据库系统就既不可用也不可信。</p>
+<p>想要保证事务的原子性，就需要在异常发生时，对已经执行的操作进行回滚，而在 MySQL 中，恢复机制是通过回滚日志（undo log）实现的。
+为了能够在发生错误时撤销之前的全部操作，需要将之前的操作都记录下来的，所以所有事务进行的修改都会先记录到这个回滚日志中，然后再对数据库中的对应行进行操作。</p>
+<p>回滚日志中保存的是逻辑日志，当回滚日志被使用时，它只会按照日志逻辑地将数据库中的修改撤销，相当于每一条 INSERT 都对应了一条 DELETE，每一条 UPDATE 也都对应一条相反的 UPDATE 语句。</p>
+<h4 id="consistency一致性">Consistency一致性</h4>
+<p>数据库对于 ACID 中的一致性的定义是这样的：如果一个事务原子地在一个一致地数据库中独立运行，那么在它执行之后，数据库的状态一定是一致的。</p>
+<p>对于这个概念，它的第一层意思就是对于数据完整性的约束，包括主键约束、引用约束以及一些约束检查等等，在事务的执行的前后以及过程中，不会违背对数据完整性的约束，所有对数据库写入的操作都应该是合法的，并不能产生不合法的数据状态。
+第二层意思其实是指逻辑上的对于开发者的要求，我们要在代码中写出正确的事务逻辑，比如银行转账，事务中的逻辑不可能只扣钱或者只加钱，这是应用层面上对于数据库一致性的要求。</p>
+<p>数据库 ACID 中的一致性，对事务的要求不止包含对数据完整性以及合法性的检查，还包含应用层面逻辑的正确。</p>
+<h4 id="isolation隔离性">Isolation隔离性</h4>
+<p>当事务都只是串行执行的时候是不会发生问题的，然而在实际工作中，并行执行的事务才是常态，并行执行下，可能出现非常复杂的问题：</p>
+<p>当 Transaction1 在执行的过程中对 <code>id = 1</code> 的用户进行了读写，但是没有将修改的内容进行提交或者回滚，在这时 Transaction2 对同样的数据进行了读操作并提交了事务；也就是说 Transaction2 是依赖于 Transaction1 的，当 Transaction1 由于一些错误需要回滚时，因为要保证事务的原子性，需要对 Transaction2 进行回滚，但是由于我们已经提交了 Transaction2，所以我们已经没有办法进行回滚操作。
+这种现象称为不可恢复安排，这种情况是我们难以接受的，如果相关的事物都回滚，这会造成性能上的巨大损失。</p>
+<p>其实这里可以使用互斥锁来解决这个问题，比如在MySQL中，想要对读取的数据进行更新时需要使用<code>SELECT ... FOR UPDATE</code>尝试获取对应行的互斥锁，保证不同事务可以正常运行。</p>
+<p>当多个事务同时并发执行时，事务的隔离性可能就会被违反，虽然单个事务的执行可能没有任何错误，但是从总体来看就会造成数据库的一致性出现问题，而串行虽然能够允许开发者忽略并行造成的影响，能够很好地维护数据库的一致性，但是却会影响事务执行的性能。
+所以为数据库提供什么样的隔离性，也就决定了数据库的性能以及可以达到什么样的一致性。</p>
+<p>在SQL标准中定义了四种数据库的事务的隔离级别：</p>
+<ul>
+<li>RAED UNCOMMITED：使用查询语句不会加锁，可能会读到未提交的行（Dirty Read）；</li>
+<li>READ COMMITED：只对记录加记录锁，而不会在记录之间加间隙锁，所以允许新的记录插入到被锁定记录的附近，所以再多次使用查询语句时，可能得到不同的结果（Non-Repeatable Read）；</li>
+<li>REPEATABLE READ：多次读取同一范围的数据会返回第一次查询的快照，不会返回不同的数据行，但是可能发生幻读（Phantom Read）；</li>
+<li>SERIALIZABLE：InnoDB 隐式地将全部的查询语句加上共享锁，解决了幻读的问题。最高的隔离级别，完全服从 ACID 的隔离级别，所有的事务依次逐个执行，这样事务之间就完全不可能产生干扰；</li>
+</ul>
+<p>从 <code>RAED UNCOMMITED</code> 到 <code>SERIALIZABLE</code>，随着事务隔离级别变得越来越严格，每个事务的隔离级别其实都比上一级多解决了一个问题，但是数据库对于并发执行事务的性能也逐渐下降。</p>
+<table>
+<thead>
+<tr>
+<th>隔离级别</th>
+<th>脏读</th>
+<th>不可重复读</th>
+<th>幻读</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>READ-UNCOMMITTED</td>
+<td>√</td>
+<td>√</td>
+<td>√</td>
+</tr>
+<tr>
+<td>READ-COMMITTED</td>
+<td>×</td>
+<td>√</td>
+<td>√</td>
+</tr>
+<tr>
+<td>REPEATABLE-READ</td>
+<td>×</td>
+<td>×</td>
+<td>√</td>
+</tr>
+<tr>
+<td>SERIALIZABLE</td>
+<td>×</td>
+<td>×</td>
+<td>×</td>
+</tr>
+</tbody>
+</table>
+<p>数据库对于隔离级别的实现，就是使用并发控制机制对在同一时间执行的事务进行控制，限制不同的事务对于同一资源的访问和更新。</p>
+<p>锁是一种最为常见的并发控制机制，在一个事务中，并不会将整个数据库都加锁，而是只会锁住那些需要访问的数据，MySQL 和常见数据库中的锁都分为两种：读锁（共享锁）、写锁（互斥锁）。
+读锁保证了读操作可以并发执行，相互不会影响，而写锁保证了在更新数据库数据时，不会有其他的事务访问或者更改同一条记录造成不可预知的问题。</p>
+<p>除了锁，另一种实现事务隔离性的方式就是通过时间戳，但实际上就是一种乐观锁思想，PostgreSQL就是使用这种方式实现事务的数据库。
+乐观锁在读取数据时不进行加锁操作，它“乐观”地认为在此期间数据不会被其他事务修改。
+为了确保数据的一致性，在数据更新时验证数据的版本或者时间戳等标志信息，以此来判断数据是否被其他事务修改过。如果数据确实被修改过，则乐观锁的更新操作会失败，此时可以根据应用需求选择回滚事务。</p>
+<p>再有就是多版本快照隔离思想。通过维护多个版本的数据，数据库可以允许事务在数据被其他事务更新时，对旧版本的数据进行读取，很多数据库都对这一机制进行了实现，也就是 MVCC。
+MySQL 和 PostgreSQL 都对这一机制进行自己的实现。</p>
+<h4 id="durability持久性">Durability持久性</h4>
+<p>数据被写入到数据库中，那么数据一定是存储在磁盘上。事务的持久性就体现在，一旦事务被提交，那么数据一定会被写入到数据库中并持久存储起来。</p>
+<p>当事务已经被提交之后，就无法再次回滚了，唯一能够撤回已经提交的事务的方式就是创建一个相反的事务对原操作进行撤销，这也是事务持久性的体现之一。</p>
+<p>与原子性一样，事务的持久性也是通过日志来实现的，MySQL使用重做日志（redo log）实现事务的持久性。
+重做日志由两部分组成，一是内存中的重做日志缓冲区，因为它保存在内存中，所以它是易失的，另一个就是在磁盘上的重做日志文件，它是持久的。</p>
+<p>当我们在一个事务中尝试对数据进行修改时，首先会先将数据从磁盘读入内存，并更新内存中缓存的数据，然后生成一条重做日志并写入重做日志缓存。
+当事务真正提交时，MySQL会将重做日志缓存中的内容，刷新到重做日志文件，即将内存中的数据更新到磁盘上。</p>
+<p>在 InnoDB 中，重做日志都是以512字节的块的形式进行存储的，因为块的大小与磁盘扇区大小相同，所以重做日志的写入可以保证原子性，不会由于机器断电导致重做日志仅写入一半并留下脏数据。</p>
+<h3 id="mysql中的日志">MySQL中的日志</h3>
+<p>MySQL 日志 主要包括错误日志、查询日志、慢查询日志、事务日志、二进制日志几大类。
+其中，比较重要的还要属二进制日志 <code>binlog（归档日志）</code>和<code>redo log（重做|事物日志）</code>和 <code>undo log（回滚日志）</code>。</p>
+<p>简单来说，MySQL InnoDB 引擎使用 <code>redo log(重做日志)</code> 保证事务的持久性，使用 <code>undo log(回滚日志)</code> 来保证事务的原子性。
+MySQL的数据备份、主备、主主、主从都离不开 <code>binlog</code>，需要依靠 <code>binlog</code> 来同步数据，保证数据一致性。</p>
+<h3 id="mvcc并发控制机制">MVCC并发控制机制</h3>
+<p>MVCC 是一种并发控制机制，解决多个并发事务同时读写数据库产生的一些问题，用于保持数据的一致性和隔离性。</p>
+<p>它是通过在每个数据行上维护多个版本的数据来实现的。当一个事务要对数据库中的数据进行修改时，MVCC 会为该事务创建一个数据快照，而不是直接修改实际的数据行。
+读操作使用旧版本数据的快照，写操作创建新版本，并确保原版本仍可用。这样，不同的事务可以在一定程度上并发执行，而不会相互干扰。</p>
+<p>当一个事务执行读操作时，它会使用快照读取。因为是快照读取，因此其他并发事务对数据行的修改不会影响当前事务的读取操作。
+事务会查找符合条件的数据快照，并选择符合其事务开始时间的数据版本进行读取，读的是旧快照。
+如果某个数据快照有多个版本，事务会选择不晚于其开始时间的最新版本，确保事务只读取在它开始之前已经存在的数据。</p>
+<p>当一个事务执行写操作时，它会先生成一个新的数据版本快照。原始版本的数据仍然存在，供其他事务使用快照读取，这保证了其他事务不受当前事务的写操作影响。
+新版本的数据会带有当前事务的版本号，以便其他事务能够正确读取相应版本的数据。然后将修改后的数据写入新版本。</p>
+<p>当一个事务提交时，它所做的修改将成为数据库的最新版本，并且对其他事务可见。
+当一个事务回滚时，它所做的修改将被撤销，对其他事务不可见。</p>
+<p>为了防止数据库中的版本无限增长，MVCC会定期进行版本的回收。回收机制会删除已经不再需要的旧版本数据，从而释放空间。</p>
+<p>InnoDB对MVCC的实现主要是依赖于：隐藏字段、<code>Read View</code>、<code>undo log</code>。</p>
+<p>InnoDB 存储引擎为每行数据添加了三个隐藏字段:</p>
+<ul>
+<li><code>DB_TRX_ID（6字节）</code>：表示最后一次插入或更新该行的事务 id。此外，delete 操作在内部被视为更新，只不过会在记录头 Record header 中的 deleted_flag 字段将其标记为已删除；</li>
+<li><code>DB_ROLL_PTR（7字节）</code> 回滚指针，指向该行的 undo log 。如果该行未被更新，则为空；</li>
+<li><code>DB_ROW_ID（6字节）</code>：如果没有设置主键且该表没有唯一非空索引时，InnoDB 会使用该 id 来生成聚簇索引；</li>
+</ul>
+<p><code>Read View</code>主要是用来做可见性判断，里面保存了 “当前对本事务不可见的其他活跃事务”。</p>
+<p><code>undo log</code>作用是，当读取记录时，若该记录被其他事务占用或当前版本对该事务不可见，则可以通过 <code>undo log</code> 读取之前的版本数据，以此实现<strong>非锁定读</strong>。</p>
+<p>非锁定读是什么？</p>
+<p>在 InnoDB 存储引擎中，多版本控制就是对非锁定读的实现。
+如果读取的行正在执行 DELETE 或 UPDATE 操作，这时读取操作不会去等待行上锁的释放。相反地，InnoDB 存储引擎会去读取行的一个快照数据，对于这种读取历史数据的方式，我们叫它快照读，就是对非锁定读的实现。</p>
+<p>具体一点，在 <code>Repeatable Read</code> 和 <code>Read Committed</code> 两个隔离级别下，如果是执行普通的 select 语句，不包括 <code>select ... lock in share mode</code> ,<code>select ... for update</code>则会使用一致性非锁定读。</p>
+<h3 id="操作事物">操作事物</h3>
+<p>所有的存储引擎中只有 <code>InnoDB</code>、<code>NDB</code> 是事务性存储引擎，也就是说只有 <code>InnoDB</code>、<code>NDB</code> 支持事务。
+不支持的存储引擎，比如在MyISAM上操作事务，事务不会生效，SQL语句直接自动执行提交，所以回滚对于不支持事务的存储引擎是无效的。</p>
+<p>启动事务的方式：</p>
+<ul>
+<li><code>begin</code>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">mysql&gt; begin;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.00 sec)
+</span></span><span class="line"><span class="cl">mysql&gt; 事务操作SQL......
+</span></span></code></pre></div></li>
+<li><code>start transaction [修饰符]</code>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">修饰符：
+</span></span><span class="line"><span class="cl">1. read only //只读
+</span></span><span class="line"><span class="cl">2. read write //读写 默认
+</span></span><span class="line"><span class="cl">3. WITH CONSISTENT SNAPSHOT //一致性读
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 例如
+</span></span><span class="line"><span class="cl">mysql&gt; start transaction read only;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.00 sec)
+</span></span><span class="line"><span class="cl">mysql&gt; 事务操作SQL......
+</span></span></code></pre></div></li>
+</ul>
+<p>提交事物完整示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">mysql&gt; begin;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.01 sec)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; update account set balance=balance-20 where id = 1;
+</span></span><span class="line"><span class="cl">Query OK, 1 row affected (0.00 sec)
+</span></span><span class="line"><span class="cl">Rows matched: 1  Changed: 1  Warnings: 0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; update account set balance=balance+20 where id = 2;
+</span></span><span class="line"><span class="cl">Query OK, 1 row affected (0.00 sec)
+</span></span><span class="line"><span class="cl">Rows matched: 1  Changed: 1  Warnings: 0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; commit;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.01 sec)
+</span></span></code></pre></div><p>回滚事物完整示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">mysql&gt; begin;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.00 sec)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; update account set balance=balance-25 where id = 1;
+</span></span><span class="line"><span class="cl">Query OK, 1 row affected (0.00 sec)
+</span></span><span class="line"><span class="cl">Rows matched: 1  Changed: 1  Warnings: 0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; update account set balance=balance+25 where id = 2;
+</span></span><span class="line"><span class="cl">Query OK, 1 row affected (0.00 sec)
+</span></span><span class="line"><span class="cl">Rows matched: 1  Changed: 1  Warnings: 0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">mysql&gt; rollback;
+</span></span><span class="line"><span class="cl">Query OK, 0 rows affected (0.00 sec)
+</span></span></code></pre></div><p>默认是事务自动提交的，每执行一条SQL就自动提交。
+此时需要操作事务，则需要显式开启（begin or start transaction）和提交（commit）或回滚（rollback）。
+如设置成OFF，则需要执行提交（commit）或回滚（rollback）操作时才会真正执行事务。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-txt" data-lang="txt"><span class="line"><span class="cl">--查看事务开启情况：
+</span></span><span class="line"><span class="cl">mysql&gt; SHOW VARIABLES LIKE &#39;autocommit&#39;;
+</span></span><span class="line"><span class="cl">+---------------+-------+
+</span></span><span class="line"><span class="cl">| Variable_name | Value |
+</span></span><span class="line"><span class="cl">+---------------+-------+
+</span></span><span class="line"><span class="cl">| autocommit | ON |
+</span></span><span class="line"><span class="cl">+---------------+-------+
+</span></span></code></pre></div><h2 id="mysql索引">MySQL索引</h2>
+<p>MySQL官方对索引的定义为：索引（Index）是帮助MySQL高效获取数据的数据结构。
+可以得到索引的本质：索引是数据结构。</p>
+<p>索引相当于一本书的目录或者字典。
+比如，要查“mysql”这个单词，我们肯定需要定位到m字母，然后从下往下找到y字母，再找到剩下的sql；如果没有索引，那么你可能需要逐个逐个寻找。
+可以简单理解为，索引维护的就是一组排好序的数据，通过这种有序的数据结构能快速的查找到想要的数据，索引这种数据结构就是以空间换取时间。</p>
+<p>我们平常所说的索引，如果没有特别指明，都是指B树结构组织的索引。当然，除了B+树这种类型的索引之外，还有哈稀索引等。</p>
+<h3 id="索引数据结构">索引数据结构</h3>
+<p>目前大部分数据库系统及文件系统都采用B-树或其变种B+树作为索引结构。</p>
+<p>为什么使用B-树、B+树？</p>
+<p>一般来说，索引本身也很大，不可能全部存储在内存中，因此索引往往以索引文件的形式存储的磁盘上。
+这样的话，索引查找过程中就要产生磁盘I/O消耗，相对于内存存取，I/O存取的消耗要高几个数量级，所以评价一个数据结构作为索引的优劣最重要的指标，就是在查找过程中磁盘I/O操作次数的渐进复杂度。
+换句话说，索引的结构组织要尽量减少查找过程中磁盘I/O的存取次数。</p>
+<p>B树即B-tree 树，B 即 Balanced 平衡的意思。B树通过重新组织节点，降低树的高度，并且减少IO读写次数来提升效率。
+文件系统及数据库系统的设计者，利用了<strong>磁盘预读原理</strong>，将一个节点的大小设为一个页，这样每个节点只需要一次IO就可以完全载入。</p>
+<p>磁盘预读原理是什么？</p>
+<p>主存即主存储器，是计算机中最重要的存储层次之一，它直接与CPU进行数据交换。主存的访问速度很快，但价格较高，且容量有限。主存用于存储当前正在被CPU处理的数据和程序代码。
+磁盘是计算机中重要的辅助存储设备之一，磁盘的容量较大，价格较低，但访问速度较慢。磁盘通常用于长期存储大量的数据和程序代码。</p>
+<p>在存储层次结构中，磁盘通常被用作主存的扩展。当主存空间不足时，操作系统会将一些不常用的数据和程序代码从主存中移到磁盘上，以释放主存空间。
+当这些数据和程序代码再次被需要时，操作系统会将其从磁盘中读取回主存。这就是所谓的磁盘缓存。</p>
+<p>在计算机中，磁盘的读写速度远低于主存和高速缓存，但它的容量较大，可以长期保存大量的数据和程序代码，因此为了提高效率，尽量减少磁盘I/O。
+为了达到这个目的，磁盘往往不是严格按需读取，而是每次都会预读，即使只需要一个字节，磁盘也会从这个位置开始，顺序向后读取一定长度的数据放入内存，这个过程是磁盘预读。
+磁盘预读的理论依据是<strong>局部性原理</strong>，即当一个数据被用到时，其附近的数据也通常会马上被使用。</p>
+<p>磁盘预读的长度一般为页的整倍数。页是计算机管理存储器的逻辑块，硬件及操作系统往往将主存和磁盘存储区分割为连续的大小相等的块，每个存储块称为一页（在许多操作系统中，页得大小通常为4k），主存和磁盘以页为单位交换数据。
+当程序要读取的数据不在主存中时，会触发一个缺页异常，此时系统会向磁盘发出读盘信号，磁盘会找到数据的起始位置并向后连续读取一页或几页载入内存中，然后异常返回，程序继续运行。</p>
+<h3 id="索引的实现">索引的实现</h3>
+<p>在MySQL中，索引属于存储引擎级别的概念，不同存储引擎对索引的实现方式是不同的，这里主要讨论MyISAM、InnoDB两个不同的存储引擎对索引实现方式。</p>
+<h4 id="myisam索引的实现">MyISAM索引的实现</h4>
+<p>在MyISAM引擎中，建立的索引文件和数据文件是分离的，B+Tree 叶节点存放的是数据记录的地址。</p>
+<p><img alt="MyISAM索引结构" src="/iblog/posts/annex/images/essays/MyISAM%E7%B4%A2%E5%BC%95%E7%BB%93%E6%9E%84.png"></p>
+<p>在索引检索的时候，首先按照 B+Tree 搜索算法搜索索引，如果指定的 Key 存在，则取出其叶子结点的值，然后以叶子结点的值为地址读取相应的数据记录。
+这种表示索引结构与数据行存储顺序无关的索引，叫做非聚集索引。</p>
+<p>MyISAM中的主索引和辅助索引在结构上是类似的，都是采用B-Tree结构。它们之间的主要区别在于，主索引要求索引列的值必须唯一，而辅助索引则可以包含重复值。
+但是无论主索引还是辅助索引，它们的叶子节点存储的都是指向数据行实际存储位置的指针，而不是数据本身。
+因此，当通过索引访问数据时，MyISAM 需要进行两次查找：首先在索引中找到对应记录的位置，然后根据该位置读取实际的数据行。</p>
+<h4 id="innodb索引的实现">InnoDB索引的实现</h4>
+<p>在InnoDB引擎中，其数据文件本身就是索引文件。</p>
+<p><img alt="Innodb索引结构" src="/iblog/posts/annex/images/essays/Innodb%E7%B4%A2%E5%BC%95%E7%BB%93%E6%9E%84.png"></p>
+<p>表数据文件本身就是按B+Tree组织的一个索引结构，这棵树的叶节点data域保存了完整的数据记录。这个索引的key是数据表的主键，因此InnoDB表数据文件本身就是<strong>主索引</strong>。
+索引的键值决定了表中数据的物理顺序，这种被称为聚簇索引或聚集索引。</p>
+<p>因为InnoDB的数据文件本身要按主键聚集，所以InnoDB要求表必须有主键，MyISAM可以没有。
+如果没有显式指定，则MySQL系统会自动选择一个可以唯一标识数据记录的列作为主键。
+如果不存在这种列，则MySQL自动为InnoDB表生成一个隐含字段作为主键，这个字段长度为6个字节，类型为长整形。</p>
+<p>与MyISAM索引的不同是，InnoDB的<strong>辅助索引</strong>data域，存储相应记录主键的值而不是地址。
+换句话说，辅助索引的叶节点存储的是主键值，加上一个指向主键的指针，而不是实际的数据行。
+这意味着，当通过辅助索引查询数据时，数据库首先通过辅助索引找到主键，然后用主键到聚簇索引中去查找对应的完整数据行，这个过程称为回表查询。</p>
+<p>知道了InnoDB的索引实现后，就很容易明白为什么不建议使用过长的字段作为主键，因为所有辅助索引都引用主索引，过长的主索引会令辅助索引变得过大。
+再例如，用非单调递增或递减的字段作为主键在InnoDB中也不是个好主意，因为InnoDB数据文件本身是一颗B+Tree，非单调的主键会造成在插入新记录时数据文件为了维持B+Tree的特性而频繁的分裂调整，十分低效，而使用自增字段作为主键则是一个很好的选择。</p>
+<p>主索引、辅助索引是什么？</p>
+<ul>
+<li>主索引通常是基于表的主键建立的索引，保证了索引列值的唯一性。在InnoDB存储引擎中，主索引实际上是一个聚簇索引，这意味着主键不仅提供唯一性约束，还决定了数据行的物理排列顺序。
+在MyISAM中，主索引通常是基于表的一个唯一键创建的，最常见的是基于主键。如果未明确定义主键，MyISAM 会尽可能选择一个唯一的非空索引作为主索引。</li>
+<li>辅助索引是相对于主索引而言，指除主索引之外的其他索引，可以是基于非主键列创建的索引，用于加速对这些列的查询。
+在InnoDB存储引擎中辅助索引的叶子结点存储的是主键值。在MyISAM中，叶子节点存储的是指向数据行实际存储位置的指针。</li>
+</ul>
+<h3 id="索引的优缺点">索引的优缺点</h3>
+<p>索引的优点：</p>
+<ul>
+<li>提高数据检索的效率，降低数据库的IO成本；</li>
+<li>降低数据排序的成本，降低了CPU的消耗；</li>
+</ul>
+<p>索引的缺点：</p>
+<ul>
+<li>索引本身很大，可以放在内存、硬盘中，通常为硬盘；</li>
+<li>索引虽然提高了查询的效率，但是会降低增删改的效率，当对表中的数据进行增删改的时候，如果数据有索引，那么索引也需要动态的修改，也就是会降低 SQL 执行效率；</li>
+</ul>
+<h3 id="索引分类">索引分类</h3>
+<p>按照应用维度划分：</p>
+<ul>
+<li>主键索引：属于唯一索引的一种，但是值不能为null；</li>
+<li>唯一索引：索引列的值必须唯一，但允许有空值；</li>
+<li>单值索引：即一个索引只包含单个列，一个表可以有多个单列索引；</li>
+<li>复合索引：一个索引包含多个列；</li>
+</ul>
+<p>按照底层存储方式角度划分：</p>
+<ul>
+<li>聚簇索引（聚集索引）：索引结构和数据一起存放的索引，InnoDB 中的主键索引就属于聚簇索引。</li>
+<li>非聚簇索引（非聚集索引）：索引结构和数据分开存放的索引，二级索引(辅助索引)就属于非聚簇索引。MySQL 的 MyISAM 引擎，不管主键还是非主键，使用的都是非聚簇索引。</li>
+</ul>
+<h3 id="操作索引">操作索引</h3>
+<p>创建索引：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> CREATE [UNIQUE] INDEX indexName ON mytable(columnName(length));
+</span></span><span class="line"><span class="cl"> ALTER mytable ADD [UNIQUE] INDEX [indexName] ON (columnName(length));
+</span></span></code></pre></div><p>删除索引：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> DROP INDEX [indexName] ON [tableName];
+</span></span></code></pre></div><p>修改索引：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">-- 该语句添加一个主键，这意味着索引值必须是唯一的，且不能为NULL
+</span></span><span class="line"><span class="cl"> ALTER TABLE [tableName] ADD PRIMARY KEY (column_list);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 这条语句创建索引的值必须是唯一的(除了NULL外，NULL可能会出现多次)
+</span></span><span class="line"><span class="cl"> ALTER TABLE [tableName] ADD UNIQUE [indexName] (column_list);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 添加普通索引，索引值可出现多次
+</span></span><span class="line"><span class="cl"> ALTER TABLE [tableName] ADD INDEX [indexName] (column_list);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 该语句指定了索引为FULLTEXT，用于全文索引
+</span></span><span class="line"><span class="cl"> ALTER TABLE [tableName] ADD FULLTEXT [indexName] (column_list);
+</span></span></code></pre></div><p>查看索引：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> SHOW INDEX FROM [tableName];
+</span></span></code></pre></div><h3 id="最左前缀匹配原则">最左前缀匹配原则</h3>
+<p>最左前缀匹配原则是指在使用复合索引，即包含多个列的索引时，MySQL优化器会尽可能地根据索引中的字段顺序，从左到右依次匹配查询条件中的字段。
+如果查询条件与索引中的最左侧字段相匹配，那么 MySQL 就会使用索引来过滤数据，这样可以提高查询效率。</p>
+<p>想要发挥最左前缀匹配的效果，你的查询条件应该至少从复合索引的第一列开始，并且尽可能地包含更多连续的索引列。
+如果查询条件没有从第一列开始或者跳过了中间的列，那么索引的部分或全部效果就可能没法用了。</p>
+<p>现在有一个students表，它有三个列(id, first_name, last_name)，并且针对这三个列创建了一个复合索引(id, first_name, last_name)。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-sql" data-lang="sql"><span class="line"><span class="cl"><span class="c1">-- 可以命中索引
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="k">select</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">from</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="k">where</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">first_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;lisa&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">last_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;liu&#39;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">-- 无法命中索引
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="k">select</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">from</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="k">where</span><span class="w"> </span><span class="n">first_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;lisa&#39;</span><span class="w">
+</span></span></span></code></pre></div><p>联合索引的最左匹配原则，在遇到范围查询（如 &gt;、&lt;）的时候，就会停止匹配，也就是范围查询的字段可以用到联合索引，但是在范围查询字段后面的字段无法用到联合索引。
+但是对于 &gt;=、&lt;=、BETWEEN、like 前缀匹配这四种范围查询，并不会停止匹配。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-sql" data-lang="sql"><span class="line"><span class="cl"><span class="c1">-- 可以命中 id、first_name列，没命中last_name 列
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="k">select</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">from</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="k">where</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;%123%&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">first_name</span><span class="w"> </span><span class="k">like</span><span class="w"> </span><span class="s1">&#39;%lisa%&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">last_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;liu&#39;</span><span class="w">
+</span></span></span></code></pre></div><h3 id="索引覆盖">索引覆盖</h3>
+<p>覆盖索引（Covering Index），一说为索引覆盖。如果一个索引包含或者说覆盖所有需要查询的字段的值，就称为索引覆盖。</p>
+<p>查询的数据列从索引文件中就能够取得，不必读取原数据、回表查询。
+MySQL可以利用索引返回select列表中的字段，而不用根据索引再次读取数据文件，换句话说查询到的列全部都在索引列中就是索引覆盖。</p>
+<p>如果要使用覆盖索引，一定要注意select列表中只取出需要的列，不可select*，因为如果将所有字段一起做索引会导致索引文件过大，查询性能下降。</p>
+<p>覆盖索引举例，(id, first_name, last_name)为一个复合索引。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-sql" data-lang="sql"><span class="line"><span class="cl"><span class="c1">--  覆盖索引，全部命中
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="k">select</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="n">first_name</span><span class="p">,</span><span class="n">last_name</span><span class="w"> </span><span class="k">from</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="k">where</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;%123%&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">first_name</span><span class="w"> </span><span class="k">like</span><span class="w"> </span><span class="s1">&#39;%lisa%&#39;</span><span class="w"> </span><span class="k">and</span><span class="w"> </span><span class="n">last_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;liu&#39;</span><span class="w">
+</span></span></span></code></pre></div><h3 id="索引建立原则">索引建立原则</h3>
+<p>既然索引可以加快查询速度，那么是不是只要是查询语句需要，就建上索引？
+答案肯定是不可以。索引虽然加快了查询速度，但索引也是有代价的：索引文件本身要消耗存储空间，同时索引会加重插入、删除和修改记录时的负担，另外MySQL在运行时也要消耗资源维护索引，因此索引并不是越多越好。</p>
+<p>以下是建立索引的一些原则：</p>
+<ul>
+<li>数据量很小则不适合建立：如果数据库的数据量不大，那么使用索引也不一定能够带来很大提升，所以没有必要建立索引；</li>
+<li>不要建立太多的索引：因为维护索引是需要耗费空间和性能的，MySQl会为了每一个索引维护一个B树，如果索引过多，这无疑是增加了MySQL的负担；</li>
+<li>频繁增删改的字段不要建立索引：如果某个字段频繁修改，那就意味着也需要修改索引，这必然影响MySQL的性能；</li>
+<li>为频繁查询的字段建立索引：建立索引要为经常作为查询条件的字段建立索引，这样能提高SQL的查询效率，与之相反的不要为很少使用的字段建立索引；</li>
+<li>避免为”大字段”建立索引：就是尽量使用字段长度小的字段作为索引；例如，要为<code>varchar(5)</code>和<code>varchar(200)</code>的字段建立索引，则优先考虑为<code>varchar(5)</code>的建立；如果非要为<code>varchar(200)</code>的字段建立索引那么可以这样：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">为</span><span class="n">varchar</span><span class="p">(</span><span class="mi">200</span><span class="p">)</span><span class="err">的字段建立索引，将其长度设置为</span> <span class="mi">20</span>  
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">index</span>  <span class="n">tbl_001</span> <span class="n">on</span> <span class="n">dual</span><span class="p">(</span><span class="n">address</span><span class="p">(</span><span class="mi">20</span><span class="p">));</span>
+</span></span></code></pre></div></li>
+<li>选择数据区分大的列建立索引：如果某个字段包含许多重复的数据则不适合建立索引。假设现在有一个”性别”字段，里面存放的数据的值要么是男，要么是女，这样的字段很不适合作为索引。
+因为如果值出现的几率几乎相等，那么无论搜索哪个值都可能得到一半的数据。在这些情况下，还不如不要索引，因为MySQL他还有一个查询优化器，查询优化器发现某个值出现在表的数据行中的百分比很高的时候，它一般会忽略索引，进行全表扫描。
+惯用的百分比界线是”30%”。匹配的数据量超过一定限制的时候查询器会放弃使用索引，这也是索引失效的场景之一。</li>
+</ul>
+<h3 id="避免索引失效原则">避免索引失效原则</h3>
+<p>建立索引之后还要保证索引生效，才能发挥索引的作用，以下是避免索引失效的原则：</p>
+<ul>
+<li>在使用复合索引时，不要跨列使用或无序使用，即最佳左前缀法则，否则索引失效；
+跨列使用指，where后边的字段和order by后边的字段拼接起来，看是否满足索引的顺序，如不满足则为跨列，会出现Using filsort。</li>
+<li>不要在索引上进行任何操作，例如：计算、函数运算、类型转换等，否则索引失效；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- age列为索引，但此时SQL语句age列存在计算，age索引列失效；
+</span></span><span class="line"><span class="cl"> select * from tbl_001 where age*3 = &#39;10&#39;;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- name为索引列，此时在该索引列上进行函数计算，name索引列失效；
+</span></span><span class="line"><span class="cl"> select * from tbl_001 tbl_001 left(name,4)=&#39;July&#39;; 
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- typeid为索引列，typeid为int类型，此时发生隐式类型转换，typeid索引列失效；
+</span></span><span class="line"><span class="cl"> select * from tbl_001 c typeid = &#39;1&#39;;
+</span></span></code></pre></div></li>
+<li>复合索引不能使用不等于（!=、&lt;&gt;）或is null、is not null，否则自身及右侧索引全部失效；
+大部分情况下如果复合索引使用上面的运算符索引会失效，但是MySQL在服务层存在SQL优化阶段，所以复合索引即使使用了不等于、is null、is not null等操作，还是可能会存在索引生效的情况。</li>
+<li>尽量使用覆盖索引，使用覆盖索引会提高系统性能；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name、tid、cid 为复合索引
+</span></span><span class="line"><span class="cl">  select name,tid,cid from tbl_001 where name = &#39;zs&#39;;
+</span></span></code></pre></div></li>
+<li>like尽量以常量开头，不要以%开头，否则索引失效；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name 为索引列，此处索引失效
+</span></span><span class="line"><span class="cl"> select * from tbl_002 where name like &#39;%x%&#39;;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 如果必须要使用%开头，可以使用覆盖索引挽救一下
+</span></span><span class="line"><span class="cl"> select name from tbl_002 where name like &#39;%x%&#39;;
+</span></span></code></pre></div></li>
+<li>不要使用or，否则索引失效；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- authorid、typeid为复合索引，此处or的左右两边索引全部失效
+</span></span><span class="line"><span class="cl"> select * from book_2021 where authorid = 1 or typeid = 1;
+</span></span></code></pre></div></li>
+<li>避免使用<code>*</code>，因为使用<code>*</code>之后MySQL还需要计算把<code>*</code>替换成对应的列；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">-- 不要使用*，把*替换成具体需要的列
+</span></span><span class="line"><span class="cl"> select * from book_2021;
+</span></span></code></pre></div></li>
+</ul>
+<h2 id="mysql执行计划">MySQL执行计划</h2>
+<p>执行计划 是指一条 SQL 语句在经过 MySQL 查询优化器 的优化后，具体的执行方式。
+使用explain关键字可以模拟优化器执行SQL查询语句，从而知道MySQL是如何处理你的SQL语句的，分析你的查询语句或是表结构的性能瓶颈。
+explain不止适用于select也适用于delete、insert、replace和update语句。</p>
+<p>当explain可解释语句一起使用时，MySQL会显示来自优化器的关于语句执行计划的信息，也就是说，MySQL解释了它将如何处理语句，包括有关表如何连接以及按顺序连接的信息。</p>
+<p>在MySQL中执行任意一条SQL前加上explain关键字，即可看到：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> +----+-------------+----------+------+---------------+------+---------+------+------+-------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table    | type | possible_keys | key  | key_len | ref  | rows | Extra |
+</span></span><span class="line"><span class="cl"> +----+-------------+----------+------+---------------+------+---------+------+------+-------+
+</span></span></code></pre></div><h3 id="idtable">id、table</h3>
+<p>table是显示这一行的数据是关于哪张表的。</p>
+<p>id是select查询的序列号，包含一组数字，表示查询中执行select子句或操作表的顺序。</p>
+<ul>
+<li>id值相同，执行顺序由上至下；</li>
+<li>id值不同，id值越大优先级越高，越先被执行；</li>
+</ul>
+<blockquote>
+<p>表的执行顺序与表中数据息息相关，举个例子：表A：3条数据 表B：4条数据 表C：6条数据</p>
+<p>假设在执行某条SQL的情况下表A、B、C的id值相同，假设执行顺序：表A、B、C。在给表B添加4条数据后，再次执行前面的这条SQL发现执行顺序变为：表A、C、B。
+<br>
+这是因为中间结果会影响表的执行顺序：
+3 * 4 * 2 = 12 * 2 = 24
+3 * 2 * 4 = 6 * 4 = 24
+虽然最后结果一样，但是中间过程不一样。中间过程越小占用的空间越小，所以在ID值相同的情况下数据小的表优先查询。</p>
+</blockquote>
+<h3 id="select_type">select_type</h3>
+<p>select_type是查询的类型，主要是用于区别普通查询、联合查询、子查询等的复杂查询。</p>
+<p>查询类型：</p>
+<ul>
+<li>PRIMARY：包含自查询的主查询，最外层部分；</li>
+<li>SUBQUERY：查询语句中包含了子查询，非最外层；</li>
+<li>SIMPLE：简单查询,即SQL中不包含子查询或者UNION查询；</li>
+<li>DERIVED：在查询过程中创建了临时表，例如SQL：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select name from (select * from table1) t1;
+</span></span></code></pre></div></li>
+<li>UNION：若第二个SELECT出现在UNION之后，则被标记为UNION；若UNION包含在FROM子句的子查询中外层SELECT将被标记为：DERIVED；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select name from (select * from table1 union select * from table2) t1;
+</span></span></code></pre></div></li>
+<li>UNION RESULT：从UNION表中的结果；</li>
+</ul>
+<h3 id="type">type</h3>
+<p>type是索引类型，是较为重要的一个指标，结果值从最好到最坏依次是：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="n">system</span> <span class="o">&gt;</span> <span class="k">const</span> <span class="o">&gt;</span> <span class="n">eq_ref</span> <span class="o">&gt;</span> <span class="n">ref</span> <span class="o">&gt;</span> <span class="n">fulltext</span> <span class="o">&gt;</span> <span class="n">ref_or_null</span> <span class="o">&gt;</span> <span class="n">index_merge</span> <span class="o">&gt;</span> <span class="n">unique_subquery</span> <span class="o">&gt;</span> <span class="n">index_subquery</span> <span class="o">&gt;</span> <span class="nb">range</span> <span class="o">&gt;</span> <span class="n">index</span> <span class="o">&gt;</span><span class="n">ALL</span>
+</span></span></code></pre></div><p>实际工作中可能用不到这么多，一般只要记住以下就行了：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="n">system</span> <span class="o">&gt;</span> <span class="k">const</span> <span class="o">&gt;</span> <span class="n">eq_ref</span> <span class="o">&gt;</span> <span class="n">ref</span> <span class="o">&gt;</span> <span class="nb">range</span> <span class="o">&gt;</span> <span class="n">index</span> <span class="o">&gt;</span> <span class="n">ALL</span>
+</span></span></code></pre></div><p>其中system、const只是理想情况，实际能达到ref、range。</p>
+<p>常见索引类型：</p>
+<ul>
+<li>system：表只有一行记录的系统表，或衍生表只有一行数据的主查询；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 衍生表：(select * from tbl_001) 只有一条记录；id为主键索引
+</span></span><span class="line"><span class="cl"> explain select * from (select * from tbl_001) where id = 1;
+</span></span></code></pre></div></li>
+<li>const：仅仅能查询到一条记录的SQL，并且用于主键索引或者唯一键索引；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- tbl_001表只有一条记录；id为主键索引或唯一键索引
+</span></span><span class="line"><span class="cl"> explain select * from tbl_001 where id = 1;
+</span></span></code></pre></div></li>
+<li>eq_ref：唯一性索引；对于每个索引键的查询，返回匹配唯一一行的数据,有且只有一个，不能多也不能为0；常见于主键或唯一索引扫描；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- tbl_001.tid为索引列；且tbl_001与tbl_002表中数据记录一一对应
+</span></span><span class="line"><span class="cl"> select * from tbl_001,tbl_002 where tbl_001.tid = tbl_002.id
+</span></span></code></pre></div></li>
+<li>ref：非唯一性索引；对于每个索引键的查询，返回多个匹配的所有行，包括0个；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name 为索引列；tbl_001 表中 name 值为 zs 的有多个
+</span></span><span class="line"><span class="cl"> explain select * from tbl_001 where name = &#39;zs&#39;;
+</span></span></code></pre></div></li>
+<li>range：检索指定范围的行，where后面是一个范围查询常见：between and、in、&gt;、&lt;=；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- tid 为索引列；
+</span></span><span class="line"><span class="cl"> explain select * from tbl_001 where tid &lt;=3;
+</span></span></code></pre></div></li>
+<li>index：查询全部索引中的数据；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name为索引列；
+</span></span><span class="line"><span class="cl"> explain select name from tbl_001;
+</span></span></code></pre></div></li>
+<li>all：查询全部表中的数据；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name不是索引列；
+</span></span><span class="line"><span class="cl"> explain select name from tbl_001;
+</span></span></code></pre></div></li>
+</ul>
+<h3 id="possible_keyskey">possible_keys、key</h3>
+<p>possible_keys是可能用到的索引，是一种预测,不准确；key是实际用到的索引，如果为null则没有用到索引。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- name为索引列
+</span></span><span class="line"><span class="cl"> explain select name from tbl_001;
+</span></span><span class="line"><span class="cl"> +----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table   | type  | possible_keys | key      | key_len | ref  | rows | Extra       |
+</span></span><span class="line"><span class="cl"> +----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | tbl_001 | index | NULL          | idx_name | 83      | NULL |    4 | Using index |
+</span></span><span class="line"><span class="cl"> +----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+
+</span></span></code></pre></div><h3 id="key_len">key_len</h3>
+<p>key_len索引使用的长度，可通过索引列长度，例如：<code>name vachar(20)</code>，来判断复合索引到底有没有使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name为索引列</span><span class="err">；可以为</span><span class="n">null</span><span class="err">；</span><span class="n">varchar类型</span><span class="err">；</span><span class="n">utf8字符集</span><span class="err">；</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="n">name</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span>  <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>      <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">index</span> <span class="o">|</span> <span class="n">NULL</span>          <span class="o">|</span> <span class="n">idx_name</span> <span class="o">|</span> <span class="mi">63</span>      <span class="o">|</span> <span class="n">NULL</span> <span class="o">|</span>    <span class="mi">4</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+-------+---------------+----------+---------+------+------+-------------+</span>
+</span></span></code></pre></div><p>其中，如果索引字段可以为null，MySQL会用一个字节进行标识；varchar为可变长度，MySQL用两个字节来标识。</p>
+<blockquote>
+<p>utf8：一个字符三个字节；
+gbk：一个字符两个字节；
+latin：一个字符一个字节；</p>
+</blockquote>
+<p>举例，字段<code>name vachar(20)</code>，不能为null，utf8编码，执行执行计划name列使用到了索引那么key_len等于<code>20*3+1+2=63</code>。</p>
+<h3 id="ref">ref</h3>
+<p>ref指明当前表所引用的字段。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">其中</span><span class="n">b</span><span class="o">.</span><span class="n">d可以为常量</span><span class="err">，常量用</span> <span class="k">const</span> <span class="err">标识</span>
+</span></span><span class="line"><span class="cl"> <span class="n">select</span> <span class="o">...</span> <span class="n">where</span> <span class="n">a</span><span class="o">.</span><span class="n">c</span> <span class="o">=</span> <span class="n">b</span><span class="o">.</span><span class="n">d</span><span class="p">;</span>  
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">tid</span> <span class="err">为索引列</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">t1</span><span class="p">,</span><span class="n">tbl_002</span> <span class="n">t2</span> <span class="n">where</span> <span class="n">t1</span><span class="o">.</span><span class="n">tid</span> <span class="o">=</span> <span class="n">t2</span><span class="o">.</span><span class="n">id</span> <span class="ow">and</span> <span class="n">t1</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+--------+------------------+----------+---------+-----------------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span> <span class="o">|</span> <span class="n">type</span>   <span class="o">|</span> <span class="n">possible_keys</span>    <span class="o">|</span> <span class="n">key</span>      <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>             <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+--------+------------------+----------+---------+-----------------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">t1</span>    <span class="o">|</span> <span class="n">ref</span>    <span class="o">|</span> <span class="n">idx_name</span><span class="p">,</span><span class="n">idx_tid</span> <span class="o">|</span> <span class="n">idx_name</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span>           <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">where</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">t2</span>    <span class="o">|</span> <span class="n">eq_ref</span> <span class="o">|</span> <span class="n">PRIMARY</span>          <span class="o">|</span> <span class="n">PRIMARY</span>  <span class="o">|</span> <span class="mi">4</span>       <span class="o">|</span> <span class="n">sql_demo</span><span class="o">.</span><span class="n">t1</span><span class="o">.</span><span class="n">tid</span> <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span> <span class="n">NULL</span>        <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+--------+------------------+----------+---------+-----------------+------+-------------+</span>
+</span></span></code></pre></div><h3 id="rows">rows</h3>
+<p>rows表示查询行数，实际通过索引查询到的个数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> mysql&gt; select * from tbl_001 t1,tbl_002 t2 where t1.tid = t2.id and t1.name = &#39;ls&#39;;
+</span></span><span class="line"><span class="cl"> +----+------+------+----+------+-------+-------+
+</span></span><span class="line"><span class="cl"> | id | name | tid  | id | name | name1 | name2 |
+</span></span><span class="line"><span class="cl"> +----+------+------+----+------+-------+-------+
+</span></span><span class="line"><span class="cl"> |  2 | ls   |    2 |  2 | ls   | ls1   | ls2   |
+</span></span><span class="line"><span class="cl"> |  4 | ls   |    1 |  1 | zs   | zs1   | zs2   |
+</span></span><span class="line"><span class="cl"> +----+------+------+----+------+-------+-------+
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> mysql&gt; explain select * from tbl_001 t1,tbl_002 t2 where t1.tid = t2.id and t1.name = &#39;ls&#39;;
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+-------+------------------+------------+---------+----------------+------+-------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table | type  | possible_keys    | key        | key_len | ref            | rows | Extra       |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+-------+------------------+------------+---------+----------------+------+-------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | t2    | index | PRIMARY          | index_name | 249     | NULL           |    2 | Using index |
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | t1    | ref   | idx_name,idx_tid | idx_tid    | 5       | sql_demo.t2.id |    1 | Using where |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+-------+------------------+------------+---------+----------------+------+-------------+
+</span></span></code></pre></div><h3 id="extra">Extra</h3>
+<p>Extra包含不适合在其他列中显示但十分重要的额外信息。</p>
+<p>常见值：</p>
+<ul>
+<li>Using filesort：文件内排序；出现这个值代表额外的一次排序（查询），性能消耗比较大，需要进行SQL优化。常见order by语句中；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span> <span class="err">为单值索引</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span> <span class="n">order</span> <span class="n">by</span> <span class="n">tid</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+----------+---------+-------+------+----------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>      <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>          <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+----------+---------+-------+------+----------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_name</span>      <span class="o">|</span> <span class="n">idx_name</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">filesort</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+----------+---------+-------+------+----------------+</span>
+</span></span></code></pre></div>对于单值索引来说，如果排序和查找的是同一个字段，则不会出现 Using filesort 反之则出现;一般通过where哪些字段就 orderby 哪些字段来避免。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span><span class="err">，</span><span class="n">tid</span> <span class="err">为复合索引</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span> <span class="n">order</span> <span class="n">by</span> <span class="n">tid</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+-----------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>       <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+-----------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_trans</span>     <span class="o">|</span> <span class="n">idx_trans</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+-----------+---------+-------+------+-------------+</span>
+</span></span></code></pre></div>对于复合索引来说要按照建立复合索引的顺序来使用，不要跨列或者无序使用。
+<blockquote>
+<p>跨列使用指，where后边的字段和order by后边的字段拼接起来，看是否满足索引的顺序，如不满足则为跨列，会出现Using filsort。</p>
+</blockquote>
+</li>
+<li>Using temporary：使了用临时表保存中间结果，MysQL在对查询结果排序时使用临时表。性能消耗也是很大的，一般出现这个词需要进行SQL优化。常见于分组查询group by语句；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span><span class="err">、</span><span class="n">tid</span><span class="err">、</span><span class="n">cid</span> <span class="err">为复合索引</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="n">name</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span> <span class="n">group</span> <span class="n">by</span> <span class="n">cid</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>     <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>                        <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_ntc</span>       <span class="o">|</span> <span class="n">idx_ntc</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>    <span class="mi">2</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span><span class="p">;</span> <span class="n">Using</span> <span class="n">temporary</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+------------------------------+</span>
+</span></span></code></pre></div>Using temporary出现的原因，已经有表了但是不使用，必须再来一张表。我们可以通过查询哪些列，就通过哪些列来分组来避免。</li>
+<li>Using index：出现这个值代表性能还是不错的；表示使用到了覆盖索引，不读取源文件，只从索引文件中获取数据，不需要回表查询。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span><span class="err">、</span><span class="n">tid</span><span class="err">、</span><span class="n">cid</span> <span class="err">为复合索引</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="n">name</span><span class="p">,</span><span class="n">tid</span><span class="p">,</span><span class="n">cid</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>     <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_ntc</span>       <span class="o">|</span> <span class="n">idx_ntc</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>    <span class="mi">2</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span></code></pre></div>如果用到了索引覆盖时，会对possible_key和key造成影响：
+<ul>
+<li>如果没有使用到where，则索引只出现在key中；</li>
+<li>如果有where，则索引出现在key和possible_key中；</li>
+</ul>
+</li>
+<li>Using where：出现这个值代表需要回表查询；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="n">name</span> <span class="err">为单值索引，此时索引中不包含其他字段，想要查询其他字段就必须回表查询</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="n">name</span><span class="p">,</span><span class="n">tid</span><span class="p">,</span><span class="n">cid</span> <span class="n">from</span> <span class="n">tbl_001</span> <span class="n">where</span> <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;zs&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span>   <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span> <span class="o">|</span> <span class="n">key</span>     <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>   <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">tbl_001</span> <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_name</span>      <span class="o">|</span> <span class="n">idx_name</span> <span class="o">|</span> <span class="mi">83</span>     <span class="o">|</span> <span class="k">const</span> <span class="o">|</span>   <span class="mi">2</span>  <span class="o">|</span> <span class="n">Using</span> <span class="n">where</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+---------+------+---------------+---------+---------+-------+------+-------------+</span>
+</span></span></code></pre></div></li>
+<li>Impossible WHERE：where语句永远为false，永远不成立；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select * from tbl_001 where name = &#39;zs&#39; and name = &#39;ls&#39;;
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------+---------------+------+---------+------+------+------------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra            |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------+---------------+------+---------+------+------+------------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | Impossible WHERE |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------+---------------+------+---------+------+------+------------------+
+</span></span></code></pre></div></li>
+</ul>
+<h2 id="mysql优化">MySQL优化</h2>
+<p>为什么要进行优化？</p>
+<ul>
+<li>SQL语句欠佳、执行过程耗时较长、索引失效；</li>
+<li>单库数据量越来越大，存储出现问题；</li>
+<li>在高并发场景下，大量请求阻塞；</li>
+</ul>
+<p>总之一句话，数据库出现性能瓶颈。</p>
+<h3 id="sql执行过程">SQL执行过程</h3>
+<p>想要进行SQL优化首先要弄懂SQL编写过程和SQL执行过程是存在区别的：</p>
+<ul>
+<li>SQL编写过程：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> select distinct .. from .. join .. on .. where .. group by .. having .. order by .. limit ..
+</span></span></code></pre></div></li>
+<li>SQL执行过程：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> from .. on .. join ..  where .. group by .. having .. select distinct .. order by .. limit ..
+</span></span></code></pre></div></li>
+</ul>
+<p>之所以SQL的编写过程会和执行过程有区别，是因为MySQL中有专门负责优化Select语句的优化器模块。</p>
+<blockquote>
+<p>MySQL Query Optimizer：MySQL查询优化器。主要功能:通过计算分析系统中收集到的统计信息，为客户端请求的Select提供MySQL认为最优的执行计划。</p>
+</blockquote>
+<p>当客户端向MySQL请求一条Select，命令解析器模块完成请求分类，区别出是Select并转发给MySQL Query Optimizer时，MySQL Query Optimizer首先会对整条Select进行优化，处理掉一些常量表达式的预算直接换算成常量值。
+并对Select中的查询条件进行简化和转换，如去掉一些无用或显而易见的条件、结构调整等。然后分析Select中的Hint信息，看显示Hint信息是否可以完全确定该Select的执行计划。如果没有Hint或Hint信息还不足以完全确定执行计划，则会读取所涉及对象的统计信息，根据Query进行写相应的计算分析，然后再得出最后的执行计划。</p>
+<blockquote>
+<p>Hint: 简单来说就是在某些特定的场景下人工协助MySQL优化器的工作，使其生成最优的执行计划。
+一般来说，优化器的执行计划都是最优化的，不过在某些特定场景下，执行计划可能不是最优化。</p>
+</blockquote>
+<h3 id="优化思路">优化思路</h3>
+<p>数据库性能优化方案很多，主要分为两大类：软件层面、硬件层面。</p>
+<p>软件层面包括：SQL 调优、表结构优化、读写分离、数据库集群、分库分表等；硬件层面主要是增加机器性能。下面是集中常见的优化思路：</p>
+<ol>
+<li>
+<p>SQL调优主要目的是尽可能的让那些慢 SQL 变快，手段其实也很简单就是让 SQL 执行尽量命中索引：</p>
+<ul>
+<li>避免在 where 子句中对字段进行 null 值判断，创建表默认值是 NULL。尽量使用 NOT NULL，或使用特殊值，如 0、-1</li>
+<li>避免在 where 子句中使用 != 或 &lt;&gt; 操作符， MySQL 只有对以下操作符才使用索引：&lt;、&lt;=、=、&gt;、&gt;=、BETWEEN、IN、非 % 开头的 LIKE</li>
+<li>避免在 where 子句中使用 or 来连接条件，可以使用 UNION 进行连接</li>
+<li>能用 union all 就不用 union，union 过滤重复数据要耗费更多的 CPU 资源</li>
+<li>避免全部 like 查询，如 &lsquo;%ConstXiong%&rsquo;</li>
+<li>避免在索引列上使用计算、函数</li>
+<li>in 和 not in 慎用，能用 between 不要用 in</li>
+<li>select 子句中避免使用 *</li>
+<li>根据 where 和 order by 使用比较频繁的字段创建索引，提高查询效率</li>
+<li>索引不宜过多，单表最好不要超过 6 个。索引过多会导致占用存储空间变大；insert、update 变慢</li>
+<li>删除未使用的索引</li>
+</ul>
+</li>
+<li>
+<p>如果是单表数据量太大，解决办法：</p>
+<ul>
+<li>分页查询(在索引上完成排序分页操作、借助主键进行关联)</li>
+<li>单表数据过大，进行分库分表</li>
+<li>考虑使用非关系型数据库提高查询效率</li>
+<li>全文索引场景较多，考虑使用 ElasticSearch、solr</li>
+</ul>
+</li>
+<li>
+<p>其他优化：</p>
+<ul>
+<li>数据库配置参数调整</li>
+<li>数据库表结构优化</li>
+<li>硬件优化，增加服务器数量，扩大服务器内存，CPU核数</li>
+</ul>
+</li>
+</ol>
+<h3 id="排查慢sql">排查慢SQL</h3>
+<p>想要优化SQL，首先要找到慢SQL，慢SQL日志超过响应时间的阈值默认10秒，便会记录该SQL。
+慢SQL日志默认是关闭的，建议在开发调优时打开，最终部署上线时关闭。</p>
+<h4 id="慢sql日志设置">慢SQL日志设置</h4>
+<p>通过SQL来查看记录慢SQL日志是否开启：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">查看变量</span> <span class="n">slow_query_log</span><span class="err">，记录慢查询日志默认关闭</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%s</span><span class="s1">low_query_log%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span>       <span class="o">|</span> <span class="n">Value</span>                                        <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">slow_query_log</span>      <span class="o">|</span> <span class="n">OFF</span>                                          <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">slow_query_log_file</span> <span class="o">|</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">mysql</span><span class="o">/</span><span class="n">data</span><span class="o">/</span><span class="n">MacBook</span><span class="o">-</span><span class="n">Pro</span><span class="o">-</span><span class="mi">2</span><span class="o">-</span><span class="n">slow</span><span class="o">.</span><span class="n">log</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span></code></pre></div><p>可以通过SQL来进行开启记录慢SQL日志：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">在内存中开启慢</span><span class="n">SQL记录日志</span><span class="err">；</span> <span class="err">此种方式在</span> <span class="n">mysql</span> <span class="err">服务重启后失效</span>
+</span></span><span class="line"><span class="cl"> <span class="n">set</span> <span class="n">global</span> <span class="n">slow_query_log</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">查看是否开启慢</span><span class="n">SQL日志记录</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%s</span><span class="s1">low_query_log%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span>       <span class="o">|</span> <span class="n">Value</span>                                        <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">slow_query_log</span>      <span class="o">|</span> <span class="n">ON</span>                                           <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">slow_query_log_file</span> <span class="o">|</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">mysql</span><span class="o">/</span><span class="n">data</span><span class="o">/</span><span class="n">MacBook</span><span class="o">-</span><span class="n">Pro</span><span class="o">-</span><span class="mi">2</span><span class="o">-</span><span class="n">slow</span><span class="o">.</span><span class="n">log</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 在MySQL my.cnf 配置文件中追加配置;重启MySQL服务后也生效，即永久开启
+</span></span><span class="line"><span class="cl"> slow_query_log=1
+</span></span><span class="line"><span class="cl"> slow_query_log_file=/usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span></code></pre></div><p>查看慢SQL记录日志阈值：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">查看慢</span><span class="n">SQL记录日志阈值</span><span class="err">，默认</span><span class="mi">10</span><span class="err">秒</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%lo</span><span class="s1">ng_query_time%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span>   <span class="o">|</span> <span class="n">Value</span>     <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">long_query_time</span> <span class="o">|</span> <span class="mf">10.000000</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span></code></pre></div><p>修改慢SQL记录日志阈值：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">在内存中修改设置慢查询</span><span class="n">SQL记录日志阈值为5秒</span><span class="err">；注意设置后不会立即生效，需要重新登陆</span><span class="n">mysql客户端才会生效</span>
+</span></span><span class="line"><span class="cl"> <span class="n">set</span> <span class="n">global</span> <span class="n">long_query_time</span> <span class="o">=</span> <span class="mi">5</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">设置之后重新登陆</span><span class="n">mysql使用命令查看慢SQL查询日志阈值</span> 
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%lo</span><span class="s1">ng_query_time%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span>   <span class="o">|</span> <span class="n">Value</span>     <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">long_query_time</span> <span class="o">|</span> <span class="mf">5.000000</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+-----------------+-----------+</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 在MySQL配置文件my.cnf中修改慢查询SQL记录日志阈值,设置为3秒
+</span></span><span class="line"><span class="cl"> long_query_time=3
+</span></span></code></pre></div><h4 id="查看慢sql日志">查看慢SQL日志</h4>
+<ul>
+<li>直接查看慢SQL日志；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl">  <span class="o">--</span> <span class="err">模拟慢查询</span><span class="n">SQL</span> 
+</span></span><span class="line"><span class="cl">  <span class="n">select</span> <span class="n">sleep</span><span class="p">(</span><span class="mi">5</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">  <span class="o">--</span> <span class="err">查看是否开启慢</span><span class="n">SQL日志记录</span>
+</span></span><span class="line"><span class="cl">  <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%s</span><span class="s1">low_query_log%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">  <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl">  <span class="o">|</span> <span class="n">Variable_name</span>       <span class="o">|</span> <span class="n">Value</span>                                        <span class="o">|</span>
+</span></span><span class="line"><span class="cl">  <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span><span class="line"><span class="cl">  <span class="o">|</span> <span class="n">slow_query_log</span>      <span class="o">|</span> <span class="n">ON</span>                                           <span class="o">|</span>
+</span></span><span class="line"><span class="cl">  <span class="o">|</span> <span class="n">slow_query_log_file</span> <span class="o">|</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">mysql</span><span class="o">/</span><span class="n">data</span><span class="o">/</span><span class="n">MacBook</span><span class="o">-</span><span class="n">Pro</span><span class="o">-</span><span class="mi">2</span><span class="o">-</span><span class="n">slow</span><span class="o">.</span><span class="n">log</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl">  <span class="o">+---------------------+----------------------------------------------+</span>
+</span></span></code></pre></div>查看慢SQL日志记录<code>cat /usr/local/mysql/data/MacBook-Pro-2-slow.log</code>执行命令：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> MacBook-Pro-2:~ root# cat /usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span><span class="line"><span class="cl"> /usr/local/mysql/bin/mysqld, Version: 8.0.22 (MySQL Community Server - GPL). started with:
+</span></span><span class="line"><span class="cl"> Tcp port: 3306  Unix socket: /tmp/mysql.sock
+</span></span><span class="line"><span class="cl"> Time                 Id Command    Argument
+</span></span><span class="line"><span class="cl"> # Time: 2021-09-17T06:46:20.655775Z
+</span></span><span class="line"><span class="cl"> # User@Host: root[root] @ localhost []  Id:    15
+</span></span><span class="line"><span class="cl"> # Query_time: 4.003891  Lock_time: 0.000000 Rows_sent: 1  Rows_examined: 1
+</span></span><span class="line"><span class="cl"> use sql_demo;
+</span></span><span class="line"><span class="cl"> SET timestamp=1631861176;
+</span></span><span class="line"><span class="cl"> select sleep(4);
+</span></span></code></pre></div></li>
+<li>通过<code>mysqldumpslow</code>工具来查看,可以通过一些过滤条件快速找到需要定位的慢SQL；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> 语法：mysqldumpslow 各种参数 慢查询日志文件路径
+</span></span><span class="line"><span class="cl"> -s：排序方式
+</span></span><span class="line"><span class="cl"> -r：逆序反转
+</span></span><span class="line"><span class="cl"> -l：锁定时间，不要从总时间中减去锁定时间
+</span></span><span class="line"><span class="cl"> -g：在文件中查找考虑包含此字符串的
+</span></span><span class="line"><span class="cl"> 更多指令解析查看 mysqldumpslow --help
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 获取返回记录最多的3条SQL
+</span></span><span class="line"><span class="cl"> mysqldumpslow -s r -t 3 /usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 获取访问次数最多的3条SQL
+</span></span><span class="line"><span class="cl"> mysqldumpslow -s r -t 3 /usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 按照时间排序，前10条包含 left join 的查询SQL 
+</span></span><span class="line"><span class="cl"> mysqldumpslow -s t -t 10 -g &#34;left join&#34; /usr/local/mysql/data/MacBook-Pro-2-slow.log
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="模拟数据并分析sql">模拟数据并分析SQL</h4>
+<ul>
+<li>
+<p>模拟数据；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">创建表</span>
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">database</span> <span class="n">testdata</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="n">use</span> <span class="n">testdata</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">dept</span> 
+</span></span><span class="line"><span class="cl"> <span class="p">(</span>
+</span></span><span class="line"><span class="cl"> <span class="n">dno</span> <span class="ne">int</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="n">primary</span> <span class="n">key</span> <span class="n">default</span> <span class="mi">0</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">dname</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">loc</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">30</span><span class="p">)</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span>
+</span></span><span class="line"><span class="cl"> <span class="p">)</span> <span class="n">engine</span><span class="o">=</span><span class="n">innodb</span> <span class="n">default</span> <span class="n">charset</span><span class="o">=</span><span class="n">utf8</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">emp</span>
+</span></span><span class="line"><span class="cl"> <span class="p">(</span>
+</span></span><span class="line"><span class="cl"> <span class="n">eid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="n">primary</span> <span class="n">key</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">ename</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">job</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl"> <span class="n">deptno</span> <span class="ne">int</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">default</span> <span class="mi">0</span>
+</span></span><span class="line"><span class="cl"> <span class="p">)</span><span class="n">engine</span><span class="o">=</span><span class="n">innodb</span> <span class="n">default</span> <span class="n">charset</span><span class="o">=</span><span class="n">utf8</span><span class="p">;</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">创建存储过程：获取随机字符串</span>
+</span></span><span class="line"><span class="cl"> <span class="n">set</span> <span class="n">global</span> <span class="n">log_bin_trust_function_creators</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="n">use</span> <span class="n">testdata</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="n">delimiter</span> <span class="o">$</span>
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">function</span> <span class="n">randstring</span><span class="p">(</span><span class="n">n</span> <span class="ne">int</span><span class="p">)</span> <span class="n">returns</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">255</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl"> <span class="n">begin</span> 
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">     <span class="n">declare</span> <span class="n">all_str</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">100</span><span class="p">)</span> <span class="n">default</span> <span class="s1">&#39;abcdefghijklmnopqrestuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">declare</span> <span class="n">return_str</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">255</span><span class="p">)</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">declare</span> <span class="n">i</span> <span class="ne">int</span> <span class="n">default</span> <span class="mi">0</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="k">while</span> <span class="n">i</span><span class="o">&lt;</span><span class="n">n</span>
+</span></span><span class="line"><span class="cl">     <span class="k">do</span>
+</span></span><span class="line"><span class="cl">         <span class="n">set</span> <span class="n">return_str</span><span class="o">=</span><span class="n">concat</span><span class="p">(</span><span class="n">return_str</span><span class="p">,</span> <span class="n">substring</span><span class="p">(</span><span class="n">all_str</span><span class="p">,</span> <span class="n">FLOOR</span><span class="p">(</span><span class="mi">1</span><span class="o">+</span><span class="n">rand</span><span class="p">()</span><span class="o">*</span><span class="mi">52</span><span class="p">),</span> <span class="mi">1</span><span class="p">));</span>
+</span></span><span class="line"><span class="cl">         <span class="n">set</span> <span class="n">i</span><span class="o">=</span><span class="n">i</span><span class="o">+</span><span class="mi">1</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">end</span> <span class="k">while</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="k">return</span> <span class="n">return_str</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="n">end</span> <span class="o">$</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 创建存储函数：插入随机整数
+</span></span><span class="line"><span class="cl"> use testdata;
+</span></span><span class="line"><span class="cl"> create function ran_num() returns int(5)
+</span></span><span class="line"><span class="cl"> begin 
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> declare i int default 0;
+</span></span><span class="line"><span class="cl"> set i=floor(rand()*100);
+</span></span><span class="line"><span class="cl"> return i;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> end$
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 创建存储过程：向emp表插入数据
+</span></span><span class="line"><span class="cl"> create procedure insert_emp(in eid_start int(10), in data_times int(10))
+</span></span><span class="line"><span class="cl"> begin 
+</span></span><span class="line"><span class="cl"> declare i int default 0;
+</span></span><span class="line"><span class="cl"> set autocommit =0;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> repeat 
+</span></span><span class="line"><span class="cl"> insert into emp values(eid_start+i, randstring(5), &#39;other&#39;, ran_num());
+</span></span><span class="line"><span class="cl"> set i=i+1;
+</span></span><span class="line"><span class="cl"> until i=data_times
+</span></span><span class="line"><span class="cl"> end repeat;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> commit;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> end $
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 创建存储过程：向dept表插入数据
+</span></span><span class="line"><span class="cl"> create procedure insert_dept(in dno_start int(10), in data_times int(10))
+</span></span><span class="line"><span class="cl"> begin 
+</span></span><span class="line"><span class="cl"> declare i int default 0;
+</span></span><span class="line"><span class="cl"> set autocommit =0;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> repeat 
+</span></span><span class="line"><span class="cl"> insert into dept values(dno_start+i, randstring(6), randstring(8));
+</span></span><span class="line"><span class="cl"> set i=i+1;
+</span></span><span class="line"><span class="cl"> until i=data_times
+</span></span><span class="line"><span class="cl"> end repeat;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> commit;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> end $
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 向emp、dept表中插入数据
+</span></span><span class="line"><span class="cl"> delimiter ;
+</span></span><span class="line"><span class="cl"> call insert_emp(1000, 800000);
+</span></span><span class="line"><span class="cl"> call insert_dept(10, 30);
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 验证插入数据量
+</span></span><span class="line"><span class="cl"> select count(1) from emp;
+</span></span></code></pre></div></li>
+<li>
+<p>使用<code>show profile</code>进行sql分析；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">查看</span> <span class="n">profiling</span> <span class="err">是否开启，默认是关闭的</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;profiling&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------+-------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Variable_name</span> <span class="o">|</span> <span class="n">Value</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------+-------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">profiling</span>     <span class="o">|</span> <span class="n">OFF</span>   <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+---------------+-------+</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">如果没开启将其开启</span>
+</span></span><span class="line"><span class="cl"> <span class="n">set</span> <span class="n">profiling</span><span class="o">=</span><span class="n">on</span><span class="p">;</span>
+</span></span></code></pre></div></li>
+<li>
+<p>执行测试SQL，任意执行均可供之后SQL分析；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">select * from emp;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">select * from emp group by eid order by eid;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">select * from emp group by eid limit 150000;
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="o">--</span> <span class="err">执行命令，查看结果</span>
+</span></span><span class="line"><span class="cl"> <span class="n">show</span> <span class="n">profiles</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----------+------------+--------------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">Query_ID</span> <span class="o">|</span> <span class="n">Duration</span>   <span class="o">|</span> <span class="n">Query</span>                                            <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----------+------------+--------------------------------------------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">2</span> <span class="o">|</span> <span class="mf">0.00300900</span> <span class="o">|</span> <span class="n">show</span> <span class="n">tables</span>                                      <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">3</span> <span class="o">|</span> <span class="mf">0.01485700</span> <span class="o">|</span> <span class="n">desc</span> <span class="n">emp</span>                                         <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">4</span> <span class="o">|</span> <span class="mf">0.00191200</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">10</span> <span class="n">limit</span> <span class="mi">150000</span>   <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">5</span> <span class="o">|</span> <span class="mf">0.25516300</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span>                                <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">6</span> <span class="o">|</span> <span class="mf">0.00026400</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">10</span> <span class="n">limit</span> <span class="mi">150000</span>   <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">7</span> <span class="o">|</span> <span class="mf">0.00019600</span> <span class="o">|</span> <span class="n">select</span> <span class="n">eid</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">10</span> <span class="n">limit</span> <span class="mi">150000</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">8</span> <span class="o">|</span> <span class="mf">0.03907500</span> <span class="o">|</span> <span class="n">select</span> <span class="n">eid</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">limit</span> <span class="mi">150000</span>    <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>        <span class="mi">9</span> <span class="o">|</span> <span class="mf">0.06499100</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">limit</span> <span class="mi">150000</span>      <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">10</span> <span class="o">|</span> <span class="mf">0.00031500</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">20</span> <span class="n">order</span> <span class="n">by</span> <span class="mi">5</span>     <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">11</span> <span class="o">|</span> <span class="mf">0.00009100</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span><span class="o">%</span><span class="mi">20</span> <span class="n">order</span> <span class="n">by</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">12</span> <span class="o">|</span> <span class="mf">0.00012400</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">order</span> <span class="n">by</span>          <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">13</span> <span class="o">|</span> <span class="mf">0.25195300</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">order</span> <span class="n">by</span> <span class="n">eid</span>      <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">14</span> <span class="o">|</span> <span class="mf">0.00196200</span> <span class="o">|</span> <span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;profiling&#39;</span>                  <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>       <span class="mi">15</span> <span class="o">|</span> <span class="mf">0.26208900</span> <span class="o">|</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">emp</span> <span class="n">group</span> <span class="n">by</span> <span class="n">eid</span> <span class="n">order</span> <span class="n">by</span> <span class="n">eid</span>      <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----------+------------+--------------------------------------------------+</span>
+</span></span></code></pre></div></li>
+<li>
+<p>使用命令<code>show profile cpu,block io for query 上一步前面执行 show profiles 的 Query_ID ;</code>诊断SQL；</p>
+<blockquote>
+<p>参数备注，不区分大小写:
+all：显示所有的开销信息;
+block io：显示块lO相关开销;
+context switches：上下文切换相关开销;
+cpu：显示CPU相关开销信息;
+ipc：显示发送和接收相关开销信息;
+memory：显示内存相关开销信息;
+page faults：显示页面错误相关开销信息;
+source：显示和Source_function，Source_file，Source_line相关的开销信息;
+swaps：显示交换次数相关开销的信息;</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> show profile cpu,block io for query 3;
+</span></span><span class="line"><span class="cl"> +----------------------------+----------+----------+------------+--------------+---------------+
+</span></span><span class="line"><span class="cl"> | Status                     | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |
+</span></span><span class="line"><span class="cl"> +----------------------------+----------+----------+------------+--------------+---------------+
+</span></span><span class="line"><span class="cl"> | starting                   | 0.004292 | 0.000268 |   0.000941 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000026 | 0.000012 |   0.000013 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000007 | 0.000005 |   0.000003 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | Opening tables             | 0.003883 | 0.000865 |   0.000880 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | init                       | 0.000022 | 0.000013 |   0.000008 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | System lock                | 0.000013 | 0.000012 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | optimizing                 | 0.000994 | 0.000078 |   0.000155 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | statistics                 | 0.000233 | 0.000222 |   0.000011 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | preparing                  | 0.000046 | 0.000043 |   0.000003 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | Creating tmp table         | 0.000075 | 0.000073 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | executing                  | 0.001532 | 0.000141 |   0.000266 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000050 | 0.000044 |   0.000005 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000014 | 0.000012 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.001539 | 0.000102 |   0.000356 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000044 | 0.000037 |   0.000007 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.000019 | 0.000016 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | checking permissions       | 0.001250 | 0.000089 |   0.000318 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | end                        | 0.000015 | 0.000007 |   0.000008 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | query end                  | 0.000006 | 0.000004 |   0.000001 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | waiting for handler commit | 0.000041 | 0.000040 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | removing tmp table         | 0.000012 | 0.000010 |   0.000001 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | waiting for handler commit | 0.000010 | 0.000009 |   0.000002 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | closing tables             | 0.000019 | 0.000018 |   0.000001 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | freeing items              | 0.000648 | 0.000081 |   0.000152 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> | cleaning up                | 0.000067 | 0.000047 |   0.000021 |            0 |             0 |
+</span></span><span class="line"><span class="cl"> +----------------------------+----------+----------+------------+--------------+---------------+
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="全局查询日志">全局查询日志</h4>
+<p><strong>不要在生产环境开启这个功能。</strong></p>
+<p>在配置MySQL文件<code>my.cnf</code>设置全局查询日志：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="o">--</span> <span class="err">开启全局查询日志</span>
+</span></span><span class="line"><span class="cl"><span class="n">general_log</span><span class="o">=</span><span class="mi">1</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">记录日志文件的路径</span>
+</span></span><span class="line"><span class="cl"><span class="n">general_log_file</span><span class="o">=/</span><span class="n">path</span><span class="o">/</span><span class="n">logfile</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">设置输出格式为</span> <span class="n">FILE</span>
+</span></span><span class="line"><span class="cl"><span class="n">log_output</span><span class="o">=</span><span class="n">FILE</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">通过</span><span class="n">cat命令直接查看</span><span class="err">；如果为空则需要造数</span>
+</span></span><span class="line"><span class="cl"><span class="n">cat</span> <span class="o">/</span><span class="k">var</span><span class="o">/</span><span class="n">lib</span><span class="o">/</span><span class="n">mysql</span><span class="o">/</span><span class="n">bigdata01</span><span class="o">.</span><span class="n">log</span><span class="p">;</span>
+</span></span></code></pre></div><p>在mysql客户端设置全局查询日志：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="o">--</span> <span class="err">查看是否开启全局查询日志</span>
+</span></span><span class="line"><span class="cl"><span class="n">show</span> <span class="n">variables</span> <span class="n">like</span> <span class="s1">&#39;</span><span class="si">%g</span><span class="s1">eneral_log%&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">开启全局查询日志</span>
+</span></span><span class="line"><span class="cl"><span class="n">set</span> <span class="n">global</span> <span class="n">general_log</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">设置输出格式为</span> <span class="n">TABLE</span>
+</span></span><span class="line"><span class="cl"><span class="n">set</span> <span class="n">global</span> <span class="n">log_output</span><span class="o">=</span><span class="s1">&#39;TABLE&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="o">--</span> <span class="err">可在</span><span class="n">mysql库里的geneial_log表查看</span><span class="err">；如果为空则需要造数</span>
+</span></span><span class="line"><span class="cl"><span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">mysql</span><span class="o">.</span><span class="n">general_log</span><span class="p">;</span>
+</span></span></code></pre></div><h3 id="sql优化方法">SQL优化方法</h3>
+<p>对于后端程序员来说，想让SQL执行的更快，最主要的就是软件层面优化索引和分库分表。</p>
+<h4 id="exist和in选择">exist和in选择</h4>
+<p>两者可以互相替代，如果主查询的数据集大，使用in的效率高一点；如果子查询的数据集大，使用exist效率高一点；</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 假设此处主查询数据集较大，使用in
+</span></span><span class="line"><span class="cl"> select * from tbl_001 where tid in (select id from tbl_001);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">  -- 假设此处子查询数据集较大，使用exist
+</span></span><span class="line"><span class="cl">  select tid from tbl_001 where exists (select * from tbl_001);
+</span></span></code></pre></div><blockquote>
+<p>exists语法：将主查询的结果，放到子查询结果中进行判断，看子查询中是否有数据，如果有数据则保留数据并返回；没有则返回空。</p>
+</blockquote>
+<h4 id="order-by优化">order by优化</h4>
+<p>order by 是比较常用的一个关键字，基本上查询出来的数据都要进行排序，否则就太乱了。使用order by的时候常常伴随着Using filesort的发生，Using filesort在底层有两种算法，根据IO的次数分为：</p>
+<ul>
+<li>双路排序：MySQL4.1之前默认使用双路排序；具体执行流程，双路排序需要扫描两次磁盘上的字段，首先扫描排序的字段对字段进行排序，然后扫描其他字段；</li>
+<li>单路排序：为了减少IO访问次数在MySQL4.1之后默认使用单路排序；读取一次获取全部的字段，在buffer中进行排序。但是此种方法存在隐患不一定是只读一次数据，如果数据量过大buffer放不下则再需要读取文件，可以通过调节buffer来进行缓解；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 设置读取文件缓冲区（buffer）的大小,单位字节
+</span></span><span class="line"><span class="cl"> set max_length_for_sort_data = 1024;
+</span></span></code></pre></div></li>
+</ul>
+<p>如果需要排序的列的总大小超过了设置的<code>max_length_for_sort_data</code>那么MySQL底层会自动从单路排序切换到双路排序。</p>
+<p>保证全部索引排序字段的一致性，都是升序或都是降序，不要部分升序部分降序。</p>
+<h3 id="sql优化案例">SQL优化案例</h3>
+<h4 id="单表优化">单表优化</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">准备测试表、测试数据</span>
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">book_2021</span><span class="p">(</span>
+</span></span><span class="line"><span class="cl">   <span class="n">bid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="n">primary</span> <span class="n">key</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">name</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">authorid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">publicid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">typeid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span>  
+</span></span><span class="line"><span class="cl"> <span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="s1">&#39;java&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="s1">&#39;php&#39;</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s1">&#39;c&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="s1">&#39;c#&#39;</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">book_2021</span> <span class="n">values</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span><span class="s1">&#39;c++&#39;</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span></code></pre></div><p>需要优化的SQL：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- SQL原型，优化该SQL 
+</span></span><span class="line"><span class="cl"> select bid from book_2021 where typeid in(2,3) and authorid=1 order by typeid desc;
+</span></span></code></pre></div><p>执行计划分析该SQL,发现该SQL存在<code>Using filesort</code>,type为ALL，需要进行SQL优化。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select bid from book_2021 where typeid in(2,3) and authorid=1 order by typeid desc;
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------+---------------+------+---------+------+------+-----------------------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table     | type | possible_keys | key  | key_len | ref  | rows | Extra                       |
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------+---------------+------+---------+------+------+-----------------------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | book_2021 | ALL  | NULL          | NULL | NULL    | NULL |    5 | Using where; Using filesort |
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------+---------------+------+---------+------+------+-----------------------------+
+</span></span></code></pre></div><ol>
+<li>根据SQL的执行过程可知,建立索引的顺序为<code>typeid、authorid、bid</code>；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- sql执行顺序
+</span></span><span class="line"><span class="cl"> from .. on .. join ..  where .. group by .. having .. select distinct .. order by .. limit ..
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 建立索引
+</span></span><span class="line"><span class="cl"> alter table book_2021 add index idx_tab(typeid,authorid,bid);
+</span></span></code></pre></div></li>
+<li>使用in的时候使索引失效，如果in失效那么后面的索引也将会失效，所以将范围条件放到最后；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 优化后的SQL
+</span></span><span class="line"><span class="cl"> select bid from book_2021 where authorid=1 and typeid in(2,3) order by typeid desc;
+</span></span></code></pre></div>将旧索引删除，创建字段顺序对应的索引。
+<blockquote>
+<p>温馨提示：索引一旦升级优化，需要删除索引防止干扰</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 删除 idx_tab 索引
+</span></span><span class="line"><span class="cl"> drop index idx_tab on book_2021;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 给表 book_2021 添加索引 idx_atb
+</span></span><span class="line"><span class="cl"> alter table book_2021 add index idx_atb(authorid,typeid,bid);
+</span></span></code></pre></div></li>
+</ol>
+<p>最终优化后的SQL执行过程：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select bid from book_2021 where authorid=1 and typeid in(2,3) order by typeid desc;
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------------+-------+---------------+---------+---------+------+------+----------+-----------------------------------------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table     | partitions | type  | possible_keys | key     | key_len | ref  | rows | filtered | Extra                                         |
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------------+-------+---------------+---------+---------+------+------+----------+-----------------------------------------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | book_2021 | NULL       | range | idx_atb       | idx_atb | 8       | NULL |    3 |   100.00 | Using where; Backward index scan; Using index |
+</span></span><span class="line"><span class="cl"> +----+-------------+-----------+------------+-------+---------------+---------+---------+------+------+----------+-----------------------------------------------+
+</span></span></code></pre></div><p>单表优化总结：</p>
+<ul>
+<li>最佳左前缀原则，保持索引的定义和使用顺序一致；</li>
+<li>索引需要逐步优化；</li>
+<li>将包含范围查询的条件放置到最后；</li>
+</ul>
+<h4 id="两表优化">两表优化</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">准备测试表、测试数据</span>
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">teacher2</span><span class="p">(</span>
+</span></span><span class="line"><span class="cl">   <span class="n">tid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="n">primary</span> <span class="n">key</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">cid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span>  
+</span></span><span class="line"><span class="cl"> <span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">teacher2</span> <span class="n">values</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">teacher2</span> <span class="n">values</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">teacher2</span> <span class="n">values</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">course2</span><span class="p">(</span>
+</span></span><span class="line"><span class="cl">   <span class="n">cid</span> <span class="ne">int</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="ow">not</span> <span class="n">null</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">   <span class="n">cname</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span>
+</span></span><span class="line"><span class="cl"> <span class="p">);</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">course2</span> <span class="n">values</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="s1">&#39;java&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">course2</span> <span class="n">values</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="s1">&#39;phython&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">course2</span> <span class="n">values</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="s1">&#39;kotlin&#39;</span><span class="p">);</span>
+</span></span></code></pre></div><p>需要优化的SQL：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- SQL原型，优化该SQL 
+</span></span><span class="line"><span class="cl"> select * from teacher2 t left outer join course2 c on t.cid = c.cid where c.cname = &#39;java&#39;;
+</span></span></code></pre></div><p>执行过程分析该SQL，发现进行了全表扫描。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> explain select * from teacher2 t left outer join course2 c on t.cid = c.cid where c.cname = &#39;java&#39;;
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+--------------------------------------------+
+</span></span><span class="line"><span class="cl"> | id | select_type | table | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra                                      |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+--------------------------------------------+
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | c     | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    3 |    33.33 | Using where                                |
+</span></span><span class="line"><span class="cl"> |  1 | SIMPLE      | t     | NULL       | ALL  | NULL          | NULL | NULL    | NULL |    3 |    33.33 | Using where; Using join buffer (hash join) |
+</span></span><span class="line"><span class="cl"> +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+--------------------------------------------+
+</span></span></code></pre></div><p>优化思路为建立索引，在哪张表哪个字段建立索引？即<strong>小表驱动大表</strong>，索引应建立在经常使用的字段上，假设此时teacher表数据量少，那么应为<code>t.cid、c.name</code>字段加索引。</p>
+<p>什么是小表驱动大表？
+假设小表10条数据；大表300条数据；让大小表做嵌套循环，无论10是外层循环还是300是外层循环，结果都是3000次，但是为了减少表连接创建的次数，应该将10，即小表放在外层循环这样效率会更高。</p>
+<p>为什么这么做？
+现有两个表A与B ，表A有200条数据，表B有20万条数据。按照循环的概念举个例子：</p>
+<ul>
+<li>小表驱动大表：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(200条){
+</span></span><span class="line"><span class="cl">for(20万条){
+</span></span><span class="line"><span class="cl">...
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>大表驱动小表：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(20万条){
+</span></span><span class="line"><span class="cl">for(200条){
+</span></span><span class="line"><span class="cl">...
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+</ul>
+<p>如果小的循环在外层，对于表连接来说就只连接200次，如果大的循环在外层，则需要进行20万次表连接，从而浪费资源，增加消耗。
+小表驱动大表的主要目的是通过减少表连接创建的次数，加快查询速度。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 给表teacher2、course2 添加索引
+</span></span><span class="line"><span class="cl"> alter table teacher2 add index idx_teacher2_cid(cid);
+</span></span><span class="line"><span class="cl"> alter table course2 add index idx_course2_cname(cname);
+</span></span></code></pre></div><p>最终优化后的SQL：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="o">--</span> <span class="err">添加索引后</span>
+</span></span><span class="line"><span class="cl"> <span class="n">explain</span> <span class="n">select</span> <span class="o">*</span> <span class="n">from</span> <span class="n">teacher2</span> <span class="n">t</span> <span class="n">left</span> <span class="n">outer</span> <span class="n">join</span> <span class="n">course2</span> <span class="n">c</span> <span class="n">on</span> <span class="n">t</span><span class="o">.</span><span class="n">cid</span> <span class="o">=</span> <span class="n">c</span><span class="o">.</span><span class="n">cid</span> <span class="n">where</span> <span class="n">c</span><span class="o">.</span><span class="n">cname</span> <span class="o">=</span> <span class="s1">&#39;java&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+------------+------+-------------------+-------------------+---------+----------------+------+----------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span> <span class="n">id</span> <span class="o">|</span> <span class="n">select_type</span> <span class="o">|</span> <span class="n">table</span> <span class="o">|</span> <span class="n">partitions</span> <span class="o">|</span> <span class="n">type</span> <span class="o">|</span> <span class="n">possible_keys</span>     <span class="o">|</span> <span class="n">key</span>               <span class="o">|</span> <span class="n">key_len</span> <span class="o">|</span> <span class="n">ref</span>            <span class="o">|</span> <span class="n">rows</span> <span class="o">|</span> <span class="n">filtered</span> <span class="o">|</span> <span class="n">Extra</span>       <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+------------+------+-------------------+-------------------+---------+----------------+------+----------+-------------+</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">c</span>     <span class="o">|</span> <span class="n">NULL</span>       <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_course2_cname</span> <span class="o">|</span> <span class="n">idx_course2_cname</span> <span class="o">|</span> <span class="mi">83</span>      <span class="o">|</span> <span class="k">const</span>          <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span>   <span class="mf">100.00</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">where</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">|</span>  <span class="mi">1</span> <span class="o">|</span> <span class="n">SIMPLE</span>      <span class="o">|</span> <span class="n">t</span>     <span class="o">|</span> <span class="n">NULL</span>       <span class="o">|</span> <span class="n">ref</span>  <span class="o">|</span> <span class="n">idx_teacher2_cid</span>  <span class="o">|</span> <span class="n">idx_teacher2_cid</span>  <span class="o">|</span> <span class="mi">4</span>       <span class="o">|</span> <span class="n">sql_demo</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">cid</span> <span class="o">|</span>    <span class="mi">1</span> <span class="o">|</span>   <span class="mf">100.00</span> <span class="o">|</span> <span class="n">Using</span> <span class="n">index</span> <span class="o">|</span>
+</span></span><span class="line"><span class="cl"> <span class="o">+----+-------------+-------+------------+------+-------------------+-------------------+---------+----------------+------+----------+-------------+</span>
+</span></span></code></pre></div><p>多表优化总结：</p>
+<ul>
+<li>小表驱动大表；</li>
+<li>索引建立在经常查询的字段上；</li>
+</ul>
+<h2 id="mysql锁机制">MySQL锁机制</h2>
+<p>在数据库中，除传统的计算资源（如CPU、RAM、I/O等）的争用以外，数据也是一种供许多用户共享的资源。如何保证数据并发访问的一致性、有效性是所有数据库必须解决的一个问题，锁冲突也是影响数据库并发访问性能的一个重要因素。从这个角度来说，锁对数据库而言显得尤其重要，也更加复杂。
+简而言之，锁机制是解决因资源共享，而造成的并发问题。</p>
+<p>MySQL中的锁按照对数据操作的类型分为：读锁即共享锁，写锁即互斥锁；按照操作粒度来分，分为表锁、行锁，页锁。</p>
+<ul>
+<li>读锁：对于同一个数据，多个读操作可以同时进行，互不干扰。</li>
+<li>写锁：如果当前写操作没有完毕，则无法进行其他的读操作、写操作。</li>
+<li>表锁：一次性对一张表整体加锁。MyISAM存储引擎偏向表锁，开销较小、加锁较快、无死锁、锁的范围较大，但是容易发生发生锁冲突，并发度低。</li>
+<li>行锁：一次性对一条数据加锁。InnoDB存储引擎偏向行锁，开销较大、加锁较慢、容易出现死锁、锁的范围较小，但是不易发生锁冲突，并发度高。</li>
+</ul>
+<h3 id="表锁">表锁</h3>
+<p>测试数据：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"> <span class="n">create</span> <span class="n">table</span> <span class="n">mylock</span> <span class="p">(</span>
+</span></span><span class="line"><span class="cl">     <span class="n">id</span> <span class="ne">int</span> <span class="ow">not</span> <span class="n">null</span> <span class="n">primary</span> <span class="n">key</span> <span class="n">auto_increment</span><span class="p">,</span>
+</span></span><span class="line"><span class="cl">     <span class="n">name</span> <span class="n">varchar</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span> <span class="n">default</span> <span class="s1">&#39;&#39;</span>
+</span></span><span class="line"><span class="cl"> <span class="p">)</span> <span class="n">engine</span> <span class="n">myisam</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;a&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;b&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;c&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;d&#39;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl"> <span class="n">insert</span> <span class="n">into</span> <span class="n">mylock</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="n">values</span><span class="p">(</span><span class="s1">&#39;e&#39;</span><span class="p">);</span>
+</span></span></code></pre></div><p>常用命令：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 加锁
+</span></span><span class="line"><span class="cl"> lock table 表名1 read/write, 表名2 read/write, 其他;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> -- 解锁
+</span></span><span class="line"><span class="cl"> unlock tables;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"> -- 查看表上是否加锁；在In_use列，0代表没有加锁，1代表加锁
+</span></span><span class="line"><span class="cl"> show open tables;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> -- 分析表锁
+</span></span><span class="line"><span class="cl"> -- Table_locks_immediate：产生表级锁定的次数，表示可以立即获取锁的查询次数，每立即获取锁值加1
+</span></span><span class="line"><span class="cl"> -- Table_locks_waited：出现表级锁定争用而发生等待的次数(不能立即获取锁的次数，每等待一次锁值加1)，此值高则说明存在着较严重的表级锁争用情况
+</span></span><span class="line"><span class="cl"> show status like &#39;table_locks%&#39;;
+</span></span></code></pre></div><hr>
+<p>给表添加<strong>读锁</strong>及测试读操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-002" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-002.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-004" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-004.png"></p>
+<p>给表添加<strong>读锁</strong>及测试写操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-003" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-003.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-005" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-005.png"></p>
+<p>给某个表添加读锁之后，所有会话都能对这个表进行读操作，但是当前会话不能对该表进行写操作，对其他表进行读、写操作；其他会话能需要等持有锁的会话释放该表的锁后，才能进行写操作，期间将会一直处于等待状态，可以对其他表进行读写操作。</p>
+<hr>
+<p>给表添加<strong>写锁</strong>及测试读操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-006" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-006.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-007" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-007.png"></p>
+<p>给表添加<strong>写锁</strong>及测试写操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-008" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-008.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-009" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-009.png"></p>
+<p>给某个表添加写锁之后，当前会话可以对该表进行写操作、读操作，其他会话要想对该表进行读写操作需要等持有锁的会话释放锁，否则期间将会一直等待该锁释放；但是当前持有锁的会话是不能对其他表进行读写操作，其他会话能够对其他表进行读写操作。</p>
+<p>对于表锁MyISAM在执行查询语句前，会自动给涉及的所有表加读锁，在执行增删改操作前，会自动给涉及的表加写锁。</p>
+<ul>
+<li>对MyISAM表的读操作(加读锁)，不会阻塞其他进程对同一表的读请求，但会阻塞对同一表的写请求。只有当读锁释放后，才会执行其它进程的写操作。</li>
+<li>对MyISAM表的写操作(加写锁)，会阻塞其他进程对同一表的读和写操作，只有当写锁释放后，才会执行其它进程的读写操作。</li>
+</ul>
+<p>简而言之，就是读锁会阻塞写，但是不会堵塞读。而写锁则会把读和写都堵塞。</p>
+<h3 id="行锁">行锁</h3>
+<p>测试数据：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> CREATE TABLE test_innodb_lock (a INT(11),b VARCHAR(16))ENGINE=INNODB;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(1,&#39;b2&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(3,&#39;3&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(4, &#39;4000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(5,&#39;5000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(6, &#39;6000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(7,&#39;7000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(8, &#39;8000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(9,&#39;9000&#39;);
+</span></span><span class="line"><span class="cl"> INSERT INTO test_innodb_lock VALUES(1,&#39;b1&#39;);
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl"> CREATE INDEX test_innodb_a_ind ON test_innodb_lock(a);
+</span></span><span class="line"><span class="cl"> CREATE INDEX test_innodb_lock_b_ind ON test_innodb_lock(b);
+</span></span><span class="line"><span class="cl"> 
+</span></span></code></pre></div><p>常用命令：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 分析行锁定：
+</span></span><span class="line"><span class="cl"> -- 尤其是当等待次数很高，而且每次等待时长也不小的时候，我们就需要分析系统中为什么会有如此多的等待，然后根据分析结果着手指定优化计划。
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_current_waits：当前正在等待锁定的数量；
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_time：从系统启动到现在锁定总时间长度；
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_time_avg：每次等待所花平均时间；
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_time_max：从系统启动到现在等待最常的一次所花的时间；
+</span></span><span class="line"><span class="cl"> -- Innodb_row_lock_waits：系统启动后到现在总共等待的次数；
+</span></span><span class="line"><span class="cl"> -- show status like &#39;innodb_row_lock%&#39;;
+</span></span></code></pre></div><p>由于行锁与事务相关，所以在测试之前需要关闭MySQL的自动提交：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> -- 关闭自动提交；0关闭，1打开
+</span></span><span class="line"><span class="cl"> set autocommit = 0;
+</span></span></code></pre></div><p>测试行锁读写操作：</p>
+<p><img alt="MySqlSQL优化及锁机制-010" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-010.png"></p>
+<p><img alt="MySqlSQL优化及锁机制-011" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-011.png"></p>
+<p>当前会话当关闭MySQL自动提交后，修改表中的某一行数据，未提交前其他会话是不可见该修改的数据的；如果当前会话和修改某一行数据其他会话也修改该行数据则其他会话会一直等待，直到持有锁的会话commit后才会执行。
+如果当前会话和其他会话操作同一张表的不同行数据时，则相互不影响。</p>
+<p><strong>使用行锁时注意，无索引行或索引失效都会导致行锁变为表锁。</strong></p>
+<p><strong>间隙锁：</strong></p>
+<p>当我们用范围条件而不是相等条件检索数据，并请求共享或排他锁时，InnoDB会给符合条件的已有数据记录的索引项加锁，对于键值在条件范围内但并不存在的记录，叫做“间隙”。
+InnoDB也会对这个“间隙”加锁，这种锁机制就是所谓的间隙锁。</p>
+<p>因为Query执行过程中通过过范围查找的话，他会锁定整个范围内所有的索引键值，即使这个键值并不存在。</p>
+<p>间隙锁有一个比较致命的弱点，就是当锁定一个范围键值之后，即使某些不存在的键值也会被无辜的锁定，而造成在锁定的时候无法插入锁定键值范围内的任何数据。在某些场景下这可能会对性能造成很大的危害。</p>
+<p>如何锁定一行？在查询语句使用<code>for update</code>关键字：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl"> select * from test_innodb_lock where a=8 for update;
+</span></span></code></pre></div><p><img alt="MySqlSQL优化及锁机制-012" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-012.png"></p>
+<p>Innodb存储引擎由于实现了行级锁定，虽然在锁定机制的实现方面所带来的性能损耗可能比表级锁定会要更高一些，但是在整体并发处理能力方面要远远优于MyISAM的表级锁定的。
+当系统并发量较高的时候，Innodb的整体性能和MyISAM相比就会有比较明显的优势了。
+但是，Innodb的行级锁定同样也有其脆弱的一面，当我们使用不当的时候，可能会让Innodb的整体性能表现不仅不能比MyISAM高，甚至可能会更差。</p>
+<h3 id="总结">总结</h3>
+<ul>
+<li>MySQL锁分为全局锁、表级锁以及行级锁，不同的存储引擎支持锁的粒度有所不同，MyISAM 只支持到表级锁，InnoDB 则可以支持到行级锁，锁的粒度决定了业务的并发度，因此更推荐使用InnoDB</li>
+<li>InnoDB默认最小加锁粒度为行级锁，并且锁是加在索引上，如果SQL语句未命中索引，则走聚簇索引的全表扫描，表上每条记录都会上锁，导致并发能力下降，增大死锁的概率，因此需要为表合理的添加索引，线上查询尽量命中索引</li>
+<li>行级锁默认加 next-key lock，而根据不同的索引也有不同的加锁规则，我们可以根据加锁规分析加锁区间</li>
+<li>尽可能让所有数据检索都通过索引来完成，避免无索引行锁升级为表锁</li>
+<li>合理设计索引，尽量缩小锁的范围</li>
+<li>尽可能较少检索条件，避免间隙锁</li>
+<li>尽量控制事务大小，减少锁定资源量和时间长度</li>
+<li>尽可能低级别事务隔离</li>
+</ul>
+<h2 id="分库分表">分库分表</h2>
+<p>当数据库存储出现瓶颈的时候，就需要进行分库分表了。
+假设你现在在一个小公司，注册用户就 20 万，每天活跃用户就 1 万，每天单表数据量就 1000，然后高峰期每秒钟并发请求最多就 10 个。
+随着公司业务发展，过了几年，注册用户数达到了 5000 万，每天活跃用户数 200 万，每天单表数据量 50 万条，数据库磁盘容量不断消耗掉，高峰期并发达到惊人的 5000~8000，这时候你会发现你得系统已经支撑不住了已经挂掉了。</p>
+<p>一句话概括，随着业务的发展，数据库会遇到瓶颈，单表得数据量太大，会极大影响你的 sql 执行的性能，到了后面你的 sql 可能就跑的很慢了。
+所以为了维持功能的正常使用不得不分库分表。</p>
+<ul>
+<li>分表：分表就是把一个表的数据放到多个表中，然后查询的时候你就查一个表。比如按照用户 id 来分表，将一个用户的数据就放在一个表中。
+然后操作的时候你对一个用户就操作那个表就好了。分表主要是为了减少单张表的大小，解决单表数据量带来的性能问题。当单表数据增量过快，业界流传是超过500万的数据量就要考虑分表了。
+当然500万只是一个经验值，大家可以根据实际情况做出决策。</li>
+<li>分库：一个库一般我们经验而言，最多支撑到并发 2000，超过这个数字就一定要扩容了，而且一个健康的单库并发值你最好保持在每秒 1000 左右，不要太大。
+那么你可以将一个库的数据拆分到多个库中，访问的时候就访问一个库好了。</li>
+</ul>
+<p>分库分表是两个事情，别搞混了，可能是光分库不分表，也可能是光分表不分库，都有可能，但不管怎样分库分表一定是为了支撑高并发、数据量大两个问题的。
+分库分表是能不分就不分，因为分库分表也会带来一些问题：</p>
+<ul>
+<li>跨库关联查询</li>
+<li>分布式事务</li>
+<li>排序、分页、函数计算问题</li>
+<li>分布式ID</li>
+<li>多数据源</li>
+</ul>
+<h3 id="拆分方案">拆分方案</h3>
+<p>怎么拆分？拆分方案一般分为两种，水平拆分，垂直拆分。</p>
+<p>水平拆分的意思，基于数据划分，表结构相同，数据不同。例如，现有一个业务表，新建业务表2，业务表与业务表2中字段一致，将ID为奇数的存储在业务表中，偶数的存放在业务表2中。
+就是把一个表的数据给弄到多个库的多个表里去，但是每个库的表结构都一样，只不过每个库表放的数据是不同的，所有库表的数据加起来就是全部数据。
+水平拆分的意义，就是将数据均匀放更多的库里，然后用多个库来扛更高的并发，还有就是用多个库的存储容量来进行扩容。</p>
+<p>垂直拆分的意思，基于表或字段划分，表结构不同。例如，将业务表中不常用的字段name和age存放到业务表2中。
+就是把一个有很多字段的表给拆分成多个表，或者是多个库上去。每个库表的结构都不一样，每个库表都包含部分字段。
+一般来说，会将较少的访问频率很高的字段放到一个表里去，然后将较多的访问频率很低的字段放到另外一个表里去。
+因为数据库是有缓存的，你访问频率高的行字段越少，就可以在缓存里缓存更多的行，性能就越好，这个一般在表层面做的较多一些。</p>
+<ul>
+<li>
+<p>在一个库内拆分多个表：先分库，将不同数据库中的表拆分为了多个子表，多个子表存在于同一数据库中；
+<img alt="MySqlSQL优化及锁机制-013" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-013.png"></p>
+</li>
+<li>
+<p>用多库拆分一个表，将一个数据库中的表拆分到多个数据库中；
+<img alt="MySqlSQL优化及锁机制-014" src="/iblog/posts/annex/images/essays/MySqlSQL%E4%BC%98%E5%8C%96%E5%8F%8A%E9%94%81%E6%9C%BA%E5%88%B6-014.png"></p>
+</li>
+</ul>
+<p>在一个数据库中将一张表拆分为几个子表，在一定程度上可以解决单表查询性能的问题，但是也会遇到单数据库存储瓶颈这个问题，所以用的更多的还是将子表拆分到多个数据库中。</p>
+<p>除了垂直和水平拆分外，还有比较流行的分库分表方式，一种是按照range，即范围来分，就是每个库一段连续的数据，这个一般是按比如时间范围来的。
+但是这种一般较少用，因为很容易产生热点问题，大量的流量都打在最新的数据上了；另一种是按照某个字段的hash值，一下均匀分散。</p>
+<p>range：好处在于扩容的时候很简单，因为你只要预备好，给每个月都准备一个库就可以了，到了一个新的月份的时候，自然而然，就会写新的库了；
+缺点，但是大部分的请求，都是访问最新的数据。实际生产用 range，要看场景。</p>
+<p>hash：好处在于可以平均分配每个库的数据量和请求压力；
+坏处在于说扩容起来比较麻烦，会有一个数据迁移的过程，之前的数据需要重新计算 hash 值重新分配到不同的库或表。</p>
+<h3 id="数据迁移方案">数据迁移方案</h3>
+<p>现在有一个未分库分表的系统，未来要分库分表，如何设计才可以让系统从未分库分表动态切换到分库分表上？</p>
+<p>方案一：停机迁移</p>
+<ol>
+<li>网站或者 app 发布公告，例如，0 点到早上 6 点进行运维，无法访问；</li>
+<li>到时间将系统停掉，执行导数工具，将单库单表的数据读出来，写到分库分表里面去；</li>
+<li>导数完之后，需要改配置，验证一下数据；</li>
+</ol>
+<p>方案二：双写迁移</p>
+<ol>
+<li>在线上系统里面，之前所有写库的地方，增删改操作，除了对老库增删改，都加上对新库的增删改；</li>
+<li>重新部署系统，新数据库数据差太多，就写一个导数工具，跑起来读老库数据写新库，跑的时候要注意，老数据不要覆盖掉新数据；</li>
+<li>假设导完数据了，有可能数据还是存在不一致，那么就程序自动做一轮校验，比对新老库每个表的每条数据，就针对那些不一样的，从老库读数据再次写。
+反复循环，直到两个库每个表的数据都完全一致为止；</li>
+</ol>
+<h3 id="常见分库分表中间件">常见分库分表中间件</h3>
+<p><a href="https://github.com/alibaba/cobar/wiki">Cobar</a>：
+阿里 b2b 团队开发和开源的，属于 proxy 层方案，就是介于应用服务器和数据库服务器之间。应用程序通过 JDBC 驱动访问 Cobar 集群，Cobar 根据 SQL 和分库规则对 SQL 做分解，然后分发到 MySQL 集群不同的数据库实例上执行。早些年还可以用，但是最近几年都没更新了，基本没啥人用，差不多算是被抛弃的状态吧。而且不支持读写分离、存储过程、跨库 join 和分页等操作。</p>
+<p><a href="https://github.com/alibaba/tb_tddl">TDDL</a>：
+淘宝团队开发的，属于 client 层方案。支持基本的 crud 语法和读写分离，但不支持 join、多表查询等语法。目前使用的也不多，因为还依赖淘宝的 diamond 配置管理系统。</p>
+<p><a href="https://github.com/Qihoo360/Atlas">Atlas</a>：
+360 开源的，属于 proxy 层方案，以前是有一些公司在用的，但是确实有一个很大的问题就是社区最新的维护都在 5 年前了。所以，现在用的公司基本也很少了。</p>
+<p><a href="https://shardingsphere.apache.org/document/legacy/4.x/document/cn/overview">Sharding-jdbc</a>：
+当当开源的，属于 client 层方案，是 ShardingSphere 的 client 层方案， ShardingSphere 还提供 proxy 层的方案 Sharding-Proxy。确实之前用的还比较多一些，因为 SQL 语法支持也比较多，没有太多限制，而且截至 2019.4，已经推出到了 4.0.0-RC1 版本，支持分库分表、读写分离、分布式 id 生成、柔性事务（最大努力送达型事务、TCC 事务）。而且确实之前使用的公司会比较多一些（这个在官网有登记使用的公司，可以看到从 2017 年一直到现在，是有不少公司在用的），目前社区也还一直在开发和维护，还算是比较活跃，个人认为算是一个现在也可以选择的方案。</p>
+<p><a href="https://www.yuque.com/ccazhw/ml3nkf">Mycat</a>：
+基于 Cobar 改造的，属于 proxy 层方案，支持的功能非常完善，而且目前应该是非常火的而且不断流行的数据库中间件，社区很活跃，也有一些公司开始在用了。但是确实相比于 Sharding jdbc 来说，年轻一些，经历的锤炼少一些。</p>
+<p>综上，现在其实建议考量的，就是 Sharding-jdbc 和 Mycat，这两个都可以去考虑使用。无论分库还是分表，上面说的那些数据库中间件都是可以支持的。就是基本上那些中间件可以做到你分库分表之后，中间件可以根据你指定的某个字段值，比如说 userid，自动路由到对应的库上去，然后再自动路由到对应的表里去。</p>
+<p>Sharding-jdbc 这种 client 层方案的优点在于不用部署，运维成本低，不需要代理层的二次转发请求，性能很高，但是如果遇到升级啥的需要各个系统都重新升级版本再发布，各个系统都需要耦合 Sharding-jdbc 的依赖；</p>
+<p>Mycat 这种 proxy 层方案的缺点在于需要部署，自己运维一套中间件，运维成本高，但是好处在于对于各个项目是透明的，如果遇到升级之类的都是自己中间件那里搞就行了。</p>
+<p>通常来说，这两个方案其实都可以选用，但是建议中小型公司选用 Sharding-jdbc，client 层方案轻便，而且维护成本低，不需要额外增派人手，而且中小型公司系统复杂度会低一些，项目也没那么多；但是中大型公司最好还是选用 Mycat 这类 proxy 层方案，因为可能大公司系统和项目非常多，团队很大，人员充足，那么最好是专门弄个人来研究和维护 Mycat，然后大量项目直接透明使用即可。</p>
+<h2 id="参考链接">参考链接</h2>
+<ul>
+<li><a href="https://mp.weixin.qq.com/s/-Jipxjwe-jAax4hJSe-9Jg">https://mp.weixin.qq.com/s/-Jipxjwe-jAax4hJSe-9Jg</a></li>
+<li><a href="https://www.hollischuang.com/archives/6330">https://www.hollischuang.com/archives/6330</a></li>
+<li><a href="https://dev.mysql.com/doc/refman/8.0/en/using-explain.html">https://dev.mysql.com/doc/refman/8.0/en/using-explain.html</a></li>
+<li><a href="https://www.javanav.com/interview/7b1d6961b1e344fa9b6ea74819d4f417.html">https://www.javanav.com/interview/7b1d6961b1e344fa9b6ea74819d4f417.html</a></li>
+<li><a href="http://blog.chinaunix.net/uid-30272888-id-5602128.html">http://blog.chinaunix.net/uid-30272888-id-5602128.html</a></li>
+<li><a href="https://blog.codinglabs.org/articles/theory-of-mysql-index.html">https://blog.codinglabs.org/articles/theory-of-mysql-index.html</a></li>
+<li><a href="https://javaguide.cn/database/mysql/mysql-index.html">https://javaguide.cn/database/mysql/mysql-index.html</a></li>
+<li><a href="https://mp.weixin.qq.com/s/8qemhRg5MgXs1So5YCv0fQ">https://mp.weixin.qq.com/s/8qemhRg5MgXs1So5YCv0fQ</a></li>
+<li><a href="https://javaguide.cn/database/mysql/innodb-implementation-of-mvcc.html">https://javaguide.cn/database/mysql/innodb-implementation-of-mvcc.html</a></li>
+<li><a href="https://javabetter.cn/mysql/shiwu-shixian.html">https://javabetter.cn/mysql/shiwu-shixian.html</a></li>
+</ul>
+</div>
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+            </div>
+        </div>
+    </div>
+    
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+    <span class="ri-search-line"></span>
+</a>
+<div id="fastSearch">
+    <input id="searchInput" tabindex="0" autocomplete="off">
+    <ul id="searchResults"></ul>
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+    
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+        <svg t="1688614744062" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="2152" width="16" height="16"><path d="M966.4 323.2c-9.6-9.6-25.6-9.6-35.2 0l-416 416-425.6-416c-9.6-9.6-25.6-9.6-35.2 0-9.6 9.6-9.6 25.6 0 35.2l441.6 432c9.6 9.6 25.6 9.6 35.2 0l435.2-432C976 345.6 976 332.8 966.4 323.2z" p-id="2153" fill="#424242"></path></svg>    </a>
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+    </a>
+</div>
+    <footer class="footer">
+    <div id="footer_powered_by" class="powered_by">
+        <a href="https://varkai.com">Designed by VarKai,</a>
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+
+    <div id="footer_slogan" class="footer_slogan">
+        <span>from 2021</span>
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+
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+    new Darkmode({
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+        mixColor: '#f7f7f7', 
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+        buttonColorDark: '#212121', 
+        buttonColorLight: '#f7f7f7', 
+        saveInCookies: false, 
+        autoMatchOsTheme: true 
+    }).showWidget();
+
+    function addDarkmodeWidget(){
+        const hours = new Date().getHours();
+        if (hours >= 19 || hours <= 5){
+            new Darkmode({
+                right: '32px', 
+                bottom: 'unset', 
+                
+                time: '0.3s', 
+                mixColor: '#f7f7f7', 
+                backgroundColor: '#f7f7f7', 
+                buttonColorDark: '#212121', 
+                buttonColorLight: '#f7f7f7', 
+                saveInCookies: false, 
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+            }).toggle();
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+</body>
+
+</html>
\ No newline at end of file
diff --git a/docs/posts/index.html b/docs/posts/index.html
index f1bcbece..84d00d36 100644
--- a/docs/posts/index.html
+++ b/docs/posts/index.html
@@ -169,7 +169,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-generics/">Java泛型</a>
+                            <a href="/iblog/posts/javabasics/rookie-generics/">Java泛型</a>
                             <div class="post_time"><span class="date">07-15</span></div>
                         </div>
                     </div>
@@ -183,21 +183,21 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/java-keyword-volatile/">volatile关键字详解</a>
+                            <a href="/iblog/posts/javakeyword/java-keyword-volatile/">volatile关键字</a>
                             <div class="post_time"><span class="date">07-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/java-keyword-synchronized/">synchronized关键字详解</a>
+                            <a href="/iblog/posts/javakeyword/java-keyword-synchronized/">synchronized关键字</a>
                             <div class="post_time"><span class="date">07-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-arraylist/">ArrayList详解</a>
+                            <a href="/iblog/posts/detailed/java-arraylist/">ArrayList详解</a>
                             <div class="post_time"><span class="date">06-26</span></div>
                         </div>
                     </div>
@@ -211,14 +211,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/sql-select-fast/">MySQL详解</a>
+                            <a href="/iblog/posts/detailed/sql-select-fast/">MySQL详解</a>
                             <div class="post_time"><span class="date">05-30</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-always-problems/">Java程序常见问题</a>
+                            <a href="/iblog/posts/codeguide/java-always-problems/">Java程序常见问题</a>
                             <div class="post_time"><span class="date">05-28</span></div>
                         </div>
                     </div>
@@ -239,7 +239,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/distributed-lock/">分布式锁详解</a>
+                            <a href="/iblog/posts/detailed/distributed-lock/">分布式锁详解</a>
                             <div class="post_time"><span class="date">05-25</span></div>
                         </div>
                     </div>
@@ -652,7 +652,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/emp/front-learning-route/">前端学习路线</a>
+                            <a href="/iblog/posts/intro/front-learning-route/">前端学习路线</a>
                             <div class="post_time"><span class="date">02-29</span></div>
                         </div>
                     </div>
@@ -699,14 +699,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/uploadfile-code/">整合文件上传功能</a>
+                            <a href="/iblog/posts/toy/uploadfile-code/">Java整合文件上传功能</a>
                             <div class="post_time"><span class="date">08-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/pay-code/">整合支付功能</a>
+                            <a href="/iblog/posts/toy/pay-code/">Java整合支付功能</a>
                             <div class="post_time"><span class="date">08-10</span></div>
                         </div>
                     </div>
@@ -720,14 +720,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/pipeline-business/">管道流设计模式结合业务</a>
+                            <a href="/iblog/posts/toy/pipeline-business/">Java管道流设计模式结合业务</a>
                             <div class="post_time"><span class="date">06-15</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-project-reconstitution/">重构一个程序</a>
+                            <a href="/iblog/posts/codeguide/java-project-reconstitution/">重构一个程序</a>
                             <div class="post_time"><span class="date">04-20</span></div>
                         </div>
                     </div>
@@ -741,21 +741,21 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/distributed-id/">分布式ID</a>
+                            <a href="/iblog/posts/detailed/distributed-id/">分布式ID详解</a>
                             <div class="post_time"><span class="date">03-13</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-bugs/">如何减少及解决bug</a>
+                            <a href="/iblog/posts/codeguide/java-bugs/">如何减少及解决bug</a>
                             <div class="post_time"><span class="date">03-10</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/elasticsearch/">Elasticsearch详解</a>
+                            <a href="/iblog/posts/detailed/elasticsearch/">Elasticsearch详解</a>
                             <div class="post_time"><span class="date">02-14</span></div>
                         </div>
                     </div>
@@ -781,14 +781,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/clean-code/">整洁的代码</a>
+                            <a href="/iblog/posts/codeguide/clean-code/">整洁的代码</a>
                             <div class="post_time"><span class="date">09-01</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-design/">如何做好程序设计功能</a>
+                            <a href="/iblog/posts/codeguide/java-design/">如何做好程序设计功能</a>
                             <div class="post_time"><span class="date">08-02</span></div>
                         </div>
                     </div>
@@ -814,14 +814,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/data-structures-algorithms/">数据结构与算法</a>
+                            <a href="/iblog/posts/detailed/data-structures-algorithms/">数据结构与算法详解</a>
                             <div class="post_time"><span class="date">12-10</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-code-rule/">规范编写Java代码总结</a>
+                            <a href="/iblog/posts/codeguide/java-code-rule/">规范编写Java代码总结</a>
                             <div class="post_time"><span class="date">11-25</span></div>
                         </div>
                     </div>
@@ -835,56 +835,56 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-mq/">MQ详解</a>
+                            <a href="/iblog/posts/detailed/java-mq/">Kafka详解</a>
                             <div class="post_time"><span class="date">10-19</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-java-container/">Java集合</a>
+                            <a href="/iblog/posts/javabasics/rookie-java-container/">Java集合</a>
                             <div class="post_time"><span class="date">10-04</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-reflect/">Java反射</a>
+                            <a href="/iblog/posts/javabasics/rookie-reflect/">Java反射</a>
                             <div class="post_time"><span class="date">10-02</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/eye-beam/">Java程序常见故障排查命令及工具</a>
+                            <a href="/iblog/posts/codeguide/eye-beam/">Java程序常见故障排查命令及工具</a>
                             <div class="post_time"><span class="date">09-08</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-transaction/">分布式事务详解</a>
+                            <a href="/iblog/posts/detailed/java-transaction/">分布式事务详解</a>
                             <div class="post_time"><span class="date">08-02</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-objectclass-methods/">JavaObject类方法</a>
+                            <a href="/iblog/posts/javabasics/rookie-objectclass-methods/">JavaObject类方法</a>
                             <div class="post_time"><span class="date">07-10</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-small-service/">微服务治理详解</a>
+                            <a href="/iblog/posts/detailed/java-small-service/">微服务治理详解</a>
                             <div class="post_time"><span class="date">06-21</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-redis/">Redis详解</a>
+                            <a href="/iblog/posts/detailed/java-redis/">Redis详解</a>
                             <div class="post_time"><span class="date">06-17</span></div>
                         </div>
                     </div>
@@ -905,14 +905,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-multi-thread/">Java多线程</a>
+                            <a href="/iblog/posts/javabasics/rookie-multi-thread/">Java多线程</a>
                             <div class="post_time"><span class="date">05-05</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-hashmap/">HashMap详解</a>
+                            <a href="/iblog/posts/detailed/java-hashmap/">HashMap详解</a>
                             <div class="post_time"><span class="date">05-03</span></div>
                         </div>
                     </div>
@@ -968,14 +968,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-netty/">Netty详解</a>
+                            <a href="/iblog/posts/detailed/java-netty/">Netty详解</a>
                             <div class="post_time"><span class="date">04-09</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-io/">JavaIO</a>
+                            <a href="/iblog/posts/javabasics/rookie-io/">JavaIO</a>
                             <div class="post_time"><span class="date">04-09</span></div>
                         </div>
                     </div>
@@ -1031,14 +1031,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/nginx-start/">Nginx介绍</a>
+                            <a href="/iblog/posts/intro/nginx-start/">Nginx入门</a>
                             <div class="post_time"><span class="date">03-04</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-object-oriented/">Java面向对象</a>
+                            <a href="/iblog/posts/javabasics/rookie-object-oriented/">Java面向对象</a>
                             <div class="post_time"><span class="date">02-15</span></div>
                         </div>
                     </div>
@@ -1052,21 +1052,21 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-operation/">Java运算</a>
+                            <a href="/iblog/posts/javabasics/rookie-operation/">Java运算</a>
                             <div class="post_time"><span class="date">01-30</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-datatype/">Java数据类型</a>
+                            <a href="/iblog/posts/javabasics/rookie-datatype/">Java数据类型</a>
                             <div class="post_time"><span class="date">01-20</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-exception/">Java异常</a>
+                            <a href="/iblog/posts/javabasics/rookie-exception/">Java异常</a>
                             <div class="post_time"><span class="date">01-13</span></div>
                         </div>
                     </div>
@@ -1113,7 +1113,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/docker-start/">Docker入门</a>
+                            <a href="/iblog/posts/intro/docker-start/">Docker入门</a>
                             <div class="post_time"><span class="date">04-07</span></div>
                         </div>
                     </div>
@@ -1127,7 +1127,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/cas-detail/">CAS详解</a>
+                            <a href="/iblog/posts/detailed/cas-detail/">CAS详解</a>
                             <div class="post_time"><span class="date">04-04</span></div>
                         </div>
                     </div>
@@ -1240,28 +1240,28 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/"></a>
+                            <a href="/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97/"></a>
                             <div class="post_time"><span class="date">01-01</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/"></a>
+                            <a href="/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97/"></a>
                             <div class="post_time"><span class="date">01-01</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/"></a>
+                            <a href="/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/"></a>
                             <div class="post_time"><span class="date">01-01</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/"></a>
+                            <a href="/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/"></a>
                             <div class="post_time"><span class="date">01-01</span></div>
                         </div>
                     </div>
diff --git a/docs/posts/index.xml b/docs/posts/index.xml
index 2ff122c6..2ff3cbbd 100644
--- a/docs/posts/index.xml
+++ b/docs/posts/index.xml
@@ -17,9 +17,9 @@
     </item>
     <item>
       <title>Java泛型</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-generics/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-generics/</link>
       <pubDate>Mon, 15 Jul 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-generics/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-generics/</guid>
       <description>概览 在Java中，泛型是一种强大的编程特性，允许类、接口和方法在定义时声明一种参数化类型，而在使用时可以指定具体的类型参数。泛型的主要目的是提高代码的重用性和类</description>
     </item>
     <item>
@@ -30,14 +30,14 @@
       <description>概览 语法糖是指编程语言中的一种语法结构，它们并不提供新的功能，而是为了让代码更易读、更易写而设计的。 语法糖使得某些常见的编程模式或操作变得更加简洁和直观，但在底</description>
     </item>
     <item>
-      <title>synchronized关键字详解</title>
+      <title>synchronized关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</guid>
       <description>synchronized synchronized是Java提供的关键字译为同步，是Java中用于实现线程同步的一种机制。它可以确保在同一时间只有一个线程能够执行某段代码，从而避免线程</description>
     </item>
     <item>
-      <title>volatile关键字详解</title>
+      <title>volatile关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</guid>
@@ -45,9 +45,9 @@
     </item>
     <item>
       <title>ArrayList详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</link>
       <pubDate>Wed, 26 Jun 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</guid>
       <description>ArrayList 在List接口实现类中，最常用的就是ArrayList，ArrayList类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删</description>
     </item>
     <item>
@@ -59,16 +59,16 @@
     </item>
     <item>
       <title>MySQL详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/sql-select-fast/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/sql-select-fast/</link>
       <pubDate>Thu, 30 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/sql-select-fast/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/sql-select-fast/</guid>
       <description>MySQL介绍 MySQL 是一种关系型数据库，主要用于持久化存储我们系统中的一些数据。 MySQL 如此流行的原因，主要具有下面这些优点： 成熟稳定，功能完善。 开源免费。 文档丰富，既有</description>
     </item>
     <item>
       <title>Java程序常见问题</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-always-problems/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-always-problems/</link>
       <pubDate>Tue, 28 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-always-problems/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-always-problems/</guid>
       <description>CPU使用过高 一般在生产环境排查程序故障，都会查看日志什么的，但是有些故障日志是看不出来的，就比如：CPU使用过高。 那应该怎么办呢？我们需要结合linux命令和</description>
     </item>
     <item>
@@ -87,9 +87,9 @@
     </item>
     <item>
       <title>分布式锁详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/distributed-lock/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/distributed-lock/</link>
       <pubDate>Sat, 25 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/distributed-lock/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/distributed-lock/</guid>
       <description>概述 在代码里面我们常用ReetrantLock、synchronized保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。 类似这样： public</description>
     </item>
     <item>
@@ -500,9 +500,9 @@
     </item>
     <item>
       <title>前端学习路线</title>
-      <link>https://whiteppure.github.io/iblog/posts/emp/front-learning-route/</link>
+      <link>https://whiteppure.github.io/iblog/posts/intro/front-learning-route/</link>
       <pubDate>Thu, 29 Feb 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/emp/front-learning-route/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/front-learning-route/</guid>
       <description>基础知识 网络知识 HTTP DNS 域名 云服务 网络安全 HTTPS CORS 网络渗透 OWASP HTML CSS JavaScript JQuery Ajax ES6-ES11 综合应用 工程化体系 代码规范 CSS预处理器 Less Sass PostCSS Node Promise Axios 工具 包管理工具 Yarn Npm 打包工具 Webpack Parcel 代码格式化工具</description>
     </item>
     <item>
@@ -541,17 +541,17 @@
       <description>Nacos安装启动 一键傻瓜试安装即可，官网写的很清楚这里不在赘述。 这里以Window环境安装为例。 启动Nacos将模式改为单机模式。 启动成功 Nacos相关配置 demo-dev.yaml</description>
     </item>
     <item>
-      <title>整合文件上传功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/uploadfile-code/</link>
+      <title>Java整合文件上传功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</link>
       <pubDate>Fri, 11 Aug 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/uploadfile-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</guid>
       <description>结构 pom.xml fastdfs-client-java-1.27.jar：点击下载 &amp;lt;dependencies&amp;gt; &amp;lt;!-- fastdfs --&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.csource&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;fastdfs-client-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;1.27&amp;lt;/version&amp;gt; &amp;lt;systemPath&amp;gt;${project.basedir}/lib/fastdfs-client-java-1.27.jar&amp;lt;/systemPath&amp;gt; &amp;lt;scope&amp;gt;system&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;!--aliyun oss 依赖--&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.aliyun.oss&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;aliyun-sdk-oss&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt;</description>
     </item>
     <item>
-      <title>整合支付功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/pay-code/</link>
+      <title>Java整合支付功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pay-code/</link>
       <pubDate>Thu, 10 Aug 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/pay-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pay-code/</guid>
       <description>结构 完整代码：https://gitee.com/gitee_pikaqiu/easy-archetype pom.xml &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.alipay.sdk&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;alipay-sdk-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;4.9.9&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt;</description>
     </item>
     <item>
@@ -562,17 +562,17 @@
       <description>常见参数校验 在日常的接口开发中，为了防止非法参数对业务造成影响，经常需要对接口的参数做校验。最简单就是用if条件语句来判断，但是随着参数越来越多，业务越来越复杂</description>
     </item>
     <item>
-      <title>管道流设计模式结合业务</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/pipeline-business/</link>
+      <title>Java管道流设计模式结合业务</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</link>
       <pubDate>Thu, 15 Jun 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/pipeline-business/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</guid>
       <description>流程图 代码实现 完整代码：https://gitee.com/gitee_pikaqiu/easy-pipeline pom &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.plugin&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-plugin-core&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;${spring.plugin.core.version}&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt;</description>
     </item>
     <item>
       <title>重构一个程序</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-project-reconstitution/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-project-reconstitution/</link>
       <pubDate>Thu, 20 Apr 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-project-reconstitution/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-project-reconstitution/</guid>
       <description>什么是重构 摘自《重构：改善既有代码的设计》 重构(名词形式): 对软件内部结构的一种调整，目的是在不改变软件可观察行为的前提下，提高其可理解性，降低其修改成本。 重构</description>
     </item>
     <item>
@@ -583,24 +583,24 @@
       <description>SpringMVC SpringWebMVC是建立在Servlet API上的原始Web框架，从一开始就包含在Spring框架中。正式名称 &amp;ldquo;Spring Web MVC &amp;ldquo;来自其源模块的名称（s</description>
     </item>
     <item>
-      <title>分布式ID</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/distributed-id/</link>
+      <title>分布式ID详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/distributed-id/</link>
       <pubDate>Mon, 13 Mar 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/distributed-id/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/distributed-id/</guid>
       <description>分布式ID 在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。 但随着数据日渐增长，主从同步也扛不住了，</description>
     </item>
     <item>
       <title>如何减少及解决bug</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-bugs/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-bugs/</link>
       <pubDate>Fri, 10 Mar 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-bugs/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-bugs/</guid>
       <description>bug的起源: 1945年，一只小飞蛾钻进了计算机电路里，导致系统无法工作，一位名叫格蕾丝·赫柏的人把飞蛾拍死在工作日志上，写道：就是这个 bug(虫子)，害我们今</description>
     </item>
     <item>
       <title>Elasticsearch详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/elasticsearch/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/elasticsearch/</link>
       <pubDate>Tue, 14 Feb 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/elasticsearch/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/elasticsearch/</guid>
       <description>概览 Elasticsearch，简称为 ES， ES是一个开源的高扩展的分布式全文搜索引擎， 是整个 ElasticStack 技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可</description>
     </item>
     <item>
@@ -619,16 +619,16 @@
     </item>
     <item>
       <title>整洁的代码</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/clean-code/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/clean-code/</link>
       <pubDate>Thu, 01 Sep 2022 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/clean-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/clean-code/</guid>
       <description>为什么要写整洁的代码 为什么要写整洁的代码,回答这个问题之前,也许应该想想写糟糕的代码的原因 是想快点完成吗?还是要赶时间吗?有可能.或许你觉得自己要干好所需要的时</description>
     </item>
     <item>
       <title>如何做好程序设计功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-design/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-design/</link>
       <pubDate>Tue, 02 Aug 2022 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-design/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-design/</guid>
       <description>功能设计流程图 与外部系统交互、本系统模块之间流程，比较好用的画圈软件draw .io或在线的process on 数据库设计 从DDD角度界限上下文、ER图、评审表结构设</description>
     </item>
     <item>
@@ -646,17 +646,17 @@
       <description>写在前面 本文中所涉及的程序均为Java开发，如果您想要直接使用这些工具需要提前配置Java环境。所涉及到的程序均提供完整代码，如果您有兴趣可以尝试运行。 使用ja</description>
     </item>
     <item>
-      <title>数据结构与算法</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/data-structures-algorithms/</link>
+      <title>数据结构与算法详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/data-structures-algorithms/</link>
       <pubDate>Fri, 10 Dec 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/data-structures-algorithms/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/data-structures-algorithms/</guid>
       <description>数据结构 数据结构是一门研究组织数据方式的学科，有了编程语言也就有了数据结构，学好数据结构可以编写出更有效率的代码。数据结构是算法的基础，想要学好算法，就必须把数</description>
     </item>
     <item>
       <title>规范编写Java代码总结</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-code-rule/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-code-rule/</link>
       <pubDate>Thu, 25 Nov 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-code-rule/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-code-rule/</guid>
       <description>编码规范 我们为什么要遵守规范来编码？ 是因为通常在编码过程中我们不只自己进行开发，通常需要一个团队来进行，开发好之后还需要维护，所以编码规范就显的尤为重要。 代码维</description>
     </item>
     <item>
@@ -667,59 +667,59 @@
       <description>网络协议 以下内容摘自百度百科： https://baike.baidu.com/item/网络协议/328636 https://baike.baidu.com/i</description>
     </item>
     <item>
-      <title>MQ详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-mq/</link>
+      <title>Kafka详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-mq/</link>
       <pubDate>Tue, 19 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-mq/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-mq/</guid>
       <description>概览 MQ 即 messagequeue 消息队列，是分布式系统的重要组件，主要解决异步消息，应用解耦，消峰等问题。从而实现高可用，高性能，可伸缩和最终一致性的架构。使用较多的MQ有：acti</description>
     </item>
     <item>
       <title>Java集合</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-java-container/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-java-container/</link>
       <pubDate>Mon, 04 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-java-container/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-java-container/</guid>
       <description>概述 Java中的集合主要包括Collection和Map两种，Collection存储着对象的集合，而Map存储着键值对的映射表。 数组 如果你看过ArrayLis</description>
     </item>
     <item>
       <title>Java反射</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-reflect/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-reflect/</link>
       <pubDate>Sat, 02 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-reflect/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-reflect/</guid>
       <description>概述 在Java程序运行状态中，对于任意一个实体类，都能够知道这个类的所有属性和方法，对于任意一个对象，都能够调用它的任意方法和属性。这种动态获取信息以及动态调用</description>
     </item>
     <item>
       <title>Java程序常见故障排查命令及工具</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/eye-beam/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/eye-beam/</link>
       <pubDate>Wed, 08 Sep 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/eye-beam/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/eye-beam/</guid>
       <description>故障排查命令 收录Linux常用命令，以下命令来自https://www.bilibili.com/video/BV14A411378a 关机/重启/注销 常用命令 作</description>
     </item>
     <item>
       <title>分布式事务详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-transaction/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-transaction/</link>
       <pubDate>Mon, 02 Aug 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-transaction/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-transaction/</guid>
       <description>基础概念 什么是事务 什么是事务？举个例子：你去超市买东西，&amp;ldquo;一手交钱，一手交货&amp;quot;就是一个事务的例子。 交钱和交货必须同时成功，事务才算成功，其</description>
     </item>
     <item>
       <title>JavaObject类方法</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-objectclass-methods/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-objectclass-methods/</link>
       <pubDate>Sat, 10 Jul 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-objectclass-methods/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-objectclass-methods/</guid>
       <description>概览 Object类位于java.lang包中，编译时会自动导入。当我们创建一个类时，如果没有明确继承一个父类，那么它就会自动继承Object，成为Object的</description>
     </item>
     <item>
       <title>微服务治理详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-small-service/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-small-service/</link>
       <pubDate>Mon, 21 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-small-service/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-small-service/</guid>
       <description>什么是微服务架构 In short， the microservice architectural style is an approach to developing a single application as a suite of small services， each running in its own process and communicating with lightweight mechanisms， often an HTTP resource API。 These services are built around business capabilities and independently deployable</description>
     </item>
     <item>
       <title>Redis详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-redis/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-redis/</link>
       <pubDate>Thu, 17 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-redis/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-redis/</guid>
       <description>Redis概述 参考文章： https://www.runoob.com/redis/redis-intro.html https://www.redis.com.cn/redis-interview-questions.html 什么是Redis Redis(Remote Dictionary Server) Redis 是一个开源的使用 ANSI C 语言编写、遵守 BSD 协议、支持网络、可基于内存亦可持久化的日志型、Key-Value 数据库，</description>
     </item>
     <item>
@@ -738,16 +738,16 @@
     </item>
     <item>
       <title>Java多线程</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-multi-thread/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-multi-thread/</link>
       <pubDate>Wed, 05 May 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-multi-thread/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-multi-thread/</guid>
       <description>线程与进程 进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。 线程是操作系统能够进行运算调度的最小单位。它被包</description>
     </item>
     <item>
       <title>HashMap详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</link>
       <pubDate>Mon, 03 May 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</guid>
       <description>HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问</description>
     </item>
     <item>
@@ -801,16 +801,16 @@
     </item>
     <item>
       <title>JavaIO</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-io/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-io/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-io/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-io/</guid>
       <description>概览 IO，即in和out的缩写，也就是输入和输出，指应用程序和外部设备之间的数据传递，常见的外部设备包括文件、管道、网络连接。 从计算机结构的角度来看IO，IO就</description>
     </item>
     <item>
       <title>Netty详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-netty/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-netty/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-netty/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-netty/</guid>
       <description>Netty 参考文章：https://dongzl.github.io/netty-handbook/#/ 概述 Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers &amp;amp; clients. Netty 是一个异步的、基于事</description>
     </item>
     <item>
@@ -863,17 +863,17 @@
       <description>为什么要学习JVM 大部分Java开发人员，除了会在项目中使用到与Java平台相关的各种高精尖技术，对于Java技术的核心Java虚拟机了解甚少。 一些有一定工作经</description>
     </item>
     <item>
-      <title>Nginx介绍</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/nginx-start/</link>
+      <title>Nginx入门</title>
+      <link>https://whiteppure.github.io/iblog/posts/intro/nginx-start/</link>
       <pubDate>Thu, 04 Mar 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/nginx-start/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/nginx-start/</guid>
       <description>Nginx介绍 Nginx (&amp;ldquo;engine x&amp;rdquo;)是一个高性能的HTTP和反向代理服务器，特点是占有内存少，并发能力强，事实上Nginx的并发能力确实在同类型的网页服务器中表</description>
     </item>
     <item>
       <title>Java面向对象</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-object-oriented/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-object-oriented/</link>
       <pubDate>Mon, 15 Feb 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-object-oriented/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-object-oriented/</guid>
       <description>概览 面向对象简称OO(object-oriented)是相对面向过程(procedure-oriented)来说的，是一种编程思想，Java就是一门面向对象的语</description>
     </item>
     <item>
@@ -885,23 +885,23 @@
     </item>
     <item>
       <title>Java运算</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-operation/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-operation/</link>
       <pubDate>Sat, 30 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-operation/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-operation/</guid>
       <description>运算符与表达式 运算符 运算符指明对操作数的运算方式。组成表达式的Java操作符有很多种。 运算符按照其要求的操作数数目来分，可以有单目运算符、双目运算符和三目运算符</description>
     </item>
     <item>
       <title>Java数据类型</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-datatype/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-datatype/</link>
       <pubDate>Wed, 20 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-datatype/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-datatype/</guid>
       <description>基本类型 Java语言提供了八种基本类型。六种数值类型（四个整数型，两个浮点型），一种字符类型，还有一种布尔型，俗称4类8种。 这里只介绍称4类8种，实际上，Jav</description>
     </item>
     <item>
       <title>Java异常</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-exception/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-exception/</link>
       <pubDate>Wed, 13 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-exception/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-exception/</guid>
       <description>异常类型 Throwable可以用来表示任何可以作为异常抛出的类，分为两种：Error 和 Exception。 其中Error用来表示Java程序无法处理的错误，这类</description>
     </item>
     <item>
@@ -934,9 +934,9 @@
     </item>
     <item>
       <title>Docker入门</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/docker-start/</link>
+      <link>https://whiteppure.github.io/iblog/posts/intro/docker-start/</link>
       <pubDate>Tue, 07 Apr 2020 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/docker-start/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/docker-start/</guid>
       <description>概述 Docker属于Linux容器的一种封装，提供简单易用的容器使用接口。它是目前流行的Linux容器解决方案。Docker将应用程序与该程序的依赖，打包在一个</description>
     </item>
     <item>
@@ -955,9 +955,9 @@
     </item>
     <item>
       <title>CAS详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/cas-detail/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/cas-detail/</link>
       <pubDate>Sat, 04 Apr 2020 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/cas-detail/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/cas-detail/</guid>
       <description>CAS CAS全称为Compare and Swap被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更</description>
     </item>
     <item>
@@ -1053,30 +1053,30 @@
     </item>
     <item>
       <title></title>
-      <link>https://whiteppure.github.io/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/static%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>https://whiteppure.github.io/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/strictfp%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>https://whiteppure.github.io/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/this%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
     </item>
     <item>
       <title></title>
-      <link>https://whiteppure.github.io/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97/</link>
       <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97%E8%AF%A6%E8%A7%A3/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javakeyword/transient%E5%85%B3%E9%94%AE%E5%AD%97/</guid>
       <description></description>
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diff --git a/docs/posts/intro/docker-start/index.html b/docs/posts/intro/docker-start/index.html
new file mode 100644
index 00000000..c596d2c7
--- /dev/null
+++ b/docs/posts/intro/docker-start/index.html
@@ -0,0 +1,603 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Docker入门 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="概述 Docker属于Linux容器的一种封装，提供简单易用的容器使用接口。它是目前流行的Linux容器解决方案。Docker将应用程序与该程序的依赖，打包在一个" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/zozo.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/highlight.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/img.css" />
+
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+</head>
+
+<body>
+    <div class="post-password">
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+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
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+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Docker入门</h2>
+                        <span id="post_page_title_date" class="date">2020.04.07</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
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+                    <div class="post_content markdown"><h2 id="概述">概述</h2>
+<p><code>Docker</code>属于<code>Linux</code>容器的一种封装，提供简单易用的容器使用接口。它是目前流行的<code>Linux</code>容器解决方案。<code>Docker</code>将应用程序与该程序的依赖，打包在一个文件里面。运行这个文件，就会生成一个虚拟容器。
+程序在这个虚拟容器里运行，就好像在真实的物理机上运行一样。有了 <code>Docker</code>，就不用担心环境问题。总体来说<code>Docker</code>的接口相当简单，用户可以方便地创建和使用容器，把自己的应用放入容器。
+容器还可以进行版本管理、复制、分享、修改，就像管理普通的代码一样。</p>
+<p><code>Docker</code>可以提供一次性的环境。比如，本地测试他人的软件、持续集成的时候提供单元测试和构建的环境。
+还可以提供弹性的云服务，因为<code>Docker</code>容器可以随开随关，很适合动态扩容和缩容。
+<code>Docker</code>最常见的就是通过多个容器，组建微服务架构，一台机器可以跑多个服务，因此在本机就可以模拟出微服务架构。</p>
+<h2 id="linux上安装">Linux上安装</h2>
+<p>2017年的3月1号之后，<code>Docker</code>的版本命名开始发生变化，同时将CE版本和EE版本进行分开。</p>
+<ul>
+<li>Docker社区版（CE）：为了开发人员或小团队创建基于容器的应用,与团队成员分享和自动化的开发管道。<code>docker-ce</code>提供了简单的安装和快速的安装，以便可以立即开始开发。<code>docker-ce</code>集成和优化，基础设施。（免费）</li>
+<li>Docker企业版（EE）：专为企业的发展和IT团队建立谁。<code>docker-ee</code>为企业提供最安全的容器平台，以应用为中心的平台。（付费）</li>
+</ul>
+<p>以下是<code>CentOS</code>或<code>RHEL</code>上使用<code>yum</code>来安装<code>Docker</code>示例。</p>
+<ol>
+<li><code>Docker</code>依赖于系统的一些必要的工具，所以先安装依赖。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">yum install -y yum-utils device-mapper-persistent-data lvm2
+</span></span></code></pre></div></li>
+<li>通过使用<code>yum-config-manager</code>来设置<code>Docker</code>的稳定仓库。(在阿里云镜像站上面可以找到<code>docker-ce</code>的软件源，使用国内的源速度比较快)。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
+</span></span></code></pre></div></li>
+<li>安装<code>docker-ce</code>，社区版，免费。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">yum clean allyum makecache fastyum -y install docker-ce
+</span></span></code></pre></div></li>
+<li>启动服务。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl"> <span class="c1">#service 命令的用法</span>
+</span></span><span class="line"><span class="cl">$ sudo service docker start
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="c1">#systemctl 命令的用法</span>
+</span></span><span class="line"><span class="cl">$ sudo systemctl start docker
+</span></span></code></pre></div></li>
+<li>查看安装版。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker version
+</span></span></code></pre></div></li>
+<li><code>Docker</code>需要用户具有<code>sudo</code>权限，为了避免每次命令都输入<code>sudo</code>，可以把用户加入<code>Docker</code>用户组。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">sudo usermod -aG docker <span class="nv">$USER</span>
+</span></span></code></pre></div></li>
+</ol>
+<h2 id="配置镜像">配置镜像</h2>
+<p>由于网速原因，可以配置一下国内的镜像加速器：</p>
+<ul>
+<li>中科大镜像: <a href="https://docker.mirrors.ustc.edu.cn">https://docker.mirrors.ustc.edu.cn</a></li>
+<li>网易: <a href="https://hub-mirror.c.163.com">https://hub-mirror.c.163.com</a></li>
+<li>阿里云: <a href="https://<%E4%BD%A0%E7%9A%84ID>.mirror.aliyuncs.com">https://&lt;你的ID&gt;.mirror.aliyuncs.com</a></li>
+<li>七牛云加速器: <a href="https://reg-mirror.qiniu.com">https://reg-mirror.qiniu.com</a></li>
+</ul>
+<p>以阿里云获取镜像地址为例， <a href="https://cr.console.aliyun.com/cn-hangzhou/instances/mirrors">https://cr.console.aliyun.com/cn-hangzhou/instances/mirrors</a>登陆后，左侧菜单选中镜像加速器就可以看到你的专属地址了。
+<img alt="获取阿里云docker地址" src="/iblog/posts/annex/images/application/%E8%8E%B7%E5%8F%96%E9%98%BF%E9%87%8C%E4%BA%91docker%E5%9C%B0%E5%9D%80.jpg">
+配置<code>Docker</code>镜像地址，添加以下内容：
+<img alt="docker配置" src="/iblog/posts/annex/images/application/docker%E9%85%8D%E7%BD%AE.jpg"></p>
+<p>也可以创建或编辑<code>/etc/docker/daemon.json</code>文件，并添加以下内容：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">{
+</span></span><span class="line"><span class="cl">  &#34;debug&#34;: true,
+</span></span><span class="line"><span class="cl">  &#34;experimental&#34;: false,
+</span></span><span class="line"><span class="cl">  &#34;registry-mirrors&#34;: [
+</span></span><span class="line"><span class="cl">    &#34;https://docker.mirrors.ustc.edu.cn&#34;
+</span></span><span class="line"><span class="cl">  ]
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>配置文件修改后，需要重启<code>Docker</code>服务使其生效：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">sudo systemctl daemon-reload
+</span></span><span class="line"><span class="cl">sudo systemctl restart docker
+</span></span></code></pre></div><p>在终端执行<code>docker info</code>命令。
+<img alt="docker信息" src="/iblog/posts/annex/images/application/docker%E4%BF%A1%E6%81%AF.jpg"></p>
+<p>出现上图所示，<code>Docker</code>镜像加速器配置成功。</p>
+<h2 id="工作原理">工作原理</h2>
+<p><img alt="docker架构" src="/iblog/posts/annex/images/application/docker%E6%9E%B6%E6%9E%84.png"></p>
+<p><code>Docker</code>架构分为三部分，客户端、宿主机、注册中心。</p>
+<ol>
+<li><code>Docker</code>客户端是用户与<code>Docker</code>交互的接口。用户通过客户端输入命令（如 <code>docker run</code>），这些命令会发送到<code>Docker</code>守护进程来执行。</li>
+<li>宿主机运行<code>Docker</code>守护进程，管理容器的生命周期。宿主机负责从注册中心拉取镜像、创建和管理容器，以及处理与容器相关的所有任务。</li>
+<li><code>Docker</code>注册中心用于存储和分发<code>Docker</code>镜像。常见的公共注册中心是<code>Docker Hub</code>，但用户也可以设置私有的注册中心。注册中心存储镜像，供宿主机下载。</li>
+</ol>
+<p>例如，当输入<code>docker run mysql:5.6</code>命令，告诉<code>Docker</code>要运行一个MySQL 5.6版本的容器。
+<code>Docker</code>客户端将用户的命令发送给宿主机上的<code>Docker</code>守护进程。<code>Docker</code>守护进程首先会在本地检查是否存在<code>mysql:5.6</code>镜像。
+如果本地没有找到<code>mysql:5.6</code>镜像，守护进程会向注册中心请求下载这个镜像。如果本地已经有这个镜像，则跳过下载步骤。
+如果需要从注册中心下载镜像，守护进程会连接到<code>Docker</code>注册中心，并拉取<code>mysql:5.6</code>镜像。
+下载完成后，<code>Docker</code>守护进程会根据<code>mysql:5.6</code>镜像创建一个新的容器。最后<code>Docker</code>守护进程为容器分配资源，并启动容器。MySQL服务会在这个容器内运行起来。</p>
+<h2 id="常用命令">常用命令</h2>
+<ul>
+<li>查看当前运行的镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker ps
+</span></span></code></pre></div><ul>
+<li>查看所有镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker ps -a
+</span></span></code></pre></div><ul>
+<li>停止容器。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker stop 容器名称
+</span></span></code></pre></div><ul>
+<li>删除镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker rmi 镜像名称
+</span></span></code></pre></div><ul>
+<li>下载镜像，若不指定版本为最新版本。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker pull 镜像:版本
+</span></span></code></pre></div><ul>
+<li>查看当前本地仓库的镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker images
+</span></span></code></pre></div><ul>
+<li>查看远程仓库镜像。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">docker search 镜像名
+</span></span></code></pre></div><p>以安装运行<code>nginx</code>为例。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-shell" data-lang="shell"><span class="line"><span class="cl">// docker run 包括下载镜像<span class="o">(</span>pull<span class="o">)</span>,创建容器<span class="o">(</span>create<span class="o">)</span>,运行容器<span class="o">(</span>start<span class="o">)</span> 可用dock -h查看帮助
+</span></span><span class="line"><span class="cl">// --rm 表明这是一个临时的容器,关闭的话会自动删除
+</span></span><span class="line"><span class="cl">// --name 容器名称
+</span></span><span class="line"><span class="cl">// -p 外部服务器端口映射docker容器端口
+</span></span><span class="line"><span class="cl">docker run --rm --name myNginx -p 80:80 nginx:版本
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 查看容器日志
+</span></span><span class="line"><span class="cl">docker logs myNginx
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 进入容器
+</span></span><span class="line"><span class="cl">docker <span class="nb">exec</span> -it myNginx bash
+</span></span></code></pre></div></div>
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diff --git a/docs/posts/intro/front-learning-route/index.html b/docs/posts/intro/front-learning-route/index.html
new file mode 100644
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@@ -0,0 +1,1513 @@
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+<html lang="zh" >
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+	
+	
+	<title>前端学习路线 ｜ 脚踏实地</title>
+	
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+                    性能优化和监控
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+</div>
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+    <div class="site_title_container">
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+            <h1>
+                <a href="https://whiteppure.github.io/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
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+                    <i class="ri-rss-fill"></i>
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+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1688701481347" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3517" width="16" height="16"><path d="M425.610455 85.814544H149.05897A42.303635 42.303635 0 0 0 106.6274 128.075535V896.492068c0 23.326702 18.976933 42.26099 42.43157 42.26099h682.743143a42.559504 42.559504 0 0 0 42.431569-42.559504v-384.016365a42.644793 42.644793 0 0 1 85.289587 0v384.016365A127.849091 127.849091 0 0 1 831.802113 1024H149.05897A127.635867 127.635867 0 0 1 21.337813 896.449423V128.03289A127.593222 127.593222 0 0 1 149.101614 0.524957h276.466196a42.644793 42.644793 0 0 1 0 85.289587z m564.062683 158.08425l-170.579174 170.579173a42.644793 42.644793 0 1 1-60.299738-60.299738L856.578738 256.393718H618.364922a42.644793 42.644793 0 1 1 0-85.289587h238.213816l-97.784512-97.784511A42.644793 42.644793 0 1 1 819.093964 13.019882l170.579174 170.579174a42.644793 42.644793 0 0 1 0 60.299738zM149.272194 597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h51.514911c59.190973 0 107.891327 23.284057 107.976617 97.102195 0 71.003581-49.46796 102.347504-106.185536 102.347504h-31.343923v66.781747a32.282109 32.282109 0 0 1-64.606862 0V597.552066z m92.709781 100.215264c31.429213 0 46.568114-16.46089 46.568114-45.757863 0-30.064579-17.313786-40.512554-48.359196-40.512554h-26.311837v86.270417h28.145563z m232.414124-142.860058c81.878003 0 136.036891 43.710913 136.036891 147.67892S556.231457 853.420826 477.935617 853.420826h-38.16709a42.644793 42.644793 0 0 1-42.644794-42.644793v-213.223967a42.644793 42.644793 0 0 1 42.644794-42.644794h34.542282z m-4.008611 240.729859c43.32711 0 73.988717-22.047358 73.988717-93.050939 0-71.046226-30.704251-90.705476-73.988717-90.705476h-8.699538v183.79906h8.699538zM692.481573 853.420826a32.282109 32.282109 0 0 1-32.282109-32.282108V597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h99.063855a29.680776 29.680776 0 1 1 0 59.404197h-77.144431v65.374469h61.749661a29.894 29.894 0 1 1 0 59.788h-61.749661v81.66478a32.282109 32.282109 0 0 1-32.282108 32.282108z" fill="#5f5f5f" p-id="3518"></path></svg>
+                    </a>
+                    <a id="export_pic" title="导出图片" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    <a id="export_markdown" title="导出markdown" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_doc" title="导出文档" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1689246982401" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="6825" width="16" height="16"><path d="M270.76864 608.32h180.8a31.68 31.68 0 0 0 0-62.976H270.76864a31.68 31.68 0 0 0 0 62.976zM271.34464 458.56h457.92a33.472 33.472 0 0 0 31.552-34.752 33.28 33.28 0 0 0-31.552-34.624H271.34464a34.816 34.816 0 0 0 0 69.376zM271.34464 293.504h457.92a33.344 33.344 0 0 0 31.552-34.688 33.216 33.216 0 0 0-31.552-34.624H271.34464a33.28 33.28 0 0 0-31.616 34.624 33.28 33.28 0 0 0 31.616 34.688z" p-id="6826" fill="#424242"></path><path d="M869.87264 0H153.77664A70.4 70.4 0 0 0 84.65664 70.912V953.6A69.952 69.952 0 0 0 153.77664 1024h370.048a32 32 0 0 0 0-63.68H147.12064V64h729.6v468.672a31.296 31.296 0 1 0 62.528 0V70.912A70.4 70.4 0 0 0 869.87264 0z" p-id="6827" fill="#424242"></path><path d="M482.16064 730.624h337.664L715.82464 625.216a28.864 28.864 0 0 1-7.936-28.736 29.184 29.184 0 0 1 20.608-21.184 29.632 29.632 0 0 1 29.12 8.128l174.784 177.216-174.784 176.96a29.184 29.184 0 0 1-49.728-13.312 29.248 29.248 0 0 1 8-28.8l103.936-105.344H482.16064a29.696 29.696 0 0 1-29.504-29.76 29.632 29.632 0 0 1 29.504-29.76z" p-id="6828" fill="#424242"></path></svg>
+                    </a>
+                </span>
+                <a  id="icon_more" title="更多" >
+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
+                </a>
+                <a  id="icon_less" class="display_none">
+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">前端学习路线</h2>
+                        <span id="post_page_title_date" class="date">2024.02.29</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><p><a href="/iblog/posts/annex/xmind/%E5%89%8D%E7%AB%AF%E7%9F%A5%E8%AF%86%E7%82%B9.xmind"><img alt="前端知识点" src="/iblog/posts/annex/images/essays/%E5%89%8D%E7%AB%AF%E7%9F%A5%E8%AF%86%E7%82%B9.png"></a></p>
+<h2 id="基础知识">基础知识</h2>
+<h3 id="网络知识">网络知识</h3>
+<ol>
+<li><a href="https://www.bilibili.com/video/BV1js411g7Fw/">HTTP</a></li>
+<li><a href="https://www.bilibili.com/video/BV1GW411j7Ts/">DNS</a></li>
+<li><a href="https://www.bilibili.com/video/BV1zA411x7Pj/">域名</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Rt411u7k4/">云服务</a></li>
+<li>网络安全
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1Up4y1i7PG/">HTTPS</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Kt411E76z/">CORS</a></li>
+<li><a href="https://www.bilibili.com/video/BV1kh411W7Vv/">网络渗透</a></li>
+<li><a href="https://www.bilibili.com/video/BV1ey4y1V7Jj/">OWASP</a></li>
+</ul>
+</li>
+</ol>
+<h3 id="htmlhttpswwwbilibilicomvideobv1p84y1p7z5"><a href="https://www.bilibili.com/video/BV1p84y1P7Z5/">HTML</a></h3>
+<h3 id="csshttpswwwbilibilicomvideobv1p84y1p7z5"><a href="https://www.bilibili.com/video/BV1p84y1P7Z5/">CSS</a></h3>
+<h3 id="javascripthttpswwwbilibilicomvideobv1yw411t7gx"><a href="https://www.bilibili.com/video/BV1YW411T7GX/">JavaScript</a></h3>
+<h3 id="jqueryhttpswwwbilibilicomvideobv1ts411e7ag"><a href="https://www.bilibili.com/video/BV1ts411E7ag/">JQuery</a></h3>
+<h3 id="ajaxhttpswwwbilibilicomvideobv1wc4y1b78y"><a href="https://www.bilibili.com/video/BV1WC4y1b78y/">Ajax</a></h3>
+<h3 id="es6-es11httpswwwbilibilicomvideobv1uk411h7on"><a href="https://www.bilibili.com/video/BV1uK411H7on/">ES6-ES11</a></h3>
+<h3 id="综合应用httpswwwbilibilicomvideobv1ra411x7rx"><a href="https://www.bilibili.com/video/BV1ra411X7RX/">综合应用</a></h3>
+<hr>
+<h2 id="工程化体系">工程化体系</h2>
+<h3 id="代码规范httpswwwbilibilicomvideobv19p4y147jz"><a href="https://www.bilibili.com/video/BV19P4y147Jz/">代码规范</a></h3>
+<h3 id="css预处理器">CSS预处理器</h3>
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1YW411T7vd/">Less</a></li>
+<li><a href="https://www.bilibili.com/video/BV1RJ4113717/">Sass</a></li>
+<li>PostCSS</li>
+</ul>
+<h3 id="nodehttpswwwbilibilicomvideobv1gm411w7ex"><a href="https://www.bilibili.com/video/BV1gM411W7ex/">Node</a></h3>
+<h3 id="promisehttpswwwbilibilicomvideobv1ga411x7z1"><a href="https://www.bilibili.com/video/BV1GA411x7z1/">Promise</a></h3>
+<h3 id="axioshttpswwwbilibilicomvideobv1wr4y1k7tq"><a href="https://www.bilibili.com/video/BV1wr4y1K7tq/">Axios</a></h3>
+<h3 id="工具">工具</h3>
+<ol>
+<li>包管理工具
+<ul>
+<li><a href="https://www.imooc.com/learn/766">Yarn</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Dv411W7XP/">Npm</a></li>
+</ul>
+</li>
+<li>打包工具
+<ul>
+<li><a href="https://www.bilibili.com/video/BV14T4y1z7sw/">Webpack</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Pa4y147Kf/">Parcel</a></li>
+</ul>
+</li>
+<li>代码格式化工具
+<ul>
+<li><a href="https://space.bilibili.com/390120104/search/video?keyword=ESLint">ESLint</a></li>
+<li><a href="https://www.bilibili.com/video/BV183411r7YK/">Prettier</a></li>
+</ul>
+</li>
+<li>调试工具
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1KM4y1G7EF/">Chrome</a></li>
+<li><a href="https://www.cnblogs.com/Christeen/p/6612697.html">IETest</a></li>
+<li><a href="https://www.bilibili.com/video/BV1r34y1d7Kz/">Postman</a></li>
+</ul>
+</li>
+<li>版本管理工具
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1FE411P7B3/">Git</a></li>
+<li><a href="https://www.bilibili.com/video/BV11E411x7Uv/">GitLab</a></li>
+<li><a href="https://www.bilibili.com/video/BV1yo4y1d7UK/">GitHub</a></li>
+</ul>
+</li>
+<li>部署发布工具
+<ul>
+<li><a href="https://www.bilibili.com/video/BV12y4y1M7jU/">Jenkins</a></li>
+<li><a href="https://www.bilibili.com/video/BV1u14y1o7DW/">CICD</a></li>
+</ul>
+</li>
+</ol>
+<h3 id="主流技术">主流技术</h3>
+<ul>
+<li><a href="https://www.bilibili.com/video/BV1Xy4y1v7S2/">TypeScript</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Zy4y1K7SH/">Vue</a></li>
+<li><a href="https://www.bilibili.com/video/BV1wy4y1D7JT/">React</a></li>
+<li><a href="https://www.bilibili.com/video/BV1ts411E7qg/">Angular</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Xh411V7b5/">综合应用</a></li>
+</ul>
+<hr>
+<h2 id="静态站点生成器">静态站点生成器</h2>
+<ul>
+<li><a href="https://www.bilibili.com/video/BV13441117KK/">Next</a></li>
+<li><a href="https://www.gatsbyjs.cn/">GatsbyJS</a></li>
+<li><a href="https://www.bilibili.com/video/BV1Xt41117Kg/">Nuxt</a></li>
+<li><a href="https://www.bilibili.com/video/BV1vb411m7NY/">Vuepress</a></li>
+<li><a href="https://www.bilibili.com/video/BV1x64y117PX/">Hugo</a></li>
+</ul>
+<hr>
+<h2 id="移动端">移动端</h2>
+<h3 id="微信小程序httpswwwbilibilicomvideobv12k411a7a2"><a href="https://www.bilibili.com/video/BV12K411A7A2/">微信小程序</a></h3>
+<h3 id="native-app">Native App</h3>
+<p>原生APP开发模式</p>
+<p>优点:</p>
+<ol>
+<li>可轻易调用手机所有硬件实现功能</li>
+<li>速度更快、性能高、整体用户体验最好</li>
+<li>质量安全性很高</li>
+</ol>
+<p>缺点：</p>
+<ol>
+<li>开发周期长及维护成本高(比如ios和android需2端开发2个app)</li>
+<li>学习成本高(ios必须会swift，android必须会Java)</li>
+</ol>
+<h4 id="安卓原生httpswwwbilibilicomvideobv19u4y1r7zv"><a href="https://www.bilibili.com/video/BV19U4y1R7zV/">安卓原生</a></h4>
+<h4 id="ios原生httpswwwbilibilicomvideobv1tt411a7xa"><a href="https://www.bilibili.com/video/BV1Tt411a7Xa/">IOS原生</a></h4>
+<h4 id="鸿蒙原生httpswwwbilibilicomvideobv1ti4y1s79b"><a href="https://www.bilibili.com/video/BV1Ti4y1s79B/">鸿蒙原生</a></h4>
+<h3 id="web-app">Web App</h3>
+<p>HTML5 APP 框架开发模式，Web App即我们通常所说的H5 app，主要通过HTML，CSS，JS构建页面，然后发布到服务器，用户通过手机网络访问这些页面。类似微信公众号等。</p>
+<p>优点:</p>
+<ol>
+<li>项目独立，维护更容易，兼容多平台</li>
+<li>开发周期短，学习成本低</li>
+<li>更新发版更容易</li>
+</ol>
+<p>缺点：</p>
+<ol>
+<li>体验不好，对设备和网络要求高，经常卡顿，性能差</li>
+<li>无法调用系统硬件</li>
+</ol>
+<h3 id="hybird-app">Hybird App</h3>
+<p>混合模式移动应用，介于Web App、Native App这两者之间的app， Hybrid App主要以JS+Native两者相互调用为主，从开发层面现“一次开发，多处运行”的机制，成为真正适合跨平台的开发，是目前乃至未来发展的趋势。</p>
+<p>优点:</p>
+<ol>
+<li>维护容易，能调用部分系统硬件，兼容多平台</li>
+<li>开发周期短，学习成本低</li>
+</ol>
+<p>缺点：</p>
+<ol>
+<li>可能需要会原生开发以支持更多的硬件调用</li>
+<li>性能跟原生还是有差距，对设备有一定要求</li>
+</ol>
+<h4 id="uni-apphttpswwwbilibilicomvideobv1bj411w7px"><a href="https://www.bilibili.com/video/BV1BJ411W7pX/">Uni-App</a></h4>
+<h4 id="taro">Taro</h4>
+<h4 id="react-nativehttpswwwbilibilicomvideobv1pt4y1n7bd"><a href="https://www.bilibili.com/video/BV1Pt4y1n7bD/">React Native</a></h4>
+<h4 id="flutter">Flutter</h4>
+<ul>
+<li><a href="https://www.bilibili.com/video/BV15t411U7yf/">基础</a></li>
+<li><a href="https://www.bilibili.com/video/BV1kt411B7mu/">实战</a></li>
+</ul>
+<hr>
+<h2 id="性能优化和监控">性能优化和监控</h2>
+<h3 id="性能优化概览httpswwwbilibilicomvideobv1kr4y1l7tk"><a href="https://www.bilibili.com/video/BV1KR4y1L7TK/">性能优化概览</a></h3>
+<h3 id="浏览器及工作方式httpswwwbilibilicomvideobv1x54y1b7re"><a href="https://www.bilibili.com/video/BV1x54y1B7RE/">浏览器及工作方式</a></h3>
+<h3 id="seohttpswwwbilibilicomvideobv1fe411j7ya"><a href="https://www.bilibili.com/video/BV1fE411J7ya/">SEO</a></h3>
+<h3 id="资源管理">资源管理</h3>
+<ul>
+<li>延迟加载</li>
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+<li>缓存复用</li>
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diff --git a/docs/posts/intro/nginx-start/index.html b/docs/posts/intro/nginx-start/index.html
new file mode 100644
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+<html lang="zh" >
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+                <a  id="icon_more" title="更多" >
+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
+                </a>
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+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Nginx入门</h2>
+                        <span id="post_page_title_date" class="date">2021.03.04</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="nginx介绍">Nginx介绍</h2>
+<blockquote>
+<p>Nginx (&ldquo;engine x&rdquo;)是一个高性能的HTTP和反向代理服务器，特点是占有内存少，并发能力强，事实上Nginx的并发能力确实在同类型的网页服务器中表现较好.
+Nginx专为性能优化而开发，性能是其最重要的考量，实现上非常注重效率，能经受高负载的考验，有报告表明能支持高达50000个并发连接数。</p>
+</blockquote>
+<h3 id="与apahche区别联系">与apahche区别联系</h3>
+<p>Nginx 启动特别容易, 并且几乎可以做到7*24不间断运行，即使运行数个月也不需要重新启动. 你还能够不间断服务的情况下进行软件版本的升级。</p>
+<p>Nginx 静态处理性能比 Apache 高 3倍以上，Apache 对 PHP 支持比较简单， Nginx 需要配合其他后端来使用 ,Apache 的组件比 Nginx 多。</p>
+<p>Nginx的优势是处理静态请求，cpu内存使用率低，apache适合处理动态请求， 所以现在一般前端用nginx作为反向代理抗住压力，apache作为后端处理动态请求。</p>
+<p>apache是同步多进程模型，一个连接对应一个进程；nginx是异步的，多个连接（万级别）可以对应一个进程。所以在高连接并发的情况下，Nginx是Apache服务器不错的替代品。</p>
+<h3 id="反向代理">反向代理</h3>
+<p><img alt="nginx反向代理" src="/iblog/posts/annex/images/application/nginx%E5%8F%8D%E5%90%91%E4%BB%A3%E7%90%86.jpg"></p>
+<p><strong>正向代理</strong>：
+在客户端(浏览器)配置代理服务器，通过代理服务器进行互联网访问. 例如：在国内想通过网络翻墙，直接访问外网，访问失败， 这个时候就要通过代理服务器，我们访问代理服务器，让代理服务器访问外网，这样就能顺利翻墙。</p>
+<p><strong>反向代理</strong>：
+其实客户端对代理是无感知的，因为客户端不需要任何配置就可以访问，我们只需要将请求发送到反向代理服务器，由反向代理服务器去选择目标服务器获取数据后,在返回给客户端，此时反向代理服务器和目标服务器对外就是一个服务器，暴露的是代理服务器地址，隐藏了真实服务器IP地址。</p>
+<h3 id="负载均衡">负载均衡</h3>
+<p>由于访问量的增加，单个服务器承受不了并发，我们增加服务器的数量，然后将请求分发到各个服务器上, 将原先请求集中到单个服务器上的情况改为将请求分发到多个服务器上,将负载分发到不同的服务器，也就是我们所说的负载均衡。
+<img alt="nginx负载均衡" src="/iblog/posts/annex/images/application/nginx%E8%B4%9F%E8%BD%BD%E5%9D%87%E8%A1%A1.png"></p>
+<h3 id="动静分离">动静分离</h3>
+<p>为了加快网站的解析速度，降低原来单个服务器的压力，可以把动态页面和静态页面由不同的服务器来解析。</p>
+<p><img alt="nginx动静分离" src="/iblog/posts/annex/images/application/nginx%E5%8A%A8%E9%9D%99%E5%88%86%E7%A6%BB.jpg"></p>
+<h2 id="docker安装nginx">Docker安装nginx</h2>
+<p>如未安装docker移步<a href="/iblog/posts/springboot/springboot-docker">安装 docker</a></p>
+<h3 id="拉取镜像">拉取镜像</h3>
+<p>搜寻 nginx 镜像</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">docker search nginx
+</span></span></code></pre></div><p>拉取 nginx 镜像</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">docker pull nginx
+</span></span></code></pre></div><p>查看本地已经安装的镜像，是否有我们刚拉取的 nginx 镜像</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">docker images
+</span></span></code></pre></div><h3 id="配置nginx">配置nginx</h3>
+<p>在本地创建对应 docekr 上 nginx 的配置文件和目录，方便管理。</p>
+<p><code>~/Documents/config/nginx</code>是我本地存放 nginx 的配置路径。路径哪里方便放哪里。</p>
+<p>在上述路径下创建 <code>conf.d</code>、<code>www</code> 文件夹</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">mkdir conf.d www
+</span></span></code></pre></div><p>创建 nginx 临时容器，用于拷贝所需配置文件</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">docker run --name tmp-nginx-container -d nginx
+</span></span></code></pre></div><p>拷贝 nginx 配置文件</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">docker cp tmp-nginx-container:/etc/nginx/nginx.conf ~/Documents/config/nginx/nginx.conf
+</span></span></code></pre></div><p><img alt="nginx存放路径" src="/iblog/posts/annex/images/application/nginx%E5%AE%89%E8%A3%85%E8%B7%AF%E5%BE%84.jpg"></p>
+<p>拷贝站点配置文件</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">docker cp tmp-nginx-container:/etc/nginx/conf.d/default.conf ~/Documents/config/nginx/conf.d/default.conf
+</span></span></code></pre></div><p>删除 nginx 临时容器</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">docker rm -f tmp-nginx-container
+</span></span></code></pre></div><p>创建 nginx 容器，并映射 nginx 配置文件、站点配置文件目录和网站根目录；-v 是挂载的意思,将宿主机的文件映射到容器中</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">docker run --name nginx -p 80:80 -v ~/Documents/config/nginx/nginx.conf:/etc/nginx/nginx.conf -v ~/Documents/config/nginx/conf.d:/etc/nginx/conf.d -v ~/Documents/config/nginx/www:/www -d nginx
+</span></span></code></pre></div><h3 id="测试nginx">测试nginx</h3>
+<p>拷贝 <code>default.conf</code> 为 <code>test.conf</code> ，并修改<code>test.conf</code> 中 <code>server_name</code>文件</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="n">server</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="n">listen</span>       <span class="mi">80</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="n">listen</span>  <span class="p">[::]:</span><span class="mi">80</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="n">server_name</span>  <span class="n">www</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">com</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#charset koi8-r;</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#access_log  /var/log/nginx/host.access.log  main;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">location</span> <span class="o">/</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">root</span>   <span class="o">/</span><span class="n">www</span><span class="o">/</span><span class="n">test</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">index</span>  <span class="n">index</span><span class="o">.</span><span class="n">html</span> <span class="n">index</span><span class="o">.</span><span class="n">htm</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#error_page  404              /404.html;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1"># redirect server error pages to the static page /50x.html</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#</span>
+</span></span><span class="line"><span class="cl">    <span class="n">error_page</span>   <span class="mi">500</span> <span class="mi">502</span> <span class="mi">503</span> <span class="mi">504</span>  <span class="o">/</span><span class="mi">50</span><span class="n">x</span><span class="o">.</span><span class="n">html</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="n">location</span> <span class="o">=</span> <span class="o">/</span><span class="mi">50</span><span class="n">x</span><span class="o">.</span><span class="n">html</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="n">root</span>   <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">share</span><span class="o">/</span><span class="n">nginx</span><span class="o">/</span><span class="n">html</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="c1"># ...</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>修改本地 <code>/etc/hosts</code> 文件；浏览器解析域名会先从 hosts 文件进行解析，如果没有的话，会从网络上进行解析。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">127.0.0.1 www.test.com
+</span></span></code></pre></div><p><img alt="nginx测试修改hosts文件" src="/iblog/posts/annex/images/application/nginx%E6%B5%8B%E8%AF%95%E4%BF%AE%E6%94%B9hosts%E6%96%87%E4%BB%B6.jpg"></p>
+<p>在本地 <code>~/Documents/config/nginx/www</code> 下新建 test 目录，并编写一个 <code>index.html</code> 测试文件
+<img alt="nginx本地路径" src="/iblog/posts/annex/images/application/nginx%E6%9C%AC%E5%9C%B0%E8%B7%AF%E5%BE%84.jpg"></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">&lt;!DOCTYPE html&gt;
+</span></span><span class="line"><span class="cl">&lt;html lang=&#34;en&#34;&gt;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">&lt;head&gt;
+</span></span><span class="line"><span class="cl">    &lt;meta charset=&#34;UTF-8&#34;&gt;
+</span></span><span class="line"><span class="cl">    &lt;meta name=&#34;viewport&#34; content=&#34;width=device-width, initial-scale=1.0&#34;&gt;
+</span></span><span class="line"><span class="cl">    &lt;meta http-equiv=&#34;X-UA-Compatible&#34; content=&#34;ie=edge&#34;&gt;
+</span></span><span class="line"><span class="cl">    &lt;title&gt;Document&lt;/title&gt;
+</span></span><span class="line"><span class="cl">&lt;/head&gt;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">&lt;body&gt;
+</span></span><span class="line"><span class="cl">    &lt;h1&gt;测试Nginx&lt;/h1&gt;
+</span></span><span class="line"><span class="cl">&lt;/body&gt;
+</span></span><span class="line"><span class="cl"> 
+</span></span><span class="line"><span class="cl">&lt;/html&gt;
+</span></span></code></pre></div><p>重启 nginx</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">docker restart nginx
+</span></span></code></pre></div><p>浏览器访问<a href="http://www.test.com">http://www.test.com</a>
+<img alt="测试nginx成功" src="/iblog/posts/annex/images/application/%E6%B5%8B%E8%AF%95nginx%E6%88%90%E5%8A%9F.jpg"></p>
+<h3 id="nginx配置详解">Nginx配置详解</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="c1">######Nginx配置文件nginx.conf中文详解#####</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="c1">#定义Nginx运行的用户和用户组</span>
+</span></span><span class="line"><span class="cl"><span class="n">user</span> <span class="n">www</span> <span class="n">www</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="c1">#nginx进程数，建议设置为等于CPU总核心数。</span>
+</span></span><span class="line"><span class="cl"><span class="n">worker_processes</span> <span class="mi">8</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="c1">#全局错误日志定义类型，[ debug | info | notice | warn | error | crit ]</span>
+</span></span><span class="line"><span class="cl"><span class="n">error_log</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">nginx</span><span class="o">/</span><span class="n">logs</span><span class="o">/</span><span class="n">error</span><span class="o">.</span><span class="n">log</span> <span class="n">info</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="c1">#进程pid文件</span>
+</span></span><span class="line"><span class="cl"><span class="n">pid</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">nginx</span><span class="o">/</span><span class="n">logs</span><span class="o">/</span><span class="n">nginx</span><span class="o">.</span><span class="n">pid</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="c1">#指定进程可以打开的最大描述符：数目</span>
+</span></span><span class="line"><span class="cl"><span class="c1">#工作模式与连接数上限</span>
+</span></span><span class="line"><span class="cl"><span class="c1">#这个指令是指当一个nginx进程打开的最多文件描述符数目，理论值应该是最多打开文件数（ulimit -n）与nginx进程数相除，但是nginx分配请求并不是那么均匀，所以最好与ulimit -n 的值保持一致。</span>
+</span></span><span class="line"><span class="cl"><span class="c1">#现在在linux 2.6内核下开启文件打开数为65535，worker_rlimit_nofile就相应应该填写65535。</span>
+</span></span><span class="line"><span class="cl"><span class="c1">#这是因为nginx调度时分配请求到进程并不是那么的均衡，所以假如填写10240，总并发量达到3-4万时就有进程可能超过10240了，这时会返回502错误。</span>
+</span></span><span class="line"><span class="cl"><span class="n">worker_rlimit_nofile</span> <span class="mi">65535</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="n">events</span>
+</span></span><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#参考事件模型，use [ kqueue | rtsig | epoll | /dev/poll | select | poll ]; epoll模型</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#是Linux 2.6以上版本内核中的高性能网络I/O模型，linux建议epoll，如果跑在FreeBSD上面，就用kqueue模型。</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#补充说明：</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#与apache相类，nginx针对不同的操作系统，有不同的事件模型</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#A）标准事件模型</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#Select、poll属于标准事件模型，如果当前系统不存在更有效的方法，nginx会选择select或poll</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#B）高效事件模型</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#Kqueue：使用于FreeBSD 4.1+, OpenBSD 2.9+, NetBSD 2.0 和 MacOS X.使用双处理器的MacOS X系统使用kqueue可能会造成内核崩溃。</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#Epoll：使用于Linux内核2.6版本及以后的系统。</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#/dev/poll：使用于Solaris 7 11/99+，HP/UX 11.22+ (eventport)，IRIX 6.5.15+ 和 Tru64 UNIX 5.1A+。</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#Eventport：使用于Solaris 10。 为了防止出现内核崩溃的问题， 有必要安装安全补丁。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">use</span> <span class="n">epoll</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#单个进程最大连接数（最大连接数=连接数*进程数）</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#根据硬件调整，和前面工作进程配合起来用，尽量大，但是别把cpu跑到100%就行。每个进程允许的最多连接数，理论上每台nginx服务器的最大连接数为。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">worker_connections</span> <span class="mi">65535</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#keepalive超时时间。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">keepalive_timeout</span> <span class="mi">60</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#客户端请求头部的缓冲区大小。这个可以根据你的系统分页大小来设置，一般一个请求头的大小不会超过1k，不过由于一般系统分页都要大于1k，所以这里设置为分页大小。</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#分页大小可以用命令getconf PAGESIZE 取得。</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#[root@web001 ~]# getconf PAGESIZE</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#4096</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#但也有client_header_buffer_size超过4k的情况，但是client_header_buffer_size该值必须设置为“系统分页大小”的整倍数。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">client_header_buffer_size</span> <span class="mi">4</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#这个将为打开文件指定缓存，默认是没有启用的，max指定缓存数量，建议和打开文件数一致，inactive是指经过多长时间文件没被请求后删除缓存。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">open_file_cache</span> <span class="nb">max</span><span class="o">=</span><span class="mi">65535</span> <span class="n">inactive</span><span class="o">=</span><span class="mi">60</span><span class="n">s</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#这个是指多长时间检查一次缓存的有效信息。</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#语法:open_file_cache_valid time 默认值:open_file_cache_valid 60 使用字段:http, server, location 这个指令指定了何时需要检查open_file_cache中缓存项目的有效信息.</span>
+</span></span><span class="line"><span class="cl">    <span class="n">open_file_cache_valid</span> <span class="mi">80</span><span class="n">s</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#open_file_cache指令中的inactive参数时间内文件的最少使用次数，如果超过这个数字，文件描述符一直是在缓存中打开的，如上例，如果有一个文件在inactive时间内一次没被使用，它将被移除。</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#语法:open_file_cache_min_uses number 默认值:open_file_cache_min_uses 1 使用字段:http, server, location  这个指令指定了在open_file_cache指令无效的参数中一定的时间范围内可以使用的最小文件数,如果使用更大的值,文件描述符在cache中总是打开状态.</span>
+</span></span><span class="line"><span class="cl">    <span class="n">open_file_cache_min_uses</span> <span class="mi">1</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#语法:open_file_cache_errors on | off 默认值:open_file_cache_errors off 使用字段:http, server, location 这个指令指定是否在搜索一个文件是记录cache错误.</span>
+</span></span><span class="line"><span class="cl">    <span class="n">open_file_cache_errors</span> <span class="n">on</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="c1">#设定http服务器，利用它的反向代理功能提供负载均衡支持</span>
+</span></span><span class="line"><span class="cl"><span class="n">http</span>
+</span></span><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#文件扩展名与文件类型映射表</span>
+</span></span><span class="line"><span class="cl">    <span class="n">include</span> <span class="n">mime</span><span class="o">.</span><span class="n">types</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#默认文件类型</span>
+</span></span><span class="line"><span class="cl">    <span class="n">default_type</span> <span class="n">application</span><span class="o">/</span><span class="n">octet</span><span class="o">-</span><span class="n">stream</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#默认编码</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#charset utf-8;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#服务器名字的hash表大小</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#保存服务器名字的hash表是由指令server_names_hash_max_size 和server_names_hash_bucket_size所控制的。参数hash bucket size总是等于hash表的大小，并且是一路处理器缓存大小的倍数。在减少了在内存中的存取次数后，使在处理器中加速查找hash表键值成为可能。如果hash bucket size等于一路处理器缓存的大小，那么在查找键的时候，最坏的情况下在内存中查找的次数为2。第一次是确定存储单元的地址，第二次是在存储单元中查找键 值。因此，如果Nginx给出需要增大hash max size 或 hash bucket size的提示，那么首要的是增大前一个参数的大小.</span>
+</span></span><span class="line"><span class="cl">    <span class="n">server_names_hash_bucket_size</span> <span class="mi">128</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#客户端请求头部的缓冲区大小。这个可以根据你的系统分页大小来设置，一般一个请求的头部大小不会超过1k，不过由于一般系统分页都要大于1k，所以这里设置为分页大小。分页大小可以用命令getconf PAGESIZE取得。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">client_header_buffer_size</span> <span class="mi">32</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#客户请求头缓冲大小。nginx默认会用client_header_buffer_size这个buffer来读取header值，如果header过大，它会使用large_client_header_buffers来读取。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">large_client_header_buffers</span> <span class="mi">4</span> <span class="mi">64</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#设定通过nginx上传文件的大小</span>
+</span></span><span class="line"><span class="cl">    <span class="n">client_max_body_size</span> <span class="mi">8</span><span class="n">m</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#开启高效文件传输模式，sendfile指令指定nginx是否调用sendfile函数来输出文件，对于普通应用设为 on，如果用来进行下载等应用磁盘IO重负载应用，可设置为off，以平衡磁盘与网络I/O处理速度，降低系统的负载。注意：如果图片显示不正常把这个改成off。</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#sendfile指令指定 nginx 是否调用sendfile 函数（zero copy 方式）来输出文件，对于普通应用，必须设为on。如果用来进行下载等应用磁盘IO重负载应用，可设置为off，以平衡磁盘与网络IO处理速度，降低系统uptime。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">sendfile</span> <span class="n">on</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#开启目录列表访问，合适下载服务器，默认关闭。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">autoindex</span> <span class="n">on</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#此选项允许或禁止使用socke的TCP_CORK的选项，此选项仅在使用sendfile的时候使用</span>
+</span></span><span class="line"><span class="cl">    <span class="n">tcp_nopush</span> <span class="n">on</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="n">tcp_nodelay</span> <span class="n">on</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#长连接超时时间，单位是秒</span>
+</span></span><span class="line"><span class="cl">    <span class="n">keepalive_timeout</span> <span class="mi">120</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#FastCGI相关参数是为了改善网站的性能：减少资源占用，提高访问速度。下面参数看字面意思都能理解。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">fastcgi_connect_timeout</span> <span class="mi">300</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="n">fastcgi_send_timeout</span> <span class="mi">300</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="n">fastcgi_read_timeout</span> <span class="mi">300</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="n">fastcgi_buffer_size</span> <span class="mi">64</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="n">fastcgi_buffers</span> <span class="mi">4</span> <span class="mi">64</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="n">fastcgi_busy_buffers_size</span> <span class="mi">128</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">    <span class="n">fastcgi_temp_file_write_size</span> <span class="mi">128</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#gzip模块设置</span>
+</span></span><span class="line"><span class="cl">    <span class="n">gzip</span> <span class="n">on</span><span class="p">;</span> <span class="c1">#开启gzip压缩输出</span>
+</span></span><span class="line"><span class="cl">    <span class="n">gzip_min_length</span> <span class="mi">1</span><span class="n">k</span><span class="p">;</span>    <span class="c1">#最小压缩文件大小</span>
+</span></span><span class="line"><span class="cl">    <span class="n">gzip_buffers</span> <span class="mi">4</span> <span class="mi">16</span><span class="n">k</span><span class="p">;</span>    <span class="c1">#压缩缓冲区</span>
+</span></span><span class="line"><span class="cl">    <span class="n">gzip_http_version</span> <span class="mf">1.0</span><span class="p">;</span>    <span class="c1">#压缩版本（默认1.1，前端如果是squid2.5请使用1.0）</span>
+</span></span><span class="line"><span class="cl">    <span class="n">gzip_comp_level</span> <span class="mi">2</span><span class="p">;</span>    <span class="c1">#压缩等级</span>
+</span></span><span class="line"><span class="cl">    <span class="n">gzip_types</span> <span class="n">text</span><span class="o">/</span><span class="n">plain</span> <span class="n">application</span><span class="o">/</span><span class="n">x</span><span class="o">-</span><span class="n">javascript</span> <span class="n">text</span><span class="o">/</span><span class="n">css</span> <span class="n">application</span><span class="o">/</span><span class="n">xml</span><span class="p">;</span>    <span class="c1">#压缩类型，默认就已经包含textml，所以下面就不用再写了，写上去也不会有问题，但是会有一个warn。</span>
+</span></span><span class="line"><span class="cl">    <span class="n">gzip_vary</span> <span class="n">on</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#开启限制IP连接数的时候需要使用</span>
+</span></span><span class="line"><span class="cl">    <span class="c1">#limit_zone crawler $binary_remote_addr 10m;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#负载均衡配置</span>
+</span></span><span class="line"><span class="cl">    <span class="n">upstream</span> <span class="n">piao</span><span class="o">.</span><span class="n">jd</span><span class="o">.</span><span class="n">com</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#upstream的负载均衡，weight是权重，可以根据机器配置定义权重。weigth参数表示权值，权值越高被分配到的几率越大。</span>
+</span></span><span class="line"><span class="cl">        <span class="n">server</span> <span class="mf">192.168</span><span class="o">.</span><span class="mf">80.121</span><span class="p">:</span><span class="mi">80</span> <span class="n">weight</span><span class="o">=</span><span class="mi">3</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">server</span> <span class="mf">192.168</span><span class="o">.</span><span class="mf">80.122</span><span class="p">:</span><span class="mi">80</span> <span class="n">weight</span><span class="o">=</span><span class="mi">2</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">server</span> <span class="mf">192.168</span><span class="o">.</span><span class="mf">80.123</span><span class="p">:</span><span class="mi">80</span> <span class="n">weight</span><span class="o">=</span><span class="mi">3</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#nginx的upstream目前支持4种方式的分配</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#1、轮询（默认）</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#每个请求按时间顺序逐一分配到不同的后端服务器，如果后端服务器down掉，能自动剔除。</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#2、weight</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#指定轮询几率，weight和访问比率成正比，用于后端服务器性能不均的情况。</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#例如：</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#upstream bakend {</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server 192.168.0.14 weight=10;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server 192.168.0.15 weight=10;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#}</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#2、ip_hash</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#每个请求按访问ip的hash结果分配，这样每个访客固定访问一个后端服务器，可以解决session的问题。</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#例如：</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#upstream bakend {</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    ip_hash;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server 192.168.0.14:88;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server 192.168.0.15:80;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#}</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#3、fair（第三方）</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#按后端服务器的响应时间来分配请求，响应时间短的优先分配。</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#upstream backend {</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server server1;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server server2;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    fair;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#}</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#4、url_hash（第三方）</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#按访问url的hash结果来分配请求，使每个url定向到同一个后端服务器，后端服务器为缓存时比较有效。</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#例：在upstream中加入hash语句，server语句中不能写入weight等其他的参数，hash_method是使用的hash算法</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#upstream backend {</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server squid1:3128;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server squid2:3128;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    hash $request_uri;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    hash_method crc32;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#tips:</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#upstream bakend{#定义负载均衡设备的Ip及设备状态}{</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    ip_hash;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server 127.0.0.1:9090 down;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server 127.0.0.1:8080 weight=2;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server 127.0.0.1:6060;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#    server 127.0.0.1:7070 backup;</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#}</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#在需要使用负载均衡的server中增加 proxy_pass http://bakend/;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#每个设备的状态设置为:</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#1.down表示单前的server暂时不参与负载</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#2.weight为weight越大，负载的权重就越大。</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#3.max_fails：允许请求失败的次数默认为1.当超过最大次数时，返回proxy_next_upstream模块定义的错误</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#4.fail_timeout:max_fails次失败后，暂停的时间。</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#5.backup： 其它所有的非backup机器down或者忙的时候，请求backup机器。所以这台机器压力会最轻。</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#nginx支持同时设置多组的负载均衡，用来给不用的server来使用。</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#client_body_in_file_only设置为On 可以讲client post过来的数据记录到文件中用来做debug</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#client_body_temp_path设置记录文件的目录 可以设置最多3层目录</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#location对URL进行匹配.可以进行重定向或者进行新的代理 负载均衡</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="c1">#虚拟主机的配置</span>
+</span></span><span class="line"><span class="cl">    <span class="n">server</span>
+</span></span><span class="line"><span class="cl">    <span class="p">{</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#监听端口</span>
+</span></span><span class="line"><span class="cl">        <span class="n">listen</span> <span class="mi">80</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#域名可以有多个，用空格隔开</span>
+</span></span><span class="line"><span class="cl">        <span class="n">server_name</span> <span class="n">www</span><span class="o">.</span><span class="n">jd</span><span class="o">.</span><span class="n">com</span> <span class="n">jd</span><span class="o">.</span><span class="n">com</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">index</span> <span class="n">index</span><span class="o">.</span><span class="n">html</span> <span class="n">index</span><span class="o">.</span><span class="n">htm</span> <span class="n">index</span><span class="o">.</span><span class="n">php</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">root</span> <span class="o">/</span><span class="n">data</span><span class="o">/</span><span class="n">www</span><span class="o">/</span><span class="n">jd</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#fastcgi解析php</span>
+</span></span><span class="line"><span class="cl">        <span class="n">location</span> <span class="o">~</span> <span class="o">.*.</span><span class="p">(</span><span class="n">php</span><span class="o">|</span><span class="n">php5</span><span class="p">)</span><span class="err">?</span><span class="o">$</span>
+</span></span><span class="line"><span class="cl">        <span class="p">{</span>
+</span></span><span class="line"><span class="cl"><span class="c1">#此处有两种方式去和php-fpm交互,一种是9000端口,另一种是使用socket连接</span>
+</span></span><span class="line"><span class="cl">            <span class="n">fastcgi_pass</span> <span class="mf">127.0</span><span class="o">.</span><span class="mf">0.1</span><span class="p">:</span><span class="mi">9000</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">fastcgi_index</span> <span class="n">index</span><span class="o">.</span><span class="n">php</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">include</span> <span class="n">fastcgi</span><span class="o">.</span><span class="n">conf</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#图片缓存时间设置</span>
+</span></span><span class="line"><span class="cl">        <span class="n">location</span> <span class="o">~</span> <span class="o">.*.</span><span class="p">(</span><span class="n">gif</span><span class="o">|</span><span class="n">jpg</span><span class="o">|</span><span class="n">jpeg</span><span class="o">|</span><span class="n">png</span><span class="o">|</span><span class="n">bmp</span><span class="o">|</span><span class="n">swf</span><span class="p">)</span><span class="o">$</span>
+</span></span><span class="line"><span class="cl">        <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">expires</span> <span class="mi">10</span><span class="n">d</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#JS和CSS缓存时间设置</span>
+</span></span><span class="line"><span class="cl">        <span class="n">location</span> <span class="o">~</span> <span class="o">.*.</span><span class="p">(</span><span class="n">js</span><span class="o">|</span><span class="n">css</span><span class="p">)</span><span class="err">?</span><span class="o">$</span>
+</span></span><span class="line"><span class="cl">        <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">expires</span> <span class="mi">1</span><span class="n">h</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#日志格式设定</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#$remote_addr与$http_x_forwarded_for用以记录客户端的ip地址；</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#$remote_user：用来记录客户端用户名称；</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#$time_local： 用来记录访问时间与时区；</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#$request： 用来记录请求的url与http协议；</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#$status： 用来记录请求状态；成功是200，</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#$body_bytes_sent ：记录发送给客户端文件主体内容大小；</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#$http_referer：用来记录从那个页面链接访问过来的；</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#$http_user_agent：记录客户浏览器的相关信息；</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#通常web服务器放在反向代理的后面，这样就不能获取到客户的IP地址了，通过$remote_add拿到的IP地址是反向代理服务器的iP地址。反向代理服务器在转发请求的http头信息中，可以增加x_forwarded_for信息，用以记录原有客户端的IP地址和原来客户端的请求的服务器地址。</span>
+</span></span><span class="line"><span class="cl">        <span class="n">log_format</span> <span class="n">access</span> <span class="s1">&#39;$remote_addr - $remote_user [$time_local] &#34;$request&#34; &#39;</span>
+</span></span><span class="line"><span class="cl">        <span class="s1">&#39;$status $body_bytes_sent &#34;$http_referer&#34; &#39;</span>
+</span></span><span class="line"><span class="cl">        <span class="s1">&#39;&#34;$http_user_agent&#34; $http_x_forwarded_for&#39;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#定义本虚拟主机的访问日志</span>
+</span></span><span class="line"><span class="cl">        <span class="n">access_log</span>  <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">nginx</span><span class="o">/</span><span class="n">logs</span><span class="o">/</span><span class="n">host</span><span class="o">.</span><span class="n">access</span><span class="o">.</span><span class="n">log</span>  <span class="n">main</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="n">access_log</span>  <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">nginx</span><span class="o">/</span><span class="n">logs</span><span class="o">/</span><span class="n">host</span><span class="o">.</span><span class="n">access</span><span class="o">.</span><span class="mf">404.</span><span class="n">log</span>  <span class="n">log404</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#对 &#34;/&#34; 启用反向代理</span>
+</span></span><span class="line"><span class="cl">        <span class="n">location</span> <span class="o">/</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_pass</span> <span class="n">http</span><span class="p">:</span><span class="o">//</span><span class="mf">127.0</span><span class="o">.</span><span class="mf">0.1</span><span class="p">:</span><span class="mi">88</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_redirect</span> <span class="n">off</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_set_header</span> <span class="n">X</span><span class="o">-</span><span class="n">Real</span><span class="o">-</span><span class="ne">IP</span> <span class="o">$</span><span class="n">remote_addr</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#后端的Web服务器可以通过X-Forwarded-For获取用户真实IP</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_set_header</span> <span class="n">X</span><span class="o">-</span><span class="n">Forwarded</span><span class="o">-</span><span class="n">For</span> <span class="o">$</span><span class="n">proxy_add_x_forwarded_for</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#以下是一些反向代理的配置，可选。</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_set_header</span> <span class="n">Host</span> <span class="o">$</span><span class="n">host</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#允许客户端请求的最大单文件字节数</span>
+</span></span><span class="line"><span class="cl">            <span class="n">client_max_body_size</span> <span class="mi">10</span><span class="n">m</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#缓冲区代理缓冲用户端请求的最大字节数，</span>
+</span></span><span class="line"><span class="cl">            <span class="c1">#如果把它设置为比较大的数值，例如256k，那么，无论使用firefox还是IE浏览器，来提交任意小于256k的图片，都很正常。如果注释该指令，使用默认的client_body_buffer_size设置，也就是操作系统页面大小的两倍，8k或者16k，问题就出现了。</span>
+</span></span><span class="line"><span class="cl">            <span class="c1">#无论使用firefox4.0还是IE8.0，提交一个比较大，200k左右的图片，都返回500 Internal Server Error错误</span>
+</span></span><span class="line"><span class="cl">            <span class="n">client_body_buffer_size</span> <span class="mi">128</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#表示使nginx阻止HTTP应答代码为400或者更高的应答。</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_intercept_errors</span> <span class="n">on</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#后端服务器连接的超时时间_发起握手等候响应超时时间</span>
+</span></span><span class="line"><span class="cl">            <span class="c1">#nginx跟后端服务器连接超时时间(代理连接超时)</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_connect_timeout</span> <span class="mi">90</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#后端服务器数据回传时间(代理发送超时)</span>
+</span></span><span class="line"><span class="cl">            <span class="c1">#后端服务器数据回传时间_就是在规定时间之内后端服务器必须传完所有的数据</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_send_timeout</span> <span class="mi">90</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#连接成功后，后端服务器响应时间(代理接收超时)</span>
+</span></span><span class="line"><span class="cl">            <span class="c1">#连接成功后_等候后端服务器响应时间_其实已经进入后端的排队之中等候处理（也可以说是后端服务器处理请求的时间）</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_read_timeout</span> <span class="mi">90</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#设置代理服务器（nginx）保存用户头信息的缓冲区大小</span>
+</span></span><span class="line"><span class="cl">            <span class="c1">#设置从被代理服务器读取的第一部分应答的缓冲区大小，通常情况下这部分应答中包含一个小的应答头，默认情况下这个值的大小为指令proxy_buffers中指定的一个缓冲区的大小，不过可以将其设置为更小</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_buffer_size</span> <span class="mi">4</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#proxy_buffers缓冲区，网页平均在32k以下的设置</span>
+</span></span><span class="line"><span class="cl">            <span class="c1">#设置用于读取应答（来自被代理服务器）的缓冲区数目和大小，默认情况也为分页大小，根据操作系统的不同可能是4k或者8k</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_buffers</span> <span class="mi">4</span> <span class="mi">32</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#高负荷下缓冲大小（proxy_buffers*2）</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_busy_buffers_size</span> <span class="mi">64</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">            <span class="c1">#设置在写入proxy_temp_path时数据的大小，预防一个工作进程在传递文件时阻塞太长</span>
+</span></span><span class="line"><span class="cl">            <span class="c1">#设定缓存文件夹大小，大于这个值，将从upstream服务器传</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_temp_file_write_size</span> <span class="mi">64</span><span class="n">k</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#设定查看Nginx状态的地址</span>
+</span></span><span class="line"><span class="cl">        <span class="n">location</span> <span class="o">/</span><span class="n">NginxStatus</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">stub_status</span> <span class="n">on</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">access_log</span> <span class="n">on</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">auth_basic</span> <span class="s2">&#34;NginxStatus&#34;</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">auth_basic_user_file</span> <span class="n">confpasswd</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="c1">#htpasswd文件的内容可以用apache提供的htpasswd工具来产生。</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#本地动静分离反向代理配置</span>
+</span></span><span class="line"><span class="cl">        <span class="c1">#所有jsp的页面均交由tomcat或resin处理</span>
+</span></span><span class="line"><span class="cl">        <span class="n">location</span> <span class="o">~</span> <span class="o">.</span><span class="p">(</span><span class="n">jsp</span><span class="o">|</span><span class="n">jspx</span><span class="o">|</span><span class="k">do</span><span class="p">)</span><span class="err">?</span><span class="o">$</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_set_header</span> <span class="n">Host</span> <span class="o">$</span><span class="n">host</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_set_header</span> <span class="n">X</span><span class="o">-</span><span class="n">Real</span><span class="o">-</span><span class="ne">IP</span> <span class="o">$</span><span class="n">remote_addr</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_set_header</span> <span class="n">X</span><span class="o">-</span><span class="n">Forwarded</span><span class="o">-</span><span class="n">For</span> <span class="o">$</span><span class="n">proxy_add_x_forwarded_for</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="n">proxy_pass</span> <span class="n">http</span><span class="p">:</span><span class="o">//</span><span class="mf">127.0</span><span class="o">.</span><span class="mf">0.1</span><span class="p">:</span><span class="mi">8080</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c1">#所有静态文件由nginx直接读取不经过tomcat或resin</span>
+</span></span><span class="line"><span class="cl">        <span class="n">location</span> <span class="o">~</span> <span class="o">.*.</span><span class="p">(</span><span class="n">htm</span><span class="o">|</span><span class="n">html</span><span class="o">|</span><span class="n">gif</span><span class="o">|</span><span class="n">jpg</span><span class="o">|</span><span class="n">jpeg</span><span class="o">|</span><span class="n">png</span><span class="o">|</span><span class="n">bmp</span><span class="o">|</span><span class="n">swf</span><span class="o">|</span><span class="n">ioc</span><span class="o">|</span><span class="n">rar</span><span class="o">|</span><span class="n">zip</span><span class="o">|</span><span class="n">txt</span><span class="o">|</span><span class="n">flv</span><span class="o">|</span><span class="n">mid</span><span class="o">|</span><span class="n">doc</span><span class="o">|</span><span class="n">ppt</span><span class="o">|</span>
+</span></span><span class="line"><span class="cl">        <span class="n">pdf</span><span class="o">|</span><span class="n">xls</span><span class="o">|</span><span class="n">mp3</span><span class="o">|</span><span class="n">wma</span><span class="p">)</span><span class="o">$</span>
+</span></span><span class="line"><span class="cl">        <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">expires</span> <span class="mi">15</span><span class="n">d</span><span class="p">;</span> 
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="n">location</span> <span class="o">~</span> <span class="o">.*.</span><span class="p">(</span><span class="n">js</span><span class="o">|</span><span class="n">css</span><span class="p">)</span><span class="err">?</span><span class="o">$</span>
+</span></span><span class="line"><span class="cl">        <span class="p">{</span>
+</span></span><span class="line"><span class="cl">            <span class="n">expires</span> <span class="mi">1</span><span class="n">h</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">        <span class="p">}</span>
+</span></span><span class="line"><span class="cl">    <span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="c1">######Nginx配置文件nginx.conf中文详解#####</span>
+</span></span></code></pre></div><p>参考链接: <a href="https://blog.6ag.cn/2918.html">https://blog.6ag.cn/2918.html</a></p>
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+        emojiCDN: '//i0.hdslb.com/bfs/emote/',
+        
+        emojiMaps: {
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+            "tv_亲亲": "a8111ad55953ef5e3be3327ef94eb4a39d535d06.png",
+            "tv_偷笑": "bb690d4107620f1c15cff29509db529a73aee261.png",
+            "tv_再见": "180129b8ea851044ce71caf55cc8ce44bd4a4fc8.png",
+            "tv_冷漠": "b9cbc755c2b3ee43be07ca13de84e5b699a3f101.png",
+            "tv_发怒": "34ba3cd204d5b05fec70ce08fa9fa0dd612409ff.png",
+            "tv_发财": "34db290afd2963723c6eb3c4560667db7253a21a.png",
+            "tv_可爱": "9e55fd9b500ac4b96613539f1ce2f9499e314ed9.png",
+            "tv_吐血": "09dd16a7aa59b77baa1155d47484409624470c77.png",
+            "tv_呆": "fe1179ebaa191569b0d31cecafe7a2cd1c951c9d.png",
+            "tv_呕吐": "9f996894a39e282ccf5e66856af49483f81870f3.png",
+            "tv_困": "241ee304e44c0af029adceb294399391e4737ef2.png",
+            "tv_坏笑": "1f0b87f731a671079842116e0991c91c2c88645a.png",
+            "tv_大佬": "093c1e2c490161aca397afc45573c877cdead616.png",
+            "tv_大哭": "23269aeb35f99daee28dda129676f6e9ea87934f.png",
+            "tv_委屈": "d04dba7b5465779e9755d2ab6f0a897b9b33bb77.png",
+            "tv_害羞": "a37683fb5642fa3ddfc7f4e5525fd13e42a2bdb1.png",
+            "tv_尴尬": "7cfa62dafc59798a3d3fb262d421eeeff166cfa4.png",
+            "tv_微笑": "70dc5c7b56f93eb61bddba11e28fb1d18fddcd4c.png",
+            "tv_思考": "90cf159733e558137ed20aa04d09964436f618a1.png",
+            "tv_惊吓": "0d15c7e2ee58e935adc6a7193ee042388adc22af.png",
+            "tv_打脸": "56ab10b624063e966bfcb76ea5dc4794d87dfd47.png",
+            "tv_抓狂": "fe31c08edad661d63762b04e17b8d5ae3c71a757.png",
+            "tv_抠鼻": "c666f55e88d471e51bbd9fab9bb308110824a6eb.png",
+            "tv_斜眼笑": "911f987aa8bc1bee12d52aafe62bc41ef4474e6c.png",
+            "tv_无奈": "ea8ed89ee9878f2fece2dda0ea8a5dbfe21b5751.png",
+            "tv_晕": "5443c22b4d07fb1907ccc610c8e6db254f2461b7.png",
+            "tv_流汗": "cead1c351ab8d79e9f369605beb90148db0fbed3.png",
+            "tv_流泪": "7e71cde7858f0cd50d74b0264aa26db612a8a167.png",
+            "tv_流鼻血": "c32d39db2737f89b904ca32700d140a9241b0767.png",
+            "tv_点赞": "f85c354995bd99e28fc76c869bfe42ba6438eff4.png",
+            "tv_生气": "26702dcafdab5e8225b43ffd23c94ac1ff932654.png",
+            "tv_生病": "8b0ec90e6b86771092a498c54f09fc94621c1900.png",
+            "tv_疑问": "0793d949b18d7be716078349c202c15ff166f314.png",
+            "tv_白眼": "c1d59f439e379ee50eef488bcb5e5378e5044ea4.png",
+            "tv_皱眉": "72ccad6679fea0d14cce648b4d818e09b8ffea2d.png",
+            "tv_目瞪口呆": "0b8cb81a68de5d5365212c99375e7ace3e7891b7.png",
+            "tv_睡着": "8b196675b53af58264f383c50ad0945048290b33.png",
+            "tv_笑哭": "1abc628f6d4f4caf9d0e7800878f4697abbc8273.png",
+            "tv_腼腆": "89712c0d4af73e67f89e35cbc518420380a7f6f4.png",
+            "tv_色": "61822c7e9aae5da76475e7892534545336b23a6f.png",
+            "tv_调侃": "4bc022533ef31544ca0d72c12c808cf4a1cce3e3.png",
+            "tv_调皮": "b9c41de8e82dd7a8515ae5e3cb63e898bf245186.png",
+            "tv_鄙视": "6e72339f346a692a495b123174b49e4e8e781303.png",
+            "tv_闭嘴": "c9e990da7f6e93975e25fd8b70e2e290aa4086ef.png",
+            "tv_难过": "87f46748d3f142ebc6586ff58860d0e2fc8263ba.png",
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+
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+            </div>
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+    <footer class="footer">
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+        <a href="https://varkai.com">Designed by VarKai,</a>
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+        
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+        buttonColorDark: '#212121', 
+        buttonColorLight: '#f7f7f7', 
+        saveInCookies: false, 
+        autoMatchOsTheme: true 
+    }).showWidget();
+
+    function addDarkmodeWidget(){
+        const hours = new Date().getHours();
+        if (hours >= 19 || hours <= 5){
+            new Darkmode({
+                right: '32px', 
+                bottom: 'unset', 
+                
+                time: '0.3s', 
+                mixColor: '#f7f7f7', 
+                backgroundColor: '#f7f7f7', 
+                buttonColorDark: '#212121', 
+                buttonColorLight: '#f7f7f7', 
+                saveInCookies: false, 
+                autoMatchOsTheme: true 
+            }).toggle();
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+    
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+</script>
+
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+
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+
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+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/docs/posts/javabasics/rookie-datatype/index.html b/docs/posts/javabasics/rookie-datatype/index.html
new file mode 100644
index 00000000..a59f7d82
--- /dev/null
+++ b/docs/posts/javabasics/rookie-datatype/index.html
@@ -0,0 +1,2434 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java数据类型 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="基本类型 Java语言提供了八种基本类型。六种数值类型（四个整数型，两个浮点型），一种字符类型，还有一种布尔型，俗称4类8种。 这里只介绍称4类8种，实际上，Jav" />
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+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+    <link rel="shortcut icon" href="https://whiteppure.github.io/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/toc.css" />
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+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e6%9c%ac%e7%b1%bb%e5%9e%8b">
+                    基本类型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e6%9c%ac%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2">
+                    基本类型转换
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%98%be%e5%bc%8f%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2">
+                    显式类型转换
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9a%90%e5%bc%8f%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2">
+                    隐式类型转换
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8c%85%e8%a3%85%e7%b1%bb%e5%9e%8b">
+                    包装类型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8b%86%e7%ae%b1%e4%b8%8e%e8%a3%85%e7%ae%b1">
+                    拆箱与装箱
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%ad%98%e6%b1%a0">
+                    缓存池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%95%e7%94%a8%e7%b1%bb%e5%9e%8b">
+                    引用类型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%95%e7%94%a8%e7%b1%bb%e5%9e%8b%e8%bd%ac%e6%8d%a2">
+                    引用类型转换
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e8%b1%a1%e7%9a%84%e6%af%94%e8%be%83">
+                    对象的比较
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e9%87%8f">
+                    常量
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9a%e4%b9%89%e5%b8%b8%e9%87%8f">
+                    定义常量
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#class%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    Class常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%90%e8%a1%8c%e6%97%b6%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    运行时常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ba%e4%bb%80%e4%b9%88%e9%9c%80%e8%a6%81%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    为什么需要常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#string%e7%b1%bb%e5%9e%8b">
+                    String类型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ba%e4%bb%80%e4%b9%88jdk9%e6%94%b9%e5%8f%98%e4%ba%86%e5%ad%98%e5%82%a8%e7%bb%93%e6%9e%84">
+                    为什么JDK9改变了存储结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%8d%e5%8f%af%e5%8f%98%e6%80%a7">
+                    不可变性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#new-stringabc%e4%bc%9a%e5%88%9b%e5%bb%ba%e5%87%a0%e4%b8%aa%e5%af%b9%e8%b1%a1">
+                    new String(“abc”)会创建几个对象
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ad%97%e7%ac%a6%e4%b8%b2%e5%b8%b8%e9%87%8f%e6%b1%a0">
+                    字符串常量池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#intern%e6%96%b9%e6%b3%95">
+                    intern方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ad%97%e7%ac%a6%e4%b8%b2%e5%b8%b8%e9%87%8f%e6%b1%a0%e9%95%bf%e5%ba%a6">
+                    字符串常量池长度
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8">
+                    使用
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%9b%e5%bb%ba%e5%ad%97%e7%ac%a6%e4%b8%b2">
+                    创建字符串
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8b%bc%e6%8e%a5%e5%ad%97%e7%ac%a6%e4%b8%b2">
+                    拼接字符串
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8b%bc%e6%8e%a5%e5%8e%9f%e7%90%86">
+                    “&#43;”拼接原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#stringbuffer%e4%b8%8estringbuilder">
+                    StringBuffer与StringBuilder
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e7%94%a8%e6%96%b9%e6%b3%95">
+                    常用方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%95%bf%e5%ba%a6%e9%99%90%e5%88%b6">
+                    长度限制
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#string%e7%b1%bb%e4%b8%8e%e7%bc%96%e7%a0%81">
+                    String类与编码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#unicode">
+                    Unicode
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%96%e7%a0%81%e4%b8%8e%e8%a7%a3%e7%a0%81">
+                    编码与解码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
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+                <a href="https://whiteppure.github.io/iblog/about/">关于</a>
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+            <h1>
+                <a href="https://whiteppure.github.io/iblog/">
+                    <span>脚踏实地</span>
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+            <p class="sub_title">
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+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1688701481347" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3517" width="16" height="16"><path d="M425.610455 85.814544H149.05897A42.303635 42.303635 0 0 0 106.6274 128.075535V896.492068c0 23.326702 18.976933 42.26099 42.43157 42.26099h682.743143a42.559504 42.559504 0 0 0 42.431569-42.559504v-384.016365a42.644793 42.644793 0 0 1 85.289587 0v384.016365A127.849091 127.849091 0 0 1 831.802113 1024H149.05897A127.635867 127.635867 0 0 1 21.337813 896.449423V128.03289A127.593222 127.593222 0 0 1 149.101614 0.524957h276.466196a42.644793 42.644793 0 0 1 0 85.289587z m564.062683 158.08425l-170.579174 170.579173a42.644793 42.644793 0 1 1-60.299738-60.299738L856.578738 256.393718H618.364922a42.644793 42.644793 0 1 1 0-85.289587h238.213816l-97.784512-97.784511A42.644793 42.644793 0 1 1 819.093964 13.019882l170.579174 170.579174a42.644793 42.644793 0 0 1 0 60.299738zM149.272194 597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h51.514911c59.190973 0 107.891327 23.284057 107.976617 97.102195 0 71.003581-49.46796 102.347504-106.185536 102.347504h-31.343923v66.781747a32.282109 32.282109 0 0 1-64.606862 0V597.552066z m92.709781 100.215264c31.429213 0 46.568114-16.46089 46.568114-45.757863 0-30.064579-17.313786-40.512554-48.359196-40.512554h-26.311837v86.270417h28.145563z m232.414124-142.860058c81.878003 0 136.036891 43.710913 136.036891 147.67892S556.231457 853.420826 477.935617 853.420826h-38.16709a42.644793 42.644793 0 0 1-42.644794-42.644793v-213.223967a42.644793 42.644793 0 0 1 42.644794-42.644794h34.542282z m-4.008611 240.729859c43.32711 0 73.988717-22.047358 73.988717-93.050939 0-71.046226-30.704251-90.705476-73.988717-90.705476h-8.699538v183.79906h8.699538zM692.481573 853.420826a32.282109 32.282109 0 0 1-32.282109-32.282108V597.552066a42.644793 42.644793 0 0 1 42.644793-42.644794h99.063855a29.680776 29.680776 0 1 1 0 59.404197h-77.144431v65.374469h61.749661a29.894 29.894 0 1 1 0 59.788h-61.749661v81.66478a32.282109 32.282109 0 0 1-32.282108 32.282108z" fill="#5f5f5f" p-id="3518"></path></svg>
+                    </a>
+                    <a id="export_pic" title="导出图片" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_markdown" title="导出markdown" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                    <a id="export_doc" title="导出文档" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
+                        <svg t="1689246982401" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="6825" width="16" height="16"><path d="M270.76864 608.32h180.8a31.68 31.68 0 0 0 0-62.976H270.76864a31.68 31.68 0 0 0 0 62.976zM271.34464 458.56h457.92a33.472 33.472 0 0 0 31.552-34.752 33.28 33.28 0 0 0-31.552-34.624H271.34464a34.816 34.816 0 0 0 0 69.376zM271.34464 293.504h457.92a33.344 33.344 0 0 0 31.552-34.688 33.216 33.216 0 0 0-31.552-34.624H271.34464a33.28 33.28 0 0 0-31.616 34.624 33.28 33.28 0 0 0 31.616 34.688z" p-id="6826" fill="#424242"></path><path d="M869.87264 0H153.77664A70.4 70.4 0 0 0 84.65664 70.912V953.6A69.952 69.952 0 0 0 153.77664 1024h370.048a32 32 0 0 0 0-63.68H147.12064V64h729.6v468.672a31.296 31.296 0 1 0 62.528 0V70.912A70.4 70.4 0 0 0 869.87264 0z" p-id="6827" fill="#424242"></path><path d="M482.16064 730.624h337.664L715.82464 625.216a28.864 28.864 0 0 1-7.936-28.736 29.184 29.184 0 0 1 20.608-21.184 29.632 29.632 0 0 1 29.12 8.128l174.784 177.216-174.784 176.96a29.184 29.184 0 0 1-49.728-13.312 29.248 29.248 0 0 1 8-28.8l103.936-105.344H482.16064a29.696 29.696 0 0 1-29.504-29.76 29.632 29.632 0 0 1 29.504-29.76z" p-id="6828" fill="#424242"></path></svg>
+                    </a>
+                </span>
+                <a  id="icon_more" title="更多" >
+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
+                </a>
+                <a  id="icon_less" class="display_none">
+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Java数据类型</h2>
+                        <span id="post_page_title_date" class="date">2021.01.20</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="基本类型">基本类型</h2>
+<p>Java语言提供了八种基本类型。六种数值类型（四个整数型，两个浮点型），一种字符类型，还有一种布尔型，俗称4类8种。
+这里只介绍称4类8种，实际上，Java中还存在另外一种基本类型 <code>void</code>，它也有对应的包装类<code>java.lang.Void</code>，不过我们无法直接对它们进行操作。</p>
+<table>
+<thead>
+<tr>
+<th>类型</th>
+<th>位数</th>
+<th>范围</th>
+<th>默认值</th>
+<th>示例</th>
+<th>备注</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>byte</td>
+<td>8</td>
+<td>-128 ~ 127</td>
+<td>0</td>
+<td><code>byte a = 100</code> <code>byte b = -50</code></td>
+<td>节省空间，常用于大型数组</td>
+</tr>
+<tr>
+<td>short</td>
+<td>16</td>
+<td>-2^15 ~ 2^15-1</td>
+<td>0</td>
+<td><code>short s = 1000</code> <code>short r = -20000</code></td>
+<td>节省空间，int变量占用空间的一半</td>
+</tr>
+<tr>
+<td>int</td>
+<td>32</td>
+<td>-2^31 ~ 2^31-1</td>
+<td>0</td>
+<td><code>int a = 100000</code> <code>int b = -200000</code></td>
+<td>默认的整型变量</td>
+</tr>
+<tr>
+<td>long</td>
+<td>64</td>
+<td>-2^63 ~ 2^63-1</td>
+<td>0L</td>
+<td><code>long a = 100000L</code> <code>long b = -200000L</code></td>
+<td>用于表示较大整数</td>
+</tr>
+<tr>
+<td>float</td>
+<td>32</td>
+<td>1.4E-45 ~ 3.4028235E38</td>
+<td>0.0f</td>
+<td><code>float f = 234.5f</code></td>
+<td>单精度浮点数，节省内存，不能表示精确值</td>
+</tr>
+<tr>
+<td>double</td>
+<td>64</td>
+<td>4.9E-324 ~ 1.7976931348623157E308</td>
+<td>0.0d</td>
+<td><code>double d = 123.4</code></td>
+<td>双精度浮点数，默认的浮点数类型，不能表示精确值</td>
+</tr>
+<tr>
+<td>char</td>
+<td>16</td>
+<td>\u0000 (0) ~ \uffff (65,535)</td>
+<td>\u0000</td>
+<td><code>char letter = 'A'</code></td>
+<td>存储单一的 Unicode 字符</td>
+</tr>
+<tr>
+<td>boolean</td>
+<td>~</td>
+<td>true, false</td>
+<td>false</td>
+<td><code>boolean one = true</code></td>
+<td>JVM 在编译时将 boolean 转换为 int，使用 1 表示 true，0 表示 false。</td>
+</tr>
+</tbody>
+</table>
+<p>一个byte(字节)等于8个bit(位)，bit是最小的单位，1b(字节)=8bit(位)。一般情况下，一个汉字是两个字节，英文与数字是一个字节。</p>
+<p><code>Float</code>和<code>Double</code>的最小值和最大值都是以科学记数法的形式输出的，结尾的&quot;E+数字&quot;表示E之前的数字要乘以10的多少次方，比如<code>3.14E3</code>就是<code>3.14 × 10^3</code>，<code>3.14E-3</code> 就是 <code>3.14 x 10^-3</code>。</p>
+<p>boolean 只有两个值，<code>true、false</code>，可以使用 1 bit 来存储，但是具体大小没有明确规定。
+JVM 会在编译时期将 boolean 类型的数据转换为 int，使用 1 来表示 true，0 表示 false。JVM 支持 boolean 数组，但是是通过读写 byte 数组来实现的。</p>
+<h3 id="基本类型转换">基本类型转换</h3>
+<p>在Java中，类型转换是将一种数据类型的值转换为另一种数据类型的过程。
+整型、常量、字符型数据可以混合运算。运算前，不同类型的数据先转化为同一类型，然后进行运算。</p>
+<p>基本类型的类型转换主要分为两类，隐式类型转换（自动类型转换）和显式类型转换（强制类型转换）。
+这些类型转换是为了处理不同数据类型之间的转换需求和类型匹配问题。</p>
+<p>基本数据类型转换时需注意：</p>
+<ul>
+<li>不能对boolean类型进行类型转换；</li>
+<li>不能把对象类型转换成不相关类的对象；</li>
+<li>在把容量大的类型转换为容量小的类型时必须使用强制类型转换；</li>
+<li>浮点数到整数的转换是通过舍弃小数得到，而不是四舍五入；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">(int)23.7 == 23;        
+</span></span><span class="line"><span class="cl">(int)-45.89f == -45
+</span></span></code></pre></div></li>
+<li>转换过程中可能导致溢出或损失精度，在运算时要避免该问题。例如：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">// 因为 byte 类型是 8 位，最大值为127，所以当 int 强制转换为 byte 类型时，值 128 时候就会导致溢出
+</span></span><span class="line"><span class="cl">int i =128;   
+</span></span><span class="line"><span class="cl">byte b = (byte)i;
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="显式类型转换">显式类型转换</h4>
+<p>显式类型转换也叫强制类型转换，显式类型转换在可能出现数据丢失或溢出的风险的情况下进行，需要使用强制类型转换运算符。
+基本类型的显式转换顺序：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">double -&gt; float -&gt; long -&gt; int -&gt; short -&gt; byte
+</span></span><span class="line"><span class="cl">double -&gt; float -&gt; long -&gt; int -&gt; char
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// double -&gt; float -&gt; long -&gt; int -&gt; short -&gt; byte</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">doubleValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">.</span><span class="na">04</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">float</span><span class="w"> </span><span class="n">floatValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="w"> </span><span class="n">doubleValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">longValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">long</span><span class="p">)</span><span class="w"> </span><span class="n">floatValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">intValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="n">longValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">short</span><span class="w"> </span><span class="n">shortValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">short</span><span class="p">)</span><span class="w"> </span><span class="n">intValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">byte</span><span class="w"> </span><span class="n">byteValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">shortValue</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// double -&gt; float -&gt; long -&gt; int -&gt; char</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">doubleVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">97</span><span class="p">.</span><span class="na">04</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">float</span><span class="w"> </span><span class="n">floatVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="w"> </span><span class="n">doubleVal</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">longVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">long</span><span class="p">)</span><span class="w"> </span><span class="n">floatVal</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">intVal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="n">longVal</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">char</span><span class="w"> </span><span class="n">charValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">char</span><span class="p">)</span><span class="w"> </span><span class="n">intVal</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><h4 id="隐式类型转换">隐式类型转换</h4>
+<p>隐式类型转换是指编译器在编译时自动完成的类型转换，也称为自动类型转换。与显示类型转换相反，这种转换通常在没有数据丢失风险的情况下进行。
+Java 会自动将较小的基本数据类型转换为较大的基本数据类型，以避免数据丢失。转换顺序如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">byte -&gt; short -&gt; int -&gt; long -&gt; float -&gt; double
+</span></span><span class="line"><span class="cl">char -&gt; int -&gt; long -&gt; float -&gt; double
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// byte -&gt; short -&gt; int -&gt; long -&gt; float -&gt; double</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">byte</span><span class="w"> </span><span class="n">byteValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">42</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">short</span><span class="w"> </span><span class="n">shortValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">byteValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">intValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">shortValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">longValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">intValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">float</span><span class="w"> </span><span class="n">floatValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">longValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">doubleValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">floatValue</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// char -&gt; int -&gt; long -&gt; float -&gt; double</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">char</span><span class="w"> </span><span class="n">charValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">&#39;A&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">charToInt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">charValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">charToLong</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">charToInt</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">float</span><span class="w"> </span><span class="n">charToFloat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">charToLong</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">charToDouble</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">charToFloat</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>隐式类型转换还有一种比较特殊的情况，对于 += 运算符来说，如果左右两边的操作数类型不同，编译器会自动将右边操作数的类型转换为左边操作数的类型，然后执行加法操作和赋值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AdditionAssignment</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="w"> </span><span class="n">byteValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">byteValue</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="c1">// 等价于 byteValue = (byte)(byteValue + 5);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">intValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">longValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">200L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">intValue</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">longValue</span><span class="p">;</span><span class="w"> </span><span class="c1">// 等价于 intValue = (int)(intValue + longValue);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">float</span><span class="w"> </span><span class="n">floatValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">.</span><span class="na">5f</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">double</span><span class="w"> </span><span class="n">doubleValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">20</span><span class="p">.</span><span class="na">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">floatValue</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">doubleValue</span><span class="p">;</span><span class="w"> </span><span class="c1">// 等价于 floatValue = (float)(floatValue + doubleValue);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="包装类型">包装类型</h3>
+<table>
+<thead>
+<tr>
+<th>基本类型</th>
+<th>包装类型</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>byte</td>
+<td>Byte</td>
+</tr>
+<tr>
+<td>boolean</td>
+<td>Boolean</td>
+</tr>
+<tr>
+<td>short</td>
+<td>Short</td>
+</tr>
+<tr>
+<td>char</td>
+<td>Character</td>
+</tr>
+<tr>
+<td>int</td>
+<td>Integer</td>
+</tr>
+<tr>
+<td>long</td>
+<td>Long</td>
+</tr>
+<tr>
+<td>float</td>
+<td>Float</td>
+</tr>
+<tr>
+<td>double</td>
+<td>Double</td>
+</tr>
+</tbody>
+</table>
+<p>在这八个类名中，除了 <code>Integer</code> 和 <code>Character</code> 类以外，其它六个类的类名和基本数据类型一致，只是类名的第一个字母大写。
+其中<code>Integer、Long、Byte、Double、Float、Short</code>都是抽象类<code>Number</code>的子类。</p>
+<p>因为 Java 是一种面向对象语言，很多地方都需要使用对象而不是基本数据类型。
+比如在集合类中，我们是无法将<code> int 、double</code> 等类型放进去的，因为集合的容器要求元素是 <code>Object</code> 类型，所以才有了对应基本类型分包装类型。</p>
+<h4 id="拆箱与装箱">拆箱与装箱</h4>
+<p>基本类型都有对应的包装类型，基本类型与其对应的包装类型之间的赋值使用<strong>自动装箱与拆箱</strong>完成。以<code>Integer</code>转<code>int</code> 为例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Integer x = 2;     // 装箱 调用了 Integer.valueOf(2)
+</span></span><span class="line"><span class="cl">int y = x;         // 拆箱 调用了 X.intValue()
+</span></span></code></pre></div><ul>
+<li>自动装箱: 将基本数据类型自动转换成对应的包装类；</li>
+<li>自动拆箱：将包装类自动转换成对应的基本数据类型；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Integer i = 10;  //自动装箱
+</span></span><span class="line"><span class="cl">int b = i;     //自动拆箱
+</span></span></code></pre></div><p>为了探究自动拆箱、自动装箱的原理，将以下代码进行编译，查看<code>class</code>文件：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="n">args</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Integer</span><span class="w"> </span><span class="n">integer</span><span class="o">=</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">integer</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>反编译得到</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="n">args</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Integer</span><span class="w"> </span><span class="n">integer</span><span class="o">=</span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">integer</span><span class="p">.</span><span class="na">intValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>int</code>的自动装箱是通过<code>Integer.valueOf()</code>方法来实现的，<code>Integer</code>的自动拆箱都是通过 <code>integer.intValue</code>来实现的。</p>
+<p>其实自动装箱和自动拆箱是Java中的语法糖，用于简化基本数据类型和其对应包装类型之间的转换操作。
+当将基本数据类型赋值给对应的包装类型时，编译器会调用包装类型的<code>valueOf()</code>方法来创建一个包装对象，并将基本数据类型的值传递给这个方法。
+当需要使用包装类型对象中的值进行基本数据类型的操作时，编译器会自动调用包装类型对象的<code>xxxValue()</code>方法，将包装对象转换为对应的基本数据类型值。</p>
+<p>自动装箱和拆箱虽然方便，但是在使用的时候也需要注意一些问题：</p>
+<ul>
+<li>比较：包装对象的数值比较，不能简单的使用<code>==</code>，虽然 -128 到 127 之间的数字可以，但是这个范围之外还是需要使用 <code>equals</code>方法进行比较；</li>
+<li>NPE：因为有自动拆箱的机制，如果初始的包装类型对象为<code>null</code>，那么在自动拆箱的时候的就会报<code>NullPointerException</code>，在使用时需要格外注意；</li>
+<li>性能：频繁的装箱和拆箱操作可能会影响性能，因为涉及到对象的创建和销毁。如果一个for循环中有大量拆装箱操作，会浪费很多资源；</li>
+</ul>
+<h4 id="缓存池">缓存池</h4>
+<p>在Java中，对于某些包装类型的对象，存在一个缓存池，这是一种优化机制，可以减少频繁创建对象的开销，提升性能。</p>
+<p>基本类型对应的缓冲池如下：</p>
+<ul>
+<li><code>Boolean</code>类型的<code>true</code>和<code>false</code>值在静态初始化块中被缓存起来了；</li>
+<li><code>Byte</code>类型在 -128 到 127 之间的值会被缓存；</li>
+<li><code>Character</code>类型在 &lsquo;\u0000&rsquo; 到 &lsquo;\u007F&rsquo; 之间的值会被缓存；</li>
+<li><code>Short</code>、<code>Integer</code>和<code>Long</code>类型在范围 -128 到 127 之间的值会被缓存；</li>
+</ul>
+<p>在使用这些基本类型对应的包装类型时，如果该数值范围在缓冲池范围内，就可以直接使用缓冲池中的对象。两种浮点数类型的包装类<code>Float</code>，<code>Double</code>并没有实现常量池技术。</p>
+<p>在JDK 1.8所有的数值类缓冲池中，<code>Integer</code>的缓冲池<code>IntegerCache</code>很特殊，这个缓冲池的下界是-128，上界默认是127，但是这个上界是可调的，在启动JVM的时候，通过<code>-XX:AutoBoxCacheMax=&lt;size&gt;</code>来指定这个缓冲池的大小，该选项在 JVM 初始化的时候会设定一个名为<code>java.lang.IntegerCache.high</code>系统属性，然后 <code>IntegerCache</code>初始化的时候就会读取该系统属性来决定上界。</p>
+<p>使用<code>Integer.valueOf()</code>方法来创建<code>Integer</code>对象时，会优先从缓冲池中获取对象，如果缓冲池中不存在该值的对象，则会创建一个新的对象。
+<code>new Integer(123)</code>，这种方式会显式地创建一个新的<code>Integer</code>对象，每次调用<code>new Integer(123)</code>都会创建一个新的对象实例。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Integer</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">123</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Integer</span><span class="w"> </span><span class="n">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">123</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">y</span><span class="p">);</span><span class="w">    </span><span class="c1">// false 因为是两个不同的对象实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Integer</span><span class="w"> </span><span class="n">z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">123</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Integer</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">123</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">z</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">k</span><span class="p">);</span><span class="w">   </span><span class="c1">// true 因为返回的是同一个缓存池中的对象实例</span><span class="w">
+</span></span></span></code></pre></div><p><code>Integer.valueOf()</code>方法的实现比较简单，就是先判断值是否在缓存池中，如果在的话就直接返回缓存池的内容。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public static Integer valueOf(int i) {
+</span></span><span class="line"><span class="cl">    if (i &gt;= IntegerCache.low &amp;&amp; i &lt;= IntegerCache.high)
+</span></span><span class="line"><span class="cl">        return IntegerCache.cache[i + (-IntegerCache.low)];
+</span></span><span class="line"><span class="cl">    return new Integer(i);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在 Java 8 中，<code>Integer</code>缓存池的大小默认为 -128~127，在源码中也能看到具体的实现。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">low</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">128</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">high</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">cache</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// high value may be configured by property</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">127</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">integerCacheHighPropValue</span><span class="w"> </span><span class="o">=</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sun</span><span class="p">.</span><span class="na">misc</span><span class="p">.</span><span class="na">VM</span><span class="p">.</span><span class="na">getSavedProperty</span><span class="p">(</span><span class="s">&#34;java.lang.Integer.IntegerCache.high&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">integerCacheHighPropValue</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">parseInt</span><span class="p">(</span><span class="n">integerCacheHighPropValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">127</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// Maximum array size is Integer.MAX_VALUE</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="p">(</span><span class="o">-</span><span class="n">low</span><span class="p">)</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="p">(</span><span class="w"> </span><span class="n">NumberFormatException</span><span class="w"> </span><span class="n">nfe</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// If the property cannot be parsed into an int, ignore it.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">high</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">h</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">cache</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="o">[</span><span class="p">(</span><span class="n">high</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">low</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">low</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">cache</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">k</span><span class="o">++</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cache</span><span class="o">[</span><span class="n">k</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">j</span><span class="o">++</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// range [-128, 127] must be interned (JLS7 5.1.7)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">assert</span><span class="w"> </span><span class="n">IntegerCache</span><span class="p">.</span><span class="na">high</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">127</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>而编译器会在自动装箱过程会调用 <code>valueOf()</code>方法，因此多个值相同且值在缓存池范围内的<code>Integer</code>实例使用自动装箱来创建，那么就会引用相同的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Integer m = 123;
+</span></span><span class="line"><span class="cl">Integer n = 123;
+</span></span><span class="line"><span class="cl">System.out.println(m == n); // true
+</span></span></code></pre></div><p>所以<code>Integer</code>、<code>int </code>在 <code>-127~128</code>之间是不会创建新的对象的，即</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">12</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">12</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="o">==</span><span class="n">b</span><span class="p">);</span><span class="c1">//true</span><span class="w">
+</span></span></span></code></pre></div><h2 id="引用类型">引用类型</h2>
+<p>在Java中，引用类型是指除了基本数据类型之外的所有类型，它们都是通过指向一个对象(类似于C的指针)来访问和操作的，所以叫做引用类型。所有引用类型的默认值都是<code>null</code>。</p>
+<p>引用类型主要包括：</p>
+<ul>
+<li>类
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>数组类型
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>接口类型
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">interface</span> <span class="nc">MyInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>注解类型
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@interface</span><span class="w"> </span><span class="n">MyAnnotation</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 注解</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>枚举类型
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">enum</span><span class="w"> </span><span class="n">Day</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 枚举</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>与基本类型的区别：</p>
+<ol>
+<li>内存分配：基本数据类型在被创建时，在栈中直接划分一块内存，将数值直接存入栈中；引用数据类型在被创建时，先在堆中开辟内存创建存放值，然后引用到栈中的是在堆中的地址值；</li>
+<li>传递参数：基本数据类型是值传递，引用数据类型是引用传递；</li>
+<li>继承和多态：引用类型支持继承和多态特性，可以通过父类引用指向子类对象，实现代码的灵活性和扩展性；</li>
+<li>比较：引用类型的变量比较的是对象的引用，而不是对象的内容。使用 == 运算符比较引用类型变量时，比较的是它们在内存中的地址是否相同；</li>
+<li><code>null</code>值：引用类型的变量可以赋予<code>null</code>值，表示它不引用任何对象。使用未初始化的引用类型变量或将其设置为<code>null</code>可以避免空指针异常；</li>
+</ol>
+<p>需要注意的是<code>String</code>类是引用类型，不是基本类型。
+默认情况下，Java中的浮点数类型是<code>double</code>类型，如果你希望定义一个<code>float</code>类型的浮点数，需要在数值后面加上 F 或 f 后缀，例如<code>float f = 1.23f</code>。
+Java 中的浮点数类型 (<code>float</code>和<code>double</code>)是用来表示近似值的，而不是精确的数值。
+因此，在涉及到精确计算的场景中，尤其是涉及货币等需要精确表示的值时，应当使用<code>BigDecimal</code>类型来避免精度问题。</p>
+<h3 id="引用类型转换">引用类型转换</h3>
+<p>在Java中，引用类型的类型转换主要涉及向上转型和向下转型两种操作，引用类型的转换是基于继承关系和多态性，只有在存在父子类关系或者接口实现关系时才能进行。</p>
+<p>向上转型是指将一个子类的对象引用转换为其父类类型或者更高层次的类型。
+向上转型是安全的，这种转型是隐式的，编译器会自动进行处理，子类对象可以直接赋值给父类类型的引用变量。
+这种转型通常发生在子类对象需要作为父类对象使用的场景中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Dog</span><span class="w"> </span><span class="n">myDog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w"> </span><span class="c1">// 创建Dog对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">myAnimal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myDog</span><span class="p">;</span><span class="w"> </span><span class="c1">// 向上转型为Animal类型，隐式转型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>向下转型是指将一个父类类型或者更高层次的类型的对象引用转换为其子类类型。
+向下转型是需要显式指定的，并且需要进行类型检查（<code>instanceof</code>）以及类型转换（<code>cast</code>）操作。如果实际对象不是目标类型，会抛出<code>ClassCastException</code>异常。
+如果引用变量是<code>null</code>，无法进行任何类型转换操作。在转换之前，需要确保引用变量不为<code>null</code>，否则会导致<code>NPE</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">myAnimal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w"> </span><span class="c1">// 向上转型为Animal类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">myAnimal</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Dog</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Dog</span><span class="w"> </span><span class="n">myDog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Dog</span><span class="p">)</span><span class="w"> </span><span class="n">myAnimal</span><span class="p">;</span><span class="w"> </span><span class="c1">// 安全的向下转型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="对象的比较">对象的比较</h3>
+<p>在Java中，引用类型的比较涉及到比较对象的引用值，而不是对象的内容。这是因为在Java中，每个对象变量存储的是对象的引用地址，而不是对象本身。
+使用<code>==</code>操作符比较两个对象引用时，比较的是它们在内存中的地址是否相同，即是否引用同一个对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str2</span><span class="p">);</span><span class="w"> </span><span class="c1">// false，str1和str2引用不同的对象实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str3</span><span class="p">);</span><span class="w"> </span><span class="c1">// true，str1和str3引用同一个对象实例</span><span class="w">
+</span></span></span></code></pre></div><p>在比较两个对象是否相等时，使用最多的是<code>equals()</code>方法，它通常在类中被重写以实现特定的比较逻辑。
+默认情况下，<code>equals()</code>方法和<code>==</code>操作符行为一样，比较的是对象的引用，但是如果类中重写了<code>equals()</code>方法，那就不一定了。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str1</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">str2</span><span class="p">));</span><span class="w"> </span><span class="c1">// true，比较的是对象的内容</span><span class="w">
+</span></span></span></code></pre></div><p>上面的例子中，<code>str1.equals(str2)</code>返回<code>true</code>，因为<code>String</code>类重写了<code>equals()</code>方法，用来比较字符串的内容而不是引用值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// String类中的equals()方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">anObject</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">anObject</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">anObject</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">anotherString</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="p">)</span><span class="n">anObject</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">anotherString</span><span class="p">.</span><span class="na">value</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">char</span><span class="w"> </span><span class="n">v1</span><span class="o">[]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">char</span><span class="w"> </span><span class="n">v2</span><span class="o">[]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">anotherString</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="o">--</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">v1</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">v2</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">i</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="常量">常量</h2>
+<p>在Java中，常量指的是一种不可改变的量或者数值，其值在程序执行过程中不会发生变化。常量在Java中有两种主要的形式：</p>
+<ul>
+<li>字面常量：在计算机科学中，字面量是用于表达源代码中一个固定值的表示法。几乎所有计算机编程语言都具有对基本值的字面量表示，诸如：整数、浮点数以及字符串；而有很多也对布尔类型和字符类型的值也支持字面量表示，还有一些甚至对枚举类型的元素以及像数组、记录和对象等复合类型的值也支持字面量表示法；</li>
+<li><code>final</code>修饰的变量：Java常量简单理解为<code>final</code>修饰的变量。Java常量就是在程序运行过程中一直不会改变的量的量，<code>final</code>修饰的变量必须在声明时初始化，一旦初始化后，其值就不能再被修改；</li>
+</ul>
+<p>常量和数据类型之间有密切的关系，常量可以是任何数据类型的值，包括基本数据类型和引用类型，如对象或数组。
+常量的数据类型必须与其值的数据类型匹配，例如<code>final int MAX_SIZE = 100</code>中的常量<code>MAX_SIZE</code>是整数类型。</p>
+<p>为防止混淆和更好理解，将常量，变量和字面量用代码举例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">int a = 10; // a为变量，10为字面量
+</span></span><span class="line"><span class="cl">final int b = 10;  // b为常量，10为字面量
+</span></span><span class="line"><span class="cl">static c = &#34;Hello World&#34;;  // c为变量，HelloWorld为字面量
+</span></span></code></pre></div><ul>
+<li>常量：程序运行中，固定不变的量；</li>
+<li>变量：值可以修改的数据类型；</li>
+<li>字面量：字面量就是数据，是由字母、数字等构成的字符串或者数值，如30（整型）、3.15（浮点型）、“我是字符串”（字符串型）、‘中’（字符型）、true（布尔型）、false（布尔型）等，只能作为右值出现，如<code>int a = 10</code>，这里的a是左值，10为右值；</li>
+</ul>
+<h3 id="定义常量">定义常量</h3>
+<p>在 Java 中使用<code>final</code>关键字来修饰常量，声明方式和变量类似。
+要声明一个常量，第一需要制定数据类型，第二需要通过<code>final</code>关键字进行限定格式：<code>final 数据类型 常量名称[=值]</code>。</p>
+<p><code>final</code>关键字表示最终的，它可以修改很多元素：</p>
+<ul>
+<li>当<code>final</code>修饰变量就变成了常量；</li>
+<li>当<code>final</code>用于修饰方法时，表示该方法不能被子类重写；</li>
+<li>当<code>final</code>用于修饰类时，表示该类不能被继承；</li>
+</ul>
+<p>常量因为被<code>final</code>修饰一旦初始化后，其值就不能再被修改，所以在定义常量时就需要对该常量进行初始化。
+为了与变量区别，提高代码的可读性和可维护性，常量取名一般都用大写字符，单词之间使用下划线 <code>_</code>分隔，如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">final double PI = 3.1415927;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">public static final int MAX_VALUE = 100;
+</span></span></code></pre></div><p>常量可以根据它们的作用范围和声明位置将其归类。常量的类型包括静态常量、成员常量和局部常量。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public class HelloWorld {
+</span></span><span class="line"><span class="cl">    // 静态常量
+</span></span><span class="line"><span class="cl">    public static final double PI = 3.14;
+</span></span><span class="line"><span class="cl">    // 声明成员常量
+</span></span><span class="line"><span class="cl">    final int y = 10;
+</span></span><span class="line"><span class="cl">    public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">        // 声明局部常量
+</span></span><span class="line"><span class="cl">        final double x = 3.3;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="常量池">常量池</h3>
+<p>常量池是Java为了提高性能和减少内存开销而引入的一种机制，常量则是程序中不可改变的值，在程序中定义的不可变值，存储在栈、堆或常量池中。</p>
+<p>常量池、可以看做是一张表，虚拟机指令根据这张常量表找到要执行的类名、方法名、参数类型、字面量等类型。
+在Java中，大致上可以分为三种常量池，分别是字符串常量池、Class常量池(静态常量池)和运行时常量池。
+我们常说的常量池，指的是方法区中的运行时常量池。</p>
+<h4 id="class常量池">Class常量池</h4>
+<p>在Java中，每个编译后的<code>.class</code>文件中包含一个常量池，用于存储与类相关的各种常量，这个常量池被称为Class常量池，这些常量包括字面量和符号引用。</p>
+<p><code>class</code>文件，主要在平台无关性和网络移动性方面使Java更适合网络。
+它在平台无关性方面的任务，是为Java程序提供独立于底层主机平台的二进制形式的服务。
+二进制形式的服务会产生字节码，有了字节码，无论是哪种平台（如Windows、Linux等），只要安装了虚拟机，都可以直接运行字节码。
+目前Java虚拟机已经可以支持很多除Java语言以外的语言了，如Groovy、JRuby、Jython、Scala等。之所以可以支持，就是因为这些语言也可以被编译成字节码。
+而虚拟机并不关心字节码是有哪种语言编译而来的。</p>
+<p>来看一下字节码文件，将下面代码通过<code>javac</code>命令编译：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HelloWorld</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>生成<code>.class</code>文件.<code>vi</code>命令查看：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Êþº¾^@^@^@4^@^Q
+</span></span><span class="line"><span class="cl">^@^D^@^M^H^@^N^G^@^O^G^@^P^A^@^F&lt;init&gt;^A^@^C()V^A^@^DCode^A^@^OLineNumberTable^A^@^Dmain^A^@^V([Ljava/lang/String;)V^A^@
+</span></span><span class="line"><span class="cl">SourceFile^A^@^OHelloWorld.java^L^@^E^@^F^A^@^C123^A^@7com/example/springboot/example/security/util/HelloWorld^A^@^Pjava/lang/Object^@!^@^C^@^D^@^@^@^@^@^B^@^A^@^E^@^F^@^A^@^G^@^@^@^]^@^A^@^A^@^@^@^E*·^@^A±^@^@^@^A^@^H^@^@^@^F^@^A^@^@^@^C^@        ^@      ^@
+</span></span><span class="line"><span class="cl">^@^A^@^G^@^@^@ ^@^A^@^B^@^@^@^D^R^BL±^@^@^@^A^@^H^@^@^@
+</span></span><span class="line"><span class="cl">^@^B^@^@^@^E^@^C^@^F^@^A^@^K^@^@^@^B^@^L
+</span></span></code></pre></div><p>使用16进制打开<code>class</code>文件，即使用<code>vim xxx.class</code> ，然后在交互模式下，输入<code>%!xxd</code> ，即可得到：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">00000000: cafe babe 0000 0034 0011 0a00 0400 0d08  .......4........
+</span></span><span class="line"><span class="cl">00000010: 000e 0700 0f07 0010 0100 063c 696e 6974  ...........&lt;init
+</span></span><span class="line"><span class="cl">00000020: 3e01 0003 2829 5601 0004 436f 6465 0100  &gt;...()V...Code..
+</span></span><span class="line"><span class="cl">00000030: 0f4c 696e 654e 756d 6265 7254 6162 6c65  .LineNumberTable
+</span></span><span class="line"><span class="cl">00000040: 0100 046d 6169 6e01 0016 285b 4c6a 6176  ...main...([Ljav
+</span></span><span class="line"><span class="cl">00000050: 612f 6c61 6e67 2f53 7472 696e 673b 2956  a/lang/String;)V
+</span></span><span class="line"><span class="cl">00000060: 0100 0a53 6f75 7263 6546 696c 6501 000f  ...SourceFile...
+</span></span><span class="line"><span class="cl">00000070: 4865 6c6c 6f57 6f72 6c64 2e6a 6176 610c  HelloWorld.java.
+</span></span><span class="line"><span class="cl">00000080: 0005 0006 0100 0331 3233 0100 3763 6f6d  .......123..7com
+</span></span><span class="line"><span class="cl">00000090: 2f65 7861 6d70 6c65 2f73 7072 696e 6762  /example/springb
+</span></span><span class="line"><span class="cl">000000a0: 6f6f 742f 6578 616d 706c 652f 7365 6375  oot/example/secu
+</span></span><span class="line"><span class="cl">000000b0: 7269 7479 2f75 7469 6c2f 4865 6c6c 6f57  rity/util/HelloW
+</span></span><span class="line"><span class="cl">000000c0: 6f72 6c64 0100 106a 6176 612f 6c61 6e67  orld...java/lang
+</span></span></code></pre></div><p><code>HelloWorld.class</code>文件中的前八个字母是<code>cafe babe</code>，这就是<code>class</code>文件的魔数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">cafe babe   0000      0034        0011      0a00 0400 0d08
+</span></span><span class="line"><span class="cl">   魔数    此版本号   主版本号    常量池计数器      常量池计数区
+</span></span></code></pre></div><p>我们需要知道的是，每个<code>class</code>文件的前四个字节表示魔数，他的唯一作用是确定这个文件是否是一个能被虚拟机接受的<code>class</code>文件，紧接着魔数的4个字节后，第5个和第6个表示次版本号，第7、8表示主版本号。
+我生成的<code>class</code>文件的版本号是16进制<code>0034</code>，转化为10进制是52，这是Java8对应的版本。也就是说，这个版本的字节码，在JDK 1.8以下的版本中无法运行，在版本号后面的，就是Class常量池入口了。</p>
+<p>Class常量池中主要存放两大类常量，字面量和符号引用。</p>
+<ul>
+<li>符号引用：符号引用是编译原理中的概念，是相对于直接引用来说的，主要包括了以下三类常量：类和接口的全限定名、字段的名称和描述符、方法的名称和描述符。
+符号引用以一组符号来描述所引用的目标。符号引用可以是任何形式的字面量，只要使用时能无歧义地定位到目标即可，符号引用和虚拟机的布局无关；</li>
+<li>字面量：字面量是指在Java源代码中明确给出的常量值。由字母、数字等构成的字符串或者数值，如30（整型）、3.15（浮点型）、“我是字符串”（字符串型）、‘中’（字符型）、true（布尔型）、false（布尔型）等，只能作为右值出现，如<code>int a = 10</code>，这里的a是左值，10为右值；</li>
+</ul>
+<p>在编译的时候每个java类都会被编译成一个<code>class</code>文件，但在编译的时候虚拟机并不知道所引用类的地址，所以就用符号引用来代替，
+而在<strong>解析阶段</strong>就是为了把符号引用转化成为真正的地址的过程。</p>
+<blockquote>
+<p>解析阶段:
+Java类从加载到虚拟机内存中开始，到卸载出内存为止，它的整个生命周期包括：加载、 验证、 准备、 解析、 初始化、 卸载，总共七个阶段。其中验证、准备、解析统称为连接。
+而在解析阶段会有一步将常量池当中二进制数据（符号引用）转化为直接引用的过程。</p>
+</blockquote>
+<p>在Java编译阶段，由<code>.java</code>文件会生成<code>.class</code>文件。
+<code>class</code>文件中除了包含类的版本、字段、方法、接口等描述信息外，还有一项信息就是常量池，用于存放编译器生成的各种字面量和符号引用。
+由于不同的<code>class</code>文件中包含的常量的个数是不固定的，所以在<code>class</code>文件的常量池入口处设置两个字节的常量池容量计数器，记录了常量池中常量的个数。</p>
+<p>Class常量池可以理解为是Class文件中的资源仓库。
+Class常量池中保存了各种常量，而这些常量都是开发者定义出来，需要在程序的运行期使用的。
+Java代码在进行<code>javac</code>编译的时候，在<code>class</code>文件中不会保存各个方法、字段的最终内存布局信息，因此这些字段、方法的符号引用不经过运行期转换的话无法得到真正的内存入口地址，也就无法直接被虚拟机使用。
+当虚拟机运行时，需要从常量池获得对应的符号引用，再在类创建时或运行时解析、翻译到具体的内存地址之中。
+Class常量池是用来保存常量的一个媒介场所，并且是一个中间场所。在JVM真的运行时，需要把常量池中的常量加载到内存中。</p>
+<h4 id="运行时常量池">运行时常量池</h4>
+<p>运行时常量池是每一个类或接口的常量池的运行时表示形式。
+每一个运行时常量池都分配在Java虚拟机的方法区之中，在类和接口被加载到虚拟机后，对应的运行时常量池就被创建出来。
+当创建类或接口的运行时常量池时，如果构造运行时常量池所需的内存空间，超过了方法区所能提供的最大值，则JVM会抛<code>OutOfMemoryError</code>异常。</p>
+<p>简单说来就是JVM在完成类装载操作后，将<code>class</code>文件中的常量池载入到内存中，并保存在方法区中，我们常说的常量池，就是指方法区中的运行时常量池。
+根据JVM规范，JVM内存共分为虚拟机栈、堆、方法区、程序计数器、本地方法栈五个部分，运行时常量池存放在JVM内存模型中的方法区中。
+在不同版本的JDK中，运行时常量池所处的位置也不一样。以<code>HotSpot</code>为例，JDK1.7之前方法区位于永久代，由于一些原因在JDK1.8时彻底祛除了永久代，用元空间代替。</p>
+<p>运行时常量池内容包含了Class常量池中的常量和字符串常量池中的内容。
+它包含多种不同的常量，也包括编译期就已经明确的数值字面量、到运行期解析后才能够获得的方法或者字段引用。
+它扮演了类似传统语言中符号表的角色，不过它存储数据范围比通常意义上的符号表要更为广泛。</p>
+<p>保存在JVM方法区中的叫运行时常量池，在 class/字节码 文件中的叫Class常量池（静态常量池）。
+与类文件中的Class常量池不同的是，运行时常量池是在类加载到内存后动态生成的，相对于Class文件常量池的另一重要特征是具备动态性。
+运行时常量池的动态性体现在它不仅仅是简单地静态存储常量值，而是支持了Java程序在运行时动态加载类、操作字符串、实现动态代理和利用反射等高级特性。
+例如，反射机制可以通过运行时常量池中的符号引用动态加载类、获取和调用方法等。</p>
+<h4 id="为什么需要常量池">为什么需要常量池</h4>
+<p>一个Java源文件中的类、接口，编译后产生一个字节码文件。
+而Java中的字节码需要数据支持，通常这种数据会很大以至于不能直接存到字节码里，换另一种方式，可以存到常量池，这个字节码包含了指向常量池的引用，在动态链接的时候会用到运行时常量池。</p>
+<p>比如：如下的代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SimpleClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sayHello</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>虽然上述代码生成的class文件只有194字节，但是里面却使用了<code>String</code>、<code>System</code>、<code>PrintStream</code>及<code>Object</code>等结构。
+这里的代码量其实很少了，如果代码多的话，引用的结构将会更多，这样就体现出常量池的作用了。</p>
+<p>常量池是为了避免频繁的创建和销毁对象而影响系统性能，其实现了对象的共享，避免了相同内容的字符串的创建，节省了内存，省去了创建相同字符串的时间，同时提升了性能。</p>
+<h2 id="string类型">String类型</h2>
+<p>在Java编程中，字符串类型是一个极其基础和重要的类，字符串属于对象，并且由专门的<code>String</code>类来创建和管理，它被广泛用于表示和操作文本数据。</p>
+<p>由于 <code>String</code>被声明为 final，它是不可变的，即一旦创建，其值无法更改。这种设计不仅确保了字符串的安全性和稳定性，还优化了内存使用。
+<code>String</code>类还实现了<code>Serializable</code>接口，这意味着字符串可以被序列化，以便在不同的Java虚拟机之间传输。
+此外，<code>String</code>实现了<code>Comparable</code>接口，使得字符串对象可以进行自然排序。</p>
+<h3 id="为什么jdk9改变了存储结构">为什么JDK9改变了存储结构</h3>
+<p>在Java8中，<code>String</code>内部使用<code>char</code>数组存储数据。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">String</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">implements</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">Serializable</span><span class="p">,</span><span class="w"> </span><span class="n">Comparable</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">CharSequence</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The value is used for character storage. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">value</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在Java9之后，<code>String</code>类的实现改用<code>byte</code>数组存储字符串，同时使用 <code>oder</code>来标识使用了哪种编码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">String</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">implements</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">Serializable</span><span class="p">,</span><span class="w"> </span><span class="n">Comparable</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">CharSequence</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The value is used for character storage. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The identifier of the encoding used to encode the bytes in {@code value}. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">byte</span><span class="w"> </span><span class="n">coder</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><a href="http://openjdk.java.net/jeps/254">那么为什么要改变存储结构呢？</a>
+官方的解释：</p>
+<blockquote>
+<p>The current implementation of the String class stores characters in a char array, using two bytes (sixteen bits) for each character.
+Data gathered from many different applications indicates that strings are a major component of heap usage and,
+moreover, that most String objects contain only Latin-1 characters. Such characters require only one byte of storage,
+hence half of the space in the internal char arrays of such String objects is going unused.<br>
+We propose to change the internal representation of the String class from a UTF-16 char array to a byte array plus an encoding-flag field.
+The new String class will store characters encoded either as ISO-8859-1/Latin-1 (one byte per character),
+or as UTF-16 (two bytes per character), based upon the contents of the string.
+The encoding flag will indicate which encoding is used.</p>
+</blockquote>
+<p>文档大意：<code>String</code>类的当前实现将字符存储在<code>char</code>数组中，每个字符使用两个字节(16位)。
+从许多不同的应用程序收集的数据表明，字符串是堆使用的主要组成部分，而且大多数字符串对象只包含拉丁字符。
+这些字符只需要一个字节的存储空间，因此这些字符串对象的内部<code>char</code>数组中有一半的空间将不会使用。</p>
+<p>我们建议将<code>String</code>类的内部表示从<code>UTF-16</code>字符数组更改为一个字节数组加上一个编码标志字段。
+新的<code>String</code>类将根据字符串的内容存储编码为<code>ISO-8859-1/Latin-1</code>(每个字符一个字节)或<code>UTF-16</code>(每个字符两个字节)的字符。
+编码标志将指示所使用的编码。</p>
+<p>简单说来就是用<code>char</code>数组存，有些数据占不了两个字节，所以为了节约资源改成<code>byte</code>数组存放。
+如果存放的不是拉丁文则需要占两个字节，所以还需要加上编码标记。
+基于<code>String</code>的数据结构，<code>StringBuffer</code>和<code>StringBuilder</code>也同样做了修改。</p>
+<h3 id="不可变性">不可变性</h3>
+<p><code>String</code>类型具有不可变性，因为底层存储的value数组被声明为<code>final</code>，这意味着value数组初始化之后就不能再引用其它数组。
+<code>String</code>是Java中一个不可变的类，所以一旦一个string对象在内存中被创建出来，他就无法被修改。</p>
+<p>下面代码说明String是不可变的：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;good&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">char</span><span class="w"> </span><span class="o">[]</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="sc">&#39;t&#39;</span><span class="p">,</span><span class="sc">&#39;e&#39;</span><span class="p">,</span><span class="sc">&#39;s&#39;</span><span class="p">,</span><span class="sc">&#39;t&#39;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">change</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;test ok&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="w"> </span><span class="s">&#34;chanage方法里str=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">str</span><span class="p">);</span><span class="w"> </span><span class="c1">// chanage方法里str=test ok</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ch</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">&#39;b&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MainTest</span><span class="w"> </span><span class="n">ex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MainTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ex</span><span class="p">.</span><span class="na">change</span><span class="p">(</span><span class="n">ex</span><span class="p">.</span><span class="na">str</span><span class="p">,</span><span class="w"> </span><span class="n">ex</span><span class="p">.</span><span class="na">ch</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">ex</span><span class="p">.</span><span class="na">str</span><span class="p">);</span><span class="w"> </span><span class="c1">// good</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">ex</span><span class="p">.</span><span class="na">ch</span><span class="p">);</span><span class="c1">// best</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>String</code>类的所有方法都没有改变字符串本身的值，都是返回了一个新的对象，那么为什么要把<code>String</code>类设计成不可变的呢？</p>
+<ol>
+<li>字符串不可变的根本原因我认为应是出于对数据的安全性考虑。<code>String</code>经常作为参数，<code>String</code>不可变性可以保证参数不可变。
+实际项目中会用到，比如数据库连接串、账号、密码等字符串，只有不可变的连接串、用户名和密码才能保证安全性。</li>
+<li>线程安全。字符串在Java中的使用频率可谓高之又高，那在高并发的情况下不可变性也使得对字符串的读写操作不用考虑多线程竞争的情况。
+不可变的字符串在多线程环境中是安全的。由于<code>String</code>对象一旦创建就不能被修改，因此多个线程可以安全地共享相同的<code>String</code>实例，而不需要担心数据被修改。</li>
+<li><code>String</code>常量池的需要。字符串常量池的基础就是字符串的不可变性，如果字符串是可变的，那想一想，常量池就没必要存在了。
+如果一个<code>String</code> 对象已经被创建过了，那么就会从<code>String</code>常量池中取得引用。只有<code>String</code>是不可变的，才可能使用 字符串常量池。</li>
+<li>可以缓存<code>hash</code>值。因为<code>String</code>的<code>hash</code>值经常被使用，像<code>Set</code>、<code>Map</code>结构中的<code>key</code>值也需要用到<code>HashCode</code>来保证唯一性和一致性，因此不可变的<code>HashCode</code>才是安全可靠的。</li>
+</ol>
+<h3 id="new-stringabc会创建几个对象">new String(&ldquo;abc&rdquo;)会创建几个对象</h3>
+<p><code>new String(&quot;abc&quot;)</code>会创建几个对象？ 这是面试中经常问的一个问题，先说答案两个字符串对象，前提是<code>String</code>常量池中还没有 &ldquo;abc&rdquo; 字符串对象。
+第一个对象是&quot;abc&quot;，它属于字符串字面量，因此编译时期会在字符串常量池中创建一个字符串对象，指向这个 &ldquo;abc&rdquo; 字符串字面量，而使用<code>new</code>的方式会在堆中创建一个字符串对象。</p>
+<p>来证明一下，到底是不是创建了两个对象，先看一下JDK8 中<code>new String()</code>源代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Initializes a newly created {@code String} object so that it represents
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * the same sequence of characters as the argument; in other words, the
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * newly created string is a copy of the argument string. Unless an
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * explicit copy of {@code original} is needed, use of this constructor is
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * unnecessary since Strings are immutable.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">String</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">original</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">this</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">hash</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>文档注释大意：初始化新创建的<code>String</code>对象，使其表示与实参相同的字符序列，换句话说，新创建的字符串是实参字符串的副本。
+除非需要显式复制形参的值，否则没有必要使用这个构造函数，因为字符串是不可变的。</p>
+<p>用字节码看一下，创建一个测试类，其<code>main</code>方法中使用这种方式来创建字符串对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;abc&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>使用<code>javap -verbose</code>命令进行反编译，得到以下内容：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">Constant pool:
+</span></span><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">   #2 = Class              #18            // java/lang/String
+</span></span><span class="line"><span class="cl">   #3 = String             #19            // abc
+</span></span><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">  #18 = Utf8               java/lang/String
+</span></span><span class="line"><span class="cl">  #19 = Utf8               abc
+</span></span><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">  public static void main(java.lang.String[]);
+</span></span><span class="line"><span class="cl">    descriptor: ([Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">    flags: ACC_PUBLIC, ACC_STATIC
+</span></span><span class="line"><span class="cl">    Code:
+</span></span><span class="line"><span class="cl">      stack=3, locals=2, args_size=1
+</span></span><span class="line"><span class="cl">         0: new           #2                  // class java/lang/String
+</span></span><span class="line"><span class="cl">         3: dup
+</span></span><span class="line"><span class="cl">         4: ldc           #3                  // String abc
+</span></span><span class="line"><span class="cl">         6: invokespecial #4                  // Method java/lang/String.&#34;&lt;init&gt;&#34;:(Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">         9: astore_1
+</span></span><span class="line"><span class="cl">// ...
+</span></span></code></pre></div><p>在<code>Constant Pool</code>中，<code>#19</code>存储这字符串字面量<code>&quot;abc&quot;</code>，<code>#3</code>是<code>String Pool</code>的字符串对象，它指向<code>#19</code>这个字符串字面量。
+在<code>main</code>方法中，<code>0:</code>行使用<code>new #2</code>在堆中创建一个字符串对象，并且使用<code>ldc #3</code>将<code>String Pool</code>中的字符串对象作为<code>String</code>构造函数的参数。
+所以能看到使用<code>new String()</code>的方式创建字符串是创建两个对象。</p>
+<p>那么使用<code>new String(&quot;a&quot;) + new String(&quot;b&quot;)</code>会创建几个对象？会创建6个对象：</p>
+<ul>
+<li>对象1：因为存在用&quot;+&ldquo;连接，所以从字节码角度分析会产生<code>new StringBuilder()</code>对象；</li>
+<li>对象2：<code>new String(&quot;a&quot;)</code>会从堆空间创建一个对象；</li>
+<li>对象3：常量池的a；</li>
+<li>对象4：<code>new String(&quot;b&quot;)</code>会从堆空间创建一个对象；</li>
+<li>对象5：常量池的b；</li>
+<li>对象6：从字节码角度分析，通过<code>new StringBuilder().append()</code>添加完字符串后，会通过<code>StringBuilder.toString()</code>中会创建一个 <code>new String(&quot;ab&quot;)</code>，但是调用<code>toString()</code>方法，不会在常量池中生成ab字符串；</li>
+</ul>
+<h3 id="字符串常量池">字符串常量池</h3>
+<p>在JVM中，为了减少相同的字符串的重复创建，为了达到节省内存的目的，会单独开辟一块内存，用于保存字符串常量，这个内存区域被叫做字符串常量池。
+字符串常量池保存着所有字符串字面量，这些字面量在编译时期就被确定。</p>
+<p>字符串常量池不同版本JDK中位置是不一样的，Java6及以前，字符串常量池存放在永久代，Java7将字符串常量池的位置调整到Java堆内。
+那么字符串常量池为什么要调整位置？</p>
+<p>是为了优化内存管理和避免特定情况下的内存溢出问题。
+在早期的Java版本（如JDK 6及之前），字符串常量池通常是存放在永久代，GC对永久代的回收效率很低，只有在<code>Full GC</code>的时候才会触发，这就导致字符串常量池回收效率不高。
+而我们开发过程中，使用频率比较高，会有大量的字符串被创建，如果无法及时回收，容易导致永久代内存不足。所以JDK7之后将字符串常量池放到堆里，能及时回收内存，避免出现<code>OOM</code>错误。</p>
+<p>如何证明Java8中的字符串常量池方到了堆中？代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 虚拟机参数： -Xmx6m -Xms6m -XX:MetaspaceSize=10m -XX:MaxMetaspaceSize=10m</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashSet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">short</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">hashSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="o">++</span><span class="p">).</span><span class="na">intern</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>抛出异常证明Java8中的字符串常量池方到了堆中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">Exception in thread &#34;main&#34; java.lang.OutOfMemoryError: Java heap space
+</span></span></code></pre></div><p>关于JDK1.6、JDK1.7字符串常量池，有一道相关的面试题。下列代码在JDK1.6、JDK1.7中执行结果不同：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w"> </span><span class="c1">// ==&gt; new String(&#34;11&#34;); 并不会在字符串常量池创建 &#34;11&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 在JDK7及之后，JVM为了节省空间进行优化，在字符串常量池中的对象只保存了堆中对象的地址，而并不是创建了一个真正的对象；</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// &#34;11&#34;不在字符串常量池中 ，把&#34;11&#34;放入字符串常量池中 因为堆中已经存在对象，JDK6在字符串池中保存的是一个真正的对象 JDK7保存的是一个引用地址</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s3</span><span class="p">.</span><span class="na">intern</span><span class="p">();</span><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取字符串常量池的引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;11&#34;</span><span class="p">;</span><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s3</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s4</span><span class="p">);</span><span class="w"> </span><span class="c1">// JDK1.6: false   JDK1.7: true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在JDK1.7及之后，<code>new String(&quot;1&quot;)</code>会在堆中创建一个对象并且会在字符串常量池中创建一个对象。
+因为在堆中已经创建了对象，JVM为了节省空间，在字符串常量池中的对象只保留了引用堆中对象的地址，而并不是创建了一个真正的对象，所以就会出现<code>true</code>的情况。
+JDK1.6创建对象被放在了永久区中的字符串常量池，而并非堆中，JVM无法对其进行优化，所以是<code>false</code>。</p>
+<p>JDK1.6中，将这个字符串对象尝试放入字符串常量池：</p>
+<ul>
+<li>如果串池中有，则并不会放入，并返回已有的串池中的对象的地址；</li>
+<li>如果没有，会把此<strong>对象复制一份，放入串池</strong>，并返回串池中的对象地址；</li>
+</ul>
+<p><img alt="JDK6字符串常量池案例解析" src="/iblog/posts/annex/images/essays/JDK6%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%B8%B8%E9%87%8F%E6%B1%A0%E6%A1%88%E4%BE%8B%E8%A7%A3%E6%9E%90.png"></p>
+<p>JDK1.7起，将这个字符串对象尝试放入字符串常量池：</p>
+<ul>
+<li>如果串池中有，则并不会放入，并返回已有的串池中的对象的地址；</li>
+<li>如果没有，则会把<strong>对象的引用地址复制一份，放入串池</strong>，并返回串池中的引用地址；</li>
+</ul>
+<p><img alt="JDK78字符串常量池案例解析" src="/iblog/posts/annex/images/essays/JDK78%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%B8%B8%E9%87%8F%E6%B1%A0%E6%A1%88%E4%BE%8B%E8%A7%A3%E6%9E%90.png"></p>
+<h4 id="intern方法">intern方法</h4>
+<p>在Java中，字符串常量池是由JVM自动管理的，开发者通常不需要显式地将字符串加入到字符串常量池中。
+Java中的字符串常量池有以下几种方式来存储字符串：</p>
+<ul>
+<li>直接量赋值: 当代码中直接使用双引号定义字符串时，例如 &ldquo;hello&rdquo;，这个字符串常量会自动被加入到字符串常量池中。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;hello&#34;</span><span class="p">;</span><span class="w"> </span><span class="c1">// &#34;hello&#34;会被加入字符串常量池</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;hel&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;lo&#34;</span><span class="p">;</span><span class="w"> </span><span class="c1">// 编译器会将&#34;hel&#34; + &#34;lo&#34;优化为&#34;hello&#34;，并将&#34;hello&#34;放入字符串常量池</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>调用String类的<code>intern()</code>方法：调用这个方法可以将字符串添加到字符串常量池中，并返回常量池中字符串的引用。
+如果字符串常量池中已经存在相同内容的字符串，则返回常量池中字符串的引用。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">).</span><span class="na">intern</span><span class="p">();</span><span class="w"> </span><span class="c1">// 将字符串&#34;hello&#34;添加到字符串常量池，并返回常量池中的引用</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>关于<code>intern</code>是一个<code>native</code>方法，调用的是底层C的方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl"><span class="o">/**</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">Returns</span> <span class="n">a</span> <span class="n">canonical</span> <span class="n">representation</span> <span class="k">for</span> <span class="n">the</span> <span class="n">string</span> <span class="n">object</span><span class="o">.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">p</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">A</span> <span class="n">pool</span> <span class="n">of</span> <span class="n">strings</span><span class="p">,</span> <span class="n">initially</span> <span class="n">empty</span><span class="p">,</span> <span class="n">is</span> <span class="n">maintained</span> <span class="n">privately</span> <span class="n">by</span> <span class="n">the</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="k">class</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="ne">String</span><span class="p">}</span><span class="o">.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">p</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">When</span> <span class="n">the</span> <span class="n">intern</span> <span class="n">method</span> <span class="n">is</span> <span class="n">invoked</span><span class="p">,</span> <span class="k">if</span> <span class="n">the</span> <span class="n">pool</span> <span class="n">already</span> <span class="n">contains</span> <span class="n">a</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">string</span> <span class="n">equal</span> <span class="n">to</span> <span class="n">this</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="ne">String</span><span class="p">}</span> <span class="n">object</span> <span class="n">as</span> <span class="n">determined</span> <span class="n">by</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">the</span> <span class="p">{</span><span class="err">@</span><span class="n">link</span> <span class="c1">#equals(Object)} method, then the string from the pool is</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">returned</span><span class="o">.</span> <span class="n">Otherwise</span><span class="p">,</span> <span class="n">this</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="ne">String</span><span class="p">}</span> <span class="n">object</span> <span class="n">is</span> <span class="n">added</span> <span class="n">to</span> <span class="n">the</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">pool</span> <span class="ow">and</span> <span class="n">a</span> <span class="n">reference</span> <span class="n">to</span> <span class="n">this</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="ne">String</span><span class="p">}</span> <span class="n">object</span> <span class="n">is</span> <span class="n">returned</span><span class="o">.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">p</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">It</span> <span class="n">follows</span> <span class="n">that</span> <span class="k">for</span> <span class="n">any</span> <span class="n">two</span> <span class="n">strings</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="n">s</span><span class="p">}</span> <span class="ow">and</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="n">t</span><span class="p">},</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="n">s</span><span class="o">.</span><span class="n">intern</span><span class="p">()</span> <span class="o">==</span> <span class="n">t</span><span class="o">.</span><span class="n">intern</span><span class="p">()}</span> <span class="n">is</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="bp">true</span><span class="p">}</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="k">if</span> <span class="ow">and</span> <span class="n">only</span> <span class="k">if</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="n">s</span><span class="o">.</span><span class="n">equals</span><span class="p">(</span><span class="n">t</span><span class="p">)}</span> <span class="n">is</span> <span class="p">{</span><span class="err">@</span><span class="n">code</span> <span class="bp">true</span><span class="p">}</span><span class="o">.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">p</span><span class="o">&gt;</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">All</span> <span class="n">literal</span> <span class="n">strings</span> <span class="ow">and</span> <span class="n">string</span><span class="o">-</span><span class="n">valued</span> <span class="n">constant</span> <span class="n">expressions</span> <span class="n">are</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="n">interned</span><span class="o">.</span> <span class="ne">String</span> <span class="n">literals</span> <span class="n">are</span> <span class="n">defined</span> <span class="ow">in</span> <span class="n">section</span> <span class="mf">3.10</span><span class="o">.</span><span class="mi">5</span> <span class="n">of</span> <span class="n">the</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*</span> <span class="o">&lt;</span><span class="n">cite</span><span class="o">&gt;</span><span class="n">The</span> <span class="n">Java</span><span class="o">&amp;</span><span class="n">trade</span><span class="p">;</span> <span class="n">Language</span> <span class="n">Specification</span><span class="o">&lt;/</span><span class="n">cite</span><span class="o">&gt;.</span>
+</span></span><span class="line"><span class="cl"> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl"><span class="n">public</span> <span class="n">native</span> <span class="ne">String</span> <span class="n">intern</span><span class="p">();</span>
+</span></span></code></pre></div><p><code>intern</code>方法文档注释大意是：字符串池最初是空的，由String类私有地维护。
+在调用<code>intern</code>方法时，如果池中已经包含了由<code>equals(object)</code>方法确定的与该字符串对象相等的字符串，则返回池中的字符串。
+否则，该字符串对象将被添加到池中，并返回对该字符串对象的引用。</p>
+<p>下面示例中s1和s2采用<code>new String()</code>的方式新建了两个不同字符串，而s3和s4是通过<code>s1.intern()</code>方法取得一个字符串引用。
+<code>intern()</code>首先把s1引用的字符串放到<code>String Pool</code>中，然后返回这个字符串引用，因此s3和s4引用的是同一个字符串。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;aaa&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;aaa&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s2</span><span class="p">);</span><span class="w">           </span><span class="c1">// false</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">intern</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">s4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">intern</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s3</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s4</span><span class="p">);</span><span class="w">           </span><span class="c1">// true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>对于程序中大量使用存在的字符串时，尤其存在很多已经重复的字符串时，使用<code>intern()</code>方法能够节省内存空间。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">MAX_COUNT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1000</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">10000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[</span><span class="n">MAX_COUNT</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="w"> </span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="o">[]</span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="p">,</span><span class="n">6</span><span class="p">,</span><span class="n">7</span><span class="p">,</span><span class="n">8</span><span class="p">,</span><span class="n">9</span><span class="p">,</span><span class="n">10</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAX_COUNT</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//            arr[i] = new String(String.valueOf(data[i%data.length])); // 花费的时间为：3074</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">data</span><span class="o">[</span><span class="n">i</span><span class="o">%</span><span class="n">data</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">)).</span><span class="na">intern</span><span class="p">();</span><span class="w"> </span><span class="c1">// 花费的时间为：1196</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;花费的时间为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">end</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">start</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">getStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">gc</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>不使用<code>intern</code>方法
+<img alt="不用intern方法测试" src="/iblog/posts/annex/images/essays/%E4%B8%8D%E7%94%A8intern%E6%96%B9%E6%B3%95%E6%B5%8B%E8%AF%95.png"></p>
+<p>使用<code>intern</code>方法后
+<img alt="使用intern方法测试" src="/iblog/posts/annex/images/essays/%E4%BD%BF%E7%94%A8intern%E6%96%B9%E6%B3%95%E6%B5%8B%E8%AF%95.png"></p>
+<h4 id="字符串常量池长度">字符串常量池长度</h4>
+<p>字符串常量池是不会存储相同内容的字符串的，字符串常量池其实是一个固定大小的<code>Hashtable</code>。
+如果放进字符串常量池的字符串非常多，就会造成Hash冲突严重，从而导致链表会很长，而链表长了后直接会造成的影响就是当调用<code>String.intern()</code>时性能会大幅下降。</p>
+<p>使用参数<code>-XX:StringTablesize</code>可设置字符串常量池的的长度，可以配置不同版本的Java，运行下列代码，使用命令进行查看<code>stringTableSize</code>大小：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">jsp(获取程序进程ID) -&gt; jinfo -flag StringTableSize 进程ID
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>不同JDK版本字符串常量池的的长度：</p>
+<ul>
+<li>在JDK6中<code>stringTable</code>是固定的，为1009的长度，所以如果常量池中的字符串过多就会导致效率下降很快。<code>-XX:StringTablesize</code>设置没有要求，可随意设置；</li>
+<li>在JDK7中，<code>stringTable</code>的长度默认值是60013，<code>-XX:StringTablesize</code>设置没有要求，可随意设置；</li>
+<li>在JDK8中，<code>stringTable</code>的长度默认为 60013，但不能低于 1009。</li>
+</ul>
+<h3 id="使用">使用</h3>
+<h4 id="创建字符串">创建字符串</h4>
+<p>创建字符串，常见的大概有这么几种方式：</p>
+<ol>
+<li><code>String</code>直接创建
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>String</code>对象创建
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&#34;123&#34;</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>String</code>引用创建
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str1</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>格式化创建字符串
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;浮点型变量: %f, 整型变量: %d, 字符串变量: %s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">.</span><span class="na">0f</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<p>所有<code>String</code>对象都是不可变的，一旦创建，其内容不能改变，这使得字符串在多线程环境中是安全的。
+通过字面量的方式创建给一个字符串赋值，存储在字符串常量池中，而<code>new</code>创建的字符串对象在堆上。</p>
+<h4 id="拼接字符串">拼接字符串</h4>
+<p>因为<code>String</code>类是不可变的，所以所谓字符串拼接，都是重新生成了一个新的字符串。
+以下是字符串的几种拼接的方式：</p>
+<ol>
+<li>使用<code>concat</code>方法连接字符串
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">.</span><span class="na">concat</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str2</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>用&rdquo;+&ldquo;连接字符串
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 在编译时会编译成 String str4 = &#34;123456&#34;;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;456&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 会调用StringBuilder.append方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;789&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str4</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>用JDK内置处理字符串类<code>Stringbuilder</code>, <code>StringBuffer</code>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">StringBuilder</span><span class="w"> </span><span class="n">builder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">StringBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuffer</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">builder</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">str</span><span class="p">).</span><span class="na">append</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">).</span><span class="na">toString</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">str</span><span class="p">).</span><span class="na">append</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">).</span><span class="na">toString</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str6</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>Java8新增<code>String.join</code>方法连接字符串
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str7</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">join</span><span class="p">(</span><span class="s">&#34;-&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str8</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">join</span><span class="p">(</span><span class="s">&#34;~&#34;</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[]</span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="s">&#34;3&#34;</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str7</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str8</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>用第三方处理字符串工具类，例如: <code>apache.commons</code>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// Java8提供的String.join方法和`apache.commons`方法相似.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 主要作用是将数组或集合以某拼接符拼接到一起形成新的字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">str9</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StringUtils</span><span class="p">.</span><span class="na">join</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[]</span><span class="p">{</span><span class="n">str</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;456&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;789&#34;</span><span class="p">});</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<p>如果在处理大量字符串的时候就需要注意性能和耗时，以下是耗时比较(短-&gt;长)：<code>StringBuilder</code>&lt;<code>StringBuffer</code>&lt;<code>concat</code>&lt;<code>+</code>&lt;<code>StringUtils.join</code> 。</p>
+<h4 id="拼接原理">“+”拼接原理</h4>
+<p>拼接字符串最简单的方式就是直接使用符号&rdquo;+&ldquo;来拼接，其实“+”是Java提供的一个语法糖。
+语法糖（Syntactic sugar），也译为糖衣语法，是由英国计算机科学家彼得·兰丁发明的一个术语，指计算机语言中添加的某种语法，这种语法对语言的功能没有影响，但是更方便程序员使用。
+语法糖让程序更加简洁，有更高的可读性。</p>
+<p>为了探究“+”拼接的原理，用<code>javap -verbose</code>命令进行反编译看一下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;456&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">str2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">  public static void main(java.lang.String[]);
+</span></span><span class="line"><span class="cl">    descriptor: ([Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">    flags: ACC_PUBLIC, ACC_STATIC
+</span></span><span class="line"><span class="cl">    Code:
+</span></span><span class="line"><span class="cl">      stack=2, locals=4, args_size=1
+</span></span><span class="line"><span class="cl">         0: ldc           #2                  // String 123
+</span></span><span class="line"><span class="cl">         2: astore_1
+</span></span><span class="line"><span class="cl">         3: ldc           #3                  // String 456
+</span></span><span class="line"><span class="cl">         5: astore_2
+</span></span><span class="line"><span class="cl">         6: new           #4                  // class java/lang/StringBuilder
+</span></span><span class="line"><span class="cl">         9: dup
+</span></span><span class="line"><span class="cl">        10: invokespecial #5                  // Method java/lang/StringBuilder.&#34;&lt;init&gt;&#34;:()V
+</span></span><span class="line"><span class="cl">        13: aload_1
+</span></span><span class="line"><span class="cl">        14: invokevirtual #6                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
+</span></span><span class="line"><span class="cl">        17: aload_2
+</span></span><span class="line"><span class="cl">        18: invokevirtual #6                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
+</span></span><span class="line"><span class="cl">        21: invokevirtual #7                  // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
+</span></span><span class="line"><span class="cl">        24: astore_3
+</span></span><span class="line"><span class="cl">        25: getstatic     #8                  // Field java/lang/System.out:Ljava/io/PrintStream;
+</span></span><span class="line"><span class="cl">        28: aload_3
+</span></span><span class="line"><span class="cl">        29: invokevirtual #9                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">        32: return
+</span></span><span class="line"><span class="cl">      // ...
+</span></span></code></pre></div><p>可以看到在字符串拼接过程中，是将<code>String</code>转成了<code>StringBuilder</code>后，使用<code>append</code>方法进行拼接字符串处理的，最后在去调用<code>StringBuilder</code>的<code>toString</code>方法进行返回。
+在JDK5之后，使用的是<code>StringBuilder</code>，在JDK5之前使用的是<code>StringBuffer</code>。</p>
+<p>知道了“+”底层之后，如果在循环中，使用“+”拼接字符串，会创建大量的<code>StringBuilder</code>对象，造成内存的浪费。
+所以对于大量字符串拼接操作，推荐使用<code>StringBuilder</code>或<code>StringBuffer</code>以提高性能。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 不推荐</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">StringConcatExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">result</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">length</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 推荐</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">StringBuilderExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">result</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">length</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="stringbuffer与stringbuilder">StringBuffer与StringBuilder</h4>
+<p><code>Stringbuilder</code>和<code>StringBuffer</code>是字符串拼接的两种实现类，它们有相同的父类：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractStringBuilder</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Appendable</span><span class="p">,</span><span class="w"> </span><span class="n">CharSequence</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * The value is used for character storage.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * The count is the number of characters used.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>StringBuffer</code>和<code>StringBuilder</code>是 Java 提供的用于处理字符串的类，二者的主要区别在于线程安全性和性能方面。拿<code>append</code>方法举例：</p>
+<ul>
+<li><code>StringBuilder.append</code>方法
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">StringBuilder</span><span class="w"> </span><span class="nf">append</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">str</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>StringBuffer.append</code>方法
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">  </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="n">StringBuffer</span><span class="w"> </span><span class="nf">append</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">toStringCache</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="kd">super</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">str</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>由此可以看出<code>StringBuilder</code>和<code>StringBuffer</code>原理是相似的，最大的区别就是<code>StringBuffer</code>是线程安全的，原因是用了<code>synchronized</code>修饰。
+<code>StringBuffer</code>是线程安全的，因为它的方法都是同步的，这意味着它是安全的，可以在多线程环境中使用。
+由于其线程安全性，每个方法调用都有同步开销，所以<code>StringBuffer</code>的性能比<code>StringBuilder</code>稍慢。</p>
+<p>与<code>String</code>类不同的是，<code>StringBuffer</code>和<code>StringBuilder</code>类的对象能够被多次的修改，并且不产生新的未使用对象。
+如果你需要一个可修改的字符串，应该使用<code>StringBuffer</code>或者<code>StringBuilder</code>，但是会有大量时间浪费在垃圾回收上，因为每次试图修改都有新的<code>String</code>对象被创建出来。</p>
+<p>通过<code>StringBuilder</code>的<code>append()</code>方式添加字符串的效率，要远远高于<code>String</code>的字符串拼接方法。
+在实际开发中还可以进行优化，<code>StringBuilder</code>的空参构造器，默认的字符串容量是16，如果需要存放的数据过多，容量就会进行扩容，我们可以设置默认初始化更大的长度，来减少扩容的次数。
+如果我们能够确定，前前后后需要添加的字符串不高于某个限定值，那么建议使用构造器创建一个阈值的长度。</p>
+<h4 id="常用方法">常用方法</h4>
+<p>基于Java8整理，如果查看其他方法请参照<a href="https://docs.oracle.com/javase/8/docs/api/index.html">Java8API官方文档</a>。</p>
+<ul>
+<li><code>substring</code>对字符串进行截取.返回一个新的字符串，它是此字符串的一个子字符串；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123456&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">substring</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 3456</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">substring</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 索引从1开始截取字符串</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">substring2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 34</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">substring2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>replace</code>替换字符串.返回一个新的字符串，它是通过用 <code>newChar</code> 替换此字符串中出现的所有 <code>oldChar</code> 得到的；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123456&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 223456</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str</span><span class="p">.</span><span class="na">replace</span><span class="p">(</span><span class="sc">&#39;1&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;2&#39;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>replaceAll</code>使用给定的 <code>replacement</code> 替换此字符串所有匹配给定的正则表达式的子字符串；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;111111&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 222222</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str</span><span class="p">.</span><span class="na">replaceAll</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>valueOf</code>该方法作用是将对象转成<code>String</code>类型；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Integer</span><span class="w"> </span><span class="n">integer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">11111</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">integer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 11111</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">str</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="长度限制">长度限制</h3>
+<p>Java中的<code>String</code>内部是用一个字符数组<code>char[]</code>存储字符数据的，数组的最大长度限制由Java虚拟机规范决定。
+所以理论上，Java数组的最大长度是<code>Integer.MAX_VALUE(2^31 - 1)</code>，即2147483647，这也是String的长度限制，但在实际操作中，能分配的最大数组长度受可用内存限制。</p>
+<p>但是并不是这样，字符串字面量的长度不能超过65535字符，如果字符串字面量长度超过这个限制，编译器会抛出错误。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkStringConstant</span><span class="p">(</span><span class="n">DiagnosticPosition</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">nerrs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">((</span><span class="n">String</span><span class="p">)</span><span class="n">var2</span><span class="p">).</span><span class="na">length</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">65535</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">log</span><span class="p">.</span><span class="na">error</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;limit.string&#34;</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="o">++</span><span class="k">this</span><span class="p">.</span><span class="na">nerrs</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>还有一点，<code>Stirng</code>长度之所以会受限制，是因JVM规范对常量池有所限制。
+<a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.7">CONSTANT_Utf8_info</a>是一个<code>CONSTANT_Utf8</code>类型的常量池数据项，它存储的是一个常量字符串。
+常量池中的所有字面量几乎都是通过<code>CONSTANT_Utf8_info</code>描述的，<code>CONSTANT_Utf8_info</code>的定义如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">ONSTANT_Utf8_info {
+</span></span><span class="line"><span class="cl">    u1 tag;
+</span></span><span class="line"><span class="cl">    u2 length;
+</span></span><span class="line"><span class="cl">    u1 bytes[length];
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><ul>
+<li><code>tag</code>：<code>CONSTANT_Utf8_info</code>结构的标记项值为<code>CONSTANT_Utf8(1)</code>；</li>
+<li><code>length</code>：<code>length</code>项的值表示字节数组中的字节数，而不是结果字符串的长度，其类型为<code>u2</code>；</li>
+<li><code>bytes[]</code>：字节数组包含字符串的字节数；</li>
+</ul>
+<p>到了这里长度终于出来了，那就是<code>length</code>。通过查阅《JVM规范》发现<code>u2</code>表示两个字节的无符号数，那么1个字节有8位，2个字节就有16位。
+16位无符号数可表示的最大值位<code>2^16 - 1 = 65535</code>。也就是说，<code>Class</code>文件中常量池的格式规定了，每个字符串常量的最大长度为65535字节。</p>
+<p>所以对<code>String</code>的长度限制主要有两点：</p>
+<ol>
+<li><code>Class</code>文件中常量池的格式规定了，每个字符串常量的最大长度为65535字节；</li>
+<li><code>checkStringConstant</code>方法，规定字符串字面量的长度不能超过65535字符，即最大65534个字符；</li>
+</ol>
+<p>所以一个字符串字面量最多可以包含65534个字符，但它的存储空间（字节数）并不会超过65535字节。</p>
+<p>那么<code>String</code>类长度限制是多少？</p>
+<ul>
+<li>在编译期间，长度不能超过65535个字符，即最大65534个字符，但65534个字符存储空间不会超过65535字节；</li>
+<li>在运行期，<code>String</code>对象的长度理论上可以达到<code>Integer.MAX_VALUE (2^31 - 1)</code>个字符，即 2,147,483,647 个字符，大概4G。
+在实际应用中，字符串的最大长度受限于可用内存和JVM配置；</li>
+</ul>
+<p>在程序开发中，如果用<code>String</code>变量接收<code>Base64</code>图片或音频视频，需要注意不要超过程序运行时字符串的最大阈值。</p>
+<h3 id="string类与编码">String类与编码</h3>
+<p>Java中的<code>String</code>类是基于<code>Unicode</code>字符集设计的，它可以存储任意<code>Unicode</code>字符。
+<code>Unicode</code>为世界上几乎所有的字符集提供了唯一的标识码，因此Java的<code>String</code>类可以处理多语言字符和符号。</p>
+<h4 id="unicode">Unicode</h4>
+<p><code>Unicode</code>（中文：万国码、国际码、统一码、单一码）是计算机科学领域里的一项业界标准。
+它对世界上大部分的文字系统进行了整理、编码，使得计算机可以用更为简单的方式来呈现和处理文字。</p>
+<p><code>Unicode</code>伴随着通用字符集的标准而发展，同时也以书本的形式对外发表。<code>Unicode</code>至今仍在不断增修，每个新版本都加入更多新的字符。
+目前最新的版本为2018年6月5日公布的11.0.0，已经收录超过13万个字符（第十万个字符在2005年获采纳）。
+<code>Unicode</code>涵盖的数据除了视觉上的字形、编码方法、标准的字符编码外，还包含了字符特性，如大小写字母。</p>
+<p><code>Unicode</code>是一种编码规范，是为解决全球字符通用编码而设计的，而<code>UTF-8</code>、<code>UTF-16</code>等是这种规范的一种实现，<code>Unicode</code>是字符集而<code>UTF-8</code>是编码规则。
+在Java虚拟机内部，<code>String</code>对象的存储是以<code>UTF-16</code>编码形式进行的。<code>UTF-16</code>编码是一种<code>Unicode</code>字符集的编码方式，它采用16位（即2个字节）编码单元来表示大部分字符，辅助字符则需要使用4个字节来表示。</p>
+<p>不管程序过程中用到了<code>GBK</code>还是<code>ISO8859-1</code>等格式，在存储与传递的过程中实际传递的都是<code>Unicode</code>编码的数据，要想接收到的值不出现乱码，就要保证传过去的时候用的是X编码，接收的时候也用X编码来转换接收。</p>
+<h4 id="编码与解码">编码与解码</h4>
+<p>字符串的编码和解码在Java中是非常常见和重要的操作，特别是在处理文件、网络通信或与外部系统交互时。</p>
+<ul>
+<li>编码是将字符串转换为字节序列的过程；</li>
+<li>解码是将字节序列转换为字符串的过程；</li>
+</ul>
+<p>字符串的编码和解码代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">StringEncodingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">originalString</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello, 你好&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">charsetName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;UTF-8&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编码：String -&gt; byte[]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">utf8Bytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">originalString</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(</span><span class="n">charsetName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Encoded UTF-8 bytes: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">bytesToHex</span><span class="p">(</span><span class="n">utf8Bytes</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 解码：byte[] -&gt; String</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">decodedString</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="n">utf8Bytes</span><span class="p">,</span><span class="w"> </span><span class="n">charsetName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Decoded String: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">decodedString</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">UnsupportedEncodingException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 辅助方法：将字节数组转换为十六进制字符串表示</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">bytesToHex</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StringBuilder</span><span class="w"> </span><span class="n">sb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuilder</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">bytes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">sb</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;%02X &#34;</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">sb</span><span class="p">.</span><span class="na">toString</span><span class="p">().</span><span class="na">trim</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在解码时，可能会出现乱码，原因是编码时格式和解码时格式不一致导致。
+即在编码时，是用一种编码，而在解码时，用的是另一种编码，所以导致乱码问题。所以想要避免乱码问题最简单的办法就是从始至终，都用同一种字符格式。</p>
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diff --git a/docs/posts/javabasics/rookie-exception/index.html b/docs/posts/javabasics/rookie-exception/index.html
new file mode 100644
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+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%84%e7%90%86%e5%bc%82%e5%b8%b8">
+                    处理异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#try-catch">
+                    try-catch
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#try-catch-finally">
+                    try-catch-finally
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#throwsthrow">
+                    throws、throw
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%82%e5%b8%b8%e9%93%be">
+                    异常链
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%8f%e9%aa%8c%e6%80%bb%e7%bb%93">
+                    经验总结
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%8d%e8%a6%81%e6%bb%a5%e7%94%a8%e5%bc%82%e5%b8%b8">
+                    不要滥用异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%a9%bacatch">
+                    空catch
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%90%9e%e6%8e%89%e5%bc%82%e5%b8%b8">
+                    吞掉异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b2%be%e7%a1%ae%e5%a4%84%e7%90%86%e5%bc%82%e5%b8%b8">
+                    精确处理异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8a%9b%e5%87%ba%e5%bc%82%e5%b8%b8">
+                    抛出异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%89%e6%8b%a9%e5%bc%82%e5%b8%b8">
+                    选择异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%8d%e8%a6%81%e5%9c%a8finally%e4%b8%ad%e6%8a%9b%e5%bc%82%e5%b8%b8">
+                    不要在finally中抛异常
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e8%80%83%e6%96%87%e7%ab%a0">
+                    参考文章
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
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+                <a href="https://whiteppure.github.io/iblog/posts/">归档</a>
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+                <a href="https://whiteppure.github.io/iblog/about/">关于</a>
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+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
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+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="https://whiteppure.github.io/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
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+                
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+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    <a id="export_markdown" title="导出markdown" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    </a>
+                </span>
+                <a  id="icon_more" title="更多" >
+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
+                </a>
+                <a  id="icon_less" class="display_none">
+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
+                
+            </div>
+
+            
+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_uv">访客数 <span id="busuanzi_value_site_uv"></span>人</span>
+                </div>
+            </div>
+            
+        </div>
+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Java异常</h2>
+                        <span id="post_page_title_date" class="date">2021.01.13</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="异常类型">异常类型</h2>
+<p><img alt="Java异常分类" src="/iblog/posts/annex/images/essays/Java%E5%BC%82%E5%B8%B8%E5%88%86%E7%B1%BB.png"></p>
+<p><code>Throwable</code>可以用来表示任何可以作为异常抛出的类，分为两种：<code>Error</code> 和 <code>Exception</code>。
+其中<code>Error</code>用来表示Java程序无法处理的错误，这类错误一般与硬件有关，与程序本身无关，通常由系统进行处理，程序本身无法捕获和处理，是不可控制的。</p>
+<p><code>Exception</code>分为两种：运行时异常和检查型异常。</p>
+<ul>
+<li>受检异常：需要用<code>try...catch... </code>语句捕获并进行处理，并且可以从异常中恢复；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">MyException</span><span class="p">{}</span><span class="w">
+</span></span></span></code></pre></div>Java编译器对检查性异常会要求我们进行<code>catch</code>，必须得进行捕获，否则编译不过去。Java认为检查性异常都可以被处理，所以必须显示的处理<code>checked</code>异常。
+常见的检查性异常有<code>IOException</code>、<code>SqlException</code>。当我们希望我们的⽅法调⽤者，明确的处理⼀些特殊情况的时候，就应该使⽤受检异常。</li>
+<li>非受检异常：是程序运行时错误。例如：除0会引发 <code>ArithmeticException</code>，此时程序崩溃并且无法恢复。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="o">/</span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div>这种异常⼀般可以理解为是代码原因导致的。⽐如发⽣空指针、数组越界等。所以，只要代码写的没问题，这些异常都是可以避免的。也就不需要我们显⽰的进⾏处理。</li>
+</ul>
+<p><code>Exception</code>表⽰程序需要捕捉、需要处理的常，是由与程序设计的不完善⽽出现的问题，程序必须处理的问题。
+异常和错误的区别是，异常能被程序本身可以处理，错误是无法处理。</p>
+<h2 id="自定义异常">自定义异常</h2>
+<p>在Java中，自定义异常类可以帮助你创建特定于你的应用程序的异常类型，这些异常类型可以提供更清晰的错误描述，并使错误处理更加灵活和精确。
+在Java中自定义异常，但所有自定义异常都必须是<code>Throwable</code>的子类。
+如果希望写一个检查性异常类，则需要继承<code>Exception</code>类。如果你想写一个运行时异常类，那么需要继承<code>RuntimeException</code>类。</p>
+<p>自定义受检查异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 创建一个自定义的受检查异常类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyCheckedException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyCheckedException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyCheckedException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用自定义异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Test</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">MyCheckedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 条件判断或业务逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyCheckedException</span><span class="p">(</span><span class="s">&#34;This is a custom checked exception.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>自定义运行时异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 创建一个自定义的非受检查异常类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyUncheckedException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">RuntimeException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyUncheckedException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyUncheckedException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用自定义异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Test</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 条件判断或业务逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyUncheckedException</span><span class="p">(</span><span class="s">&#34;This is a custom unchecked exception.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="异常的传播">异常的传播</h2>
+<p>在Java中，异常传播指的是当一个方法内部抛出异常时，异常如何在调用栈中向上传播的过程。
+理解异常传播是异常处理机制中的重要部分，对于编写健壮的代码和良好的异常处理策略至关重要。</p>
+<p>当一个方法内部抛出异常时，异常会沿着调用链向上传播给调用者。这个过程描述了异常如何从方法内部向外部传递，并最终在调用栈中找到合适的异常处理器来处理异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExceptionPropagationExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">method1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception caught in main method: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method1</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">method2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">RuntimeException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;RuntimeException caught in method1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method2</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">method3</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method3</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 人为地抛出一个异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">&#34;Exception occurred in method3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>异常传播的基本过程：</p>
+<ol>
+<li>当方法内部抛出一个异常（使用<code>throw</code>关键字），异常对象被创建并包含了当前异常的堆栈信息，包括方法调用路径。</li>
+<li>异常从抛出它的方法开始，沿着方法调用链向上传播。每当方法内部抛出异常时，JVM将控制权传递给调用该方法的上级方法。</li>
+<li>异常会继续沿着调用链向上移动，直到找到合适的异常处理器来处理异常。处理器可以是<code>try-catch</code>块、异常处理方法或者不处理异常而继续向上传播。</li>
+<li>如果找到了与抛出的异常匹配的<code>catch</code>块或者方法签名中声明的<code>throws</code>子句，异常被捕获并在这里进行处理。处理可以包括记录日志、恢复操作或者向上抛出另一个异常。</li>
+<li>如果异常没有在当前方法中被捕获处理，它将继续向上传播，控制权交给调用当前方法的方法。这个过程继续直到异常被捕获或者传播到了调用栈的顶部。</li>
+<li>如果异常传播到了调用栈的顶部仍然没有被处理，通常情况下会导致程序终止，并打印异常的堆栈跟踪信息，这有助于开发人员定位和解决问题。</li>
+</ol>
+<h2 id="处理异常">处理异常</h2>
+<p>异常的处理⽅式有两种，⾃⼰处理，向上抛出交给调⽤者处理。</p>
+<p>需要注意的是，一般情况下不要丢弃异常，捕获异常后需要进行相关处理。
+如果用户觉得不能很好地处理该异常，就让它继续传播，传到别的地方去处理，或者把一个低级的异常转换成应用级的异常，重新抛出。
+千万不能捕获了之后什么也不做，或者只是使⽤<code>e.printStacktrace</code>。如果是练习这样写也就算了，但是在正式的环境上千万不能这样做。实际开发中应该使用日志记录。</p>
+<p>写完代码后请一定要检查下，代码中千万不要有<code>printStackTrace</code>。
+不能直接使用<code>printStackTrace</code>打印异常的原因在于它可能泄露敏感信息、未将异常信息记录到日志系统中、使得错误难以追踪和管理、影响系统性能，并且通常缺乏必要的上下文信息。
+因此，在正式开发中，应使用日志框架记录异常信息，以便更好地监控和调试应用程序。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExceptionHandlingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Logger</span><span class="w"> </span><span class="n">logger</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">LoggerFactory</span><span class="p">.</span><span class="na">getLogger</span><span class="p">(</span><span class="n">ExceptionHandlingExample</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">divide</span><span class="p">(</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 使用日志记录异常信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">logger</span><span class="p">.</span><span class="na">error</span><span class="p">(</span><span class="s">&#34;Division by zero error&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 或者根据业务逻辑重新抛出应用级异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CustomApplicationException</span><span class="p">(</span><span class="s">&#34;Failed to divide numbers&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 自定义应用级异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CustomApplicationException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">RuntimeException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CustomApplicationException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="try-catch">try-catch</h3>
+<p>自己处理异常指在当前方法内部通过<code>try-catch</code>语句捕获并处理异常，而不是将异常传播给调用者处理。
+这种方式适合于可以预见并且能够恢复的异常情况。处理异常的目的是在发生异常时执行某些逻辑，例如提供默认值、记录日志、给用户友好的错误提示等。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExceptionHandlingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">divide</span><span class="p">(</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error: Division by zero is not allowed. Defaulting result to 0.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 给出一个默认值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在Java中，一个<code>try</code>语句可以对应多个<code>catch</code>块来进行多重捕获。
+如果在<code>try</code>语句块中发生异常，异常会被依次传递给每个<code>catch</code>块，直到找到匹配的<code>catch</code>块进行处理。如果没有匹配的<code>catch</code>块，异常会继续向上抛出。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MultiCatchExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">numbers</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">numbers</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">);</span><span class="w"> </span><span class="c1">// ArrayIndexOutOfBoundsException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="c1">// ArithmeticException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArrayIndexOutOfBoundsException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Array index is out of bounds: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Arithmetic error occurred: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;An unexpected error occurred: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>从JDK7开始，Java引入了多个异常类型的合并处理，这使得可以将多个不同类型的异常在一个<code>catch</code>块中捕获和处理。
+这种特性可以减少重复的代码，并提高异常处理的简洁性和可读性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MultiCatchExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">numbers</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">numbers</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">);</span><span class="w"> </span><span class="c1">// ArrayIndexOutOfBoundsException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="c1">// ArithmeticException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArrayIndexOutOfBoundsException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;An error occurred: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;An unexpected error occurred: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="try-catch-finally">try-catch-finally</h3>
+<p><code>try</code> 语句块不止可以与 <code>catch</code> 连用，也可以与<code>finally</code>连用，但是 <code>catch</code> 不能与 <code>finally</code> 连用。
+<code>try-catch-finally</code>结构与异常密切相关，它是Java中用于处理异常的基本结构之一，用于确保资源的正确关闭和异常的正确处理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TryCatchFinallyExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BufferedReader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileReader</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">line</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">line</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">readLine</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">line</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error reading file: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">reader</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">reader</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w"> </span><span class="c1">// 确保关闭资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error closing reader: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>根据JVM规范，如果<code>try</code>语句块里边有返回值则返回<code>try</code>语句块里边的；
+如果<code>try</code>语句块和<code>finally</code>语句块都有<code>return</code>，则忽略<code>try</code>语句块里边的使用<code>finally</code>语句块里边的<code>return</code>；
+<code>finally</code>语句块是在<code>try</code>语句块或者<code>catch</code>语句块中的<code>return</code>语句之前执行的，无论是否发生异常，<code>finally</code>代码块中的代码总会被执行。
+一般情况下如果方法有返回值，切忌不要在<code>finally</code>中写<code>return</code>，这样会使得程序结构变得混乱。</p>
+<blockquote>
+<p><code>finally</code>语句块什么时候不执行？
+如果当一个线程在执行<code>try</code>语句块或者<code>catch</code>语句块时被打断（interrupted）或者被终止（killed）或退出虚拟机(<code>System.exit(0)</code>)，与其相对应的<code>finally</code>语句块可能不会执行。
+还有更极端的情况，就是在线程运行<code>try</code>语句块或者<code>catch</code>语句块时，突然死机或者断电，<code>finally</code>语句块肯定不会执行了。</p>
+</blockquote>
+<p>无论是否发生异常，<code>finally</code>代码块中的代码总会被执行。根据这个特性，<code>finally</code>块确保在代码执行过程中发生异常时，资源得到正确释放，所以经常用来关闭资源。
+自从JDK7之后，支持<code>try-with-resources</code>的写法，这种写法对比之前更清晰、明了：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">InputStream</span><span class="w"> </span><span class="n">in</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;awsl&#34;</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">in</span><span class="p">.</span><span class="na">read</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>JVM先会把<code>try</code>或者<code>catch</code>代码块中的返回值保留，再来执行<code>finally</code>代码块中的语句，等到<code>finally</code>代码块执行完毕之后，在把之前保留的返回值给返回出去。
+这条规则只适用于<code>return</code>和<code>throw</code>语句，不适用于<code>break</code>和<code>continue</code>语句，因为它们根本就没有返回值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// main 代码块中的执行结果为：1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;main 代码块中的执行结果为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">myMethod</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;try 代码块被执行！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="o">++</span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;finally 代码块被执行！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">			</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;finally 代码块中的i = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="throwsthrow">throws、throw</h3>
+<p>向上抛出交给调用者处理，这种方式通过在方法签名中使用<code>throws</code>关键字将异常向上抛出，交由调用该方法的代码处理。适用于方法本身无法或者不适合处理异常的情况。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExceptionHandlingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">process</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">process</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">divide</span><span class="p">(</span><span class="n">10</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ArithmeticException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Caught ArithmeticException: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 处理部分异常逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 可能抛出其他类型的异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Exception</span><span class="p">(</span><span class="s">&#34;A different kind of exception occurred.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">ArithmeticException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>throws</code>用在方法上声明异常，子类继承的时候要继承该异常或者该异常的子类，不处理异常，谁调用该方法谁处理异常。
+<code>throws</code>抛出异常时，它的调用者也要申明抛出异常或者捕获，不然编译报错。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">ArithmeticException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>throw</code>用于方法内部，抛出的是异常对象。调用者可以不申明或不捕获但编译器不会报错。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Error: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>throws</code>表示出现异常的一种可能性，告诉调用者这个方法是危险的，并不一定会发生这些异常。<code>throw</code>则是抛出了异常，执行<code>throw</code>则一定抛出了某种异常对象。
+两者都是消极处理异常的方式（这里的消极并不是说这种方式不好），只是抛出或者可能抛出异常，但是不会由方法去处理异常，真正的处理异常由此方法的上层调用处理。</p>
+<h3 id="异常链">异常链</h3>
+<p>异常链则是一种特定的异常处理技术，通过在捕获异常时将原始异常作为参数传递给新的异常，这样来保留原始异常的详细信息。
+如果因为一个异常你决定抛出⼀个新的异常，⼀定要包含原有的异常，这样处理程序才可以通过<code>getCause</code>方法和<code>initCause</code>⽅法来访问异常最终的根源。
+这样做有助于调试和了解错误的根本原因。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 定义一个自定义异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyCustomException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyCustomException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyCustomException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 一个可能抛出异常的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SomeService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟抛出一个IOException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IOException</span><span class="p">(</span><span class="s">&#34;IO error occurred&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用异常链来包装原始异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SomeService</span><span class="w"> </span><span class="n">service</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SomeService</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">service</span><span class="p">.</span><span class="na">doSomething</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 包装原始异常并抛出新的自定义异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyCustomException</span><span class="p">(</span><span class="s">&#34;Failed to do something due to IO error&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="经验总结">经验总结</h2>
+<p>处理异常是软件开发中至关重要的一部分，有效的异常处理可以提高系统的健壮性、可靠性和用户体验。以下是处理异常的一些经验总结。</p>
+<h3 id="不要滥用异常">不要滥用异常</h3>
+<p>要谨慎地使用异常，异常捕获的代价非常高昂，异常使用过多会严重影响程序的性能。
+如果在程序中能够用<code>if</code>语句和<code>boolean</code>变量来进行逻辑判断，那么尽量减少异常的使用，从而避免不必要的异常捕获和处理。</p>
+<h3 id="空catch">空catch</h3>
+<p>千万不要使用空的<code>catch</code>块：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">try{
+</span></span><span class="line"><span class="cl"> // ...
+</span></span><span class="line"><span class="cl">}catch(IOException e){
+</span></span><span class="line"><span class="cl">  // ...
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在捕获了异常之后什么都不做，相当于忽略了这个异常。空的<code>catch</code>块意味着你在程序中隐藏了错误和异常，并且很可能导致程序出现不可控的执行结果。
+如果你非常肯定捕获到的异常不会以任何方式对程序造成影响，最好用日志将该异常进行记录，以便日后方便更新和维护。</p>
+<h3 id="吞掉异常">吞掉异常</h3>
+<p>请不要在<code>catch</code>块中吞掉异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">catch (NoSuchMethodException e) {
+</span></span><span class="line"><span class="cl">   return null;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>不要不处理异常，而返回<code>null</code>，这样异常就会被吞掉，无法获取到任何失败信息，会给日后的问题排查带来巨大困难。</p>
+<h3 id="精确处理异常">精确处理异常</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public void foo() throws Exception { //错误做法
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>一定要尽量避免上面的代码，因为他的调用者完全不知道错误的原因到底是什么。
+在方法声明中，可以由方法抛出一些特定受检异常。如果有多个，那就分别抛出多个，这样这个方法的使用者才会分别针对每个异常做特定的处理，从而避免发生故障。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">public void foo() throws SpecificException1, SpecificException2 { 
+</span></span><span class="line"><span class="cl">//正确做法
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>同样的在捕获异常时，也要注意，尽量捕获特定的子类，而不是直接捕获<code>Exception</code>类。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    someMethod();
+</span></span><span class="line"><span class="cl">} 
+</span></span><span class="line"><span class="cl">catch (Exception e) {
+</span></span><span class="line"><span class="cl">    log.error(&#34;method has failed&#34;, e);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>上面代码，最大的问题就是，如果<code>someMethod()</code>的开发者在里面新增了一个特定的异常，并且预期是调用方能够特殊的对他进行处理。
+但是调用者直接<code>catch了Exception</code>类，就会导致永远无法知道<code>someMethod</code>的具体变化细节。这久可能导致在运行的过程中在某一个时间点程序崩溃。
+更不要去捕获<code>Throwable</code>类，因为Java中的<code>Error</code>也可以是<code>Throwable</code>的子类。但是<code>Error</code>是Java虚拟机本身无法控制的。Java虚拟机甚至可能不会在出现任何错误时请求用户的<code>catch</code>子句。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    someMethod();
+</span></span><span class="line"><span class="cl">} 
+</span></span><span class="line"><span class="cl">catch (Throwable e) {
+</span></span><span class="line"><span class="cl">    log.error(&#34;method has failed&#34;, e);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p><code>OutOfMemoryError</code>和<code>StackOverflowError</code>便是典型的例子，它们都是由于一些超出应用处理范围的情况导致的。</p>
+<h3 id="抛出异常">抛出异常</h3>
+<p>通常情况下，在捕获异常的时候抛出异常，需要注意的是，要始终在自定义异常中，覆盖原有的异常，从而构成一条异常链，这样堆栈跟踪就不会丢失：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">catch (NoSuchMethodException e) {
+</span></span><span class="line"><span class="cl">    throw new MyServiceException(&#34;Some information: &#34; + e.getMessage());  //错误做法
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>上面的命令可能会丢失掉主异常的堆栈跟踪。正确的方法是：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">catch (NoSuchMethodException e) {
+</span></span><span class="line"><span class="cl">     throw new MyServiceException(&#34;Some information: &#34; , e);  //正确做法
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>需要注意的是，可以记录异常或抛出异常，但不要同时做：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">catch (NoSuchMethodException e) {
+</span></span><span class="line"><span class="cl">   log.error(&#34;Some information&#34;, e);
+</span></span><span class="line"><span class="cl">   throw e;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>抛出和日志记录可能会在日志文件中产生多个日志消息,这就会导致同一个问题，却在日志中有很多不同的错误信息，使得开发人员陷入混乱。</p>
+<h3 id="选择异常">选择异常</h3>
+<p>一旦你决定抛出异常，你就要决定抛出抛出检查异常还是非检查异常。</p>
+<p>检查异常导致了太多的<code>try…catch</code>代码，可能有很多检查异常对开发人员来说是无法合理地进行处理的，比如：<code>SQLException</code>，而开发人员却不得不去进行<code>try…catch</code>，这样就会导致经常出现这样一种情况：逻辑代码只有很少的几行，而进行异常捕获和处理的代码却有很多行。
+这样不仅导致逻辑代码阅读起来晦涩难懂，而且降低了程序的性能。</p>
+<p>建议尽量避免检查异常的使用，如果确实该异常情况出现很的普遍，需要提醒调用者注意处理的话，就使用检查异常；否则使用非检查异常。
+因此，在一般情况下，尽量将检查异常转变为非检查异常交给上层处理。</p>
+<h3 id="不要在finally中抛异常">不要在finally中抛异常</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">  someMethod();  //抛出 exceptionOne
+</span></span><span class="line"><span class="cl">}finally{
+</span></span><span class="line"><span class="cl">  cleanUp();    //如果在这里再抛出一个异常，那么try中的exception将会丢失
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在上面的例子中，如果<code>someMethod()</code>抛出一个异常，并且在<code>finally</code>块中，<code>cleanUp()</code>也抛出一个异常，那么初始的<code>exception</code>将永远丢失。
+但是如果你不想处理<code>someMethod()</code>中的异常，但是仍然需要做一些清理工作，那么在<code>finally</code>块中进行清理。不要使用<code>catch</code>块。</p>
+<h2 id="参考文章">参考文章</h2>
+<ul>
+<li><a href="https://www.hollischuang.com/archives/5528">https://www.hollischuang.com/archives/5528</a></li>
+<li><a href="https://stackify.com/best-practices-exceptions-java">https://stackify.com/best-practices-exceptions-java</a></li>
+</ul>
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diff --git a/docs/posts/javabasics/rookie-generics/index.html b/docs/posts/javabasics/rookie-generics/index.html
new file mode 100644
index 00000000..74f5b1bf
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+	<title>Java泛型 ｜ 脚踏实地</title>
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+    <meta name="description" content="概览 在Java中，泛型是一种强大的编程特性，允许类、接口和方法在定义时声明一种参数化类型，而在使用时可以指定具体的类型参数。泛型的主要目的是提高代码的重用性和类" />
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+        
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+
+    
+    
+    
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+
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+
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+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
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+        
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+        <ul class="nav">
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+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%a7%88">
+                    概览
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+                    类型擦除
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+            
+            
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+                <a class="nav-link text-left" href="#%e6%b3%9b%e5%9e%8b%e4%b8%8e%e5%8f%8d%e5%b0%84">
+                    泛型与反射
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b3%9b%e5%9e%8b%e7%b1%bb">
+                    泛型类
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b3%9b%e5%9e%8b%e6%8e%a5%e5%8f%a3">
+                    泛型接口
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b3%9b%e5%9e%8b%e6%96%b9%e6%b3%95">
+                    泛型方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+                <a class="nav-link text-left" href="#%e6%b3%9b%e5%9e%8b%e9%80%9a%e9%85%8d%e7%ac%a6">
+                    泛型通配符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
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+                        <h2 id="post_single_title">Java泛型</h2>
+                        <span id="post_page_title_date" class="date">2024.07.15</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>在Java中，泛型是一种强大的编程特性，允许类、接口和方法在定义时声明一种参数化类型，而在使用时可以指定具体的类型参数。泛型的主要目的是提高代码的重用性和类型安全性。</p>
+<p>确切地说，泛型的本质是参数化类型，也就是在代码设计中，将类型作为参数进行传递和使用。这种参数化类型的设计使得代码可以更加灵活和通用，而不需要针对不同的数据类型重复编写类似的代码。
+Java泛型也是一种语法糖，在编译阶段完成类型的转换的工作，避免在运行时强制类型转换而出现<code>ClassCastException</code>，类型转化异常。举个例子，最常见的就是使用泛型集合：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;String&gt; names = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">names.add(&#34;Alice&#34;);
+</span></span><span class="line"><span class="cl">names.add(&#34;Bob&#34;);
+</span></span><span class="line"><span class="cl">// 不需要强制转换为 String
+</span></span><span class="line"><span class="cl">String first = names.get(0);
+</span></span></code></pre></div><p>需要注意的是，泛型在Java中是通过类型擦除来实现的，这意味着泛型信息只在编译时存在，而在运行时会被擦除。
+由于类型擦除，运行时不会保留泛型类型的具体信息。所以对于泛型类的实例，无法在运行时获取其具体的类型参数信息。</p>
+<h2 id="泛型特点">泛型特点</h2>
+<p>泛型的好处是在编译的时候检查类型安全，并且所有的强制转换都是自动和隐式的，提高代码的重用率。
+通过泛型，编译器能够在编译时检查类型，并确保类型参数的一致性，从而避免了因类型转换错误而导致的运行时异常。这种类型安全性大大提高了代码的健壮性和可靠性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;String&gt; names = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">names.add(&#34;Alice&#34;);
+</span></span><span class="line"><span class="cl">names.add(&#34;Bob&#34;);
+</span></span><span class="line"><span class="cl">String first = names.get(0); // 不需要强制转换为 String
+</span></span></code></pre></div><p>泛型允许编写通用的代码模板，适用于多种数据类型。通过泛型，可以在不同的上下文中重复使用同一段代码，而无需为每种数据类型都编写相似的代码逻辑，从而提高了代码的重用性和灵活性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 泛型方法，用于打印任意类型的数组元素
+</span></span><span class="line"><span class="cl">public static &lt;T&gt; void printArray(T[] arr) {
+</span></span><span class="line"><span class="cl">    for (T elem : arr) {
+</span></span><span class="line"><span class="cl">        System.out.print(elem + &#34; &#34;);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    System.out.println();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>使用泛型可以减少或消除代码中的类型转换，使代码更加简洁和易于理解。不再需要在每处使用到集合或类时进行手动类型转换，从而提高了代码的可读性和可维护性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Map&lt;String, Integer&gt; map = new HashMap&lt;&gt;();
+</span></span><span class="line"><span class="cl">map.put(&#34;one&#34;, 1);
+</span></span><span class="line"><span class="cl">map.put(&#34;two&#34;, 2);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 不需要强制转换为 Integer
+</span></span><span class="line"><span class="cl">int value = map.get(&#34;one&#34;);
+</span></span></code></pre></div><p>泛型在提高代码的类型安全性和重用性方面有很多优点，但也存在一些缺点和限制。
+例如，Java泛型是通过类型擦除实现的，这意味着在编译时会将泛型类型信息擦除掉，便于与旧版Java兼容。这导致在运行时无法获取泛型类型的具体信息。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;Integer&gt; intList = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">List&lt;String&gt; strList = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">System.out.println(intList.getClass() == strList.getClass());  // Output: true
+</span></span></code></pre></div><h2 id="类型擦除">类型擦除</h2>
+<p>Java中的泛型通过一种称为类型擦除的机制实现。声明了泛型的<code>.java</code>源代码，在编译生成<code>.class</code>文件之后，泛型相关的信息就消失了。
+可以认为，源代码中泛型相关的信息，就是提供给编译器用的，泛型信息对Java编译器可以见，而对Java虚拟机不可见。</p>
+<p>关于如何实现泛型，Java官方文档中有对应的解释，<a href="https://docs.oracle.com/javase/tutorial/java/generics/erasure.html">原文</a>如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Generics were introduced to the Java language to provide tighter type checks at compile time and to support generic programming. To implement generics, the Java compiler applies type erasure to:
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">- Replace all type parameters in generic types with their bounds or Object if the type parameters are unbounded. The produced bytecode, therefore, contains only ordinary classes, interfaces, and methods.
+</span></span><span class="line"><span class="cl">- Insert type casts if necessary to preserve type safety.
+</span></span><span class="line"><span class="cl">- Generate bridge methods to preserve polymorphism in extended generic types.
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Type erasure ensures that no new classes are created for parameterized types; consequently, generics incur no runtime overhead.
+</span></span></code></pre></div><p>以下是实现类型擦除的步骤：</p>
+<ol>
+<li>当你写泛型代码时，Java编译器会在编译阶段进行类型检查，确保你使用的类型是正确的。例如，如果你声明一个<code>List&lt;String&gt;</code>，编译器会确保你只能向这个列表添加字符串；</li>
+<li>一旦编译完成，所有的泛型类型信息都会被移除，这个过程叫做“类型擦除”。在类型擦除过程中：
+<ul>
+<li>泛型类型参数被替换：所有的泛型类型参数会被替换为它们的上界（如果没有指定上界，就替换为<code>Object</code>）。</li>
+<li>插入必要的类型转换：在必要的地方，编译器会插入类型转换，以确保类型安全。</li>
+</ul>
+</li>
+<li>当泛型类被继承，并且子类使用具体类型时，编译器会生成桥接方法来保证子类的方法正确覆盖父类的方法。桥接方法是编译器自动生成的，用来保证多态性和类型一致性；
+<br><br>假设有一个父类和一个子类：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;child value&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div>编译后，<code>Child</code>类中会有一个桥方法：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;child value&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 生成的桥方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">getValue</span><span class="p">();</span><span class="w"> </span><span class="c1">// 调用实际的getValue方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<p>在编译时，泛型类型参数会被替换为它们的上限。如果没有明确的上限，则替换为<code>Object</code>。泛型擦除示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 泛型类
+</span></span><span class="line"><span class="cl">public class Box&lt;T&gt; {
+</span></span><span class="line"><span class="cl">    private T value;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public void setValue(T value) {
+</span></span><span class="line"><span class="cl">        this.value = value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public T getValue() {
+</span></span><span class="line"><span class="cl">        return value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 使用泛型类
+</span></span><span class="line"><span class="cl">Box&lt;String&gt; stringBox = new Box&lt;&gt;();
+</span></span><span class="line"><span class="cl">stringBox.setValue(&#34;Hello&#34;);
+</span></span><span class="line"><span class="cl">String value = stringBox.getValue();
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 擦除后的类
+</span></span><span class="line"><span class="cl">public class Box {
+</span></span><span class="line"><span class="cl">    private Object value;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public void setValue(Object value) {
+</span></span><span class="line"><span class="cl">        this.value = value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    public Object getValue() {
+</span></span><span class="line"><span class="cl">        return value;
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 使用擦除后的类
+</span></span><span class="line"><span class="cl">Box stringBox = new Box();
+</span></span><span class="line"><span class="cl">stringBox.setValue(&#34;Hello&#34;);
+</span></span><span class="line"><span class="cl">String value = (String) stringBox.getValue(); // 强制类型转换
+</span></span></code></pre></div><p>由于泛型类型在运行时被擦除，无法在运行时获取泛型的实际类型信息。这会导致某些操作无法进行。例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">genericMethod</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">t</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">T</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在静态方法或静态上下文中，无法直接引用泛型类的类型参数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">GenericClass</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态方法中不能使用泛型类的类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// public static void staticMethod(T value) { // 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//     // ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// }</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 解决方法：定义静态泛型方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">staticMethod</span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>无法直接创建泛型数组。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 无法直接创建泛型数组
+</span></span><span class="line"><span class="cl">// List&lt;String&gt;[] stringLists = new ArrayList&lt;String&gt;[10]; // 编译错误
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 解决方法：使用原始类型数组并进行类型转换
+</span></span><span class="line"><span class="cl">List&lt;String&gt;[] stringLists = (List&lt;String&gt;[]) new ArrayList[10];
+</span></span></code></pre></div><p>泛型类型参数不能是基本数据类型，如<code>int</code>、<code>char</code>，只能是类类型。这可能会导致额外的装箱和拆箱开销，从而影响性能。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 使用基本数据类型会导致编译错误
+</span></span><span class="line"><span class="cl">// List&lt;int&gt; intList = new ArrayList&lt;&gt;(); // 编译错误
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 解决方法：使用包装类
+</span></span><span class="line"><span class="cl">List&lt;Integer&gt; intList = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">intList.add(1);
+</span></span><span class="line"><span class="cl">int value = intList.get(0); // 需要拆箱操作
+</span></span></code></pre></div><h2 id="泛型与反射">泛型与反射</h2>
+<p>Java中的泛型是通过类型擦除来实现的，这意味着泛型信息只在编译期间存在，而在运行时则被擦除。所以反射在运行时无法直接获取具体的泛型类型信息。</p>
+<p>类型擦除是Java泛型的一种实现机制，目的是保持与旧版本的兼容性。在编译过程中，泛型类型被替换为其非泛型上限，通常是<code>Object</code>类，并在需要时插入类型转换。
+这样Java编译器在编译期间进行类型检查，而在运行时不保留泛型类型信息。</p>
+<p>通过反射可以绕过Java泛型的类型检查，这利用了Java泛型的类型擦除机制。在编译时，泛型类型被擦除，实际操作的对象是原始类型<code>Object</code>。
+这使得在运行时可以向泛型集合中插入不同类型的元素。但这种做法会导致类型安全性问题，所以在实际开发中应谨慎使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">  </span><span class="c1">//这样调用 add 方法只能存储整形，因为泛型类型的实例为 Integer</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;add&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="p">.</span><span class="na">class</span><span class="p">).</span><span class="na">invoke</span><span class="p">(</span><span class="n">list</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;string&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="c1">// 1 string</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="泛型类">泛型类</h2>
+<p>在类上使用泛型，从而使类能够处理多种数据类型，而无需为每种数据类型编写单独的类。泛型类在定义时指定了一个或多个类型参数，这些类型参数在类的实例化时被具体的类型所替换。
+定义泛型类时，类型参数放在类名后面的尖括号内。例如，T是一个常用的类型参数名称，但你可以使用任何有效的标识符。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">NumberBox</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">number</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">NumberBox</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">number</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">number</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>需要注意的是，静态成员不能使用泛型类型参数，因为静态成员在类加载时已经存在，而类型参数在实例化时才确定。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericClass</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态成员不能使用泛型类的类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// private static T staticValue; // 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态方法不能直接使用泛型类的类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// public static void staticMethod(T value) { // 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//     // ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// }</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 可以使用泛型方法来解决这个问题</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">staticMethod</span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>泛型类不只接受一个类型参数，它还可以接受多个类型参数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Pair</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Pair</span><span class="p">(</span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="nf">getKey</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>除此之外，泛型类可以直接继承自另一个泛型类。当泛型类继承另一个泛型类时，可以选择保留父类的泛型类型参数，也可以重新定义自己的泛型类型参数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 父类是一个泛型类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Box</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Box</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 子类继承自泛型父类并保留类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ChildBox</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Box</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ChildBox</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>子类也可以重新定义自己的泛型类型参数，与父类的类型参数可以不同。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 父类是一个泛型类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Box</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Box</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 子类继承自泛型父类，并重新定义类型参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ChildBox</span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Box</span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ChildBox</span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>关于泛型类需要注意的是，一个泛型类可以继承自一个普通类，不需要在继承语法上做特别的修改。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 父类是一个普通类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 省略部分代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 子类是一个泛型类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Child</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 省略部分代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>但是普通类不能继承泛型类的类型参数，因为类型参数在实例化时才被确定，而普通类在编译时就被确定了。</p>
+<p>在Java中，使用泛型创建对象时，必须指定类型参数T的具体数据类型，即在尖括号&lt;&gt;中传入具体的类型。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Box&lt;Integer&gt; intBox = new Box&lt;&gt;(); // 使用 Integer 类型
+</span></span><span class="line"><span class="cl">intBox.setValue(123);
+</span></span><span class="line"><span class="cl">Integer intValue = intBox.getValue();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Box&lt;String&gt; strBox = new Box&lt;&gt;(); // 使用 String 类型
+</span></span><span class="line"><span class="cl">strBox.setValue(&#34;Hello&#34;);
+</span></span><span class="line"><span class="cl">String strValue = strBox.getValue();
+</span></span></code></pre></div><p>如果&lt;&gt;中什么都不传入，则编译器会发出警告，提示使用原始类型，这是不推荐的做法。使用原始类型的主要问题是类型安全性降低，容易引发<code>ClassCastException</code>等运行时错误。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Box rawBox = new Box(); // 使用原始类型（不推荐）
+</span></span><span class="line"><span class="cl">rawBox.setValue(&#34;Hello&#34;);
+</span></span><span class="line"><span class="cl">String strValue = (String) rawBox.getValue(); // 需要强制转换
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 编译时会发出警告：Box is a raw type. References to generic type Box&lt;T&gt; should be parameterized
+</span></span></code></pre></div><h2 id="泛型接口">泛型接口</h2>
+<p>泛型除了可以定义在类上，还可以定义在接口上。泛型接口允许你定义一个接口，其中的方法支持使用泛型类型参数。这样可以使得接口在实现时能够处理多种类型的数据，提高了灵活性和代码的复用性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">SomeInterface</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>实现泛型接口时可以指定具体的类型参数，也可以保留接口定义的类型参数，甚至可以不指定类型参数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SomeClass</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SomeInterface</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Doing something with: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AnotherClass</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SomeInterface</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Doing something with: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>实现泛型接口时没有确定类型参数，则默认为<code>Object</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AnotherClass</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SomeInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doSomething</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Doing something with: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>泛型接口可以拥有静态成员，但是这些静态成员不受类型参数的影响，属于接口本身的静态成员。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 定义一个泛型接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Generator</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">T</span><span class="w"> </span><span class="nf">generate</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态方法尝试使用类型参数 T，会导致编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printInfo</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Info: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实现泛型接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">StringGenerator</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Generator</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">generate</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Generated String&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="泛型方法">泛型方法</h2>
+<p>泛型方法是Java中一种特殊的方法，它在声明时可以使用泛型类型参数，使得方法在调用时可以接受不同类型的参数，并且能够保证类型安全。
+泛型方法是在方法声明中使用了泛型类型参数的方法。通常情况下，泛型方法的类型参数在方法返回类型之前声明。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericMethodExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型方法示例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">genericMethod</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Received: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">data</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在Java中，静态方法可以使用泛型，其声明方式与普通方法类似。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericMethodExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型方法示例：交换数组中的两个元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">swap</span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">T</span><span class="w"> </span><span class="n">temp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">temp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在静态成员中不能使用泛型类定义的类型参数，但我们可以将静态成员方法定义为一个泛型方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Test2</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 静态泛型方法示例：使用泛型类型参数 E</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 型类定义的类型参数 T 不能在静态方法中使用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">show</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>当一个方法需要处理多个泛型类型参数时，可以在方法签名中声明多个类型参数，并在方法体内使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MultiGenericMethodExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型方法示例：打印任意类型的数组元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printArray</span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">arr1</span><span class="p">,</span><span class="w"> </span><span class="n">U</span><span class="o">[]</span><span class="w"> </span><span class="n">arr2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;Array 1 elements: &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">elem</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">elem</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;Array 2 elements: &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">elem</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">elem</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>需要格外注意的是，Java泛型类中定义的类型参数与泛型方法中定义的类型参数是相互独立的，它们没有直接的关系。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Example</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型类中的类型参数 T</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">field</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 泛型方法中的类型参数 U（与泛型类中的 T 无关）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method</span><span class="p">(</span><span class="n">U</span><span class="w"> </span><span class="n">param</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">param</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>它们的命名可以不同，甚至可以具有相同的名称，但它们并不会直接相互影响或约束。为了避免混淆，如果在一个泛型类中存在泛型方法，那么两者的类型参数最好不要同名。</p>
+<h2 id="泛型通配符">泛型通配符</h2>
+<p>Java的泛型是类型安全的，即使两个类型具有继承关系，比如<code>Integer</code>是<code>Number</code>的子类，但<code>ArrayList&lt;Integer&gt;</code>并不是<code>ArrayList&lt;Number&gt;</code>的子类。
+这导致在处理不同泛型类型时，不能直接赋值或进行操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ArrayList&lt;Integer&gt; intList = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">ArrayList&lt;Number&gt; numList = intList; // 编译错误，ArrayList&lt;Integer&gt; 不是 ArrayList&lt;Number&gt; 的子类型
+</span></span></code></pre></div><p>使用泛型通配符可以解决这个问题，泛型通配符是用于解决泛型之间引用传递问题的特殊语法。
+泛型通配符通过引入<code>?</code>、<code>? extends T</code>和<code>? super T</code>这些语法，解决了泛型类型之间没有继承关系、不能直接赋值和操作以及无法处理不确定具体泛型类型等问题。</p>
+<p>泛型通配符用来表示未知类型，允许在泛型类、方法或接口中使用不确定的类型。
+它们主要有三种形式：<code>?</code>、<code>? extends ...</code>、<code>? super ...</code>，每种形式适用于不同的场景。</p>
+<ul>
+<li><code>?</code>通配符：表示任意类型，称为未限定通配符。<code>?</code>代表了任何一种数据类型，能代表任何一种数据类型的只有<code>null</code>。<code>Object</code>本身也算是一种数据类型，但却不能代表任何一种数据类型，所以<code>ArrayList&lt;Object&gt;</code>和<code>ArrayList&lt;?&gt;</code>的含义是不同的，前者类型是<code>Object</code>，也就是继承树的最高父类，而后者的类型完全是未知的，注意不要混淆。
+在使用时，可以用作泛型类型的参数，但不能实例化具体的泛型对象。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;?&gt; list = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 可以添加 null，因为 null 是任意引用类型的成员
+</span></span><span class="line"><span class="cl">list.add(null);
+</span></span><span class="line"><span class="cl">// 不能添加具体的对象，因为无法确定 list 的元素类型
+</span></span><span class="line"><span class="cl">// list.add(&#34;example&#34;); // 编译错误
+</span></span></code></pre></div></li>
+<li><code>? extends ...</code>通配符：<code>? extends T</code>表示某种具体类型的子类型（包括T自身），称为上界通配符。用于限制泛型类型的范围，可以用在方法参数、集合中的泛型类型等地方。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;? extends Number&gt; numbers = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 可以添加 null 或任何 Number 及其子类的对象
+</span></span><span class="line"><span class="cl">numbers.add(null);
+</span></span><span class="line"><span class="cl">numbers.add(new Integer(10));
+</span></span><span class="line"><span class="cl">numbers.add(new Double(3.14));
+</span></span><span class="line"><span class="cl">// 不能添加其他类型的对象，例如 String
+</span></span><span class="line"><span class="cl">// numbers.add(&#34;example&#34;); // 编译错误
+</span></span></code></pre></div></li>
+<li><code>? super ...</code>通配符：<code>? super T</code>表示某种具体类型的超类型（包括T自身），称为下界通配符。用于限制泛型类型为某个类的父类或者父类的父类等。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List&lt;? super Integer&gt; integers = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 可以添加 Integer 或其子类的对象
+</span></span><span class="line"><span class="cl">integers.add(new Integer(10));
+</span></span><span class="line"><span class="cl">integers.add(new Long(20L)); // Long 是 Integer 的父类
+</span></span><span class="line"><span class="cl">// 不能添加 Object 类型的对象
+</span></span><span class="line"><span class="cl">// integers.add(new Object()); // 编译错误
+</span></span></code></pre></div></li>
+</ul>
+<p>有一个有趣的问题，可能比较不好理解。使用了<code>ArrayList&lt;? extends Number&gt;</code>这样的通配符声明时，编译器会将此列表视为一个可以存放<code>Number</code>及其子类，如<code>Integer</code>、<code>Float</code>等对象的集合。然而这种声明方式也限制了你向这个集合中添加元素的能力。
+具体来说，你无法向使用了上界通配符<code>&lt;? extends Number&gt;</code>的列表中添加任何类型的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="n">ArrayList</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="c1">// 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">		</span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Float</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">0</span><span class="p">));</span><span class="c1">// 编译错误</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ArrayList&lt;? extends Number&gt;</code>表示这个列表中的元素的确是<code>Number</code>或其子类，但具体是哪一种子类是不确定的。
+在编译时，Java无法确定你尝试添加的是哪一种具体的子类<code>Integer</code>还是<code>Float</code>，因此会阻止这种可能会导致类型不匹配的操作。
+泛型的目的之一是在编译时提供类型安全性检查。使用了<code>&lt;? extends Number&gt;</code>的通配符后，编译器不能确保添加的具体子类型是安全的，因此禁止了这种操作。
+如果你需要向列表中添加元素，应该使用没有通配符的具体类型来声明列表。上界统配符最大的作用就是为了拓展方法形参中类型参数的范围。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w"> </span><span class="c1">// 正确，因为Integer是Number的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Float</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">0</span><span class="p">));</span><span class="w"> </span><span class="c1">// 正确，因为Float是Number的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>有意思的来了，使用<code>ArrayList&lt;? super Number&gt;</code>，添加<code>Object</code>类型的对象编译报错。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">GenericType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">super</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w"> </span><span class="c1">// 编译正确，Integer 是 Number 的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Float</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">0</span><span class="p">));</span><span class="w"> </span><span class="c1">// 编译正确，Float 是 Number 的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">());</span><span class="w"> </span><span class="c1">// 编译错误，Object 不是 Number 或其子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>其原因是，<code>ArrayList&lt;? super Number&gt;</code>的下界是<code>ArrayList&lt;Number&gt;</code>。因此，我们可以确定<code>Number</code>类及其子类的对象自然可以加入<code>ArrayList&lt;? super Number&gt;</code>集合中。
+而<code>Number</code>类的父类对象就不能加入<code>ArrayList&lt;? super Number&gt;</code>集合中了，因为不能确定<code>ArrayList&lt;? super Number&gt;</code>集合的数据类型。</p>
+<p>使用<code>extends</code>通配符,允许获取集合中的元素，因为可以确定元素至少是指定类型的子类。禁止向集合中添加任何元素，因为编译器无法确定具体的子类型，不能确保类型安全性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ExtendsWildcardExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译错误：无法添加任何元素，因为编译器无法确定具体的子类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// list.add(new Integer(1));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// list.add(new Float(1.0));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 可以安全地获取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Number</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w"> </span><span class="c1">// 可以确定是 Number 类型或其子类的对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;First element: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">num</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>使用<code>super</code>通配符，允许向集合中添加元素，因为可以确定元素至少是指定类型的父类。禁止安全地从集合中读取元素，因为编译器无法确定具体的父类型，不能确保类型安全性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SuperWildcardExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">super</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 允许添加 Integer 及其子类的对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译错误：无法安全地从列表中获取元素，因为编译器无法确定具体的父类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Integer num = list.get(0);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译错误：只能存放 Integer 及其子类的对象，Object 不是 Integer 的子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// list.add(new Object());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>PECS原则（Producer Extends, Consumer Super）是理解和使用Java泛型通配符的一个重要原则。这个原则帮助我们决定在使用泛型时，应该使用<code>extends</code>还是<code>super</code>通配符。
+如果我们从集合中读取元素并返回它们，即集合是生产者，我们应该使用<code>&lt;? extends T&gt;</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ProducerExtendsExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">integerList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">integerList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">integerList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">numberList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">integerList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Number</span><span class="w"> </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getFirst</span><span class="p">(</span><span class="n">numberList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;First number: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">number</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Number</span><span class="w"> </span><span class="nf">getFirst</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w"> </span><span class="c1">// 安全地读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>如果我们向集合中写入元素，即集合是消费者，我们应该使用<code>&lt;? super T&gt;</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConsumerSuperExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Number</span><span class="o">&gt;</span><span class="w"> </span><span class="n">numberList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">super</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">integerList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">numberList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">addNumbers</span><span class="p">(</span><span class="n">integerList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Number list: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">numberList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addNumbers</span><span class="p">(</span><span class="n">List</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">super</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">3</span><span class="p">));</span><span class="w"> </span><span class="c1">// 安全地写入元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="p">(</span><span class="n">4</span><span class="p">));</span><span class="w"> </span><span class="c1">// 安全地写入元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ad%97%e8%8a%82%e6%b5%81%e4%b8%8e%e5%ad%97%e7%ac%a6%e6%b5%81">
+                    字节流与字符流
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%8a%82%e7%82%b9%e6%b5%81%e4%b8%8e%e5%a4%84%e7%90%86%e6%b5%81">
+                    节点流与处理流
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ba%8f%e5%88%97%e5%8c%96">
+                    序列化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ba%8f%e5%88%97%e5%8c%96%e4%bd%9c%e7%94%a8">
+                    序列化作用
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e5%ba%8f%e5%88%97%e5%8c%96">
+                    使用序列化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#serializable">
+                    Serializable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#externalizable">
+                    Externalizable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#transient">
+                    transient
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#serialversionuid">
+                    serialVersionUID
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%87%aa%e5%ae%9a%e4%b9%89%e5%ba%8f%e5%88%97%e5%8c%96%e5%92%8c%e5%8f%8d%e5%ba%8f%e5%88%97%e5%8c%96">
+                    自定义序列化和反序列化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8d%95%e4%be%8b%e4%b8%8e%e5%ba%8f%e5%88%97%e5%8c%96">
+                    单例与序列化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#io%e6%a8%a1%e5%9e%8b">
+                    IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%98%bb%e5%a1%9e%e5%bc%8fio%e6%a8%a1%e5%9e%8b">
+                    阻塞式IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9d%9e%e9%98%bb%e5%a1%9eio%e6%a8%a1%e5%9e%8b">
+                    非阻塞IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#io%e5%a4%8d%e7%94%a8%e6%a8%a1%e5%9e%8b">
+                    IO复用模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bf%a1%e5%8f%b7%e9%a9%b1%e5%8a%a8io%e6%a8%a1%e5%9e%8b">
+                    信号驱动IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%82%e6%ad%a5io%e6%a8%a1%e5%9e%8b">
+                    异步IO模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#nio">
+                    NIO
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e6%af%94%e4%bc%a0%e7%bb%9fio">
+                    对比传统IO
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%9a%e9%81%93">
+                    通道
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bc%93%e5%86%b2%e5%8c%ba">
+                    缓冲区
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%89%e6%8b%a9%e5%99%a8">
+                    选择器
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e8%80%83%e6%96%87%e7%ab%a0">
+                    参考文章
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="https://whiteppure.github.io/iblog/">首页</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="https://whiteppure.github.io/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="https://whiteppure.github.io/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                        <h2 id="post_single_title">JavaIO</h2>
+                        <span id="post_page_title_date" class="date">2021.04.09</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>IO，即<code>in</code>和<code>out</code>的缩写，也就是输入和输出，指应用程序和外部设备之间的数据传递，常见的外部设备包括文件、管道、网络连接。
+从计算机结构的角度来看IO，IO就是描述了计算机系统和外部设备之间通信的过程。</p>
+<p>传统的IO是通过流技术来处理的。<code>Java IO</code>通过数据流、序列化和文件系统提供输入和输出。
+流（<code>Stream</code>），是一个抽象的概念，是指一连串的数据（字符或字节），是以先进先出的方式发送信息的通道。
+代表任何有能力产出数据的数据源对象或者是有能力接受数据的接收端对象。流的作用就是为数据源和目的地建立一个输送通道。</p>
+<p>一般来说关于流的特性有以下几点：</p>
+<ul>
+<li>先进先出：最先写入输出流的数据最先被输入流读取到。</li>
+<li>顺序存取：可以一个接一个地往流中写入一串字节，读出时也将按写入顺序读取一串字节，不能随机访问中间的数据，<code>RandomAccessFile</code>除外。</li>
+<li>只读或只写：每个流只能是输入流或输出流的一种，不能同时具备两个功能，输入流只能进行读操作，对输出流只能进行写操作。
+在一个数据传输通道中，如果既要写入数据又要读取数据，则要分别提供两个流。</li>
+</ul>
+<h2 id="流的分类">流的分类</h2>
+<p><img alt="JavaIO流分类" src="/iblog/posts/annex/images/essays/JavaIO%E6%B5%81%E5%88%86%E7%B1%BB.png"></p>
+<p>根据数据传输特性将流抽象为各种类，方便更直观的进行数据操作。主要的分类方式有以下3种：</p>
+<ul>
+<li>按数据流的方向：分为输入流、输出流；</li>
+<li>按处理数据单位：分为字节流、字符流；</li>
+<li>按功能：分为节点流、处理流；</li>
+</ul>
+<p>看上面的几个分类可能会感觉到有些混乱，那什么时候用字节流？什么时候该用输出流呢？</p>
+<ol>
+<li>首先自己要知道是选择输入流还是输出流，这就要根据自己的情况而定，如果你想从程序写东西到别的地方，那么就选择输出流，反之用输入流。</li>
+<li>然后考虑你传输数据时，是选择使用字节流传输还是字符流，也就是每次传1个字节还是2个字节，有中文肯定就选择字符流了。</li>
+<li>前面两步就可以选出一个合适的节点流了，比如字节输入流<code>InputStream</code>，如果要在此基础上增强功能，那么就在处理流中选择一个合适的即可。</li>
+</ol>
+<h3 id="输入流与输出流">输入流与输出流</h3>
+<p>输入流和输出流是Java中用于处理字节数据的抽象类，它们提供了读取和写入数据的方法，用于处理各种数据源和目标，如文件、网络连接等。
+此输入、输出是相对于我们写的代码程序而言。</p>
+<ul>
+<li>输入流：从别的地方获取资源输入到我们的程序中；如从数据源（如文件、网络连接、内存等）读取数据；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">inputStream</span><span class="p">.</span><span class="na">read</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 处理读取的数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">inputStream</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>输出流：从我们的程序中输出到别的地方；如将一个字符串保存到本地文件中，就需要使用输出流；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">OutputStream</span><span class="w"> </span><span class="n">outputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;output.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">String</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello, World!&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="na">getBytes</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">outputStream</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="n">bytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">outputStream</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>输入流和输出流是Java中用于处理字节数据的基本抽象，它们提供了读取和写入数据的方法，能够处理各种数据源和目标。
+在实际应用中，根据需求选择合适的输入流或输出流的子类，并结合缓冲区等机制提高数据处理效率。</p>
+<h3 id="字节流与字符流">字节流与字符流</h3>
+<p>字节流和字符流的用法几乎完成全一样，区别在于字节流和字符流所操作的数据单元不同。字节流操作的单元是数据单元是8位的字节，而字符流操作的是数据单元为16位的字符。</p>
+<blockquote>
+<p>字符流的由来
+Java中字符是采用<code>Unicode</code>标准，一个字符是16位，即一个字符使用两个字节来表示。为此，Java中引入了处理字符的流。因为数据编码的不同，而有了对字符进行高效操作的流对象。本质其实就是基于字节流读取时，去查了指定的码表。
+在<code>Unicode</code>编码中，一个英文为一个字节，一个中文为两个字节。如果使用字节流处理中文，如果一次读写一个字符对应的字节数就不会有问题，一旦将一个字符对应的字节分裂开来，就会出现乱码了。</p>
+</blockquote>
+<p>字节流以字节为单位进行数据读写，适合处理二进制数据（如图像、音频等）和文本数据。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">inputStream</span><span class="p">.</span><span class="na">read</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 处理读取的字节数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">inputStream</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>字符流以字符为单位进行数据读写，适合处理文本数据（如文本文件、字符串等）。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Reader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileReader</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">read</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 处理读取的字符数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">reader</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>在Java中，字节流和字符流之间的转换可以通过<code>InputStreamReader</code>和<code>OutputStreamWriter</code>进行。
+这两个类分别将<code>InputStream</code>转换为<code>Reader</code>，以及将<code>OutputStream</code>转换为<code>Writer</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 字节输入流转换为字符输入流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ByteToCharStreamExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">FileInputStream</span><span class="w"> </span><span class="n">fileInputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;example.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">InputStreamReader</span><span class="w"> </span><span class="n">inputStreamReader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InputStreamReader</span><span class="p">(</span><span class="n">fileInputStream</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;UTF-8&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">BufferedReader</span><span class="w"> </span><span class="n">bufferedReader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="n">inputStreamReader</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">line</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">line</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bufferedReader</span><span class="p">.</span><span class="na">readLine</span><span class="p">())</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">line</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 字节输出流转换为字符输出流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CharToByteStreamExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">FileOutputStream</span><span class="w"> </span><span class="n">fileOutputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;output.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">OutputStreamWriter</span><span class="w"> </span><span class="n">outputStreamWriter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">OutputStreamWriter</span><span class="p">(</span><span class="n">fileOutputStream</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;UTF-8&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">BufferedWriter</span><span class="w"> </span><span class="n">bufferedWriter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedWriter</span><span class="p">(</span><span class="n">outputStreamWriter</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">bufferedWriter</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="s">&#34;这是一个字符流到字节流的示例。&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">bufferedWriter</span><span class="p">.</span><span class="na">newLine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">bufferedWriter</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="s">&#34;Hello, world!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>字节流一般用来处理图像、视频、音频、<code>PPT、Word</code>等类型的文件。字符流一般用于处理纯文本类型的文件，如<code>txt</code>文件等，但不能处理图像视频等非文本文件。
+用一句话说就是，字节流可以处理一切文件，而字符流只能处理纯文本文件。
+字节流本身没有缓冲区，缓冲字节流相对于字节流，效率提升非常高。而字符流本身就带有缓冲区，缓冲字符流相对于字符流效率提升就不是那么大了。</p>
+<h3 id="节点流与处理流">节点流与处理流</h3>
+<p>按功能不同分为节点流、处理流：</p>
+<ul>
+<li>节点流：节点流直接连接到数据源（如文件、网络连接、内存等），负责实际的数据读写操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 文件输入节点流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 文件输出节点流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">OutputStream</span><span class="w"> </span><span class="n">outputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;output.txt&#34;</span><span class="p">);</span><span class="w"> 
+</span></span></span></code></pre></div></li>
+<li>处理流：处理流不直接操作数据源，而是通过包装在节点流上来增强其功能和处理能力。处理流的构造方法始终接受另一个流对象作为参数。
+通过多层包装，处理流形成了对节点流的封装，但实际的数据处理操作仍由底层节点流完成。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;file.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用处理流包装节点流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">BufferedReader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">InputStreamReader</span><span class="p">(</span><span class="n">inputStream</span><span class="p">));</span><span class="w"> 
+</span></span></span></code></pre></div></li>
+</ul>
+<h2 id="序列化">序列化</h2>
+<p>序列化是将对象的状态信息转换为可存储或传输的形式的过程。一个对象可以被表示为一个字节序列，该字节序列包括该对象的数据、有关对象的类型的信息和存储在对象中数据的类型。
+序列化是一种数据的持久化手段。一般广泛应用于网络传输，<code>RMI</code>和<code>RPC</code>等场景中。一般是以字节码或XML格式传输。而字节码或XML编码格式可以还原为完全相等的对象。</p>
+<p>将序列化对象写入文件之后，可以从文件中读取出来，这个相反的过程称为反序列化。</p>
+<h3 id="序列化作用">序列化作用</h3>
+<p>序列化机制允许将实现序列化的Java对象转换位字节序列，这些字节序列可以保存在磁盘上，或通过网络传输，以达到以后恢复成原来的对象。
+序列化机制使得对象可以脱离程序的运行而独立存在。</p>
+<p>对象序列化机制是Java语言内建的一种对象持久化方式，通过对象序列化，可以把对象的状态保存为字节数组，并且可以在有需要的时候将这个字节数组通过反序列化的方式再转换成对象。
+对象序列化可以很容易的在JVM中的活动对象和字节流之间进行转换。</p>
+<p>由于序列化整个过程都是Java虚拟机独立的，也就是说，在一个平台上序列化的对象可以在另一个完全不同的平台上反序列化该对象。
+在Java中，对象的序列化与反序列化被广泛应用到RMI(远程方法调用)及网络传输中。</p>
+<h3 id="使用序列化">使用序列化</h3>
+<p>使用Java对象序列化在保存对象时，会把其状态保存为一组字节，在未来再将这些字节组装成对象。
+必须注意地是，对象序列化保存的是对象的&quot;状态&quot;，即它的成员变量。所以对象序列化不会关注类中的静态变量。</p>
+<p>如果需要将某个对象保存到磁盘上或者通过网络传输，那么这个类应该实现<code>Serializable</code>接口或<code>Externalizable</code>接口。</p>
+<h4 id="serializable">Serializable</h4>
+<p>类的可序列化性是通过实现<code>java.io.Serializable</code>接口的类来启用的。没有实现此接口的类的任何状态都不会被序列化或反序列化。
+可序列化类的所有子类型本身都是可序列化的。序列化接口没有方法或字段，只用于标识可序列化的语义。</p>
+<p>为了允许非序列化类的子类型被序列化，子类型可以承担保存和恢复超类型的公共、受保护和(如果可以访问)包字段的状态的责任。
+只有当它所继承的类有一个可访问的无参数构造函数来初始化类的状态时，子类型才可以承担这种责任。如果不是这种情况，则声明一个类可序列化是错误的，该错误将在运行时检测到。</p>
+<p>当试图对一个对象进行序列化的时候，如果遇到未实现<code>Serializable</code>接口的对象。在此情况下，将抛出<code>NotSerializableException</code>，并标识非<code>serializable</code>对象的类。
+实现<code>Serializable</code>序列化反序列对象化代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//       serialUser();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;----------反序列化对象----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">unSerialUser</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">serialUser</span><span class="w"> </span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;Jane&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">));)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unSerialUser</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">User</span><span class="w"> </span><span class="n">newUser</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">User</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">newUser</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">User</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getAge</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAge</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;User{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, age=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Serializable</code>明明就是一个空的接口，它是怎么保证只有实现了该接口的方法才能进行序列化与反序列化的呢？
+对象的序列化过程是通过<code>ObjectOutputStream</code>和<code>ObjectInputputStream</code>来实现的。在<code>ObjectOutputStream</code>中<code>writeObject</code>的调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(&#34;stringlist&#34;));
+</span></span><span class="line"><span class="cl">objectOutputStream.writeObject(stringList);
+</span></span><span class="line"><span class="cl">IOUtils.close(objectOutputStream);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">writeObject
+</span></span><span class="line"><span class="cl">    ---&gt;writeObject0
+</span></span><span class="line"><span class="cl">    ---&gt;writeOrdinaryObject
+</span></span><span class="line"><span class="cl">    ---&gt;writeSerialData
+</span></span><span class="line"><span class="cl">    ---&gt;invokeWriteObject
+</span></span></code></pre></div><p><code>writeObject0</code>方法中有这么一段代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Underlying writeObject/writeUnshared implementation.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeObject0</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">unshared</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">oldMode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bout</span><span class="p">.</span><span class="na">setBlockDataMode</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">depth</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="c1">// ... </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// remaining cases</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">obj</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeString</span><span class="p">((</span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">unshared</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">cl</span><span class="p">.</span><span class="na">isArray</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeArray</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">desc</span><span class="p">,</span><span class="w"> </span><span class="n">unshared</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">obj</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Enum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeEnum</span><span class="p">((</span><span class="n">Enum</span><span class="o">&lt;?&gt;</span><span class="p">)</span><span class="w"> </span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">desc</span><span class="p">,</span><span class="w"> </span><span class="n">unshared</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// =============================</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">obj</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Serializable</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeOrdinaryObject</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">desc</span><span class="p">,</span><span class="w"> </span><span class="n">unshared</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">extendedDebugInfo</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NotSerializableException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">cl</span><span class="p">.</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\n&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">debugInfoStack</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NotSerializableException</span><span class="p">(</span><span class="n">cl</span><span class="p">.</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// =============================</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ... </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在进行序列化操作时，会判断要被序列化的类是否是<code>String</code>、<code>Enum</code>、<code>Array</code>和<code>Serializable</code>类型，如果不是则直接抛出<code>NotSerializableException</code>。</p>
+<h4 id="externalizable">Externalizable</h4>
+<p><code>Externalizable</code>继承了<code>Serializable</code>，该接口中定义了两个抽象方法：<code>writeExternal</code>()与<code>readExternal()</code>。
+当使用<code>Externalizable</code>接口来进行序列化与反序列化的时候，需要开发人员重写<code>writeExternal()</code>与<code>readExternal()</code>。</p>
+<p>还有一点值得注意，在使用<code>Externalizable</code>进行序列化的时候，在读取对象时，会调用被序列化类的无参构造器去创建一个新的对象，然后再将被保存对象的字段的值分别填充到新对象中。
+所以在实现<code>Externalizable</code>接口的类必须要提供一个<code>public</code>的无参的构造器。如果<code>User</code>类中没有无参数的构造函数，在反序列化时会抛出异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">java.io.InvalidClassException: content.posts.rookie.User; no valid constructor
+</span></span></code></pre></div><p>实现<code>Externalizable</code>序列化反序列对象化代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//       serialUser();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;----------反序列化对象----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">unSerialUser</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">serialUser</span><span class="w"> </span><span class="p">()</span><span class="w">  </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;Jane&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// /将对象序列化到文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">));)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unSerialUser</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">User</span><span class="w"> </span><span class="n">newUser</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">User</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">newUser</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">User</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Externalizable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">User</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getAge</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAge</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;User{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, age=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeExternal</span><span class="p">(</span><span class="n">ObjectOutput</span><span class="w"> </span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">out</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">out</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">age</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">readExternal</span><span class="p">(</span><span class="n">ObjectInput</span><span class="w"> </span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="n">in</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="n">in</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="transient">transient</h4>
+<p>对于一个类中的某些字段如果不需要序列化，就需要加上<code>transient</code>关键字。
+被<code>transient</code>修饰的成员变量，在序列化的时候其值会被忽略，在被反序列化后，<code>transient</code>变量的值被设为初始值，如<code>int</code>型的是0，引用类型的是<code>null</code>。
+此时<code>name</code>字段将不会被序列化，当然如果一个变量被<code>static</code>修饰，它也不会被序列化。这是因为<code>static</code>字段属于类，而不是类的具体实例。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 该字段不会被序列化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">address</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>当你不希望某个成员变量的状态被序列化时，可以使用<code>transient</code>关键字。通常这种情况是因为该变量的状态是临时的，或者该变量包含敏感信息（如密码），不应在序列化过程中保存。</p>
+<h4 id="serialversionuid">serialVersionUID</h4>
+<p>虚拟机是否允许反序列化， 不仅取决于类路径和功能代码是否⼀致，⼀个⾮常重要的⼀点是两个类的序列化 ID 是否⼀致，即<code>serialVersionUID</code>要求⼀致。
+因为⽂件存储中的内容可能被篡改，为了保证数据的安全，在进⾏反序列化时，JVM会把传来的字节流中的<code>serialVersionUID</code>与本地相应实体类的<code>serialVersionUID</code>进⾏⽐较，如果相同就认为是⼀致的，可以进⾏反序列化。
+否则就会出现序列化版本不⼀致的异常，即<code>InvalidCastException</code>。</p>
+<p><code>Serializable</code>接口注释：</p>
+<blockquote>
+<p>If a serializable class does not explicitly declare a serialVersionUID,
+then the serialization runtime will calculate a default
+serialVersionUID value for that class based on various aspects of the class,
+as described in the Java(TM) Object Serialization Specification.
+However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID values,
+since the default serialVersionUID computation is highly sensitive to class details that may vary depending on compiler implementations,
+and can thus result in unexpectedInvalidClassExceptions during deserialization.</p>
+</blockquote>
+<p>大意：当实现<code>java.io.Serializable</code>接口的类没有显式地定义⼀个<code>serialVersionUID</code>变量时候，Java序列化机制会根据编译的Class⾃动⽣成⼀个<code>serialVersionUID</code>作序列化版本⽐较⽤，
+这种情况下，如果<code>class</code>⽂件没有发⽣变化，就算再编译多次，<code>serialVersionUID</code>也不会变化的。但是如果发⽣了变化，那么这个⽂件对应的<code>serialVersionUID</code>也就会发⽣变化。</p>
+<p>Java强烈建议用户自定义一个<code>serialVersionUID</code>，如果我们没有在类中明确的定义一个<code>serialVersionUID</code>的话，反序列化时可能会导致<code>InvalidClassException</code>这个异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;----------序列化对象----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">serialUser</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;----------反序列化对象----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">unSerialUser</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">serialUser</span><span class="w"> </span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;Jane&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">user</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">));)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unSerialUser</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">&#34;./user.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="p">(</span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">User</span><span class="w"> </span><span class="n">newUser</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">User</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">newUser</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">User</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getAge</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAge</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;User{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, age=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">java.io.InvalidClassException: com.test.User; local class incompatible: stream classdesc serialVersionUID = -2986778152837257883, local class serialVersionUID = 7961728318907695402
+</span></span></code></pre></div><p>代码调用链：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ObjectInputStream.readObject 
+</span></span><span class="line"><span class="cl">    -&gt; readObject0
+</span></span><span class="line"><span class="cl">    -&gt; readOrdinaryObject
+</span></span><span class="line"><span class="cl">    -&gt; readClassDesc
+</span></span><span class="line"><span class="cl">    -&gt; readNonProxyDesc
+</span></span><span class="line"><span class="cl">    -&gt; ObjectStreamClass.initNonProxy
+</span></span></code></pre></div><p>在<code>initNonProxy</code>中 ，关键代码如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">initNonProxy</span><span class="p">(</span><span class="n">ObjectStreamClass</span><span class="w"> </span><span class="n">model</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                  </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">cl</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                  </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">resolveEx</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                  </span><span class="n">ObjectStreamClass</span><span class="w"> </span><span class="n">superDesc</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">throws</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">long</span><span class="w"> </span><span class="n">suid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Long</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">getSerialVersionUID</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ObjectStreamClass</span><span class="w"> </span><span class="n">osc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">cl</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">osc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lookup</span><span class="p">(</span><span class="n">cl</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">osc</span><span class="p">.</span><span class="na">isProxy</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;cannot bind non-proxy descriptor to a proxy class&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">isEnum</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">osc</span><span class="p">.</span><span class="na">isEnum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">isEnum</span><span class="w"> </span><span class="o">?</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;cannot bind enum descriptor to a non-enum class&#34;</span><span class="w"> </span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;cannot bind non-enum descriptor to an enum class&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ========== 判断反序列化 serializableUID 是否一致 ========== start//</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">serializable</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">osc</span><span class="p">.</span><span class="na">serializable</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">!</span><span class="n">cl</span><span class="p">.</span><span class="na">isArray</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">suid</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">osc</span><span class="p">.</span><span class="na">getSerialVersionUID</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="n">osc</span><span class="p">.</span><span class="na">name</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;local class incompatible: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="s">&#34;stream classdesc serialVersionUID = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">suid</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="s">&#34;, local class serialVersionUID = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">osc</span><span class="p">.</span><span class="na">getSerialVersionUID</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ========== 判断反序列化 serializableUID 是否一致 ========== end//</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 在反序列化过程中，对serialVersionUID做了比较，如果发现不相等，则直接抛出异常</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">classNamesEqual</span><span class="p">(</span><span class="n">model</span><span class="p">.</span><span class="na">name</span><span class="p">,</span><span class="w"> </span><span class="n">osc</span><span class="p">.</span><span class="na">name</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="n">osc</span><span class="p">.</span><span class="na">name</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="s">&#34;local class name incompatible with stream class &#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="s">&#34;name \&#34;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">model</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>其中<code>getSerialVersionUID</code>方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="nf">getSerialVersionUID</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// REMIND: synchronize instead of relying on volatile?</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">suid</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">suid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">AccessController</span><span class="p">.</span><span class="na">doPrivileged</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">PrivilegedAction</span><span class="o">&lt;</span><span class="n">Long</span><span class="o">&gt;</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kd">public</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 生成一个默认的serialVersionUID</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">return</span><span class="w"> </span><span class="n">computeDefaultSUID</span><span class="p">(</span><span class="n">cl</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">suid</span><span class="p">.</span><span class="na">longValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这也就是报错的原因，在没有定义<code>serialVersionUID</code>的时候，会调用<code>computeDefaultSUID</code>方法，生成一个默认的<code>serialVersionUID</code>。
+所以如果一个类实现了<code>Serializable</code>接口，一定要记得定义<code>serialVersionUID</code>，否则会发生异常。<code>serialVersionUID</code>有两种显示的生成方式：</p>
+<ul>
+<li>默认的<code>1L</code>，比如：<code>private static final long serialVersionUID = 1L; </code></li>
+<li>根据类名、接口名、成员方法及属性等来生成一个64位的哈希字段，比如：<code>private static final  long   serialVersionUID = xxxxL;</code></li>
+</ul>
+<p>可通过编译器进行设置，让它帮忙提示：
+<img alt="idea检查serialVersionUID" src="/iblog/posts/annex/images/essays/idea%E6%A3%80%E6%9F%A5serialVersionUID.png"></p>
+<p><img alt="idea自动生成serialVersionUID" src="/iblog/posts/annex/images/essays/idea%E8%87%AA%E5%8A%A8%E7%94%9F%E6%88%90serialVersionUID.png"></p>
+<h3 id="自定义序列化和反序列化">自定义序列化和反序列化</h3>
+<p>想要实现自定义序列化和反序列化，可以在被序列化的类中增加<code>writeObject</code>和<code>readObject</code>方法来实现。
+举个例子，看一下<code>java.util.ArrayList</code>中的是如何自定义序列化的：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">implements</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">RandomAccess</span><span class="p">,</span><span class="w"> </span><span class="n">Cloneable</span><span class="p">,</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">Serializable</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">serialVersionUID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">8683452581122892189L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">transient</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elementData</span><span class="p">;</span><span class="w"> </span><span class="c1">// non-private to simplify nested class access</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ArrayList</code>实现了<code>java.io.Serializable</code>接口且有自定义<code>serialVersionUID</code>，那么我们就可以对它进行序列化及反序列化。
+<code>ArrayList</code>底层是通过数组实现的，其中数组<code>elementData</code>其实就是用来保存列表中的元素的。
+因为<code>elementData</code>是被<code>transient</code>修饰的，所以这个成员变量不会被序列化而保留下来。那么为什么却通过序列化和反序列化把<code>List</code>中的元素保留下来了呢？</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stringList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">stringList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;hello&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">stringList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;world&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">stringList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;123&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">stringList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;init StringList&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">stringList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">objectOutputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;stringlist&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectOutputStream</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">stringList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">IOUtils</span><span class="p">.</span><span class="na">close</span><span class="p">(</span><span class="n">objectOutputStream</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">&#34;stringlist&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">objectInputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newStringList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">)</span><span class="n">objectInputStream</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">IOUtils</span><span class="p">.</span><span class="na">close</span><span class="p">(</span><span class="n">objectInputStream</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="p">(</span><span class="n">file</span><span class="p">.</span><span class="na">exists</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">file</span><span class="p">.</span><span class="na">delete</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;new StringList&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">newStringList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ArrayList</code>实际上是动态数组，每次在放满以后自动增长设定的长度值，如果数组自动增长长度设为100，而实际只放了一个元素，那就会序列化99个<code>null</code>元素。
+为了保证在序列化的时候不会将这么多<code>null</code>同时进行序列化，<code>ArrayList</code>把元素数组设置为<code>transient</code>。
+为了防止一个包含大量空对象的数组被序列化优化存储，所以<code>ArrayList</code>使用<code>transient</code>来修饰<code>elementData</code>。
+但是作为一个集合，在序列化过程中还必须保证其中的元素可以被持久化下来，所以通过重写<code>writeObject</code>和<code>readObject</code>方法的方式把其中的元素保留下来。</p>
+<p>在序列化过程中，如果被序列化的类中定义了<code>writeObject</code>和<code>readObject</code>方法，虚拟机会试图调用对象类里的<code>writeObject</code>和<code>readObject</code>方法，进行用户自定义的序列化和反序列化。
+如果没有这样的方法，则默认调用是<code>ObjectOutputStream</code>的<code>defaultWriteObject</code>方法以及<code>ObjectInputStream</code>的<code>defaultReadObject</code>方法。
+用户自定义的<code>writeObject</code>和<code>readObject</code>方法可以允许用户控制序列化的过程，比如可以在序列化的过程中动态改变序列化的数值。对象的序列化过程通过<code>ObjectOutputStream</code>和<code>ObjectInputputStream</code>来实现的。</p>
+<p><code>writeObject</code>方法把<code>elementData</code>数组中的元素遍历的保存到输出流（<code>ObjectOutputStream</code>）中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeObject</span><span class="p">(</span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">ObjectOutputStream</span><span class="w"> </span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">IOException</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Write out element count, and any hidden stuff</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedModCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">modCount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">s</span><span class="p">.</span><span class="na">defaultWriteObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Write out size as capacity for behavioural compatibility with clone()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">s</span><span class="p">.</span><span class="na">writeInt</span><span class="p">(</span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Write out all elements in the proper order.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">elementData</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>readObject</code>方法从输入流（<code>ObjectInputStream</code>）中读出对象并保存赋值到 <code>elementData</code> 数组中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">readObject</span><span class="p">(</span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">ObjectInputStream</span><span class="w"> </span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">java</span><span class="p">.</span><span class="na">io</span><span class="p">.</span><span class="na">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">EMPTY_ELEMENTDATA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Read in size, and any hidden stuff</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">s</span><span class="p">.</span><span class="na">defaultReadObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Read in capacity</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">s</span><span class="p">.</span><span class="na">readInt</span><span class="p">();</span><span class="w"> </span><span class="c1">// ignored</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// be like clone(), allocate array based upon size not capacity</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ensureCapacityInternal</span><span class="p">(</span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elementData</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Read in all elements in the proper order.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="n">size</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">a</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那么在一个类中定义了<code>writeObject</code>和<code>readObject</code>方法，这两个方法是怎么被调用的呢？ 答案是会通过反射的方式调用。</p>
+<p>对象的序列化过程是通过<code>ObjectOutputStream</code>和<code>ObjectInputputStream</code>来实现的。在<code>ObjectOutputStream</code>中<code>writeObject</code>的调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(&#34;stringlist&#34;));
+</span></span><span class="line"><span class="cl">objectOutputStream.writeObject(stringList);
+</span></span><span class="line"><span class="cl">IOUtils.close(objectOutputStream);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">writeObject
+</span></span><span class="line"><span class="cl">    ---&gt;writeObject0
+</span></span><span class="line"><span class="cl">    ---&gt;writeOrdinaryObject
+</span></span><span class="line"><span class="cl">    ---&gt;writeSerialData
+</span></span><span class="line"><span class="cl">    ---&gt;invokeWriteObject
+</span></span></code></pre></div><p>其中<code>invokeWriteObject</code>方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/** class-defined writeObject method, or null if none */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">Method</span><span class="w"> </span><span class="n">writeObjectMethod</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Invokes the writeObject method of the represented serializable class.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Throws UnsupportedOperationException if this class descriptor is not
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * associated with a class, or if the class is externalizable,
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * non-serializable or does not define writeObject.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">void</span><span class="w"> </span><span class="nf">invokeWriteObject</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">out</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">UnsupportedOperationException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">requireInitialized</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">writeObjectMethod</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// ========== 调用writeObject 方法 start========== //</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeObjectMethod</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="p">{</span><span class="w"> </span><span class="n">out</span><span class="w"> </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// ========== 调用writeObject 方法 end========== //</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InvocationTargetException</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Throwable</span><span class="w"> </span><span class="n">th</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ex</span><span class="p">.</span><span class="na">getTargetException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">th</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">IOException</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">throw</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="p">)</span><span class="w"> </span><span class="n">th</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">throwMiscException</span><span class="p">(</span><span class="n">th</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IllegalAccessException</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// should not occur, as access checks have been suppressed</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InternalError</span><span class="p">(</span><span class="n">ex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">UnsupportedOperationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>文档注释大意：调用表示的<code>serializable</code>类的<code>writeObject</code>方法，如果类描述符不与类相关联，或者该类是可外部化、不可序列化的，或者没有定义 <code>writeObject</code>，则抛出 <code>UnsupportedOperationException</code>。
+类定义的<code>writeObject</code>方法，如果没有则为<code>null</code>。</p>
+<p>所以基本可以确定是这个方法调用的，其中<code>writeObjectMethod.invoke(obj, new Object[]{ out });</code>是关键，而<code>writeObjectMethod</code>就是在序列化类中定义的<code>writeObject</code>方法，所以确实是通过反射的方式被调用了。</p>
+<h3 id="单例与序列化">单例与序列化</h3>
+<p>单例模式，是设计模式中最简单的一种。通过单例模式可以保证系统中一个类只有一个实例而且该实例易于外界访问，从而方便对实例个数的控制并节约系统资源。
+单例模式真的能够实现实例的唯一性吗？答案是否定的，很多人都知道使用反射可以破坏单例模式，除了反射以外，使用序列化与反序列化也同样会破坏单例。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">path</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;/Users/whitepure/github/iblog/blog-site/content/posts/rookie/singleton.txt&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//Write Obj to file</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="n">path</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">Singleton</span><span class="p">.</span><span class="na">getSingleton</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//Read Obj from file</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">path</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">file</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Singleton</span><span class="w"> </span><span class="n">newInstance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Singleton</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//判断是否是同一个对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">newInstance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Singleton</span><span class="p">.</span><span class="na">getSingleton</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">serialVersionUID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">6377402142849822126L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getSingleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">MainTest</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>输出结果为<code>false</code>，结论为<code>Singleton</code>的序列化与反序列化得到的对象是一个新的对象，所以序列化破坏了<code>Singleton</code>的单例性。</p>
+<p>对象的序列化过程是通过<code>ObjectOutputStream</code>和<code>ObjectInputputStream</code>来实现的。<code>ObjectInputStream</code>中<code>readObject</code>的调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(&#34;stringlist&#34;));
+</span></span><span class="line"><span class="cl">objectOutputStream.writeObject(stringList);
+</span></span><span class="line"><span class="cl">IOUtils.close(objectOutputStream);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">readObject
+</span></span><span class="line"><span class="cl">    ---&gt; readObject0
+</span></span><span class="line"><span class="cl">    ---&gt; readOrdinary
+</span></span><span class="line"><span class="cl">    ---&gt; checkResolve
+</span></span></code></pre></div><p>其中<code>readOrdinaryObject</code> 方法，文档注释大意：读取并返回&quot;ordinary&quot;(即，不是字符串、类、<code>ObjectStreamClass</code>、数组或枚举常量)对象，如果对象的类是不可解析的，则为<code>null</code>(在这种情况下，<code>ClassNotFoundException</code>将与对象的句柄相关联)。设置<code>passHandle</code>为对象的赋值句柄。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Reads and returns &#34;ordinary&#34; (i.e., not a String, Class,
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * ObjectStreamClass, array, or enum constant) object, or null if object&#39;s
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * class is unresolvable (in which case a ClassNotFoundException will be
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * associated with object&#39;s handle).  Sets passHandle to object&#39;s assigned
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * handle.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">readOrdinaryObject</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">unshared</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// `desc.isInstantiable()`: 如果一个 `serializable/externalizable` 的类可以在运行时被实例化，那么该方法就返回true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// `desc.newInstance`：该方法通过反射的方式调用无参构造方法新建一个对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">desc</span><span class="p">.</span><span class="na">isInstantiable</span><span class="p">()</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">desc</span><span class="p">.</span><span class="na">newInstance</span><span class="p">()</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="p">)</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidClassException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">desc</span><span class="p">.</span><span class="na">forClass</span><span class="p">().</span><span class="na">getName</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;unable to create instance&#34;</span><span class="p">).</span><span class="na">initCause</span><span class="p">(</span><span class="n">ex</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// hasReadResolveMethod:如果实现了serializable 或者 externalizable接口的类中包含readResolve则返回true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">obj</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">handles</span><span class="p">.</span><span class="na">lookupException</span><span class="p">(</span><span class="n">passHandle</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">desc</span><span class="p">.</span><span class="na">hasReadResolveMethod</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// invokeReadResolve:通过反射的方式调用要被反序列化的类的readResolve方法。</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Object</span><span class="w"> </span><span class="n">rep</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">desc</span><span class="p">.</span><span class="na">invokeReadResolve</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">unshared</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">rep</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">isArray</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">rep</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cloneArray</span><span class="p">(</span><span class="n">rep</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">obj</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>desc.isInstantiable</code>方法作用是，如果一个<code>serializable</code>/<code>externalizable</code>的类可以在运行时被实例化，那么该方法就返回<code>true</code>。
+如果返回<code>true</code>，就会触发<code>desc.newInstance</code>方法执行，该方法通过反射的方式调用无参构造方法新建一个对象。
+所以序列化破坏单例的原因是调用了<code>desc.newInstance</code>方法，从而序列化会通过反射调用无参数的构造方法创建一个新的对象。</p>
+<p>原因清楚了之后，那怎么解决呢？继续向下看<code>readOrdinaryObject</code>方法代码。
+<code>hasReadResolveMethod</code>方法的作用，如果实现了<code>serializable</code>或者<code>externalizable</code>接口的类中包含<code>readResolve</code>则返回<code>true</code>。
+<code>invokeReadResolve</code>是通过反射的方式调用要被反序列化的类的<code>readResolve</code>方法。
+所以在<code>Singleton</code>中定义<code>readResolve</code>方法，并在该方法中指定要返回的对象的生成策略，就可以防止单例被破坏。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">serialVersionUID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">6377402142849822126L</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getSingleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">MainTest</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">readResolve</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="io模型">IO模型</h2>
+<p>在Unix操作系统中，常见的IO模型有以下五种：阻塞IO、非阻塞IO、信号驱动IO、IO多路转接、异步IO。其中，前四个被称为同步IO。</p>
+<h3 id="阻塞式io模型">阻塞式IO模型</h3>
+<p>BIO（<code>Blocking IO</code>），最传统的一种IO模型，即在读写数据过程中会发生阻塞现象。</p>
+<p>当用户线程发出IO请求之后，内核会去查看数据是否就绪，如果没有就绪就会等待数据就绪，而用户线程就会处于阻塞状态，用户线程交出CPU。
+当数据就绪之后，内核会将数据拷贝到用户线程，并返回结果给用户线程，用户线程才解除<code>block</code>状态。</p>
+<p>BIO编程简单，易于理解和实现，但因为一个请求IO会阻塞进程，不能充分利用CPU，导致低效的资源使用，特别是在处理大量连接时。
+所以不适用并发量大的应用，适用并发量小的网络应用开发。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try (Socket socket = new Socket(&#34;example.com&#34;, 80);
+</span></span><span class="line"><span class="cl">     InputStream input = socket.getInputStream();
+</span></span><span class="line"><span class="cl">     OutputStream output = socket.getOutputStream()) {
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    output.write(&#34;GET / HTTP/1.1\r\n\r\n&#34;.getBytes());
+</span></span><span class="line"><span class="cl">    int data;
+</span></span><span class="line"><span class="cl">    while ((data = input.read()) != -1) {
+</span></span><span class="line"><span class="cl">        System.out.print((char) data);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">} catch (IOException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h3 id="非阻塞io模型">非阻塞IO模型</h3>
+<p>NIO（<code>NoBlocking IO</code>），当用户线程发起一个<code>read</code>操作后，并不需要等待，而是马上就得到了一个结果。
+如果结果是一个<code>error</code>时，它就知道数据还没有准备好，于是它可以再次发送<code>read</code>操作。
+一旦内核中的数据准备好了，并且又再次收到了用户线程的请求，那么它马上就将数据拷贝到了用户线程然后返回。</p>
+<p>在NIO中，IO操作立即返回，不会阻塞线程，所以线程可以在数据未准备好时执行其他任务。
+用户线程需要不断地询问内核数据是否就绪，也就说非阻塞IO不会交出CPU，而会一直占用CPU。</p>
+<p>NIO虽然线程不会被IO操作阻塞，可以同时处理多个连接，但编程复杂度较高，需要处理非阻塞逻辑和轮询。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try (SocketChannel socketChannel = SocketChannel.open()) {
+</span></span><span class="line"><span class="cl">    socketChannel.configureBlocking(false);
+</span></span><span class="line"><span class="cl">    socketChannel.connect(new InetSocketAddress(&#34;example.com&#34;, 80));
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    while (!socketChannel.finishConnect()) {
+</span></span><span class="line"><span class="cl">        // 做其他事情
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    ByteBuffer buffer = ByteBuffer.allocate(1024);
+</span></span><span class="line"><span class="cl">    int bytesRead = socketChannel.read(buffer);
+</span></span><span class="line"><span class="cl">} catch (IOException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>需要注意的是<code>Java NIO</code>不是IO模型中的NIO模型，而是IO多路复用模型。</p>
+<h3 id="io复用模型">IO复用模型</h3>
+<p>IO复用模型，一个线程不断去轮询多个<code>socket</code>的状态，只有当<code>socket</code>真正有读写事件时，才真正调用实际的IO读写操作。
+在多路复用IO模型中，只需要使用一个线程就可以管理多个<code>socket</code>，系统不需要建立新的进程或者线程，也不必维护这些线程和进程，并且只有在真正有<code>socket</code>读写事件进行时，才会使用IO资源，所以它大大减少了资源占用。</p>
+<p><code>Java NIO</code>实际上就是多路复用IO，通过<code>selector.select()</code>查询每个通道是否有到达事件，如果没有事件则一直阻塞在那里。
+因此这种方式会导致用户线程的阻塞，所以多路复用IO比较适合连接数比较多的情况。</p>
+<p><img alt="IO多路复用模型" src="/iblog/posts/annex/images/essays/IO%E5%A4%9A%E8%B7%AF%E5%A4%8D%E7%94%A8%E6%A8%A1%E5%9E%8B.png"></p>
+<p>单线程可以处理多个通道，提高资源利用率，性能好。适用高并发服务应用开发，一个进程响应多个请求，但编程复杂度较高，需要处理选择器和事件。
+常用的实现方式包括<code>select</code>、<code>poll</code>和<code>epoll</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try (Selector selector = Selector.open();
+</span></span><span class="line"><span class="cl">     ServerSocketChannel serverChannel = ServerSocketChannel.open()) {
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    serverChannel.bind(new InetSocketAddress(8080));
+</span></span><span class="line"><span class="cl">    serverChannel.configureBlocking(false);
+</span></span><span class="line"><span class="cl">    serverChannel.register(selector, SelectionKey.OP_ACCEPT);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    while (true) {
+</span></span><span class="line"><span class="cl">        selector.select();
+</span></span><span class="line"><span class="cl">        Set&lt;SelectionKey&gt; selectedKeys = selector.selectedKeys();
+</span></span><span class="line"><span class="cl">        Iterator&lt;SelectionKey&gt; iter = selectedKeys.iterator();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        while (iter.hasNext()) {
+</span></span><span class="line"><span class="cl">            SelectionKey key = iter.next();
+</span></span><span class="line"><span class="cl">            if (key.isAcceptable()) {
+</span></span><span class="line"><span class="cl">                // 处理接受事件
+</span></span><span class="line"><span class="cl">            } else if (key.isReadable()) {
+</span></span><span class="line"><span class="cl">                // 处理读取事件
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            iter.remove();
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">} catch (IOException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><blockquote>
+<p>多路复用IO为何比非阻塞IO模型的效率高？
+因为在非阻塞IO中，不断地询问<code>socket</code>状态是通过用户线程去进行的，而在多路复用IO中，轮询每个<code>socket</code>状态是内核在进行的，这个效率要比用户线程要高的多。</p>
+</blockquote>
+<p>要注意的是，多路复用IO模型是通过轮询的方式来检测是否有事件到达，并且对到达的事件逐一进行响应。
+因此对于多路复用IO模型来说，一旦事件响应体很大，那么就会导致后续的事件迟迟得不到处理，并且会影响新的事件轮询。</p>
+<h3 id="信号驱动io模型">信号驱动IO模型</h3>
+<p>当用户线程发起一个IO请求操作，会给对应的<code>socket</code>注册一个信号函数，然后用户线程会继续执行不阻塞，当内核数据就绪时会发送一个信号给用户线程，用户线程接收到信号之后，便在信号函数中调用IO读写操作来进行实际的IO请求操作。</p>
+<p>在Java中，信号驱动IO模型不常见，更多用于<code>Unix/Linux</code>系统编程，通过<code>sigaction</code>和<code>SIGIO</code>信号实现。
+虽然信号驱动IO不需要轮询，避免了CPU资源浪费，但是编程复杂，依赖于操作系统的信号机制，且跨平台支持较差，开发中使用较少。</p>
+<h3 id="异步io模型">异步IO模型</h3>
+<p>AIO（<code>Async IO</code>）模型是比较理想的IO模型，当用户线程发起IO操作后，立刻就可以开始去做其它的事。
+从内核的角度看，当它收到一个IO请求之后，它会立刻返回给用户线程，说明IO请求已经成功发起了，因此不会对用户线程产生任何阻塞。
+然后，内核会等待数据准备完成，然后将数据拷贝到用户线程，当这一切都完成之后，内核会给用户线程发送一个信号，告诉它IO操作完成了。</p>
+<p>用户线程完全不需要知道实际的整个IO操作是如何进行的，只需要先发起一个请求，当接收内核返回的成功信号时表示IO操作已经完成，可以直接去使用数据了。</p>
+<p>在异步IO模型中，IO操作的两个阶段都不会阻塞用户线程，这两个阶段都是由内核自动完成，然后发送一个信号告知用户线程操作已完成。
+用户线程中不需要再次调用IO函数进行具体的读写。这点是和信号驱动模型有所不同的，在信号驱动模型中，当用户线程接收到信号表示数据已经就绪，然后需要用户线程调用IO函数进行实际的读写操作；
+而在异步IO模型中，收到信号表示IO操作已经完成，不需要再在用户线程中调用IO函数进行实际的读写操作。</p>
+<p>AIO不会阻塞线程，适用于高并发和低延迟的应用场景，但编程复杂度较高，需要处理异步操作和回调。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try (AsynchronousSocketChannel client = AsynchronousSocketChannel.open()) {
+</span></span><span class="line"><span class="cl">    Future&lt;Void&gt; connectFuture = client.connect(new InetSocketAddress(&#34;example.com&#34;, 80));
+</span></span><span class="line"><span class="cl">    connectFuture.get();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    ByteBuffer buffer = ByteBuffer.allocate(1024);
+</span></span><span class="line"><span class="cl">    Future&lt;Integer&gt; readFuture = client.read(buffer);
+</span></span><span class="line"><span class="cl">    readFuture.get();
+</span></span><span class="line"><span class="cl">} catch (IOException | InterruptedException | ExecutionException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h2 id="nio">NIO</h2>
+<p>NIO解释为<code>New IO</code>或<code>Non Blocking IO</code>是从Java 1.4 版本开始引入的一个新的IO API，可以替代标准的<code>Java IO</code>API。
+NIO支持面向缓冲区的、基于通道的IO操作，所以NIO将以更加高效的方式进行文件的读写操作。</p>
+<p>Java中的NIO是一个非常重要的部分，尤其是在处理高性能、高并发的应用时。NIO提供了一种比传统的阻塞IO更高效的方式来处理IO操作。
+<code>Java NIO</code>属于IO多路复用模型，只不过<code>Java NIO</code>组件提供了统一的应用开发API，屏蔽了底层的操作系统的差异。<code>Java NIO</code>类库包含以下三个核心组件：</p>
+<ul>
+<li>Channel（通道）</li>
+<li>Buffer（缓冲区）</li>
+<li>Selector（选择器）</li>
+</ul>
+<h3 id="对比传统io">对比传统IO</h3>
+<table>
+<thead>
+<tr>
+<th>区别</th>
+<th>传统IO</th>
+<th>NIO</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>传输方式</td>
+<td>面向流，通过流传输</td>
+<td>面向缓冲区，通过缓冲区传输</td>
+</tr>
+<tr>
+<td>是否阻塞</td>
+<td>阻塞IO</td>
+<td>非阻塞IO</td>
+</tr>
+<tr>
+<td>其他</td>
+<td>无</td>
+<td>选择器，可以解决阻塞问题</td>
+</tr>
+</tbody>
+</table>
+<p>什么是面向流？什么是面向缓冲区呢？
+在传统IO操作中，IO的<code>read</code>操作总是以流式的方式顺序地从一个流中读取一个或多个字节，因此，我们不能随意地改变读取指针的位置，也不能前后移动流中的数据。
+而NIO中引入了<code>Channel</code>（通道）和<code>Buffer</code>（缓冲区）的概念。面向缓冲区的读取和写入，都是与<code>Buffer</code>进行交互。
+用户程序只需要从通道中读取数据到缓冲区中，或将数据从缓冲区中写入到通道中。NIO不像OIO那样是顺序操作，可以随意地读取<code>Buffer</code>中任意位置的数据，可以随意修改<code>Buffer</code>中任意位置的数据。</p>
+<p>传统IO的操作是堵塞的，当一个线程调用<code>read()</code>或<code>write()</code>时，该线程被阻塞，直到有一些数据被读取，或数据完全写入，该线程在此期间不能再干任何事情了。
+NIO如何做到非阻塞的呢？当调用<code>read</code>方法时，系统底层已经把数据准备好了，应用程序只需要从通道把数据复制到<code>Buffer</code>（缓冲区）就行。
+如果没有数据，当前线程可以去干别的事情，不需要进行阻塞等待。根本原因是NIO使用了通道和通道的IO多路复用技术。</p>
+<h3 id="通道">通道</h3>
+<p>通道(<code>Channel</code>)用于源节点与目标节点的连接，在<code>Java NIO</code>中负责缓冲区中数据的传输。<code>Channel</code>本身不存储数据，需要配合缓冲区进行数据传输。
+<code>Channel</code>的角色和传统IO中的<code>Stream</code>是差不多的。在NIO中，一个网络连接使用一个通道表示，所有的NIO的IO操作都是通过连接通道完成的。
+一个通道类似于传统IO中的两个流的结合体，既可以从通道读取数据，也可以向通道写入数据。</p>
+<p><img alt="IO" src="/iblog/posts/annex/images/essays/IO%E4%B8%8ENIO-1.png"></p>
+<p><img alt="NIO" src="/iblog/posts/annex/images/essays/IO%E4%B8%8ENIO-2.png"></p>
+<p>通道的主要实现类：</p>
+<ul>
+<li><code>FileChannel</code>：用于读取、写入、映射和操作文件的通道。</li>
+<li><code>SocketChannel</code>：通过TCP读写网络中的数据。</li>
+<li><code>ServerSocketChannel</code>：可以监听新进来的TCP连接，对每一个新进来的连接都会创建一个<code>SocketChannel</code>。</li>
+<li><code>DatagramChannel</code>：通过UDP读写网络中的数据通道。</li>
+</ul>
+<p>Java针对支持通道的类提供了<code>getChannel()</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 使用非直接缓冲区完成读写操作
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param args args
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">start</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 获取通道</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">FileChannel</span><span class="w"> </span><span class="n">inChannel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="s">&#34;1.jpg&#34;</span><span class="p">).</span><span class="na">getChannel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">FileChannel</span><span class="w"> </span><span class="n">outChannel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="s">&#34;2.jpg&#34;</span><span class="p">).</span><span class="na">getChannel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 分配指定大小的缓冲区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ByteBuffer</span><span class="p">.</span><span class="na">allocate</span><span class="p">(</span><span class="n">1024</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将通道中的数据存入缓冲区中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">inChannel</span><span class="p">.</span><span class="na">read</span><span class="p">(</span><span class="n">buf</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 切换读取数据的模式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">buf</span><span class="p">.</span><span class="na">flip</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 将缓冲区中的数据写入通道中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">outChannel</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="n">buf</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 清空缓冲区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">buf</span><span class="p">.</span><span class="na">clear</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">long</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;耗费的时间为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">end</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">start</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="缓冲区">缓冲区</h3>
+<p>通道负责传输，缓冲区负责存储，缓冲区底层实现是数组，用于存储不同类型的数据。
+若需要使用NIO，需要获取用于连接IO设备的通道以及用于容纳数据的缓冲区，然后操作缓冲区，对数据进行处理。</p>
+<p><code>Channel</code>提供从文件、网络读取数据的渠道，但是读写的数据都必须经过Buffer。
+所谓通道的读取，就是将数据从通道读取到缓冲区中；所谓通道的写入，就是将数据从缓冲区中写入到通道中。缓冲区的使用，是面向流进行读写操作的OIO所没有的，也是NIO非阻塞的重要前提和基础之一。</p>
+<p>根据数据类型的不同(<code>boolean</code>除外)，有以下<code>Buffer</code>常用子类：</p>
+<ul>
+<li><code>ByteBuffer</code>：用于存储字节数据</li>
+<li><code>CharBuffer</code>：用于存储字符数据</li>
+<li><code>ShortBuffer</code>：用于存储短整型数据</li>
+<li><code>IntBuffer</code>：用于存储整型数据</li>
+<li><code>LongBuffer</code>：用于存储长整型数据</li>
+<li><code>FloatBuffer</code>：用于存储浮点型数据</li>
+<li><code>DoubleBuffer</code>：用于存储双精度浮点型数据</li>
+</ul>
+<p>在父类抽象类<code>Buffer</code>中存在四个核心属性：</p>
+<ul>
+<li><code>capacity</code>：容量，表示缓冲区中最大存储数据的容量，一旦声明不能改变。一旦写入的对象数量超过了<code>capacity</code>容量，缓冲区就满了，不能再写入了。</li>
+<li><code>limit</code>：界限，表示缓冲区中可以写入或者读取的最大上限，<code>limit</code>后数据不能进行读写。</li>
+<li><code>position</code>：位置，表示缓冲区中正在操作数据的位置。</li>
+<li><code>mark</code>：标记，用于暂存<code>position</code>的值，可以通过<code>reset()</code>恢复到<code>mark</code>的位置。</li>
+</ul>
+<p>当向缓冲区写入数据时，缓冲区处于写模式。在写模式下，数据写入缓冲区，并更新位置属性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ByteBuffer buffer = ByteBuffer.allocate(10);
+</span></span><span class="line"><span class="cl">buffer.put((byte) 1);
+</span></span><span class="line"><span class="cl">buffer.put((byte) 2);
+</span></span><span class="line"><span class="cl">buffer.put((byte) 3);
+</span></span><span class="line"><span class="cl">// 此时，位置 position = 3，容量 capacity = 10，限制 limit = 10
+</span></span></code></pre></div><p>在读数据之前，需要调用<code>flip()</code>方法将缓冲区从写模式切换到读模式。<code>flip()</code>方法将限制设置为当前位置，然后将位置重置为零。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">buffer.flip();
+</span></span><span class="line"><span class="cl">// 此时，位置 position = 0，限制 limit = 3，容量 capacity = 10
+</span></span></code></pre></div><p>在读模式下，可以从缓冲区读取数据。每次读取操作都会更新位置属性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">while (buffer.hasRemaining()) {
+</span></span><span class="line"><span class="cl">    // 输出：1, 2, 3
+</span></span><span class="line"><span class="cl">    System.out.println(buffer.get());
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>读完数据后，可以调用<code>clear()</code>方法将位置重置为零，限制设置为容量，用于准备再次写入整个缓冲区的数据。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">buffer.clear();
+</span></span><span class="line"><span class="cl">// 此时，位置 position = 0，限制 limit = 10，容量 capacity = 10
+</span></span></code></pre></div><p><code>compact()</code>方法将未读的数据复制到缓冲区的开始位置，然后将位置设置为未读数据的数量。适用于继续写入缓冲区但保留未读数据的情况。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">buffer.compact();
+</span></span><span class="line"><span class="cl">// 此时，未读的数据被移到缓冲区的开始位置，位置 position 设置为未读数据的数量
+</span></span></code></pre></div><p>完整代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BufferExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个容量为10的ByteBuffer</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ByteBuffer</span><span class="p">.</span><span class="na">allocate</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 写入数据到缓冲区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 写入数据后的缓冲区状态:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 位置 (Position): 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 限制 (Limit): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 容量 (Capacity): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;写入数据后的缓冲区状态:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printBufferStatus</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 翻转缓冲区，准备读取</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">flip</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 翻转缓冲区后的状态:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 位置 (Position): 0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 限制 (Limit): 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 容量 (Capacity): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;翻转缓冲区后的状态:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printBufferStatus</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;读取数据:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">buffer</span><span class="p">.</span><span class="na">hasRemaining</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">buffer</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取数据后的缓冲区状态:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 位置 (Position): 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 限制 (Limit): 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 容量 (Capacity): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;读取数据后的缓冲区状态:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printBufferStatus</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 清空缓冲区，准备再次写入</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">clear</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 清空缓冲区后的状态:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 位置 (Position): 0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 限制 (Limit): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 容量 (Capacity): 10</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;清空缓冲区后的状态:&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printBufferStatus</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printBufferStatus</span><span class="p">(</span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;位置 (Position): &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">position</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;限制 (Limit): &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">limit</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;容量 (Capacity): &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">capacity</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>mark</code>方法，记录当前<code>position</code>位置，可以通过<code>reset()</code>恢复到<code>mark</code>的位置。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BufferMarkResetExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个容量为10的ByteBuffer</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ByteBuffer</span><span class="p">.</span><span class="na">allocate</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 写入数据到缓冲区</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 标记当前位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">mark</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;标记位置 (Position)：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">position</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 继续写入数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前缓冲区位置 (Position)：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">position</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 调用reset()方法恢复到标记的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">reset</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;重置后的位置 (Position)：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">position</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 从标记的位置继续写入数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">put</span><span class="p">((</span><span class="kt">byte</span><span class="p">)</span><span class="w"> </span><span class="n">6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 翻转缓冲区，准备读取</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">buffer</span><span class="p">.</span><span class="na">flip</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;读取数据：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">buffer</span><span class="p">.</span><span class="na">hasRemaining</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">buffer</span><span class="p">.</span><span class="na">get</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="选择器">选择器</h3>
+<p>选择器是<code>Java NIO</code>中的一个核心组件，允许单个线程管理多个通道（<code>Channel</code>）。它可以监控多个通道的IO事件，例如数据是否准备好读取、是否可以写入等。
+通过选择器，应用程序可以在一个线程中同时管理多个通道的IO操作，而不必为每个通道创建一个单独的线程，这样可以提高系统资源利用率和应用程序的性能。</p>
+<blockquote>
+<p>什么是IO事件呢？
+表示通道某种IO操作已经就绪、或者说已经做好了准备。例如，如果一个新<code>Channel</code>链接建立成功了，就会在<code>Server Socket Channel</code>上发生一个IO事件，代表一个新连接一个准备好，这个IO事件叫做“接收就绪”事件。</p>
+</blockquote>
+<p><code>Selector</code>的本质，就是去查询这些IO就绪事件，所以，它的名称就叫做<code>Selector</code>查询者。
+从编程实现维度来说，IO多路复用编程的第一步，是把通道注册到选择器中，第二步则是通过选择器所提供的事件查询方法，这些注册的通道是否有已经就绪的IO事件。</p>
+<p>与传统IO相比，NIO使用选择器的最大优势就是系统开销小，系统不必为每一个网络连接创建进程/线程。
+通过<code>Java NIO</code>可以达到一个线程负责多个连接通道的IO处理，这是非常高效的。这种高效，恰恰就来自于Java的选择器组件<code>Selector</code>以及其底层的操作系统IO多路复用技术的支持。</p>
+<p>选择器的使命是完成IO的多路复用，其主要工作是通道的注册、监听、事件查询。
+一个通道代表一条连接通路，通过选择器可以同时监控多个通道的IO（输入输出）状况。选择器和通道的关系，是监控和被监控的关系。</p>
+<p><img alt="selector示意图" src="/iblog/posts/annex/images/essays/selector%E7%A4%BA%E6%84%8F%E5%9B%BE.png"></p>
+<p>使用选择器，首先需要通过<code>Selector.open()</code>方法创建一个选择器对象。选择器允许单个线程管理多个通道的IO操作，实现了IO多路复用的机制。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Selector selector = Selector.open();
+</span></span></code></pre></div><p>通过<code>register</code>方法将通道注册到选择器上，并指定选择器要监控的IO事件类型，可供选择器监控的通道IO事件类型，包括以下四种：</p>
+<ul>
+<li>可读：<code>SelectionKey.OP_READ</code></li>
+<li>可写：<code>SelectionKey.OP_WRITE</code></li>
+<li>连接：<code>SelectionKey.OP_CONNECT</code></li>
+<li>接收：<code>SelectionKey.OP_ACCEPT</code></li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
+</span></span><span class="line"><span class="cl">serverSocketChannel.configureBlocking(false); // 非阻塞模式
+</span></span><span class="line"><span class="cl">serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
+</span></span></code></pre></div><p>使用选择器的<code>select()</code>方法阻塞，直到至少有一个通道准备好进行IO操作，并处理每个发生的事件。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">selector.select(); // 阻塞直到有通道发生了注册的事件
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Set&lt;SelectionKey&gt; selectedKeys = selector.selectedKeys();
+</span></span><span class="line"><span class="cl">Iterator&lt;SelectionKey&gt; keyIterator = selectedKeys.iterator();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">while (keyIterator.hasNext()) {
+</span></span><span class="line"><span class="cl">    SelectionKey key = keyIterator.next();
+</span></span><span class="line"><span class="cl">    keyIterator.remove();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    if (key.isAcceptable()) {
+</span></span><span class="line"><span class="cl">        // 处理接受连接事件
+</span></span><span class="line"><span class="cl">        handleAccept(key, selector);
+</span></span><span class="line"><span class="cl">    } else if (key.isReadable()) {
+</span></span><span class="line"><span class="cl">        // 处理读事件
+</span></span><span class="line"><span class="cl">        handleRead(key);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>当有客户端连接时，我们通过服务端通道接受连接，并将客户端通道注册为读事件。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleAccept</span><span class="p">(</span><span class="n">SelectionKey</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">Selector</span><span class="w"> </span><span class="n">selector</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ServerSocketChannel</span><span class="w"> </span><span class="n">serverChannel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">ServerSocketChannel</span><span class="p">)</span><span class="w"> </span><span class="n">key</span><span class="p">.</span><span class="na">channel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SocketChannel</span><span class="w"> </span><span class="n">clientChannel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">serverChannel</span><span class="p">.</span><span class="na">accept</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">clientChannel</span><span class="p">.</span><span class="na">configureBlocking</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">clientChannel</span><span class="p">.</span><span class="na">register</span><span class="p">(</span><span class="n">selector</span><span class="p">,</span><span class="w"> </span><span class="n">SelectionKey</span><span class="p">.</span><span class="na">OP_READ</span><span class="p">);</span><span class="w"> </span><span class="c1">// 注册读事件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Accepted connection from &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">clientChannel</span><span class="p">.</span><span class="na">getRemoteAddress</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>读事件发生时，我们从通道中读取数据，并进行相应的处理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRead</span><span class="p">(</span><span class="n">SelectionKey</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SocketChannel</span><span class="w"> </span><span class="n">channel</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">SocketChannel</span><span class="p">)</span><span class="w"> </span><span class="n">key</span><span class="p">.</span><span class="na">channel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ByteBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ByteBuffer</span><span class="p">.</span><span class="na">allocate</span><span class="p">(</span><span class="n">1024</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">bytesRead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">channel</span><span class="p">.</span><span class="na">read</span><span class="p">(</span><span class="n">buffer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">bytesRead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 客户端关闭连接</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">channel</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">key</span><span class="p">.</span><span class="na">cancel</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Closed connection: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">channel</span><span class="p">.</span><span class="na">getRemoteAddress</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">buffer</span><span class="p">.</span><span class="na">flip</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">buffer</span><span class="p">.</span><span class="na">remaining</span><span class="p">()</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">buffer</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">data</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Received: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="n">data</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">buffer</span><span class="p">.</span><span class="na">clear</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="参考文章">参考文章</h2>
+<ul>
+<li><a href="http://hollischuang.gitee.io/tobetopjavaer">http://hollischuang.gitee.io/tobetopjavaer</a></li>
+<li><a href="https://docs.oracle.com/javase/7/docs/api/java/io/Externalizable.html">https://docs.oracle.com/javase/7/docs/api/java/io/Externalizable.html</a></li>
+<li><a href="https://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html">https://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html</a></li>
+<li><a href="https://blog.csdn.net/crazymakercircle/article/details/120946903">https://blog.csdn.net/crazymakercircle/article/details/120946903</a></li>
+</ul>
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+	<title>Java集合 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="概述 Java中的集合主要包括Collection和Map两种，Collection存储着对象的集合，而Map存储着键值对的映射表。 数组 如果你看过ArrayLis" />
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+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+</head>
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+<body>
+    <div class="post-password">
+        
+    </div>
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+    
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+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%bf%b0">
+                    概述
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e7%bb%84">
+                    数组
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%98%e9%95%bf%e5%8f%82%e6%95%b0">
+                    变长参数
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9a%e4%b9%89%e6%95%b0%e7%bb%84">
+                    定义数组
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%81%8d%e5%8e%86%e6%95%b0%e7%bb%84">
+                    遍历数组
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e7%bb%84%e5%8e%bb%e9%87%8d">
+                    数组去重
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%95%b0%e7%bb%84%e8%bd%ac%e9%9b%86%e5%90%88">
+                    数组转集合
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#arraylist">
+                    ArrayList
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#randomaccess">
+                    RandomAccess
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cloneable">
+                    Cloneable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#arraylist%e6%89%a9%e5%ae%b9">
+                    ArrayList扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#arraylist%e4%b8%8elinkedlist">
+                    ArrayList与LinkedList
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#arraylist%e5%ae%89%e5%85%a8%e5%88%a0%e9%99%a4">
+                    ArrayList安全删除
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashset">
+                    HashSet
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8e%bb%e9%87%8d%e5%8e%9f%e7%90%86">
+                    去重原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#equals%e4%b8%8ehashcode">
+                    equals与hashCode
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8-1">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#queue">
+                    Queue
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap">
+                    HashMap
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e7%bb%93%e6%9e%84">
+                    HashMap结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hash%e5%86%b2%e7%aa%81">
+                    Hash冲突
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e5%ae%b9%e9%87%8f">
+                    HashMap容量
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashmap%e6%89%a9%e5%ae%b9">
+                    HashMap扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#17%e6%89%a9%e5%ae%b9">
+                    1.7扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#18%e6%89%a9%e5%ae%b9">
+                    1.8扩容
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8-2">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
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+
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+                        <h2 id="post_single_title">Java集合</h2>
+                        <span id="post_page_title_date" class="date">2021.10.04</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概述">概述</h2>
+<p>Java中的集合主要包括<code>Collection</code>和<code>Map</code>两种，<code>Collection</code>存储着对象的集合，而<code>Map</code>存储着键值对的映射表。</p>
+<p><img alt="Java中的集合-01" src="/iblog/posts/annex/images/essays/Java%E4%B8%AD%E7%9A%84%E9%9B%86%E5%90%88-01.jpg"></p>
+<h2 id="数组">数组</h2>
+<p>如果你看过<code>ArrayList</code>类源码，就知道<code>ArrayList</code>底层是通过数组来存储元素的，所以如果严格来说，数组也算集合的一种。
+Java中提供的数组是用来存储固定大小的同类型元素，所以Java数组就是同类数据元素的集合。
+在Java中，数组是一种非常常用的数据结构，用于存储同一类型的一组元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 定义一个整数数组
+</span></span><span class="line"><span class="cl">int[] intArray;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 初始化数组并赋值
+</span></span><span class="line"><span class="cl">intArray = new int[5]; // 数组长度为5，每个元素默认值为0
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 定义并初始化数组
+</span></span><span class="line"><span class="cl">int[] anotherArray = {1, 2, 3, 4, 5}; // 定义并同时赋值
+</span></span></code></pre></div><p>数组是引用数据类型，如果使用了没有开辟空间的数组，则一定会出现<code>NullPointerException</code>异常信息。
+所以数组本质上也是Java对象，能够向下或者向上转型，能使用<code>instanceof</code>关键字。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int[] intArray; // 声明数组但未初始化
+</span></span><span class="line"><span class="cl">System.out.println(intArray[0]); // 这将导致 NullPointerException
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Object obj = new int[5]; // 向上转型
+</span></span><span class="line"><span class="cl">if (obj instanceof int[]) {
+</span></span><span class="line"><span class="cl">int[] array = (int[]) obj; // 向下转型
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Successfully casted obj to int[]&#34;);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>数组由于其连续的内存分配和高效的下标访问，具有高访问效率，但其固定大小、插入删除低效、单一类型限制和高内存要求使其在实际应用中不如集合灵活，
+所以我们应该优选集合，而不是数组。只有在已证明性能成为问题的时候，并且确定切换到数组对性能提高有帮助时，才应该将项目重构为使用数组。</p>
+<h3 id="变长参数">变长参数</h3>
+<p>在Java中，变长参数在方法定义中处理方式与数组相同。
+变长参数允许你传递任意数量的参数到一个方法中，编译时会将其处理为一个数组。例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public void methodName(int... values) {
+</span></span><span class="line"><span class="cl">    for (int value : values) {
+</span></span><span class="line"><span class="cl">        System.out.println(value);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// 在这个方法中，可以传递任意数量的整数
+</span></span><span class="line"><span class="cl">methodName(1, 2, 3); // 传递三个参数
+</span></span><span class="line"><span class="cl">methodName(4, 5); // 传递两个参数
+</span></span><span class="line"><span class="cl">methodName(); // 传递零个参数
+</span></span></code></pre></div><p>一个方法只能有一个变长参数，即使是不同类型也不行。并且变长参数必须是方法参数列表中的最后一个参数。</p>
+<h3 id="定义数组">定义数组</h3>
+<p>由于数组没有提供任何的封装，所有对元素的操作，都是通过自定义的方法实现的，对数组元素的操作比较麻烦，好在Java自带了一些API供开发者调用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="w"> </span><span class="p">};</span><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="p">{</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span></code></pre></div><p>需要注意的是[]，写在数组名称的前后都可以，但是推荐第一种写法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">array2</span><span class="o">[]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="n">4</span><span class="p">,</span><span class="n">5</span><span class="w"> </span><span class="p">};</span><span class="w">
+</span></span></span></code></pre></div><h3 id="遍历数组">遍历数组</h3>
+<p>在Java中，遍历数组有多种不同的方式，每种方式适合不同的情况和需求。以下是几种常见的遍历数组的方式：</p>
+<ol>
+<li>使用普通for循环；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int[] array = {1, 2, 3, 4, 5};
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">for (int i = 0; i &lt; array.length; i++) {
+</span></span><span class="line"><span class="cl">    System.out.println(array[i]);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>使用增强for循环；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int[] array = {1, 2, 3, 4, 5};
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">for (int num : array) {
+</span></span><span class="line"><span class="cl">    System.out.println(num);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>使用Java 8的<code>Stream API</code>；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int[] array = {1, 2, 3, 4, 5};
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">Arrays.stream(array).forEach(num -&gt; System.out.println(num));
+</span></span></code></pre></div></li>
+</ol>
+<h3 id="数组去重">数组去重</h3>
+<ol>
+<li>如果数组元素是对象类型（如<code>String</code>、<code>Integer</code>等），可以利用集合类的特性来进行去重。这种方法简单直接，适用于不需要保持原始顺序的情况；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayDuplicateRemoval</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用Set去重</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedHashSet</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">array</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="o">[]</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">set</span><span class="p">.</span><span class="na">toArray</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Integer</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出去重后的数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">result</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>Java 8引入的<code>Stream API</code>提供了一种更加函数式和流畅的方式进行数组去重。这种方法同样适用于对象类型数组，且可以保持元素的原始顺序；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayDuplicateRemoval</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用Stream API去重</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="o">[]</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">stream</span><span class="p">(</span><span class="n">array</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                 </span><span class="p">.</span><span class="na">distinct</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                 </span><span class="p">.</span><span class="na">toArray</span><span class="p">(</span><span class="n">Integer</span><span class="o">[]</span><span class="p">::</span><span class="k">new</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出去重后的数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">result</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<h3 id="数组转集合">数组转集合</h3>
+<ol>
+<li>使用<code>Arrays.asList</code>方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayToCollection</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;A&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;B&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;D&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数组转换为List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">array</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>使用<code>Collections.addAll</code>方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayToCollection</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;A&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;B&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;D&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个空的List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数组元素添加到List中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Collections</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">list</span><span class="p">,</span><span class="w"> </span><span class="n">array</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>使用<code>Stream API</code>；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayToCollection</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 示例数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;A&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;B&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;D&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 将数组转换为List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Stream</span><span class="p">.</span><span class="na">of</span><span class="p">(</span><span class="n">array</span><span class="p">).</span><span class="na">collect</span><span class="p">(</span><span class="n">Collectors</span><span class="p">.</span><span class="na">toList</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出List</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<h2 id="arraylist">ArrayList</h2>
+<p>在<code>List</code>接口实现类中，最常用的就是<code>ArrayList</code>，<code>ArrayList</code>类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删除元素。
+<code>ArrayList</code>继承了<code>AbstractList</code>，并实现了<code>List</code>、<code>RandomAccess</code>，<code>Cloneable</code>接口：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">RandomAccess</span><span class="p">,</span><span class="n">Cloneable</span><span class="p">,</span><span class="n">Serializable</span><span class="p">{}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="randomaccess">RandomAccess</h3>
+<p><code>Random</code>是随机的意思，<code>Access</code>是访问的意思，合起来<code>RandomAccess</code>就是随机访问的意思。
+<code>RandomAccess</code>接口是一个标记接口，用来标记实现的<code>List</code>集合具备快速随机访问的能力。
+所有的<code>List</code>实现都支持随机访问的，只是基于基本结构的不同，实现的速度不同罢了。</p>
+<p>当一个<code>List</code>拥有快速访问功能时，其遍历方法采用随机访问速度最快，而没有快速随机访问的<code>List</code>采用顺序访问的速度最快。
+如果集合中的数据量过大需要遍历时，此时需要格外注意，因为不同的遍历方式会影响很大，可以使用<code>instanceof</code>关键字来判断该类有没有<code>RandomAccess</code>标记：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 假设 list 数据量非常大,推荐写法
+</span></span><span class="line"><span class="cl">List&lt;Object&gt; list = ...;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">if(list instanceof RandomAccess){
+</span></span><span class="line"><span class="cl">    // 随机访问
+</span></span><span class="line"><span class="cl">    for (int i = 0;i&lt; list.size();i++) {
+</span></span><span class="line"><span class="cl">        System.out.println(list.get(i));
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}else {
+</span></span><span class="line"><span class="cl">    // 顺序访问
+</span></span><span class="line"><span class="cl">    for(Object obj: list) {
+</span></span><span class="line"><span class="cl">        System.out.println(obj);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在<code>List</code>中<code>ArrayList</code>被<code>RandomAccess</code>接口标记，而<code>LinkedList</code>没有被<code>RandomAccess</code>接口标记，所以<code>ArrayList</code>适合随机访问，而<code>LinkedList</code>适合顺序访问。</p>
+<h3 id="cloneable">Cloneable</h3>
+<p><code>Cloneable</code>接口是Java开发中常用的一个接口，它是一个标记接口。
+如果一个想要拷贝一个对象，就需要重写<code>Object</code>中的<code>clone</code>方法并让其实现<code>Cloneable</code>接口。如果只重写<code>clone</code>方法，不实现<code>Cloneable</code>接口就会报<code>CloneNotSupportedException</code>异常。</p>
+<p><code>clone</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>应当注意的是，<code>clone()</code>方法并不是<code>Cloneable</code>接口的方法，而是<code>Object</code>的一个<code>protected</code>方法。
+<code>Cloneable</code>接口只是规定，如果一个类没有实现<code>Cloneable</code>接口又调用了<code>clone</code>方法，就会抛出<code>CloneNotSupportedException</code>。
+换言之，<code>clone</code>方法规定了想要拷贝对象，就需要实现<code>Cloneable</code>方法，<code>clone</code>方法让<code>Cloneable</code>接口变得有意义。</p>
+<p>拷贝分为浅拷贝与深拷贝：</p>
+<ul>
+<li>浅拷贝：被复制对象的所有值属性都含有与原来对象的相同，而所有的对象引用属性仍然指向原来的对象；</li>
+<li>深拷贝：在浅拷贝的基础上，所有引用其他对象的变量也进行了<code>clone</code>，并指向被复制过的新对象；</li>
+</ul>
+<p>如果一个被复制的属性都是基本类型，那么只需要实现当前类的<code>Cloneable</code>机制就可以了，此为浅拷贝。
+如果被复制对象的属性包含其他实体类对象引用，那么这些实体类对象都需要实现<code>Cloneable</code>接口并覆盖<code>clone</code>方法。
+<code>ArrayList</code>中<code>clone</code>方法可以创建一个浅拷贝。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// ArrayList类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayList</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">transient</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elementData</span><span class="p">;</span><span class="w">     
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Returns a shallow copy of this &lt;tt&gt;ArrayList&lt;/tt&gt; instance.  (The
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * elements themselves are not copied.)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return a clone of this &lt;tt&gt;ArrayList&lt;/tt&gt; instance
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 调用Object类的clone方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ArrayList</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">ArrayList</span><span class="o">&lt;?&gt;</span><span class="p">)</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 将集合中的元素进行拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="p">.</span><span class="na">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">v</span><span class="p">.</span><span class="na">modCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">v</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// this shouldn&#39;t happen, since we are Cloneable</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InternalError</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// Arrays类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Arrays</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="nf">copyOf</span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newLength</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">copyOf</span><span class="p">(</span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="n">newLength</span><span class="p">,</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">getClass</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="p">,</span><span class="n">U</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="nf">copyOf</span><span class="p">(</span><span class="n">U</span><span class="o">[]</span><span class="w"> </span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newLength</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">T</span><span class="o">[]&gt;</span><span class="w"> </span><span class="n">newType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">T</span><span class="o">[]</span><span class="w"> </span><span class="n">copy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">((</span><span class="n">Object</span><span class="p">)</span><span class="n">newType</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p">(</span><span class="n">Object</span><span class="p">)</span><span class="n">Object</span><span class="o">[]</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">?</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="o">[</span><span class="n">newLength</span><span class="o">]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="o">[]</span><span class="p">)</span><span class="w"> </span><span class="n">Array</span><span class="p">.</span><span class="na">newInstance</span><span class="p">(</span><span class="n">newType</span><span class="p">.</span><span class="na">getComponentType</span><span class="p">(),</span><span class="w"> </span><span class="n">newLength</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">original</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">copy</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">original</span><span class="p">.</span><span class="na">length</span><span class="p">,</span><span class="w"> </span><span class="n">newLength</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">copy</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>ArrayList</code>中核心方法最终调用<code>Arrays.copyOf</code>方法，其中调用<code>Arrays.newInstance</code>方法或者创建一个新数组，<code>Arrays.newInstance</code>方法作用，是创建具有指定组件类型和长度的新数组。
+所以不论怎样都会创建一个<code>Object</code>数组。最后使用<code>System.arraycopy</code>方法将之前的旧数组中的元素拷贝到新创建的数组中，然后赋值给<code>ArrayList.elementData</code>对象并返回。</p>
+<p>如果需要深拷贝，即复制对象及其引用的所有对象，需要手动实现拷贝逻辑，通常涉及遍历列表并复制每个元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Item</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Item</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayListCopy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建并初始化一个ArrayList</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Item</span><span class="o">&gt;</span><span class="w"> </span><span class="n">originalList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Item</span><span class="p">(</span><span class="s">&#34;C&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 深拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Item</span><span class="o">&gt;</span><span class="w"> </span><span class="n">deepCopy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Item</span><span class="w"> </span><span class="n">item</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">originalList</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">deepCopy</span><span class="p">.</span><span class="na">add</span><span class="p">((</span><span class="n">Item</span><span class="p">)</span><span class="w"> </span><span class="n">item</span><span class="p">.</span><span class="na">clone</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 修改原始列表的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originalList</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">).</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Z&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Original List: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">originalList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Deep Copy: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">deepCopy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="arraylist扩容">ArrayList扩容</h3>
+<p>因为<code>ArrayList</code>底层使用数组保存数据的，而数组一旦被创建就不能改变大小，但是<code>ArrayList</code>的长度是可以改变的，所以可以通过<code>ArrayList</code>类中的<code>add</code>方法找到数组扩容方法。
+<code>add</code>方法调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">add 
+</span></span><span class="line"><span class="cl">    -&gt; ensureCapacityInternal()
+</span></span><span class="line"><span class="cl">    -&gt; calculateCapacity()
+</span></span><span class="line"><span class="cl">    -&gt; ensureExplicitCapacity()
+</span></span><span class="line"><span class="cl">    -&gt; grow()
+</span></span></code></pre></div><p>通过<code>add</code>方法，最终找到了<code>grow</code>方法，也就是扩容的核心方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">grow</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">minCapacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// overflow-conscious code</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elementData</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">minCapacity</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">minCapacity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">MAX_ARRAY_SIZE</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hugeCapacity</span><span class="p">(</span><span class="n">minCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// minCapacity is usually close to size, so this is a win:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">elementData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>ArrayList</code>如果没有指定容量创建数组，默认会创建一个长度为10的数组用来保存元素，之后通过<code>grow</code>方法中的这段代码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p><code>&gt;&gt;</code>右移几位就是相当于除以2的几次幂，所以每次扩容都是原容量的1.5倍。最后通过<code>Arrays.copyOf</code>方法将之前的数组中元素，全部移到新创建的数组上。</p>
+<p>由于频繁的扩容数组会对性能产生影响，如果在<code>ArrayList</code>中要存储很大的数据，需要在<code>ArrayList</code>的有参构造中指定数组的长度，来减少扩容的次数。
+需要注意的是创建指定长度的<code>ArrayList</code>，在没有<code>add</code>之前<code>ArrayList</code>中的数组已经初始化了，但是<code>List</code>的大小没变，因为<code>List</code>的大小是由<code>size</code>决定的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="p">(</span><span class="n">1000000</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><h3 id="arraylist与linkedlist">ArrayList与LinkedList</h3>
+<p><code>ArrayList</code>与<code>LinkedList</code>性能比较是一道经典的面试题，先说答案<code>ArrayList</code>查找快，增删慢，而<code>LinkedList</code>增删快，查找慢。
+造成这种原因是因为底层的数据结构不一样。<code>ArrayList</code>底层是数组，而数组的中的元素内存分配都是连续的，并且数组中的元素只能存放一种，这就造成了数组中的元素地址是有规律的，数组中查找元素快速的原因正是利用了这一特点。
+查询方式为: 首地址＋(元素类型长度*下标)。例如：<code>new int arr[5]; arr</code>数组的地址假设为<code>0x1000</code>，那么<code>arr[3]</code>地址可看作为 <code>0x1000 + (3 * 4)</code>，3为数组下标，4为int元素类型长度。</p>
+<p>而<code>LinkedList</code>在Java中的底层结构是对象，每一个对象结点中都保存了下一个结点的位置形成的链表结构，由于<code>LinkedList</code>元素的地址是不连续的，所以没办法按照数组那样去查找，所以就比较慢。</p>
+<p>由于数组一旦分配了大小就不能改变，所以<code>ArrayList</code>在进行添加操作时会创建新的数组，如果要添加到<code>ArrayList</code>中的指定的位置，是通过<code>System.arraycopy</code>方法将数组进行复制，新的数组会将待插入的指定位置空余出来，最后在将元素添加到集合中。
+在进行删除操作时是通过<code>System.arraycopy</code>方法，将待删除元素后面剩余元素复制到待删除元素的位置。当<code>ArrayList</code>里有大量数据时，这时候去频繁插入或删除元素会触发底层数组频繁拷贝，所以效率不高，还会造成内存空间的浪费。</p>
+<p><code>LinkedList</code>在进行添加，删除操作时，会用二分查找法找到将要添加或删除的元素，之后再设置对象的下一个结点来进行添加或删除操作，所以增加删除的效率高。</p>
+<blockquote>
+<p>二分查找法：也称为折半查找法，是一种适用于大量数据查找的方法，但是要求数据必须的排好序的，每次以中间的值进行比较，根据比较的结果可以直接舍去一半的值，直至全部找完（可能会找不到）或者找到数据为止。
+此处LinkedList会比较查找的元素是距离头结点比较近，还是尾结点比较近，距离哪边较近则从哪边开始查找。</p>
+</blockquote>
+<p><code>ArrayList</code>获取元素效率非常的高，时间复杂度是<code>O(1)</code>，而查找、插入和删除元素效率似乎不太高，时间复杂度为<code>O(n)</code>。
+<code>LinkedList</code>与<code>ArrayList</code>相反，获取第几个元素依次遍历复杂度<code>O(n)</code>，添加到末尾复杂度<code>O(1)</code>，添加到指定位置复杂度<code>O(n)</code>，删除元素直接指针指向操作复杂度<code>O(1)</code>。</p>
+<p>注意，<code>ArrayList</code>的增删不一定比<code>LinkedList</code>效率低，但是<code>ArrayList</code>查找效率一定比<code>LinkedList</code>高。
+如果在靠近末尾的地方插入，那么<code>ArrayList</code>只需要移动较少的数据，而<code>LinkedList</code>则需要一直查找到列表尾部，反而耗费较多时间，这时<code>ArrayList</code>就比<code>LinkedList</code>要快。</p>
+<p>所以在实际开发中，<code>ArrayList</code>适用于需要快速随机访问和较少插入删除操作的场景，而<code>LinkedList</code>适用于频繁插入删除操作和需要实现队列或双端队列的场景。</p>
+<h3 id="线程安全">线程安全</h3>
+<p>众所周知，<code>ArrayList</code>是线程不安全的，因为它不保证在多线程环境下的同步操作，当多个线程同时访问和修改同一个<code>ArrayList</code>对象时可能会导致数据不一致或抛出异常。
+多线程下抛出<code>ConcurrentModificationException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果没有报错，需要多试几次</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrayList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">arrayList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">arrayList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>出现该异常的原因是集合中的<code>fail-fast</code>机制。在查看源码的时候，发现调用<code>remove</code>方法时，会执行<code>checkForComodification</code>方法。
+若<code>modCount</code>不等于<code>expectedModCount</code>，则抛出<code>ConcurrentModificationException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkForComodification</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那为什么会抛出<code>ConcurrentModificationException</code>异常呢？
+在调用<code>add</code>方法时，会修改<code>modCount++</code>。一个线程调用<code>add</code>方法，一个线程调用<code>next</code>遍历方法，都共同读取<code>modCount</code>变量的值。
+因为是多线程操作，<code>expectedModCount</code>、<code>modCount</code>变量为公共的，所以很容易出现<code>modCount != expectedModCount</code>，所以便抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 添加元素到指定的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">element</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IndexOutOfBoundsException</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;Index: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Size: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 修改modCount</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ensureCapacity</span><span class="p">(</span><span class="n">size</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">  </span><span class="c1">// Increments modCount!!</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">element</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">size</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>因此，在多线程环境中使用<code>ArrayList</code>时，需要手动同步操作，或者使用线程安全的集合类。保证<code>ArrayList</code>线程安全有以下几种方法：</p>
+<ol>
+<li>可以使用 <code>Vector</code> 来代替 <code>ArrayList</code>。<code>Vector</code>是线程安全的<code>ArrayList</code>，但是由于底层是加了<code>synchronized</code>，性能略差不推荐使用；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List list = new Vector();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+<li>使用<code>Collections.synchronizedArrayList()</code> 来创建 <code>ArrayList</code>。使用<code>Collections</code>工具类来创建<code>ArrayList</code>的思路是，在<code>ArrayList</code>的外边套了一个<code>synchronized</code>外壳，来保证<code>ArrayList</code>线程安全；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">List list = Collections.synchronizedArrayList();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+<li>使用<code>CopyOnWriteArrayList()</code>来保证 <code>ArrayList</code> 线程安全。<code>CopyWriteArrayList</code>字面意思就是在写的时候复制，主要思想就是读写分离的思想。
+<code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>，所以保证了某个线程在写的时候不会被打断；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">CopyOnWriteArrayList&lt;String&gt; list = new CopyOnWriteArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">list.add(UUID.randomUUID().toString());
+</span></span></code></pre></div></li>
+</ol>
+<p>其中比较推荐的解决方案是使用<code>CopyOnWriteArrayList</code>。
+<code>CopyWriteArrayList</code>字面意思就是在写的时候复制，思想就是读写分离的思想。它的基本原理是每次修改操作都会创建该列表的一个新副本，因此读操作不需要加锁，可以并发执行。
+以下是<code>CopyOnWriteArrayList</code>的<code>add()</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The array, accessed only via getArray/setArray. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The lock protecting all mutators */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Gets the array.  Non-private so as to also be accessible
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * from CopyOnWriteArraySet class.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="nf">getArray</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Appends the specified element to the end of this list.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param e element to be appended to this list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@code true}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">lock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elements</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">newElements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elements</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newElements</span><span class="o">[</span><span class="n">len</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setArray</span><span class="p">(</span><span class="n">newElements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>保证了某个线程在写的时候不会被打断。
+可以看到源码开始先是复制了一份数组，同一时刻只有一个线程写，其余的线程会读。在复制的数组上边进行写操作，写好以后在返回<code>true</code>。
+这样就把读写进行了分离，写好以后因为<code>array</code>加了<code>volatile</code>修饰，所以该数组是对于其他的线程是可见的，就会读取到最新的值。
+由于每次写操作都会创建一个数组的新副本，所以写操作的开销较大。但是读取操作非常高效且不需要加锁，因此适用于读操作远多于写操作的场景，例如缓存、白名单等。</p>
+<h3 id="arraylist安全删除">ArrayList安全删除</h3>
+<p>在<code>ArrayList</code>中删除元素时，&ldquo;安全删除&rdquo; 指的是在删除元素过程中避免出现异常或错误，并确保集合的结构和元素的状态保持一致。
+在使用增强型<code>for-each</code>循环遍历<code>ArrayList</code>时，如果尝试删除元素，会抛出<code>ConcurrentModificationException</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArrayListError</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;C&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;D&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">element</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">element</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">list</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">element</span><span class="p">);</span><span class="w"> </span><span class="c1">// 这会抛出 ConcurrentModificationException</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在前面讲过<code>add</code>方法，会操作<code>modCount</code>变量的值，在查看源码的时候，发现调用<code>remove</code>方法时，也会操作<code>modCount</code>变量的值。
+当调用<code>remove</code>方法时执行了<code>modCount++</code>，此时<code>modCount</code>变成了<code>N+1</code>。然后接着再循环中遍历调用<code>next</code>方法，调用<code>checkForComodification</code>比较<code>expectedModCount</code>和<code>modCount</code>的大小，此时<code>modCount != expectedModCount</code>，便抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">checkForComodification</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">modCount</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedModCount</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentModificationException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="c1">// 删除指定位置的元素 </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RangeCheck</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 修改modCount</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">modCount</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">E</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">E</span><span class="p">)</span><span class="w"> </span><span class="n">elementData</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">numMoved</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">numMoved</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">arraycopy</span><span class="p">(</span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="o">+</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">elementData</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">numMoved</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">elementData</span><span class="o">[--</span><span class="n">size</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="c1">// Let gc do its work</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">oldValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>安全删除的关键在于，确保在遍历和删除操作中不会同时对集合的结构造成不一致性，从而导致程序运行时出现异常或者结果不符合预期。</p>
+<p>最经典的解决方案是使用<code>Iterator</code>遍历集合，在遍历过程中删除元素。在使用迭代器遍历<code>ArrayList</code>时，迭代器会维护一个<code>expectedModCount</code>，它记录了迭代开始时的<code>modCount</code>。
+每次调用迭代器的<code>next</code>方法时，都会检查当前的<code>modCount</code>是否与<code>expectedModCount</code>相等，如果不相等就抛出<code>ConcurrentModificationException</code>异常。使用迭代器的<code>remove()</code>方法能够确保在删除元素时，同步更新，从而避免异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ArrayList&lt;String&gt; list = new ArrayList&lt;&gt;();
+</span></span><span class="line"><span class="cl">// 添加元素到列表中
+</span></span><span class="line"><span class="cl">Iterator&lt;String&gt; iterator = list.iterator();
+</span></span><span class="line"><span class="cl">while (iterator.hasNext()) {
+</span></span><span class="line"><span class="cl">    String element = iterator.next();
+</span></span><span class="line"><span class="cl">    if (/* 满足删除条件 */) {
+</span></span><span class="line"><span class="cl">        iterator.remove(); // 使用迭代器的 remove 方法安全删除元素
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><h2 id="hashset">HashSet</h2>
+<p><code>HashSet</code>是基于<code>HashMap</code>来实现的，支持快速查找，但不支持有序性操作。实现了<code>Set</code>接口，同时还实现了序列化和可克隆化。
+<code>Set</code>不允许存储重复的元素，即集合中的元素是唯一的。当试图添加一个已经存在的元素时，<code>add</code>方法会返回<code>false</code>，并且集合不会发生改变。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HashSetExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 HashSet 实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Orange&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 打印 HashSet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;HashSet: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">set</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 尝试添加重复元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">added</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Added duplicate element: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">added</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出: false</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After removing &#39;Banana&#39;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">set</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="去重原理">去重原理</h3>
+<p><code>HashSet</code>内部实际上是由一个<code>HashMap</code>实例支持的，其中<code>HashMap</code>的键值对中的键存储了<code>HashSet</code>中的元素，而值则是一个占位对象，用来表示键已经存在。</p>
+<p>当调用<code>HashSet</code>的<code>add(E e)</code>方法添加元素时，首先会调用元素<code>e</code>的 <code>hashCode</code>方法获取其哈希码。<code>HashSet</code>根据哈希码确定元素在内部<code>HashMap</code>的存储位置。
+如果该位置上已经存在一个元素，则使用 <code>equals</code> 方法比较新元素<code>e</code>与已存在的元素是否相等。
+如果<code>equals</code>方法返回<code>true</code>，则认为新元素与已存在元素相同，不进行添加操作，返回<code>false</code>。
+如果<code>equals</code>方法返回<code>false</code>，则说明哈希码冲突，但实际上是不同的对象，此时将新元素添加到 <code>HashSet</code>中，返回<code>true</code>。
+如果该位置上不存在任何元素，则直接将新元素添加到<code>HashSet</code>中，并返回<code>true</code>。</p>
+<p>简单来说，<code>HashSet</code>利用对象的哈希码和<code>equals</code>方法来确保集合中不存储重复的元素。
+当添加新元素时，先计算其哈希码确定存储位置，如果位置上已存在相同哈希码且通过<code>equals</code>方法比较相等的元素，则不添加，否则添加新元素到集合中。</p>
+<p><code>HashSet</code>添加方法的实现源码如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// hashmap 中 put() 返回 null 时，表示操作成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">e</span><span class="p">,</span><span class="w"> </span><span class="n">PRESENT</span><span class="p">)</span><span class="o">==</span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 返回值：如果插入位置没有元素则返回 null，否则返回上一个元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">put</span><span class="p">(</span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">return</span><span class="w"> </span><span class="n">putVal</span><span class="p">(</span><span class="n">hash</span><span class="p">(</span><span class="n">key</span><span class="p">),</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">false</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">final</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">putVal</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">onlyIfAbsent</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="kt">boolean</span><span class="w"> </span><span class="n">evict</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="c1">//如果哈希表为空，调用 resize() 创建一个哈希表，并用变量 n 记录哈希表长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">tab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">tab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">resize</span><span class="p">()).</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">    * 如果指定参数 hash 在表中没有对应的桶，即为没有碰撞
+</span></span></span><span class="line"><span class="cl"><span class="cm">    * Hash函数，(n - 1) &amp; hash 计算 key 将被放置的槽位
+</span></span></span><span class="line"><span class="cl"><span class="cm">    * (n - 1) &amp; hash 本质上是 hash % n 位运算更快
+</span></span></span><span class="line"><span class="cl"><span class="cm">    */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 直接将键值对插入到 map 中即可</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="c1">// 桶中已经存在元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">K</span><span class="w"> </span><span class="n">k</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 比较桶中第一个元素(数组中的结点)的 hash 值相等，key 相等</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">p</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">hash</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="p">((</span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">.</span><span class="na">key</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">key</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">key</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">k</span><span class="p">))))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 将第一个元素赋值给 e，用 e 来记录</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 当前桶中无该键值对，且桶是红黑树结构，按照红黑树结构插入</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">p</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">((</span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="w"> </span><span class="n">p</span><span class="p">).</span><span class="na">putTreeVal</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 当前桶中无该键值对，且桶是链表结构，按照链表结构插入到尾部</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">binCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">binCount</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 遍历到链表尾部</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">.</span><span class="na">next</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="n">p</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="c1">// 检查链表长度是否达到阈值，达到将该槽位节点组织形式转为红黑树</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">binCount</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">TREEIFY_THRESHOLD</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="c1">// -1 for 1st</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                  </span><span class="n">treeifyBin</span><span class="p">(</span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="n">hash</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 链表节点的&lt;key, value&gt;与 put 操作&lt;key, value&gt;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 相同时，不做重复操作，跳出循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">hash</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">((</span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">key</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">key</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">key</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">k</span><span class="p">))))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 找到或新建一个 key 和 hashCode 与插入元素相等的键值对，进行 put 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// existing mapping for key</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 记录 e 的 value</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">V</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">          * onlyIfAbsent 为 false 或旧值为 null 时，允许替换旧值
+</span></span></span><span class="line"><span class="cl"><span class="cm">          * 否则无需替换
+</span></span></span><span class="line"><span class="cl"><span class="cm">          */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">onlyIfAbsent</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 访问后回调</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">afterNodeAccess</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 返回旧值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">return</span><span class="w"> </span><span class="n">oldValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="c1">// 更新结构化修改信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="o">++</span><span class="n">modCount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="c1">// 键值对数目超过阈值时，进行 rehash</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="c1">// 插入后回调</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="n">afterNodeInsertion</span><span class="p">(</span><span class="n">evict</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>从上述源码可以看出，当将一个键值对放入<code>HashMap</code>时，首先根据<code>key</code>的<code>hashCode()</code>返回值决定该<code>Entry</code>的存储位置。如果有两个<code>key</code>的<code>hash</code>值相同，则会判断这两个元素<code>key</code>的<code>equals()</code>是否相同，如果相同就返回<code>true</code>，说明是重复键值对，那么<code>HashSet</code>中<code>add</code>方法的返回值会是<code>false</code>，表示<code>HashSet</code>添加元素失败。
+因此，如果向<code>HashSet</code>中添加一个已经存在的元素，新添加的集合元素不会覆盖已有元素，从而保证了元素的不重复。如果不是重复元素，<code>put</code>方法最终会返回<code>null</code>，传递到<code>HashSet</code>的<code>add</code>方法就是添加成功。</p>
+<h3 id="equals与hashcode">equals与hashCode</h3>
+<p>因为<code>HashSet</code>底层用到了<code>equals</code>和<code>hashCode</code>方法，如果对象中的<code>equals</code>和<code>hashCode</code>方法没有正确地重写，可能会导致<code>HashSet</code>在判断元素相等性时出现问题，从而允许添加相同的元素。</p>
+<p><code>equals()</code>地址比较是通过对象的哈希值来比较的。<code>hash</code>值是由<code>hashCode</code>方法产生的，<code>hashCode</code>属于<code>Object</code>类的本地方法，默认使用<code>==</code>比较两个对象，如果<code>equals()</code>相等<code>，hashcode</code>一定相等，如果<code>hashcode</code>相等，<code>equals</code>不一定相等。
+所以在覆盖<code>equals</code>方法时应当总是覆盖<code>hashCode</code>方法，保证等价的两个对象散列值也相等。</p>
+<p>下面的代码中，新建了两个等价的对象，并将它们添加到<code>HashSet</code>中。我们希望将这两个对象当成一样的，只在集合中添加一个对象，但是因为<code>EqualExample</code>没有实现<code>hashCode</code>方法，因此这两个对象的散列值是不同的，最终导致集合添加了两个等价的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">e1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EqualExample</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">e2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EqualExample</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e1</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">e2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">EqualExample</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">e1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">e2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">set</span><span class="p">.</span><span class="na">size</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>所以在覆盖<code>equals</code>方法时应当总是覆盖<code>hashCode</code>方法，保证等价的两个对象散列值也相等。</p>
+<h3 id="线程安全-1">线程安全</h3>
+<p><code>HashSet</code>和<code>ArrayList</code>类似，也是线程不安全的集合类，也会出现<code>ConcurrentModificationException</code>异常。代码演示线程不安全示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">set</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>HashSet</code>线程不安全的解决方案通常是使用<code>CopyOnWriteArraySet</code>。这种集合在读操作远多于写操作的场景中非常有用，因为它通过每次修改创建集合的副本来实现线程安全。
+<code>CopyOnWriteArraySet</code>是Java中一种线程安全的<code>Set</code>实现，内部使用了<code>CopyOnWriteArrayList</code>来存储元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">al</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an empty set.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">CopyOnWriteArraySet</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">al</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>因为底层用<code>CopyOnWriteArrayList</code>存储，所以写操作开销大，每次修改都会创建数组副本，适用场景有限。不适用于写操作频繁的场景，否则会导致高昂的内存和时间开销。
+与<code>CopyOnWriteArrayList</code>不同的是，<code>CopyOnWriteArraySet</code>不允许包含重复元素。如果尝试添加一个已经存在的元素，集合将保持不变，所以该集合在线程不安全的情况下可替代<code>HashSet</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CopyOnWriteArraySetExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 创建一个 CopyOnWriteArraySet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">cowSet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArraySet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w"> </span><span class="c1">// 不允许重复元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Set: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fruit</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">cowSet</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">fruit</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 添加新元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Grapes&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After adding Grapes: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">cowSet</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After removing Banana: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="queue">Queue</h2>
+<p>在Java中，队列是一种常用的数据结构，用于按顺序存储元素，通常以先进先出(<code>FIFO</code>：<code>First In First Out</code>)的方式进行操作。
+它和<code>List</code>的区别在于，<code>List</code>可以在任意位置添加和删除元素，而队列只有两个操作，把元素添加到队列末尾，或者从队列头部取出元素。</p>
+<p>常见实现：</p>
+<ul>
+<li><code>LinkedList</code>：<code>LinkedList</code>类实现了<code>Queue</code>接口，同时也实现了<code>Deque</code>接口（双端队列）。它可以作为队列、双端队列或堆栈使用；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Queue&lt;String&gt; queue = new LinkedList&lt;&gt;();
+</span></span><span class="line"><span class="cl">queue.offer(&#34;A&#34;);
+</span></span><span class="line"><span class="cl">queue.offer(&#34;B&#34;);
+</span></span><span class="line"><span class="cl">queue.poll(); // 返回 &#34;A&#34; 并移除
+</span></span></code></pre></div></li>
+<li><code>PriorityQueue</code>：<code>PriorityQueue</code>是一个基于优先级堆实现的队列，元素根据其自然顺序进行排序；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">PriorityQueue&lt;Integer&gt; pq = new PriorityQueue&lt;&gt;();
+</span></span><span class="line"><span class="cl">pq.offer(2);
+</span></span><span class="line"><span class="cl">pq.offer(1);
+</span></span><span class="line"><span class="cl">pq.offer(3);
+</span></span><span class="line"><span class="cl">pq.poll(); // 返回 1 并移除
+</span></span></code></pre></div></li>
+<li><code>ArrayDeque</code>：<code>ArrayDeque</code>类实现了<code>Deque</code>接口，是一个可调整大小的数组实现的双端队列，通常比<code>LinkedList</code>更快；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Deque&lt;String&gt; deque = new ArrayDeque&lt;&gt;();
+</span></span><span class="line"><span class="cl">deque.offer(&#34;A&#34;);
+</span></span><span class="line"><span class="cl">deque.offerFirst(&#34;B&#34;);
+</span></span><span class="line"><span class="cl">deque.pollLast(); // 返回 &#34;A&#34; 并移除
+</span></span></code></pre></div></li>
+</ul>
+<p>队列的实现通常不允许插入<code>null</code>元素，尽管一些实现，如<code>LinkedList</code>，不禁止插入<code>null</code>元素。
+即使在允许的实现中，<code>null</code>也不应插入队列中，因为<code>poll</code>方法也使用<code>null</code>作为特殊返回值，用来表示队列不包含任何元素。这会导致难以区分队列中的<code>null</code>元素和队列为空的情况。</p>
+<p><code>poll()</code>和<code>peek()</code>方法：</p>
+<ul>
+<li><code>poll()</code>: 检索并删除此队列的头部，如果此队列为空，则返回<code>null</code>；</li>
+<li><code>peek()</code>: 检索但不删除此队列的头部，如果此队列为空，则返回<code>null</code>；</li>
+</ul>
+<h2 id="hashmap">HashMap</h2>
+<p><code>HashMap</code>是一个散列表，它存储的内容是键值对(<code>key-value</code>)映射。
+<code>HashMap</code>实现了<code>Map</code>接口，根据键的<code>HashCode</code>值存储数据，具有很快的访问速度，最多允许一条记录的键为<code>null</code>，不支持线程同步。<code>HashMap</code>是无序的，即不会记录插入的顺序。</p>
+<p>相关操作：</p>
+<ul>
+<li>存储：通过<code>key</code>的<code>hashcode</code>方法找到在<code>hashMap</code>存储的位置，如果该位置有元素则通过<code>equals</code>方法进行比较，如果<code>equals</code>返回值为<code>true</code>，则覆盖<code>value</code>；
+如果<code>equals</code>返回值为<code>false</code>则在该数组元素的头部追加该元素，形成一个链表结构；</li>
+<li>读取：通过<code>key</code>的<code>hashcode</code>方法获取元素存在该数组的位置，然后通过<code>equals</code>拿到该值；</li>
+</ul>
+<p>总的来说<code>hashMap</code>底层将<code>key-value</code>当成一个整体来处，<code>hashMap</code>底层采用一个<code>Entry</code>数组保存所有的键值对。
+当存储一个<code>entry</code>对象时，会根据<code>key</code>的<code>hashCode</code>来决定存放在数组中的位置，再根据<code>equals</code>方法来确定在链表中的位置，读取一个<code>entry</code>对象。
+<code>equals</code>和<code>hashCode</code>在<code>hashMap</code>中就像一个坐标一样，来定位<code>hashMap</code>中的值。</p>
+<h3 id="hashmap结构">HashMap结构</h3>
+<p><img alt="HashMap结构" src="/iblog/posts/annex/images/essays/HashMap%E7%BB%93%E6%9E%84.png"></p>
+<p>在JDK1.7及之前结构为<code>数组+单向链表</code>，JDK1.8及之后结构为<code>数组 + 单向链表/红黑树</code>。
+在JDK1.8时，如果存储<code>Map</code>中数组元素对应的索引的每个链表超过8，就将单向链表转化为红黑树，当红黑树的节点少于6个的时候又开始使用链表。</p>
+<p>那么为什么要使用红黑树？
+当有发生大量的<code>hash</code>冲突时，因为链表遍历效率很慢，为了提升查询的效率，所以使用了红黑树的数据结构。</p>
+<p>为什么不一开始就用红黑树代替链表结构？</p>
+<blockquote>
+<p>Because TreeNodes are about twice the size of regular nodes, we use them only when bins contain enough nodes to warrant use  (see TREEIFY_THRESHOLD).
+And when they become too small (due to removal or resizing) they are converted back to plain bins.</p>
+</blockquote>
+<p>这是JDK文档注释，大意为：单个<code>TreeNode</code>需要占用的空间大约是普通<code>Node</code>的两倍，所以只有当包含足够多的<code>Nodes</code>时才会转成<code>TreeNodes</code>，而是否足够多就是由<code>TREEIFY_THRESHOLD</code>的值(默认值8)决定的。
+而当桶中节点数由于移除或者<code>resize</code>变少后，又会变回普通的链表的形式，以便节省空间，这个阈值是<code>UNTREEIFY_THRESHOLD</code>(默认值6)。</p>
+<p>为什么树化阈值要设置为8？
+如果<code>hashCode</code>分布良好，也就是<code>hash</code>计算的结果离散好的话，那么红黑树这种形式是很少会被用到的，因为各个值都均匀分布，很少出现链表很长的情况。
+在理想情况下，链表长度符合泊松分布，各个长度的命中概率依次递减，当长度为8的时候，概率仅为0.00000006。
+这是一个小于千万分之一的概率，通常我们的<code>Map</code>里面是不会存储这么多的数据的，所以通常情况下，并不会发生从链表向红黑树的转换。</p>
+<p><code>HashMap</code>是通过<code>hash</code>算法来判断对象应该放在哪个桶里面的。JDK并不能阻止我们用户实现自己的哈希算法，如果我们故意把哈希算法变得不均匀，那么每次存放对象很容易造成<code>hash</code>冲突。
+链表长度超过8就转为红黑树的设计，更多的是为了防止用户自己实现了不好的哈希算法时导致链表过长，从而导致查询效率低，而此时转为红黑树更多的是一种保底策略，用来保证极端情况下查询的效率。
+红黑树的引入保证了在大量<code>hash</code>冲突的情况下，<code>HashMap</code>还具有良好的查询性能。</p>
+<p>那么在JDK1.8引入红黑树后，如果单链表节点个数超过8个是否一定会树化？
+这是不一定的，在进行树化之前会进行判断<code>(n = tab.length) &lt; MIN_TREEIFY_CAPACITY)</code>是否需要扩容，如果表中数组元素小于这个阈值（默认是64），就会进行扩容。
+因为扩容不仅能增加表中的容量，还能缩短单链表的节点数，从而更长远的解决链表遍历慢问题。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Replaces all linked nodes in bin at index for given hash unless
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * table is too small, in which case resizes instead.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">treeifyBin</span><span class="p">(</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">;</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tab</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MIN_TREEIFY_CAPACITY</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">tl</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">replacementTreeNode</span><span class="p">(</span><span class="n">e</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tl</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">hd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">p</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tl</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">tl</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">p</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">tab</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hd</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">hd</span><span class="p">.</span><span class="na">treeify</span><span class="p">(</span><span class="n">tab</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hash冲突">Hash冲突</h3>
+<p>在<code>HashMap</code>中，哈希冲突，也叫<code>Hash</code>碰撞，是指两个不同的键通过同一散列函数计算得到的哈希值相同，从而映射到同一个桶中。
+当插入<code>HashMap</code>中元素的<code>key</code>出现重复时，这个时候就发生了<code>Hash</code>冲突了。哈希冲突是哈希表必须处理的问题。</p>
+<p>链地址法是处理哈希冲突的常见方法之一，它在每个桶中使用一个链表来存储所有映射到该桶的键值对。具体插入步骤：</p>
+<ol>
+<li>计算键的哈希值并确定其在数组中的位置；</li>
+<li>如果桶为空，直接将键值对存储在该桶中；</li>
+<li>如果桶不为空，则遍历桶中的链表，检查是否存在相同的键；
+<ul>
+<li>如果存在相同的键，更新对应的值；</li>
+<li>如果不存在相同的键，将新的键值对添加到链表的末尾；</li>
+</ul>
+</li>
+</ol>
+<p>在Java8及更高版本中，为了提高性能，当单个桶中的链表长度超过一定阈值（默认是 8）时，会将链表转换为红黑树。
+这种方法在大量冲突的情况下提供了更高效的查找和插入性能。具体插入步骤：</p>
+<ol>
+<li>计算键的哈希值确定存储位置；</li>
+<li>如果存储位置为空，则直接插入新键值对；</li>
+<li>如果存储位置已有节点，当链表长度超过阈值（默认为 8），将链表转换为红黑树，否则继续用链表存储；</li>
+<li>如果当前结点为红黑树结点，则根据节点的哈希值和键值比较，找到合适的插入位置；插入后，根据红黑树的性质进行调整，保持平衡；</li>
+<li>当桶中元素数量减少到一定阈值以下时（默认是 6），会将红黑树转换回链表，以减少内存开销；</li>
+</ol>
+<h3 id="hashmap容量">HashMap容量</h3>
+<p><code>HashMap</code>在创建时需要指定初始容量，如果不指定默认是16。初始容量指的是<code>HashMap</code>中桶的数量，即存储键值对的数组大小。
+如果能预估要存储的键值对数量，可以在创建<code>HashMap</code>时指定初始容量，以避免频繁的扩容操作。</p>
+<p>如果指定容量大小为10，那么实际大小是多少？
+先说答案，实际大小是16，其容量为不小于指定容量的2的N次方。</p>
+<p>为什么容量始终是2的N次方？
+为了减少<code>Hash</code>碰撞，尽量使<code>Hash</code>算法的结果均匀分布。</p>
+<p>当使用<code>put</code>方法时，到底存入<code>HashMap</code>的哪个数组中？
+这是通过<code>hash</code>算法决定的，如果某一个数组中的链表过长旧会影响查询的效率。为了避免出现<code>hash</code>碰撞，让<code>hash</code>尽可能的散列分布，就需要在<code>hash</code>算法上做文章。</p>
+<p>JDK1.7通过逻辑与运算，判断这个元素该进入哪个数组。在下面的代码中<code>length</code>的长度始终为不小于指定容量的2的N次方。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">indexFor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">h</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为了更好的理解这个方法，举个例子，假设<code>h=2</code>或<code>h=3</code>，<code>length=15</code>，执行<code>indexFor</code>方法，最终逻辑与运算后的结果是一致的，因为最终结果是一致的所以就导致了<code>hash</code>碰撞。
+这种问题多了以后会造成容器中的元素分布不均匀，都分配在同一个数组上，在查询的时候就减慢了查询的效率，另一方面也造成空间的浪费。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">-- 2转换为2进制与15-1进行&amp;运算
+</span></span><span class="line"><span class="cl">  0000 0010
+</span></span><span class="line"><span class="cl">&amp; 0000 1110 
+</span></span><span class="line"><span class="cl">———————————— 
+</span></span><span class="line"><span class="cl">  0000 1110
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">-- 3转换为2进制与15-1进行&amp;运算
+</span></span><span class="line"><span class="cl">  0000 0011
+</span></span><span class="line"><span class="cl">&amp; 0000 1110 
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0000 1110
+</span></span></code></pre></div><p>为了避免上面<code>length=15</code>这类问题出现，所以集合的容量采用必须是2的N次幂这种方式。
+因为2的N次幂的结果减一转换为二进制后都是以<code>...1111</code>结尾的，所以在进行逻辑与运算时碰撞几率小。</p>
+<p>在JDK1.8中，在<code>putVal</code>方法中通过<code>i = (n - 1) &amp; hash</code>来计算key的散列地址：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="nf">putVal</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">onlyIfAbsent</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">evict</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 此处省略了代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// i = (n - 1) &amp; hash]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">hash</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tab</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newNode</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 省略了代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这里的&quot;&amp;&ldquo;等同于&rdquo;%&quot;，但是&quot;%&ldquo;运算的速度并没有&rdquo;&amp;&ldquo;的操作速度快。
+&ldquo;&amp;&ldquo;操作能代替&rdquo;%&ldquo;运算，但必须满足一定的条件，即<code>a%b=a&amp;(b-1)</code>仅当b是2的n次方的时候才成立。</p>
+<p>容器容量怎么保持始终为2的N次方？
+<code>HashMap</code>的<code>tableSizeFor</code>方法做了处理，能保证永远都是2的N次幂。
+如果用户指定了初始容量，那么<code>HashMap</code>会计算出比该数大的第一个2的幂作为初始容量。另外就是在扩容的时候，也是进行成倍的扩容，即4变成8、8变成16。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Returns a power of two size for the given target capacity.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">tableSizeFor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">cap</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 假设n=17</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = 00010001 - 00010000 = 00010000 = 16</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cap</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00010000 | 00001000) = 00011000 = 24</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011000 | 00000110) = 00011110 = 30</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011110 | 00000001) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011111 | 00000000) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">8</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = (00011111 | 00000000) = 00011111 = 31</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">|=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">16</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// n = 00011111 = 31，MAXIMUM_CAPACITY：Integer的最大长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// (31 &lt; 0) ? 1 : (31 &gt;= Integer的最大长度) ? Integer的最大长度 : 31 + 1 ;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 即最终返回 32 = 2 的 (n=5)次方</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>发现上面在进行<code>&gt;&gt;&gt;</code>操作时会将<code>cap</code>变量的二进制值变为最高位后边全是1，即<code>00010001 -&gt; 00011111</code>，所以这个算法就导致了任意传入一个数值，会将该数字变为它的2倍减1，因为任何尾数全为1的在加1都为2的倍数。
+至于开头减1，是因为如果给定的n已经是2的次幂，但是不进行减1操作的话，那么得到的值就是大于给定值的最小2的次幂值，例如，传入4就会返回8。
+这里面最大右移到16位，因为最大值是32个1，这是int类型存储变量的最大值，在往后就没意义了。</p>
+<p><code>HashMap</code>默认初始化容量为什么是16？
+这个问题没有找到相关解释。我推断这应该就是个经验值，既然一定要设置一个默认的<code>2^n</code>作为初始值，那么就需要在效率和内存使用上做一个权衡。
+这个值既不能太小，也不能太大，太小了就有可能频繁发生扩容，影响效率；太大了又浪费空间，不划算。所以16就作为一个经验值被采用了。</p>
+<p>关于默认容量的定义，故意把16写成<code>1 &lt;&lt; 4</code>这种形式，就是提醒开发者，这个地方要是2的次幂，与上面呼应。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * The default initial capacity - MUST be a power of two.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">4</span><span class="p">;</span><span class="w"> </span><span class="c1">// aka 16</span><span class="w">
+</span></span></span></code></pre></div><p>那么<code>HashMap</code>初始化容量设置多少合适？
+当我们使用<code>HashMap(int initialCapacity)</code>来初始化容量的时候，<code>HashMap</code>并不会使用我们传进来的<code>initialCapacity</code>直接作为初始容量。
+JDK会默认帮我们计算一个相对合理的值当做初始容量，所谓合理值，其实是找到第一个比用户传入的值大的2的幂。
+如果创建<code>HashMap</code>初始化容量设置为7，那么<code>HashMap</code>通过计算会创建一个初始化为8的<code>HashMap</code>。当<code>HashMap</code>中的元素到<code>0.75 * 8 = 6</code>就会进行<strong>扩容</strong>，这明显是我们不希望看到的。</p>
+<blockquote>
+<p>负载因子，表示HashMap满的程度，默认值为0.75f，也就是说默认情况下，当HashMap中元素个数达到了容量的3/4的时候就会进行自动扩容；</p>
+</blockquote>
+<p>设置多少合适，可以参考JDK8中<code>putAll</code>方法中的实现：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">(int) ((float) expectedSize / 0.75F + 1.0F);
+</span></span></code></pre></div><p>通过<code>expectedSize/0.75F+1.0F</code>计算，将初始化容量设置为7带入，得到<code>7/0.75+1=10</code>，10经过JDK处理之后，会被设置成16，这就大大的减少了扩容的几率。
+当我们明确知道<code>HashMap</code>中元素的个数的时候，把默认容量设置成<code>expectedSize/0.75F+1.0F</code> 是一个在性能上相对好的选择，但同时也会牺牲些内存。</p>
+<p>这个算法在<code>guava</code>中也有实现，开发的时候，可以直接通过<code>Maps</code>类创建一个<code>HashMap</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Maps</span><span class="p">.</span><span class="na">newHashMapWithExpectedSize</span><span class="p">(</span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">newHashMapWithExpectedSize</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedSize</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="p">(</span><span class="n">capacity</span><span class="p">(</span><span class="n">expectedSize</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">capacity</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedSize</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">expectedSize</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">3</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CollectPreconditions</span><span class="p">.</span><span class="na">checkNonnegative</span><span class="p">(</span><span class="n">expectedSize</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;expectedSize&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">expectedSize</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">expectedSize</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1073741824</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)((</span><span class="kt">float</span><span class="p">)</span><span class="n">expectedSize</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">75F</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">.</span><span class="na">0F</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">2147483647</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hashmap扩容">HashMap扩容</h3>
+<p>随着<code>HashMap</code>中的元素增加，<code>Hash</code>碰撞导致获取元素方法的效率就会越来越低。为了保证获取元素方法的效率，所以针对<code>HashMap</code>中的数组进行扩容。
+扩容数组的方式只能再去开辟一个新的数组，并把之前的元素转移到新数组上。</p>
+<p><code>HashMap</code>的容量是有上限的，必须小于<code>1&lt;&lt;30</code>，即<code>1073741824</code>。如果容量超出了这个数，则不再增长，且阈值会被设置为<code>Integer.MAX_VALUE</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// Java8
+</span></span><span class="line"><span class="cl">if (oldCap &gt;= MAXIMUM_CAPACITY) {
+</span></span><span class="line"><span class="cl">    threshold = Integer.MAX_VALUE;
+</span></span><span class="line"><span class="cl">    return oldTab;
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// Java7
+</span></span><span class="line"><span class="cl">if (oldCapacity == MAXIMUM_CAPACITY) { 
+</span></span><span class="line"><span class="cl">    threshold = Integer.MAX_VALUE;
+</span></span><span class="line"><span class="cl">    return;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>在<code>HashMap</code>中有一个概念叫<code>loadFactor</code>，即负载因子，它表示<code>HashMap</code>满的程度，默认值为<code>0.75f</code>，也就是说默认情况下，当<code>HashMap</code>中元素个数达到了容量的3/4的时候就会进行自动扩容。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">resize</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>为什么负载因子默认设置为0.75？</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * The load factor used when none specified in constructor.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">DEFAULT_LOAD_FACTOR</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">75f</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>在<a href="https://docs.oracle.com/javase/6/docs/api/java/util/HashMap.html">JDK的官方文档</a>中解释如下：</p>
+<blockquote>
+<p>As a general rule, the default load factor (.75) offers a good tradeoff between time and space costs.
+Higher values decrease the space overhead but increase the lookup cost (reflected in most of the operations of the HashMap class, including get and put).
+The expected number of entries in the map and its load factor should be taken into account when setting its initial capacity, so as to minimize the number of rehash operations.
+If the initial capacity is greater than the maximum number of entries divided by the load factor, no rehash operations will ever occur.</p>
+</blockquote>
+<p>文档大意：一般来说，默认的负载因子(0.75)在时间和空间成本之间提供了很好的权衡。
+更高的值减少了空间开销，但增加了查找成本(反映在<code>HashMap</code>类的大多数操作中，包括<code>get</code>和<code>put</code>)。
+在设置映射的初始容量时，应该考虑映射中预期的条目数及其负载因子，以便最小化重哈希操作的数量。如果初始容量大于最大条目数除以负载因子，则不会发生重新散列操作。</p>
+<p>负载因子和<code>HashMap</code>中的扩容有关，当<code>HashMap</code>中的元素大于临界值（<code>threshold = loadFactor * capacity</code>）就会扩容。
+所以负载因子的大小决定了什么时机扩容，扩容又影响到了hash碰撞的频率，所以设置一个合理的负载因子可以有效的避免<code>hash</code>碰撞。</p>
+<p>设置为0.75的其他解释：</p>
+<ul>
+<li>根据数学公式推算，这个值在<code>log(2)</code>的时候比较合理；</li>
+<li>为了提升扩容效率，<code>HashMap</code>的容量有一个固定的要求，那就是一定是2的幂。如果负载因子是3/4的话，那么和容量的乘积结果就可以是一个整数；</li>
+</ul>
+<h4 id="17扩容">1.7扩容</h4>
+<p>扩容步骤：</p>
+<ol>
+<li>当插入新的键值对使得元素数量超过阈值时，<code>HashMap</code>会进行扩容；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">addEntry</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">bucketIndex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//size：The number of key-value mappings contained in this map.  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//threshold：The next size value at which to resize (capacity * load factor)  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//数组扩容条件：1.已经存在的key-value mappings的个数大于等于阈值  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//             2.底层数组的bucketIndex坐标处不等于null  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">size</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">threshold</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="kc">null</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">table</span><span class="o">[</span><span class="n">bucketIndex</span><span class="o">]</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">(</span><span class="n">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">table</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="c1">//扩容之后，数组长度变了  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hash</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kc">null</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">hash</span><span class="p">(</span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="c1">//为什么要再次计算一下hash值呢？  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bucketIndex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">indexFor</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">table</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="c1">//扩容之后，数组长度变了，在数组的下标跟数组长度有关，得重算。  </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">createEntry</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="n">bucketIndex</span><span class="p">);</span><span class="w">  
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w"> 
+</span></span></span></code></pre></div></li>
+<li>创建一个新的数组，新的容量是原来的两倍，新阈值=新容量*负载因子；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">resize</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">   </span><span class="c1">//传入新的容量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">oldTable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">    </span><span class="c1">//引用扩容前的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldTable</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCapacity</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">  </span><span class="c1">//扩容前的数组大小如果已经达到最大(2^30)了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w"> </span><span class="c1">//修改阈值为int的最大值(2^31-1)，这样以后就不会扩容了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">newTable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Entry</span><span class="o">[</span><span class="n">newCapacity</span><span class="o">]</span><span class="p">;</span><span class="w">  </span><span class="c1">//初始化一个新的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">transfer</span><span class="p">(</span><span class="n">newTable</span><span class="p">);</span><span class="w">                         </span><span class="c1">//！！将数据转移到新的Entry数组里</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">table</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="p">;</span><span class="w">                           </span><span class="c1">//HashMap的table属性引用新的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">newCapacity</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">);</span><span class="c1">//修改阈值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>将旧表中的所有元素重新计算哈希值，并放入新表中：通过<code>transfer</code>方法将旧数组上的元素转移到扩容后的新数组上。遍历旧表中的每个桶，对于每个桶中的每个节点，重新计算它们在新表中的索引位置，将节点放入新表的相应位置；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">transfer</span><span class="p">(</span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">newTable</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="o">[]</span><span class="w"> </span><span class="n">src</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">                   </span><span class="c1">//src引用了旧的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">newCapacity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">src</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">//遍历旧的Entry数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">src</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">             </span><span class="c1">//取得旧Entry数组的每个元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">src</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="c1">//释放旧Entry数组的对象引用（for循环后，旧的Entry数组不再引用任何对象）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Entry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">indexFor</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="p">,</span><span class="w"> </span><span class="n">newCapacity</span><span class="p">);</span><span class="w"> </span><span class="c1">//！！重新计算每个元素在数组中的位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTable</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">//标记[1]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">newTable</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">      </span><span class="c1">//将元素放在数组上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">             </span><span class="c1">//访问下一个Entry链上的元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>将旧表引用指向新表；</li>
+</ol>
+<h4 id="18扩容">1.8扩容</h4>
+<p>Java1.8的<code>HashMap</code>扩容原理与1.7类似，但有一些重要改进。
+在1.8时做了一些优化，文档注释写的很清楚：&ldquo;元素的位置要么是在原位置，要么是在原位置再移动<strong>2次幂的位置</strong>&quot;。也就是对比1.7的迁移到新的数组上省去了重新计算<code>hash</code>值的时间。</p>
+<p>这里的&quot;2次幂的位置&quot;是指长度为原来数组元素两倍的位置。
+假设旧容量是16，那么其二进制表示是<code>10000</code>，扩容后的新容量是32，其二进制表示是<code>100000</code>。<code>HashMap</code>通过<code>h &amp; (length - 1)</code>计算索引。
+在扩容之前，容量为16，根据公式<code>hash &amp; (oldCapacity - 1)</code>计算，因为<code>oldCapacity - 1</code>的二进制是<code>0000 1111</code>，那么计算索引时使用的是哈希值的低四位。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">扩容之前的位置：
+</span></span><span class="line"><span class="cl">  0101 0101
+</span></span><span class="line"><span class="cl">&amp; 0000 1111
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0000 0101
+</span></span></code></pre></div><p>扩容后，新的索引还是通过<code>hash &amp; (newCapacity - 1)</code>计算的，若容量为32，因为<code>newCapacity - 1</code>的二进制是<code>0001 1111</code>，那么计算索引时使用的是哈希值的低五位。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">扩容之后的位置：
+</span></span><span class="line"><span class="cl">  0101 0101
+</span></span><span class="line"><span class="cl">&amp; 0001 1111
+</span></span><span class="line"><span class="cl">————————————
+</span></span><span class="line"><span class="cl">  0001 0101
+</span></span></code></pre></div><p>扩容后，新的索引位置只受到哈希值高位的影响，所以叫高位优化。
+高位优化的关键在于，如果一个哈希值在旧容量下的索引是<code>index</code>，那么在新容量下，这个哈希值要么在<code>index</code>位置，要么在<code>index + oldCapacity</code>位置。
+例如上面的例子，容量为16，扩容之前的位置为<code>0000 0101</code>即5，扩容之后的位置为<code>0001 0101</code>即21（16+5）。
+通过这种高位优化技术，Java1.8中的<code>HashMap</code>在扩容时无需重新计算所有元素的哈希值，只需根据哈希值的高位来判断元素的新位置，所以提高了扩容的效率。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Initializes or doubles table size.  If null, allocates in
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * accord with initial capacity target held in field threshold.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Otherwise, because we are using power-of-two expansion, the
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * elements from each bin must either stay at same index, or move
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * with a power of two offset in the new table.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return the table
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="nf">resize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">oldTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">oldTab</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">oldTab</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">oldThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">threshold</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newCap</span><span class="p">,</span><span class="w"> </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">oldTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldCap</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                     </span><span class="n">oldCap</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldThr</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// double threshold</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldThr</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="c1">// initial capacity was placed in threshold</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldThr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">               </span><span class="c1">// zero initial threshold signifies using defaults</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newCap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)(</span><span class="n">DEFAULT_LOAD_FACTOR</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">DEFAULT_INITIAL_CAPACITY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newThr</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">float</span><span class="w"> </span><span class="n">ft</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="n">newCap</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newThr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">newCap</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">ft</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="n">MAXIMUM_CAPACITY</span><span class="w"> </span><span class="o">?</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                      </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">ft</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newThr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">({</span><span class="s">&#34;rawtypes&#34;</span><span class="p">,</span><span class="s">&#34;unchecked&#34;</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">newTab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">[</span><span class="n">newCap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">table</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">oldTab</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">oldCap</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">oldTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 单个节点，直接移动到新表中的新位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">newTab</span><span class="o">[</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">newCap</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">TreeNode</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 红黑树节点，处理红黑树的拆分逻辑</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">((</span><span class="n">TreeNode</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">e</span><span class="p">).</span><span class="na">split</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">newTab</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="p">,</span><span class="w"> </span><span class="n">oldCap</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// preserve order</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 处理链表节点，使用高位优化技术重新分配节点</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">loHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">loTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hiHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">hiTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                           </span><span class="c1">// 判断节点在新表中的位置，高位优化的关键</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="p">.</span><span class="na">hash</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">oldCap</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                               </span><span class="c1">// 保持在原位置（低位链表）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">loHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">loTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">loTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                               </span><span class="c1">// 移动到新位置（高位链表）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">hiTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">hiHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                    </span><span class="n">hiTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">hiTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="c1">// 将低位链表和高位链表分别放入新表中的相应位置</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loTail</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">loTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">newTab</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">loHead</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">hiTail</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">hiTail</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">newTab</span><span class="o">[</span><span class="n">j</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">oldCap</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hiHead</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">newTab</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="线程安全-2">线程安全</h3>
+<p><code>HashMap</code>是线程不安全的集合类。因为<code>HashMap</code>中的方法大多没有同步，这意味着如果一个线程在遍历<code>HashMap</code>的同时，另一个线程修改了<code>HashMap</code>，例如添加或删除元素，可能会导致<code>ConcurrentModificationException</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="n">Object</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">(),</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">map</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>更严重的是，当多个线程中的<code>HashMap</code>同时扩容时，再使用<code>put</code>方法添加元素，如果<code>hash</code>值相同，可能出现同时在同一数组下用链表表示，造成闭环，导致在<code>get</code>时会出现死循环，CPU飙升到100%。</p>
+<p>在大多数并发场景中，推荐使用<code>ConcurrentHashMap</code>，因为它设计用于高并发环境，并且在大多数情况下性能优于使用同步包装或手动同步的<code>HashMap</code>。
+<code>ConcurrentHashMap</code>是Java中的一种线程安全的哈希表实现，用来替代传统的<code>HashMap</code>，来解决在多线程环境中并发修改带来的问题。
+与<code>Hashtable</code>不同，<code>ConcurrentHashMap</code>不对整个表进行全局加锁。相反它只对具体操作涉及的部分进行加锁，减少了线程之间的竞争。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConcurrentHashMapExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ConcurrentHashMap</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcurrentHashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;One&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Two&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Value for key 1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">keySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Key: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Value: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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+    
+    <a id="back_to_top" href="#" class="back_to_top">
+        <svg t="1688628374733" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3166" width="16" height="16"><path d="M966.4 668.8l-435.2-432c-9.6-9.6-25.6-9.6-35.2 0l-441.6 432c-9.6 9.6-9.6 25.6 0 35.2 9.6 9.6 25.6 9.6 35.2 0l425.6-416 416 416c9.6 9.6 25.6 9.6 35.2 0S976 678.4 966.4 668.8z" p-id="3167" fill="#424242"></path></svg>
+    </a>
+</div>
+    <footer class="footer">
+    <div id="footer_powered_by" class="powered_by">
+        <a href="https://varkai.com">Designed by VarKai,</a>
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+    <div id="footer_slogan" class="footer_slogan">
+        <span>from 2021</span>
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+<script src="https://whiteppure.github.io/iblog/js/darkmode.js"></script>
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+
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+<script>
+    new Darkmode({
+        right: '32px', 
+        bottom: 'unset', 
+        
+        time: '0.15s', 
+        mixColor: '#f7f7f7', 
+        backgroundColor: '#f7f7f7', 
+        buttonColorDark: '#212121', 
+        buttonColorLight: '#f7f7f7', 
+        saveInCookies: false, 
+        autoMatchOsTheme: true 
+    }).showWidget();
+
+    function addDarkmodeWidget(){
+        const hours = new Date().getHours();
+        if (hours >= 19 || hours <= 5){
+            new Darkmode({
+                right: '32px', 
+                bottom: 'unset', 
+                
+                time: '0.3s', 
+                mixColor: '#f7f7f7', 
+                backgroundColor: '#f7f7f7', 
+                buttonColorDark: '#212121', 
+                buttonColorLight: '#f7f7f7', 
+                saveInCookies: false, 
+                autoMatchOsTheme: true 
+            }).toggle();
+        }
+    }
+    
+    
+</script>
+
+
+
+
+
+
+
+
+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/docs/posts/javabasics/rookie-multi-thread/index.html b/docs/posts/javabasics/rookie-multi-thread/index.html
new file mode 100644
index 00000000..c61d9240
--- /dev/null
+++ b/docs/posts/javabasics/rookie-multi-thread/index.html
@@ -0,0 +1,6708 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java多线程 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="线程与进程 进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。 线程是操作系统能够进行运算调度的最小单位。它被包" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
+    
+
+	
+
+    <link rel="shortcut icon" href="https://whiteppure.github.io/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e4%b8%8e%e8%bf%9b%e7%a8%8b">
+                    线程与进程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e7%9a%84%e5%b9%b6%e8%a1%8c%e4%b8%b2%e8%a1%8c%e5%b9%b6%e5%8f%91">
+                    线程的并行、串行、并发
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e7%9a%84%e5%90%8c%e6%ad%a5%e5%bc%82%e6%ad%a5">
+                    线程的同步、异步
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%88%e6%8a%a4%e7%ba%bf%e7%a8%8b">
+                    守护线程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8">
+                    线程安全
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e7%9a%84%e7%8a%b6%e6%80%81">
+                    线程的状态
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e7%9b%b8%e5%85%b3%e6%96%b9%e6%b3%95">
+                    线程相关方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%9b%e5%bb%ba%e7%ba%bf%e7%a8%8b">
+                    创建线程
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#thread">
+                    Thread
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#runnable">
+                    Runnable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#callable">
+                    Callable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e6%b1%a0">
+                    线程池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%88%9b%e5%bb%ba%e6%96%b9%e5%bc%8f">
+                    创建方式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%87%aa%e5%ae%9a%e4%b9%89%e7%ba%bf%e7%a8%8b%e6%b1%a0">
+                    自定义线程池
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e6%b1%a0%e5%b7%a5%e4%bd%9c%e5%8e%9f%e7%90%86">
+                    线程池工作原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%98%bb%e5%a1%9e%e9%98%9f%e5%88%97">
+                    阻塞队列
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e6%b1%a0%e5%8f%82%e6%95%b0">
+                    线程池参数
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%90%88%e7%90%86%e9%85%8d%e7%bd%ae%e7%ba%bf%e7%a8%8b%e6%b1%a0%e5%8f%82%e6%95%b0">
+                    合理配置线程池参数
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%94%81">
+                    锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%ac%e5%b9%b3%e9%94%81%e4%b8%8e%e9%9d%9e%e5%85%ac%e5%b9%b3%e9%94%81">
+                    公平锁与非公平锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%af%e9%87%8d%e5%85%a5%e9%94%81%e4%b8%8e%e4%b8%8d%e5%8f%af%e9%87%8d%e5%85%a5%e9%94%81">
+                    可重入锁与不可重入锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%b1%e4%ba%ab%e9%94%81%e4%b8%8e%e7%8b%ac%e5%8d%a0%e9%94%81">
+                    共享锁与独占锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%82%b2%e8%a7%82%e9%94%81%e4%b8%8e%e4%b9%90%e8%a7%82%e9%94%81">
+                    悲观锁与乐观锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%87%aa%e6%97%8b%e9%94%81%e4%b8%8e%e9%80%82%e5%ba%94%e6%80%a7%e8%87%aa%e6%97%8b%e9%94%81">
+                    自旋锁与适应性自旋锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%81%8f%e5%90%91%e9%94%81">
+                    偏向锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bd%bb%e9%87%8f%e7%ba%a7%e9%94%81%e4%b8%8e%e9%87%8d%e9%87%8f%e7%ba%a7%e9%94%81">
+                    轻量级锁与重量级锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%af%e4%b8%ad%e6%96%ad%e9%94%81">
+                    可中断锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%92%e6%96%a5%e9%94%81">
+                    互斥锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%ad%bb%e9%94%81">
+                    死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e8%b5%84%e6%ba%90%e6%9c%89%e5%ba%8f%e5%88%86%e9%85%8d%e6%b3%95%e9%81%bf%e5%85%8d%e6%ad%bb%e9%94%81">
+                    使用资源有序分配法避免死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e9%93%b6%e8%a1%8c%e5%ae%b6%e7%ae%97%e6%b3%95%e9%81%bf%e5%85%8d%e6%ad%bb%e9%94%81">
+                    使用银行家算法避免死锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8trylock%e8%bf%9b%e8%a1%8c%e8%b6%85%e6%97%b6%e9%94%81%e5%ae%9a">
+                    使用tryLock进行超时锁定
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#java%e5%86%85%e5%ad%98%e6%a8%a1%e5%9e%8b">
+                    Java内存模型
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8e%9f%e5%ad%90%e6%80%a7">
+                    原子性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%af%e8%a7%81%e6%80%a7">
+                    可见性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9c%89%e5%ba%8f%e6%80%a7">
+                    有序性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%99%90%e5%88%b6%e5%a4%84%e7%90%86%e5%99%a8%e4%bc%98%e5%8c%96">
+                    限制处理器优化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%85%e5%ad%98%e5%b1%8f%e9%9a%9c">
+                    内存屏障
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#happens-before">
+                    Happens-Before
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#as-if-serial">
+                    as-if-serial
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#volatile">
+                    volatile
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e6%a1%88%e4%be%8b">
+                    使用案例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#volatile%e4%b8%8e%e5%8f%af%e8%a7%81%e6%80%a7">
+                    volatile与可见性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#volatile%e4%b8%8e%e6%9c%89%e5%ba%8f%e6%80%a7">
+                    volatile与有序性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#volatile%e4%b8%8e%e5%8e%9f%e5%ad%90%e6%80%a7">
+                    volatile与原子性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#synchronized">
+                    synchronized
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e7%a4%ba%e4%be%8b">
+                    使用示例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86">
+                    实现原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%94%81%e7%9a%84%e5%8d%87%e7%ba%a7">
+                    锁的升级
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#synchronized%e4%b8%8e%e5%8f%af%e8%a7%81%e6%80%a7">
+                    synchronized与可见性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#synchronized%e4%b8%8e%e5%8e%9f%e5%ad%90%e6%80%a7">
+                    synchronized与原子性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#synchronized%e4%b8%8e%e6%9c%89%e5%ba%8f%e6%80%a7">
+                    synchronized与有序性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cas">
+                    CAS
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e7%a4%ba%e4%be%8b-1">
+                    使用示例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#unsafe">
+                    Unsafe
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86-1">
+                    实现原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cas%e9%97%ae%e9%a2%98">
+                    CAS问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#juc%e5%8c%85">
+                    J.U.C.包
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#lock">
+                    Lock
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#readwritelock">
+                    ReadWriteLock
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#locksupport">
+                    LockSupport
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#aqs">
+                    AQS
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#reentrantlock">
+                    ReentrantLock
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e6%af%94synchronized">
+                    对比synchronized
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8a%a0%e9%94%81%e5%8e%9f%e7%90%86">
+                    加锁原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8a%e6%94%be%e9%94%81%e5%8e%9f%e7%90%86">
+                    释放锁原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#countdownlatch">
+                    CountDownLatch
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cyclicbarrier">
+                    CyclicBarrier
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#semaphore">
+                    Semaphore
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#threadlocal">
+                    ThreadLocal
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e6%af%94%e7%ba%bf%e7%a8%8b%e5%90%8c%e6%ad%a5">
+                    对比线程同步
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8%e7%a4%ba%e4%be%8b-2">
+                    使用示例
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86-2">
+                    实现原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%86%85%e5%ad%98%e6%b3%84%e6%bc%8f%e9%97%ae%e9%a2%98">
+                    内存泄漏问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b8%b8%e7%94%a8%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8%e7%9a%84%e9%9b%86%e5%90%88">
+                    常用线程安全的集合
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#copywritearraylist">
+                    CopyWriteArrayList
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#copyonwritearrayset">
+                    CopyOnWriteArraySet
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashtable">
+                    HashTable
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#concurrenthashmap">
+                    ConcurrentHashMap
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jdk17">
+                    JDK1.7
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jdk18">
+                    JDK1.8
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e8%80%83%e6%96%87%e7%ab%a0">
+                    参考文章
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="https://whiteppure.github.io/iblog/">首页</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="https://whiteppure.github.io/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="https://whiteppure.github.io/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                        <h2 id="post_single_title">Java多线程</h2>
+                        <span id="post_page_title_date" class="date">2021.05.05</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
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+                    <div class="post_content markdown"><h2 id="线程与进程">线程与进程</h2>
+<ul>
+<li>进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。</li>
+<li>线程是操作系统能够进行运算调度的最小单位。它被包含在进程之中，是进程中的实际执行单位。一个进程可以包含多个线程，这些线程共享进程的内存空间和资源，但有自己的栈和程序计数器。</li>
+</ul>
+<p>进程是操作系统资源分配的基本单位，而线程是处理器任务调度和执行的基本单位。
+一条线程指的是进程中的一个单一顺序的控制流，一个进程至少有一个线程，一个进程中可以并发多个线程，多个线程可共享数据，每条线程并行执行不同的任务。</p>
+<p>Java程序是多线程程序，每启动一个Java程序，至少我们知道的都会包含一个主线程和一个垃圾回收线程。而且启动的时候，每条线程可以并行执行不同的任务。</p>
+<p><img alt="线程与进程的关系" src="/iblog/posts/annex/images/essays/%E7%BA%BF%E7%A8%8B%E4%B8%8E%E8%BF%9B%E7%A8%8B%E7%9A%84%E5%85%B3%E7%B3%BB.jpg"></p>
+<h2 id="线程的并行串行并发">线程的并行、串行、并发</h2>
+<ul>
+<li>并行：前提是在多核CPU，多个线程同时被多个CPU执行，同时执行的线程并不会抢占CPU资源。</li>
+<li>串行：前提是在单核CPU条件下，单线程程序执行，不能同时执行，也不能去切换执行，也就是在同一时间段只能做一件事，如果需要做多件事情需要排队执行。</li>
+<li>并发：前提是多线程条件下，多个线程抢占一个CPU资源，多个线程被交替执行。因为CPU运算速度很快，所以用户感觉不到线程切换的卡顿。</li>
+</ul>
+<table>
+<thead>
+<tr>
+<th></th>
+<th style="text-align:center">单线程</th>
+<th>多线程</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>单CPU</td>
+<td style="text-align:center">串行</td>
+<td>并发</td>
+</tr>
+<tr>
+<td>多CPU</td>
+<td style="text-align:center">串行</td>
+<td>并行</td>
+</tr>
+</tbody>
+</table>
+<p>无论并行、并发，都可以有多个线程执行，如果是多个线程抢占一个CPU，交替执行，并且CPU通过时间片轮转等机制切换执行线程，这种情况下称为并发执行。
+多个线程同时被多个CPU执行，并且各个线程之间不会互相抢占CPU资源，这种情况下称为并行执行。每个线程都在自己的CPU核心上独立执行，互不干扰。</p>
+<p>对于单CPU的计算机来说，同一时间是只能干一件事儿的，如果是单线程就是串行，如果是多个线程就是并发。
+而对于多CPU的计算机说，同一时间能干多个事，如果多个CPU同时执行多个线程就是并行，如果一个CPU同时执行多个线程就是并行。</p>
+<p>并行与并发区别图解
+<img alt="并行与并发区别" src="/iblog/posts/annex/images/essays/%E5%B9%B6%E8%A1%8C%E4%B8%8E%E5%B9%B6%E5%8F%91%E5%8C%BA%E5%88%AB.png"></p>
+<p>并发是两个队列交替使用一台咖啡机，并行是两个队列同时使用两台咖啡机；
+如果串行，一个队列使用一台咖啡机，那么哪怕前面那个人便秘了去厕所呆半天，后面的人也只能死等着他回来才能去接咖啡，这种效率无疑是最低的。</p>
+<h2 id="线程的同步异步">线程的同步、异步</h2>
+<ul>
+<li>同步指的是按顺序执行任务，一个任务的执行必须等待前一个任务完成后才能继续。在同步模式下，任务按照严格的顺序依次执行，每个任务执行完毕后才能进行下一个任务。
+例如，使用关键字<code>synchronized</code>或<code>Lock</code>接口可以实现多线程的同步，确保多个线程按照特定的顺序或条件执行。</li>
+<li>异步指的是任务的执行不依赖于主线程或当前线程，可以通过回调、事件驱动等方式实现任务的并行执行或后台执行。 异步任务可以在任务执行过程中继续执行其他任务，不需要等待当前任务完成。
+异步在Java中通常通过多线程、回调函数或<code>Future</code>、<code>CompletableFuture</code>等方式实现。</li>
+</ul>
+<p>线程与同步异步关系：</p>
+<ul>
+<li>单线程环境下，所有任务按顺序同步执行。如果某个任务阻塞或者等待，整个程序会停止执行直到该任务完成。</li>
+<li>多线程环境下，同步任务可以通过加锁等机制实现对共享资源的安全访问，保证数据的一致性。多线程中的同步操作可以确保多个线程协调执行，避免数据竞争和不一致问题。</li>
+<li>单线程环境中，异步模式通过事件驱动或者非阻塞IO方式实现，可以模拟多任务并发执行的效果。虽然不能真正并行执行多个任务，但可以利用非阻塞方式处理IO或事件，提高响应速度。</li>
+<li>多线程环境中，异步操作通常通过新线程或线程池执行，实现任务的并行处理。多线程中的异步操作可以提高系统的吞吐量和响应能力，充分利用多核处理器的优势。</li>
+</ul>
+<table>
+<thead>
+<tr>
+<th></th>
+<th>单线程</th>
+<th>多线程</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>同步</td>
+<td>只能同步执行，按照顺序执行任务</td>
+<td>可以同步执行，多个线程按顺序执行任务</td>
+</tr>
+<tr>
+<td>异步</td>
+<td>不能直接异步执行，但可以通过事件循环或非阻塞IO模型实现类似异步效果</td>
+<td>可以异步执行，通过多线程或者线程池来实现并行处理</td>
+</tr>
+</tbody>
+</table>
+<h2 id="守护线程">守护线程</h2>
+<p>守护线程是指为其他线程服务的线程。守护线程也称“服务线程”，在没有用户线程可服务时会自动离开。因为作用是服务其他线程，所以在程序中的优先级比较低。
+在JVM中，所有非守护线程都执行完毕后，无论有没有守护线程，虚拟机都会自动退出。</p>
+<p>举例，垃圾回收线程就是一个经典的守护线程，当我们的程序中不再有任何运行的线程，程序就不会再产生垃圾，垃圾回收器也就无事可做。
+所以当垃圾回收线程是JVM上仅剩的线程时，垃圾回收线程会自动离开。它始终在低级别的状态中运行，用于实时监控和管理系统中的可回收资源。
+守护线程在程序中的操作演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="w"> </span><span class="n">daemon</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;启动线程---&gt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">daemon</span><span class="p">.</span><span class="na">setDaemon</span><span class="p">(</span><span class="n">i</span><span class="o">==</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">daemon</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isDaemon</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">daemon</span><span class="p">.</span><span class="na">isDaemon</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前线程是否是守护线程：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">isDaemon</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isDaemon</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">i</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="线程安全">线程安全</h2>
+<p>线程安全是指在多线程环境下，一个类、方法或代码块能够被多个线程安全地访问和修改，不会导致数据不一致性或产生不可预测的行为。线程安全通常通过同步机制实现，来确保多个线程不会同时访问或修改共享资源。</p>
+<p>在多线程并发环境中，多个线程共同操作同一个数据，如果最终数据的值与预期不一致，就会出现线程不安全问题。
+为了解决这个问题，Java中最常用的方法是加锁。当一个线程修改某个数据时，其他线程不能访问该数据，直到该线程操作结束并释放锁，其他线程才能继续操作该数据。</p>
+<p>线程安全问题的根本原因：</p>
+<ul>
+<li>CPU切换线程执导致的原子性问题。当CPU在执行线程时进行上下文切换，一个线程的操作可能在执行一半时被中断，导致另一个线程看到不完整的操作结果，从而出现数据不一致。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Counter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w"> </span><span class="c1">// 这个操作实际上分为三步：读取count值、增加1、写回count值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>缓存可见性问题。由于CPU、内存、IO设备读写速度差异巨大，为了减少CPU等待IO的时间，在CPU和内存之间引入了高速缓存。多核CPU的情况下，每个核心有自己的缓存，这会导致高速缓存与主内存之间的数据不一致，即一个核心对变量的修改，另一个核心可能看不到。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SharedData</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setFlag</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">getFlag</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">flag</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>指令优化重排序问题。编译器和处理器为了优化性能，可能会对指令进行重排序，这不会影响单线程环境下的执行结果，但在多线程环境下，可能导致程序行为不可预测。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Example</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">write</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">           </span><span class="c1">// 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">     </span><span class="c1">// 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">read</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">      </span><span class="c1">// 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="p">);</span><span class="w"> </span><span class="c1">// 4</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h2 id="线程的状态">线程的状态</h2>
+<p>线程状态共包含6种，通过<code>Thread.State</code>枚举类表示的。6种状态又可以互相的转换，线程状态转换关系：</p>
+<p><img alt="线程状态转换" src="/iblog/posts/annex/images/essays/%E7%BA%BF%E7%A8%8B%E8%BD%AC%E6%8D%A2%E5%9B%BE.jpg"></p>
+<ol>
+<li>新建状态(New): 线程被创建但尚未启动。例如，<code>Thread t = new Thread();</code> 状态为NEW；调用线程对象的<code>start()</code>方法会使线程从NEW状态转变为RUNNABLE状态。</li>
+<li>可运行状态(Runnable): 线程在Java虚拟机中执行中。这包括运行状态和就绪状态，线程可能正在运行，也可能等待操作系统为其分配CPU时间。
+<ul>
+<li>就绪（Ready）：线程已经被创建，等待被调度执行。此时可能有多个线程处于就绪状态，但只有一个线程能够获取CPU时间片执行。</li>
+<li>运行中（Running）：就绪的线程获得了CPU时间片，开始执行程序代码。</li>
+</ul>
+</li>
+<li>阻塞状态(Blocked): 当一个线程试图进入一个同步代码块或方法，但该同步块已经被其他线程持有时，线程将进入阻塞状态。阻塞状态的线程将等待获取同步锁，一旦获取到锁就可以转变为RUNNABLE状态。</li>
+<li>无限期等待(Waiting): 当线程调用<code>Object.wait()</code>、<code>Thread.join()</code>或<code>LockSupport.park()</code>方法时，它会进入WAITING状态，直到被其他线程显式唤醒。线程被唤醒后可以转变为RUNNABLE状态。</li>
+<li>限期等待(Timed Waiting): 当线程调用带有超时参数的等待方法，如<code>sleep()</code>、<code>wait(timeout)</code>、<code>join(timeout)</code>、<code>LockSupport.parkNanos()</code>或<code>LockSupport.parkUntil()</code>时，它会进入TIMED_WAITING状态，直到超时时间到达或被其他线程唤醒。
+超时时间到达或被唤醒后可以转变为RUNNABLE状态。</li>
+<li>死亡(Terminated): 线程完成<code>run()</code>方法的执行或者因异常而终止时，会进入TERMINATED状态。一旦线程的<code>run()</code>方法执行完成或抛出未捕获的异常，线程将进入终止状态。</li>
+</ol>
+<p>阻塞和等待的区别在于，阻塞是被动的，它是在等待获取一个排它锁。而等待是主动的，通过调用<code>Thread.sleep()</code>和<code>Object.wait()</code>等方法进入等待。</p>
+<h2 id="线程相关方法">线程相关方法</h2>
+<ul>
+<li><code>start()</code>：启动一个新线程，调用线程的<code>run()</code>方法。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Thread is running&#34;);
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start();
+</span></span></code></pre></div></li>
+<li><code>run()</code>：运行线程中的代码。可以通过继承<code>Thread</code>类并重写<code>run()</code>方法，或通过实现<code>Runnable</code>接口并传递给<code>Thread</code>类的构造函数。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public class MyThread extends Thread {
+</span></span><span class="line"><span class="cl">    public void run() {
+</span></span><span class="line"><span class="cl">        System.out.println(&#34;Thread is running&#34;);
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">MyThread t = new MyThread();
+</span></span><span class="line"><span class="cl">t.start();
+</span></span></code></pre></div></li>
+<li><code>sleep(long millis)</code>：让当前线程休眠指定的毫秒数。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    Thread.sleep(1000); // 休眠1秒
+</span></span><span class="line"><span class="cl">} catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>join()</code>：当有新的线程加入时，主线程会进入等待状态，一直到调用<code>join()</code>方法的线程执行结束为止。<code>join()</code>方法的实现依赖于对象的<code>wait()</code>方法。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    try {
+</span></span><span class="line"><span class="cl">        Thread.sleep(2000);
+</span></span><span class="line"><span class="cl">    } catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">        e.printStackTrace();
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start();
+</span></span><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    t.join();
+</span></span><span class="line"><span class="cl">} catch (InterruptedException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>yield()</code>：用于让当前正在执行的线程暂时让出CPU的执行权，使其他线程有机会运行。它不会使线程进入阻塞或等待状态，只是让出当前的CPU时间片，让同等优先权的线程运行。
+如果没有同等优先权的线程，那么<code>yield()</code>方法将不会起作用。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public void run() {
+</span></span><span class="line"><span class="cl">    for (int i = 0; i &lt; 5; i++) {
+</span></span><span class="line"><span class="cl">        System.out.println(threadName + &#34; is running, iteration: &#34; + i);
+</span></span><span class="line"><span class="cl">        // 暂时让出CPU执行权，给其他线程机会
+</span></span><span class="line"><span class="cl">        Thread.yield();
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    System.out.println(threadName + &#34; has finished execution.&#34;);
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">public static void main(String[] args) {
+</span></span><span class="line"><span class="cl">    Thread thread1 = new Thread(new YieldExample(&#34;Thread 1&#34;));
+</span></span><span class="line"><span class="cl">    Thread thread2 = new Thread(new YieldExample(&#34;Thread 2&#34;));
+</span></span><span class="line"><span class="cl">    thread1.start();
+</span></span><span class="line"><span class="cl">    thread2.start();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>wait()</code>：使当前线程等待，直到另一个线程调用该对象的<code>notify()</code>或<code>notifyAll()</code>方法。<code>wait()</code>必须在同步<code>synchronized</code>块里使用。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">synchronized (lock) {
+</span></span><span class="line"><span class="cl">    lock.wait();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>notify()</code>：唤醒一个正在等待该对象的<code>wait()</code>方法的线程。如果多个线程都在该对象的监视器上等待，则任意选择一个线程被唤醒。
+<code>notify()</code>方法必须与<code>wait()</code>方法一起使用，否则会抛出<code>IllegalMonitorStateException</code>异常。<code>notify()</code>方法必须在同步代码块或同步方法中调用，因为它依赖于对象的监视器锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doWaitNotify</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">waitingThread</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is waiting...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w"> </span><span class="c1">// 进入等待状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is notified and resumed.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">waitingThread</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟一些操作延迟</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Notifying waiting thread...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notify</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒等待的线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>需要注意区分<code>wait</code>方法与<code>sleep</code>方法，很多人分不清。<code>sleep</code>和<code>wait</code>方法异同点：</p>
+<ul>
+<li><code>sleep()</code>属于<code>Thread</code>类，<code>wait()</code>属于<code>Object</code>类；</li>
+<li><code>sleep()</code>和<code>wait()</code>都会抛出<code>InterruptedException</code>异常，这个异常属于<code>checkedException</code>是不可避免；</li>
+<li>两者比较的共同之处是，都是使程序等待多长时间。不同的是调用<code>sleep()</code>不会释放锁，会使线程堵塞，而调用<code>wait()</code>会释放锁，让线程进入等待状态，用 <code>notify()</code>、<code>notifyall()</code>可以唤醒，或者等待时间到了；这是因为，如果没有释放锁，那么其它线程就无法进入对象的同步方法或者同步控制块中，那么就无法执行 <code>notify()</code> 或者 <code>notifyAll()</code> 来唤醒挂起的线程，造成死锁。</li>
+<li><code>wait()</code>必须在同步<code>synchronized</code>块里使用，<code>sleep()</code>可以在任意地方使用；</li>
+</ul>
+<p>其中&quot;<code>wait()</code>必须在同步<code>synchronized</code>块里使用&quot;，不止<code>wait</code>方法，<code>notify、notifyAll</code>也和<code>wait</code>方法一样，必须在<code>synchronized</code>块里使用，为什么呢？</p>
+<p>是为了避免丢失唤醒问题。假设没有<code>synchronized</code>修饰，使用了<code>wait</code>方法而没有设置等待时间，也没有调用唤醒方法或者唤醒方法调用的时机不对，这个线程将会永远的堵塞下去。
+<code>wait</code>、<code>notify</code>、<code>notifyAll</code>方法调用的时候要释放锁，你都没给它加锁，他怎么释放锁。所以如果没在<code>synchronized</code>块中调用<code>wait()、notify、notifyAll</code>方法是肯定抛异常的。</p>
+<h2 id="创建线程">创建线程</h2>
+<p>在Java中创建一个线程，有且仅有一种方式，创建一个<code>Thread</code>类实例，并调用它的<code>start</code>方法。</p>
+<h3 id="thread">Thread</h3>
+<p>最经典也是最常见的方式是通过继承<code>Thread</code>类，重写<code>run()</code>方法来创建线程。适用于需要直接控制线程生命周期的情况。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ThreadDemo</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadDemo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ThreadDemo</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;通过继承Thread类的方式创建线程,线程 %s 启动&#34;</span><span class="p">,</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="runnable">Runnable</h3>
+<p>实现<code>Runnale</code>接口，将它作为<code>target</code>参数传递给<code>Thread</code>类构造函数的方式创建线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;通过实现Runnable接口的方式，重写run方法创建线程；线程 %s 启动&#34;</span><span class="p">,</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="callable">Callable</h3>
+<p><code>Callable</code>接口与<code>Runnable</code>类似，但它可以返回结果，并且可以抛出异常，需要配合<code>Future</code>接口使用。通过实现<code>Callable</code>接口，来创建一个带有返回值的线程。
+在<code>Callable</code>执行完之前的这段时间，主线程可以先去做一些其他的事情，事情都做完之后，再获取<code>Callable</code>的返回结果。可以通过<code>isDone()</code>来判断子线程是否执行完。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">ExecutionException</span><span class="p">,</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FutureTask</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">futureTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FutureTask</span><span class="o">&lt;&gt;</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;通过实现Callable接口的方式，重写call方法创建线程；线程 %s 启动&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">10000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;我是call方法返回值&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">futureTask</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;主线程工作中 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">callRet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">callRet</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="p">(</span><span class="n">futureTask</span><span class="p">.</span><span class="na">isDone</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">callRet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">futureTask</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;主线程继续工作 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;获取call方法返回值：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">callRet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在实际开发中，通常使用异步编程工具，如<code>CompletableFuture</code>。
+<code>CompletableFuture</code>是JDK8的新特性。<code>CompletableFuture</code>实现了<code>CompletionStage</code>接口和<code>Future</code>接口，前者是对后者的一个扩展，增加了异步会点、流式处理、多个<code>Future</code>组合处理的能力，使Java在处理多任务的协同工作时更加顺畅便利。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CompletableFutureRunAsyncExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CompletableFuture</span><span class="o">&lt;</span><span class="n">Void</span><span class="o">&gt;</span><span class="w"> </span><span class="n">future</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CompletableFuture</span><span class="p">.</span><span class="na">runAsync</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 异步执行的任务，没有返回值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Running asynchronously&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">future</span><span class="p">.</span><span class="na">thenRun</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After running asynchronously&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">future</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w"> </span><span class="c1">// 等待任务完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CompletableFuture</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">future</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CompletableFuture</span><span class="p">.</span><span class="na">supplyAsync</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="s">&#34;Hello&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">thenApply</span><span class="p">(</span><span class="n">result</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; CompletableFuture!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="线程池">线程池</h3>
+<p>线程池做的工作主要是控制运行的线程的数量，处理过程中将任务放入队列，然后在线程创建后启动这些任务。如果线程数量超过了最大数量超出数量的线程排队等候，等其它线程执行完毕，再从队列中取出任务来执行。
+线程池是一种用于管理和复用线程的机制，可以有效地提高应用程序的性能和资源利用率。它的主要特点为：线程复用，提高响应速度，管理线程。</p>
+<ul>
+<li>降低资源消耗，通过重复利用己创建的线程降低线程创建和销毁造成的消耗。</li>
+<li>提高响应速度，当任务到达时，任务可以不需要的等到线程创建就能立即执行。</li>
+<li>提高线程的管理性，线程是稀缺资源，如果无限制的创建，不仅会消耗系统资源，还会降低系统的稳定性，使用线程池可以进行统一的分配，调优和监控。</li>
+</ul>
+<h4 id="创建方式">创建方式</h4>
+<p>在Java中，使用<code>java.util.concurrent</code>包中的<code>Executor</code>来创建和管理线程池。几种常见的线程池创建方式：</p>
+<ul>
+<li><code>Executors.newSingleThreadExecutor()</code>：创建只有一个线程的线程池。</li>
+<li><code>Executors.newFixedThreadPool(int)</code>：创建固定线程的线程池。</li>
+<li><code>Executors.newCachedThreadPool()</code>：创建一个可缓存的线程池，线程数量随着处理业务数量变化。</li>
+</ul>
+<p>这三种常用创建线程池的方式，底层代码都是用<code>ThreadPoolExecutor</code>创建的。</p>
+<ol>
+<li>
+<p>使用<code>Executors.newSingleThreadExecutor()</code>创建一个单线程化的线程池，它只会用唯一的工作线程来执行任务，保证所有任务按照指定顺序执行。
+<code>newSingleThreadExecutor</code>将<code>corePoolSize</code>和<code>maximumPoolSize</code>都设置为1，它使用的<code>LinkedBlockingQueue</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">ExecutorService</span><span class="w"> </span><span class="nf">newSingleThreadExecutor</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FinalizableDelegatedExecutorService</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">0L</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedBlockingQueue</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Executors</span><span class="p">.</span><span class="na">newSingleThreadExecutor</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>
+<p>使用<code>Executors.newFixedThreadPool(int)</code>创建一个定长线程池，可控制线程最大并发数，超出的线程会在队列中等待。
+<code>newFixedThreadPool</code>创建的线程池<code>corePoolSize</code>和<code>maximumPoolSize</code>值是相等的，它使用的<code>LinkedBlockingQueue</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">ExecutorService</span><span class="w"> </span><span class="nf">newFixedThreadPool</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">nThreads</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="n">nThreads</span><span class="p">,</span><span class="w"> </span><span class="n">nThreads</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                  </span><span class="n">0L</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                  </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedBlockingQueue</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Executors</span><span class="p">.</span><span class="na">newFixedThreadPool</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>
+<p>使用<code>Executors.newCachedThreadPool()</code>创建一个可缓存线程池，如果线程池长度超过处理需要，可灵活回收空闲线程，若无可回收则新建线程。
+<code>newCachedThreadPool</code>将<code>corePoolSize</code>设置为0，将<code>maximumPoolSize</code>设置为<code>Integer.MAX_VALUE</code>，使用的 <code>SynchronousQueue</code>，也就是说来了任务就创建线程运行，当线程空闲超过60秒，就销毁线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">ExecutorService</span><span class="w"> </span><span class="nf">newCachedThreadPool</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                  </span><span class="n">60L</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">SECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                  </span><span class="k">new</span><span class="w"> </span><span class="n">SynchronousQueue</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Executors</span><span class="p">.</span><span class="na">newCachedThreadPool</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<h4 id="自定义线程池">自定义线程池</h4>
+<p>在实际开发中用哪个线程池？上面的三种一个都不用，我们生产上只能使用自定义的。<code>Executors</code>类中已经给你提供了，为什么不用？</p>
+<blockquote>
+<p>摘自<a href="https://developer.aliyun.com/topic/download?spm=a2c6h.15028928.J_5293118740.2&id=805">《阿里巴巴开发手册》</a>
+【强制】线程资源必须通过线程池提供，不允许在应用中自行显式创建线程。
+说明：线程池的好处是减少在创建和销毁线程上所消耗的时间以及系统资源的开销，解决资源不足的问题。 如果不使用线程池，有可能造成系统创建大量同类线程而导致消耗完内存或者“过度切换”的问题。<br>
+【强制】线程池不允许使用 <code>Executors</code> 去创建，而是通过 <code>ThreadPoolExecutor</code> 的方式，这样的处理方式让写的同学更加明确线程池的运行规则，规避资源耗尽的风险。
+说明：<code>Executors</code> 返回的线程池对象的弊端如下：
+1） <code>FixedThreadPool</code> 和 <code>SingleThreadPool</code>： 允许的请求队列长度为 <code>Integer.MAX_VALUE</code>，可能会堆积大量的请求，从而导致OOM。
+2） <code>CachedThreadPool</code>： 允许的创建线程数量为 <code>Integer.MAX_VALUE</code>，可能会创建大量的线程，从而导致 OOM。</p>
+</blockquote>
+<p>自定义线程池代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">2</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">5</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">1L</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">SECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedBlockingQueue</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">3</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Executors</span><span class="p">.</span><span class="na">defaultThreadFactory</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>SpringBoot异步配置，自定义线程池代码演示：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@EnableAsync</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AsyncConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 线程空闲存活的时间 单位: TimeUnit.SECONDS
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">KEEP_ALIVE_TIME</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">60</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">60</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * CPU 核心数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CPU_COUNT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Runtime</span><span class="p">.</span><span class="na">getRuntime</span><span class="p">().</span><span class="na">availableProcessors</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 核心线程数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CORE_POOL_SIZE</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">CPU_COUNT</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 线程池最大容纳线程数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * IO密集型:即存在大量堵塞; 公式: CPU核心数量 / 1- 阻塞系数 (阻塞系统在 0.8~0.9 之间)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * CPU密集型: 需要大量运算,没有堵塞或很少有; 公式:CPU核心数量 + 1
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">IO_MAXIMUM_POOL_SIZE</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">CPU_COUNT</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="n">1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">9</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CPU_MAXIMUM_POOL_SIZE</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CPU_COUNT</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行写入请求时的线程池
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 线程池
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;iSaveTaskThreadPool&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Executor</span><span class="w"> </span><span class="nf">iSaveTaskThreadPool</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">getThreadPoolTaskExecutor</span><span class="p">(</span><span class="s">&#34;iSaveTaskThreadPool-&#34;</span><span class="p">,</span><span class="n">IO_MAXIMUM_POOL_SIZE</span><span class="p">,</span><span class="n">100000</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行读请求时的线程池
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 线程池
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;iQueryThreadPool&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Executor</span><span class="w"> </span><span class="nf">iQueryThreadPool</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">getThreadPoolTaskExecutor</span><span class="p">(</span><span class="s">&#34;iQueryThreadPool-&#34;</span><span class="p">,</span><span class="n">CPU_MAXIMUM_POOL_SIZE</span><span class="p">,</span><span class="n">10000</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 创建一个线程池对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param threadNamePrefix 线程名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param queueCapacity 堵塞队列长度
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param refusePolicy 拒绝策略
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ThreadPoolTaskExecutor</span><span class="w"> </span><span class="nf">getThreadPoolTaskExecutor</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">threadNamePrefix</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">maxPoolSize</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">queueCapacity</span><span class="p">,</span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="w"> </span><span class="n">refusePolicy</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ThreadPoolTaskExecutor</span><span class="w"> </span><span class="n">taskExecutor</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolTaskExecutor</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setCorePoolSize</span><span class="p">(</span><span class="n">CORE_POOL_SIZE</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setMaxPoolSize</span><span class="p">(</span><span class="n">maxPoolSize</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setKeepAliveSeconds</span><span class="p">(</span><span class="n">KEEP_ALIVE_TIME</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setThreadNamePrefix</span><span class="p">(</span><span class="n">threadNamePrefix</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 拒绝策略; 既不会抛弃任务,也不会抛出异常,而是将某些任务回退到调用者,从而降低新任务的流量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setRejectedExecutionHandler</span><span class="p">(</span><span class="n">refusePolicy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 阻塞队列 长度</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setQueueCapacity</span><span class="p">(</span><span class="n">queueCapacity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setWaitForTasksToCompleteOnShutdown</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">setAwaitTerminationSeconds</span><span class="p">(</span><span class="n">60</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">taskExecutor</span><span class="p">.</span><span class="na">initialize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">taskExecutor</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="线程池工作原理">线程池工作原理</h4>
+<p><img alt="线程池工作原理" src="/iblog/posts/annex/images/essays/%E7%BA%BF%E7%A8%8B%E6%B1%A0%E5%B7%A5%E4%BD%9C%E5%8E%9F%E7%90%86.png"></p>
+<p>在创建了线程池后，等待提交过来的任务请求，当调用<code>execute</code>方法添加一个请求任务时，线程池会做如下判断：</p>
+<ol>
+<li>如果当前运行的线程数小于<code>corePoolSize</code>，那么马上创建线程运行该任务。</li>
+<li>如果当前运行的线程数大于等于<code>corePoolSize</code>，那么该任务会被放入任务队列。</li>
+<li>如果这时候任务队列满了且正在运行的线程数还小于<code>maximumPoolSize</code>，那么要创建非核心线程立刻运行这个任务扩容。</li>
+<li>如果任务队列满了且正在运行的线程数等于<code>maximumPoolSize</code>，那么线程池会启动饱和拒绝策略来执行。</li>
+<li>随着时间的推移，业务量越来越少，线程池中出现了空闲线程。当一个线程无事可做超过一定的时间时，线程池会进行判断，如果当前运行的线程数大于<code>corePoolSize</code>，那么这个线程就被停掉，所以线程池的所有任务完成后它最终会收缩到<code>corePoolSize</code>的大小。</li>
+</ol>
+<h4 id="阻塞队列">阻塞队列</h4>
+<p>阻塞队列，顾名思义，首先它是一个队列，一个阻塞队列在数据结构中所起的作用：</p>
+<ul>
+<li>当阻塞队列是空时，从队列中获取元素的操作将会被阻塞。</li>
+<li>当阻塞队列是满时，往队列里添加元素的操作将会被阻塞。</li>
+</ul>
+<p><img alt="阻塞队列" src="/iblog/posts/annex/images/essays/%E9%98%BB%E5%A1%9E%E9%98%9F%E5%88%97%E7%BB%93%E6%9E%84.jpeg"></p>
+<p>在多线程编程中，阻塞队列扮演着重要角色，特别适用于生产者-消费者模式，确保线程之间的同步和有序执行。阻塞队列的本质是一种数据结构，用于存储待执行的任务。
+当任务提交给线程池时，如果核心线程已满或任务队列达到容量上限，新任务将被放入阻塞队列中，等待执行条件的满足。</p>
+<p>阻塞在多线程领域指的是线程因某些条件而暂停执行，一旦条件满足，线程会被自动唤醒继续执行。这种机制保证了线程池的任务按照预期顺序执行，有效地管理并发任务的执行流程。</p>
+<p>在Java中，常见的线程池阻塞队列包括：</p>
+<ul>
+<li><code>ArrayBlockingQueue</code>: 由数组结构组成的有界阻塞队列。它按照 FIFO（先进先出）的顺序对元素进行排序。</li>
+<li><code>LinkedBlockingQueue</code>: 由链表结构组成的有界（默认大小为 <code>Integer.MAX_VALUE</code>，大约21亿）阻塞队列。同样按照 FIFO 的顺序对元素进行排序。</li>
+<li><code>PriorityBlockingQueue</code>: 支持优先级排序的无界阻塞队列。元素按照它们的优先级顺序被处理，具有最高优先级的元素总是被队列中的下一个要处理的元素。</li>
+<li><code>DelayQueue</code>: 使用优先级队列实现的延迟无界阻塞队列。队列中的元素只有在其指定的延迟时间到达时才能被取出。</li>
+<li><code>SynchronousQueue</code>: 不存储元素的阻塞队列，每个插入操作必须等待一个对应的移除操作。用于直接传递任务的场景。</li>
+<li><code>LinkedTransferQueue</code>: 由链表结构组成的无界阻塞队列，支持生产者-消费者的传输机制。与其他队列不同，它支持优先级传输。</li>
+<li><code>LinkedBlockingDeque</code>: 由链表结构组成的双向阻塞队列。它支持在队列的两端进行插入和移除操作，是一种双端队列。</li>
+</ul>
+<p>当你自定义线程池时，选择合适的阻塞队列是非常重要的。阻塞队列就像一个存放任务的“箱子”，线程池中的任务先放到这里，然后线程池的线程再从这里取出来执行。
+如果你的系统可能会有很多任务一起提交，可以考虑用能存很多任务的队列，比如<code>LinkedBlockingQueue</code>。这样即使任务多了，也不会丢失。
+如果你的任务有优先级，比如有些任务比其他的更重要，那就选<code>PriorityBlockingQueue</code>。它会按照任务的优先级来决定哪个任务先执行。
+如果应用程序需要限制内存使用，并希望在达到容量限制时阻塞新任务提交，可以选择<code>ArrayBlockingQueue</code>。</p>
+<h4 id="线程池参数">线程池参数</h4>
+<p>在Java中，线程池的创建和管理通过<code>java.util.concurrent.ThreadPoolExecutor</code>类完成。理解这个类构造函数的参数可以帮助我们更好地配置和优化线程池的运行效果。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="nf">ThreadPoolExecutor</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">corePoolSize</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="kt">int</span><span class="w"> </span><span class="n">maximumPoolSize</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="kt">long</span><span class="w"> </span><span class="n">keepAliveTime</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="n">TimeUnit</span><span class="w"> </span><span class="n">unit</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="n">BlockingQueue</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">workQueue</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="n">ThreadFactory</span><span class="w"> </span><span class="n">threadFactory</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                          </span><span class="n">RejectedExecutionHandler</span><span class="w"> </span><span class="n">handler</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><ul>
+<li><code>corePoolSize</code>: 核心线程数。当提交一个新任务时，如果当前运行的线程少于<code>corePoolSize</code>，则即使有空闲的工作线程，也会创建一个新线程来执行任务。
+核心线程在<code>ThreadPoolExecutor</code>的生命周期内始终存活，除非设置了<code>allowCoreThreadTimeOut</code>。</li>
+<li><code>maximumPoolSize</code>：线程池能够容纳同时执行的最大线程数，此值必须大于等于1。当任务队列满时，如果当前运行的线程数少于<code>maximumPoolSize</code>，则会创建新的线程来执行任务。</li>
+<li><code>threadFactory</code>：线程工厂，一般用默认的即可。用于创建新线程，通常用来给线程设置名称、设置为守护线程等。</li>
+<li><code>workQueue</code>：任务队列，用于保存等待执行任务的队列。随着业务量的增多，线程开始慢慢处理不过来，这时候需要放到任务队列中去等待线程处理。</li>
+<li><code>rejectedExecutionHandler</code>：拒绝策略。如果业务越来越多，线程池首先会扩容，扩容后发现还是处理不过来，任务队列已经满了，处理被拒绝任务的策略。
+<ol>
+<li><code>AbortPolicy</code>: 默认拒绝策略；直接抛出<code>java.util.concurrent.RejectedExecutionException</code>异常，阻止系统的正常运行；</li>
+<li><code>CallerRunsPolicy</code>：调用这运行，一种调节机制，该策略既不会抛弃任务，也不会抛出异常，而是将某些任务回退到调用者，从而降低新任务的流量；</li>
+<li><code>DiscardOldestPolicy</code>：抛弃队列中等待最久的任务，然后把当前任务加入到队列中；</li>
+<li><code>DiscardPolicy</code>：直接丢弃任务，不给予任何处理也不会抛出异常；如果允许任务丢失，这是一种最好的解决方案；</li>
+</ol>
+</li>
+<li><code>keepAliveTime</code>：多余的空闲线程的存活时间。如果线程池扩容后，能处理过来，而且数据量并没有那么大，用最初的线程数量就能处理过来，剩下的线程被叫做空闲线程。
+<code>keepAliveTime</code>指的是当线程数超过<code>corePoolSize</code>时，多余的空闲线程在等待新任务到来之前可以存活的最长时间。如果设置为0，则超出核心线程数的空闲线程会立即终止。</li>
+<li><code>unit</code>：<code>keepAliveTime</code>参数的时间单位，可以是<code>TimeUnit.SECONDS</code>、<code>TimeUnit.MILLISECONDS</code>等。</li>
+</ul>
+<h4 id="合理配置线程池参数">合理配置线程池参数</h4>
+<p>合理配置线程池参数，可以分为以下两种情况：</p>
+<ul>
+<li>CPU密集型：CPU密集的意思是该任务需要大量的运算，而没有阻塞，CPU一直全速运行；CPU密集型任务配置尽可能少的线程数量：<code>参考公式：（CPU核数+1）</code></li>
+<li>IO密集型：即该任务需要大量的IO，即大量的阻塞；在IO密集型任务中使用多线程可以大大的加速程序运行，故需要多配置线程数：参考公式：<code>CPU核数/ (1-阻塞系数) 阻塞系数在0.8~0.9之间</code></li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ExecutorService</span><span class="w"> </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取CPU核心数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">coreNum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Runtime</span><span class="p">.</span><span class="na">getRuntime</span><span class="p">().</span><span class="na">availableProcessors</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="cm">/*
+</span></span></span><span class="line"><span class="cl"><span class="cm">             * 1. IO密集型: CPU核数/ (1-阻塞系数) 阻塞系数在0.8~0.9之间
+</span></span></span><span class="line"><span class="cl"><span class="cm">             * 2. CPU密集型: CPU核数+1
+</span></span></span><span class="line"><span class="cl"><span class="cm">             */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//            int maximumPoolSize = coreNum + 1;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">maximumPoolSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">coreNum</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="n">1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">9</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前线程池最大允许存放：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">maximumPoolSize</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;个线程&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">2</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">maximumPoolSize</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">1L</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">SECONDS</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedBlockingQueue</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">3</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Executors</span><span class="p">.</span><span class="na">defaultThreadFactory</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadPoolExecutor</span><span class="p">.</span><span class="na">CallerRunsPolicy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">executor1</span><span class="p">.</span><span class="na">execute</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;执行了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">executor1</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="锁">锁</h2>
+<p>在Java中根据锁的特性来划分可以分为很多，锁的主要作用是确保多线程环境下的数据安全，从而保证程序的正确执行。
+在Java中具体&quot;锁&quot;的实现，通常可以归纳为三种，使用<code>synchronized</code>关键字、调用<code>juc.locks</code>包下相关接口、使用<code>CAS</code>思想。</p>
+<table>
+<thead>
+<tr>
+<th>锁的类型与概念</th>
+<th>描述</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>公平锁</td>
+<td>线程按照请求的顺序获取锁。</td>
+</tr>
+<tr>
+<td>非公平锁</td>
+<td>线程获取锁的顺序不受控制，有可能插队。</td>
+</tr>
+<tr>
+<td>可重入锁</td>
+<td>允许同一个线程多次获取同一把锁，避免死锁。</td>
+</tr>
+<tr>
+<td>不可重入锁</td>
+<td>不允许同一个线程多次获取同一把锁。</td>
+</tr>
+<tr>
+<td>共享锁</td>
+<td>多个线程可以同时获取同一把锁。</td>
+</tr>
+<tr>
+<td>独占锁</td>
+<td>同一时间只允许一个线程获取该锁。</td>
+</tr>
+<tr>
+<td>悲观锁</td>
+<td>假设会有并发冲突，每次操作时都加锁。</td>
+</tr>
+<tr>
+<td>乐观锁</td>
+<td>假设不会有并发冲突，操作时不加锁，提交时检查是否冲突。</td>
+</tr>
+<tr>
+<td>偏向锁</td>
+<td>当只有一个线程访问同步块时，为该线程加锁，减少获取锁的操作成本。</td>
+</tr>
+<tr>
+<td>轻量级锁</td>
+<td>针对竞争不激烈的情况下进行优化，通过CAS操作来避免互斥。</td>
+</tr>
+<tr>
+<td>重量级锁</td>
+<td>竞争激烈时，锁的持有和释放会导致线程阻塞和唤醒。</td>
+</tr>
+<tr>
+<td>可中断锁</td>
+<td>允许在等待锁的过程中可以响应中断信号。</td>
+</tr>
+<tr>
+<td>互斥锁</td>
+<td>控制对共享资源的访问，同一时间只有一个线程可以获取锁。</td>
+</tr>
+<tr>
+<td>死锁</td>
+<td>几个线程因互相持有对方所需的资源而无法继续执行的状态。</td>
+</tr>
+</tbody>
+</table>
+<h3 id="公平锁与非公平锁">公平锁与非公平锁</h3>
+<p>根据线程获取锁的顺序来划分可分为公平锁和非公平锁。</p>
+<ul>
+<li>公平锁：公平锁是指多个线程按照申请锁的顺序来获取锁。即先到先得的原则，先请求锁的线程会先获取到锁，后到的线程会排队等待。
+优点是等待锁的线程不会饿死。缺点是整体吞吐效率相对非公平锁要低，等待队列中除第一个线程以外的所有线程都会阻塞，CPU唤醒阻塞线程的开销比非公平锁大。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">fairLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w"> </span><span class="c1">// true 表示使用公平锁</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>非公平锁：非公平锁是指多个线程获取锁的顺序是不确定的，是随机竞争的。即线程获取锁的顺序是不固定的，有可能新来的线程比等待时间长的线程先获取到锁。
+优点是可以通过减少线程切换的开销来提高并发性能，整体的吞吐效率高。缺点是处于等待队列中的线程可能会饿死，或者等很久才会获得锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">nonfairLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w"> </span><span class="c1">// false 表示使用非公平锁（默认）</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>通常情况下，如果不特别需要公平性，非公平锁能够提供更高的性能。但是在某些需要严格控制线程执行顺序的场景下，公平锁可能更为适合。
+在Java中公平锁和非公平锁的实现为<code>ReentrantLock</code>、<code>synchronized</code>。
+其中<code>synchronized</code>是非公平锁，<code>ReentrantLock</code>默认是非公平锁，但是可以指定<code>ReentrantLock</code>的构造函数创建公平锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an instance of {@code ReentrantLock}.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * This is equivalent to using {@code ReentrantLock(false)}.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">ReentrantLock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sync</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NonfairSync</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an instance of {@code ReentrantLock} with the
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * given fairness policy.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @param fair {@code true} if this lock should use a fair ordering policy
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">ReentrantLock</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">fair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sync</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fair</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FairSync</span><span class="p">()</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NonfairSync</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="可重入锁与不可重入锁">可重入锁与不可重入锁</h3>
+<p>根据一个线程是否可以多次获得同一把锁来划分，可分为可重入锁和不可重入锁。</p>
+<ul>
+<li>可重入锁：可重入锁是指同一个线程在外层方法获取锁之后，在内层方法仍然能够获取该锁的锁。即同一个线程可以多次获得同一把锁，可重入锁最大的作用就是避免死锁。所以可重入锁又叫做递归锁。</li>
+<li>不可重入锁：所谓不可重入锁，就是与可冲入锁作用相悖；不可重入锁是指一个线程在持有锁的情况下再次请求锁时，会被阻塞或导致死锁。即同一个线程不能多次获得同一把锁。</li>
+</ul>
+<p>举个例子，当你进入你家时门外会有锁，进入房间后厨房卫生间都可以随便进出，这个叫可重入锁。当你进入房间时，发现厨房、卫生间都上锁而且你拿不到钥匙，这个叫不可重入锁。
+在Java中<code>ReentrantLock</code>和<code>synchronized</code>都是可重入锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReentrantExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">outerMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Outer method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">innerMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">innerMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Inner method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReentrantExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">example</span><span class="p">.</span><span class="na">outerMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReentrantLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">outerMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Outer method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">innerMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">innerMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Inner method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReentrantLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">example</span><span class="p">.</span><span class="na">outerMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="共享锁与独占锁">共享锁与独占锁</h3>
+<p>根据锁的访问权限可划分为共享锁和独占锁。</p>
+<ul>
+<li>独占锁：独占锁又称排它锁，指一次只能有一个线程获得锁，其他所有尝试获取锁的线程都会被阻塞，直到持有锁的线程释放锁。
+只有一个线程能访问受保护的资源，从而确保资源的独占访问，适用于写操作等需要完全独占资源的场景。</li>
+<li>共享锁：共享锁允许多个线程同时获得锁，多个线程可以并发地访问受保护的资源。适用于读操作等可以并发访问的场景。
+多个线程可以同时持有锁，但如果某个线程需要进行写操作，则必须等到所有持有共享锁的线程释放锁。</li>
+</ul>
+<p>在Java中，对于<code>ReentrantLock</code>和<code>synchronized</code>都是独占锁。对于<code>ReentrantReadWriteLock</code>其读锁是共享锁而写锁是独占锁，读锁的共享可保证并发读是非常高效的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SharedLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="w"> </span><span class="n">rwLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="p">.</span><span class="na">ReadLock</span><span class="w"> </span><span class="n">readLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rwLock</span><span class="p">.</span><span class="na">readLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="p">.</span><span class="na">WriteLock</span><span class="w"> </span><span class="n">writeLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rwLock</span><span class="p">.</span><span class="na">writeLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">readMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">readLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the read lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// Read-only critical section</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">readLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; released the read lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">writeLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the write lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// Write critical section</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; released the write lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SharedLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SharedLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">readTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">readMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">writeTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">3</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">writeMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">t1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">readTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">t2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">readTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">t3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">writeTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">t1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">t2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">t3</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="悲观锁与乐观锁">悲观锁与乐观锁</h3>
+<p>根据对数据并发访问来划分，可分为悲观锁和乐观锁。乐观锁与悲观锁是一种广义上的概念，可以理解为一种标准类似于Java中的接口。</p>
+<ul>
+<li>对于多线程并发操作，加了悲观锁的线程认为每一次修改数据时都会有其他线程来跟它一起修改数据，所以在修改数据之前先会加锁，确保其他线程不会修改该数据。
+由于悲观锁在修改数据前先加锁的特性，能保证写操作时数据正确，所以悲观锁更适合写多读少的场景。</li>
+<li>乐观锁则与悲观锁相反，每一次修改数据时，都认为没有其他线程来跟它一起修改，所以在修改数据之前不会去添加锁，如果这个数据没有被更新，当前线程将自己修改的数据成功写入。如果数据已经被其他线程更新，则根据不同的实现方式执行不同的操作。
+由于乐观锁是一种无锁操作，所以在使用乐观锁的场景中读的性能会大幅度提升，适合读多写少。</li>
+</ul>
+<p>在Java中悲观锁的实现有，<code>synchronized</code>、<code>Lock</code>实现类，乐观锁的实现有<code>CAS</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SynchronizedExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SynchronizedExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SynchronizedExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Count: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">example</span><span class="p">.</span><span class="na">getCount</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">existingValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">count</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">existingValue</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">count</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">existingValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">count</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CASExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CASExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Count: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">example</span><span class="p">.</span><span class="na">getCount</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="自旋锁与适应性自旋锁">自旋锁与适应性自旋锁</h3>
+<p>自旋锁是一种特殊的锁，它不会让线程立即阻塞。
+当一个线程尝试获取某个锁时，如果该锁已被其他线程占用，就一直循环检测锁是否被释放，而不是进入线程挂起或睡眠状态，直到获取到某个锁超过一定的自旋次数后才会阻塞线程。
+自旋锁本身是有缺点的，它不能代替阻塞。如果锁被占用的时间很长，那么自旋的线程只会白白浪费处理器资源，带来性能上的浪费，所以使用自旋锁时需要根据具体的应用场景来权衡其利弊。</p>
+<p>在Java中，可以使用<code>java.util.concurrent.atomic</code>包下的原子类来实现自旋锁，其中<code>AtomicInteger</code>常被用来实现简单的自旋锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SpinLock</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">lock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 自旋等待获取锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">locked</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取到锁后，将 locked 设置为 true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unlock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 释放锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SpinLock</span><span class="w"> </span><span class="n">spinLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SpinLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">spinLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread 1 in critical section&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟临界区代码执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spinLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">spinLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread 2 in critical section&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟临界区代码执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spinLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为什么要使用自旋锁？在许多场景中，同步资源的锁定时间很短，为了这一小段时间去切换线程，线程挂起和恢复现场的花费可能会让系统得不偿失。
+简单来说就是，避免切换线程带来的开销。自旋等待虽然避免了线程切换的开销，但它要占用处理器时间。如果锁被占用的时间很短，自旋等待的效果就会非常好。
+反之，如果锁被占用的时间很长，那么自旋的线程只会白浪费处理器资源。所以自旋等待的时间必须要有一定的限度，如果自旋超过了限定次数（默认是10次，可以使用<code>-XX:PreBlockSpin</code>来更改）没有成功获得锁，就应当挂起线程。</p>
+<blockquote>
+<p>自旋锁在JDK 1.4中引入，默认关闭，但是可以使用<code>-XX:+UseSpinning</code>开启。在JDK1.6中默认开启，同时自旋的默认次数为10次，可以通过参数<code>-XX:PreBlockSpin</code>来调整。</p>
+</blockquote>
+<p>如果通过参数<code>-XX:PreBlockSpin</code>来调整自旋锁的自旋次数会带来诸多不便。假如将参数调整为10，但是系统很多线程都是等你刚刚退出的时候就释放了锁，假如多自旋一两次就可以获取锁。于是JDK1.6引入适应性自旋锁。</p>
+<p>适应性自旋锁是对自旋的升级、优化，自旋的时间不再固定，它根据当前锁的使用情况动态调整自旋等待时间。
+如果在同一个锁对象上，自旋等待刚刚成功获得过锁，并且持有锁的线程正在运行中，那么虚拟机就会认为这次自旋也是很有可能再次成功，进而它将允许自旋等待持续相对更长的时间。
+如果对于某个锁，自旋很少成功获得过，那在以后尝试获取这个锁时将可能省略掉自旋过程，直接阻塞线程，避免浪费处理器资源。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AdaptiveSpinLock</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">MIN_SPIN_COUNT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">MAX_SPIN_COUNT</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AtomicBoolean</span><span class="w"> </span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicBoolean</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">spinCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MIN_SPIN_COUNT</span><span class="p">;</span><span class="w"> </span><span class="c1">// 初始自旋等待次数设定为最小值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">lock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">spins</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">spinCount</span><span class="p">;</span><span class="w"> </span><span class="c1">// 获取当前自旋次数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">locked</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">false</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">spins</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAX_SPIN_COUNT</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spins</span><span class="o">++</span><span class="p">;</span><span class="w"> </span><span class="c1">// 自旋次数递增</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 在真实场景中，可能需要添加短暂的延时，避免过多占用CPU资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">spins</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">onSpinWait</span><span class="p">();</span><span class="w"> </span><span class="c1">// 在Java 9及以上版本中，可以使用Thread.onSpinWait()来优化自旋等待</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">spinCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">spins</span><span class="p">;</span><span class="w"> </span><span class="c1">// 更新自旋次数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unlock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">locked</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AdaptiveSpinLock</span><span class="w"> </span><span class="n">spinLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AdaptiveSpinLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">spinLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread 1 in critical section&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟临界区代码执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spinLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">spinLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread 2 in critical section&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟临界区代码执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">spinLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="偏向锁">偏向锁</h3>
+<p>偏向锁是Java中针对加锁操作进行的一种优化机制，主要针对只有一个线程访问同步块的场景。它的设计初衷是在无竞争的情况下，减少不必要的同步原语的性能消耗。</p>
+<blockquote>
+<p>《深入理解Java虚拟机》对偏向锁的解释：
+<code>Hotspot</code> 的作者经过以往的研究发现大多数情况下锁不仅不存在多线程竞争，而且总是由同一线程多次获得，为了让线程获得锁的代价更低而引入了偏向锁。
+当一个线程访问同步块并获取锁时，会在对象头和栈帧中的锁记录里存储锁偏向的线程 ID，以后该线程在进入和退出同步块时不需要花费CAS操作来加锁和解锁，而只需简单的测试一下对象头的 <code>MarkWord</code> 里是否存储着指向当前线程的偏向锁，如果测试成功，表示线程已经获得了锁，如果测试失败，则需要再测试下 <code>MarkWord</code> 中偏向锁的标识是否设置成 1（表示当前是偏向锁），如果没有设置，则使用 CAS 竞争锁，如果设置了，则尝试使用CAS将对象头的偏向锁指向当前线程。</p>
+</blockquote>
+<p>之所以叫偏向锁是因为偏向于第一个获取到他的线程，如果在程序执行中该锁没有被其他的线程获取，则持有偏向锁的线程将永远不需要再进行同步。
+但是如果线程间存在锁竞争，偏向锁会失效，此时会涉及到锁的撤销，将锁状态升级为适合多线程竞争的轻量级锁或者重量级锁，这个过程可能会引入额外的开销，影响性能。</p>
+<p>当一个线程访问同步块时，首先会尝试获取偏向锁。如果同步块之前没有被其他线程锁定，当前线程会尝试获取偏向锁，并将对象头的标记位设置为偏向锁。
+如果其他线程尝试访问该同步块，会检测到该同步块已经被偏向锁定，会尝试撤销偏向锁，升级为轻量级锁或者重量级锁。
+如果偏向线程已经不再访问该同步块，那么该对象头的标记位会被设置成无锁状态，接着是无锁状态。</p>
+<h3 id="轻量级锁与重量级锁">轻量级锁与重量级锁</h3>
+<p>根据锁的竞争情况来划分可以分为重量级锁和轻量级锁。</p>
+<ul>
+<li>重量级锁：重量级锁适用于多线程竞争激烈的情况下，它的实现通常依赖于操作系统的底层特性，重量级锁会导致线程堵塞。传统的重量级锁，使用的是系统互斥量实现的。</li>
+<li>轻量级锁：相对于重量级锁而言的。轻量级锁适用于多线程竞争不激烈的情况下，它的设计目标是在减少传统重量级锁在竞争时带来的性能损耗。</li>
+</ul>
+<p>在Java中轻量级锁的经典实现是CAS中的自旋锁。优点是竞争的线程不会阻塞，提高了程序的响应速度；缺点是如果始终得不到锁竞争的线程，使用自旋会消耗CPU。所以轻量级锁适合，追求响应时间，同步块执行速度非常快的场景。
+重量级锁依赖于操作系统提供的底层同步机制。优点是线程竞争不使用自旋，不会消耗CPU；缺点是当多个线程竞争同一个锁时，会直接阻塞等待，直到获取到锁的线程释放锁资源。适合追求吞吐量、同步块执行时间较长也就是线程竞争激烈的场景。</p>
+<p>轻量级锁不是在任何情况下都比重量级锁快的，要看同步块执行期间有没有多个线程抢占资源的情况。如果有，那么轻量级线程要承担CAS+互斥锁的性能消耗，就会比重量锁执行的更慢。</p>
+<h3 id="可中断锁">可中断锁</h3>
+<p>可中断锁顾名思义，就是可以中断的锁。
+如果某一线程A正在执行锁中的代码，另一线程B正在等待获取该锁，可能由于等待时间过长，线程B不想等待了，想先处理其他事情，我们可以让它中断自己或者在别的线程中中断它，这种就是可中断锁。</p>
+<p>在Java中<code>synchronized</code>就是不可中断锁，<code>Lock</code>是可中断锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SynchronizedExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">5000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟线程持有锁的操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;Thread-1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;Thread-2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 让Thread-1先获取锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 等待线程执行完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">LockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">5000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟线程持有锁的操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;Thread-1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">.</span><span class="na">tryLock</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// 可中断地尝试获取锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; unable to acquire the lock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;Thread-2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// 让Thread-1先获取锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 等待线程执行完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="互斥锁">互斥锁</h3>
+<p>互斥锁是一种用于多线程编程中的同步原语，用于确保在任何时刻，只有一个线程可以访问共享资源，从而避免数据竞争和并发访问的冲突。
+在编程中，引入了对象互斥锁的概念，来保证共享数据操作的完整性。每个对象都对应于一个可称为&quot;互斥锁&quot;的标记，这个标记用来保证在任一时刻，只能有一个线程访问该对象。</p>
+<p>互斥锁在访问共享资源之前对对象进行加锁操作，在访问完成之后进行解锁操作。加锁后，任何其他试图再次加锁的线程会被阻塞，直到当前线程解锁其他线程才能访问公共资源。
+如果在解锁时有多个线程在等待获取锁，一旦锁被释放，它们将竞争重新获取锁。只有第一个竞争到锁的线程会变为就绪状态并开始执行，其他线程将继续等待。</p>
+<p>在Java里最基本的互斥手段就是使用<code>synchronized</code>关键字、<code>ReentrantLock</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SynchronizedMutexExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Counter: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="死锁">死锁</h3>
+<p>死锁并不是Java程序中通俗意义上的&quot;锁&quot;，而是程序中出现的一种问题。之所以放到“锁”这个标题下是为了方便类比，就类似谐音梗吧。</p>
+<p>死锁是指两个或多个线程在执行过程中，由于竞争资源或者互相等待释放资源而造成的一种僵局，使得所有参与的线程无法继续执行。
+举个例子，当线程A持有锁a并尝试获取锁b，线程B持有锁b并尝试获取锁a时，就会出现死锁。简单来说，死锁问题的产生是由两个或者以上线程并行执行的时候，争夺资源而互相等待造成的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;lockA&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;lockB&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadHolderLock</span><span class="p">(</span><span class="n">lockA</span><span class="p">,</span><span class="n">lockB</span><span class="p">),</span><span class="s">&#34;线程AAA&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ThreadHolderLock</span><span class="p">(</span><span class="n">lockB</span><span class="p">,</span><span class="n">lockA</span><span class="p">),</span><span class="s">&#34;线程BBB&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="kd">class</span> <span class="nc">ThreadHolderLock</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Runnable</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">public</span><span class="w"> </span><span class="nf">ThreadHolderLock</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">lockA</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">lockB</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">this</span><span class="p">.</span><span class="na">lockA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lockA</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">this</span><span class="p">.</span><span class="na">lockB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lockB</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lockA</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 持有锁 &#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockA</span><span class="o">+</span><span class="s">&#34;, 尝试获得&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockB</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                 </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                 </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lockB</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                 </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 持有锁 &#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockB</span><span class="o">+</span><span class="s">&#34;, 尝试获得&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">lockA</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">             </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用资源有序分配法避免死锁">使用资源有序分配法避免死锁</h4>
+<p>想要如何避免死锁，就要弄清楚死锁出现的原因，造成死锁必须达成的4个条件：</p>
+<ul>
+<li>互斥条件：一个资源每次只能被一个线程使用。例如，如果线程 A 已经持有的资源，不能再同时被线程 B 持有，如果线程 B 请求获取线程 A 已经占用的资源，那线程 B 只能等待，直到线程 A 释放了资源。</li>
+<li>请求与保持条件：一个线程因请求资源而阻塞时，对已获得的资源保持不放。例如，当线程 A 已经持有了资源 1，又想申请资源 2，而资源 2 已经被线程 C 持有了，所以线程 A 就会处于等待状态，但是线程 A 在等待资源 2 的同时并不会释放自己已经持有的资源 1。</li>
+<li>不剥夺条件：线程已获得的资源，在未使用完之前，不能强行剥夺。例如，当线程A已经持有了资源 ，在自己使用完之前不能被其他线程获取，线程 B 如果也想使用此资源，则只能在线程 A 使用完并释放后才能获取。</li>
+<li>循环等待条件：若干线程之间形成一种头尾相接的循环等待资源关系。比如，线程 A 已经持有资源 2，而想请求资源 1， 线程 B 已经获取了资源 1，而想请求资源 2，这就形成资源请求等待的环。</li>
+</ul>
+<p>避免死锁的产生就只需要破环其中一个条件就可以，最常见的并且可行的就是使用资源有序分配法，来破循环等待条件。
+资源有序分配法指的是，线程 A 和 线程 B 获取资源的顺序要一样，当线程 A 先尝试获取资源 A，然后尝试获取资源 B 的时候，线程 B 同样也是先尝试获取资源 A，然后尝试获取资源 B。也就是说，线程 A 和 线程 B 总是以相同的顺序申请自己想要的资源。
+给资源分配一个全局的唯一编号，进程必须按资源编号的顺序请求资源。这种方法可以避免循环等待，从而防止死锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Resource</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Resource</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Process</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="w"> </span><span class="n">resources</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Process</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">resources</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">resources</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquireResources</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 模拟处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">releaseResources</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">acquireResources</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Resource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired Resource &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">resource</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">releaseResources</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Resource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">resources</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; released Resource &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">resource</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ResourceOrderingExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Resource</span><span class="w"> </span><span class="n">resource3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource1</span><span class="p">,</span><span class="w"> </span><span class="n">resource2</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource2</span><span class="p">,</span><span class="w"> </span><span class="n">resource3</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Resource</span><span class="o">[]</span><span class="p">{</span><span class="n">resource3</span><span class="p">,</span><span class="w"> </span><span class="n">resource1</span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process3</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用银行家算法避免死锁">使用银行家算法避免死锁</h4>
+<p><img alt="银行家算法" src="/iblog/posts/annex/images/essays/%E9%93%B6%E8%A1%8C%E5%AE%B6%E7%AE%97%E6%B3%95.png"></p>
+<p>银行家算法：一个避免死锁的著名算法，是由艾兹格·迪杰斯特拉在1965年为T.H.E系统设计的一种避免死锁产生的算法。它以银行借贷系统的分配策略为基础，判断并保证系统的安全运行。</p>
+<p>在银行中，客户申请贷款的数量是有限的，每个客户在第一次申请贷款时要声明完成该项目所需的最大资金量，在满足所有贷款要求时，客户应及时归还。银行家在客户申请的贷款数量不超过自己拥有的最大值时，都应尽量满足客户的需要。通过判断借贷是否安全，然后决定借不借。
+举例，现有公司B、公司A、公司T，想要从银行分别贷款70亿、40亿、50亿，假设银行只有100亿供放贷，如果借不到企业最大需求的钱，钱将不会归还，怎么才能合理的放贷？</p>
+<table>
+<thead>
+<tr>
+<th>公司</th>
+<th>最大需求</th>
+<th>已借走</th>
+<th>最多还借</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>B</td>
+<td>70</td>
+<td>20</td>
+<td>50</td>
+</tr>
+<tr>
+<td>A</td>
+<td>40</td>
+<td>10</td>
+<td>30</td>
+</tr>
+<tr>
+<td>T</td>
+<td>50</td>
+<td>30</td>
+<td>20</td>
+</tr>
+</tbody>
+</table>
+<p>此时公司B、A、T已经从银行借走60亿，银行还剩40亿。此时银行可放贷金额组合：</p>
+<ul>
+<li>借给公司B10亿、公司A10亿、公司T20亿，等待公司T还钱再将10亿借给公司A，等待公司A还钱，再将钱借给公司B；</li>
+<li>借给公司T20亿，等公司T还钱再将钱借给公司A，等待公司A还钱再将钱借给公司B；</li>
+<li>借给公司A10亿，等待公司A还钱再将钱借给公司T，公司T还钱再将钱借给公司B；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Banker</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="p">;</span><span class="w">  </span><span class="c1">// 系统可用资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="p">;</span><span class="w">  </span><span class="c1">// 每个进程的最大资源需求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">allocation</span><span class="p">;</span><span class="w"> </span><span class="c1">// 每个进程当前已分配的资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">need</span><span class="p">;</span><span class="w">      </span><span class="c1">// 每个进程剩余的资源需求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Banker</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">available</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">maximum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">numProcesses</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">numResources</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">allocation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">numProcesses</span><span class="o">][</span><span class="n">numResources</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">need</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">numProcesses</span><span class="o">][</span><span class="n">numResources</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">numProcesses</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">numResources</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">need</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maximum</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// 初始时，Need等于Maximum</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 请求资源的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">requestResources</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">isRequestValid</span><span class="p">(</span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="n">request</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 请求不合法，拒绝请求</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 试探性分配</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">allocation</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 安全性检查</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">safe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">isSafeState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">safe</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 如果不安全，恢复试探性分配前的状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">allocation</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">-=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">safe</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isRequestValid</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">processId</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">request</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">need</span><span class="o">[</span><span class="n">processId</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">request</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">available</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 请求超出需求或可用资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isSafeState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">work</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">available</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="o">[]</span><span class="w"> </span><span class="n">finish</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">boolean</span><span class="o">[</span><span class="n">allocation</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">found</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">allocation</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">finish</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">canProceed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">work</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">need</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">work</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">canProceed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">canProceed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">work</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="n">work</span><span class="o">[</span><span class="n">j</span><span class="o">]</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">allocation</span><span class="o">[</span><span class="n">i</span><span class="o">][</span><span class="n">j</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">finish</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">found</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">found</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">finish</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">f</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// 存在未完成的进程，系统不安全</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w"> </span><span class="c1">// 所有进程都完成，系统安全</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BankerExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">available</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">maximum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">9</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">},</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">{</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Banker</span><span class="w"> </span><span class="n">banker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Banker</span><span class="p">(</span><span class="n">available</span><span class="p">,</span><span class="w"> </span><span class="n">maximum</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">request1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 1 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">4</span><span class="p">,</span><span class="w"> </span><span class="n">request2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 2 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">request3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">granted3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">banker</span><span class="p">.</span><span class="na">requestResources</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">request3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Request 3 granted: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">granted3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="使用trylock进行超时锁定">使用tryLock进行超时锁定</h4>
+<p>使用 <code>java.util.concurrent.locks.ReentrantLock</code> 的 <code>tryLock</code>方法可以尝试获取锁，并设置超时时间，避免长时间等待造成的死锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Process</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Process</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock1</span><span class="p">.</span><span class="na">tryLock</span><span class="p">(</span><span class="n">50</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock2</span><span class="p">.</span><span class="na">tryLock</span><span class="p">(</span><span class="n">50</span><span class="p">,</span><span class="w"> </span><span class="n">TimeUnit</span><span class="p">.</span><span class="na">MILLISECONDS</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Process &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; acquired both locks&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="c1">// 模拟处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">lock2</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">lock1</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 等待一段时间再重试</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">50</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TryLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">lock1</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Process</span><span class="w"> </span><span class="n">process2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Process</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">lock2</span><span class="p">,</span><span class="w"> </span><span class="n">lock1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">process2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="java内存模型">Java内存模型</h2>
+<p><a href="http://www.cs.umd.edu/~pugh/java/memoryModel/jsr133.pdf">Java内存模型</a>，即JMM（Java Memory Model）本身是一种抽象的概念，并不真实存在。
+它定义了Java程序中多线程间如何通过内存进行交互的规则和规范。屏蔽了各种硬件和操作系统的访问差异的，保证了Java程序在各种平台下对内存的访问都能保证效果一致的机制及规范。
+JMM规定了变量的读取和写入如何在主内存和各线程的工作内存之间进行，保证了并发编程的<strong>原子性</strong>、<strong>可见性</strong>及<strong>有序性</strong>。
+内存模型解决并发问题主要采用两种方式，<strong>限制处理器优化</strong>和使用<strong>内存屏障</strong>。</p>
+<p><img alt="Java内存模型" src="/iblog/posts/annex/images/essays/Java%E5%86%85%E5%AD%98%E6%A8%A1%E5%9E%8B.jpg"></p>
+<h3 id="原子性">原子性</h3>
+<p>原子性指的是一个操作或一组操作在执行时不可被中断，即这些操作要么全部完成，要么全部不完成。
+在Java中，为了保证原子性，提供了两个高级的字节码指令 <code>monitorenter</code> 和 <code>monitorexit</code>。对应的就是Java中的关键字 <code>synchronized</code>，在Java中只要被<code>synchronized</code>修饰就能保证原子性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="可见性">可见性</h3>
+<p>可见性指的是一个线程对共享变量的修改，能够及时被其他线程看到。Java提供了<code>volatile</code>关键字和<code>synchronized</code>关键字来保证变量的可见性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SharedData</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setFlag</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">getFlag</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">flag</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="有序性">有序性</h3>
+<p>有序性指的是程序的执行顺序按照代码的顺序执行，编译器和处理器可能会进行优化，但这些优化不会影响单线程的语义。
+在Java中，可以使用<code>synchronized</code>和<code>volatile</code>来保证多线程之间操作的有序性。其中<code>volatile</code> 关键字会禁止编译器指令重排，来保证。
+<code>synchronized</code> 关键字保证同一时刻只允许一条线程操作，而不能禁止指令重排，指令重排并不会影响单线程的顺序，它影响的是多线程并发执行的顺序性，从而保证了有序性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Example</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">write</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">           </span><span class="c1">// 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">     </span><span class="c1">// 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">read</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">      </span><span class="c1">// 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">a</span><span class="p">);</span><span class="w"> </span><span class="c1">// 4</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在多线程环境下，Java语句可能会不按照顺序执行，所以要注意数据的依赖性。计算机在执行程序时，为了提高性能，编译器和处理器常常会做指令重排，一把分为以下两种：</p>
+<ul>
+<li>单线程环境里面确保程序最终执行结果和代码顺序执行的结果一致。处理器在进行重新排序是必须要考虑指令之间的数据依赖；</li>
+<li>多线程环境中线程交替执行，由于编译器优化重排的存在，两个线程使用的变量能否保持一致性是无法确定的，结果无法预测；</li>
+</ul>
+<h3 id="限制处理器优化">限制处理器优化</h3>
+<p>处理器和编译器为了提高执行效率，会对指令进行优化重排序。虽然这种优化不会影响单线程程序的执行结果，但在多线程环境下可能导致意外的行为。
+Java 内存模型通过以下方式限制处理器和编译器的优化：</p>
+<ul>
+<li><code>volatile</code>关键字：声明为<code>volatile</code>的变量会被直接写入主内存，并且在读取时直接从主内存中读取。<code>volatile</code> 禁止了指令重排序，保证了变量的可见性和有序性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>synchronized</code> 关键字：进入同步块时，会触发获取锁的操作，这会刷新线程的工作内存，从主内存中读取最新值；退出同步块时，会触发释放锁的操作，这会将工作内存中的值写回主内存。
+<code>synchronized</code> 也禁止了指令重排序，保证了变量的原子性和可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="内存屏障">内存屏障</h3>
+<p>内存屏障，也称为内存栅栏，是一种用于防止处理器和编译器对内存操作进行重排序的指令。
+内存屏障通过插入特殊的指令来强制某些操作的顺序执行，从而确保多线程环境下的正确性。Java内存模型在底层实现中使用了内存屏障来保证内存操作的有序性和可见性。</p>
+<p>内存屏障主要分为四种类型，在Java中内存屏障被隐式地应用于某些关键字和类中，用来确保线程安全和内存可见性。</p>
+<ol>
+<li><code>LoadLoad</code>屏障：确保在该屏障之前的所有 <code>load</code> 操作都完成后，才能执行该屏障后面的 <code>load</code> 操作。这种屏障保证了前面的 <code>load</code> 操作对后面的 <code>load</code> 操作的可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">SharedData data = ...;  // 获取共享对象的引用
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">while (!data.flag) {
+</span></span><span class="line"><span class="cl">    // 使用 LoadLoad 屏障保证可见性
+</span></span><span class="line"><span class="cl">    // 在这里插入 LoadLoad 屏障确保读取到最新的 flag 值
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// 使用 LoadLoad 屏障保证可见性
+</span></span><span class="line"><span class="cl">int result = data.x;  // 3. Load 操作
+</span></span></code></pre></div></li>
+<li><code>StoreStore</code>屏障：保证在该屏障之前的所有 <code>store</code> 操作都完成后，才能执行该屏障后面的 <code>store</code> 操作。这确保了前面的 <code>store</code> 操作对后面的 <code>store</code> 操作的可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">data.x = 42;        // 1. Store 操作
+</span></span><span class="line"><span class="cl">// 使用 StoreStore 屏障确保顺序性
+</span></span><span class="line"><span class="cl">data.flag = true;   // 2. Store 操作
+</span></span></code></pre></div></li>
+<li><code>LoadStore</code>屏障：确保在该屏障之前的所有 <code>load</code> 操作都完成后，才能执行该屏障后面的 <code>store</code> 操作。这种屏障保证了前面的 <code>load</code> 操作对后面的 <code>store</code> 操作的可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">while (!data.flag) {
+</span></span><span class="line"><span class="cl">    // Spin until flag is true
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// 使用 LoadStore 屏障保证顺序性
+</span></span><span class="line"><span class="cl">int result = data.x;  // 3. Load 操作
+</span></span></code></pre></div></li>
+<li><code>StoreLoad</code>屏障：保证在该屏障之前的所有 <code>store</code> 操作都完成后，才能执行该屏障后面的 <code>load</code> 操作。这确保了前面的 <code>store</code> 操作对后面的 <code>load</code> 操作的可见性。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">data.x = 42;        // 1. Store 操作
+</span></span><span class="line"><span class="cl">// 使用 StoreLoad 屏障保证可见性
+</span></span><span class="line"><span class="cl">data.flag = true;   // 2. Store 操作
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 在另一个线程 B 中
+</span></span><span class="line"><span class="cl">while (!data.flag) {
+</span></span><span class="line"><span class="cl">    // Spin until flag is true
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">int result = data.x;  // 3. Load 操作
+</span></span></code></pre></div></li>
+</ol>
+<h3 id="happens-before">Happens-Before</h3>
+<p>&ldquo;Happens-Before&quot;原则是Java内存模型中的一个核心概念，用来定义多个线程之间操作的执行顺序和内存可见性。
+如果一个操作A在另一个操作B之前，那么在内存模型中，A的所有操作结果对于B是可见的，并且A的执行顺序在B之前。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ProgramOrderExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">example</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">    </span><span class="c1">// 1. Happens-Before</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// 2. Happens-Before</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>需要注意的是两个操作之间存在Happens-Before关系，并不意味着Java的具体实现必须要按照Happens-Before关系指定的顺序来执行。
+如果重排序之后的执行结果，与按Happens-Before关系来执行的结果一致，那么JMM允许这种重排序。JMM只要求在最终的执行结果上保持与Happens-Before关系一致的语义。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HappensBeforeExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">         </span><span class="c1">// Statement 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">   </span><span class="c1">// Statement 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">    </span><span class="c1">// Statement 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;x = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">x</span><span class="p">);</span><span class="w">  </span><span class="c1">// Statement 4</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;flag is false&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>根据Happens-Before规则：</p>
+<ul>
+<li>Statement 1 在 Statement 2 之前执行，因此 <code>x = 1</code> 的操作 Happens-Before <code>flag = true</code> 的操作。</li>
+<li>Statement 2 在 Statement 3 之前执行，因此 <code>flag = true</code> 的操作 Happens-Before <code>if (flag)</code> 的操作。</li>
+</ul>
+<p>如果<code>thread2</code>观察到<code>flag</code>的值为<code>true</code>，则说明 Happens-Before 原则保证了在此之前的操作结果对于其他线程是可见的。但是只要不改变程序的最终执行结果和Happens-Before关系，Java内存模型允许编译器和处理器进行指令重排序。
+<code>thread1</code>可能会将<code>flag</code>设置 <code>true</code>之后才设置 <code>x</code> 的值为<code>1</code>。这种情况下，<code>thread2</code>在检查<code>flag</code>之后，可能会观察到 <code>x = 1</code>。
+这种情况仍然满足Happens-Before关系，尽管发生了重排序。</p>
+<p>&ldquo;Happens-Before&quot;原则在Java内存模型中包含8条具体的规则：</p>
+<ol>
+<li>程序顺序规则。在一个线程内，按照程序代码的顺序执行，前面的操作总是先于后面的操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int a = 1;   // 1. Happens-Before
+</span></span><span class="line"><span class="cl">int b = 2;   // 2. Happens-Before
+</span></span></code></pre></div></li>
+<li>监视器锁规则。一个线程在同步块内部对一个锁的解锁操作，一定早于另一个线程对同一个锁的加锁操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">synchronized(lock) {
+</span></span><span class="line"><span class="cl">    // 操作 A
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">// 锁的释放 Happens-Before 后续的加锁
+</span></span><span class="line"><span class="cl">synchronized(lock) {
+</span></span><span class="line"><span class="cl">    // 操作 B
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li><code>volatile</code>变量规则。对一个 <code>volatile</code> 变量的写操作，一定早于随后对这个变量的读操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">volatile boolean flag = false;
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">flag = true; // 写操作 Happens-Before
+</span></span><span class="line"><span class="cl">if (flag) {  // 读操作
+</span></span><span class="line"><span class="cl">    // flag 的写操作 Happens-Before flag 的读操作
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>线程启动规则。主线程启动一个子线程，子线程中的操作一定在主线程中启动该子线程的操作之后执行。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 操作 B
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start(); // 启动操作 Happens-Before
+</span></span></code></pre></div></li>
+<li>线程终止规则。一个线程中的所有操作一定早于另一个线程检测到这个线程已经终止。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 操作 A
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start();
+</span></span><span class="line"><span class="cl">t.join(); // A Happens-Before join 返回
+</span></span></code></pre></div></li>
+<li>线程中断规则。对线程的中断操作一定早于被中断线程检测到中断事件。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 检测中断
+</span></span><span class="line"><span class="cl">    if (Thread.interrupted()) {
+</span></span><span class="line"><span class="cl">        // 中断事件发生
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t.start();
+</span></span><span class="line"><span class="cl">t.interrupt(); // Happens-Before 检测中断
+</span></span></code></pre></div></li>
+<li>对象的构造函数规则。一个对象的构造函数执行结束一定早于该对象的 finalize 方法开始执行。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">class MyObject {
+</span></span><span class="line"><span class="cl">    @Override
+</span></span><span class="line"><span class="cl">    protected void finalize() {
+</span></span><span class="line"><span class="cl">        // 构造函数 Happens-Before finalize 方法
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>传递性规则。如果操作 A 发生在操作 B 之前，操作 B 发生在操作 C 之前，那么操作 A 一定早于操作 C。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread t1 = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 操作 A
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">Thread t2 = new Thread(() -&gt; {
+</span></span><span class="line"><span class="cl">    // 操作 B
+</span></span><span class="line"><span class="cl">});
+</span></span><span class="line"><span class="cl">t1.start();
+</span></span><span class="line"><span class="cl">t1.join(); // A Happens-Before join 返回
+</span></span><span class="line"><span class="cl">t2.start();
+</span></span><span class="line"><span class="cl">t2.join(); // join 返回 Happens-Before B
+</span></span></code></pre></div></li>
+</ol>
+<h3 id="as-if-serial">as-if-serial</h3>
+<p>为了提高并行度，优化程序性能，编译器和处理器会对代码进行指令重排序。但为了不改变程序的执行结果，尽可能地提高程序执行的并行度，编译器、必须遵守<code>as-if-serial</code>语义。</p>
+<p>&ldquo;as-if-serial&quot;最初来自于计算机科学领域中的编译优化和程序行为的讨论。
+这个概念的核心思想是，编译器和计算机系统在进行优化时，可以重新排列和改变指令的执行顺序，只要最终程序的执行结果与按照程序顺序执行时的结果一致即可。
+这个原则确保了编译器和硬件系统在优化时不会改变程序的语义和行为。就是不管怎么重排序，单线程程序的执行结果不能被改变。</p>
+<p>编译器和处理器不会对存在数据依赖关系的操作做重排序，因为这种重排序会改变执行结果。但是如果操作之间不存在数据依赖关系，这些操作可能被编译器和处理器重排序。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int a=1;
+</span></span><span class="line"><span class="cl">int b=2;
+</span></span><span class="line"><span class="cl">int c=a+b;
+</span></span></code></pre></div><p>a和c之间存在数据依赖关系，同时b和c之间也存在数据依赖关系。因此在最终执行的指令序列中，c不能被重排序到A和B的前面，c如果排到a和b的前面，程序的结果将会被改变。
+a和b之间没有数据依赖关系，编译器和处理器可以重排序a和b之间的执行顺序。</p>
+<h2 id="volatile">volatile</h2>
+<p><code>volatile</code>通常被比喻成轻量级的锁，是Java并发编程中比较重要的一个关键字。<code>volatile</code>作用：</p>
+<ul>
+<li>可见性：当一个线程修改了 <code>volatile</code> 变量的值，新的值对于其他线程是立即可见的。这避免了其他线程读取到旧的缓存值。</li>
+<li>有序性：对 <code>volatile</code> 变量的读写操作不会被重排序。所有对 <code>volatile</code> 变量的写操作在内存中会按照程序的顺序执行，同时在一个线程中的操作不会重排序到 <code>volatile</code> 变量的读写操作之后。</li>
+</ul>
+<p>注意<code>volatile</code>不保证原子性，也就是线程不安全。</p>
+<h3 id="使用案例">使用案例</h3>
+<p>在Java中<code>volatile</code>是一个变量修饰符，只能用来修饰变量。<code>volatile</code>典型的使用就是单例模式中的双重检查锁实现。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">多线程下的单例模式 DCL(double check lock)
+</span></span></span><span class="line"><span class="cl"><span class="cm">**/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SingletonDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// volatile 此处作用 禁止指令重排</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">SingletonDemo</span><span class="w"> </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">SingletonDemo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">SingletonDemo</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">SingletonDemo</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SingletonDemo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为什么在此处要使用<code>volatile</code>修饰<code>singleton</code>？
+多线程下的DCL单例模式，如果不加<code>volatile</code>修饰不是绝对安全的，因为在创建对象的时候JVM底层会进行三个步骤：</p>
+<ol>
+<li>分配对象的内存空间；</li>
+<li>初始化对象；</li>
+<li>设置对象指向刚刚分配的内存地址；</li>
+</ol>
+<p>其中步骤2和步骤3是没有数据依赖关系的，而且无论重排前还是重排后的程序执行结果在单线程中并没有改变，因此这种重排优化是允许的。
+所以有可能先执行步骤3在执行步骤2，导致分配的对象不为<code>null</code>，但对象没有被初始化。所以当一个线程获取对象不为<code>null</code>时，由于对象未必已经完成初始化，会存在线程不安全的风险。</p>
+<h3 id="volatile与可见性">volatile与可见性</h3>
+<p>各个线程对主内存中共享变量的操作，都是各个线程各自拷贝到自己的工作内存操作后再写回主内存中的。
+这就可能存在一个线程AAA修改了共享变量X的值还未写回主内存中时 ，另外一个线程BBB又对内存中的一个共享变量X进行操作，但此时A线程工作内存中的共享比那里X对线程B来说并不不可见。
+这种工作内存与主内存同步延迟现象就造成了可见性问题。</p>
+<p>这种变量的可见性问题可以用<code>volatile</code>来解决。<code>volatile</code>的作用简单来说就是当一个线程修改了数据，并且写回主物理内存，其他线程都会得到通知获取最新的数据。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// thread1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; is come in&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 模拟执行其他业务</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 用该线程改变A类中 number 变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">a</span><span class="p">.</span><span class="na">numberTo100</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">},</span><span class="w"> </span><span class="s">&#34;thread1&#34;</span><span class="p">).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果number 等于0，则其他线程会一直等待 则证明 volatile 没有保证变量的可见性；相反则保证了变量的可见性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">number</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; thread is over&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 注意: 此时变量要加 volatile 关键字修饰； 可以去掉 volatile 来进行对比测试</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">numberTo100</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; update number&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>为什么<code>volatile</code>能确保变量的可见性？
+将上面单例模式DCL实现用命令<code>javap -v SingletonDemo.class &gt;test.txt</code>命令执行，将反编译后的字节码指令写入到test文件中，可以看到<code>ACC_VOLATILE</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public static volatile content.posts.rookie.SingletonDemo singleton;
+</span></span><span class="line"><span class="cl">descriptor: Lcontent/posts/rookie/SingletonDemo;
+</span></span><span class="line"><span class="cl">flags: ACC_PUBLIC, ACC_STATIC, ACC_VOLATILE
+</span></span></code></pre></div><p><code>volatile</code>在字节码层面，就是使用访问标志<code>ACC_VOLATILE</code>来表示，供后续操作此变量时判断访问标志是否为<code>ACC_VOLATILE</code>，来决定是否遵循<code>volatile</code>的语义处理。</p>
+<p>可以从<code>openjdk8</code>中找到对应的源码文件：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">openjdk8/hotspot/src/share/vm/interpreter/bytecodeInterpreter.cpp
+</span></span></code></pre></div><p><img alt="volitile字节码" src="/iblog/posts/annex/images/essays/volitile%E5%AD%97%E8%8A%82%E7%A0%81.png"></p>
+<p>重点是<code>cache-&gt;is_volatile()</code>方法，调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">bytecodeInterpreter.cpp&gt;is_volatile() 
+</span></span><span class="line"><span class="cl">==&gt; accessFlags.hpp&gt;is_volatile 
+</span></span><span class="line"><span class="cl">==&gt; bytecodeInterpreter.cpprelease_byte_field_put
+</span></span><span class="line"><span class="cl">==&gt; oop.inline.hpp&gt;(oopDesc::byte_field_acquire、oopDesc::release_byte_field_put)
+</span></span><span class="line"><span class="cl">==&gt; orderAccess.hpp
+</span></span><span class="line"><span class="cl">&gt;&gt; orderAccess_linux_x86.inline.hpp.OrderAccess::release_store
+</span></span></code></pre></div><p>最终调用了<code>OrderAccess::release_store</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">inline void     OrderAccess::release_store(volatile jbyte*   p, jbyte   v) { *p = v; }
+</span></span><span class="line"><span class="cl">inline void     OrderAccess::release_store(volatile jshort*  p, jshort  v) { *p = v; }
+</span></span></code></pre></div><p>可以从上面看到C++的实现层面，又使用C++中的<code>volatile</code>关键字，用来修饰变量，通常用于建立语言级别的内存屏障<code>memory barrier</code>。
+在《C++ Programming Language》一书中对<code>volatile</code>修饰词的解释：</p>
+<blockquote>
+<p>A volatile specifier is a hint to a compiler that an object may change its value in ways not specified by the language so that aggressive optimizations must be avoided.</p>
+</blockquote>
+<ul>
+<li><code>volatile</code>修饰的类型变量表示可以被某些编译器未知的因素更改。</li>
+<li>使用 <code>volatile</code> 变量时，避免激进的优化。系统总是重新从内存读取数据，即使它前面的指令刚从内存中读取被缓存，防止出现未知更改和主内存中不一致。</li>
+</ul>
+<p>其在64位系统的实现<code>orderAccess_linux_x86.inline.hpp.OrderAccess::release_store</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">inline void OrderAccess::fence() {
+</span></span><span class="line"><span class="cl">  if (os::is_MP()) {
+</span></span><span class="line"><span class="cl">    // always use locked addl since mfence is sometimes expensive
+</span></span><span class="line"><span class="cl">#ifdef AMD64
+</span></span><span class="line"><span class="cl">    __asm__ volatile (&#34;lock; addl $0,0(%%rsp)&#34; : : : &#34;cc&#34;, &#34;memory&#34;);
+</span></span><span class="line"><span class="cl">#else
+</span></span><span class="line"><span class="cl">    __asm__ volatile (&#34;lock; addl $0,0(%%esp)&#34; : : : &#34;cc&#34;, &#34;memory&#34;);
+</span></span><span class="line"><span class="cl">#endif
+</span></span><span class="line"><span class="cl">  }
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>其中代码<code>lock; addl $0,0(%%rsp)</code>就是常说的<strong>lock前缀</strong>。</p>
+<blockquote>
+<p>lock前缀，会保证某个处理器对共享内存的独占使用。它将本处理器缓存写入内存，该写入操作会引起其他处理器或内核对应的缓存失效。通过独占内存、使其他处理器缓存失效，达到了“指令重排序无法越过内存屏障”的作用。</p>
+</blockquote>
+<p>对于 <code>volatile</code>修饰的变量，当对 <code>volatile</code> 修饰的变量进行写操作的时候，JVM会向处理器发送一条带有<code>lock</code>前缀的指令，将这个缓存中的变量回写到系统主存中。
+但是就算写回到内存，如果其他处理器缓存的值还是旧的，再执行计算操作就会有问题，所以在多处理器下，为了保证各个处理器的缓存是一致的，就会实现<strong>缓存一致性协议</strong>。</p>
+<blockquote>
+<p>缓存一致性协议: 每个处理器通过嗅探在总线上传播的数据来检查自己缓存的值是不是过期了，当处理器发现自己缓存行对应的内存地址被修改，就会将当前处理器的缓存行设置成无效状态，当处理器要对这个数据进行修改操作的时候，会强制重新从系统内存里把数据读到处理器缓存里。</p>
+</blockquote>
+<p>为了提高CPU处理器的执行速度，在处理器和内存之间增加了多级缓存来提升。但是由于引入了多级缓存，就存在缓存数据不一致问题。</p>
+<p><img alt="CPU多级缓存" src="/iblog/posts/annex/images/essays/CPU%E5%A4%9A%E7%BA%A7%E7%BC%93%E5%AD%98.jpg"></p>
+<p>所以如果一个变量被<code>volatile</code>所修饰的话，在每次数据变化之后，其值都会被强制刷入主存。
+而其他处理器的缓存由于遵守了缓存一致性协议，也会把这个变量的值从主存加载到自己的缓存中。这就保证了一个<code>volatile</code>在并发编程中，其值在多个缓存中是可见的。</p>
+<h3 id="volatile与有序性">volatile与有序性</h3>
+<p>有序性指的就是代码按照顺序执行，是对比指令重排来说的。计算机在执行程序时，为了提高性能，编译器和处理器常常会做指令重排。
+在上面的使用案例中的代码，单例模式DCL就是一个使用禁止指令重排的案例。</p>
+<p><code>volatile</code>禁止指令重排的原因是什么？<code>volatile</code> 关键字通过在读写操作前后插入内存屏障来禁止指令重排序，从而确保了内存可见性和操作的有序性。</p>
+<ol>
+<li>写入<code>volatile</code>变量时：</li>
+</ol>
+<ul>
+<li>在写操作之前插入一个 <code>StoreStore</code> 屏障，确保在写入 <code>volatile</code> 变量之前的所有普通写操作都已经完成。</li>
+<li>在写操作之后插入一个 <code>StoreLoad</code> 屏障，确保在写入 <code>volatile</code> 变量之后的所有普通读操作都能读取到最新的值。</li>
+</ul>
+<ol start="2">
+<li>读取<code>volatile</code>变量时：</li>
+</ol>
+<ul>
+<li>在读操作之前插入一个 <code>LoadLoad</code> 屏障，确保在读取 <code>volatile</code> 变量之前的所有普通读操作都已经完成。</li>
+<li>在读操作之后插入一个 <code>LoadStore</code> 屏障，确保在读取 <code>volatile</code> 变量之后的所有普通写操作都能读取到最新的值。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Example</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writer</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">42</span><span class="p">;</span><span class="w">    </span><span class="c1">// 1. 普通写操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">   </span><span class="c1">// 2. volatile 写操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">reader</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">flag</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">    </span><span class="c1">// 3. volatile 读操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w"> </span><span class="c1">// 4. 普通读操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="volatile与原子性">volatile与原子性</h3>
+<p><code>volatile</code>不保证原子性，也就是线程不安全。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 创建20个线程 每个线程让 number++ 1000次；
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * number 变量用 volatile 修饰
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 如果 volatile 保证变量的原子性，则最后结果为 20 * 1000，反之则不保证。
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 当然不排除偶然事件，建议反复多试几次。
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">a</span><span class="p">.</span><span class="na">addPlusplus</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前存活线程大于 2 个(包括main线程) 礼让线程继续执行上边的线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">activeCount</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">yield</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; Thread is over\t&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="na">number</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addPlusplus</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">number</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>不保证原子性的原因，由于各个线程之间都是复制主内存的数据到自己的工作空间里边修改数据，CPU的轮询反复切换线程，会导致数据丢失。
+即某个线程修改了数据，准备回主内存，此时CPU切换到另一个线程修改了数据，并且写回到了主内存。其他的线程不知道主内存的数据已经被更改，还会执行将之前从主内存复制的数据修改后的，写到主内存，这就导致了数据被覆盖、丢失。</p>
+<p>如果要解决原子性的问题，在Java中只能控制线程，在修改的时候不能被中断，即加锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 创建20个线程 每个线程让 number++ 1000次；
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * number 变量用 volatile 修饰
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 如果 volatile 保证变量的原子性，则最后结果为 20 * 1000，反之则不保证。
+</span></span></span><span class="line"><span class="cl"><span class="cm">         * 当然不排除偶然事件，建议反复多试几次。
+</span></span></span><span class="line"><span class="cl"><span class="cm">         */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">a</span><span class="p">.</span><span class="na">addPlusplus</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前存活线程大于 2 个(包括main线程) 礼让线程继续执行上边的线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">activeCount</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Thread</span><span class="p">.</span><span class="na">yield</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; Thread is over\t&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="na">number</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 如果要解决原子性的问题可以用synchronized 关键字(这种太浪费性能)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 可用JUC下的 AtomicInteger 来解决
+</span></span></span><span class="line"><span class="cl"><span class="cm">     **/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">atomicInteger</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">number</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addPlusplus</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">number</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">incrementAndGet</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>对于<code>AtomicInteger.incrementAndGet</code>方法来说，原理就是<code>volatile</code> + <code>do...while()</code> + <code>CAS</code>;</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">incrementAndGet</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">getAndAddInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//=========================</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>用<code>volatile</code>修饰该变量，保证该变量被某个线程修改时，保证其他线程中的这个变量的可见性。
+在多线程环境下，CPU轮流切换线程执行，有可能某个线程修改了数据，准备回主内存，此时CPU切换到另一个线程修改了数据，并且写回到了主内存，此时就导致数据的不准确。
+<code>do...while()</code> + <code>CAS</code>的作用就是，当某个线程工作内存中的值与主内存中的值，如果不相同就会一直<code>while</code>循环下去，之所以用<code>do..while</code>是考虑到做自增操作。</p>
+<h2 id="synchronized">synchronized</h2>
+<p><code>synchronized</code>是Java提供的关键字译为同步，是Java中用于实现线程同步的一种机制。它可以确保在同一时间只有一个线程能够执行某段代码，从而避免线程安全问题。
+当它修饰一个方法或者一个代码块的时候，同一时刻最多只有一个线程执行这段代码。<code>synchronized</code>关键字在需要原子性、可见性和有序性这三种特性的时候都可以作为其中一种解决方案，大部分并发控制操作都能使用<code>synchronized</code>来完成。</p>
+<p><code>synchronized</code>的作用：</p>
+<ul>
+<li>互斥性：确保在同一时间只有一个线程可以执行被 <code>synchronized</code> 修饰的代码块或方法。</li>
+<li>可见性：当一个线程退出 <code>synchronized</code> 代码块时，它所做的所有修改对于进入 <code>synchronized</code> 代码块的其他线程是可见的。这是通过释放和获得监视器锁来实现的。</li>
+</ul>
+<h3 id="使用示例">使用示例</h3>
+<table>
+<thead>
+<tr>
+<th>修饰的对象</th>
+<th>作用范围</th>
+<th>作用对象</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>同步一个实例方法</td>
+<td>整个实例方法</td>
+<td>调用此方法的对象</td>
+</tr>
+<tr>
+<td>同步一个静态方法</td>
+<td>整个静态方法</td>
+<td>此类的所有对象</td>
+</tr>
+<tr>
+<td>同步代码块-对象</td>
+<td>整个代码块</td>
+<td>调用此代码块的对象</td>
+</tr>
+<tr>
+<td>同步代码块-类</td>
+<td>整个代码块</td>
+<td>此类的所有对象</td>
+</tr>
+</tbody>
+</table>
+<ul>
+<li>同步一个实例方法。在这种情况下，<code>increment</code>方法被声明为同步方法。当一个线程调用这个方法时，它会获得该实例的监视器锁，其他线程必须等待这个线程释放锁后才能调用这个方法。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>同步一个静态方法。当<code>synchronized</code>作用于静态方法时，其锁就是当前类的<code>class</code>对象锁。由于静态成员不专属于任何一个实例对象，而是类成员，因此通过<code>class</code>对象锁可以控制静态成员的并发操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>同步代码块。在某些情况下，我们编写的方法体可能比较大，同时存在一些比较耗时的操作，而需要同步的代码又只有一小部分，如果直接对整个方法进行同步操作，这样做就有点浪费。此时我们可以使用同步代码块的方式对需要同步的代码进行包裹。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div>除了使用<code>synchronized(this)</code>锁定，当然静态方法是没有this对象的，也可以使用<code>class</code>对象来做为锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">MainTest</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>当如果没有明确的对象作为锁，只是想让一段代码同步时，可以创建一个特殊的对象来充当锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">method</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">synchronized</span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="c1">// .....</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>零长度的<code>byte</code>数组对象创建起来将比任何对象都经济。查看编译后的字节码，生成零长度的<code>byte[]</code>对象只需3条操作码，而<code>Object lock = new Object()</code>则需要7行操作码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">byte[] emptyArray = new byte[0];
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">0: iconst_0       // 将常量0推送到栈顶
+</span></span><span class="line"><span class="cl">1: newarray byte  // 创建一个新的byte类型数组
+</span></span><span class="line"><span class="cl">3: astore_1       // 将引用类型的数据存储到局部变量表中
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Object lock = new Object();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">0: new           #2   // 创建一个新的对象
+</span></span><span class="line"><span class="cl">3: dup                // 复制栈顶的操作数栈顶的值，并将复制值压入栈顶
+</span></span><span class="line"><span class="cl">4: invokespecial #1   // 调用实例初始化方法, 使用Object.&lt;init&gt;
+</span></span><span class="line"><span class="cl">7: astore_1           // 将引用类型的数据存储到局部变量表中
+</span></span></code></pre></div><h3 id="实现原理">实现原理</h3>
+<p><code>synchronized</code>关键字在Java中通过进入和退出一个监视器来实现同步。监视器本质上是一种锁，它可以是类对象锁或实例对象锁。每个对象在JVM中都有一个与之关联的监视器。
+当一个线程进入同步代码块或方法时，它会尝试获得对象的监视器。如果成功获得锁，线程就可以执行同步代码；否则它将被阻塞，直到获得锁为止。</p>
+<p>在Java中<code>synchronized</code>锁对象时，其实就是改变对象中的对象头的<code>markword</code>的锁的标志位来实现的。用<code>javap -v MainTest.class</code>命令反编译下面代码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">demo01</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;demo 01&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">demo02</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">MainTest</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;demo 02&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">  synchronized void demo01();
+</span></span><span class="line"><span class="cl">    descriptor: ()V
+</span></span><span class="line"><span class="cl">    flags: ACC_SYNCHRONIZED
+</span></span><span class="line"><span class="cl">    Code:
+</span></span><span class="line"><span class="cl">      stack=2, locals=1, args_size=1
+</span></span><span class="line"><span class="cl">         0: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
+</span></span><span class="line"><span class="cl">         3: ldc           #3                  // String demo 01
+</span></span><span class="line"><span class="cl">         5: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">         8: return
+</span></span><span class="line"><span class="cl">// ...
+</span></span><span class="line"><span class="cl">void demo02();
+</span></span><span class="line"><span class="cl">    descriptor: ()V
+</span></span><span class="line"><span class="cl">    flags:
+</span></span><span class="line"><span class="cl">    Code:
+</span></span><span class="line"><span class="cl">      stack=2, locals=3, args_size=1
+</span></span><span class="line"><span class="cl">         0: ldc           #5                  // class content/posts/rookie/MainTest
+</span></span><span class="line"><span class="cl">         2: dup
+</span></span><span class="line"><span class="cl">         3: astore_1
+</span></span><span class="line"><span class="cl">         4: monitorenter
+</span></span><span class="line"><span class="cl">         5: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
+</span></span><span class="line"><span class="cl">         8: ldc           #6                  // String demo 02
+</span></span><span class="line"><span class="cl">        10: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
+</span></span><span class="line"><span class="cl">        13: aload_1
+</span></span><span class="line"><span class="cl">        14: monitorexit
+</span></span><span class="line"><span class="cl">        15: goto          23
+</span></span><span class="line"><span class="cl">        18: astore_2
+</span></span><span class="line"><span class="cl">        19: aload_1
+</span></span><span class="line"><span class="cl">        20: monitorexit
+</span></span><span class="line"><span class="cl">        21: aload_2
+</span></span><span class="line"><span class="cl">        22: athrow
+</span></span><span class="line"><span class="cl">        23: return
+</span></span><span class="line"><span class="cl">// ...
+</span></span></code></pre></div><p>通过反编译后代码可以看出：</p>
+<ul>
+<li>对于同步方法，JVM采用<code>ACC_SYNCHRONIZED</code>标记符来实现同步；</li>
+<li>对于同步代码块，JVM采用<code>monitorenter</code>、<code>monitorexit</code>两个指令来实现同步；</li>
+</ul>
+<p>其中同步代码块，有两个<code>monitorexit</code>指令的原因是为了保证抛异常的情况下也能释放锁，所以<code>javac</code>为同步代码块添加了一个隐式的<code>try-finally</code>，在<code>finally</code>中会调用<code>monitorexit</code>命令释放锁。</p>
+<p><a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-2.html#jvms-2.11.10">官方文档</a>中关于同步方法和同步代码块的实现原理描述：</p>
+<blockquote>
+<p>方法级的同步是隐式的。同步方法的常量池中会有一个 <code>ACC_SYNCHRONIZED</code> 标志。当某个线程要访问某个方法的时候，会检查是否有 <code>ACC_SYNCHRONIZED</code>，如果有设置，则需要先获得监视器锁，然后开始执行方法，方法执行之后再释放监视器锁。这时如果其他线程来请求执行方法，会因为无法获得监视器锁而被阻断住。值得注意的是，如果在方法执行过程中，发生了异常，并且方法内部并没有处理该异常，那么在异常被抛到方法外面之前监视器锁会被自动释放。<br>
+同步代码块使用 <code>monitorenter</code> 和 <code>monitorexit</code> 两个指令实现。可以把执行 <code>monitorenter</code> 指令理解为加锁，执行 <code>monitorexit</code> 理解为释放锁。 每个对象维护着一个记录着被锁次数的计数器。未被锁定的对象的该计数器为0，当一个线程获得锁（执行 <code>monitorenter</code>）后，该计数器自增变为 1 ，当同一个线程再次获得该对象的锁的时候，计数器再次自增。当同一个线程释放锁（执行 <code>monitorexit</code> 指令）的时候，计数器再自减。当计数器为0的时候。锁将被释放，其他线程便可以获得锁。</p>
+</blockquote>
+<p>其实无论是<code>ACC_SYNCHRONIZED</code>还是<code>monitorenter</code>、<code>monitorexit</code>都是基于<code>Monitor</code>实现的，每一个锁都对应一个<code>monitor</code>对象。
+在Java虚拟机(HotSpot)中，<code>Monitor</code>是基于C++实现的，由<code>ObjectMonitor</code>实现。在<code>/hotspot/src/share/vm/runtime/objectMonitor.hpp</code>中有<code>ObjectMonitor</code>的实现。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// initialize the monitor, exception the semaphore, all other fields
+</span></span><span class="line"><span class="cl">// are simple integers or pointers
+</span></span><span class="line"><span class="cl">ObjectMonitor() {
+</span></span><span class="line"><span class="cl">    _header       = NULL;
+</span></span><span class="line"><span class="cl">    _count        = 0; //记录个数
+</span></span><span class="line"><span class="cl">    _waiters      = 0,
+</span></span><span class="line"><span class="cl">    _recursions   = 0;
+</span></span><span class="line"><span class="cl">    _object       = NULL;
+</span></span><span class="line"><span class="cl">    _owner        = NULL;
+</span></span><span class="line"><span class="cl">    _WaitSet      = NULL; //处于wait状态的线程，会被加入到_WaitSet
+</span></span><span class="line"><span class="cl">    _WaitSetLock  = 0 ;
+</span></span><span class="line"><span class="cl">    _Responsible  = NULL ;
+</span></span><span class="line"><span class="cl">    _succ         = NULL ;
+</span></span><span class="line"><span class="cl">    _cxq          = NULL ;
+</span></span><span class="line"><span class="cl">    FreeNext      = NULL ;
+</span></span><span class="line"><span class="cl">    _EntryList    = NULL ; //处于等待锁block状态的线程，会被加入到该列表
+</span></span><span class="line"><span class="cl">    _SpinFreq     = 0 ;
+</span></span><span class="line"><span class="cl">    _SpinClock    = 0 ;
+</span></span><span class="line"><span class="cl">    OwnerIsThread = 0 ;
+</span></span><span class="line"><span class="cl">  }
+</span></span></code></pre></div><ul>
+<li><code>_owner</code>：指向持有<code>ObjectMonitor</code>对象的线程；</li>
+<li><code>_WaitSet</code>：存放处于<code>wait</code>状态的线程队列；</li>
+<li><code>_EntryList</code>：存放处于等待锁<code>block</code>状态的线程队列；</li>
+<li><code>_recursions</code>：锁的重入次数；</li>
+<li><code>_count</code>：用来记录该线程获取锁的次数；</li>
+</ul>
+<p>当多个线程同时访问一段同步代码时，首先会进入<code>_EntryList</code>队列中，当某个线程获取到对象的<code>monitor</code>后进入<code>_Owner</code>区域，并把<code>monitor</code>中的<code>_owner</code>变量设置为当前线程，同时<code>monitor</code>中的计数器<code>_count</code>加1，即获得对象锁。</p>
+<p><img alt="synchronized原理" src="/iblog/posts/annex/images/essays/synchronized%E5%8E%9F%E7%90%86.gif"></p>
+<p>若此时持有<code>monitor</code>的线程调用<code>wait()</code>方法，将释放当前对象持有的<code>monitor</code>，<code>_owner</code>变量恢复为<code>null</code>，<code>_count</code>自减1，同时该线程进入<code>_WaitSet</code>集合中等待被唤醒。若当前线程执行完毕也将释放<code>monitor</code>并复位变量的值，以便其他线程进入获取<code>monitor</code>。</p>
+<p><code>ObjectMonitor</code>中其他方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">  bool      try_enter (TRAPS) ;
+</span></span><span class="line"><span class="cl">  void      enter(TRAPS);
+</span></span><span class="line"><span class="cl">  void      exit(bool not_suspended, TRAPS);
+</span></span><span class="line"><span class="cl">  void      wait(jlong millis, bool interruptable, TRAPS);
+</span></span><span class="line"><span class="cl">  void      notify(TRAPS);
+</span></span><span class="line"><span class="cl">  void      notifyAll(TRAPS);
+</span></span></code></pre></div><p><code>sychronized</code>加锁的时候，会调用<code>objectMonitor</code>的<code>enter</code>方法，解锁的时候会调用<code>exit</code>方法。
+在JDK1.6之前，<code>synchronized</code>的实现直接调用<code>ObjectMonitor</code>的<code>enter</code>和<code>exit</code>，这种锁被称之为重量级锁，这也是早期<code>synchronized</code>效率低的原因。
+所以，在JDK1.6中出现对锁进行了很多的优化，进而出现轻量级锁，偏向锁，锁消除，适应性自旋锁，锁粗化。</p>
+<blockquote>
+<p>早期的<code>synchronized</code>效率低的原因：
+Java的线程是映射到操作系统原生线程之上的，如果要阻塞或唤醒一个线程就需要操作系统的帮忙，监视器锁<code>monitor</code>是依赖于底层的操作系统的<code>Mutex Lock</code>来实现的，而操作系统实现线程之间的切换时需要从用户态转换到核心态。因此状态转换需要花费很多的处理器时间。
+对于代码简单的同步块（如被<code>synchronized</code>修饰的<code>get</code>、<code>set</code>方法）状态转换消耗的时间有可能比用户代码执行的时间还要长，所以说<code>synchronized</code>是Java语言中一个重量级的操作。也是为什么早期的<code>synchronized</code>效率低的原因。</p>
+</blockquote>
+<h3 id="锁的升级">锁的升级</h3>
+<p>在JDK1.6之前，使用<code>synchronized</code>被称作重量级锁，它的实现是基于底层操作系统的<code>mutex</code>互斥原语的，这个开销是很大的。所以在JDK1.6时JVM对<code>synchronized</code>做了优化。
+<code>synchronized</code>锁对象时，其实就是改变对象中的对象头的<code>markword</code>的锁的标志位来实现的。对象头中<code>markword</code>锁状态的表示：</p>
+<table>
+<thead>
+<tr>
+<th>锁状态</th>
+<th><code>markword</code> 锁标志位</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>无锁状态</td>
+<td><code>01</code></td>
+</tr>
+<tr>
+<td>偏向锁状态</td>
+<td><code>01</code></td>
+</tr>
+<tr>
+<td>轻量级锁状态</td>
+<td><code>00</code></td>
+</tr>
+<tr>
+<td>重量级锁状态</td>
+<td><code>10</code></td>
+</tr>
+<tr>
+<td>被垃圾回收器标记</td>
+<td><code>11</code></td>
+</tr>
+</tbody>
+</table>
+<p>对象的锁状态，可以分为4种，级别从低到高依次是：无锁状态、偏向锁状态、轻量级锁状态和重量级锁状态。
+其中这几个锁只有重量级锁是需要使用操作系统底层<code>mutex</code>互斥原语来实现，其他的锁都是使用对象头来实现的。</p>
+<ul>
+<li>无锁状态：<code>markword</code>锁的标志位0，偏向锁的标志位为1；例如：刚被创建出来的对象。</li>
+<li>偏向锁：如果一个线程获取了锁，此时<code>markword</code>的结构变为偏向锁结构，当这个线程再次请求锁时，无需再做任何同步操作，直接可以获取锁。
+省去了大量有关锁申请的操作，从而也就提供程序的性能。</li>
+<li>轻量级锁：当锁是偏向锁的时候，被另外的线程所访问，偏向锁就会升级为轻量级锁，其他线程会通过自旋的形式尝试获取锁，不会阻塞从而提高性能。</li>
+<li>重量级锁：升级为重量级锁时，锁标志的状态值变为“10”，此时<code>MarkWord</code>中存储的是指向重量级锁的指针，此时等待锁的线程都会进入阻塞状态，所以开销是很大。</li>
+</ul>
+<p>随着锁的竞争，锁从偏向锁升级到轻量级锁，再升级的重量级锁。锁升级过程：</p>
+<ol>
+<li>无锁状态升级为偏向锁：
+一个对象刚开始实例化的时候，没有任何线程来访问它的时候，它是可偏向的，意味着它现在认为只可能有一个线程来访问它，所以当第一个线程来访问它的时候，它会偏向这个线程。此时对象持有偏向锁。
+偏向第一个线程，这个线程在修改对象头成为偏向锁的时候使用CAS操作，并将对象头中的<code>ThreadID</code>改成自己的ID，之后再次访问这个对象时，只需要对比ID，就不需要再使用CAS在进行操作。</li>
+<li>偏向锁升级为轻量级锁：
+一旦有第二个线程访问这个对象，因为偏向锁不会主动释放，所以第二个线程可以看到对象的偏向状态。
+这时表明在这个对象上已经存在竞争了，JVM会检查原来持有该对象锁的线程是否依然存活，如果不存活，则可以将对象变为无锁状态，然后重新偏向新的线程。
+如果原来的线程依然存活，则马上执行这个线程的操作栈，检查该对象的使用情况，如果仍然需要持有偏向锁，则偏向锁升级为轻量级锁。</li>
+<li>轻量级锁升级为重量级锁：
+轻量级锁认为竞争存在，但是竞争的程度很轻，一般两个线程对于同一个锁的操作都会错开，或者说稍微等待一下，另一个线程就会释放锁。
+但是当自旋超过一定的次数，或者一个线程在持有锁，一个在自旋，又有第三个来访时，轻量级锁膨胀为重量级锁，重量级锁使除了拥有锁的线程以外的线程都阻塞。
+当持有锁的线程退出同步块或方法时，会执行<code>monitorexit</code>指令释放锁。如果有其他线程在等待该锁，它们会被唤醒并竞争锁的所有权。</li>
+</ol>
+<p>在所有的锁都启用的情况下，线程进入临界区时会先获取偏向锁，如果已经存在偏向锁了，则会尝试获取轻量级锁，启用自旋锁。
+如果自旋也没有获取到锁，则使用重量级锁，将没有获取到锁的线程阻塞挂起，直到持有锁的线程执行完同步块唤醒他们。</p>
+<p>偏向锁是在无锁争用的情况下使用的，也就是同步代码块在当前线程没有执行完之前，没有其它线程会执行该同步块。
+一旦有了第二个线程的争用，偏向锁就会升级为轻量级锁，如果轻量级锁自旋到达阈值后，没有获取到锁，就会升级为重量级锁。</p>
+<p>锁可以升级，但是不可以降级，有的观点认为不会进行锁降级。
+实际上，锁降级确实是会发生的，当JVM进入<strong>安全点</strong>的时候，会检查是否有闲置的`Monitor，然后试图进行降级。
+也就是说，仅仅是发生在STW的时候，只有垃圾回收线程能够观测到它，在我们正常使用的过程中是不会发生锁降级的，只有在GC的时候才会降级。</p>
+<blockquote>
+<p>安全点：程序执行时并非在所有地方都能停顿下来开始GC，只有在特定的位置才能停顿下来开始GC，这些位置称为安全点。</p>
+</blockquote>
+<h3 id="synchronized与可见性">synchronized与可见性</h3>
+<p>可见性是指当多个线程访问同一个变量时，一个线程修改了这个变量的值，其他线程能够立即看得到修改的值。</p>
+<p>Java内存模型规定了所有的变量都存储在主内存中，每条线程还有自己的工作内存，线程的工作内存中保存了该线程中是用到的变量的主内存副本拷贝，线程对变量的所有操作都必须在工作内存中进行，而不能直接读写主内存。
+不同的线程之间也无法直接访问对方工作内存中的变量，线程间变量的传递均需要自己的工作内存和主存之间进行数据同步进行。所以就可能出现线程1改了某个变量的值，但是线程2不可见的情况。</p>
+<p>被<code>synchronized</code>修饰的代码，在开始执行时会加锁，执行完成后会进行解锁。但是为了保证可见性，有一条规则是这样的，“对一个变量解锁之前，必须先把此变量同步回主存中”，这样解锁后，后续线程就可以访问到被修改后的值。
+所以<code>synchronized</code>关键字锁住的对象，其值是具有可见性的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">VisibilityExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">toggleFlag</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 修改共享变量并确保可见性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">!</span><span class="n">flag</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 其他操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isFlag</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取共享变量并确保可见性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">flag</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="synchronized与原子性">synchronized与原子性</h3>
+<p>原子性是指一个操作是不可中断的，要全部执行完成，要不就都不执行。</p>
+<p>线程是CPU调度的基本单位，CPU有时间片的概念，会根据不同的调度算法进行线程调度。当一个线程获得时间片之后开始执行，在时间片耗尽之后，就会失去CPU使用权。所以在多线程场景下，由于时间片在线程间轮换，就会发生原子性问题。
+在Java中，为了保证原子性，提供了两个高级的字节码指令<code>monitorenter</code>和<code>monitorexit</code>，这两个字节码指令，在Java中对应的关键字就是<code>synchronized</code>。
+通过<code>monitorexit</code>和<code>monitorexit</code>指令，可以保证被<code>synchronized</code>修饰的代码在同一时间只能被一个线程访问，在锁未释放之前，无法被其他线程访问到。
+因此在Java中可以使用<code>synchronized</code>来保证方法和代码块内的操作是原子性的。</p>
+<p>举个例子，线程1在执行<code>monitorenter</code>指令的时候，会对<code>Monitor</code>进行加锁，加锁后其他线程无法获得锁，除非线程1主动解锁。
+即使在执行过程中，由于某种原因，比如CPU时间片用完，线程1放弃了CPU，但是它并没有进行解锁。
+而由于<code>synchronized</code>的锁是可重入的，下一个时间片还是只能被他自己获取到，还是会继续执行代码，直到所有代码执行完，这就保证了原子性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AtomicityExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 原子性的递增操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">decrement</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 原子性的递减操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 原子性的读取操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicityExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicityExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程1：递增操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 线程2：递减操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">decrement</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 启动线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 等待两个线程执行完成</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">thread1</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">thread2</span><span class="p">.</span><span class="na">join</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 输出最终的计数结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Final Count: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">example</span><span class="p">.</span><span class="na">getCount</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="synchronized与有序性">synchronized与有序性</h3>
+<p>有序性即程序执行的顺序按照代码的先后顺序执行。</p>
+<p>除了引入了时间片以外，由于处理器优化和指令重排等，CPU还可能对输入代码进行乱序执行，比如<code>load-&gt;add-&gt;save</code>有可能被优化成<code>load-&gt;save-&gt;add</code>这就是可能存在有序性问题。
+这里需要注意的是，<code>synchronized</code>是无法禁止指令重排和处理器优化的，也就是说<code>synchronized</code>无法避免上述提到的问题。
+那<code>synchronized</code>是如何保证有序性的？</p>
+<p><code>synchronized</code>通过两个主要机制来保证有序性。<code>synchronized</code>的主要特性是互斥性，意味着在同一时刻只有一个线程可以进入同步块，既然是单线程就需要遵守<code>as-if-serial</code>语义，那么就可以认为单线程程序是按照顺序执行的。</p>
+<blockquote>
+<p><code>as-if-serial</code>语义：不管怎么重排序（编译器和处理器为了提高并行度），单线程程序的执行结果都不能被改变。编译器和处理器无论如何优化，都必须遵守<code>as-if-serial</code>语义。</p>
+</blockquote>
+<p>第二个保证就是内存屏障。编译器和CPU在执行代码时，可能会为了优化性能进行指令重排，但<code>synchronized</code>块内的指令不会被重排。
+原因就是Java内存模型通过在进入和退出<code>synchronized</code>块时插入内存屏障，来保证这些操作在多线程环境下的顺序执行。
+在进入<code>synchronized</code>块时，会插入一个<code>LoadLoad</code>屏障和一个<code>LoadStore</code>屏障，确保在锁被获取后，前面的所有读操作和写操作都已经完成。
+在退出<code>synchronized</code>块时，会插入一个<code>StoreStore</code>屏障和一个<code>StoreLoad</code>屏障，确保在锁被释放前，所有的写操作都已经完成，并且这些写操作对其他线程可见。</p>
+<h2 id="cas">CAS</h2>
+<p>CAS全称为<code>Compare and Swap</code>被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更新为新值。
+CAS操作是原子的，这意味着在多个线程同时执行CAS操作时，不会发生竞争条件。</p>
+<h3 id="使用示例-1">使用示例</h3>
+<p><code>java.util.concurrent.atomic</code>并发包下的所有原子类都是基于CAS来实现的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">atomicInteger</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">result</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;更新成功，当前值：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;更新失败，当前值：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">atomicInteger</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>CAS一些常见使用场景：</p>
+<ul>
+<li>使用CAS实现线程安全的计数器，避免传统锁的开销。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">oldValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">oldValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">counter</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">oldValue</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">counter</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">oldValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">newValue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>使用CAS来实现无锁队列、栈等数据结构。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASQueue</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">enqueue</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">item</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="nf">dequeue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentHead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentHead</span><span class="p">,</span><span class="w"> </span><span class="n">nextNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在数据库中，CAS可以用于实现乐观锁机制，避免长时间持有锁。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">OptimisticLocking</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="w"> </span><span class="n">version</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">updateWithOptimisticLock</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expectedVersion</span><span class="p">,</span><span class="w"> </span><span class="n">Runnable</span><span class="w"> </span><span class="n">updateTask</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">currentVersion</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentVersion</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">expectedVersion</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">updateTask</span><span class="p">.</span><span class="na">run</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentVersion</span><span class="p">,</span><span class="w"> </span><span class="n">currentVersion</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getVersion</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">version</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OptimisticLocking</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">OptimisticLocking</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">updateTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Performing update&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">version</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">getVersion</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">success</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">updateWithOptimisticLock</span><span class="p">(</span><span class="n">version</span><span class="p">,</span><span class="w"> </span><span class="n">updateTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">success</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Update successful.&#34;</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Update failed.&#34;</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在实现线程池时，CAS可以用于安全地管理线程状态和任务队列。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CASThreadPool</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">submitTask</span><span class="p">(</span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">newNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">newNode</span><span class="p">);</span><span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">tail</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentTail</span><span class="p">,</span><span class="w"> </span><span class="n">currentTail</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Runnable</span><span class="w"> </span><span class="nf">getTask</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currentHead</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">currentHead</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">Runnable</span><span class="o">&gt;</span><span class="w"> </span><span class="n">nextNode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">next</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">head</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">currentHead</span><span class="p">,</span><span class="w"> </span><span class="n">nextNode</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">currentHead</span><span class="p">.</span><span class="na">item</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="unsafe">Unsafe</h3>
+<p><code>Unsafe</code>是CAS的核心类，Java无法直接访问底层操作系统，而是通过<code>native</code>方法来访问。不过尽管如此，JVM还是开了一个后门，JDK中有一个类<code>Unsafe</code>，它提供了硬件级别的原子操作。</p>
+<p><code>Unsafe</code>类位于<code>sun.misc</code>包中，它提供了访问底层操作系统的特定功能，如直接内存访问、CAS 操作等。
+由于其提供了直接操作内存的能力，使用不当可能导致内存泄漏、数据损坏等问题，应谨慎使用。
+<code>Unsafe</code>类包含了许多不安全的操作，所以它并不是Java标准的一部分，而且在Java9开始已经标记为受限制的API。</p>
+<p>Java中CAS操作的执行依赖于<code>Unsafe</code>类的方法，<code>Unsafe</code>类中的所有方法都是<code>native</code>修饰的，也就是说<code>Unsafe</code>类中的方法都直接调用操作系统底层资源执行相应任务。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">UnsafeExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Unsafe</span><span class="w"> </span><span class="n">unsafe</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Field</span><span class="w"> </span><span class="n">field</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Unsafe</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;theUnsafe&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">field</span><span class="p">.</span><span class="na">setAccessible</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">unsafe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Unsafe</span><span class="p">)</span><span class="w"> </span><span class="n">field</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">valueOffset</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">objectFieldOffset</span><span class="p">(</span><span class="n">UnsafeExample</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;value&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">current</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">unsafe</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="p">,</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="实现原理-1">实现原理</h3>
+<p>以<code>AtomicInteger</code>原子整型类为例，来看一下CAS实现原理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicInteger</span><span class="p">().</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>调用栈如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">compareAndSet
+</span></span><span class="line"><span class="cl">    --&gt; unsafe.compareAndSwapInt
+</span></span><span class="line"><span class="cl">    ---&gt; unsafe.compareAndSwapInt
+</span></span><span class="line"><span class="cl">    --&gt; (C++) cmpxchg
+</span></span></code></pre></div><p><code>AtomicInteger</code>内部方法都是基于<code>Unsafe</code>类实现的。</p>
+<blockquote>
+<p><code>Unsafe</code>是CAS的核心类，Java无法直接访问底层操作系统，而是通过<code>native</code>方法来访问。不过尽管如此，JVM还是开了一个后门，JDK中有一个类<code>Unsafe</code>，它提供了硬件级别的原子操作。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// setup to use Unsafe.compareAndSwapInt for updates</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Unsafe</span><span class="w"> </span><span class="n">unsafe</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Unsafe</span><span class="p">.</span><span class="na">getUnsafe</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">valueOffset</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">objectFieldOffset</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">(</span><span class="n">AtomicInteger</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredField</span><span class="p">(</span><span class="s">&#34;value&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">ex</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="n">ex</span><span class="p">);</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSet</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">expect</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">update</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">unsafe</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">valueOffset</span><span class="p">,</span><span class="w"> </span><span class="n">expect</span><span class="p">,</span><span class="w"> </span><span class="n">update</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>compareAndSwapInt</code>方法参数：</p>
+<ul>
+<li><code>this</code>：<code>Unsafe</code>对象本身，需要通过这个类来获取 <code>value</code> 的内存偏移地址；</li>
+<li><code>valueOffset</code>： <code>valueOffset</code> 表示的是变量值在内存中的偏移地址，因为 <code>Unsafe</code> 就是根据内存偏移地址获取数据的原值的。</li>
+<li><code>expect</code>：当前预期的值；</li>
+<li><code>update</code>：要设置的新值；</li>
+</ul>
+<p>继续向底层深入，就会看到<code>Unsafe</code>类中的一些其他方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Unsafe</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapObject</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">var5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">compareAndSwapLong</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var4</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>对应查看<code>openjdk</code>的<code>hotspot</code>源码，<code>src/share/vm/prims/unsafe.cpp</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">#define FN_PTR(f) CAST_FROM_FN_PTR(void*, &amp;f)
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapObject&#34;, CC&#34;(&#34;OBJ&#34;J&#34;OBJ&#34;&#34;OBJ&#34;)Z&#34;,  FN_PTR(Unsafe_CompareAndSwapObject)},
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapInt&#34;,  CC&#34;(&#34;OBJ&#34;J&#34;&#34;I&#34;&#34;I&#34;&#34;)Z&#34;,      FN_PTR(Unsafe_CompareAndSwapInt)},
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">{CC&#34;compareAndSwapLong&#34;, CC&#34;(&#34;OBJ&#34;J&#34;&#34;J&#34;&#34;J&#34;&#34;)Z&#34;,      FN_PTR(Unsafe_CompareAndSwapLong)},
+</span></span></code></pre></div><p>最终在<code>hotspot</code>源码实现<code>/src/share/vm/runtime/Atomic.cpp</code>中都会调用统一的<code>cmpxchg</code>函数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-cpp" data-lang="cpp"><span class="line"><span class="cl"><span class="n">jbyte</span> <span class="n">Atomic</span><span class="o">::</span><span class="n">cmpxchg</span><span class="p">(</span><span class="n">jbyte</span> <span class="n">exchange_value</span><span class="p">,</span> <span class="k">volatile</span> <span class="n">jbyte</span><span class="o">*</span><span class="n">dest</span><span class="p">,</span> <span class="n">jbyte</span> <span class="n">compare_value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">     <span class="n">assert</span> <span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="n">jbyte</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span><span class="p">,</span><span class="s">&#34;assumption.&#34;</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="n">uintptr_t</span> <span class="n">dest_addr</span> <span class="o">=</span> <span class="p">(</span><span class="n">uintptr_t</span><span class="p">)</span> <span class="n">dest</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">uintptr_t</span> <span class="n">offset</span> <span class="o">=</span> <span class="n">dest_addr</span> <span class="o">%</span> <span class="k">sizeof</span><span class="p">(</span><span class="n">jint</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="k">volatile</span> <span class="n">jint</span><span class="o">*</span><span class="n">dest_int</span> <span class="o">=</span> <span class="p">(</span> <span class="k">volatile</span> <span class="n">jint</span><span class="o">*</span><span class="p">)(</span><span class="n">dest_addr</span> <span class="o">-</span> <span class="n">offset</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 对象当前值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jint</span> <span class="n">cur</span> <span class="o">=</span> <span class="o">*</span><span class="n">dest_int</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 当前值cur的地址
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jbyte</span> <span class="o">*</span> <span class="n">cur_as_bytes</span> <span class="o">=</span> <span class="p">(</span><span class="n">jbyte</span> <span class="o">*</span><span class="p">)</span> <span class="p">(</span> <span class="o">&amp;</span> <span class="n">cur</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// new_val地址
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">jint</span> <span class="n">new_val</span> <span class="o">=</span> <span class="n">cur</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="n">jbyte</span> <span class="o">*</span> <span class="n">new_val_as_bytes</span> <span class="o">=</span> <span class="p">(</span><span class="n">jbyte</span> <span class="o">*</span><span class="p">)</span> <span class="p">(</span> <span class="o">&amp;</span> <span class="n">new_val</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">      <span class="c1">// new_val存exchange_value，后面修改则直接从new_val中取值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="n">new_val_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">=</span> <span class="n">exchange_value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 比较当前值与期望值，如果相同则更新，不同则直接返回
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="k">while</span> <span class="p">(</span><span class="n">cur_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">==</span> <span class="n">compare_value</span><span class="p">)</span> <span class="p">{</span>
+</span></span><span class="line"><span class="cl">      <span class="c1">// 调用汇编指令cmpxchg执行CAS操作，期望值为cur，更新值为new_val
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>         <span class="n">jint</span> <span class="n">res</span> <span class="o">=</span> <span class="n">cmpxchg</span><span class="p">(</span><span class="n">new_val</span><span class="p">,</span> <span class="n">dest_int</span><span class="p">,</span> <span class="n">cur</span><span class="p">);</span>
+</span></span><span class="line"><span class="cl">         <span class="k">if</span> <span class="p">(</span><span class="n">res</span> <span class="o">==</span> <span class="n">cur</span><span class="p">)</span> <span class="k">break</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">cur</span> <span class="o">=</span> <span class="n">res</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">new_val</span> <span class="o">=</span> <span class="n">cur</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">         <span class="n">new_val_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">]</span> <span class="o">=</span> <span class="n">exchange_value</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">     <span class="p">}</span>
+</span></span><span class="line"><span class="cl">     <span class="c1">// 返回当前值
+</span></span></span><span class="line"><span class="cl"><span class="c1"></span>     <span class="k">return</span> <span class="n">cur_as_bytes</span><span class="p">[</span><span class="n">offset</span><span class="p">];</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span></code></pre></div><p>从上述源码可以看出CAS操作通过CPU提供的原子指令<code>cmpxchg</code>来实现无锁操作，这个指令会保证在多个处理器同时访问和修改数据时的正确性。</p>
+<p>CPU处理器速度远远大于在主内存中的速度，为了加快访问速度，现代CPU引入了多级缓存，如L1、L2、L3 级别的缓存，这些缓存离CPU越近就越快。
+这些缓存存储了频繁使用的数据，但在多处理器环境中，缓存的一致性成为了下一个问题。
+当CPU中某个处理器对缓存中的共享变量进行了操作后，其他处理器会有个嗅探机制。即将其他处理器共享变量的缓存失效，当其他线程读取时会重新从主内存中读取最新的数据，这是基于<code>MESI</code>缓存一致性协议来实现的。</p>
+<p>在多线程环境中，CAS就是比较当前线程工作内存中的值和主内存中的值，如果相同则执行规定操作，否则继续比较，直到主内存和当前线程工作内存中的值一致为止。
+每个CPU核心都有自己的缓存，用于存储频繁访问的数据。当一个线程在某个CPU核心上修改了共享变量的值时，其他CPU核心上缓存中的该变量会被标记为无效，这样其他线程再访问该变量时就会重新从主内存中获取最新值，从而保证了数据的一致性。
+CAS操作通过CPU提供的原子指令<code>cmpxchg</code>来比较和交换变量的值，它的原子性和线程安全性依赖于CPU的硬件支持和缓存一致性协议的保障。</p>
+<p><img alt="CPU多级缓存" src="/iblog/posts/annex/images/essays/CPU%E5%A4%9A%E7%BA%A7%E7%BC%93%E5%AD%98.jpg"></p>
+<p>所以当执行CAS方法时，读取变量当前的值，并与预期值进行比较。如果变量的当前值等于预期值，则将其更新为新值。如果变量的当前值不等于预期值，则不执行更新操作。
+注意CAS操作是原子的，即整个过程不会被其他线程打断。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="cas问题">CAS问题</h3>
+<ul>
+<li>循环时间长开销：CAS操作在失败时会进行自旋重试，即反复尝试CAS操作直到成功或达到一定的重试次数。自旋次数过多可能会影响性能，因此在使用CAS时需要权衡自旋次数和性能之间的关系。
+例如<code>getAndAddInt</code>方法执行，如果CAS失败会一直会进行尝试，如果CAS长时间不成功，可能会给CPU带来很大的开销。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getAndAddInt</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var4</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">getIntVolatile</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="o">!</span><span class="k">this</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">var2</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="p">,</span><span class="w"> </span><span class="n">var5</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">var4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">var5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>原子性问题：CAS操作本身是原子的，即在执行过程中不会被中断。但需要注意的是，CAS操作是针对单个变量的原子操作，而对于判断某个变量的值并根据结果进行另外的操作，需要额外的控制确保整体的原子性。
+这个时候就可以用锁来保证原子性，但是Java从1.5开始JDK提供了<code>AtomicReference</code>类来保证引用对象之间的原子性，可以把多个变量放在一个对象里来进行CAS操作。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AtomicReferenceSimpleExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DataObject</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">var2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">public</span><span class="w"> </span><span class="nf">DataObject</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">var2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 AtomicReference 实例，并初始化为一个 DataObject 对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicReference</span><span class="o">&lt;</span><span class="n">DataObject</span><span class="o">&gt;</span><span class="w"> </span><span class="n">atomicRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">DataObject</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Initial&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行 CAS 操作，修改 DataObject 对象的属性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">updateAndGet</span><span class="p">(</span><span class="n">data</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="p">.</span><span class="na">setVar1</span><span class="p">(</span><span class="n">data</span><span class="p">.</span><span class="na">getVar1</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">data</span><span class="p">.</span><span class="na">setVar2</span><span class="p">(</span><span class="s">&#34;Updated&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">data</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取修改后的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DataObject</span><span class="w"> </span><span class="n">updatedObject</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Updated var1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">updatedObject</span><span class="p">.</span><span class="na">getVar1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Updated var2: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">updatedObject</span><span class="p">.</span><span class="na">getVar2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>ABA问题：ABA问题指的是，在CAS操作过程中，如果一个变量的值从A变成了B，然后再变回A，那么CAS操作会错误地认为变量的值未改变过。
+比如，线程1从内存位置V取出A，线程2同时也从内存取出A，并且线程2进行一些操作将值改为B，然后线程2又将V位置数据改成A，这时候线程1进行CAS操作发现内存中的值依然时A，然后线程1操作成功。尽管线程1的CAS操作成功，但是不代表这个过程没有问题。
+简而言之就是只比较结果，不比较过程。解决ABA问题的常见方法是使用版本号或者标记来跟踪变量的变化。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ABASolutionWithVersion</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 初始值为100，初始版本号为0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AtomicStampedReference</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">atomicRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicStampedReference</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">100</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">stampHolder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// 用于获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">expectedValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w"> </span><span class="c1">// 期望值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">newValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">200</span><span class="p">;</span><span class="w"> </span><span class="c1">// 新值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟一个线程进行 ABA 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">getStamp</span><span class="p">();</span><span class="w"> </span><span class="c1">// 获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// 修改值和版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 再次修改回原值和新版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 其他线程进行 CAS 操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">getStamp</span><span class="p">();</span><span class="w"> </span><span class="c1">// 获取当前版本号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atomicRef</span><span class="p">.</span><span class="na">compareAndSet</span><span class="p">(</span><span class="n">expectedValue</span><span class="p">,</span><span class="w"> </span><span class="n">newValue</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="p">,</span><span class="w"> </span><span class="n">stamp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;CAS Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出CAS操作结果</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h2 id="juc包">J.U.C.包</h2>
+<p><code>java.util.concurrent</code>，简称 J.U.C.。是Java并发工具包，提供了在多线程编程中常用的工具类和框架，帮助开发者简化并发编程的复杂性，并提高程序的性能和可靠性。</p>
+<p><code>java.util.concurrent.locks</code>包下常用的类与接口是<code>JDK1.5</code>后新增的。<code>lock</code>的出现是为了弥补<code>synchronized</code>关键字解决不了的一些问题。
+例如，当一个代码块被<code>synchronized</code>修饰了，一个线程获取了对应的锁，并执行该代码块时，其他线程只能一直等待，等待获取锁的线程释放锁。
+如果这个线程因为某些原因被堵塞了，没有释放锁，那么其他线程只能一直等待下去，导致效率很低。
+因此就需要有一种机制可以不让等待的线程一直无期限地等待下去，比如只等待一定的时间或者能够响应中断，通过<code>Lock</code>就可以办到。</p>
+<p><code>java.util.concurrent</code>包中的锁在<code>locks</code>包下：</p>
+<p><img alt="juc.locks" src="/iblog/posts/annex/images/essays/juc.locks.png"></p>
+<p><code>Lock</code>和<code>ReadWriteLock</code>是两大锁的根接口，<code>Lock</code>代表实现类是<code>ReentrantLock</code>，<code>ReadWriteLock</code>的代表实现类是<code>ReentrantReadWriteLock</code>。</p>
+<p>除了锁之外，<code>java.util.concurrent</code>包还提供了一些其他的工具类和框架，如<code>Semaphore</code>、<code>CountDownLatch</code>、<code>CyclicBarrier</code>等。</p>
+<h3 id="lock">Lock</h3>
+<p><code>Lock</code>接口在Java的<code>java.util.concurrent.locks</code>包中定义，用于实现更灵活的线程同步机制。与传统的 <code>synchronized</code> 关键字相比，<code>Lock</code>接口提供了更多的操作和更细粒度的控制。
+在实际使用中，自然是能够替代<code>synchronized</code>关键字的。</p>
+<p><code>Lock</code>接口中的方法：</p>
+<ul>
+<li><code>lock()</code>：<code>lock()</code>方法是平常使用得最多的一个方法，就是用来获取锁。如果锁已经被另一个线程持有，则当前线程将会被阻塞，直到锁被释放。
+如果使用<code>lock</code>方法必须主动去释放锁，并且在发生异常时，不会自动释放锁。因此使用<code>Lock</code>必须在<code>try-catch</code>块中进行，并且将释放锁的操作放在<code>finally</code>块中进行，以保证锁一定被被释放，防止死锁的发生。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>lockInterruptibly()</code>：获取锁，但与<code>lock()</code>方法不同，它允许线程在等待获取锁的过程中被中断。
+例如，当两个线程同时通过<code>lock.lockInterruptibly()</code>想获取某个锁时，如果此时线程A获取到了锁，而线程B在等待，那么对线程B调用<code>threadB.interrupt()</code>能够中断线程B的等待过程。
+当一个线程获取了锁之后，是不会被<code>interrupt()</code>方法中断的。因为<code>interrupt()</code>方法只能中断阻塞过程中的线程而不能中断正在运行过程中的线程。与 <code>synchronized</code> 相比，当一个线程处于等待某个锁的状态，是无法被中断的，只有一直等待下去。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">LockInterruptiblyExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lockInterruptibly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LockInterruptiblyExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LockInterruptiblyExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; was interrupted.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">interrupt</span><span class="p">();</span><span class="w"> </span><span class="c1">// Interrupt the second thread</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>trylock()</code>：该方法的作用是尝试获取锁，如果锁可用则返回<code>true</code>，不可用则返回<code>false</code>。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TryLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">.</span><span class="na">tryLock</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; could not acquire the lock.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TryLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TryLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">example</span><span class="p">::</span><span class="n">increment</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>newCondition</code>：<code>Lock</code>接口提供了方法<code>Condition newCondition();</code>，返回的<code>Condition</code>类型也是一个接口，<code>Condition</code>提供了更细粒度的线程通信控制，用于实现复杂的线程间协作。
+类似于<code>Object</code>类中的<code>wait()</code>、<code>notify()</code>和<code>notifyAll()</code>方法。
+<ul>
+<li><code>await()</code>：当前线程等待，直到被通知或被中断。</li>
+<li><code>signal()</code>：唤醒一个等待线程。如果所有线程都在等待，则任意选择一个线程唤醒。</li>
+<li><code>signalAll()</code>：唤醒所有等待线程。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConditionExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Condition</span><span class="w"> </span><span class="n">condition</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lock</span><span class="p">.</span><span class="na">newCondition</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">counter</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="n">condition</span><span class="p">.</span><span class="na">await</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">condition</span><span class="p">.</span><span class="na">signal</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">reset</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">condition</span><span class="p">.</span><span class="na">signal</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">ConditionExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConditionExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Runnable</span><span class="w"> </span><span class="n">incrementTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">example</span><span class="p">::</span><span class="n">increment</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Runnable</span><span class="w"> </span><span class="n">resetTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">example</span><span class="p">::</span><span class="n">reset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">incrementTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">resetTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="readwritelock">ReadWriteLock</h3>
+<p><code>ReadWriteLock</code>接口提供了一种用于在某些情况下可以显著提升并发性能的锁定机制。
+它允许多个读线程同时访问共享资源，但对写线程使用排他锁，这样读操作不会互相阻塞，而写操作会阻塞所有其他操作。</p>
+<p>该接口有两个方法：</p>
+<ul>
+<li><code>readLock()</code>：返回用于读取操作的锁。</li>
+<li><code>writeLock()</code>：返回用于写入操作的锁。</li>
+</ul>
+<p><code>ReadWriteLock</code>管理一组锁，一个是只读的锁，一个是写锁。Java并发库中<code>ReetrantReadWriteLock</code>实现了<code>ReadWriteLock</code>接口并添加了可重入的特性。
+对于<code>ReetrantReadWriteLock</code>其读锁是共享锁而写锁是独占锁，读锁的共享可保证并发读是非常高效的。需要注意的是，读写、写读、写写的过程是互斥的，只有读读不是互斥的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReadWriteLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReadWriteLock</span><span class="w"> </span><span class="n">readWriteLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantReadWriteLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">readLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">readWriteLock</span><span class="p">.</span><span class="na">readLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Lock</span><span class="w"> </span><span class="n">writeLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">readWriteLock</span><span class="p">.</span><span class="na">writeLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 读操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">readValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">readLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; Reading: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">readLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 写操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">writeValue</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">writeLock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; Writing: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">writeLock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReadWriteLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReadWriteLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">readTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">readValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">100</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟读取时间</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">writeTask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">writeValue</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">150</span><span class="p">);</span><span class="w"> </span><span class="c1">// 模拟写入时间</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">readTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">readTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">writeTask</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread3</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="locksupport">LockSupport</h3>
+<p><code>LockSupport</code>是<code>java.util.concurrent.locks</code>包下的一个工具类。它提供了最基本的线程阻塞和解除阻塞的功能，通常用来构建更高级的同步机制。
+其中有两个重要的方法，通过<code>park()</code>和<code>unpark()</code>方法来实现阻塞和唤醒线程的操作，可以理解为<code>wait()</code>和<code>notify()</code>的加强版。</p>
+<ul>
+<li><code>park()</code>：阻塞当前线程，直到线程被其他线程中断或调用<code>unpark()</code>方法唤醒。</li>
+<li><code>unpark()</code>：唤醒指定线程。如果该线程尚未阻塞，则下一次调用<code>park()</code>方法时不会阻塞。</li>
+</ul>
+<p>传统等待唤醒机制是使用<code>Object</code>中的<code>wait()</code>方法让线程等待，使用<code>Object</code>中的<code>notify()</code>方法唤醒线程。
+或者使用JUC包中<code>Condition</code>的<code>await()</code>方法让线程等待，使用<code>signal()</code>方法唤醒线程。</p>
+<p><code>wait()</code>和<code>notify()</code>/<code>await()</code>和<code>signal()</code>方法必须要在同步块或同步方法里且成对出现使用，如果没有在<code>synchronized</code>代码块使用则抛出<code>java.lang.IllegalMonitorStateException</code>。
+必须先<code>wait()</code>/<code>await()</code>后<code>notify()</code>/<code>signal()</code>，如果先<code>notify()</code>后<code>wait()</code>会出现另一个线程一直处于等待状态。</p>
+<p><code>LockSupport</code>对比传统等待唤醒机制，能够解决传统等待唤醒问题。
+<code>LockSupport</code>使用的是许可机制，而<code>wait/notify</code>使用的是监视器机制。每个线程最多只有一个许可，调用<code>park()</code>会消耗一个许可，如果有许可则会直接消耗这张许可然后退出，如果没有许可就堵塞等待许可可用。
+调用<code>unpark()</code>则会增加一个许可，连续调用多次<code>unpark()</code>和调用一次一样，只会增加一个许可。而且<code>LockSupport</code>的<code>park()</code>和<code>unpark()</code>是可中断的，且无需在同步块中使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">LockSupportProducerConsumer</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">consumer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Consumer waiting for resource&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">resource</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">LockSupport</span><span class="p">.</span><span class="na">park</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Consumer consumed resource&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">producer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">2000</span><span class="p">);</span><span class="w"> </span><span class="c1">// Simulate some work with sleep</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">resource</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Producer produced resource&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">LockSupport</span><span class="p">.</span><span class="na">unpark</span><span class="p">(</span><span class="n">consumer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">consumer</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">producer</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>LockSupport</code>类使用了一种名为<code>Permit</code>的概念来做到阻塞和唤醒线程的功能，每个线程都有一个<code>Permit</code>，<code>Permit</code>只有两个值1和0，默认是0。
+官网解释<code>LockSupport</code>是用来创建锁和同步其他类的基本线程的阻塞原语。<code>LockSupport</code>最终调用的<code>Unsafe</code>中的<code>native</code>方法。以<code>unpark、park</code>为例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unpark</span><span class="p">(</span><span class="n">Thread</span><span class="w"> </span><span class="n">thread</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">thread</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">unpark</span><span class="p">(</span><span class="n">thread</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">park</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">blocker</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">setBlocker</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">blocker</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">park</span><span class="p">(</span><span class="kc">false</span><span class="p">,</span><span class="w"> </span><span class="n">0L</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">setBlocker</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="aqs">AQS</h3>
+<p>AQS是指<code>java.util.concurrent.locks</code>包下的一个抽象类<code>AbstractQueuedSynchronizer</code>译为，抽象的队列<strong>同步器</strong>。</p>
+<blockquote>
+<p>同步器是在多线程编程中用于管理线程间协作和同步的机制。同步器通常用于协调线程的执行顺序、控制共享资源的访问以及管理线程的状态。常见的同步器包括：CountDownLatch、CyclicBarrier、Semaphore等。</p>
+</blockquote>
+<p>在JUC包下，能够看到有许多类都继承了AQS，如<code>ReentrantLock</code>、<code>CountDownLatch</code>、<code>ReentrantReadWriteLock</code>、<code>Semaphore</code>。</p>
+<p><img alt="JUC.locks包UML" src="/iblog/posts/annex/images/essays/JUC.locks%E5%8C%85UML.png"></p>
+<p>AQS是用来构建锁或其它同步器组件的重要基础框架，以及是整个JUC体系的基石，它用于实现依赖先进先出队列的阻塞锁和相关的同步器。
+AQS提供了一个框架，用于创建在等待队列中具有独占或共享模式的同步器。</p>
+<p><img alt="AQS" src="/iblog/posts/annex/images/essays/AQS.png"></p>
+<p>AQS可以理解为一个框架，因为它定义了一些JUC包下常用&quot;锁&quot;的标准。
+AQS简单来说，包含一个<code>status</code>和一个队列。<code>status</code>保存线程持有锁的状态，用于判断该线程获没获取到锁，没获取到锁就去队列中排队。
+AQS中的队列，是指CLH队列（Craig， Landin， and Hagerste[三个人名组成]）锁队列的变体，是一个双向队列。
+队列中的元素即<code>Node</code>结点，每个<code>Node</code>中包含：头结点、尾结点、等待状态、存放的线程等。<code>Node</code>遵循从尾部入队，从头部出队的规则，即先进先出原则。</p>
+<p><img alt="AQS简单理解" src="/iblog/posts/annex/images/essays/AQS%E7%AE%80%E5%8D%95%E7%90%86%E8%A7%A3.png"></p>
+<p>在多线程并发环境下，使用<code>lock</code>加锁，当处在加锁与解锁之间的代码，只能有一个线程来执行。这时候其他线程不能够获取锁，如果不处理线程就会造成了堵塞。
+在AQS框架中，会将暂时获取不到锁的线程加入到队列里，这个队列就是AQS的抽象表现。它会将这些线程封装成队列的结点，通过CAS、自旋以及<code>LockSupport.park()</code>的方式，维护<code>state</code>变量的状态，使并发达到同步的效果。</p>
+<h3 id="reentrantlock">ReentrantLock</h3>
+<p><code>ReentrantLock</code>译为可重入锁，是一种锁的实现类，它提供了比<code>synchronized</code>关键字更广泛的锁定操作选项，提供了公平锁和非公平锁两种模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReentrantLockExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increment</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">counter</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; incremented counter to &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReentrantLockExample</span><span class="w"> </span><span class="n">example</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLockExample</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">example</span><span class="p">.</span><span class="na">increment</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">100</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="对比synchronized">对比synchronized</h4>
+<p>Java提供了两种锁机制来控制多个线程对共享资源的互斥访问，第一个是JVM实现的 <code>synchronized</code>，而另一个是 JDK 实现的 <code>ReentrantLock</code>。</p>
+<table>
+<thead>
+<tr>
+<th>比较</th>
+<th>synchronized</th>
+<th>ReentrantLock</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>锁的实现</td>
+<td>JVM实现</td>
+<td>JDK实现</td>
+</tr>
+<tr>
+<td>性能</td>
+<td>synchronized 与 ReentrantLock 大致相同</td>
+<td>synchronized 与 ReentrantLock 大致相同</td>
+</tr>
+<tr>
+<td>等待可中断</td>
+<td>不可中断</td>
+<td>可中断</td>
+</tr>
+<tr>
+<td>公平锁</td>
+<td>非公平锁</td>
+<td>默认非公平锁，也可以是公平锁</td>
+</tr>
+<tr>
+<td>锁绑定多个条件</td>
+<td>不能绑定</td>
+<td>可以同时绑定多个Condition对象</td>
+</tr>
+<tr>
+<td>可重入</td>
+<td>可重入锁</td>
+<td>可重入锁</td>
+</tr>
+<tr>
+<td>释放锁</td>
+<td>自动释放锁</td>
+<td>调用 unlock() 释放锁</td>
+</tr>
+<tr>
+<td>等待唤醒</td>
+<td>搭配wait()、notify或notifyAll()使用</td>
+<td>搭配await()/singal()使用</td>
+</tr>
+</tbody>
+</table>
+<p><code>synchronized</code>与<code>ReentrantLock</code>最直观的区别就是，在使用<code>ReentrantLock</code>的时候需要调用<code>unlock</code>方法释放锁，所以为了保证一定释放，通常都是和 <code>try-finally</code> 配合使用的。
+在实际开发中除非需要使用<code>ReentrantLock</code>的高级功能，否则优先使用<code>synchronized</code>。
+这是因为<code>synchronized</code>是JVM实现的一种锁机制，JVM原生地支持它，而<code>ReentrantLock</code>不是所有的JDK版本都支持。并且使用<code>synchronized</code>不用担心没有释放锁而导致死锁问题，因为JVM会确保锁的释放。</p>
+<h4 id="加锁原理">加锁原理</h4>
+<p><code>ReentrantLock</code>原理用到了AQS，而AQS包括一个线程队列和一个<code>state</code>变量，<code>state</code>，它的值有3种状态：没占用是0，占用了是1，大于1是可重入锁。
+所以<code>ReentrantLock</code>加锁过程，可以简单理解为<code>state</code>变量的变化。</p>
+<p>在多线程并发环境下，某个线程持有锁，将<code>state</code>由0设置为1，如果有其他线程再次进入，线程则会经过一系列判断，然后构建<code>Node</code>结点，最终形成双向链表结构。
+最后执行<code>LockSupport.park()</code>方法，将等待的线程挂起，如果当前持有锁的线程释放了锁，则将<code>state</code>变量设置为0，调用<code>LockSpoort.unpark()</code>方法指定唤醒等待队列中的某个线程。</p>
+<p><img alt="reentrantLock加锁" src="/iblog/posts/annex/images/essays/reentrantLock%E5%8A%A0%E9%94%81.png"></p>
+<p><code>ReentrantLock</code>加锁有两种形式，默认是非公平锁，但可以通过构造方法来指定为公平锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">reentrantLock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">//⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇⬇</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an instance of {@code ReentrantLock} with the
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * given fairness policy.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @param fair {@code true} if this lock should use a fair ordering policy
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">ReentrantLock</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">fair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">sync</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fair</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FairSync</span><span class="p">()</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NonfairSync</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>无论是公平锁还是非公平锁，由于用到了AQS框架，所以底层实现的逻辑大致是差不多的，<code>ReentrantLock</code>加锁核心方法调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">lock()
+</span></span><span class="line"><span class="cl">    --&gt; acquire()
+</span></span><span class="line"><span class="cl">    --&gt; tryAcquire()
+</span></span><span class="line"><span class="cl">    --&gt; addWaiter()
+</span></span><span class="line"><span class="cl">    --&gt; acquireQueued()
+</span></span><span class="line"><span class="cl">    --&gt; selfInterrupt()
+</span></span></code></pre></div><p>公平锁还是非公平锁虽然大致逻辑差不多，但是区别总是有的，总的来说非公平锁比非公平锁在代码里面多了几行判断。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// ===========重写 lock 方法对比===========</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">lock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">acquire</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 非公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">lock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetState</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setExclusiveOwnerThread</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquire</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">acquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">tryAcquire</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquireQueued</span><span class="p">(</span><span class="n">addWaiter</span><span class="p">(</span><span class="n">Node</span><span class="p">.</span><span class="na">EXCLUSIVE</span><span class="p">),</span><span class="w"> </span><span class="n">arg</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">selfInterrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// ===========重写 tryAcquire 方法对比===========</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">protected</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">tryAcquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">acquires</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">c</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">hasQueuedPredecessors</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">compareAndSetState</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">acquires</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setExclusiveOwnerThread</span><span class="p">(</span><span class="n">current</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">current</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">getExclusiveOwnerThread</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">nextc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">acquires</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nextc</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="s">&#34;Maximum lock count exceeded&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">setState</span><span class="p">(</span><span class="n">nextc</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 非公平锁</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">protected</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">tryAcquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">acquires</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">nonfairTryAcquire</span><span class="p">(</span><span class="n">acquires</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">nonfairTryAcquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">acquires</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="n">current</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">c</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetState</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">acquires</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setExclusiveOwnerThread</span><span class="p">(</span><span class="n">current</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">current</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">getExclusiveOwnerThread</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">nextc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">acquires</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">nextc</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="c1">// overflow</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Error</span><span class="p">(</span><span class="s">&#34;Maximum lock count exceeded&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">setState</span><span class="p">(</span><span class="n">nextc</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在重写的<code>tryAcquire</code>方法里，公平锁在获取同步状态时多了一个限制条件即<code>hasQueuedPredecessors()</code>方法。该方法作用是保证等待队列中的线程按照从头到尾的顺序排队获取锁。
+举个例子，目前队列中有两个线程A、B，线程A，在线程B的前面。在当前线程释放锁的时候，线程B获取到了锁，该方法会判断当前头结点的下一个结点中存放的线程跟当前线程是否相同。
+在这个例子中头结点的下一个结点存放的线程是傀儡结点线程为<code>null</code>，而当前线程是线程B，所以返回<code>true</code>，回到上一个方法<code>true</code>取反就是<code>false</code>所以获取锁失败。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">hasQueuedPredecessors</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// The correctness of this depends on head being initialized</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// before tail and on head.next being accurate if the current</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// thread is first in queue.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">;</span><span class="w"> </span><span class="c1">// Read fields in reverse initialization order</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">s</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">((</span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">h</span><span class="p">.</span><span class="na">next</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">thread</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在执行完<code>tryAcquire</code>方法之后就会执行<code>addWaiter</code>方法。
+<code>addWaiter</code>方法作用为，当第一次将等待的线程添加到队列时，先会调用<code>enq</code>方法。
+如果不是第一次调用，即尾结点不为空，队列中已经有了其他线程结点，则会直接将当前线程的前结点指向尾结点，即队列中最后一个线程结点。
+然后用CAS将前一个结点的下一个结点指向当前结点，形成链表结构，最后返回添加到队列中的结点。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">addWaiter</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">mode</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">(),</span><span class="w"> </span><span class="n">mode</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Try the fast path of enq; backup to full enq on failure</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">pred</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pred</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">node</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pred</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetTail</span><span class="p">(</span><span class="n">pred</span><span class="p">,</span><span class="w"> </span><span class="n">node</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">pred</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">enq</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>enq</code>方法作用是将等待获取锁的线程封装成<code>Node</code>结点，并将<code>Node</code>结点串联起来，形成双向链表结构，简而言之就是将线程添加到等待队列中去。                                                                <br>
+该方法运用自旋机制，如果添加的结点为第一个结点，则会在第一个实际结点之前，生成一个“傀儡结点”。添加的第一个结点的前结点指向傀儡结点，尾结点指向实际结点。傀儡结点的后结点则指向添加的第一个结点。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="nf">enq</span><span class="p">(</span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(;;)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">t</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// Must initialize</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetHead</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Node</span><span class="p">()))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">tail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">t</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">compareAndSetTail</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">node</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">t</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">t</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>之后执行<code>acquireQueued</code>方法，该方法用到了自旋机制。首先判断当前结点是否为头结点，如果是头结点，就让头结点中的线程尝试获取锁。
+如果不是头结点，执行<code>shouldParkAfterFailedAcquire</code>方法尝试让当前线程挂起，直到持有锁的线程释放锁，唤醒等待的线程之后再去尝试获取锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">acquireQueued</span><span class="p">(</span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">failed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">interrupted</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(;;)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">final</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">predecessor</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">p</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">tryAcquire</span><span class="p">(</span><span class="n">arg</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">setHead</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">p</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span><span class="c1">// help GC</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">failed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">interrupted</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">shouldParkAfterFailedAcquire</span><span class="p">(</span><span class="n">p</span><span class="p">,</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">parkAndCheckInterrupt</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">interrupted</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">failed</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">cancelAcquire</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>shouldParkAfterFailedAcquire</code>方法，该方法首先判断上一个结点的<code>waitStatus</code>。
+如果该队列只有一个结点，则上一个结点为头结点，此时头结点的<code>waitStatus=0</code>，经过该方法会将上一个结点的<code>waitStatus</code>通过CAS，设置为-1。
+因为最外部是一个自旋机制，会一直循环，所以当第二次进入该方法，则会直接返回<code>true</code>。返回<code>true</code>意味着当前线程将进入堵塞状态，会执行<code>parkAndCheckInterrupt()</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">shouldParkAfterFailedAcquire</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">pred</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">ws</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pred</span><span class="p">.</span><span class="na">waitStatus</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ws</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Node</span><span class="p">.</span><span class="na">SIGNAL</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ws</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pred</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pred</span><span class="p">.</span><span class="na">prev</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">pred</span><span class="p">.</span><span class="na">waitStatus</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pred</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">compareAndSetWaitStatus</span><span class="p">(</span><span class="n">pred</span><span class="p">,</span><span class="w"> </span><span class="n">ws</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p">.</span><span class="na">SIGNAL</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>parkAndCheckInterrupt</code>方法，底层是调用<code>LockSupport.park()</code>方法让线程挂起，直到持有锁的线程将它们唤醒。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">parkAndCheckInterrupt</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">LockSupport</span><span class="p">.</span><span class="na">park</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">interrupted</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ReentrantLock</code>其加锁核心方法为<code>acquire</code>方法。最终执行完毕，下面的<code>if</code>表达式返回<code>true</code>，则执行<code>selfInterrupt</code>方法中断线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">acquire</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">tryAcquire</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">acquireQueued</span><span class="p">(</span><span class="n">addWaiter</span><span class="p">(</span><span class="n">Node</span><span class="p">.</span><span class="na">EXCLUSIVE</span><span class="p">),</span><span class="w"> </span><span class="n">arg</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">selfInterrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ReentrantLock</code>在采用非公平锁构造时，首先检查锁状态，如果锁可用，直接通过CAS设置成持有状态，且把当前线程设置为锁的拥有者。
+如果当前锁已经被持有，那么接下来进行可重入检查，如果可重入，需要为锁状态加上请求数。如果不属于上面两种情况，那么说明锁是被其他线程持有，当前线程应该放入等待队列。</p>
+<p>在放入等待队列的过程中，首先要检查队列是否为空队列，如果为空队列，需要创建虚拟的头节点，然后把对当前线程封装的节点加入到队列尾部。
+由于设置尾部节点采用了CAS，为了保证尾节点能够设置成功，<code>ReentrantLock</code>采用了无限循环的方式，直到设置成功为止。</p>
+<p>在完成放入等待队列任务后，则需要维护节点的状态，以及及时清除处于<code>Cancel</code>状态的节点，来帮助垃圾收集器及时回收。
+如果当前节点之前的节点的等待状态小于1，说明当前节点之前的线程处于等待状态，那么当前节点的线程也应处于等待状态。通过<code>LockSupport</code>类实现等待挂起的功能。
+当等待的线程被唤起后，检查中断状态，如果处于中断状态，那么需要中断当前线程。</p>
+<h4 id="释放锁原理">释放锁原理</h4>
+<p><img alt="reentrantLock解锁" src="/iblog/posts/annex/images/essays/reentrantLock%E8%A7%A3%E9%94%81.png"></p>
+<p><code>ReentrantLock</code>释放锁调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">unlock()
+</span></span><span class="line"><span class="cl">    --&gt; release()
+</span></span><span class="line"><span class="cl">    --&gt; tryRelease()
+</span></span><span class="line"><span class="cl">    --&gt; unparkSuccessor()
+</span></span></code></pre></div><p>在<code>release</code>方法中如果<code>tryRelease</code>方法返回<code>true</code>，则判断队列头结点中的<code>waitStatus</code>，如果不等于0则执行<code>unparkSuccessor</code>方法，按顺序唤醒队列中等待的线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">release</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">arg</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">tryRelease</span><span class="p">(</span><span class="n">arg</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="w"> </span><span class="n">h</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">h</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">h</span><span class="p">.</span><span class="na">waitStatus</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">unparkSuccessor</span><span class="p">(</span><span class="n">h</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>tryRelease</code>方法作用是尝试释放锁，首先获取当前持有锁线程的<code>state</code>变量并使其减1。
+如果减1后的<code>state</code>值等于0，则认为该线程马上要释放锁，将当前持有锁的线程设置为<code>null</code>，将0设置为<code>state</code>的新值并返回<code>true</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">tryRelease</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">releases</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getState</span><span class="p">()</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">releases</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">getExclusiveOwnerThread</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalMonitorStateException</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">c</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">setExclusiveOwnerThread</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">setState</span><span class="p">(</span><span class="n">c</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">free</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>unparkSuccessor</code>方法用于唤醒等待队列中的后继节点。首先判断当前节点的等待状态如果小于0，将其设置为0。
+然后从尾部开始向前查找，直到找到一个有效的后继节点，如果找到一个有效的后继节点，唤醒其线程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">unparkSuccessor</span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">ws</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">waitStatus</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ws</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">compareAndSetWaitStatus</span><span class="p">(</span><span class="n">node</span><span class="p">,</span><span class="w"> </span><span class="n">ws</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Node</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">node</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">waitStatus</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Node</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tail</span><span class="p">;</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">t</span><span class="p">.</span><span class="na">prev</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">t</span><span class="p">.</span><span class="na">waitStatus</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">t</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LockSupport</span><span class="p">.</span><span class="na">unpark</span><span class="p">(</span><span class="n">s</span><span class="p">.</span><span class="na">thread</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="countdownlatch">CountDownLatch</h3>
+<p><code>count down latch</code>直译为倒计时门闩，也可以叫做闭锁。</p>
+<blockquote>
+<p>门闩，汉语词汇。拼音：mén shuān 释义：指门关上后，插在门内使门推不开的滑动插销。</p>
+</blockquote>
+<p><code>CountDownLatch</code>JDK文档注释：</p>
+<blockquote>
+<p>A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes.</p>
+</blockquote>
+<p>文档大意：一种同步辅助工具，允许一个或多个线程等待，直到在其他线程中执行的一组操作完成。</p>
+<p><code>CountDownLatch</code>是Java中的一个同步工具类，用于使一个或多个线程等待其他线程完成一组操作。<code>CountDownLatch</code>通过一个计数器实现，该计数器的初始值由构造方法指定，底层还是AQS。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="nf">CountDownLatch</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">count</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;count &lt; 0&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">this</span><span class="p">.</span><span class="na">sync</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Sync</span><span class="p">(</span><span class="n">count</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>每调用一次<code>countDown()</code>方法，计数器减一，当计数器到达零时，所有因调用<code>await()</code>方法而等待的线程都将被唤醒。
+举个例子，晚上教室关门，要等同学都离开之后，再关门：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CountDownLatch</span><span class="w"> </span><span class="n">countDownLatch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CountDownLatch</span><span class="p">(</span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">7</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;同学&#34;</span><span class="o">+</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;\t 离开&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">countDownLatch</span><span class="p">.</span><span class="na">countDown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">countDownLatch</span><span class="p">.</span><span class="na">await</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;关门...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="cyclicbarrier">CyclicBarrier</h3>
+<p><code>Cyclic Barrier</code>直译为循环屏障，是Java中关于线程的计数器，也可以叫它栅栏。</p>
+<p><code>CyclicBarrier</code>JDK文档注释：</p>
+<blockquote>
+<p>A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point.  CyclicBarriers are useful in programs involving a fixed sized party of threads that must occasionally wait for each other. The barrier is called <em>cyclic</em> because it can be re-used after the waiting threads are released.</p>
+</blockquote>
+<p>文档大意：一种同步辅助工具，允许一组线程相互等待到达一个共同的障碍点。<code>cyclicbarrier</code>在包含固定大小的线程组的程序中非常有用，这些线程必须偶尔相互等待。
+这个屏障被称为<code>cyclic</code>，因为它可以在等待的线程被释放后被重用。</p>
+<p>它与<code>CountDownLatch</code>的作用是相反的，<code>CountDownLatch</code>是定义一个次数，然后减直到减到0，再去执行一些任务。
+而<code>CyclicBarrier</code>是定义一个上限次数，从零开始加，直到加到定义的上限次数，再去执行一些任务。
+<code>CountDownLatch</code>的计数器只能使用一次，而<code>CyclicBarrier</code>的计数器可以使用<code>reset()</code>方法重置，可以使用多次，所以<code>CyclicBarrier</code>能够处理更为复杂的场景。
+例如，凑齐七颗龙珠召唤神龙：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CyclicBarrier</span><span class="w"> </span><span class="n">cyclicBarrier</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CyclicBarrier</span><span class="p">(</span><span class="n">7</span><span class="p">,()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;凑齐七颗龙珠，召唤神龙！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">7</span><span class="p">;</span><span class="n">i</span><span class="o">++</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;拿到&#34;</span><span class="o">+</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;星龙珠&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">cyclicBarrier</span><span class="p">.</span><span class="na">await</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">BrokenBarrierException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CyclicBarrier</code>要做的事情是，让一组线程达到一个屏障时被阻塞，直到最后一个线程达到屏障时，所有被屏障拦截的线程才会继续干活，线程进入屏障通过<code>CyclicBarrier.await()</code>方法。</p>
+<p><img alt="CyclicBarrier" src="/iblog/posts/annex/images/essays/CyclicBarrier.gif"></p>
+<p><code>CyclicBarrier</code>是基于<code>ReentrantLock</code>实现的，其底层也是基于AQS。
+<code>CyclicBarrier</code>通过一个内部的计数器和一个锁来实现线程间的协调。当所有线程都调用<code>await</code>方法时，计数器递减，当计数器为零时，所有等待的线程将被唤醒，并重置计数器，以便下一次使用。</p>
+<h3 id="semaphore">Semaphore</h3>
+<p><code>Semaphore</code>译为信号量，有时被称为信号灯。可以用来控制同时访问特定资源的线程数量，通过协调各个线程，保证合理的使用资源。
+信号量主要用于两个目的，一个是用于多个共享资源的互斥使用，另一个用于并发线程数量的控制。</p>
+<p><code>Semaphore</code>JDK文档注释：</p>
+<blockquote>
+<p>A counting semaphore.  Conceptually, a semaphore maintains a set of permits.  Each {@link #acquire} blocks if necessary until a permit is available, and then takes it.  Each {@link #release} adds a permit, potentially releasing a blocking acquirer.</p>
+</blockquote>
+<p>文档大意：<code>Semaphore</code>是一个计数信号量。从概念上讲，信号量维护一组许可。如果需要，每个<code>acquire</code>方法调用会阻塞，直到有一个许可可用，然后获取许可。
+每个<code>release</code>方法调用会添加一个许可，可能会释放一个阻塞的线程。实际上，<code>Semaphore</code>并没有维护实际的许可对象，只是维护一个可用许可的计数，并根据计数执行相应的操作。</p>
+<p>举个例子，九辆车抢三个车位，车位满了之后只有等里面的车离开停车场外面的车才可以进入。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Semaphore</span><span class="w"> </span><span class="n">semaphore</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Semaphore</span><span class="p">(</span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">9</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">semaphore</span><span class="p">.</span><span class="na">acquire</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;辆车，抢到车位&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">2000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;停车结束.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">semaphore</span><span class="p">.</span><span class="na">release</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Semaphore</code>通过一个计数器和一个队列来管理许可和等待线程。它依赖于AQS来实现同步逻辑。
+<code>Semaphore</code>是用来保护一个或者多个共享资源的访问，<code>Semaphore</code>内部维护了一个计数器，其值为可以访问的共享资源的个数。
+一个线程要访问共享资源，先获得信号量，如果信号量的计数器值大于1，意味着有共享资源可以访问，则使其计数器值减去1，再访问共享资源。
+如果计数器值为0，线程进入休眠。当某个线程使用完共享资源后，释放信号量，并将信号量内部的计数器加1，之前进入休眠的线程将被唤醒并再次试图获得信号量。</p>
+<p><code>Semaphore</code>的核心方法为：</p>
+<ul>
+<li><code>acquire()</code>：获取一个许可，如果没有可用的许可，当前线程将被阻塞，直到有许可可用。
+当调用<code>semaphore.acquire()</code>方法时，当前线程会尝试去同步队列获取一个令牌，获取令牌的过程也就是使用原子操作去修改同步队列的<code>state</code>，获取一个令牌则修改为<code>state=state-1</code>。
+当计算出来的<code>state&lt;0</code>，则代表令牌数量不足，此时会创建一个<code>Node</code>节点加入阻塞队列，挂起当前线程。当计算出来的<code>state&gt;=0</code>，则代表获取令牌成功。</li>
+<li><code>release()</code>：释放一个许可，将其返回到<code>Semaphore</code>。
+当调用<code>semaphore.release()</code>方法时，线程会尝试释放一个令牌，释放令牌的过程也就是把同步队列的<code>state</code>修改为<code>state=state+1</code>的过程。
+释放令牌成功之后，同时会唤醒同步队列中的一个线程。被唤醒的节点会重新尝试去修改<code>state=state-1</code>的操作，如果<code>state&gt;=0</code>则获取令牌成功，否则重新进入阻塞队列，挂起线程。</li>
+</ul>
+<h2 id="threadlocal">ThreadLocal</h2>
+<p><code>ThreadLocal</code>文档注释：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">This class provides thread-local variables.
+</span></span><span class="line"><span class="cl">These variables differ from their normal counterparts in that each thread that accesses one (via its {@code get} or {@code set} method) has its own,
+</span></span><span class="line"><span class="cl">independently initialized copy of the variable. 
+</span></span></code></pre></div><p>文档大意：这个类提供线程局部变量。这些变量与普通变量的不同之处在于，每个访问它们的线程(通过其get方法或set方法)都有自己的独立初始化的变量副本。</p>
+<p>如文档注释所说，<code>ThraedLocal</code>为每个使用该变量的线程提供独立的变量副本，所以每一个线程都可以独立地改变自己的副本，而不会影响其它线程所对应的副本。
+每个访问<code>ThreadLocal</code>变量的线程都有自己的隔离副本，这样防止了线程之间的干扰，消除了同步的需要。
+从线程的角度看，目标变量就象是线程的本地变量，这也是类名中“Local”所要表达的意思。说白了<code>ThreadLocal</code>就是存放线程的局部变量的。</p>
+<h3 id="对比线程同步">对比线程同步</h3>
+<p><code>ThreadLocal</code>是修饰变量的，重点是在控制变量的作用域，初衷不是为了解决线程并发和线程冲突的，而是为了让变量的种类变的更多更丰富，方便使用。很多开发语言在语言级别都提供这种作用域的变量类型。</p>
+<p>其实要保证线程安全，并不一定就是要进行同步，两者没有因果关系。同步只是保证共享数据竞争时的手段。如果一个方法本来就不涉及共享数据，那它自然就无需任何同步措施去保证正确性。
+线程安全，并不一定就是要进行同步，<code>ThreadLocal</code>目的是线程安全，但不是同步手段。</p>
+<p><code>ThreadLocal</code>和线程同步机制都可以解决多线程中共享变量的访问冲突问题。
+在同步机制中，通过对象的锁机制保证同一时间只有一个线程访问变量。使用同步机制要求程序谨慎地分析什么时候对变量进行读写，什么时候需要锁定某个对象，什么时候释放对象锁等繁杂的问题，程序设计和编写难度相对较大。
+而<code>ThreadLocal</code> 则从另一个角度来解决多线程的并发访问。<code>ThreadLocal</code>会为每一个线程提供一个独立的变量副本，从而隔离了多个线程对数据的访问冲突。因为每一个线程都拥有自己的变量副本，从而也就没有必要对该变量进行同步了。
+<code>ThreadLocal</code>提供了线程安全的共享对象，在编写多线程代码时，可以把不安全的变量封装进<code>ThreadLocal</code>。</p>
+<p>虽然<code>ThreadLocal</code>能够保证多线程访问数据安全，但是由于在每个线程中都创建了副本，所以要考虑它对资源的消耗，比如内存的占用会比不使用<code>ThreadLocal</code>要大。
+对于多线程资源共享的问题，同步机制采用了“以时间换空间”的方式，而<code>ThreadLocal</code>采用了“以空间换时间”的方式。前者仅提供一份变量，让不同的线程排队访问，而后者为每一个线程都提供了一份变量，因此可以同时访问而互不影响。</p>
+<h3 id="使用示例-2">使用示例</h3>
+<p>在JDK5.0中，<code>ThreadLocal</code>已经支持泛型，该类的类名已经变为<code>ThreadLocal&lt;T&gt;</code>。API方法也相应进行了调整，新版本的API方法分别是<code>void set(T value)</code>、<code>T get()</code>。</p>
+<p><code>ThreadLocal</code>中主要有三个方法：</p>
+<ul>
+<li><code>set()</code>：设置当前线程的线程局部变量的值。</li>
+<li><code>get()</code>：该方法返回当前线程所对应的线程局部变量。</li>
+<li><code>remove()</code>：删除当前线程的线程局部变量，目的是为了减少内存的占用。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ThreadLocalExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 创建一个 ThreadLocal 变量，用于存储每个线程独立的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ThreadLocal</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadLocal</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 设置线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="s">&#34;Thread-1&#39;s Value&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并打印线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 删除线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">remove</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; after remove: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 设置线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="s">&#34;Thread-2&#39;s Value&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并打印线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 删除线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">remove</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; after remove: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">threadLocalValue</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>除此之外，<code>ThreadLocal</code>提供了一个<code>withInitial()</code>方法统一初始化所有线程的<code>ThreadLocal</code>的值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ThreadLocalWithInitialExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 使用 withInitial 方法提供初始值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ThreadLocal</span><span class="o">&lt;</span><span class="n">SimpleDateFormat</span><span class="o">&gt;</span><span class="w"> </span><span class="n">dateFormat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ThreadLocal</span><span class="p">.</span><span class="na">withInitial</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SimpleDateFormat</span><span class="p">(</span><span class="s">&#34;yyyy-MM-dd&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并打印线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">SimpleDateFormat</span><span class="w"> </span><span class="n">df</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dateFormat</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">formattedDate</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">df</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">formattedDate</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 删除线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">dateFormat</span><span class="p">.</span><span class="na">remove</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Runnable</span><span class="w"> </span><span class="n">task2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并打印线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">SimpleDateFormat</span><span class="w"> </span><span class="n">df</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dateFormat</span><span class="p">.</span><span class="na">get</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">formattedDate</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">df</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">formattedDate</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 删除线程局部变量的值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">dateFormat</span><span class="p">.</span><span class="na">remove</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">thread2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(</span><span class="n">task2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">thread2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ThreadLocal</code>是一种强大的工具，适用于需要线程隔离的场景，如用户会话、数据库连接和格式化对象等。
+使用<code>ThreadLocal</code>可以有效地管理线程本地的数据，避免多线程环境下的竞争和数据一致性问题。
+但是由于<code>ThreadLocal</code>的生命周期与线程相关，如果在线程池中使用<code>ThreadLocal</code>，需要注意及时调用<code>remove()</code>方法清理线程局部变量，来防止内存泄漏。</p>
+<h3 id="实现原理-2">实现原理</h3>
+<p><code>ThreadLocal</code>类本身并不存储线程本地变量的值，而是通过<code>ThreadLocalMap</code>来实现。
+每个线程内部都有一个<code>ThreadLocalMap</code>实例，<code>ThreadLocal</code>变量作为<code>ThreadLocalMap</code>的键，存储的值是该线程对应的变量值。</p>
+<p><code>set</code>方法首先获取当前线程 <code>Thread</code> 对象，然后获取该线程的 <code>ThreadLocalMap</code> 实例。如果存在，则将值存储在 <code>ThreadLocalMap</code> 中；否则，创建一个新的 <code>ThreadLocalMap</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">set</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 每个线程 都有一个自己的ThreadLocalMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ThreadLocalMap 里就保存着所有的ThreadLocal变量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getMap</span><span class="p">(</span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 向map里添加值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// map为null，创建一个 ThreadLocalMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">createMap</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 全局定义的localMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">ThreadLocal</span><span class="p">.</span><span class="na">ThreadLocalMap</span><span class="w"> </span><span class="n">threadLocals</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 获取当前线程所持有的localMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="nf">getMap</span><span class="p">(</span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">t</span><span class="p">.</span><span class="na">threadLocals</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 创建，初始化 localMap </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">void</span><span class="w"> </span><span class="nf">createMap</span><span class="p">(</span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">firstValue</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">t</span><span class="p">.</span><span class="na">threadLocals</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ThreadLocalMap</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">firstValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>get</code>方法同样先获取当前线程 <code>Thread</code> 对象，然后获取该线程的 <code>ThreadLocalMap</code> 实例。再通过 <code>ThreadLocal</code> 对象作为键从 <code>ThreadLocalMap</code> 中获取值。如果键不存在，则调用 <code>setInitialValue</code> 方法初始化变量。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">get</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获取当前线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 每个线程 都有一个自己的ThreadLocalMap，</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// ThreadLocalMap里就保存着所有的ThreadLocal变量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getMap</span><span class="p">(</span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//ThreadLocalMap的key就是当前ThreadLocal对象实例，</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//多个ThreadLocal变量都是放在这个map中的</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ThreadLocalMap</span><span class="p">.</span><span class="na">Entry</span><span class="w"> </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">getEntry</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//从map里取出来的值就是我们需要的这个ThreadLocal变量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">T</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="p">)</span><span class="n">e</span><span class="p">.</span><span class="na">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果map没有初始化，那么在这里初始化一下</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">setInitialValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 全局定义的localMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">ThreadLocal</span><span class="p">.</span><span class="na">ThreadLocalMap</span><span class="w"> </span><span class="n">threadLocals</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 获取当前线程所持有的localMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="nf">getMap</span><span class="p">(</span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">t</span><span class="p">.</span><span class="na">threadLocals</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>setInitialValue</code> 方法通过 <code>initialValue</code> 方法获取初始值，并存储在 <code>ThreadLocalMap</code> 中。如果 <code>initialValue</code> 方法未被重写，默认返回 <code>null</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">setInitialValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">T</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">initialValue</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ThreadLocalMap</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getMap</span><span class="p">(</span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">map</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">map</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">createMap</span><span class="p">(</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">protected</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">initialValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ThreadLocalMap</code>是一个自定义的哈希表，其中每个元素是一个<code>Entry</code>对象。
+<code>ThreadLocalMap</code>是一个比较特殊的<code>Map</code>，它的每个<code>Entry</code>的<code>key</code>都是一个弱引用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Entry</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WeakReference</span><span class="o">&lt;</span><span class="n">ThreadLocal</span><span class="o">&lt;?&gt;&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The value associated with this ThreadLocal. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Object</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//key就是一个弱引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Entry</span><span class="p">(</span><span class="n">ThreadLocal</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">k</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">v</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">k</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">v</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这样设计的好处是，如果这个变量不再被其他对象使用时，可以自动回收这个<code>ThreadLocal</code>对象，避免可能的内存泄露。</p>
+<h3 id="内存泄漏问题">内存泄漏问题</h3>
+<p>虽然<code>ThreadLocalMap</code>中的<code>key</code>是弱引用，当不存在外部强引用的时候，就会自动被回收。但是<code>Entry</code>中的<code>value</code>依然是强引用，<code>value</code>的引用链条如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Thread --&gt; ThreadLocalMap --&gt; Entry --&gt; value
+</span></span></code></pre></div><p>只有当<code>Thread</code>被回收时，这个<code>value</code>才有被回收的机会，否则只要线程不退出，<code>value</code>总是会存在一个强引用。
+但是要求每个<code>Thread</code>都会退出，是一个极其苛刻的要求，对于线程池来说，大部分线程会一直存在在系统的整个生命周期内，那样的话就会造成<code>value</code>对象出现泄漏的可能。</p>
+<p>如果<code>get()</code>方法总是访问固定几个一直存在的<code>ThreadLocal</code>，那么清理动作就不会执行，如果你没有机会调用<code>set()</code>和<code>remove()</code>，那么这个内存泄漏依然会发生。
+所以当你不需要这个<code>ThreadLocal</code>变量时，主动调用<code>remove()</code>，这样是能够避免内存泄漏的。可以将<code>ThreadLocal</code>的使用和清理放在<code>try-finally</code>块中，确保<code>remove()</code>方法总是会被调用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">ThreadLocal&lt;MyClass&gt; threadLocal = new ThreadLocal&lt;&gt;();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    threadLocal.set(new MyClass());
+</span></span><span class="line"><span class="cl">    // 使用线程局部变量
+</span></span><span class="line"><span class="cl">} finally {
+</span></span><span class="line"><span class="cl">    threadLocal.remove();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>除此之外，应尽量避免将<code>ThreadLocal</code>对象声明为静态变量，特别是在应用服务器或类似环境中，因为它们的生命周期通常较长，会增加内存泄漏的风险。</p>
+<h2 id="常用线程安全的集合">常用线程安全的集合</h2>
+<p>在多线程环境中，数据的一致性和线程的安全性是至关重要的。传统的集合类，如<code>ArrayList</code>、<code>HashMap</code>和<code>HashSet</code>，在并发访问时并不安全，可能会导致数据不一致和其他并发问题。
+为了在并发编程中高效且安全地操作数据，Java提供了一系列线程安全的集合类来替代这些传统集合。</p>
+<table>
+<thead>
+<tr>
+<th>线程不安全</th>
+<th>线程安全替代</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>ArrayList</td>
+<td>CopyOnWriteArrayList</td>
+</tr>
+<tr>
+<td>HashSet</td>
+<td>CopyOnWriteArraySet</td>
+</tr>
+<tr>
+<td>HashMap</td>
+<td>HashTable、ConcurrentHashMap</td>
+</tr>
+</tbody>
+</table>
+<h3 id="copywritearraylist">CopyWriteArrayList</h3>
+<p><code>CopyOnWriteArrayList</code>是Java中的一种线程安全的<code>List</code>实现，适用于读操作远多于写操作的场景，该集合在线程不安全的情况下可替代<code>ArrayList</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrayList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">arrayList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">arrayList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">},</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">i</span><span class="p">)).</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CopyWriteArrayList</code>字面意思就是在写的时候复制，思想就是读写分离的思想。它的基本原理是每次修改操作都会创建该列表的一个新副本，因此读操作不需要加锁，可以并发执行。
+以下是<code>CopyOnWriteArrayList</code>的<code>add()</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The array, accessed only via getArray/setArray. */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** The lock protecting all mutators */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kd">transient</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Gets the array.  Non-private so as to also be accessible
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * from CopyOnWriteArraySet class.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="nf">getArray</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Appends the specified element to the end of this list.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param e element to be appended to this list
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return {@code true}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">E</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">ReentrantLock</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">lock</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lock</span><span class="p">.</span><span class="na">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">elements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">elements</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">newElements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">elements</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">newElements</span><span class="o">[</span><span class="n">len</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">setArray</span><span class="p">(</span><span class="n">newElements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">.</span><span class="na">unlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>CopyWriteArrayList</code>之所以线程安全的原因是在源码里面使用<code>ReentrantLock</code>保证了某个线程在写的时候不会被打断。
+可以看到源码开始先是复制了一份数组，同一时刻只有一个线程写，其余的线程会读。在复制的数组上边进行写操作，写好以后在返回<code>true</code>。
+这样就把读写进行了分离，写好以后因为<code>array</code>加了<code>volatile</code>修饰，所以该数组是对于其他的线程是可见的，就会读取到最新的值。</p>
+<p>由于每次写操作都会创建一个数组的新副本，所以写操作的开销较大。但是读取操作非常高效且不需要加锁，因此适用于读操作远多于写操作的场景，例如缓存、白名单等。
+不适合写操作频繁的场景，在这种情况下，<code>ConcurrentLinkedQueue</code>或<code>ConcurrentHashMap</code>等其他线程安全集合可能更合适。</p>
+<h3 id="copyonwritearrayset">CopyOnWriteArraySet</h3>
+<p><code>CopyOnWriteArraySet</code>是Java中一种线程安全的<code>Set</code>实现，内部使用了<code>CopyOnWriteArrayList</code>来存储元素。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="w"> </span><span class="n">al</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Creates an empty set.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">CopyOnWriteArraySet</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">al</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArrayList</span><span class="o">&lt;</span><span class="n">E</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这种集合在读操作远多于写操作的场景中非常有用，因为它通过每次修改创建集合的副本来实现线程安全。
+因为底层用<code>CopyOnWriteArrayList</code>存储，所以写操作开销大，每次修改都会创建数组副本，适用场景有限。不适用于写操作频繁的场景，否则会导致高昂的内存和时间开销。
+与<code>CopyOnWriteArrayList</code>不同的是，<code>CopyOnWriteArraySet</code>不允许包含重复元素。如果尝试添加一个已经存在的元素，集合将保持不变，所以该集合在线程不安全的情况下可替代<code>HashSet</code>。
+<code>CopyOnWriteArraySet</code>适用于需要唯一性且不关心元素顺序的场景，例如维护一组独特的订阅者或监听器。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CopyOnWriteArraySetExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 CopyOnWriteArraySet</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">cowSet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyOnWriteArraySet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Apple&#34;</span><span class="p">);</span><span class="w"> </span><span class="c1">// 不允许重复元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Set: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fruit</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">cowSet</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">fruit</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加新元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;Grapes&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After adding Grapes: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">cowSet</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="s">&#34;Banana&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After removing Banana: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">cowSet</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hashtable">HashTable</h3>
+<p><code>HashTable</code>的出现是为了解决<code>HashMap</code>线程不安全的问题，但因为性能的原因，在多线程环境下很少使用，一般都会使用<code>ConcurrentHashMap</code>。<code>HashTable</code>性能低的原因，就是直接加了<code>synchronized</code>修饰。</p>
+<p><code>HashMap</code>中的方法大多没有同步，这意味着如果一个线程在遍历<code>HashMap</code>的同时，另一个线程修改了<code>HashMap</code>，例如添加或删除元素，可能会导致<code>ConcurrentModificationException</code>。
+当遍历<code>HashTable</code>中的元素时，此时另一个线程来修改数据，这个时候加锁是没问题的。但是在没有另一个线程该数据的时候，<code>HashTable</code>还是加锁，这时性能就不太好了。可理解为<code>HashTable</code>性能不好的原因就是锁的粒度太粗了。</p>
+<p><code>Hashtable</code>的线程安全通过在方法级别使用<code>synchronized</code>关键字来实现，这确保了每次只有一个线程能够执行任何给定的方法。这种方法级别的锁定提供了基本的线程安全，但在高并发环境下会导致性能瓶颈。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HashtableExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个 Hashtable</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Hashtable</span><span class="o">&lt;</span><span class="n">Integer</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashtable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Hashtable</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 添加元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashtable</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;One&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashtable</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Two&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashtable</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;Three&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 读取元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Value for key 1: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">hashtable</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Value for key 2: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">hashtable</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 删除元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashtable</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 迭代元素</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">hashtable</span><span class="p">.</span><span class="na">keySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Key: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;, Value: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">hashtable</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="concurrenthashmap">ConcurrentHashMap</h3>
+<p><code>ConcurrentHashMap</code>是Java中的一种线程安全的哈希表实现，用来替代传统的<code>HashMap</code>，来解决在多线程环境中并发修改带来的问题。
+与<code>Hashtable</code>不同，<code>ConcurrentHashMap</code>不对整个表进行全局加锁。相反它只对具体操作涉及的部分进行加锁，减少了线程之间的竞争。
+因为<code>HashMap</code>在JDK1.7与JDK1.8做了调整，所以<code>ConcurrentHashMap</code>在JDK1.7与JDK1.8实现也有所不同。</p>
+<h4 id="jdk17">JDK1.7</h4>
+<p>JDK1.7<code>ConcurrentHashMap</code>采用<code>segment</code>的分段锁机制实现线程安全，其中<code>segment</code>类继承自<code>ReentrantLock</code>。用<code>ReentrantLock</code>、CAS来保证线程安全。
+每个分段相当于一个独立的哈希表，并且分别加锁。</p>
+<p>需要注意的是JDK1.7中的ConcurrentHashMap，分段数量是固定。在创建<code>ConcurrentHashMap</code>实例时，必须指定初始的分段数量。
+这个初始的分段数量在实例创建后是不可动态修改的，也就是说一旦创建了<code>ConcurrentHashMap</code>，其分段数量就固定不变了。数组的长度就是<code>concurrencyLevel</code>指定的分段数量。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="nf">ConcurrentHashMap</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">initialCapacity</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">concurrencyLevel</span><span class="p">){}</span><span class="w">
+</span></span></span></code></pre></div><p>相比之下，JDK1.8中的<code>ConcurrentHashMap</code>改进了这一点，不再使用固定的分段数量，而是根据当前的容量动态调整分段的数量，从而更好地适应不同的并发场景，提升了并发性能和灵活性。</p>
+<p><img alt="jdk1.7ConcurrentHashMap" src="/iblog/posts/annex/images/essays/jdk1.7ConcurrentHashMap.png"></p>
+<p>整个<code>ConcurrentHashMap</code>被划分为多个分段，每个分段都是一个独立的哈希表。每个分段独立加锁，细化了锁的粒度，同时允许多个线程同时操作不同的分段，从而提高并发性能。
+使用<code>ReentrantLock</code>锁定分段，在执行插入、删除或更新操作时，只有操作涉及的分段会被锁定，其他分段不受影响。
+在进行插入操作时，先根据键的哈希值确定应该操作哪个分段，然后锁定该分段并进行操作。这种方法可以减少锁争用，提高并发性能。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">public V put(K key， V value) {
+</span></span><span class="line"><span class="cl">    Segment&lt;K,V&gt; s;
+</span></span><span class="line"><span class="cl">    if (value == null)
+</span></span><span class="line"><span class="cl">        throw new NullPointerException();
+</span></span><span class="line"><span class="cl">    int hash = hash(key.hashCode());
+</span></span><span class="line"><span class="cl">    int j = (hash &gt;&gt;&gt; segmentShift) &amp; segmentMask;
+</span></span><span class="line"><span class="cl">    if ((s = (Segment&lt;K,V&gt;)UNSAFE.getObject          // nonvolatile; recheck
+</span></span><span class="line"><span class="cl">         (segments, (j &lt;&lt; SSHIFT) + SBASE)) == null) //  in ensureSegment
+</span></span><span class="line"><span class="cl">        s = ensureSegment(j);
+</span></span><span class="line"><span class="cl">    return s.put(key, hash, value, false);
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>首先判空，然后计算哈希值。计算<code>put</code>进来的元素分配到哪个<code>segment</code>数组上，判断当前<code>segments</code>数组上的元素是否为空，如果分段为空就会使用<code>ensureSegment</code>方法创建<code>segment</code>对象；
+最后调用<code>Segment.put</code>方法存放到对应的节点中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Returns the segment for the given index, creating it and
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * recording in segment table (via CAS) if not already present.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @param k the index
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @return the segment
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">ensureSegment</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">k</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">ss</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">segments</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">u</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">k</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">SSHIFT</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">SBASE</span><span class="p">;</span><span class="w"> </span><span class="c1">// raw offset</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">seg</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">seg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">getObjectVolatile</span><span class="p">(</span><span class="n">ss</span><span class="p">,</span><span class="w"> </span><span class="n">u</span><span class="p">))</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">proto</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ss</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">;</span><span class="w"> </span><span class="c1">// use segment 0 as prototype</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">cap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">proto</span><span class="p">.</span><span class="na">table</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">float</span><span class="w"> </span><span class="n">lf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">proto</span><span class="p">.</span><span class="na">loadFactor</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">threshold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)(</span><span class="n">cap</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">lf</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">HashEntry</span><span class="o">[</span><span class="n">cap</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">seg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">getObjectVolatile</span><span class="p">(</span><span class="n">ss</span><span class="p">,</span><span class="w"> </span><span class="n">u</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="c1">// recheck</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">(</span><span class="n">lf</span><span class="p">,</span><span class="w"> </span><span class="n">threshold</span><span class="p">,</span><span class="w"> </span><span class="n">tab</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">seg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Segment</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">)</span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">getObjectVolatile</span><span class="p">(</span><span class="n">ss</span><span class="p">,</span><span class="w"> </span><span class="n">u</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                       </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">UNSAFE</span><span class="p">.</span><span class="na">compareAndSwapObject</span><span class="p">(</span><span class="n">ss</span><span class="p">,</span><span class="w"> </span><span class="n">u</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">seg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">seg</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>ensureSegment</code>方法作用是返回指定索引的分段对象，通过CAS判断，如果还没有分段则创建它并记录在分段表中。</p>
+<p>当多个线程同时执行该方法，同时通过<code>ensureSegment</code>方法创建<code>segment</code>对象时，只有一个线程能够创建成功。
+其中创建的新<code>segment</code>对象中的加载因子、存放位置、扩容阈值与<code>segment[0]</code>元素保持一致，这样性能更高，因为不用在计算了。</p>
+<p>为了保证线程安全，在<code>ensureSegment</code>方法中用<code>Unsafe</code>类中的一些方法做了三次判断，其中最后一次也就是该方法保证线程安全的关键，用到了CAS操作。确保只有一个线程能够成功创建分段。
+当多个线程并发执行下面的代码，先执行CAS的线程，判断<code>segment</code>数组中某个位置是空的，然后就把这个线程自己创建的<code>segment</code>数组赋值给<code>seg</code>，即<code>seg = s</code>然后<code>break</code>跳出循环。
+后执行的线程会再次判断seg是否为空，因先执行的线程已经<code>seg = s</code>不为空了，所以循环条件不成立，也就不再执行了。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">while ((seg = (Segment&lt;K，V&gt;)UNSAFE.getObjectVolatile(ss, u)) == null) {
+</span></span><span class="line"><span class="cl">    if (UNSAFE.compareAndSwapObject(ss, u, null, seg = s))
+</span></span><span class="line"><span class="cl">        break;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p><code>Segment.put</code>为了保证线程安全，执行<code>put</code>方法时需要加锁，如果未能获取锁，会执行<code>scanAndLockForPut</code>方法，确保最终能获取到锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">final V put(K key, int hash, V value, boolean onlyIfAbsent) {
+</span></span><span class="line"><span class="cl">    HashEntry&lt;K,V&gt; node = tryLock() ? null :
+</span></span><span class="line"><span class="cl">        scanAndLockForPut(key, hash, value);
+</span></span><span class="line"><span class="cl">    // ... 插入节点操作 最后释放锁
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p><code>scanAndLockForPut</code>方法的主要作用就是加锁，如果没有获取锁，就会一致遍历<code>segment</code>数组，直到遍历到最后一个元素。
+每次遍历完都会尝试获取锁，如果还是获取不到锁，就会重试，最大次数为<code>MAX_SCAN_RETRIES</code>在CPU多核下为64次，如果大于64次就会强制加锁。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">scanAndLockForPut</span><span class="p">(</span><span class="n">K</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">entryForHash</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">hash</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">retries</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// negative while locating node</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">tryLock</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="w"> </span><span class="n">f</span><span class="p">;</span><span class="w"> </span><span class="c1">// to recheck first below</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">retries</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">e</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">node</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="c1">// speculatively create node</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">node</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashEntry</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;</span><span class="p">(</span><span class="n">hash</span><span class="p">,</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">retries</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">key</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">key</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">retries</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">retries</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">MAX_SCAN_RETRIES</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">lock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">retries</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                 </span><span class="p">(</span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">entryForHash</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">hash</span><span class="p">))</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">first</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f</span><span class="p">;</span><span class="w"> </span><span class="c1">// re-traverse if entry changed</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">retries</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">node</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">MAX_SCAN_RETRIES</span><span class="w"> </span><span class="o">=</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Runtime</span><span class="p">.</span><span class="na">getRuntime</span><span class="p">().</span><span class="na">availableProcessors</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">64</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><h4 id="jdk18">JDK1.8</h4>
+<p>在JDK1.8中，<code>ConcurrentHashMap</code>进行了重大改进，弃用了分段锁机制，转而采用更细粒度的并发控制机制。
+直接用Node数组+链表/红黑树的数据结构来实现，并发控制使用 <code>synchronized</code> 和CAS来操作，整体看起来就像是优化过且线程安全的<code>HashMap</code>。
+虽然在JDK1.8中还能看到<code>Segment</code>的数据结构，但是已经简化了其属性，这样做只是为了兼容旧版本。</p>
+<p>JDK1.8中彻底放弃了<code>Segment</code>转而采用的是<code>Node</code>，其设计思想也不再是JDK1.7中的分段锁思想。
+<code>ConcurrentHashMap</code>在JDK1.8中不再使用分段锁，而是使用与<code>HashMap</code>类似的数组+链表/红黑树的数据结构。
+数组中的每个桶是一个链表或红黑树的头节点。<code>HashMap</code>不同的是<code>ConcurrentHashMap</code>只是增加了同步操作来控制并发。</p>
+<p><img alt="jdk1.8ConcurrentHashMap" src="/iblog/posts/annex/images/essays/jdk1.8ConcurrentHashMap.png"></p>
+<p>插入操作首先根据键的哈希值定位到具体的桶。如果该桶为空，则使用CAS操作插入新的节点。如果该桶非空，则使用<code>synchronized</code>锁定该桶，并进行链表或红黑树的插入操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">final V putVal(K key, V value, boolean onlyIfAbsent) {
+</span></span><span class="line"><span class="cl">    if (key == null || value == null)
+</span></span><span class="line"><span class="cl">        throw new NullPointerException();
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    // 计算键的哈希值，并将其扩散
+</span></span><span class="line"><span class="cl">    int hash = spread(key.hashCode());
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    // 记录桶中元素个数
+</span></span><span class="line"><span class="cl">    int binCount = 0;
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    // 循环查找或插入元素
+</span></span><span class="line"><span class="cl">    for (Node&lt;K,V&gt;[] tab = table;;) {
+</span></span><span class="line"><span class="cl">        Node&lt;K,V&gt; f;
+</span></span><span class="line"><span class="cl">        int n, i, fh;
+</span></span><span class="line"><span class="cl">        
+</span></span><span class="line"><span class="cl">        // 如果表为空或长度为0，则进行初始化
+</span></span><span class="line"><span class="cl">        if (tab == null || (n = tab.length) == 0)
+</span></span><span class="line"><span class="cl">            tab = initTable();
+</span></span><span class="line"><span class="cl">        
+</span></span><span class="line"><span class="cl">        // 计算存储位置
+</span></span><span class="line"><span class="cl">        else if ((f = tabAt(tab, i = (n - 1) &amp; hash)) == null) {
+</span></span><span class="line"><span class="cl">            // 如果位置为空，则尝试使用 CAS 插入新节点
+</span></span><span class="line"><span class="cl">            if (casTabAt(tab, i, null, new Node&lt;K,V&gt;(hash, key, value, null)))
+</span></span><span class="line"><span class="cl">                break;  // 插入成功，退出循环
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        
+</span></span><span class="line"><span class="cl">        // 如果位置非空，处理链表或红黑树结构
+</span></span><span class="line"><span class="cl">        else if ((fh = f.hash) == MOVED)
+</span></span><span class="line"><span class="cl">            tab = helpTransfer(tab, f); // 如果处于扩容状态，则帮助进行扩容
+</span></span><span class="line"><span class="cl">        
+</span></span><span class="line"><span class="cl">        else {
+</span></span><span class="line"><span class="cl">            V oldVal = null;
+</span></span><span class="line"><span class="cl">            
+</span></span><span class="line"><span class="cl">            // 使用 synchronized 锁定桶
+</span></span><span class="line"><span class="cl">            synchronized (f) {
+</span></span><span class="line"><span class="cl">                if (tabAt(tab, i) == f) {
+</span></span><span class="line"><span class="cl">                    if (fh &gt;= 0) {
+</span></span><span class="line"><span class="cl">                        // 处理链表结构
+</span></span><span class="line"><span class="cl">                        binCount = 1;
+</span></span><span class="line"><span class="cl">                        for (Node&lt;K,V&gt; e = f;; ++binCount) {
+</span></span><span class="line"><span class="cl">                            K ek;
+</span></span><span class="line"><span class="cl">                            if (e.hash == hash &amp;&amp;
+</span></span><span class="line"><span class="cl">                                ((ek = e.key) == key ||
+</span></span><span class="line"><span class="cl">                                 (ek != null &amp;&amp; key.equals(ek)))) {
+</span></span><span class="line"><span class="cl">                                oldVal = e.val;
+</span></span><span class="line"><span class="cl">                                if (!onlyIfAbsent)
+</span></span><span class="line"><span class="cl">                                    e.val = value;
+</span></span><span class="line"><span class="cl">                                break;
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">                            Node&lt;K,V&gt; pred = e;
+</span></span><span class="line"><span class="cl">                            if ((e = e.next) == null) {
+</span></span><span class="line"><span class="cl">                                pred.next = new Node&lt;K,V&gt;(hash, key, value, null);
+</span></span><span class="line"><span class="cl">                                break;
+</span></span><span class="line"><span class="cl">                            }
+</span></span><span class="line"><span class="cl">                        }
+</span></span><span class="line"><span class="cl">                    } else if (f instanceof TreeBin) {
+</span></span><span class="line"><span class="cl">                        // 处理红黑树结构
+</span></span><span class="line"><span class="cl">                        Node&lt;K,V&gt; p;
+</span></span><span class="line"><span class="cl">                        binCount = 2;
+</span></span><span class="line"><span class="cl">                        if ((p = ((TreeBin&lt;K,V&gt;)f).putTreeVal(hash, key, value)) != null) {
+</span></span><span class="line"><span class="cl">                            oldVal = p.val;
+</span></span><span class="line"><span class="cl">                            if (!onlyIfAbsent)
+</span></span><span class="line"><span class="cl">                                p.val = value;
+</span></span><span class="line"><span class="cl">                        }
+</span></span><span class="line"><span class="cl">                    }
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            
+</span></span><span class="line"><span class="cl">            // 根据操作结果进行进一步处理
+</span></span><span class="line"><span class="cl">            if (binCount != 0) {
+</span></span><span class="line"><span class="cl">                if (binCount &gt;= TREEIFY_THRESHOLD)  // 如果链表长度达到阈值，则转为红黑树
+</span></span><span class="line"><span class="cl">                    treeifyBin(tab, i);
+</span></span><span class="line"><span class="cl">                if (oldVal != null)
+</span></span><span class="line"><span class="cl">                    return oldVal;  // 返回旧值
+</span></span><span class="line"><span class="cl">                break;  // 插入完成，退出循环
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    // 更新计数器
+</span></span><span class="line"><span class="cl">    addCount(1L, binCount);
+</span></span><span class="line"><span class="cl">    return null;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>如果<code>table</code>为空或长度为0，则调用<code>initTable()</code>方法进行初始化。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">private final Node&lt;K,V&gt;[] initTable() {
+</span></span><span class="line"><span class="cl">    Node&lt;K,V&gt;[] tab; int sc;
+</span></span><span class="line"><span class="cl">    while ((tab = table) == null || tab.length == 0) {
+</span></span><span class="line"><span class="cl">        if ((sc = sizeCtl) &lt; 0)
+</span></span><span class="line"><span class="cl">            Thread.yield(); // lost initialization race; just spin
+</span></span><span class="line"><span class="cl">        else if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) {
+</span></span><span class="line"><span class="cl">            try {
+</span></span><span class="line"><span class="cl">                if ((tab = table) == null || tab.length == 0) {
+</span></span><span class="line"><span class="cl">                    int n = (sc &gt; 0) ? sc : DEFAULT_CAPACITY;
+</span></span><span class="line"><span class="cl">                    @SuppressWarnings(&#34;unchecked&#34;)
+</span></span><span class="line"><span class="cl">                    Node&lt;K,V&gt;[] nt = (Node&lt;K,V&gt;[])new Node&lt;?,?&gt;[n];
+</span></span><span class="line"><span class="cl">                    table = tab = nt;
+</span></span><span class="line"><span class="cl">                    sc = n - (n &gt;&gt;&gt; 2);
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            } finally {
+</span></span><span class="line"><span class="cl">                sizeCtl = sc;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">            break;
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">    return tab;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>根据键的哈希值<code>hash</code>计算存储在<code>table</code>中的位置。如果该位置为空，则使用<code>casTabAt()</code>方法尝试通过CAS操作插入新的<code>Node</code>节点。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int hash = spread(key.hashCode());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// hash算法，计算存放在map中的位置；要保证尽可能的均匀分散，避免hash冲突
+</span></span><span class="line"><span class="cl">static final int HASH_BITS = 0x7fffffff;
+</span></span><span class="line"><span class="cl">static final int spread(int h) {
+</span></span><span class="line"><span class="cl">    // 等同于： key.hashCode() ^ (key.hashCode() &gt;&gt;&gt; 16) &amp; 0x7fffffff
+</span></span><span class="line"><span class="cl">    return (h ^ (h &gt;&gt;&gt; 16)) &amp; HASH_BITS;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>如果位置非空，首先判断是否处于扩容状态<code>MOVED</code>，如果是，则调用<code>helpTransfer()</code>方法协助进行扩容操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// MOVED = -1
+</span></span><span class="line"><span class="cl">if ((fh = f.hash) == MOVED)
+</span></span><span class="line"><span class="cl">tab = helpTransfer(tab, f);
+</span></span></code></pre></div><p>如果位置上是链表结构<code>(fh &gt;= 0)</code>，则遍历链表，根据键查找或插入节点。如果位置上是红黑树结构<code>(f instanceof TreeBin)</code>，则调用<code>putTreeVal()</code>方法在红黑树中插入节点。
+然后使用<code>synchronized (f)</code>锁定桶，确保在链表或红黑树操作期间其他线程不能修改桶的结构。根据链表长度<code>binCount &gt;= TREEIFY_THRESHOLD(默认是8)</code>，则把链表转化为红黑树结构的情况，如果插入操作修改了已有节点的值，则返回旧值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">V oldVal = null;
+</span></span><span class="line"><span class="cl">synchronized (f) {
+</span></span><span class="line"><span class="cl">    if (tabAt(tab, i) == f) {
+</span></span><span class="line"><span class="cl">        if (fh &gt;= 0) {
+</span></span><span class="line"><span class="cl">            binCount = 1;
+</span></span><span class="line"><span class="cl">            for (Node&lt;K,V&gt; e = f;; ++binCount) {
+</span></span><span class="line"><span class="cl">                K ek;
+</span></span><span class="line"><span class="cl">                if (e.hash == hash &amp;&amp;
+</span></span><span class="line"><span class="cl">                    ((ek = e.key) == key ||
+</span></span><span class="line"><span class="cl">                     (ek != null &amp;&amp; key.equals(ek)))) {
+</span></span><span class="line"><span class="cl">                    oldVal = e.val;
+</span></span><span class="line"><span class="cl">                    if (!onlyIfAbsent)
+</span></span><span class="line"><span class="cl">                        e.val = value;
+</span></span><span class="line"><span class="cl">                    break;
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">                Node&lt;K,V&gt; pred = e;
+</span></span><span class="line"><span class="cl">                if ((e = e.next) == null) {
+</span></span><span class="line"><span class="cl">                    pred.next = new Node&lt;K,V&gt;(hash, key,
+</span></span><span class="line"><span class="cl">                                              value, null);
+</span></span><span class="line"><span class="cl">                    break;
+</span></span><span class="line"><span class="cl">                }
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">        else if (f instanceof TreeBin) {
+</span></span><span class="line"><span class="cl">            Node&lt;K,V&gt; p;
+</span></span><span class="line"><span class="cl">            binCount = 2;
+</span></span><span class="line"><span class="cl">            if ((p = ((TreeBin&lt;K,V&gt;)f).putTreeVal(hash, key,
+</span></span><span class="line"><span class="cl">                                           value)) != null) {
+</span></span><span class="line"><span class="cl">                oldVal = p.val;
+</span></span><span class="line"><span class="cl">                if (!onlyIfAbsent)
+</span></span><span class="line"><span class="cl">                    p.val = value;
+</span></span><span class="line"><span class="cl">            }
+</span></span><span class="line"><span class="cl">        }
+</span></span><span class="line"><span class="cl">    }
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">if (binCount != 0) {
+</span></span><span class="line"><span class="cl">    if (binCount &gt;= TREEIFY_THRESHOLD)
+</span></span><span class="line"><span class="cl">        treeifyBin(tab, i);
+</span></span><span class="line"><span class="cl">    if (oldVal != null)
+</span></span><span class="line"><span class="cl">        return oldVal;
+</span></span><span class="line"><span class="cl">    break;
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p>最后调用<code>addCount()</code>方法更新元素计数器，表示成功插入了一个节点。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">// 相当于size++
+</span></span><span class="line"><span class="cl">addCount(1L, binCount);
+</span></span></code></pre></div><p>其中<code>addCount()</code>方法中也包含了扩容操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">addCount</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">x</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">check</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">CounterCell</span><span class="o">[]</span><span class="w"> </span><span class="n">as</span><span class="p">;</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">b</span><span class="p">,</span><span class="w"> </span><span class="n">s</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">as</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">counterCells</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="o">!</span><span class="n">U</span><span class="p">.</span><span class="na">compareAndSwapLong</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">BASECOUNT</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">baseCount</span><span class="p">,</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">x</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CounterCell</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">v</span><span class="p">;</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">m</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">uncontended</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">as</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">m</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">as</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">(</span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">as</span><span class="o">[</span><span class="n">ThreadLocalRandom</span><span class="p">.</span><span class="na">getProbe</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">m</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="o">!</span><span class="p">(</span><span class="n">uncontended</span><span class="w"> </span><span class="o">=</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="n">U</span><span class="p">.</span><span class="na">compareAndSwapLong</span><span class="p">(</span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">CELLVALUE</span><span class="p">,</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="na">value</span><span class="p">,</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">x</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">fullAddCount</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="w"> </span><span class="n">uncontended</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">check</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sumCount</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">check</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Node</span><span class="o">&lt;</span><span class="n">K</span><span class="p">,</span><span class="n">V</span><span class="o">&gt;[]</span><span class="w"> </span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="n">nt</span><span class="p">;</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">sc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="p">(</span><span class="kt">long</span><span class="p">)(</span><span class="n">sc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sizeCtl</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">tab</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">               </span><span class="p">(</span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tab</span><span class="p">.</span><span class="na">length</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">MAXIMUM_CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">resizeStamp</span><span class="p">(</span><span class="n">n</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">sc</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">sc</span><span class="w"> </span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">RESIZE_STAMP_SHIFT</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">sc</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">sc</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">MAX_RESIZERS</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="p">(</span><span class="n">nt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nextTable</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">transferIndex</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">U</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">SIZECTL</span><span class="p">,</span><span class="w"> </span><span class="n">sc</span><span class="p">,</span><span class="w"> </span><span class="n">sc</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">transfer</span><span class="p">(</span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="n">nt</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">U</span><span class="p">.</span><span class="na">compareAndSwapInt</span><span class="p">(</span><span class="k">this</span><span class="p">,</span><span class="w"> </span><span class="n">SIZECTL</span><span class="p">,</span><span class="w"> </span><span class="n">sc</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                         </span><span class="p">(</span><span class="n">rs</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">RESIZE_STAMP_SHIFT</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">2</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">transfer</span><span class="p">(</span><span class="n">tab</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sumCount</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>节点从<code>table</code>移动到<code>nextTable</code>，大体思想是遍历、复制的过程。
+通过<code>Unsafe.compareAndSwapInt</code>修改<code>sizeCtl</code>值，保证只有一个线程能够初始化<code>nextTable</code>，扩容后的数组长度为原来的两倍，但是容量是原来的1.5。</p>
+<h2 id="参考文章">参考文章</h2>
+<ul>
+<li><a href="http://www.threadlocal.cn">http://www.threadlocal.cn</a></li>
+<li><a href="https://blog.csdn.net/lufeng20/article/details/24314381">https://blog.csdn.net/lufeng20/article/details/24314381</a></li>
+<li><a href="https://blog.csdn.net/qq_35190492/article/details/116431270">https://blog.csdn.net/qq_35190492/article/details/116431270</a></li>
+<li><a href="https://www.cnblogs.com/dolphin0520/p/3920407.html">https://www.cnblogs.com/dolphin0520/p/3920407.html</a></li>
+<li><a href="https://www.jianshu.com/p/c0642afe03e0">https://www.jianshu.com/p/c0642afe03e0</a></li>
+<li><a href="https://www.cnblogs.com/edisonchou/p/5061886.html">https://www.cnblogs.com/edisonchou/p/5061886.html</a></li>
+<li><a href="https://zhuanlan.zhihu.com/p/361475700">https://zhuanlan.zhihu.com/p/361475700</a></li>
+<li><a href="http://www.cs.umd.edu/~pugh/java/memoryModel/jsr133.pdf">http://www.cs.umd.edu/~pugh/java/memoryModel/jsr133.pdf</a></li>
+<li><a href="https://www.cnblogs.com/myseries/p/10784076.html">https://www.cnblogs.com/myseries/p/10784076.html</a></li>
+<li><a href="http://www.blogjava.net/zhanglongsr/articles/356782.html">http://www.blogjava.net/zhanglongsr/articles/356782.html</a></li>
+<li><a href="https://zhuanlan.zhihu.com/p/290991898">https://zhuanlan.zhihu.com/p/290991898</a></li>
+<li><a href="https://blog.csdn.net/choukekai/article/details/63688332">https://blog.csdn.net/choukekai/article/details/63688332</a></li>
+<li><a href="https://blog.csdn.net/zqz_zqz/article/details/70233767">https://blog.csdn.net/zqz_zqz/article/details/70233767</a></li>
+<li><a href="https://tech.meituan.com/2018/11/15/java-lock.html">https://tech.meituan.com/2018/11/15/java-lock.html</a></li>
+<li><a href="https://www.cnblogs.com/aspirant/p/11470858.html">https://www.cnblogs.com/aspirant/p/11470858.html</a></li>
+<li><a href="https://www.bilibili.com/video/BV1xt411S7xy?p=159">https://www.bilibili.com/video/BV1xt411S7xy?p=159</a></li>
+<li><a href="https://developer.51cto.com/art/202104/656540.htm">https://developer.51cto.com/art/202104/656540.htm</a></li>
+<li><a href="https://blog.csdn.net/qq_38293564/article/details/80558157">https://blog.csdn.net/qq_38293564/article/details/80558157</a></li>
+<li><a href="https://zhuanlan.zhihu.com/p/98593407">https://zhuanlan.zhihu.com/p/98593407</a></li>
+<li><a href="https://blog.csdn.net/zbc1090549839/article/details/53389602">https://blog.csdn.net/zbc1090549839/article/details/53389602</a></li>
+<li><a href="https://www.hollischuang.com/archives/2030">https://www.hollischuang.com/archives/2030</a></li>
+<li><a href="https://blog.csdn.net/javazejian/article/details/72828483">https://blog.csdn.net/javazejian/article/details/72828483</a></li>
+<li><a href="https://blog.csdn.net/luoweifu/article/details/46613015">https://blog.csdn.net/luoweifu/article/details/46613015</a></li>
+<li><a href="https://www.artima.com/insidejvm/ed2/threadsynch.html">https://www.artima.com/insidejvm/ed2/threadsynch.html</a></li>
+<li><a href="https://xie.infoq.cn/article/d3afa3e6f9a70155106627ce5">https://xie.infoq.cn/article/d3afa3e6f9a70155106627ce5</a></li>
+<li><a href="http://hollischuang.gitee.io/tobetopjavaer/#/basics/concurrent-coding/synchronized">http://hollischuang.gitee.io/tobetopjavaer/#/basics/concurrent-coding/synchronized</a></li>
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+<html lang="zh" >
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+	<title>Java面向对象 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="概览 面向对象简称OO(object-oriented)是相对面向过程(procedure-oriented)来说的，是一种编程思想，Java就是一门面向对象的语" />
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+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
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+<body>
+    <div class="post-password">
+        
+    </div>
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+    
+    
+    
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+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
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+        
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+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%a7%88">
+                    概览
+                </a>
+            </li>
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+            
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+        
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+                <a class="nav-link text-left" href="#%e8%bd%af%e4%bb%b6%e8%ae%be%e8%ae%a1%e5%8e%9f%e5%88%99">
+                    软件设计原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
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+                    单一职责原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bc%80%e6%94%be%e5%b0%81%e9%97%ad%e5%8e%9f%e5%88%99">
+                    开放封闭原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%be%9d%e8%b5%96%e5%80%92%e7%bd%ae%e5%8e%9f%e5%88%99">
+                    依赖倒置原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%a5%e5%8f%a3%e9%9a%94%e7%a6%bb%e5%8e%9f%e5%88%99">
+                    接口隔离原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8c%e6%b0%8f%e6%9b%bf%e6%8d%a2%e5%8e%9f%e5%88%99">
+                    里氏替换原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%90%88%e6%88%90%e5%a4%8d%e7%94%a8%e5%8e%9f%e5%88%99">
+                    合成复用原则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%aa%e7%b1%b3%e7%89%b9%e6%b3%95%e5%88%99">
+                    迪米特法则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9d%a2%e5%90%91%e5%af%b9%e8%b1%a1%e4%b8%89%e5%a4%a7%e7%89%b9%e6%80%a7">
+                    面向对象三大特性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b0%81%e8%a3%85">
+                    封装
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%a7%e6%89%bf">
+                    继承
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%a7%e6%89%bf%e4%b8%8e%e7%bb%84%e5%90%88">
+                    继承与组合
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8a%bd%e8%b1%a1%e7%b1%bb%e4%b8%8e%e6%8e%a5%e5%8f%a3">
+                    抽象类与接口
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%9a%e6%80%81">
+                    多态
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8d%e5%86%99%e4%b8%8e%e9%87%8d%e8%bd%bd">
+                    重写与重载
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%ae%be%e8%ae%a1%e6%a8%a1%e5%bc%8f">
+                    设计模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8d%95%e4%be%8b%e6%a8%a1%e5%bc%8f">
+                    单例模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%a5%bf%e6%b1%89%e5%bc%8f">
+                    饿汉式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e4%b8%8d%e5%ae%89%e5%85%a8%e7%9a%84%e6%87%92%e6%b1%89%e5%bc%8f">
+                    线程不安全的懒汉式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8%e7%9a%84%e6%87%92%e6%b1%89%e5%bc%8f">
+                    线程安全的懒汉式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8c%e9%87%8d%e6%a0%a1%e9%aa%8c%e9%94%81">
+                    双重校验锁
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9d%99%e6%80%81%e5%86%85%e9%83%a8%e7%b1%bb%e5%bc%8f">
+                    静态内部类式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%9e%9a%e4%b8%be%e5%bc%8f">
+                    枚举式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8d%95%e4%be%8b%e4%b8%8e%e5%ba%8f%e5%88%97%e5%8c%96">
+                    单例与序列化
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b7%a5%e5%8e%82%e6%a8%a1%e5%bc%8f">
+                    工厂模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ae%80%e5%8d%95%e5%b7%a5%e5%8e%82%e6%a8%a1%e5%bc%8f">
+                    简单工厂模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%b7%a5%e5%8e%82%e6%96%b9%e6%b3%95%e6%a8%a1%e5%bc%8f">
+                    工厂方法模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8a%bd%e8%b1%a1%e5%b7%a5%e5%8e%82%e6%a8%a1%e5%bc%8f">
+                    抽象工厂模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8e%9f%e5%9e%8b%e6%a8%a1%e5%bc%8f">
+                    原型模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b5%85%e5%85%8b%e9%9a%86">
+                    浅克隆
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b7%b1%e5%85%8b%e9%9a%86">
+                    深克隆
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%bb%e7%bb%93">
+                    总结
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%bb%ba%e9%80%a0%e8%80%85%e6%a8%a1%e5%bc%8f">
+                    建造者模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%82%e9%85%8d%e5%99%a8%e6%a8%a1%e5%bc%8f">
+                    适配器模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%af%b9%e8%b1%a1%e9%80%82%e9%85%8d%e5%99%a8">
+                    对象适配器
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%b1%bb%e9%80%82%e9%85%8d%e5%99%a8">
+                    类适配器
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%bb%e7%bb%93-1">
+                    总结
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a1%a5%e6%8e%a5%e6%a8%a1%e5%bc%8f">
+                    桥接模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%84%e5%90%88%e6%a8%a1%e5%bc%8f">
+                    组合模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a3%85%e9%a5%b0%e6%a8%a1%e5%bc%8f">
+                    装饰模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%96%e8%a7%82%e6%a8%a1%e5%bc%8f">
+                    外观模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%ba%ab%e5%85%83%e6%a8%a1%e5%bc%8f">
+                    享元模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bb%a3%e7%90%86%e6%a8%a1%e5%bc%8f">
+                    代理模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%9d%99%e6%80%81%e4%bb%a3%e7%90%86">
+                    静态代理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#jdk%e5%8a%a8%e6%80%81%e4%bb%a3%e7%90%86">
+                    JDK动态代理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cglib%e5%8a%a8%e6%80%81%e4%bb%a3%e7%90%86">
+                    Cglib动态代理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%80%bb%e7%bb%93-2">
+                    总结
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%81%8c%e8%b4%a3%e9%93%be%e6%a8%a1%e5%bc%8f">
+                    职责链模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%91%bd%e4%bb%a4%e6%a8%a1%e5%bc%8f">
+                    命令模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%a3%e9%87%8a%e5%99%a8%e6%a8%a1%e5%bc%8f">
+                    解释器模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%ad%e4%bb%a3%e5%99%a8%e6%a8%a1%e5%bc%8f">
+                    迭代器模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%ad%e4%bb%8b%e8%80%85%e6%a8%a1%e5%bc%8f">
+                    中介者模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%a4%87%e5%bf%98%e5%bd%95%e6%a8%a1%e5%bc%8f">
+                    备忘录模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a7%82%e5%af%9f%e8%80%85%e6%a8%a1%e5%bc%8f">
+                    观察者模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%8a%b6%e6%80%81%e6%a8%a1%e5%bc%8f">
+                    状态模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ad%96%e7%95%a5%e6%a8%a1%e5%bc%8f">
+                    策略模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a8%a1%e6%9d%bf%e6%96%b9%e6%b3%95%e6%a8%a1%e5%bc%8f">
+                    模板方法模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%ae%bf%e9%97%ae%e8%80%85%e6%a8%a1%e5%bc%8f">
+                    访问者模式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="https://whiteppure.github.io/iblog/">首页</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
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+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="https://whiteppure.github.io/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
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+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
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+                    
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+                    <i class="ri-rss-fill"></i>
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+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                        <h2 id="post_single_title">Java面向对象</h2>
+                        <span id="post_page_title_date" class="date">2021.02.15</span>
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+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p>面向对象简称OO(<code>object-oriented</code>)是相对面向过程(<code>procedure-oriented</code>)来说的，是一种编程思想，Java就是一门面向对象的语言，包括三大特性和六大原则。
+其中，三大特性指的是封装、继承和多态。六大原则指的是单一职责原则、开放封闭原则、迪米特原则、里氏替换原则、依赖倒置原则以及接口隔离原则。
+单一职责原则是指一个类应该是一组相关性很高的函数和数据的封装，这是为了提高程序的内聚性，而其他五个原则是通过抽象来实现的，目的是为了降低程序的耦合性以及提高可扩展性。</p>
+<p>面向对象编程简称OOP(<code>Object-oriented programming</code>)，是将事务高度抽象化的编程模式。
+面向对象编程是以功能来划分问题的，将问题分解成一个一个步骤，对每个步骤进行相应的抽象，形成对应对象，通过不同对象之间的调用，组合成某个功能解决问题。</p>
+<p>面向对象是对比面向过程来说的，面向过程编程简称POP(<code>Procedural oriented programming</code>)。
+面向过程编程是一种以过程为中心的编程方式，主要通过一系列步骤来处理数据。程序通过调用函数一步步完成任务，每个函数都执行特定的操作。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 面向过程编程示例：计算矩形面积</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ProceduralExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 定义计算面积的函数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calculateArea</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">width</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">height</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">width</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">width</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">height</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">area</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">calculateArea</span><span class="p">(</span><span class="n">width</span><span class="p">,</span><span class="w"> </span><span class="n">height</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;矩形的面积是: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">area</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>面向对象编程是一种以对象为中心的编程方式，将数据和操作封装在一起，通过对象的交互来完成程序的功能。对象是类的实例，类定义了对象的属性和方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 面向对象编程示例：计算矩形面积</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 定义矩形类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Rectangle</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构造函数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Rectangle</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">width</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">height</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">width</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">height</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 计算面积的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">calculateArea</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">width</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ObjectOrientedExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建矩形对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Rectangle</span><span class="w"> </span><span class="n">rectangle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Rectangle</span><span class="p">(</span><span class="n">5</span><span class="p">,</span><span class="w"> </span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 调用对象的方法计算面积</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">area</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rectangle</span><span class="p">.</span><span class="na">calculateArea</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;矩形的面积是: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">area</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>通过例子可以看出面向对象更重视不重复造轮子，即创建一次重复使用。
+简而言之，用面向过程的方法写出来的程序是一份蛋炒饭，而用面向对象写出来的程序是一份盖浇饭，就是在一碗白米饭上面浇上一份盖菜，你喜欢什么菜，你就浇上什么菜。</p>
+<p>面向对象是模型化的，你只需抽象出几个类，进行封装成各个功能，通过不同对象之间的调用来解决问题，而面向过程需要把问题分解为几个步骤，每个步骤用对应的函数调用即可。
+面向过程是具体化的、流程化的，解决一个问题需要你一步一步的分析，一步一步的实现。
+面向对象的底层其实还是面向过程，把面向过程抽象成类，然后进行封装，方便我们我们使用就是面向对象了。</p>
+<p>抽象会使复杂的问题更加简单化，面向对象更符合人类的思维，而面向过程则是机器的思想。
+选择哪种编程范式取决于具体的应用场景和开发需求。对于复杂系统的开发，面向对象更有优势，因为它可以更好地组织和管理代码；而对于一些简单的任务，面向过程可能更加直观和高效。</p>
+<h2 id="软件设计原则">软件设计原则</h2>
+<p>软件设计原则是指导软件开发过程中设计和构建软件系统的一组规则。
+这些规则的目的是为了让程序达到高内聚、低耦合以及提高扩展性，其实现手段是面向对象的三大特性：封装、继承以及多态。</p>
+<table>
+<thead>
+<tr>
+<th>设计原则名称</th>
+<th>核心思想</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>单一职责原则</td>
+<td>一个类只负责一个特定的职责</td>
+</tr>
+<tr>
+<td>开放封闭原则</td>
+<td>软件实体应该可以扩展，但不应该修改其已有代码</td>
+</tr>
+<tr>
+<td>依赖倒转原则</td>
+<td>高层模块不应该依赖低层模块，两者都应该依赖抽象；抽象不应该依赖细节，细节应该依赖抽象</td>
+</tr>
+<tr>
+<td>里氏替换原则</td>
+<td>任何基类可以出现的地方，子类也可以出现</td>
+</tr>
+<tr>
+<td>接口隔离原则</td>
+<td>使用多个专门的接口，而不是一个通用的接口</td>
+</tr>
+<tr>
+<td>合成复用原则</td>
+<td>优先使用组合而不是继承来实现代码复用</td>
+</tr>
+<tr>
+<td>迪米特法则</td>
+<td>一个对象应尽量少地了解其他对象，从而降低耦合度</td>
+</tr>
+</tbody>
+</table>
+<h3 id="单一职责原则">单一职责原则</h3>
+<p>其核心思想为，一个类最好只做一件事。单一职责原则可降低类的复杂度，提高代码可读性、可维护性、降低变更风险。
+单一职责原则可以看做是低耦合、高内聚在面向对象原则上的引申，将职责定义为引起变化的原因，以提高内聚性来减少引起变化的原因。
+职责过多，可能引起它变化的原因就越多，这将导致职责依赖，相互之间就产生影响，从而大大损伤其内聚性和耦合度。
+通常意义下的单一职责，就是指只有一种单一功能，不要为类实现过多的功能点，以保证实体只有一个引起它变化的原因。
+专注，是一个人优良的品质；同样的，单一也是一个类的优良设计。交杂不清的职责将使得代码看起来特别别扭牵一发而动全身，有失美感和必然导致丑陋的系统错误风险。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Vehicle</span><span class="w"> </span><span class="n">vehicle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Vehicle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vehicle</span><span class="p">.</span><span class="na">running</span><span class="p">(</span><span class="s">&#34;汽车&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 飞机不是在路上行驶</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vehicle</span><span class="p">.</span><span class="na">running</span><span class="p">(</span><span class="s">&#34;飞机&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 在run方法中违反了单一职责原则
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 解决方法根据不同的交通工具,分解成不同的类即可
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Vehicle</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">running</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在路上行驶 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 解决</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Driving</span><span class="w"> </span><span class="n">driving</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Driving</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">driving</span><span class="p">.</span><span class="na">running</span><span class="p">(</span><span class="s">&#34;汽车&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Flight</span><span class="w"> </span><span class="n">flight</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Flight</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flight</span><span class="p">.</span><span class="na">running</span><span class="p">(</span><span class="s">&#34;飞机&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Driving</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">running</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在路上行驶 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Flight</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">running</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在空中飞行 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>只要类中方法数量足够少，可以在方法级别保持单一职责原则。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Vehicle2</span><span class="w"> </span><span class="n">vehicle2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Vehicle2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vehicle2</span><span class="p">.</span><span class="na">driving</span><span class="p">(</span><span class="s">&#34;汽车&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">vehicle2</span><span class="p">.</span><span class="na">flight</span><span class="p">(</span><span class="s">&#34;飞机&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/*
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 改进
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Vehicle2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">driving</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在路上行驶 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">flight</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;在空中飞行 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="开放封闭原则">开放封闭原则</h3>
+<p>软件实体应该是可扩展的，而不可修改的。也就是对提供方扩展开放，对使用方修改封闭的。开放封闭原则主要体现在两个方面：</p>
+<ul>
+<li>对扩展开放，意味着有新的需求或变化时，可以对现有代码进行扩展，以适应新的情况。</li>
+<li>对修改封闭，意味着类一旦设计完成，就可以独立完成其工作，而不要对其进行任何尝试的修改。</li>
+</ul>
+<p>实现开放封闭原则的核心思想是对抽象编程，而不对具体编程。
+因为抽象相对稳定，让类依赖于固定的抽象，所以修改就是封闭的；而通过面向对象的继承和多态机制，又可以实现对抽象类的继承，通过覆写其方法来改变固有行为，实现新的拓展方法，所以就是开放的。
+需求总是变化，当我们给程序添加或者修改功能时，需要用开放封闭原则来封闭变化满足需求，同时还能保持软件内部的封装体系稳定，不被需求的变化影响。
+编程中遵循其他原则，以及使用其他设计模式的目的就是为了遵循开闭原则。</p>
+<p>当软件需要变化时，尽量使用扩展的软件实体的方式行为来实现变化，而不是通过修改已有的代码来实现变化。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Mother</span><span class="w"> </span><span class="n">mother</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Mother</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Son</span><span class="w"> </span><span class="n">son</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Son</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Daughter</span><span class="w"> </span><span class="n">daughter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Daughter</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 注入子类对象 如果扩展需要其他类 换成其他对象即可</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mother</span><span class="p">.</span><span class="na">setAbstractFather</span><span class="p">(</span><span class="n">son</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mother</span><span class="p">.</span><span class="na">display</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractFather</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Son</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractFather</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;son class ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Daughter</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractFather</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;daughter class ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Mother</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractFather</span><span class="w"> </span><span class="n">abstractFather</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAbstractFather</span><span class="p">(</span><span class="n">AbstractFather</span><span class="w"> </span><span class="n">abstractFather</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">abstractFather</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">abstractFather</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractFather</span><span class="p">.</span><span class="na">display</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="依赖倒置原则">依赖倒置原则</h3>
+<p>该原则依赖于抽象，具体而言就是高层模块不依赖于底层模块，二者都同依赖于抽象，抽象不依赖于具体，具体依赖于抽象。
+我们知道，依赖一定会存在于类与类、模块与模块之间。当两个模块之间存在紧密的耦合关系时，最好的方法就是分离接口和实现，即在依赖之间定义一个抽象的接口使得高层模块调用接口，而底层模块实现接口的定义，以此来有效控制耦合关系，达到依赖于抽象的设计目标。
+抽象的稳定性决定了系统的稳定性，因为抽象是不变的，依赖于抽象是面向对象设计的精髓，也是依赖倒置原则的核心。
+依赖于抽象是一个通用的原则，而某些时候依赖于细节则是在所难免的，必须权衡在抽象和具体之间的取舍。</p>
+<p>依赖于抽象，就是对接口编程，不要对实现编程。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 定义一个接口，表示消息发送者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">MessageSender</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实现接口的EmailSender类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">EmailSender</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">MessageSender</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Sending email with message: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实现接口的SmsSender类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SmsSender</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">MessageSender</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Sending SMS with message: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 高层模块的MessageService类依赖于MessageSender接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">MessageService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">MessageSender</span><span class="w"> </span><span class="n">sender</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 通过构造函数注入依赖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">MessageService</span><span class="p">(</span><span class="n">MessageSender</span><span class="w"> </span><span class="n">sender</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">sender</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sender</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">processMessage</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用MessageSender接口发送消息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sender</span><span class="p">.</span><span class="na">sendMessage</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用EmailSender发送消息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MessageSender</span><span class="w"> </span><span class="n">emailSender</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EmailSender</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MessageService</span><span class="w"> </span><span class="n">emailService</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MessageService</span><span class="p">(</span><span class="n">emailSender</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">emailService</span><span class="p">.</span><span class="na">processMessage</span><span class="p">(</span><span class="s">&#34;Hello via Email!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用SmsSender发送消息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MessageSender</span><span class="w"> </span><span class="n">smsSender</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SmsSender</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MessageService</span><span class="w"> </span><span class="n">smsService</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MessageService</span><span class="p">(</span><span class="n">smsSender</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">smsService</span><span class="p">.</span><span class="na">processMessage</span><span class="p">(</span><span class="s">&#34;Hello via SMS!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="接口隔离原则">接口隔离原则</h3>
+<p>使用多个小的专门的接口，而不要使用一个大的总接口。具体而言，接口隔离原则体现在，接口应该是内聚的，应该避免“胖”接口。
+一个类对另外一个类的依赖应该建立在最小的接口上，不要强迫依赖不用的方法，这是一种接口污染。
+接口有效地将细节和抽象隔离，体现了对抽象编程的一切好处，接口隔离强调接口的单一性，而胖接口存在明显的弊端，会导致实现的类型必须完全实现接口的所有方法、属性等。
+某些时候，实现类并非需要所有的接口定义，在设计上这是“浪费”，而且在实施上这会带来潜在的问题，对胖接口的修改将导致一连串的客户端程序需要修改，有时候这是一种灾难。
+在这种情况下，应该将胖接口<strong>分离</strong>为多个特点的定制化方法，使得客户端仅仅依赖于它们的实际调用的方法，从而解除了客户端不会依赖于它们不用的方法。</p>
+<p>分离的手段主要有以下两种：</p>
+<ul>
+<li>委托分离，通过增加一个新的类型来委托客户的请求，隔离客户和接口的直接依赖，但是会增加系统的开销。</li>
+<li>多重继承分离，通过接口多继承来实现客户的需求，这种方式是较好的。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FuncImpl</span><span class="w"> </span><span class="n">func</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FuncImpl</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">func</span><span class="p">.</span><span class="na">func1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">func</span><span class="p">.</span><span class="na">func2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">func</span><span class="p">.</span><span class="na">func3</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Function1</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果将接口中的方法都写在一个接口就会造成实现该接口就要重写该接口所有方法。</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 当然Java 8 接口可以有实现，降低了维护成本，解了决该问题；</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 但是我们还是应当遵循该原则，使得接口看起来更加清晰</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// void func2();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// void func3();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Function2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">func2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Function3</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">func3</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">FuncImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Function1</span><span class="p">,</span><span class="n">Function2</span><span class="p">,</span><span class="n">Function3</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am function1 impl&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func2</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am function2 impl&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func3</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am function3 impl&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="里氏替换原则">里氏替换原则</h3>
+<p>里氏替换原则这一思想体现为对继承机制的约束规范，只有子类能够替换基类时，才能保证系统在运行期内识别子类，这是保证继承复用的基础。
+在父类和子类的具体行为中，必须严格把握继承层次中的关系和特征，将基类替换为子类，程序的行为不会发生任何变化。
+同时这一约束反过来则是不成立的，子类可以替换基类，但是基类不一定能替换子类。
+里氏替换原则，主要着眼于对抽象和多态建立在继承的基础上，因此只有遵循了里氏替换原则，才能保证继承复用是可靠地。</p>
+<p>实现的方法是面向接口编程，即将公共部分抽象为基类接口或抽象类，在子类中通过覆写父类的方法实现新的方式支持同样的职责。
+里氏替换原则是关于继承机制的设计原则，违反了里氏替换原则就必然导致违反开放封闭原则。
+里氏替换原则能够保证系统具有良好的拓展性，同时实现基于多态的抽象机制，能够减少代码冗余，避免运行期的类型判别。</p>
+<p>简单来说就是子类可以扩展父类的功能，而不应该改变父类原有的功能。
+如果通过重写父类方法来完成新的功能，这样写起来虽然简单，但整个体系的可复用性会非常差，特别是运用多态比较频繁时，程序运行出错的概率会非常大。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Rectangle</span><span class="w"> </span><span class="n">rectangle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Rectangle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">rectangle</span><span class="p">.</span><span class="na">setWidth</span><span class="p">(</span><span class="n">20</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">rectangle</span><span class="p">.</span><span class="na">setHeight</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">(</span><span class="n">rectangle</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">print</span><span class="p">(</span><span class="n">rectangle</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=======================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Rectangle</span><span class="w"> </span><span class="n">square</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Square</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">square</span><span class="p">.</span><span class="na">setWidth</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 因为 Square类 重写了父类 setWidth setHeight 方法，会导致 while 循环变成一个无限循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">resize</span><span class="p">(</span><span class="n">square</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">print</span><span class="p">(</span><span class="n">square</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">resize</span><span class="p">(</span><span class="n">Rectangle</span><span class="w"> </span><span class="n">rectangle</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">rectangle</span><span class="p">.</span><span class="na">getWidth</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">rectangle</span><span class="p">.</span><span class="na">getHeight</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">rectangle</span><span class="p">.</span><span class="na">setHeight</span><span class="p">(</span><span class="n">rectangle</span><span class="p">.</span><span class="na">getHeight</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">print</span><span class="p">(</span><span class="n">Rectangle</span><span class="w"> </span><span class="n">rectangle</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">rectangle</span><span class="p">.</span><span class="na">getWidth</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">rectangle</span><span class="p">.</span><span class="na">getHeight</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 正方形</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Square</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Rectangle</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setWidth</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">width</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setWidth</span><span class="p">(</span><span class="n">width</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setHeight</span><span class="p">(</span><span class="n">width</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHeight</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">height</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setWidth</span><span class="p">(</span><span class="n">height</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setHeight</span><span class="p">(</span><span class="n">height</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 长方形</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Rectangle</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setWidth</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">width</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">width</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHeight</span><span class="p">(</span><span class="n">Integer</span><span class="w"> </span><span class="n">height</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">height</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getWidth</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">width</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getHeight</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">height</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="合成复用原则">合成复用原则</h3>
+<p>在面向对象设计中，可以通过两种方法在不同的环境中复用已有的设计和实现，即通过组合/聚合关系或通过继承。
+首先应该考虑使用组合/聚合，因为组合/聚合可以使系统更加灵活，降低类与类之间的耦合度，一个类的变化对其他类造成的影响相对较少；
+其次才考虑继承，在使用继承时，需要严格遵循里氏代换原则，有效使用继承会有助于对问题的理解，降低复杂度，而滥用继承反而会增加系统构建和维护的难度以及系统的复杂度，因此需要慎重使用继承复用。</p>
+<p>尽量使用对象组合，而不是继承来达到复用的目的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 引擎接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Engine</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 电动引擎</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ElectricEngine</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Engine</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">start</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Electric engine starts...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 燃油引擎</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">GasEngine</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Engine</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">start</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Gas engine starts...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 汽车类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Car</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Engine</span><span class="w"> </span><span class="n">engine</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Car</span><span class="p">(</span><span class="n">Engine</span><span class="w"> </span><span class="n">engine</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">engine</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">engine</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">start</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">engine</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Car starts...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个电动引擎汽车</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Engine</span><span class="w"> </span><span class="n">electricEngine</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ElectricEngine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Car</span><span class="w"> </span><span class="n">electricCar</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Car</span><span class="p">(</span><span class="n">electricEngine</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">electricCar</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=======================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建一个燃油引擎汽车</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Engine</span><span class="w"> </span><span class="n">gasEngine</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">GasEngine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Car</span><span class="w"> </span><span class="n">gasCar</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Car</span><span class="p">(</span><span class="n">gasEngine</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">gasCar</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="迪米特法则">迪米特法则</h3>
+<p>迪米特法则又叫最少知识原则，就是说一个对象应当对其他对象有尽可能少的了解。其核心思想为，降低类之间的耦合。
+如果类与类之间的关系越密切，耦合度越大，当一个类发生改变时，对另一个类的影响也越大，所以一个对象应该对其他对象有最少的了解。
+通俗地讲，一个类应该对自己需要耦合或调用的类知道得最少，被耦合或调用的类的内部是如何复杂都和我没关系，那是你的事情，我就知道你提供的<code>public</code>方法，我就调用这么多，其他的一概不关心。
+迪米特法则其根本思想，是强调了类之间的松耦合。类之间的耦合越弱，越有利于复用，一个处在弱耦合的类被修改，不会对有关系的类造成搏击，也就是说，信息的隐藏促进了软件的复用。</p>
+<p>迪米特法则还有个更简单的定义，只与直接的<strong>朋友</strong>交谈，不跟“陌生人”说话。</p>
+<blockquote>
+<p>朋友定义：每个对象都会与其他对象有耦合关系，只要两个对象之间有耦合关系，我们就说这两个对象之间是朋友关系。<br>
+耦合的方式很多：依赖、关联、组合、聚合等。其中，我们称出现成员变量、方法参数、方法返回值中的类为直接的朋友，而出现在局部变量中的类不是直接的朋友。也就是说，陌生的类最好不要以局部变量的形式出现在类的内部。</p>
+</blockquote>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 学生类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Student</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Class</span><span class="w"> </span><span class="n">myClass</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Student</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="w"> </span><span class="n">myClass</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">myClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myClass</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 查询自己的班级信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">queryClassInfo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">className</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myClass</span><span class="p">.</span><span class="na">getClassName</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; is in class &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">className</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 班级类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Class</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">className</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Class</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">className</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">className</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">className</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getClassName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">className</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 老师类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Teacher</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Teacher</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 不符合迪米特法则的方法示例，直接返回班级名</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// public String getStudentClass(Student student) {</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//     return student.myClass.getClassName();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// }</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 通过学生对象调用公共方法获取班级信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getStudentClass</span><span class="p">(</span><span class="n">Student</span><span class="w"> </span><span class="n">student</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">student</span><span class="p">.</span><span class="na">queryClassInfo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建班级</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Class</span><span class="w"> </span><span class="n">class1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Class</span><span class="p">(</span><span class="s">&#34;Class 1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建学生并设置班级</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Student</span><span class="w"> </span><span class="n">student</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Student</span><span class="p">(</span><span class="s">&#34;Alice&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">class1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 学生查询自己的班级信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">student</span><span class="p">.</span><span class="na">queryClassInfo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=======================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建老师并查询学生的班级信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Teacher</span><span class="w"> </span><span class="n">teacher</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Teacher</span><span class="p">(</span><span class="s">&#34;Mr. Smith&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">studentClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">teacher</span><span class="p">.</span><span class="na">getStudentClass</span><span class="p">(</span><span class="n">student</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">student</span><span class="p">.</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; is in class &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">studentClass</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="面向对象三大特性">面向对象三大特性</h2>
+<p>面向对象编程具有三大基本特性，它们是：封装、继承、多态。这些特性是面向对象编程语言如Java、Python等的基础。
+面向对象编程的三大特性共同作用，使得程序设计更加灵活、可扩展和易于维护。
+封装提供了数据的安全性和访问控制，继承实现了代码的重用和层次化设计，多态增加了代码的适应性和灵活性。这些特性共同构成了面向对象编程范式的核心，是现代软件开发中广泛应用的重要基础。</p>
+<h3 id="封装">封装</h3>
+<p>封装是面向对象方法的重要原则，就是把对象的属性和操作（或服务）结合为一个独立的整体，并尽可能隐藏对象的内部实现细节。
+简单的说，一个类就是一个封装了数据以及操作这些数据的代码的逻辑实体。在一个对象内部，某些代码或某些数据可以是私有的，不能被外界访问。
+通过这种方式，对象对内部数据提供了不同级别的保护，以防止程序中无关的部分意外的改变或错误的使用了对象的私有部分。</p>
+<p>良好的封装能够减少耦合，提高了可维护性和灵活性以及可重用性，允许类内部结构自由修改，并对成员变量进行精确控制，同时有效隐藏信息和实现细节。
+封装的目的是增强安全性和简化编程，使用者不必了解具体的实现细节，而只是要通过外部接口以特定的访问权限来使用类的成员。
+其中包括<code>private</code>、<code>protected</code>和<code>public</code>三个访问权限修饰符，如果不加修饰符，则表示包级可见（<code>default</code>）。</p>
+<table>
+<thead>
+<tr>
+<th>修饰符</th>
+<th>当前类</th>
+<th>同一包下</th>
+<th>其他包的子类</th>
+<th>不同包的子类</th>
+<th>其他包</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>public</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+</tr>
+<tr>
+<td>protected</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y/N</td>
+<td>N</td>
+</tr>
+<tr>
+<td>default</td>
+<td>Y</td>
+<td>Y</td>
+<td>Y</td>
+<td>N</td>
+<td>N</td>
+</tr>
+<tr>
+<td>private</td>
+<td>Y</td>
+<td>N</td>
+<td>N</td>
+<td>N</td>
+<td>N</td>
+</tr>
+</tbody>
+</table>
+<p>这四种访问权限的控制符能够控制类中成员的可见性，当然需要满足在不使用Java反射的情况下。</p>
+<ul>
+<li><code>private</code>：仅在定义它们的类内部可见。</li>
+<li><code>protected</code>：同一个包内的类和该类的子类可以访问。</li>
+<li><code>default</code>：包级可见性，同一个包内的类可以访问。</li>
+<li><code>public</code>：任何类都可以访问。</li>
+</ul>
+<p>设计良好的模块会隐藏所有的实现细节，把它的<code>API</code>与它的实现清晰地隔离开来。
+模块之间只通过它们的<code>API</code>进行通信，一个模块不需要知道其他模块的内部工作情况，这个概念被称为信息隐藏或封装。因此访问权限应当尽可能地使每个类或者成员不被外界访问。
+如果子类的方法重写了父类的方法，那么子类中该方法的访问级别不允许低于父类的访问级别。这是为了确保可以使用父类实例的地方都可以使用子类实例，也就是确保满足里氏替换原则。</p>
+<p>某个类的字段决不能是公有的，因为这么做的话就失去了对这个字段修改行为的控制，其他类可以对其随意修改。
+下面的例子中，<code>AccessExample</code>拥有id公有字段，如果在某个时刻，我们想要使用<code>int</code>存储<code>id</code>字段，那么就需要修改所有类中的代码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AccessExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// public int id;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>可以使用公有的<code>getter</code>和<code>setter</code>方法来替换公有字段，这样的话就可以控制对字段的修改行为，实现了封装。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AccessExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getId</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">id</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setId</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">id</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">id</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>但是也有例外，如果是包级私有的类或者私有的嵌套类，那么直接暴露成员不会有特别大的影响。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AccessWithInnerClassExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">class</span> <span class="nc">InnerClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">InnerClass</span><span class="w"> </span><span class="n">innerClass</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">AccessWithInnerClassExample</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">innerClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InnerClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getValue</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">innerClass</span><span class="p">.</span><span class="na">x</span><span class="p">;</span><span class="w">  </span><span class="c1">// 直接访问</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="继承">继承</h3>
+<p>继承可以使用父类的所有功能，并在无需重新编写原来类的情况下对这些功能进行扩展。 通过继承创建的新类称为“子类”或“派生类”，被继承的类称为“基类”、“父类”或“超类”。
+继承的过程，就是从一般到特殊的过程。继承概念的实现方式有两种，<strong>实现继承</strong>与<strong>接口继承</strong>。实现继承是指直接使用基类的属性和方法而无需额外编码的能力；接口继承是指仅使用属性和方法的名称、但是子类必须提供实现的能力。</p>
+<ul>
+<li>实现继承：如果多个类的某个部分的功能相同，那么可以抽象出一个类来，把相同的部分放到父类中，让他们继承这个类；</li>
+<li>接口继承：如果多个类处理的目标是一样的，但是处理的方法方式不同，那么就定义一个接口，也就是一个标准，让他们的实现这个接口，各自实现自己具体的处理方法来处理那个目标；</li>
+</ul>
+<p>继承的根本原因是因为要复用，而实现的根本原因是需要定义一个标准。</p>
+<h4 id="继承与组合">继承与组合</h4>
+<p>继承是实现复用代码的重要手段，但是继承会破坏封装；组合也是代码复用的重要方式，可以提供良好的封装性。</p>
+<table>
+<thead>
+<tr>
+<th>特性</th>
+<th>组合</th>
+<th>继承</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>优点</td>
+<td>不破坏封装，整体类与局部类之间松耦合，彼此相对独立；具有较好的可扩展性；支持动态组合，运行时可以选择不同类型的局部对象；整体类可以对局部类进行包装，提供新的接口。</td>
+<td>子类能自动继承父类的接口；支持扩展父类的功能；创建子类对象时无需创建父类对象。</td>
+</tr>
+<tr>
+<td>缺点</td>
+<td>整体类不能自动获得和局部类同样的接口；创建整体类对象时需要创建所有局部类的对象。</td>
+<td>破坏封装，子类与父类之间紧密耦合，子类依赖于父类的实现，缺乏独立性；增加系统结构的复杂度；不支持动态继承，子类无法选择不同的父类。</td>
+</tr>
+</tbody>
+</table>
+<p>在设计中，通常会同时使用继承和组合来实现代码的复用和关系建模，具体根据需求和设计原则来选择合适的关系模型。
+组合比继承更加灵活，所以在写代码如果这个功能组合和继承都能够完成，那么应该优先选择组合，但是继承在一些场景还是要优先于组合的：</p>
+<ul>
+<li>继承要慎用，其使用场合仅限于你确信使用该技术有效的情况。一个判断方法是，问一问自己是否需要从新类向基类进行向上转型。如果是必须的，则继承是必要的。反之则应该好好考虑是否需要继承。</li>
+<li>只有当子类真正是超类的子类型时，才适合用继承。换句话说，对于两个类A和B，只有当两者之间确实存在<code>is-a</code>关系的时候，类B才应该继承类A。</li>
+</ul>
+<p>通过下列代码可以发现，子类可以访问父类的成员变量方法，并且通过重写可以改变父类方法实现从而破坏了封装性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 继承</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">B</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">B</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">b</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;I am super class ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">B</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">A</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 调用父类成员 </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">t</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="kd">super</span><span class="p">.</span><span class="na">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在继承结构中，父类的内部细节对于子类是可见的。所以我们通常也可以说通过继承的代码复用是一种白盒式代码复用。
+如果基类的实现发生改变，那么派生类的实现也将随之改变，这样就导致了子类行为的不可预知性。</p>
+<p>为了保证父类有良好的封装性，不会对子类随意更改，设计父类时应遵循以下原则：</p>
+<ul>
+<li>尽量隐藏父类的内部数据.尽量把所有父类的所有成员变量都用<code>private</code>修饰，不要让子类直接访问父类的成员；</li>
+<li>不要让子类随意的修改访问父类的方法，父类中那些仅为辅助其他的工具方法，应该使用<code>private</code>修饰，让子类无法访问该方法。如果父类中的方法需要被外部类调用，则需以<code>public</code>修饰，但又不希望重写父类方法可以使用<code>final</code>来修饰方法；
+但如果希望父类某个方法被重写，但又不希望其他类访问自由，可以使用<code>protected</code>修饰；</li>
+<li>尽量不要在父类构造器中调用将要被子类重写的方法；</li>
+</ul>
+<p><code>super</code>关键字通常用在继承的子类中，通常有以下作用：</p>
+<ul>
+<li>访问父类的构造函数：可以使用<code>super</code>函数访问父类的构造函数，从而委托父类完成一些初始化的工作。
+应该注意到，子类一定会调用父类的构造函数来完成初始化工作，一般是调用父类的默认构造函数，如果子类需要调用父类其它构造函数，那么就可以使用<code>super</code>函数。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Parent</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Parent constructor&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Child</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">();</span><span class="w"> </span><span class="c1">// 调用父类构造方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Child constructor&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>访问父类的成员：如果子类重写了父类的某个方法，可以通过使用<code>super </code>关键字来引用父类的方法实现。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Parent&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Child&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">displayName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Child&#39;s name: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">     </span><span class="c1">// 输出 Child</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Parent&#39;s name: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 Parent</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>在子类中调用父类的方法：这对于子类重写父类方法时，希望在子类方法中调用父类方法的场景非常有用。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Parent&#39;s display method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">display</span><span class="p">();</span><span class="w"> </span><span class="c1">// 调用父类的display方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Child&#39;s display method&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>继承是类与类或者接口与接口之间最常见的关系，继承是一种<code>is-a</code>的关系。而组合强调的是整体与部分、拥有的关系，即<code>has-a</code>的关系。
+组合是把旧类对象作为新类对象的成员变量组合进来，用以实现新类的功能。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">B</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">B</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">b</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;I am super class ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">B</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">B</span><span class="p">(</span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 复用 A 类提供的 test 方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">a</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>组合是通过对现有的对象进行拼装产生新的、更复杂的功能。因为在对象之间，各自的内部细节是不可见的，所以我们也说这种方式的代码复用是黑盒式代码复用。因为组合中一般都定义一个类型，所以在编译期根本不知道具体会调用哪个实现类的方法。</p>
+<h4 id="抽象类与接口">抽象类与接口</h4>
+<p>抽象类和接口也是Java继承体系中的重要组成部分。
+抽象类是用来捕捉子类的通用特性的，而接口则是抽象方法的集合；抽象类不能被实例化，只能被用作子类的超类，是被用来创建继承层级里子类的模板，而接口只是一种形式，自身不能做任何事情。</p>
+<p>抽象类和抽象方法都使用<code>abstract</code>关键字进行声明。如果一个类中包含抽象方法，那么这个类必须声明为抽象类。
+抽象类和普通类最大的区别是，抽象类不能被实例化，需要继承抽象类才能实例化其子类。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractClassExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func2</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;func2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractExtendClassExample</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractClassExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;func1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实例化抽象类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// AbstractClassExample ac1 = new AbstractClassExample(); </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 实例化抽象类子类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// AbstractClassExample ac2 = new AbstractExtendClassExample();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// ac2.func1();</span><span class="w">
+</span></span></span></code></pre></div><p>接口是抽象类的延伸，在Java8之前，它可以看成是一个完全抽象的类，也就是说它不能有任何的方法实现。
+但从Java8 开始，接口也可以拥有默认的方法实现，这是因为不支持默认方法的接口的维护成本太高了。在Java8之前，如果一个接口想要添加新的方法，那么要修改所有实现了该接口的类，现在不用修改所有实现该接口的类。</p>
+<p>接口中的成员（字段、方法）默认都是<code>public</code>的，并且不允许定义为<code>private</code>或者 <code>protected</code>。
+接口的字段默认都是用<code>static</code>和<code>final</code>修饰的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">InterfaceExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">default</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func2</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;func2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">123</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// int y;               // Variable &#39;y&#39; might not have been initialized</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">       </span><span class="c1">// Modifier &#39;public&#39; is redundant for interface fields</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// private int k = 0;   // Modifier &#39;private&#39; not allowed here</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// protected int l = 0; // Modifier &#39;protected&#39; not allowed here</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// private void fun3(); // Modifier &#39;private&#39; not allowed here</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">InterfaceImplementExample</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">InterfaceExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func1</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;func1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>Java的接口可以多继承：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">interface</span> <span class="nc">Action</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Serializable</span><span class="p">,</span><span class="n">AutoCloseable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">	</span><span class="c1">// to do ...</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>从设计层面上看，抽象类提供了一种<code>is-a</code>关系，那么就必须满足里式替换原则，即子类对象必须能够替换掉所有父类对象。
+而接口更像是一种 <code>like-a</code> 关系，它只是提供一种方法实现契约，并不要求接口和实现接口的类具有 <code>is-a</code> 关系。
+抽象类是一种自下而上的思想，而接口是一种自上而下的思想。抽象类是将多个类的公共特点聚合到同一个类中，然后实现父类的方法；接口更像是对类的一种约束，其他类调用实现某接口的类。</p>
+<p>从语法角度来看，一个类可以实现多个接口，但是不能继承多个抽象类。接口的字段只能是<code>static</code>和<code>final</code>类型的，而抽象类的字段没有这种限制，接口的成员只能是<code>public</code>的，而抽象类的成员可以有多种访问权限。</p>
+<p>接口适合的情况包括需要让不相关的类都实现相同方法，例如实现<code>Comparable</code>接口中的<code>compareTo</code>方法，以及需要实现类似多重继承的效果。
+抽象类则更适合于多个相关类需要共享代码逻辑，或者需要控制继承来的成员访问权限，以及需要继承非静态和非常量字段的场景。选择使用接口或抽象类取决于设计需求和代码结构的具体情况。</p>
+<p>在很多情况下，接口优先于抽象类。因为接口没有抽象类严格的类层次结构要求，可以灵活地为一个类添加行为。
+并且从Java8开始，接口也可以有默认的方法实现，使得修改接口的成本也变的很低。</p>
+<h3 id="多态">多态</h3>
+<p>多态是面向对象编程中的一个重要概念，它允许对象以多种形式出现。
+在Java中，多态主要通过继承和接口来实现。多态性使得一个对象可以被看作是其本身的类型，也可以被看作是其父类或接口的类型。
+多态存在的前提，有类继承或者接口实现、子类要重写父类的方法、父类的引用指向子类的对象，如：<code>Parent p = new Child();</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">contextLoads</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am Parent ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">contextLoads</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am Child ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">mainTest</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Parent</span><span class="w"> </span><span class="n">child</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Child</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// i am Child ... </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">child</span><span class="p">.</span><span class="na">contextLoads</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>通过多态，可以将相似的操作封装在父类或接口中，子类只需要实现或重写这些操作，从而减少代码的重复。
+多态使得程序更加灵活和可扩展，可以在不修改现有代码的情况下增加新的功能。
+通过多态，可以用接口来定义一组可互换的操作，使得代码更具通用性。
+但多态不能使用子类特有的方法和属性，在编写代码期间使用多态调用方法或属性时，编译工具首先会检查父类中是否有该方法和属性，如果没有则会编译报错。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">contextLoads</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am Parent ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Child</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Parent</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w">  </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;child&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">contextLoads</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am Child ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">mainTest</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Parent</span><span class="w"> </span><span class="n">child</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Child</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译报错: 无法解析 &#39;Parent&#39; 中的方法 &#39;test&#39;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">child</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 编译报错: 不能解决符号 &#39;c&#39;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">child</span><span class="p">.</span><span class="na">c</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="重写与重载">重写与重载</h4>
+<p>多态分为两种主要类型：静态绑定（编译时多态）和动态绑定（运行时多态）。</p>
+<p>动态绑定发生在运行时，主要通过方法重写实现，我们通常所说的多态就是指这个。重写存在于继承体系中，指子类实现了一个与父类在方法声明上完全相同的一个方法。
+动态绑定的关键在于：父类的引用可以指向子类的对象，方法调用在运行时根据实际对象类型来决定执行哪个方法。</p>
+<p>为了满足里式替换原则，重写有以下三个限制，使用<code>@Override</code>注解，可以让编译器帮忙检查是否满足这三个限制条件。</p>
+<ul>
+<li>子类方法的访问权限必须大于等于父类方法；</li>
+<li>子类方法的返回类型必须是父类方法返回类型或为其子类型；</li>
+<li>子类方法抛出的异常类型必须是父类抛出异常类型或为其子类型；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Animal</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">makeSound</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Animal makes a sound&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">makeSound</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Dog barks&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Cat</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">makeSound</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Cat meows&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">TestDynamicBinding</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">myDog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">myCat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Cat</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">myDog</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"> </span><span class="c1">// 输出 &#34;Dog barks&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">myCat</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"> </span><span class="c1">// 输出 &#34;Cat meows&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>静态绑定发生在编译时，主要通过方法重载实现。
+重载是在一个类里面，方法名字相同，但参数类型、个数、顺序至少有一个不同，返回类型可以相同也可以不同。应该注意的是，只有返回值不同，其它都相同不算是重载。编译器在编译时决定调用哪一个方法。
+每个重载的方法都必须有一个独一无二的参数类型列表。最常用的地方就是构造器的重载。</p>
+<p>重载规则：</p>
+<ul>
+<li>被重载的方法必须改变参数列表(参数个数或类型不一样)；</li>
+<li>被重载的方法可以改变返回类型；</li>
+<li>被重载的方法可以改变访问修饰符；</li>
+<li>被重载的方法可以声明新的或更广的检查异常；</li>
+<li>方法能够在同一个类中或者在一个子类中被重载；</li>
+<li>无法以返回值类型作为重载函数的区分标准；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Overloading</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">test</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;test1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;test2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">   
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//以下两个参数类型顺序不同</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;test3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;returntest3&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">   
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="p">,</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;test4&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;returntest4&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">   
+</span></span></span><span class="line"><span class="cl"><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Overloading</span><span class="w"> </span><span class="n">o</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Overloading</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">o</span><span class="p">.</span><span class="na">test</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">o</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">o</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="s">&#34;test3&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">o</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="s">&#34;test4&#34;</span><span class="p">,</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>方法的重写和重载是Java多态性的不同表现，重写是父类与子类之间多态性的一种表现，重载可以理解成多态的具体表现形式。
+方法重载是一个类中定义了多个方法名相同，而他们的参数的数量不同或数量相同而类型和次序不同，则称为方法的重载。
+方法重写是在子类存在方法与父类的方法的名字相同，而且参数的个数与类型一样，返回值也一样的方法，就称为重写。
+方法重载是一个类的多态性的表现，而方法重写是子类与父类的一种多态性表现。</p>
+<h2 id="设计模式">设计模式</h2>
+<p>设计模式是一套被反复使用、多数人知晓的、经过分类编目的、代码设计经验的总结，使用设计模式是为了可重用代码、让代码更容易被他人理解、保证代码可靠性、高内聚低耦合。
+虽然<a href="https://baike.baidu.com/item/GoF/6406151?fr=aladdin">GoF</a>设计模式只有23个，但是它们各具特色，每个模式都为某一个可重复的设计问题提供了一套解决方案。
+根据它们的用途，设计模式可分为创建型，结构型和行为型三种，其中创建型模式主要用于描述如何创建对象，结构型模式主要用于描述如何实现类或对象的组合，行为型模式主要用于描述类或对象怎样交互以及怎样分配职责。
+在GoF23种设计模式中包含5种创建型设计模式、7种结构型设计模式和11种行为型设计模式。此外，根据某个模式主要是用于处理类之间的关系还是对象之间的关系，设计模式还可以分为类模式和对象模式。</p>
+<p>设计模式练习网站: <a href="https://java-design-patterns.com/patterns">https://java-design-patterns.com/patterns</a></p>
+<table>
+<thead>
+<tr>
+<th>设计模式类型</th>
+<th>设计模式名称</th>
+<th>介绍</th>
+<th>学习难度</th>
+<th>使用频率</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>创建型模式(6种)</td>
+<td>单例模式</td>
+<td>保证一个类仅有一个对象，并提供一个访问它的全局访问点。</td>
+<td>★☆☆☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>简单工厂模式</td>
+<td>定义一个工厂类，它可以根据参数的不同返回不同类的实例，被创建的实例通常都具有共同的父类。</td>
+<td>★★☆☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>工厂方法模式</td>
+<td>定义一个用于创建对象的接口，让子类决定将哪一个类实例化。</td>
+<td>★★☆☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>抽象工厂模式</td>
+<td>提供一个创建一系列相关或相互依赖对象的接口，而无需指定它们的具体类。</td>
+<td>★★★★☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>原型模式</td>
+<td>使用原型实例指定创建对象的种类，并且通过拷贝这些原型创建新的对象。</td>
+<td>★★★☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>建造者模式</td>
+<td>将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示。</td>
+<td>★★★★☆</td>
+<td>★★☆☆☆</td>
+</tr>
+<tr>
+<td>结构型模式(7种)</td>
+<td>适配器模式</td>
+<td>将一个类的接口转换成客户希望的另一个接口。适配器模式使得原本由于接口不兼容而不能一起工作的那些类可以一起工作。</td>
+<td>★★☆☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>桥接模式</td>
+<td>将抽象部分与它的实现部分分离，使他们都可以独立地变化。</td>
+<td>★★★☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>组合模式</td>
+<td>组合多个对象形成树形结构以表示具有“整体—部分”关系的层次结构。组合模式对单个对象和组合对象的使用具有一致性。</td>
+<td>★★★☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>装饰模式</td>
+<td>动态地给一个对象增加一些额外的职责，就增加对象功能来说，装饰模式比生成子类实现更为灵活。</td>
+<td>★★★☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>外观模式</td>
+<td>为子系统中的一组接口提供一个统一的入口。外观模式定义了一个高层接口，这个接口使得这一子系统更加容易使用。</td>
+<td>★☆☆☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>享元模式</td>
+<td>运用共享技术有效地支持大量细粒度的对象。</td>
+<td>★★★★☆</td>
+<td>★☆☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>代理模式</td>
+<td>为其他对象提供一个代理以控制对这个对象的访问。</td>
+<td>★★★☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td>行为模式(11种)</td>
+<td>职责链模式</td>
+<td>为解除请求的发送者和接收者之间的耦合，而使多个对象都有机会处理这个请求。将这些对象连成一条链，并沿着这条链传递该请求，直到有对象处理它。</td>
+<td>★★★☆☆</td>
+<td>★★☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>命令模式</td>
+<td>将一个请求封装为一个对象，从而使你可用不同的请求对客户进行参数化，对请求排队或记录请求日志，以及支持可取消的操作。</td>
+<td>★★★☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>解释器模式</td>
+<td>定义一个语言，定义它的文法的一种表示，并定义一个解释器，该解释器使用该表示来解释语言中的句子。</td>
+<td>★★★★★</td>
+<td>★☆☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>迭代器模式</td>
+<td>提供一种方法顺序访问一个聚合对象中各个元素，而又不需暴露该对象的内部表示。</td>
+<td>★★★☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>中介者模式</td>
+<td>用一个中介对象来封装一系列的对象交互。中介者使各对象不需要显示地相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互。</td>
+<td>★★★☆☆</td>
+<td>★★☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>备忘录模式</td>
+<td>在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保持该状态，这样以后就可以将该对象恢复到保存的状态。</td>
+<td>★★☆☆☆</td>
+<td>★★☆☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>观察者模式</td>
+<td>定义对象间的一种一对多的依赖关系，以便当一个对象的状态发生改变时，所有依赖于它的对象都得到通知并自动刷新。</td>
+<td>★★★☆☆</td>
+<td>★★★★★</td>
+</tr>
+<tr>
+<td></td>
+<td>状态模式</td>
+<td>允许一个对象在其内部状态改变时改变它的行为。对象看起来似乎修改了它所属的类。</td>
+<td>★★★☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>策略模式</td>
+<td>定义一系列的算法，把它们一个个封装起来，并且使他们可相互替换。本模式使得算法的变化可以独立于使用它的客户。</td>
+<td>★☆☆☆☆</td>
+<td>★★★★☆</td>
+</tr>
+<tr>
+<td></td>
+<td>模板方法模式</td>
+<td>定义一个操作中的算法的骨架，而将一些步骤延迟到子类。</td>
+<td>★★☆☆☆</td>
+<td>★★★☆☆</td>
+</tr>
+<tr>
+<td></td>
+<td>访问者模式</td>
+<td>表示一个作用于某对象结构中的各元素的操作。它使你可以在不改变各元素类别的前提下定义作用于这些元素的新操作。</td>
+<td>★★★★☆</td>
+<td>★☆☆☆☆</td>
+</tr>
+</tbody>
+</table>
+<h3 id="单例模式">单例模式</h3>
+<p>确保某一个类只有一个实例，而且自行实例化并向整个系统提供这个实例，这个类称为单例类，它提供全局访问的方法。单例模式是一种对象创建型模式。
+单例模式设计就是采用一定的方法保证在整个程序中，对某个类只能存在一个对象的实例，并且该类只提供一个取得其对象实例的方法。</p>
+<p>单例模式作用：</p>
+<ul>
+<li>在内存里只有一个实例，减少了内存的开销，尤其是频繁的创建和销毁实例（比如网站首页页面缓存）；</li>
+<li>避免对资源的多重占用（比如写文件操作）；</li>
+</ul>
+<p>单例模式主要应用在需要频繁的进行创建和销毁的对象、创建对象时耗时过多或耗费资源过多、重量级对象，但又经常用到的对象、工具类对象、频繁访问数据库或文件的对象(比如数据源、<code>session</code> 工厂等)。
+单例模式在Java中有6种实现。</p>
+<table>
+<thead>
+<tr>
+<th>名称</th>
+<th>优点</th>
+<th>缺点</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>饿汉式</td>
+<td>线程安全，写法简单</td>
+<td>不懒加载，可能造成浪费</td>
+</tr>
+<tr>
+<td>懒汉式(线程不安全)</td>
+<td>懒加载</td>
+<td>线程不安全</td>
+</tr>
+<tr>
+<td>懒汉式(线程安全)</td>
+<td>线程安全，懒加载</td>
+<td>效率很低，反序列化破坏单例</td>
+</tr>
+<tr>
+<td>双重校验锁</td>
+<td>线程安全，懒加载</td>
+<td>反序列化破坏单例</td>
+</tr>
+<tr>
+<td>静态内部类式</td>
+<td>线程安全，懒加载</td>
+<td>反序列化破坏单例</td>
+</tr>
+<tr>
+<td>枚举式</td>
+<td>防止反射攻击，反序列化创建对象，写法简单</td>
+<td>不能传参，不能继承其他类</td>
+</tr>
+</tbody>
+</table>
+<h4 id="饿汉式">饿汉式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这种写法比较简单，就是在类加载的时候就完成实例化。避免了线程同步问题。但是在类装载的时候就完成实例化，没有达到懒加载的效果。如果从始至终从未使用过这个实例，则会造成内存的浪费。</p>
+<h4 id="线程不安全的懒汉式">线程不安全的懒汉式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">instance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>起到了懒加载的效果，但是只能在单线程下使用。如果在多线程下，一个线程进入了<code>if (singleton == null)</code>判断语句块，还未来得及往下执行，另一个线程也通过了这个判断语句，这时便会产生多个实例，所以在多线程环境下不可使用这种方式。</p>
+<h4 id="线程安全的懒汉式">线程安全的懒汉式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">instance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>虽然解决了线程安全问题但是效率太低了，每个线程在想获得类的实例时候，执行<code>getInstance()</code>方法都要进行同步。而其实这个方法只执行一次实例化代码就够了，后面的想获得该类实例，直接 <code>return</code>就行了。</p>
+<h4 id="双重校验锁">双重校验锁</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * volatile在这作用: 禁止JVM指令重排
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">instance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">Singleton</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">instance</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Double-Check</code>概念是多线程开发中常使用到的，如代码中所示，我们进行了两次<code>if (singleton == null)</code>检查，这样就可以保证线程安全了。
+这样，实例化代码只用执行一次，后面再次访问时，判断<code>if (singleton == null)</code>，直接<code>return</code>实例化对象，也避免的反复进行方法同步。</p>
+<h4 id="静态内部类式">静态内部类式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">class</span> <span class="nc">InnerClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">InnerClass</span><span class="p">.</span><span class="na">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这种方式同样利用了<code>classloder</code>的机制来保证初始化<code>instance</code>时只有一个线程，它跟饿汉式不同的是（很细微的差别）：饿汉式是只要<code>Singleton</code>类被装载了，那么<code>instance</code>就会被实例化（没有达到<code>lazy loading</code>效果），而这种方式是<code>Singleton</code>类被装载了，<code>instance</code>不一定被初始化。
+因为<code>SingletonHolder</code>类没有被主动使用，只有显示通过调用<code>getInstance</code>方法时，才会显示装载<code>SingletonHolder</code>类，从而实例化<code>instance</code>。
+想象一下，如果实例化<code>instance</code>很消耗资源，我想让他延迟加载，另外一方面，我不希望在<code>Singleton</code>类加载时就实例化，因为我不能确保<code>Singleton</code>类还可能在其他的地方被主动使用从而被加载，那么这个时候实例化<code>instance</code>显然是不合适的。
+这个时候，这种方式相比饿汉式更加合理。</p>
+<h4 id="枚举式">枚举式</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">enum</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">INSTAMCE</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Singleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>这种方式是《Effective Java》作者<code>Josh Bloch</code>提倡的方式，借助 JDK1.5 中添加的枚举来实现单例模式。不仅能避免多线程同步问题，而且还能防止反序列化重新创建新的对象。</p>
+<h4 id="单例与序列化">单例与序列化</h4>
+<p>上述单例模式6种写法除了枚举式单例外其他5种写法都存在序列化问题。序列化可以破坏单例，原因是序列化会通过反射调用无参数的构造方法创建一个新的对象。</p>
+<p>要想防止序列化对单例的破坏，只要在单例类中定义<code>readResolve</code>方法就可以解决该问题。原理是反序列化时，会通过反射的方式调用要被反序列化的类的<code>readResolve</code>方法，所以在这个方法中可以自定义序列化的方式。
+主要在<code>Singleton</code>类中定义<code>readResolve</code>方法，并在该方法中指定要返回的对象的生成策略，就可以防止单例被破坏。
+以双重校验锁为例，在该单例类中插入<code>readResolve</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Singleton</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Serializable</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">volatile</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">Singleton</span><span class="w"> </span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Singleton</span><span class="w"> </span><span class="nf">getSingleton</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">Singleton</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">singleton</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">singleton</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Singleton</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">readResolve</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">singleton</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="工厂模式">工厂模式</h3>
+<p>工厂模式是将实例化的对象代码提取出来，放到一个类中统一管理和维护，达到和主项目的依赖关系的解耦，从而提高项目的扩展和维护性。
+创建对象实例时不要直接<code>new</code>类，而是把这个<code>new</code>类的动作放在一个工厂的方法中并返回。不要让类继承具体的类，而是继承抽象类或者实现接口。</p>
+<h4 id="简单工厂模式">简单工厂模式</h4>
+<p>简单工厂模式，定义一个工厂类，它可以根据参数的不同返回不同类的实例，被创建的实例通常都具有共同的父类。
+因为在简单工厂模式中用于创建实例的方法是静态方法，因此简单工厂模式又被称为静态工厂方法模式，它属于类创建型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SimpleFactoryDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SimpleFactory</span><span class="p">.</span><span class="na">getTest</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SimpleFactoryImpl1</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SimpleFactoryInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am  simpleFactory 1 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SimpleFactoryImpl2</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">SimpleFactoryInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;i am  simpleFactory 2 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SimpleFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getTest</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">1</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">SimpleFactoryImpl1</span><span class="w"> </span><span class="n">simpleFactory</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SimpleFactoryImpl1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">simpleFactory</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="n">2</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">SimpleFactoryImpl2</span><span class="w"> </span><span class="n">simpleFactoryImpl2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SimpleFactoryImpl2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">simpleFactoryImpl2</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">default</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>简单工厂模式的优点是实现了对象创建和使用的分离，符合面向接口编程的思想，从而实现代码解耦。然而，如果工厂内包含的逻辑和职责过多，会导致代码臃肿和扩展困难。
+尤其是在产品类型较多时，添加新产品需要修改工厂逻辑，可能导致系统维护和扩展变得复杂。简单工厂模式适用于创建对象较少且业务逻辑不复杂的场景。</p>
+<h4 id="工厂方法模式">工厂方法模式</h4>
+<p>工厂方法模式，定义一个用于创建对象的接口，让子类决定将哪一个类实例化。工厂方法模式让一个类的实例化延迟到其子类。
+工厂方法模式又简称为工厂模式，又可称作虚拟构造器模式或多态工厂模式。工厂方法模式是一种类创建型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FactoryMethodDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FoodFactory</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ColdRiceNoodleFactory</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">f</span><span class="p">.</span><span class="na">getFood</span><span class="p">().</span><span class="na">eat</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 扩展需要增加产品及相应产品工厂并实现相关接口</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Food</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Food</span><span class="w"> </span><span class="nf">getFood</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RiceNoodle</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;eat rice noodle ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RiceNoodleFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FoodFactory</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Food</span><span class="w"> </span><span class="nf">getFood</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ColdRiceNoodle</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;eat cold rice noodle ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ColdRiceNoodleFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Food</span><span class="w"> </span><span class="nf">getFood</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>工厂方法模式是简单工厂模式的延伸，它继承了简单工厂模式的优点，同时还弥补了简单工厂模式的不足。
+使用工厂方法模式扩展时，无须修改抽象工厂和抽象产品提供的接口，无须修改客户端，也无须修改其他的具体工厂和具体产品，只要添加一个具体工厂和具体产品就可以了，这样系统的可扩展性也就变得非常好，完全符合“开闭原则”。
+但是在添加新产品时，需要编写新的具体产品类，而且还要提供与之对应的具体工厂类，系统中类的个数将成对增加，在一定程度上增加了系统的复杂度，有更多的类需要编译和运行，会给系统带来一些额外的开销。</p>
+<h4 id="抽象工厂模式">抽象工厂模式</h4>
+<p>抽象工厂模式，提供一个创建一系列相关或相互依赖对象的接口，而无须指定它们具体的类。抽象工厂模式又称为Kit模式，它是一种对象创建型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">interface</span> <span class="nc">Food</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ColdRiceNoodle</span><span class="w"> </span><span class="nf">getColdRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RiceNoodle</span><span class="w"> </span><span class="nf">getRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RiceNoodle</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;eating rice noodle&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ColdRiceNoodle</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">eat</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;eating cold rice noodle&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RiceNoodleFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="w"> </span><span class="nf">getColdRiceNoodle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="w"> </span><span class="nf">getRiceNoodle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ColdRiceNoodleFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FoodFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="w"> </span><span class="nf">getColdRiceNoodle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ColdRiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="w"> </span><span class="nf">getRiceNoodle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RiceNoodle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>抽象工厂模式是工厂方法模式的进一步延伸，仍然具有工厂方法和简单工厂的优点。抽象工厂模式隔离了具体类的生成，使得客户并不需要知道什么被创建。
+由于这种隔离，更换一个具体工厂就变得相对容易，所有的具体工厂都实现了抽象工厂中定义的那些公共接口，因此只需改变具体工厂的实例，就可以在某种程度上改变整个软件系统的行为。
+但是抽象工厂也存在一些缺点，增加新的产品等级结构麻烦，需要对原有系统进行较大的修改，甚至需要修改抽象层代码，这显然会带来较大的不便，违背了“开闭原则”。</p>
+<h3 id="原型模式">原型模式</h3>
+<p>在Java中通过<code>new</code>关键字创建的对象是非常繁琐的，在我们需要大量对象的情况下，原型模式就是我们可以考虑实现的方式。
+使用原型实例指定创建对象的种类，并且通过拷贝这些原型创建新的对象。原型模式是一种对象创建型模式。</p>
+<p>原型模式我们也称为克隆模式，即一个某个对象为原型克隆出来一个一模一样的对象，该对象的属性和原型对象一模一样，而且对于原型对象没有任何影响。
+原型模式的克隆方式有两种，浅克隆和深度克隆；浅克隆和深克隆的主要区别在于是否支持引用类型的成员变量的复制。</p>
+<h4 id="浅克隆">浅克隆</h4>
+<p>在浅克隆中，当对象被复制时只复制它本身和其中包含的值类型的成员变量，而引用类型的成员对象并没有复制。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ShallowClone</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">cloneHuman</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CloneHuman</span><span class="p">(</span><span class="s">&#34;黑色&#34;</span><span class="p">,</span><span class="s">&#34;大眼睛&#34;</span><span class="p">,</span><span class="s">&#34;高鼻梁&#34;</span><span class="p">,</span><span class="s">&#34;大嘴巴&#34;</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(</span><span class="n">123231231231L</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">clone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman</span><span class="p">)</span><span class="n">cloneHuman</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;头发：%s,眼睛：%s,鼻子：%s,嘴巴：%s,生日：%s&#34;</span><span class="p">,</span><span class="n">clone</span><span class="p">.</span><span class="na">getHair</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getEye</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getNodes</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getMouse</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getBirth</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;浅克隆，引用类型地址比较：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">cloneHuman</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">clone</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CloneHuman</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getHair</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHair</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getEye</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setEye</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getNodes</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNodes</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getMouse</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setMouse</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneHuman</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">,</span><span class="n">Date</span><span class="w"> </span><span class="n">brith</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">brith</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="nf">getBirth</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setBirth</span><span class="p">(</span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>Java提供的<code>Cloneable</code>接口和<code>Serializable</code>接口的代码非常简单，它们都是空接口，这种空接口也称为标识接口，标识接口中没有任何方法的定义，其作用是告诉JRE这些接口的实现类是否具有某个功能，如是否支持克隆、是否支持序列化等。</p>
+<p>应该注意的是，<code>clone</code>方法并不是<code>Cloneable</code>接口的方法，而是<code>Object</code>的一个<code>protected</code>方法。
+<code>Cloneable</code>接口只是规定，如果一个类没有实现<code>Cloneable</code>接口又调用了<code>clone()</code>方法，就会抛出 <code>CloneNotSupportedException</code>。</p>
+<h4 id="深克隆">深克隆</h4>
+<p>在深克隆中，除了对象本身被复制外，对象所包含的所有成员变量也将复制。
+深克隆有两种实现方式，第一种是在浅克隆的基础上实现，第二种是通过序列化和反序列化实现。</p>
+<p>在浅克隆的基础上实现：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DeepClone</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">cloneHuman</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CloneHuman</span><span class="p">(</span><span class="s">&#34;黑色&#34;</span><span class="p">,</span><span class="s">&#34;大眼睛&#34;</span><span class="p">,</span><span class="s">&#34;高鼻梁&#34;</span><span class="p">,</span><span class="s">&#34;大嘴巴&#34;</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(</span><span class="n">123231231231L</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">clone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman</span><span class="p">)</span><span class="n">cloneHuman</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;头发：%s,眼睛：%s,鼻子：%s,嘴巴：%s,生日：%s&#34;</span><span class="p">,</span><span class="n">clone</span><span class="p">.</span><span class="na">getHair</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getEye</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getNodes</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getMouse</span><span class="p">(),</span><span class="n">clone</span><span class="p">.</span><span class="na">getBirth</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;深克隆，引用类型地址比较：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">cloneHuman</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">clone</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CloneHuman</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getHair</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHair</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getEye</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setEye</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getNodes</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNodes</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getMouse</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setMouse</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneHuman</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">,</span><span class="n">Date</span><span class="w"> </span><span class="n">brith</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">brith</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman</span><span class="w"> </span><span class="n">human</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman</span><span class="p">)</span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">human</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Date</span><span class="p">)</span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">human</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="nf">getBirth</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setBirth</span><span class="p">(</span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>序列化反序列化实现深克隆：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DeepClone2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="p">,</span><span class="w"> </span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman2</span><span class="w"> </span><span class="n">cloneHuman1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CloneHuman2</span><span class="p">(</span><span class="s">&#34;黑色&#34;</span><span class="p">,</span><span class="s">&#34;大眼睛&#34;</span><span class="p">,</span><span class="s">&#34;高鼻梁&#34;</span><span class="p">,</span><span class="s">&#34;大嘴巴&#34;</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(</span><span class="n">123231231231L</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用序列化和反序列化实现深克隆</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ByteArrayOutputStream</span><span class="w"> </span><span class="n">bos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ByteArrayOutputStream</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectOutputStream</span><span class="w"> </span><span class="n">oos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectOutputStream</span><span class="p">(</span><span class="n">bos</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">oos</span><span class="p">.</span><span class="na">writeObject</span><span class="p">(</span><span class="n">cloneHuman1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bos</span><span class="p">.</span><span class="na">toByteArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ByteArrayInputStream</span><span class="w"> </span><span class="n">bis</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ByteArrayInputStream</span><span class="p">(</span><span class="n">bytes</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectInputStream</span><span class="w"> </span><span class="n">ois</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectInputStream</span><span class="p">(</span><span class="n">bis</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 克隆好的对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman2</span><span class="w"> </span><span class="n">cloneHuman2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman2</span><span class="p">)</span><span class="w"> </span><span class="n">ois</span><span class="p">.</span><span class="na">readObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;深克隆，引用类型地址比较：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">cloneHuman1</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">cloneHuman2</span><span class="p">.</span><span class="na">getBirth</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CloneHuman2</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="p">,</span><span class="w"> </span><span class="n">Serializable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getHair</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHair</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getEye</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setEye</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getNodes</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNodes</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getMouse</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setMouse</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneHuman2</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hair</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">eye</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nodes</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mouse</span><span class="p">,</span><span class="n">Date</span><span class="w"> </span><span class="n">brith</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hair</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hair</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">eye</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">eye</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">nodes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">nodes</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mouse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mouse</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">brith</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CloneHuman2</span><span class="w"> </span><span class="n">human</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">CloneHuman2</span><span class="p">)</span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">human</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Date</span><span class="p">)</span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">human</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Date</span><span class="w"> </span><span class="nf">getBirth</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setBirth</span><span class="p">(</span><span class="n">Date</span><span class="w"> </span><span class="n">birth</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">birth</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">birth</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="总结">总结</h4>
+<p>原型模式作为一种快速创建大量相同或相似对象的方式，在软件开发中应用较为广泛，很多软件提供的复制和粘贴操作就是原型模式的典型应用。
+通过<code>clone</code>的方式在获取大量对象的时候性能开销基本没有什么影响，而<code>new</code>的方式随着实例的对象越来越多，性能会急剧下降，所以原型模式是一种比较重要的获取实例的方式。</p>
+<p>优点：</p>
+<ul>
+<li>当创建新的对象实例较为复杂时，使用原型模式可以简化对象的创建过程，提高创建对象的效率。</li>
+<li>可以使用深克隆的方式保存对象的状态，使用原型模式将对象复制一份并将其状态保存起来，可辅助实现撤销操作。</li>
+<li>扩展性较好，由于在原型模式中提供了抽象原型类，在客户端可以针对抽象原型类进行编程，而将具体原型类写在配置文件中，增加或减少产品类对原有系统都没有任何影响。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>需要为每一个类配备一个克隆方法，而且该克隆方法位于一个类的内部，当对已有的类进行改造时，需要修改源代码，违背了“开闭原则”。</li>
+<li>在实现深克隆时需要编写较为复杂的代码，而且当对象之间存在多重的嵌套引用时，为了实现深克隆，每一层对象对应的类都必须支持深克隆，实现起来可能会比较麻烦。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>原型模式很少单独出现，一般是和工厂方法模式一起出现，通过<code>clone</code>的方法创建一个对象，然后由工厂方法提供给调用者。</li>
+<li><code>Spring</code>中<code>bean</code>的创建实际就是两种：单例模式和原型模式。</li>
+<li>创建新对象成本较大，新的对象可以通过原型模式对已有对象进行复制来获得。</li>
+<li>系统要保存对象的状态，而对象的状态变化很小，或者对象本身占用内存较少时，可以使用原型模式配合备忘录模式来实现。</li>
+</ul>
+<h3 id="建造者模式">建造者模式</h3>
+<p>建造者模式，将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示。建造者模式是一种对象创建型模式。
+建造者模式是较为复杂的创建型模式，它将客户端与包含多个组成部分的复杂对象的创建过程分离，客户端无须知道复杂对象的内部组成部分与装配方式，只需要知道所需建造者的类型即可。
+它关注如何一步一步创建一个的复杂对象，不同的具体建造者定义了不同的创建过程，且具体建造者相互独立，增加新的建造者非常方便，无须修改已有代码，系统具有较好的扩展性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Director</span><span class="w"> </span><span class="n">director</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Director</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Builder</span><span class="w"> </span><span class="n">commonBuilder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CommonRole</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">director</span><span class="p">.</span><span class="na">construct</span><span class="p">(</span><span class="n">commonBuilder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Role</span><span class="w"> </span><span class="n">commonRole</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">commonBuilder</span><span class="p">.</span><span class="na">getRole</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">commonRole</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Role</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">head</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">body</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">foot</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">sp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">hp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setSp</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">sp</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">sp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getSp</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">sp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHp</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">hp</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">hp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getHp</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">hp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;Role{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;head=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">head</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, body=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">body</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, foot=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">foot</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, sp=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">sp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, hp=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">hp</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;, name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Builder</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderHead</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderBody</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderFoot</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderSp</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderHp</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderName</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Role</span><span class="w"> </span><span class="nf">getRole</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Role</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CommonRole</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Builder</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Role</span><span class="w"> </span><span class="n">role</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Role</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderHead</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;building head .....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderBody</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;building body .....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderFoot</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;building foot .....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderSp</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">role</span><span class="p">.</span><span class="na">setSp</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderHp</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">role</span><span class="p">.</span><span class="na">setHp</span><span class="p">(</span><span class="s">&#34;100&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">builderName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">role</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;lucy&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Role</span><span class="w"> </span><span class="nf">getRole</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">role</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Director</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">construct</span><span class="p">(</span><span class="n">Builder</span><span class="w"> </span><span class="n">builder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderHead</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderBody</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderFoot</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderHp</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderSp</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">builder</span><span class="p">.</span><span class="na">builderName</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>优点：</p>
+<ul>
+<li>客户端不必知道产品内部组成的细节，将产品本身与产品的创建过程解耦，使得相同的创建过程可以创建不同的产品对象。</li>
+<li>建造者模式很容易进行扩展。如果有新的需求，通过实现一个新的建造者类就可以完成，基本上不用修改之前已经测试通过的代码，因此也就不会对原有功能引入风险，符合开放封闭原则。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>若产品内部发生变化，建造者都要修改，成本较大；若内部变化复杂，会有很多的建造类。</li>
+<li>产品必须有共同点，使用范围有限。建造者模式创造出来的产品，其组成部分基本相同。如果产品之间的差异较大，则不适用这个模式。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>需要生成的产品对象有复杂的内部结构，这些产品对象通常包含多个成员属性。</li>
+<li>需要生成的产品对象的属性相互依赖，需要指定其生成顺序。</li>
+<li>对象的创建过程独立于创建该对象的类。在建造者模式中引入了指挥者类，将创建过程封装在指挥者类中，而不在建造者类中。</li>
+<li>隔离复杂对象的创建和使用，并使得相同的创建过程可以创建不同的产品。</li>
+</ul>
+<h3 id="适配器模式">适配器模式</h3>
+<p>适配器模式，将一个接口转换成客户希望的另一个接口(指广义的接口，它可以表示一个方法或者方法的集合)，使接口不兼容的那些类可以一起工作，其别名为包装器。
+适配器模式既可以作为类结构型模式，也可以作为对象结构型模式。</p>
+<p>在适配器模式中，我们通过增加一个新的适配器类来解决接口不兼容的问题，使得原本没有任何关系的类可以协同工作。根据适配器类与适配者类的关系不同，适配器模式可分为对象适配器和类适配器两种，在对象适配器模式中，适配器与适配者之间是关联关系。
+在类适配器模式中，适配器与适配者之间是继承或实现关系。</p>
+<h4 id="对象适配器">对象适配器</h4>
+<p>由于在Java中不支持多重继承，而且有破坏封装之嫌。所以提倡多用组合少用继承，在实际开发中推荐使用对象适配器模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">RedHat</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Linux</span><span class="p">()).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Win10</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Windows</span><span class="p">()).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Adapter</span><span class="w"> </span><span class="n">adapter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Adapter</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Windows</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">RedHat</span><span class="p">(</span><span class="n">adapter</span><span class="p">).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">LinuxSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">WindowsSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Linux</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;linux 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Windows</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;windows 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RedHat</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RedHat</span><span class="p">(</span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">linuxSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">useInputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始使用 redHat 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">linuxSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;结束使用 redHat 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Win10</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Win10</span><span class="p">(</span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">windowsSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">useInputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始使用 win10 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">windowsSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;结束使用 win10 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 在 Linux 系统上使用 windows 输入法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Adapter</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Adapter</span><span class="p">(</span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">windowsSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">windowsSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="类适配器">类适配器</h4>
+<p>类适配器模式和对象适配器模式最大的区别在于适配器和适配者之间的关系不同，对象适配器模式中适配器和适配者之间是关联关系，而类适配器模式中适配器和适配者是继承关系。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">RedHat</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Linux</span><span class="p">()).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">Win10</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Windows</span><span class="p">()).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Adapter</span><span class="w"> </span><span class="n">adapter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Adapter</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">new</span><span class="w"> </span><span class="n">RedHat</span><span class="p">(</span><span class="n">adapter</span><span class="p">).</span><span class="na">useInputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">LinuxSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">WindowsSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Linux</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;linux 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Windows</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;windows 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RedHat</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RedHat</span><span class="p">(</span><span class="n">LinuxSoftware</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">linuxSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">linuxSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">useInputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始使用 redHat 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">linuxSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;结束使用 redHat 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Win10</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Win10</span><span class="p">(</span><span class="n">WindowsSoftware</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">windowsSoftware</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">windowsSoftware</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">useInputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始使用 win10 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">windowsSoftware</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;结束使用 win10 系统输入法 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 在 Linux 系统上使用 windows 输入法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Adapter</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Windows</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">LinuxSoftware</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">inputMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">inputMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="总结-1">总结</h4>
+<p>适配器模式将现有接口转化为客户类所期望的接口，实现了对现有类的复用，它是一种使用频率非常高的设计模式，在软件开发中得以广泛应用，在<code>Spring</code>等开源框架、驱动程序设计（如<code>JDBC</code>中的数据库驱动程序）中也使用了适配器模式。</p>
+<p>优点：</p>
+<ul>
+<li>将目标类和适配者类解耦，通过引入一个适配器类来重用现有的适配者类，无须修改原有结构。</li>
+<li>增加了类的透明性和复用性，同时系统的灵活性和扩展性都非常好，更换适配器或者增加新的适配器都非常方便。可以在不修改原有代码的基础上增加新的适配器类，完全符合开放封闭原则。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>过多地使用适配器，会让系统非常零乱，不易整体进行把握。比如，明明看到调用的是 A 接口，其实内部被适配成了 B 接口的实现，一个系统如果太多出现这种情况，无异于一场灾难。因此如果不是很有必要，可以不使用适配器。</li>
+<li>对象适配器模式的缺点是很难置换适配者类的方法。</li>
+<li>类适配器模式中的目标抽象类只能为接口，不能为类，其使用有一定的局限性。</li>
+</ul>
+<p>使用场景</p>
+<ul>
+<li>系统需要使用现有的类，而这些类的接口不符合系统的需要；想要建立一个可以重复使用的类，用于与一些彼此之间没有太大关联的一些类一起工作。</li>
+<li>系统需要使用现有的类，而此类的接口不符合系统的需要。</li>
+<li>想要建立一个可以重复使用的类，用于与一些彼此之间没有太大关联的一些类，包括一些可能在将来引进的类一起工作，这些源类不一定有一致的接口。</li>
+<li>通过接口转换，将一个类插入另一个类系中。如，老虎和飞禽，现在多了一个飞虎，在不增加实体的需求下，增加一个适配器，在里面包容一个虎对象，实现飞的接口。</li>
+</ul>
+<h3 id="桥接模式">桥接模式</h3>
+<p>桥接模式，将实现与抽象放在两个不同的类层次中，使两个层次可以独立改变。它是一种对象结构型模式，又称为柄体模式或接口模式。
+桥接模式是一种很实用的结构型设计模式，如果软件系统中某个类存在两个独立变化的维度，通过该模式可以将这两个维度分离出来，使两者可以独立扩展，让系统更加符合“单一职责原则”。</p>
+<p>如手机制造，内存是一个公司生产，芯片是另一个公司生产，而品牌又是另一个公司。我们需要什么样子的手机就把相应的芯片、内存组装起来。桥接模式就是把两个不同维度的东西桥接起来。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Phone_A</span><span class="w"> </span><span class="n">phone_a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Phone_A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_a</span><span class="p">.</span><span class="na">setAbstractChip</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Chip_A</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_a</span><span class="p">.</span><span class="na">setAbstractMemory</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Memory_A</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_a</span><span class="p">.</span><span class="na">finished</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Phone_B</span><span class="w"> </span><span class="n">phone_b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Phone_B</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_b</span><span class="p">.</span><span class="na">setAbstractChip</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Chip_B</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_b</span><span class="p">.</span><span class="na">setAbstractMemory</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Memory_A</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">phone_b</span><span class="p">.</span><span class="na">finished</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractMemory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractChip</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">type</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span>  <span class="nc">AbstractPhone</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractMemory</span><span class="w"> </span><span class="n">abstractMemory</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractChip</span><span class="w"> </span><span class="n">abstractChip</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAbstractChip</span><span class="p">(</span><span class="n">AbstractChip</span><span class="w"> </span><span class="n">abstractChip</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">abstractChip</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">abstractChip</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAbstractMemory</span><span class="p">(</span><span class="n">AbstractMemory</span><span class="w"> </span><span class="n">abstractMemory</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">abstractMemory</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">abstractMemory</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finished</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Memory_A</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractMemory</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">size</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;create 6G of memory ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Memory_B</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractMemory</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">size</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;create 8G of memory ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Chip_A</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractChip</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">type</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;snapdragon 888 chip ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Chip_B</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractChip</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">type</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;A14 chip ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Phone_A</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPhone</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finished</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractMemory</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractChip</span><span class="p">.</span><span class="na">type</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;phone_a assembly completed ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Phone_B</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPhone</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finished</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractMemory</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">abstractChip</span><span class="p">.</span><span class="na">type</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;phone_b assembly completed ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>桥接模式是设计Java虚拟机和实现JDBC等驱动程序的核心模式之一，应用较为广泛。
+在软件开发中如果一个类或一个系统有多个变化维度时，都可以尝试使用桥接模式对其进行设计。桥接模式为多维度变化的系统提供了一套完整的解决方案，并且降低了系统的复杂度。</p>
+<p>优点：</p>
+<ul>
+<li>实现了抽象和实现部分的分离，从而极大的提供了系统的灵活性，让抽象部分和实现部分独立开来，这有助于系统进行分层设计，从而产生更好的结构化系统。</li>
+<li>优秀的扩展能力。在两个变化维度中任意扩展一个维度，都不需要修改原有系统，符合开放封闭原则。</li>
+<li>桥接模式替代多层继承方案，可以减少子类的个数，降低系统的管理和维护成本。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>桥接模式的引入会增加系统的理解与设计难度，由于聚合关联关系建立在抽象层，要求开发者针对抽象进行设计与编程。</li>
+<li>桥接模式要求正确识别出系统中两个独立变化的维度(抽象、和实现)，因此其使用范围有一定的局限性，即需要有这样的应用场景，如何正确识别两个独立维度也需要一定的经验积累。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>桥接模式主要解决在有多种可能会变化的情况下，用继承会造成类爆炸问题，扩展起来不灵活。对于两个独立变化的维度，使用桥接模式再适合不过了。</li>
+<li>如果一个系统需要在构件的抽象化角色和具体化角色之间增加更多的灵活性，避免在两个层次之间建立静态的继承联系，通过桥接模式可以使它们在抽象层建立一个关联关系。</li>
+</ul>
+<h3 id="组合模式">组合模式</h3>
+<p>组合模式，组合多个对象形成树形结构以表示具有“整体—部分”关系的层次结构。组合模式对单个对象和组合对象的使用具有一致性，组合模式又可以称为“整体—部分”模式，它是一种对象结构型模式。
+组合模式，是用于把一组相似的对象当作一个单一的对象。组合模式依据树形结构来组合对象，用来表示部分以及整体层次。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Tree</span><span class="w"> </span><span class="n">tree</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Tree</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tree</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">LeftNode</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tree</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">RightNode</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tree</span><span class="p">.</span><span class="na">implmethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">implmethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LeftNode</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception: the method is not supported. &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception: the method is not supported. &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">implmethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;left node method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RightNode</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception: the method is not supported. &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Exception: the method is not supported. &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">implmethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;right node method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Tree</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractTree</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">AbstractTree</span><span class="o">&gt;</span><span class="w"> </span><span class="n">treeList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">treeList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">remove</span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">treeList</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">node</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">implmethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;tree node&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">AbstractTree</span><span class="w"> </span><span class="n">node</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">treeList</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">node</span><span class="p">.</span><span class="na">implmethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>组合模式使用面向对象的思想来实现树形结构的构建与处理，描述了如何将容器对象和叶子对象进行递归组合，实现简单，灵活性好。
+由于在软件开发中存在大量的树形结构，因此组合模式是一种使用频率较高的结构型设计模式。在XML解析、组织结构树处理、文件系统设计等领域，组合模式都得到了广泛应用。</p>
+<p>优点：</p>
+<ul>
+<li>高层模块调用简单。客户端可以一致地使用一个组合结构或其中单个对象，不必关心处理的是单个对象还是整个组合结构。</li>
+<li>在组合模式中节点增加自由，无须对现有类库进行任何修改，符合开闭原则。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>在使用组合模式时，其叶子和树的声明都是实现类，而不是接口，违反了依赖倒置原则。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>部分、整体场景，如树形菜单，文件、文件夹的管理。</li>
+<li>希望用户忽略组合对象与单个对象的不同，用户将统一地使用组合结构中的所有对象。</li>
+</ul>
+<h3 id="装饰模式">装饰模式</h3>
+<p>装饰模式，动态地给一个对象增加一些额外的职责，就增加对象功能来说，装饰模式比生成子类实现更为灵活。装饰模式是一种对象结构型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Drink</span><span class="w"> </span><span class="n">coffee</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ShortBlock</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单价格：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">cost</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单描述：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">getDesc</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">coffee</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Chocolate</span><span class="p">(</span><span class="n">coffee</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单价格：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">cost</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单描述：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">getDesc</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">coffee</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Milk</span><span class="p">(</span><span class="n">coffee</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单价格：&#34;</span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">cost</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;订单描述：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">getDesc</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Drink</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">price</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">.</span><span class="na">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setDesc</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">desc</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">desc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getDesc</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setPrice</span><span class="p">(</span><span class="kt">double</span><span class="w"> </span><span class="n">price</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">price</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">price</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">getPrice</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">price</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">cost</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ShortBlock</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Drink</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ShortBlock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setPrice</span><span class="p">(</span><span class="n">3</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;ShortBlock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">cost</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">getPrice</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LongBlock</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Drink</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">LongBlock</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setPrice</span><span class="p">(</span><span class="n">5</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;LongBlock&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">cost</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">getPrice</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CoffeeShop</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Drink</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Drink</span><span class="w"> </span><span class="n">coffee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="nf">CoffeeShop</span><span class="p">(</span><span class="n">Drink</span><span class="w"> </span><span class="n">coffee</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">coffee</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">coffee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">cost</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">getPrice</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">coffee</span><span class="p">.</span><span class="na">cost</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getDesc</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">desc</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">getPrice</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="s">&#34; &amp;&amp; &#34;</span><span class="o">+</span><span class="w">  </span><span class="n">coffee</span><span class="p">.</span><span class="na">getDesc</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Milk</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">CoffeeShop</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Milk</span><span class="p">(</span><span class="n">Drink</span><span class="w"> </span><span class="n">seasoning</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">seasoning</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;Milk&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setPrice</span><span class="p">(</span><span class="n">6</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Chocolate</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">CoffeeShop</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Chocolate</span><span class="p">(</span><span class="n">Drink</span><span class="w"> </span><span class="n">seasoning</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">seasoning</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;Chocolate&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setPrice</span><span class="p">(</span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>装饰模式降低了系统的耦合度，可以动态增加或删除对象的职责，并使得需要装饰的具体构件类和具体装饰类可以独立变化，以便增加新的具体构件类和具体装饰类。
+在软件开发中，装饰模式应用较为广泛，例如在<code>JavaIO</code>中的输入流和输出流的设计、<code>javax.swing</code>包中一些图形界面构件功能的增强等地方都运用了装饰模式。</p>
+<p>一般的，我们为了扩展一个类经常使用继承方式实现，由于继承为类引入静态特征，并且随着扩展功能的增多，子类会很膨胀，装饰者模式主要解决这个问题。</p>
+<p>优点：</p>
+<ul>
+<li>对于扩展一个对象的功能，装饰模式比继承更加灵活性，不会导致类的个数急剧增加。</li>
+<li>装饰类和被装饰类可以独立发展，不会相互耦合，装饰模式是继承的一个替代模式，装饰模式可以动态扩展一个实现类的功能。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>多层装饰比较复杂。</li>
+<li>使用装饰模式进行系统设计时将产生很多小对象，这些对象的区别在于它们之间相互连接的方式有所不同，而不是它们的类或者属性值有所不同，大量小对象的产生势必会占用更多的系统资源，在一定程序上影响程序的性能。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>这种模式创建了一个装饰类，用来包装原有的类，并在保持类方法签名完整性的前提下，提供了额外的功能，可代替继承。</li>
+<li>扩展一个类的功能。</li>
+<li>动态增加功能，动态撤销功能。</li>
+<li>当不能采用继承的方式对系统进行扩展或者采用继承不利于系统扩展和维护时可以使用装饰模式。不能采用继承的情况主要有两类：
+<ul>
+<li>第一类是系统中存在大量独立的扩展，为支持每一种扩展或者扩展之间的组合将产生大量的子类，使得子类数目呈爆炸性增长；</li>
+<li>第二类是因为类已定义为不能被继承；</li>
+</ul>
+</li>
+</ul>
+<h3 id="外观模式">外观模式</h3>
+<p>外观模式，为子系统中的一组接口提供一个统一的入口。外观模式定义了一个高层接口，这个接口使得这一子系统更加容易使用。
+外观模式又称为门面模式，它是一种对象结构型模式。外观模式是迪米特法则的一种具体实现，通过引入一个新的外观角色可以降低原有系统的复杂度，同时降低客户类与子系统的耦合度。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Facade</span><span class="w"> </span><span class="n">facade</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Facade</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">facade</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Facade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="n">c</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">D</span><span class="w"> </span><span class="n">d</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Facade</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="p">.</span><span class="na">getInstance</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">B</span><span class="p">.</span><span class="na">getInstance</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">C</span><span class="p">.</span><span class="na">getInstance</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">d</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">D</span><span class="p">.</span><span class="na">getInstance</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">a</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">b</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">c</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">d</span><span class="p">.</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * A调用B类，A调用C类，B调用C类，D调用B类，D调用C类
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">A</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">private</span><span class="w"> </span><span class="nf">A</span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="n">B</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="n">C</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;A class test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">B</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">B</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">B</span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">C</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;B class test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">C</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">C</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">C</span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kd">static</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;C class test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">D</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">D</span><span class="w"> </span><span class="n">instance</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">D</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="nf">D</span><span class="p">(){}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">D</span><span class="w"> </span><span class="nf">getInstance</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">instance</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="nf">aTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">B</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">C</span><span class="p">.</span><span class="na">getInstance</span><span class="p">().</span><span class="na">aTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;D class test method ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>外观模式的主要目的在于降低系统的复杂程度，在面向对象软件系统中，类与类之间的关系越多，不能表示系统设计得越好，反而表示系统中类之间的耦合度太大，这样的系统在维护和修改时都缺乏灵活性，因为一个类的改动会导致多个类发生变化，而外观模式的引入在很大程度上降低了类与类之间的耦合关系。
+引入外观模式之后，增加新的子系统或者移除子系统都非常方便，客户类无须进行修改（或者极少的修改），只需要在外观类中增加或移除对子系统的引用即可。
+从这一点来说，外观模式在一定程度上并不符合开放封闭原则，增加新的子系统需要对原有系统进行一定的修改，虽然这个修改工作量不大。</p>
+<p>优点：</p>
+<ul>
+<li>减少关联关系；对客户端屏蔽了具体的实现，使得子系统使用起来更加容易；客户端代码将变得很简单，与之关联的对象也很少。</li>
+<li>解耦合；具体实现有改变不会影响到调用的客户端，只需要调整外观类即可。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>如果设计不当，扩展时增加新的实现可能需要修改外观类的源代码，违背了开放封闭原则.</li>
+<li>不能很好地限制客户端直接使用子系统类，如果对客户端访问子系统类做太多的限制则减少了可变性和灵活性。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>当要为访问一系列复杂的子系统提供一个简单入口时可以使用外观模式。</li>
+<li>客户端程序与多个子系统之间存在很大的依赖性。引入外观类可以将子系统与客户端解耦，从而提高子系统的独立性和可移植性。</li>
+<li>在层次化结构中，可以使用外观模式定义系统中每一层的入口，层与层之间不直接产生联系，而通过外观类建立联系，降低层之间的耦合度。</li>
+</ul>
+<h3 id="享元模式">享元模式</h3>
+<p>享元模式，运用共享技术有效地支持大量细粒度对象的复用。系统只使用少量的对象，而这些对象都很相似，状态变化很小，可以实现对象的多次复用。
+由于享元模式要求能够共享的对象必须是细粒度对象，因此它又称为轻量级模式，它是一种对象结构型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WebSiteFactory</span><span class="w"> </span><span class="n">webSiteFactory</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WebSiteFactory</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;新闻&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;lucy&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;新闻&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;jane&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;博客&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;jack&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;博客&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;maik&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">getWebSite</span><span class="p">(</span><span class="s">&#34;博客&#34;</span><span class="p">).</span><span class="na">use</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">User</span><span class="p">(</span><span class="s">&#34;seven&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;网站类型共：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">webSiteFactory</span><span class="p">.</span><span class="na">countWebSiteType</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WebSite</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">use</span><span class="p">(</span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ConcreateWebSite</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WebSite</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ConcreateWebSite</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">use</span><span class="p">(</span><span class="n">User</span><span class="w"> </span><span class="n">user</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;网站类型名称：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="s">&#34;\t 网站用户：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">user</span><span class="p">.</span><span class="na">getUsername</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">User</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">User</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">username</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setUsername</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">username</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getUsername</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">username</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">WebSiteFactory</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">WebSite</span><span class="o">&gt;</span><span class="w"> </span><span class="n">pool</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WebSite</span><span class="w"> </span><span class="nf">getWebSite</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">webSiteName</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">pool</span><span class="p">.</span><span class="na">containsKey</span><span class="p">(</span><span class="n">webSiteName</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">pool</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">webSiteName</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcreateWebSite</span><span class="p">(</span><span class="n">webSiteName</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">pool</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">webSiteName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="nf">countWebSiteType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">pool</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>当系统中存在大量相同或者相似的对象时，享元模式是一种较好的解决方案，它通过共享技术实现相同或相似的细粒度对象的复用，从而节约了内存空间，提高了系统性能。
+相比其他结构型设计模式，享元模式的使用频率并不算太高，但是作为一种以“节约内存，提高性能”为出发点的设计模式，它在软件开发中还是得到了一定程度的应用。如：<code>String</code>、Java的池技术等。</p>
+<p>享元模式主要解决在有大量对象时，有可能会造成内存溢出，我们把其中共同的部分抽象出来，如果有相同的业务请求，直接返回在内存中已有的对象，避免重新创建。</p>
+<p>优点：</p>
+<ul>
+<li>大大减少对象的创建，降低系统的内存，使效率提高。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>提高了系统的复杂度，需要分离出外部状态和内部状态，而且外部状态具有固有化的性质，不应该随着内部状态的变化而变化，否则会造成系统的混乱。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>在使用享元模式时需要维护一个存储享元对象的享元池，而这需要耗费一定的系统资源，因此，应当在需要多次重复使用享元对象时才值得使用享元模式。</li>
+<li>系统有大量相似对象。</li>
+<li>需要缓冲池的场景。</li>
+</ul>
+<h3 id="代理模式">代理模式</h3>
+<p>代理模式，给某一个对象提供一个代理或占位符，并由代理对象来控制对原对象的访问。
+代理模式是为一个对象提供一个替身，以控制对这个对象的访问，即通过代理对象访问目标对象。
+这样做的好处是，可以在目标对象实现的基础上，增强额外的功能操作，即扩展目标对象的功能。被代理的对象可以是远程对象、创建开销大的对象或需要安全控制的对象。
+代理模式有不同的形式，主要有三种 静态代理、动态代理 (<code>JDK</code>代理、<code>Cglib</code>代理)。</p>
+<h4 id="静态代理">静态代理</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ProxyImpl</span><span class="w"> </span><span class="n">proxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ProxyImpl</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StaticProxy</span><span class="w"> </span><span class="n">staticProxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StaticProxy</span><span class="p">(</span><span class="n">proxy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">staticProxy</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">ProxyInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ProxyImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ProxyInterface</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;helloWorld&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">StaticProxy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ProxyInterface</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ProxyImpl</span><span class="w"> </span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">StaticProxy</span><span class="w"> </span><span class="p">(</span><span class="n">ProxyImpl</span><span class="w"> </span><span class="n">target</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">target</span><span class="o">=</span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;静态代理之前...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">target</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;静态代理之后...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>静态代理能在不修改目标对象的功能前提下，能通过代理对象对目标进行扩展。
+但是因为代理对象需要与目标对象实现相同的接口，所以会有很多代理类一旦接口增加方法后，目标对象与代理对象都需要维护。</p>
+<h4 id="jdk动态代理">JDK动态代理</h4>
+<p>JDK动态代理，代理对象不需要实现接口，但是目标对象需要实现接口，否则不能实现动态代理。代理对象的生产是利用JDK的API，动态的在内存中构建代理对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ProxyImpl</span><span class="w"> </span><span class="n">proxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ProxyImpl</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ProxyInterface</span><span class="w"> </span><span class="n">jdkProxyInterface</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">ProxyInterface</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">JDKProxy</span><span class="p">().</span><span class="na">bind</span><span class="p">(</span><span class="n">proxy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">jdkProxyInterface</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">ProxyInterface</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ProxyImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ProxyInterface</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;helloWorld&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">JDKProxy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//通用类型，表示被代理的真实对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">bind</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">target</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">target</span><span class="o">=</span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//生成代理类（与被代理对象实现相同接口的兄弟类）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">Proxy</span><span class="p">.</span><span class="na">newProxyInstance</span><span class="p">(</span><span class="n">target</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getClassLoader</span><span class="p">(),</span><span class="w"> </span><span class="n">target</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getInterfaces</span><span class="p">(),</span><span class="w"> </span><span class="p">(</span><span class="n">proxy</span><span class="p">,</span><span class="w"> </span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Object</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;JDK动态代理前&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">res</span><span class="o">=</span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">target</span><span class="p">,</span><span class="w"> </span><span class="n">args</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;JDK动态代理后&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="cglib动态代理">Cglib动态代理</h4>
+<p><code>Cglib</code>代理也叫作子类代理，它是在内存中构建一个子类对象从而实现对目标对象功能扩展。
+<code>Cglib</code>是一个强大的高性能的代码生成包，它可以在运行期扩展Java类与实现Java接口，广泛的被许多AOP的框架使用，例如<code>Spring AOP</code>，实现方法拦截。</p>
+<p>以下测试代码需要导入<code>Cglib</code>和<code>asm</code>相关jar包：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">asm-3.3.1.jar
+</span></span><span class="line"><span class="cl">cglib-2.2.jar
+</span></span></code></pre></div><p>使用<code>Cglib</code>实现动态代理时出现了下面这个异常：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Exception in thread &#34;main&#34; java.lang.IncompatibleClassChangeError: 
+</span></span><span class="line"><span class="cl">class net.sf.cglib.core.DebuggingClassWriter has interface org.objectweb.asm.ClassVisitor as super class
+</span></span></code></pre></div><p>原因是<code>cglib.jar</code>包含<code>asm.jar</code>包。报错内容是<code>ClassVisitor</code>的父类不相容。<a href="https://my.oschina.net/itblog/blog/528613">详细原因分析</a>。
+测试时用<code>cglib2.2.jar</code>和<code>asm3.3.1.jar</code>版本，解决jar包冲突问题。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Target</span><span class="w"> </span><span class="n">target</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Target</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Target</span><span class="w"> </span><span class="n">bind</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Target</span><span class="p">)</span><span class="k">new</span><span class="w"> </span><span class="n">CGLibProxy</span><span class="p">().</span><span class="na">bind</span><span class="p">(</span><span class="n">target</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bind</span><span class="p">.</span><span class="na">test</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Target</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;helloWorld&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CGLibProxy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">MethodInterceptor</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="n">Object</span><span class="w"> </span><span class="nf">bind</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">target</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">target</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">target</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Enhancer</span><span class="w"> </span><span class="n">enhancer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Enhancer</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">enhancer</span><span class="p">.</span><span class="na">setSuperclass</span><span class="p">(</span><span class="n">target</span><span class="p">.</span><span class="na">getClass</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">enhancer</span><span class="p">.</span><span class="na">setCallback</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">enhancer</span><span class="p">.</span><span class="na">create</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">intercept</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">proxy</span><span class="p">,</span><span class="w"> </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">,</span><span class="w"> </span><span class="n">MethodProxy</span><span class="w"> </span><span class="n">methodProxy</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Object</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;CGLib动态代理前&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">res</span><span class="o">=</span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">target</span><span class="p">,</span><span class="w"> </span><span class="n">args</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;CGLib动态代理后&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">res</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="总结-2">总结</h4>
+<p>代理模式是常用的结构型设计模式之一，它为对象的间接访问提供了一个解决方案，可以对对象的访问进行控制。
+代理模式主要解决，在直接访问对象时带来的问题。比如说，要访问的对象在远程的机器上。在面向对象系统中，有些对象由于某些原因，对象创建开销很大，或者某些操作需要安全控制，或者需要进程外的访问，直接访问会给使用者或者系统结构带来很多麻烦，我们可以在访问此对象时加上一个对此对象的访问层。</p>
+<p>优点：</p>
+<ul>
+<li>职责清晰。能够协调调用者和被调用者，在一定程度上降低了系统的耦合度。</li>
+<li>高扩展性。增加和更换代理类无须修改源代码，符合开闭原则，系统具有较好的灵活性和可扩展性。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>由于在客户端和真实主题之间增加了代理对象，因此有些类型的代理模式可能会造成请求的处理速度变慢。</li>
+<li>实现代理模式需要额外的工作，有些代理模式的实现非常复杂。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>想在访问一个类时做一些控制。</li>
+</ul>
+<h3 id="职责链模式">职责链模式</h3>
+<p>职责链模式，避免请求发送者与接收者耦合在一起，让多个对象都有可能接收请求，将这些对象连接成一条链，并且沿着这条链传递请求，直到有对象处理它为止。职责链模式是一种对象行为型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="c1">// 产品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">test</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RequestEntity</span><span class="p">(</span><span class="s">&#34;test&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">2000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 指定职责链</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BeforeHandler</span><span class="w"> </span><span class="n">before</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BeforeHandler</span><span class="p">(</span><span class="s">&#34;before&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AfterHandler</span><span class="w"> </span><span class="n">after</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AfterHandler</span><span class="p">(</span><span class="s">&#34;after&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PostHandler</span><span class="w"> </span><span class="n">post</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PostHandler</span><span class="p">(</span><span class="s">&#34;post&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 形成链状闭环 要确保会被责任链中的组件处理 否则会一直循环下去 ，当然也可以选择不闭环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">before</span><span class="p">.</span><span class="na">setHandler</span><span class="p">(</span><span class="n">after</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">after</span><span class="p">.</span><span class="na">setHandler</span><span class="p">(</span><span class="n">post</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">post</span><span class="p">.</span><span class="na">setHandler</span><span class="p">(</span><span class="n">before</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">after</span><span class="p">.</span><span class="na">handleRequest</span><span class="p">(</span><span class="n">test</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RequestEntity</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">grade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RequestEntity</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">,</span><span class="n">Integer</span><span class="w"> </span><span class="n">grade</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">grade</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">grade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="nf">getGrade</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">grade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Handler</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 下一个引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Handler</span><span class="w"> </span><span class="n">handler</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Handler</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setHandler</span><span class="p">(</span><span class="n">Handler</span><span class="w"> </span><span class="n">handler</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">handler</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">handler</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRequest</span><span class="p">(</span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BeforeHandler</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Handler</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">BeforeHandler</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRequest</span><span class="p">(</span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1000</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;分数为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;，被&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;处理 &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">handler</span><span class="p">.</span><span class="na">handleRequest</span><span class="p">(</span><span class="n">requestEntity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">AfterHandler</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Handler</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">AfterHandler</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRequest</span><span class="p">(</span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">2000</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;分数为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;，被&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;处理 &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">handler</span><span class="p">.</span><span class="na">handleRequest</span><span class="p">(</span><span class="n">requestEntity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">PostHandler</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Handler</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">PostHandler</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handleRequest</span><span class="p">(</span><span class="n">RequestEntity</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">3000</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;分数为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">requestEntity</span><span class="p">.</span><span class="na">getGrade</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;，被&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;处理 &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">handler</span><span class="p">.</span><span class="na">handleRequest</span><span class="p">(</span><span class="n">requestEntity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>职责链模式通过建立一条链来组织请求的处理者，请求将沿着链进行传递，请求发送者无须知道请求在何时、何处以及如何被处理，实现了请求发送者与处理者的解耦。
+在软件开发中，如果遇到有多个对象可以处理同一请求时可以应用职责链模式，例如在Web应用开发中创建一个过滤器(Filter)链来对请求数据进行过滤，在工作流系统中实现公文的分级审批等等，使用职责链模式可以较好地解决此类问题。</p>
+<p>优点：</p>
+<ul>
+<li>增加新的请求处理类很方便，只需要在客户端重新建链即可，从这一点来看是符合开闭原则的。</li>
+<li>为请求创建了一个接收者对象的链式结构。对请求的发送者和接收者进行解耦。</li>
+<li>简化了对象，使得对象不需要知道链的结构。</li>
+<li>增强给对象指派职责的灵活性。通过改变链内的成员或者调动它们的次序，允许动态地新增或者删除责任。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>系统性能将受到一定影响，可能会造成循环调用。特别是在链比较长的时候，因此需控制链中最大节点数量，一般通过在<code>Handler</code>中设置一个最大节点数量，在<code>setNext</code>方法中判断是否已经超过阀值，超过则不允许该链建立，避免出现超长链无意识地破坏系统性能。</li>
+<li>调试不方便。采用了类似递归的方式，调试时逻辑可能比较复杂。可能不容易观察运行时的特征，有碍于除错。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>在处理消息的时候以过滤很多通道。</li>
+<li>有多个对象可以处理同一个请求，具体哪个对象处理该请求由运行时刻自动确定。</li>
+<li>在不明确指定接收者的情况下，向多个对象中的一个提交一个请求。</li>
+<li>可动态指定一组对象处理请求。</li>
+</ul>
+<h3 id="命令模式">命令模式</h3>
+<p>命令模式，将一个请求封装为一个对象，从而让我们可用不同的请求对客户进行参数化；对请求排队或者记录请求日志，以及支持可撤销的操作。
+命令模式是一种对象行为型模式，其别名为动作模式或事务模式。
+命令模式可以将请求发送者和接收者完全解耦，发送者与接收者之间没有直接引用关系，发送请求的对象只需要知道如何发送请求，而不必知道如何完成请求。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LightReceiver</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LightOnCommand</span><span class="w"> </span><span class="n">lightOnCommand</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LightOnCommand</span><span class="p">(</span><span class="n">lightReceiver</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LightOffCommand</span><span class="w"> </span><span class="n">lightOffCommand</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LightOffCommand</span><span class="p">(</span><span class="n">lightReceiver</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RemoteCommand</span><span class="w"> </span><span class="n">remoteCommand</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RemoteCommand</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 测试</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">remoteCommand</span><span class="p">.</span><span class="na">setCommand</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="n">lightOnCommand</span><span class="p">,</span><span class="n">lightOffCommand</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 按下开灯按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;按下开灯按钮 -------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">remoteCommand</span><span class="p">.</span><span class="na">onButtonPushed</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 按下关灯按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;按下关灯按钮 -------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">remoteCommand</span><span class="p">.</span><span class="na">offButtonPushed</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 按下撤销按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;按下撤销按钮 ---------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">remoteCommand</span><span class="p">.</span><span class="na">undoButtonPushed</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Command</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行命令
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 撤销命令
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">undo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LightReceiver</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">on</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开灯 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">off</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;关灯 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LightOnCommand</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Command</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">LightOnCommand</span><span class="p">(</span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lightReceiver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lightReceiver</span><span class="p">.</span><span class="na">on</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">undo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lightReceiver</span><span class="p">.</span><span class="na">off</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">LightOffCommand</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">LightOffCommand</span><span class="p">(</span><span class="n">LightReceiver</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">lightReceiver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lightReceiver</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lightReceiver</span><span class="p">.</span><span class="na">off</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">undo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">lightReceiver</span><span class="p">.</span><span class="na">on</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 空执行 默认命令实现类
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">NoCommand</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">exec</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;默认命令执行&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">undo</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;默认撤销方法&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RemoteCommand</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 存放开关命令</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">onCommands</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">offCommands</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 存放撤销命令</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">undoCommands</span><span class="o">[]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RemoteCommand</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">undoCommands</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Command</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">onCommands</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Command</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">offCommands</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Command</span><span class="o">[</span><span class="n">5</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 默认空命令</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">onCommands</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NoCommand</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">offCommands</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NoCommand</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 设置命令</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="kt">void</span><span class="w">  </span><span class="nf">setCommand</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">no</span><span class="p">,</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">onCommand</span><span class="p">,</span><span class="w"> </span><span class="n">Command</span><span class="w"> </span><span class="n">offCommand</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">onCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">onCommand</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">offCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">offCommand</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 按下开的按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">onButtonPushed</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">no</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">onCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">.</span><span class="na">exec</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 记录撤销操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">undoCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">onCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 按下关闭的按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">offButtonPushed</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">no</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">offCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">.</span><span class="na">exec</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 记录撤销操作</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">undoCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">offCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 按下撤销按钮</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">undoButtonPushed</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">no</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">undoCommands</span><span class="o">[</span><span class="n">no</span><span class="o">]</span><span class="p">.</span><span class="na">undo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>命令模式是一种使用频率非常高的设计模式，它可以将请求发送者与接收者解耦，请求发送者通过命令对象来间接引用请求接收者，使得系统具有更好的灵活性和可扩展性。
+在基于GUI的软件开发，无论是在电脑桌面应用还是在移动应用中，命令模式都得到了广泛的应用。
+在软件系统中，行为请求者与行为实现者通常是一种紧耦合的关系，但某些场合，比如需要对行为进行记录、撤销或重做、事务等处理时，这种无法抵御变化的紧耦合的设计就不太合适。</p>
+<p>优点：</p>
+<ul>
+<li>降低了系统耦合度。</li>
+<li>新的命令可以很容易地加入到系统中。由于增加新的具体命令类不会影响到其他类，因此增加新的具体命令类很容易，无须修改原有系统源代码，甚至客户类代码，满足开闭原则的要求。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>使用命令模式可能会导致某些系统有过多的具体命令类。因为针对每一个对请求接收者的调用操作都需要设计一个具体命令类，因此在某些系统中可能需要提供大量的具体命令类，这将影响命令模式的使用。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>请求调用者需要与请求接收者解耦时，命令模式可以使调用者和接收者不直接交互。</li>
+<li>当系统需要支持命令的撤销操作和恢复操作时。</li>
+<li>系统需要在不同的时间指定请求、将请求排队和执行请求。一个命令对象和请求的初始调用者可以有不同的生命期，换言之，最初的请求发出者可能已经不在了，而命令对象本身仍然是活动的，可以通过该命令对象去调用请求接收者，而无须关心请求调用者的存在性，可以通过请求日志文件等机制来具体实现。</li>
+</ul>
+<h3 id="解释器模式">解释器模式</h3>
+<p>解释器模式，定义一个语言的文法，并且建立一个解释器来解释该语言中的句子，这里的“语言”是指使用规定格式和语法的代码。解释器模式是一种类行为型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">expStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getExpStr</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">getValue</span><span class="p">(</span><span class="n">expStr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Calculator</span><span class="w"> </span><span class="n">calculator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Calculator</span><span class="p">(</span><span class="n">expStr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;运算结果：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">expStr</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;=&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">calculator</span><span class="p">.</span><span class="na">run</span><span class="p">(</span><span class="n">var</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获得表达式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getExpStr</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;请输入表达式：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">InputStreamReader</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">in</span><span class="p">))).</span><span class="na">readLine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 获得值映射</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getValue</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">expStr</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">expStr</span><span class="p">.</span><span class="na">toCharArray</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ch</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">ch</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">map</span><span class="p">.</span><span class="na">containsKey</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">ch</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;请输入&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">ch</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;的值：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">String</span><span class="w"> </span><span class="n">in</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BufferedReader</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">InputStreamReader</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">in</span><span class="p">))).</span><span class="na">readLine</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">map</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">ch</span><span class="p">),</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">in</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">map</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 表达式解释器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 终结表达式
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">VarExpression</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">VarExpression</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">key</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">map</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">map</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">key</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 非终结表达式
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SymbolExpression</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SymbolExpression</span><span class="p">(</span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">left</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 因为 SymbolExpression  是让其子类来实现，因此 interpreter 是一个默认实现</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 减法
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">SubExpression</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SymbolExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">SubExpression</span><span class="p">(</span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 加法
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">AddExpression</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SymbolExpression</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">AddExpression</span><span class="p">(</span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">interpreter</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">left</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">right</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 计算器 调用加减法
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Calculator</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">expression</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="nf">Calculator</span><span class="p">(</span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">expression</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">expression</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">expression</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Calculator</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">expStr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 安排运算先后顺序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Stack</span><span class="o">&lt;</span><span class="n">AbstractExpression</span><span class="o">&gt;</span><span class="w"> </span><span class="n">stack</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Stack</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 表达式拆分成字符数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">char</span><span class="o">[]</span><span class="w"> </span><span class="n">charArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">expStr</span><span class="p">.</span><span class="na">toCharArray</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AbstractExpression</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//遍历我们的字符数组，  即遍历	[a, +, b]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//针对不同的情况，做处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">charArray</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">charArray</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;+&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 从 stack 取 出 left =&gt; &#34;a&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 取出右表达式 &#34;b&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">VarExpression</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">charArray</span><span class="o">[++</span><span class="n">i</span><span class="o">]</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">AddExpression</span><span class="p">(</span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">// 然后根据得到 left 和 right 构建 AddExpresson 加入 stack</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">case</span><span class="w"> </span><span class="sc">&#39;-&#39;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">left</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">right</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">VarExpression</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">charArray</span><span class="o">[++</span><span class="n">i</span><span class="o">]</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">SubExpression</span><span class="p">(</span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">right</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">default</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="c1">//如果是一个 Var 就创建要给 VarExpression 对象，并 push 到 stack</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">stack</span><span class="p">.</span><span class="na">push</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">VarExpression</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">charArray</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//当遍历完整个 charArray  数组后，stack 就得到最后</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">expression</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stack</span><span class="p">.</span><span class="na">pop</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">run</span><span class="p">(</span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">var</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//最后将表达式 a+b 和 var = {a=10,b=20}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//然后传递给 expression 的 interpreter 进行解释执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">expression</span><span class="p">.</span><span class="na">interpreter</span><span class="p">(</span><span class="n">var</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>解释器模式为自定义语言的设计和实现提供了一种解决方案，它用于定义一组文法规则并通过这组文法规则来解释语言中的句子。
+虽然解释器模式的使用频率不是特别高，但是它在正则表达式、XML文档解释等领域还是得到了广泛使用。
+与解释器模式类似，目前还诞生了很多基于抽象语法树的源代码处理工具，例如<code>Eclipse</code>中的<code>Eclipse AST</code>，它可以用于表示Java语言的语法结构，用户可以通过扩展其功能，创建自己的文法规则。</p>
+<p>优点：</p>
+<ul>
+<li>易于改变和扩展文法。增加新的解释表达式较为方便。如果用户需要增加新的解释表达式只需要对应增加一个新的终结符表达式或非终结符表达式类，原有表达式类代码无须修改，符合“开闭原则”。</li>
+<li>易于实现简单文法。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>可利用场景比较少。</li>
+<li>对于复杂的文法比较难维护。解释器模式会引起类膨胀，如果一个语言包含太多文法规则，类的个数将会急剧增加，导致系统难以管理和维护。</li>
+<li>解释器模式采用递归调用方法。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>对于一些固定文法构建一个解释句子的解释器。</li>
+<li>可以将一个需要解释执行的语言中的句子表示为一个抽象语法树</li>
+<li>一些重复出现的问题可以用一种简单的语言来进行表达。</li>
+<li>一个简单语法需要解释的场景。</li>
+</ul>
+<h3 id="迭代器模式">迭代器模式</h3>
+<p>迭代器模式，提供一种方法来访问聚合对象，而不用暴露这个对象的内部表示，其别名为游标。迭代器模式是一种对象行为型模式。
+迭代器模式的重要用途就是帮助我们遍历容器。迭代器模式，提供一种遍历集合元素的统一接口，用一致的方法遍历集合元素，不需要知道集合对象的底层表示，即不暴露其内部的结构。
+在迭代器模式结构中包含聚合和迭代器两个层次结构，考虑到系统的灵活性和可扩展性，在迭代器模式中应用了工厂方法模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Bread</span><span class="w"> </span><span class="n">bread</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Bread</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bread</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;面粉&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bread</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;黄油&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bread</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;白糖&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bread</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">&#34;鸡蛋&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Iterator</span><span class="w"> </span><span class="n">iterator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bread</span><span class="p">.</span><span class="na">getIterator</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">iterator</span><span class="p">.</span><span class="na">hasNext</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">iterator</span><span class="p">.</span><span class="na">next</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">FoodIterator</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Iterator</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">foods</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w">      </span><span class="n">position</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">FoodIterator</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">foods</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">foods</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">foods</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">hasNext</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">position</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">foods</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">next</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">food</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">foods</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">position</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">food</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Food</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Iterator</span><span class="w"> </span><span class="nf">getIterator</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Bread</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Food</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">foods</span><span class="w">    </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[</span><span class="n">4</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w">      </span><span class="n">position</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">foods</span><span class="o">[</span><span class="n">position</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">position</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Iterator</span><span class="w"> </span><span class="nf">getIterator</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FoodIterator</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">foods</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>迭代器模式是一种使用频率非常高的设计模式，通过引入迭代器可以将数据的遍历功能从聚合对象中分离出来，聚合对象只负责存储数据，而遍历数据由迭代器来完成。
+由于很多编程语言的类库都已经实现了迭代器模式，因此在实际开发中，我们只需要直接使用Java、C#等语言已定义好的迭代器即可，迭代器已经成为我们操作聚合对象的基本工具之一。
+迭代器的使用现在非常广泛，因为Java中提供了<code>java.util.Iterator</code>。而且Java中的很多容器，如<code>Collection</code>、<code>Set</code>也都提供了对迭代器的支持。</p>
+<p>优点：</p>
+<ul>
+<li>提供一个统一的方法遍历对象，客户不用再考虑聚合的类型，使用一种方法就可以遍历对象了。</li>
+<li>隐藏了聚合的内部结构，客户端要遍历聚合的时候只能取到迭代器，而不会知道聚合的具体组成。</li>
+<li>提供了一种设计思想，就是一个类应该只有一个引起变化的原因。
+在聚合类中，我们把迭代器分开，就是要把管理对象集合和遍历对象集合的责任分开，这样一来集合改变的话，只影响到聚合对象。而如果遍历方式改变的话，只影响到了迭代器。</li>
+<li>当要展示一组相似对象，或者遍历一组相同对象时使用，适合使用迭代器模式</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>由于迭代器模式将存储数据和遍历数据的职责分离，增加新的聚合类需要对应增加新的迭代器类，类的个数成对增加，这在一定程度上增加了系统的复杂性。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>需要为一个聚合对象提供多种遍历方式。</li>
+<li>使用迭代器模式可以为遍历不同的聚合结构提供一个统一的接口，接口的实现类中为不同的聚合结构提供不同的遍历方式，而客户端可以一致性地操作该接口。</li>
+</ul>
+<h3 id="中介者模式">中介者模式</h3>
+<p>中介者模式，用一个中介对象（中介者）来封装一系列的对象交互，中介者使各对象不需要显式地相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互。
+中介者模式又称为调停者模式，它是一种对象行为型模式。
+如果在一个系统中对象之间存在多对多的相互关系，我们可以将对象之间的一些交互行为从各个对象中分离出来，并集中封装在一个中介者对象中，并由该中介者进行统一协调，这样对象之间多对多的复杂关系就转化为相对简单的一对多关系。
+通过引入中介者来简化对象之间的复杂交互，中介者模式是“迪米特法则”的一个典型应用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//创建一个中介者对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ConcreteMediator</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//创建 Alarm  并且加入到ConcreteMediator 对象的 HashMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Alarm</span><span class="w"> </span><span class="n">alarm</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Alarm</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;alarm&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//创建了 CoffeeMachine 对象，并且加入到	ConcreteMediator 对象的 HashMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CoffeeMachine</span><span class="w"> </span><span class="n">coffeeMachine</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CoffeeMachine</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;coffeeMachine&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//创建  tV , 并	且加入到	ConcreteMediator 对象的 HashMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">TV</span><span class="w"> </span><span class="n">tV</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TV</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;TV&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//让闹钟发出消息 依次调用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alarm</span><span class="p">.</span><span class="na">sendAlarm</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">coffeeMachine</span><span class="p">.</span><span class="na">finishCoffee</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alarm</span><span class="p">.</span><span class="na">sendAlarm</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">tV</span><span class="p">.</span><span class="na">startTv</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 中介者
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Mediator</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">register</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">,</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="n">colleague</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ConcreteMediator</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Mediator</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 集合，放入所有的同事对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Colleague</span><span class="o">&gt;</span><span class="w"> </span><span class="n">colleagueMap</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">interMap</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">ConcreteMediator</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">colleagueMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">interMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">register</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">,</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="n">colleague</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">colleague</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Alarm</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">interMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;Alarm&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">colleague</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">CoffeeMachine</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">interMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">&#34;CoffeeMachine&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;........&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">colleagueName</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">colleagueName</span><span class="p">)</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Alarm</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">stateChange</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">((</span><span class="n">CoffeeMachine</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">interMap</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="s">&#34;CoffeeMachine&#34;</span><span class="p">)))).</span><span class="na">startCoffee</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">((</span><span class="n">TV</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">interMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="s">&#34;TV&#34;</span><span class="p">)))).</span><span class="na">startTv</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">stateChange</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">((</span><span class="n">TV</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">interMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="s">&#34;TV&#34;</span><span class="p">)))).</span><span class="na">stopTv</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">colleagueMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">colleagueName</span><span class="p">)</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">TV</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//如果 TV 发现消息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 抽象同事类
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Colleague</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Colleague</span><span class="p">(</span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">mediator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mediator</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Mediator</span><span class="w"> </span><span class="nf">getMediator</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">mediator</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Alarm</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Alarm</span><span class="p">(</span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">//在创建 Alarm 同事对象时，将自己放入到 ConcreteMediator 对象中[集合]</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mediator</span><span class="p">.</span><span class="na">register</span><span class="p">(</span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendAlarm</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">sendMessage</span><span class="p">(</span><span class="n">stateChange</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 调用的中介者对象的 getMessage 方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">getMediator</span><span class="p">().</span><span class="na">getMessage</span><span class="p">(</span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">TV</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">TV</span><span class="p">(</span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mediator</span><span class="p">.</span><span class="na">register</span><span class="p">(</span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">getMediator</span><span class="p">().</span><span class="na">getMessage</span><span class="p">(</span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">startTv</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;It&#39;s time to StartTv!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">stopTv</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;StopTv!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CoffeeMachine</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Colleague</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CoffeeMachine</span><span class="p">(</span><span class="n">Mediator</span><span class="w"> </span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">mediator</span><span class="p">,</span><span class="w"> </span><span class="n">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mediator</span><span class="p">.</span><span class="na">register</span><span class="p">(</span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sendMessage</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">stateChange</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">getMediator</span><span class="p">().</span><span class="na">getMessage</span><span class="p">(</span><span class="n">stateChange</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">startCoffee</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;It&#39;s time to startcoffee!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finishCoffee</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After 5 minutes!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Coffee is ok!&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">sendMessage</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>中介者模式将一个网状的系统结构变成一个以中介者对象为中心的星形结构，在这个星型结构中，使用中介者对象与其他对象的一对多关系来取代原有对象之间的多对多关系。
+中介者模式在事件驱动类软件中应用较为广泛，特别是基于GUI（图形用户界面）的应用软件，此外，在类与类之间存在错综复杂的关联关系的系统中，中介者模式都能得到较好的应用。</p>
+<p>优点：</p>
+<ul>
+<li>减少类间依赖，降低了耦合，符合迪米特法则。</li>
+<li>简化了对象之间的交互，它用中介者和同事的一对多交互代替了原来同事之间的多对多交互，一对多关系更容易理解、维护和扩展，将原本难以理解的网状结构转换成相对简单的星型结构。</li>
+<li>降低了类的复杂度，将一对多转化成了一对一。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>中介者承担了较多的责任，一旦中介者出现了问题，整个系统就会受到影响。</li>
+<li>如果设计不当，可能会导致具体中介者类非常复杂，使得系统难以维护，在实际使用过程中要特别注意。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>主要解决对象与对象之间存在大量的关联关系，这样势必会导致系统的结构变得很复杂，同时若一个对象发生改变，我们也需要跟踪与之相关联的对象，同时做出相应的处理。
+应当注意不应当在职责混乱的时候使用。</li>
+<li>系统中对象之间存在比较复杂的引用关系，导致它们之间的依赖关系结构混乱而且难以复用该对象。</li>
+<li>想通过一个中间类来封装多个类中的行为，而又不想生成太多的子类。</li>
+</ul>
+<h3 id="备忘录模式">备忘录模式</h3>
+<p>备忘录模式，在不破坏封装的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态，这样可以在以后将对象恢复到原先保存的状态。它是一种对象行为型模式，其别名为<code>Token</code>。
+在设计备忘录类时需要考虑其封装性，除了<code>Originator</code>类，不允许其他类来调用备忘录类<code>Memento</code>的构造函数与相关方法，如果不考虑封装性，允许其他类调用构造方法，将导致在备忘录中保存的历史状态发生改变，通过撤销操作所恢复的状态就不再是真实的历史状态，备忘录模式也就失去了本身的意义。
+所谓备忘录模式就是在不破坏封装的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态，这样可以在以后将对象恢复到原先保存的状态。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Originator</span><span class="w"> </span><span class="n">originator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Originator</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CareTaker</span><span class="w"> </span><span class="n">careTaker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CareTaker</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 保存状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">careTaker</span><span class="p">.</span><span class="na">saveMemento</span><span class="p">(</span><span class="n">originator</span><span class="p">.</span><span class="na">saveState</span><span class="p">(</span><span class="s">&#34; 状态#1 &#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">careTaker</span><span class="p">.</span><span class="na">saveMemento</span><span class="p">(</span><span class="n">originator</span><span class="p">.</span><span class="na">saveState</span><span class="p">(</span><span class="s">&#34; 状态#2 &#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">careTaker</span><span class="p">.</span><span class="na">saveMemento</span><span class="p">(</span><span class="n">originator</span><span class="p">.</span><span class="na">saveState</span><span class="p">(</span><span class="s">&#34; 状态#3 &#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;目前保存的状态为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">originator</span><span class="p">.</span><span class="na">getState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;开始恢复以前的状态 ....&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">originator</span><span class="p">.</span><span class="na">recover</span><span class="p">(</span><span class="n">careTaker</span><span class="p">.</span><span class="na">recover</span><span class="p">(</span><span class="n">0</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;恢复之后的状态为：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">originator</span><span class="p">.</span><span class="na">getState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Originator</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Memento</span><span class="w"> </span><span class="nf">saveState</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">state</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Memento</span><span class="p">(</span><span class="n">state</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">recover</span><span class="p">(</span><span class="n">Memento</span><span class="w"> </span><span class="n">memento</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="n">memento</span><span class="p">.</span><span class="na">getState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 备忘录对象 保存对象信息
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Memento</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 需要保存状态
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Memento</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">state</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">getState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 管理备忘录对象
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CareTaker</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Memento</span><span class="o">&gt;</span><span class="w"> </span><span class="n">mementos</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Memento</span><span class="w"> </span><span class="nf">recover</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="k">return</span><span class="w"> </span><span class="n">mementos</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">index</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">saveMemento</span><span class="p">(</span><span class="n">Memento</span><span class="w"> </span><span class="n">memento</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">mementos</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">memento</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>备忘录模式在很多软件的使用过程中普遍存在，但是在应用软件开发中，它的使用频率并不太高，因为现在很多基于窗体和浏览器的应用软件并没有提供撤销操作。
+如果需要为软件提供撤销功能，备忘录模式无疑是一种很好的解决方案。在一些字处理软件、图像编辑软件、数据库管理系统等软件中备忘录模式都得到了很好的应用。
+为了符合迪米特原则，还要增加一个管理备忘录的类(<code>CareTaker</code>)，为了节约内存，可使用原型模式和备忘录模式。</p>
+<p>优点：</p>
+<ul>
+<li>给用户提供了一种可以恢复状态的机制，可以使用户能够比较方便地回到某个历史的状态。</li>
+<li>实现了信息的封装，使得用户不需要关心状态的保存细节。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>消耗资源。如果类的成员变量过多，势必会占用比较大的资源，而且每一次保存都会消耗一定的内存。每保存一次对象的状态都需要消耗一定的系统资源。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>很多时候我们总是需要记录一个对象的内部状态，这样做的目的就是为了允许用户取消不确定或者错误的操作，能够恢复到他原先的状态，使得他有&quot;后悔药&quot;可吃。</li>
+<li>需要保存/恢复数据的相关状态场景。</li>
+<li>提供一个可回滚的操作。</li>
+</ul>
+<h3 id="观察者模式">观察者模式</h3>
+<p>观察者模式，定义对象之间的一种一对多依赖关系，使得每当一个对象状态发生改变时，其相关依赖对象皆得到通知并被自动更新。
+观察者模式的别名包括发布-订阅模式、模型-视图模式、源-监听器模式或从属者模式。观察者模式是一种对象行为型模式。</p>
+<p>观察者模式描述了如何建立对象与对象之间的依赖关系，以及如何构造满足这种需求的系统。
+观察者模式包含观察目标和观察者两类对象，一个目标可以有任意数目的与之相依赖的观察者，一旦观察目标的状态发生改变，所有的观察者都将得到通知。
+作为对这个通知的响应，每个观察者都将监视观察目标的状态以使其状态与目标状态同步，这种交互也称为发布-订阅(Publish-Subscribe)。观察目标是通知的发布者，它发出通知时并不需要知道谁是它的观察者，可以有任意数目的观察者订阅它并接收通知。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WeatherData</span><span class="w"> </span><span class="n">weatherData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WeatherData</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">CurrentCondition</span><span class="w"> </span><span class="n">currentCondition</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CurrentCondition</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">BaiduSite</span><span class="w"> </span><span class="n">baiduSite</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BaiduSite</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 注册观察者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">registerObserver</span><span class="p">(</span><span class="n">currentCondition</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">registerObserver</span><span class="p">(</span><span class="n">baiduSite</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 设置数据 一旦数据变化 所有的观察者都会变化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">setWeatherData</span><span class="p">(</span><span class="n">10f</span><span class="p">,</span><span class="w"> </span><span class="n">20f</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 移除注册观察者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">removeObserver</span><span class="p">(</span><span class="n">baiduSite</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 唤醒所有已经注册的观察者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">weatherData</span><span class="p">.</span><span class="na">notifyObservers</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Subject</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">registerObserver</span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">removeObserver</span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">notifyObservers</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * 观察者
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">Observer</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="kt">float</span><span class="w">  </span><span class="n">temperature</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">WeatherData</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Subject</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Observer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">observers</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setWeatherData</span><span class="p">(</span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">registerObserver</span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">observers</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">observer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">removeObserver</span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">observers</span><span class="p">.</span><span class="na">contains</span><span class="p">(</span><span class="n">observer</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">observers</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">observer</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">notifyObservers</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 唤醒所有的观察者</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Observer</span><span class="w"> </span><span class="n">observer</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">observers</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">observer</span><span class="p">.</span><span class="na">update</span><span class="p">(</span><span class="n">temperature</span><span class="p">,</span><span class="n">humidity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CurrentCondition</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Observer</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">displayed</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">displayed</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;===当前天气情况===&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前湿度：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前温度：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BaiduSite</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Observer</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">update</span><span class="p">(</span><span class="kt">float</span><span class="w"> </span><span class="n">temperature</span><span class="p">,</span><span class="w"> </span><span class="kt">float</span><span class="w"> </span><span class="n">humidity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">temperature</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">humidity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">displayed</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">displayed</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;===当前百度网站天气情况===&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前湿度：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">temperature</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;当前温度：&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">humidity</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>观察者模式是一种使用频率非常高的设计模式，无论是移动应用、Web应用或者桌面应用，观察者模式几乎无处不在，它为实现对象之间的联动提供了一套完整的解决方案，凡是涉及到一对一或者一对多的对象交互场景都可以使用观察者模式。
+观察者模式广泛应用于各种编程语言的GUI事件处理的实现，在基于事件的XML解析技术（如SAX2）以及Web事件处理中也都使用了观察者模式。</p>
+<p>优点：</p>
+<ul>
+<li>观察者和被观察者是抽象耦合的。观察目标只需要维持一个抽象观察者的集合，无须了解其具体观察者。由于观察目标和观察者没有紧密地耦合在一起，因此它们可以属于不同的抽象化层次。</li>
+<li>观察者模式满足“开闭原则”的要求，增加新的具体观察者无须修改原有系统代码，在具体观察者与观察目标之间不存在关联关系的情况下，增加新的观察目标也很方便。</li>
+<li>观察者模式可以实现表示层和数据逻辑层的分离，定义了稳定的消息更新传递机制，并抽象了更新接口，使得可以有各种各样不同的表示层充当具体观察者角色。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>如果一个被观察者对象有很多的直接和间接的观察者的话，将所有的观察者都通知到会花费很多时间。</li>
+<li>如果在观察者和观察目标之间有循环依赖的话，观察目标会触发它们之间进行循环调用，可能导致系统崩溃。</li>
+<li>观察者模式没有相应的机制让观察者知道所观察的目标对象是怎么发生变化的，而仅仅只是知道观察目标发生了变化。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>一个对象状态改变给其他对象通知的问题，而且要考虑到易用和低耦合，保证高度的协作。一个对象（目标对象）的状态发生改变，所有的依赖对象（观察者对象）都将得到通知，进行广播通知。</li>
+<li>一个抽象模型有两个方面，其中一个方面依赖于另一个方面。将这些方面封装在独立的对象中使它们可以各自独立地改变和复用。</li>
+<li>一个对象的改变将导致其他一个或多个对象也发生改变，而不知道具体有多少对象将发生改变，可以降低对象之间的耦合度。</li>
+<li>一个对象必须通知其他对象，而并不知道这些对象是谁。</li>
+<li>需要在系统中创建一个触发链，A对象的行为将影响B对象，B对象的行为将影响C对象……，可以使用观察者模式创建一种链式触发机制。</li>
+</ul>
+<p>注意事项：</p>
+<ul>
+<li>Java中已经有了对观察者模式的支持类。</li>
+<li>避免循环引用。</li>
+<li>如果顺序执行，某一观察者错误会导致系统卡壳，一般采用异步方式。</li>
+</ul>
+<h3 id="状态模式">状态模式</h3>
+<p>状态模式，允许一个对象在其内部状态改变时改变它的行为，对象看起来似乎修改了它的类。其别名为状态对象，状态模式是一种对象行为型模式。
+状态模式用于解决系统中复杂对象的状态转换以及不同状态下行为的封装问题。当系统中某个对象存在多个状态，这些状态之间可以进行转换，而且对象在不同状态下行为不相同时可以使用状态模式。
+状态模式将一个对象的状态从该对象中分离出来，封装到专门的状态类中，使得对象状态可以灵活变化，对于客户端而言，无须关心对象状态的转换以及对象所处的当前状态，无论对于何种状态的对象，客户端都可以一致处理。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 创建活动对象，奖品有 1 个奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RaffleActivity</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 我们连续抽 300 次奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">30</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;--------第&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;次抽奖----------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 参加抽奖，第一步点击扣除积分</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">debuctMoney</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 第二步抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">raffle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 扣除积分 - 50</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 是否抽中奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 发放奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RaffleActivity</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// state 表示活动当前的状态，是变化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 奖品数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 四个属性，表示四种状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">noRafflleState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NoRaffleState</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">canRaffleState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CanRaffleState</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">dispenseState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DispenseState</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">State</span><span class="w"> </span><span class="n">dispensOutState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DispenseOutState</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//构造器</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//1. 初始化当前的状态为 noRafflleState（即不能抽奖的状态）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//2. 初始化奖品的数量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">RaffleActivity</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getNoRafflleState</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//扣分, 调用当前状态的 deductMoney</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">debuctMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">state</span><span class="p">.</span><span class="na">deductMoney</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果当前的状态是抽奖成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">state</span><span class="p">.</span><span class="na">raffle</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//领取奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">state</span><span class="p">.</span><span class="na">dispensePrize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">state</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">state</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">state</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//这里请大家注意，每领取一次奖品，count--</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getCount</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">curCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">count</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">curCount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setCount</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">count</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">count</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getNoRafflleState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">noRafflleState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNoRafflleState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">noRafflleState</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">noRafflleState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">noRafflleState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getCanRaffleState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">canRaffleState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setCanRaffleState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">canRaffleState</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">canRaffleState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">canRaffleState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getDispenseState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">dispenseState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setDispenseState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">dispenseState</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dispenseState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dispenseState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="nf">getDispensOutState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">dispensOutState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setDispensOutState</span><span class="p">(</span><span class="n">State</span><span class="w"> </span><span class="n">dispensOutState</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">dispensOutState</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">dispensOutState</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">DispenseOutState</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 初始化时传入活动引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">DispenseOutState</span><span class="p">(</span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;奖品发送完了，请下次再参加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;奖品发送完了，请下次再参加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;奖品发送完了，请下次再参加&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">DispenseState</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 初始化时传入活动引用，发放奖品后改变其状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">DispenseState</span><span class="p">(</span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不能扣除积分&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不能抽奖&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//发放奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getCount</span><span class="p">()</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;恭喜中奖了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 改变状态为不能抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getNoRafflleState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;很遗憾，奖品发送完了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 改变状态为奖品发送完毕, 后面我们就不可以抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getDispensOutState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//System.out.println(&#34;抽奖活动结束&#34;);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">//System.exit(0);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">NoRaffleState</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 初始化时传入活动引用，扣除积分后改变其状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">NoRaffleState</span><span class="p">(</span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 当前状态可以扣积分 , 扣除后，将状态设置成可以抽奖状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;扣除 50 积分成功，您可以抽奖了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getCanRaffleState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 当前状态不能抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;扣了积分才能抽奖喔！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 当前状态不能发奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不能发放奖品&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">CanRaffleState</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CanRaffleState</span><span class="p">(</span><span class="n">RaffleActivity</span><span class="w"> </span><span class="n">activity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">activity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">activity</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">deductMoney</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;已经扣取过了积分&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">//可以抽奖, 抽完奖后，根据实际情况，改成新的状态</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">raffle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;正在抽奖，请稍等！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Random</span><span class="w"> </span><span class="n">r</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Random</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">r</span><span class="p">.</span><span class="na">nextInt</span><span class="p">(</span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 10%中奖机会</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">num</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 改变活动状态为发放奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getDispenseState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;很遗憾没有抽中奖品！&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 改变状态为不能抽奖</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">activity</span><span class="p">.</span><span class="na">setState</span><span class="p">(</span><span class="n">activity</span><span class="p">.</span><span class="na">getNoRafflleState</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 不能发放奖品</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dispensePrize</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;没中奖，不能发放奖品&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>状态模式将一个对象在不同状态下的不同行为封装在一个个状态类中，通过设置不同的状态对象可以让环境对象拥有不同的行为，而状态转换的细节对于客户端而言是透明的，方便了客户端的使用。
+在实际开发中，状态模式具有较高的使用频率，在工作流和游戏开发中状态模式都得到了广泛的应用，例如公文状态的转换、游戏中角色的升级等。</p>
+<p>优点：</p>
+<ul>
+<li>封装了状态的转换规则，在状态模式中可以将状态的转换代码封装在环境类或者具体状态类中，可以对状态转换代码进行集中管理，而不是分散在一个个业务方法中。</li>
+<li>将所有与某个状态有关的行为放到一个类中，只需要注入一个不同的状态对象即可使环境对象拥有不同的行为。</li>
+<li>可以让多个环境对象共享一个状态对象，从而减少系统中对象的个数。</li>
+<li>允许状态转换逻辑与状态对象合成一体，而不是提供一个巨大的条件语句块，状态模式可以让我们避免使用庞大的条件语句来将业务方法和状态转换代码交织在一起。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>状态模式的使用必然会增加系统类和对象的个数。</li>
+<li>状态模式的结构与实现都较为复杂，如果使用不当将导致程序结构和代码的混乱。</li>
+<li>状态模式对“开闭原则”的支持并不太好，增加新的状态类需要修改那些负责状态转换的源代码，否则无法转换到新增状态；而且修改某个状态类的行为也需修改对应类的源代码。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>状态模式主要解决对象的行为依赖于它的状态（属性），并且可以根据它的状态改变而改变它的相关行为。
+在代码中包含大量与对象状态有关的条件语句时应该考虑使用状态模式。应当注意的是，在行为受状态约束的时候使用状态模式，状态应该不超过5个，太多则导致程序结构、代码混乱。</li>
+<li>行为随状态改变而改变的场景。</li>
+<li>条件、分支语句的代替者。</li>
+</ul>
+<h3 id="策略模式">策略模式</h3>
+<p>策略模式，定义一系列算法类，将每一个算法封装起来，并让它们可以相互替换，策略模式让算法独立于使用它的客户而变化，也称为政策模式。策略模式是一种对象行为型模式。
+策略模式的主要目的是将算法的定义与使用分开，也就是将算法的行为和环境分开，将算法的定义放在专门的策略类中，每一个策略类封装了一种实现算法，使用算法的环境类针对抽象策略类进行编程，符合“依赖倒转原则”。
+在出现新的算法时，只需要增加一个新的实现了抽象策略类的具体策略类即可。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Bird</span><span class="w"> </span><span class="n">bird</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Bird</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">bird</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Duck</span><span class="w"> </span><span class="n">duck</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Duck</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">duck</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Dog</span><span class="w"> </span><span class="n">dog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dog</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;变为会飞 ：&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dog</span><span class="p">.</span><span class="na">setFlyStrategy</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">GoodFlyStrategy</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dog</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">FlyStrategy</span><span class="w"> </span><span class="n">flyStrategy</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setFlyStrategy</span><span class="p">(</span><span class="n">FlyStrategy</span><span class="w"> </span><span class="n">flyStrategy</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">flyStrategy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">flyStrategy</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Bird</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractStrategy</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Bird</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;小鸟&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">GoodFlyStrategy</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Duck</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Duck</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;鸭子&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BadFlyStrategy</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Dog</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&#34;狗&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">NoFlyStrategy</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">flyStrategy</span><span class="p">.</span><span class="na">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">interface</span> <span class="nc">FlyStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">GoodFlyStrategy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FlyStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;擅长飞翔 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">BadFlyStrategy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FlyStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不擅长飞翔 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">NoFlyStrategy</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FlyStrategy</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">fly</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;不会飞 ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>策略模式用于算法的自由切换和扩展，它是应用较为广泛的设计模式之一。策略模式对应于解决某一问题的一个算法族，允许用户从该算法族中任选一个算法来解决某一问题，同时可以方便地更换算法或者增加新的算法。
+只要涉及到算法的封装、复用和切换都可以考虑使用策略模式。如果一个系统的策略多于四个，就需要考虑使用混合模式，解决策略类膨胀的问题。</p>
+<p>优点：</p>
+<ul>
+<li>策略模式提供了对“开闭原则”的完美支持，用户可以在不修改原有系统的基础上选择算法或行为，也可以灵活地增加新的算法或行为。</li>
+<li>策略模式提供了管理相关的算法族的办法。策略类的等级结构定义了一个算法或行为族，恰当使用继承可以把公共的代码移到抽象策略类中，从而避免重复的代码。</li>
+<li>策略模式提供了一种算法的复用机制，由于将算法单独提取出来封装在策略类中，因此不同的环境类可以方便地复用这些策略类。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>客户端必须知道所有的策略类，并自行决定使用哪一个策略类。这就意味着客户端必须理解这些算法的区别，以便适时选择恰当的算法。
+换言之，策略模式只适用于客户端知道所有的算法或行为的情况。</li>
+<li>所有策略类都需要对外暴露。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>一个系统有许多许多类，而区分它们的只是他们直接的行为，那么使用策略模式可以动态地让一个对象在许多行为中选择一种行为。</li>
+<li>如果一个对象有很多的行为，如果不用恰当的模式，这些行为就只好使用多重的条件选择语句来实现。</li>
+</ul>
+<h3 id="模板方法模式">模板方法模式</h3>
+<p>模板方法模式，定义一个操作中的算法骨架，而将算法的一些步骤延迟到子类中，使得子类可以不改变该算法结构的情况下重定义该算法的某些特定步骤。
+模板方法模式是一种基于继承的代码复用技术，它是一种类行为型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====红豆豆浆=====&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">RedBean</span><span class="w"> </span><span class="n">redBean</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RedBean</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">redBean</span><span class="p">.</span><span class="na">template</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====花生豆浆=====&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Peanut</span><span class="w"> </span><span class="n">peanut</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Peanut</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">peanut</span><span class="p">.</span><span class="na">template</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=====豆浆=====&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">None</span><span class="w"> </span><span class="n">none</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">None</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">none</span><span class="p">.</span><span class="na">template</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SoyaMilk</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">template</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">filterMaterial</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">soak</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">isAppended</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">add</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">over</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">filterMaterial</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第一步：筛选材料&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">soak</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第二步：浸泡&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">over</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第四步：打豆浆&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 钩子方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isAppended</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Peanut</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SoyaMilk</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第三步：加入花生&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">RedBean</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SoyaMilk</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;第三步：加入红豆&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">None</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">SoyaMilk</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">add</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isAppended</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>模板方法模式是基于继承的代码复用技术，它体现了面向对象的诸多重要思想，是一种使用较为频繁的模式。
+模板方法模式广泛应用于框架设计中，以确保通过父类来控制处理流程的逻辑顺序（如框架的初始化，测试流程的设置等）。</p>
+<p>优点：</p>
+<ul>
+<li>它封装了不变部分，扩展可变部分。它把认为是不变部分的算法封装到父类中实现，而把可变部分算法由子类继承实现，便于子类继续扩展。</li>
+<li>它在父类中提取了公共的部分代码，便于代码复用。</li>
+<li>部分方法是由子类实现的，因此子类可以通过扩展方式增加相应的功能，符合开闭原则。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>需要为每一个基本方法的不同实现提供一个子类，如果父类中可变的基本方法太多，将会导致类的个数增加，系统更加庞大，设计也更加抽象，间接地增加了系统实现的复杂度。此时，可结合桥接模式来进行设计。</li>
+<li>由于继承关系自身的缺点，如果父类添加新的抽象方法，则所有子类都要改一遍。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>算法的整体步骤很固定，但其中个别部分易变时，这时候可以使用模板方法模式，将容易变的部分抽象出来，供子类实现。</li>
+<li>当多个子类存在公共的行为时，可以将其提取出来并集中到一个公共父类中以避免代码重复。首先，要识别现有代码中的不同之处，并且将不同之处分离为新的操作。最后，用一个调用这些新的操作的模板方法来替换这些不同的代码。</li>
+<li>当需要控制子类的扩展时，模板方法只在特定点调用钩子操作，这样就只允许在这些点进行扩展。</li>
+</ul>
+<h3 id="访问者模式">访问者模式</h3>
+<p>访问者模式，提供一个作用于某对象结构中的各元素的操作表示，它使我们可以在不改变各元素的类的前提下定义作用于这些元素的新操作。访问者模式是一种对象行为型模式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ObjectStructure</span><span class="w"> </span><span class="n">objectStructure</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ObjectStructure</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">attach</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Man</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">attach</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">WoMan</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">attach</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Man</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">attach</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">WoMan</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示成功的评价</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Success</span><span class="w"> </span><span class="n">success</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Success</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">display</span><span class="p">(</span><span class="n">success</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;==================&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 显示失败的评价</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Fail</span><span class="w"> </span><span class="n">fail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Fail</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">objectStructure</span><span class="p">.</span><span class="na">display</span><span class="p">(</span><span class="n">fail</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Action</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getManResult</span><span class="p">(</span><span class="n">Man</span><span class="w"> </span><span class="n">man</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getWomanResult</span><span class="p">(</span><span class="n">WoMan</span><span class="w"> </span><span class="n">woman</span><span class="w"> </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Success</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Action</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getManResult</span><span class="p">(</span><span class="n">Man</span><span class="w"> </span><span class="n">man</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;男人觉得很赞～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getWomanResult</span><span class="p">(</span><span class="n">WoMan</span><span class="w"> </span><span class="n">woman</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;女人觉得很赞～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Fail</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Action</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getManResult</span><span class="p">(</span><span class="n">Man</span><span class="w"> </span><span class="n">man</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;男人觉得很失败～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">getWomanResult</span><span class="p">(</span><span class="n">WoMan</span><span class="w"> </span><span class="n">woman</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;女人觉得很失败～&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span>  <span class="nc">Person</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">accpet</span><span class="p">(</span><span class="n">Action</span><span class="w"> </span><span class="n">action</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">WoMan</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Person</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">accpet</span><span class="p">(</span><span class="n">Action</span><span class="w"> </span><span class="n">action</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="n">action</span><span class="p">.</span><span class="na">getWomanResult</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Man</span><span class="w">  </span><span class="kd">extends</span><span class="w"> </span><span class="n">Person</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">accpet</span><span class="p">(</span><span class="n">Action</span><span class="w"> </span><span class="n">action</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">action</span><span class="p">.</span><span class="na">getManResult</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ObjectStructure</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Person</span><span class="o">&gt;</span><span class="w"> </span><span class="n">people</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">attach</span><span class="p">(</span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">people</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">detach</span><span class="p">(</span><span class="n">Person</span><span class="w"> </span><span class="n">person</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">people</span><span class="p">.</span><span class="na">remove</span><span class="p">(</span><span class="n">person</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">display</span><span class="p">(</span><span class="n">Action</span><span class="w"> </span><span class="n">acion</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">people</span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">item</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">item</span><span class="p">.</span><span class="na">accpet</span><span class="p">(</span><span class="n">acion</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>由于访问者模式的使用条件较为苛刻，本身结构也较为复杂，因此在实际应用中使用频率不是特别高。
+当系统中存在一个较为复杂的对象结构，且不同访问者对其所采取的操作也不相同时，可以考虑使用访问者模式进行设计。
+在XML文档解析、编译器的设计、复杂集合对象的处理等领域访问者模式得到了一定的应用。</p>
+<p>优点：</p>
+<ul>
+<li>扩展性好。增加新的访问操作很方便。使用访问者模式，增加新的访问操作就意味着增加一个新的具体访问者类，实现简单，无须修改源代码，符合“开闭原则”。</li>
+<li>复用性好。可以通过访问者来定义整个对象结构通用的功能，从而提高系统的复用程度。</li>
+<li>灵活性好。访问者模式将数据结构与作用于结构上的操作解耦，使得操作集合可相对自由地演化而不影响系统的数据结构。</li>
+<li>符合单一职责原则单一职责原则。访问者模式把相关的行为封装在一起，构成一个访问者，使每一个访问者的功能都比较单一。</li>
+</ul>
+<p>缺点：</p>
+<ul>
+<li>破坏封装。访问者模式中具体元素对访问者公布细节，这破坏了对象的封装性。具体元素对访问者公布细节，违反了迪米特法则。</li>
+<li>违反了依赖倒置原则依赖倒置原则。访问者模式依赖了具体类，而没有依赖抽象类。</li>
+</ul>
+<p>使用场景：</p>
+<ul>
+<li>需要对一个对象结构中的对象进行很多不同的并且不相关的操作，而需要避免让这些操作&quot;污染&quot;这些对象的类，使用访问者模式将这些封装到类中。访问者可以对功能进行统一，可以做报表、UI、拦截器与过滤器。</li>
+<li>对象结构中对象对应的类很少改变，但经常需要在此对象结构上定义新的操作。</li>
+<li>需要对一个对象结构中的对象进行很多不同的并且不相关的操作，而需要避免让这些操作&quot;污染&quot;这些对象的类，也不希望在增加新操作时修改这些类。</li>
+</ul>
+</div>
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diff --git a/docs/posts/javabasics/rookie-objectclass-methods/index.html b/docs/posts/javabasics/rookie-objectclass-methods/index.html
new file mode 100644
index 00000000..ac2d4942
--- /dev/null
+++ b/docs/posts/javabasics/rookie-objectclass-methods/index.html
@@ -0,0 +1,1650 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
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+	
+	
+	<title>JavaObject类方法 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="概览 Object类位于java.lang包中，编译时会自动导入。当我们创建一个类时，如果没有明确继承一个父类，那么它就会自动继承Object，成为Object的" />
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+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
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+        <ul class="nav">
+            
+        <ul class="nav">
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+            
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+        <ul class="nav">
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+            
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+            </li>
+            
+            
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+        
+        
+        
+        
+        
+        
+        
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+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ad%89%e4%bb%b7%e5%85%b3%e7%b3%bb">
+                    等价关系
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%8e%e5%8f%8c%e7%ad%89%e5%8f%b7">
+                    与双等号
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8d%e5%86%99equals%e6%96%b9%e6%b3%95">
+                    重写equals方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashcode">
+                    hashCode
+                </a>
+            </li>
+            
+            
+        </ul>
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+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%94%af%e4%b8%80%e6%80%a7">
+                    唯一性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#hashcode%e4%b8%8eequals">
+                    hashCode与equals
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8d%e5%86%99hashcode%e6%96%b9%e6%b3%95">
+                    重写hashCode方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#tostring">
+                    toString
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%87%8d%e5%86%99tostring%e6%96%b9%e6%b3%95">
+                    重写toString方法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%bf%e7%94%a8tostring">
+                    使用toString
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#clone">
+                    clone
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#cloneable%e6%8e%a5%e5%8f%a3">
+                    Cloneable接口
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b5%85%e6%8b%b7%e8%b4%9d%e4%b8%8e%e6%b7%b1%e6%8b%b7%e8%b4%9d">
+                    浅拷贝与深拷贝
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#clone%e7%9a%84%e6%9b%bf%e4%bb%a3">
+                    clone的替代
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#finalize">
+                    finalize
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#getclass">
+                    getClass
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#notify">
+                    notify
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+            </li>
+            
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+        
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+        
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+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#notifyall">
+                    notifyAll
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wait">
+                    wait
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
+        
+        
+        
+
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+                        <h2 id="post_single_title">JavaObject类方法</h2>
+                        <span id="post_page_title_date" class="date">2021.07.10</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
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+                    <div class="post_content markdown"><h2 id="概览">概览</h2>
+<p><code>Object</code>类位于<code>java.lang</code>包中，编译时会自动导入。当我们创建一个类时，如果没有明确继承一个父类，那么它就会自动继承<code>Object</code>，成为<code>Object</code>的子类。
+<code>Object</code>类可以显示继承，也可以隐式继承，效果都是一样的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Object</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// to do</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">A</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// to do</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>Java<code>Object</code>类是所有类的父类，也就是说Java的所有类都继承了<code>Object</code>。因此，<code>Object</code>类提供了一组通用的方法，这些方法可以在所有Java对象上调用。</p>
+<table>
+<thead>
+<tr>
+<th>方法名称</th>
+<th>方法作用</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>equals</td>
+<td>比较两个对象是否相同</td>
+</tr>
+<tr>
+<td>hashCode</td>
+<td>获取对象的哈希值</td>
+</tr>
+<tr>
+<td>toString</td>
+<td>返回对象的字符串表示形式</td>
+</tr>
+<tr>
+<td>clone</td>
+<td>创建并返回一个对象的拷贝</td>
+</tr>
+<tr>
+<td>finalize</td>
+<td>当垃圾收集确定不再有对对象的引用时，由垃圾收集器在对象上调用</td>
+</tr>
+<tr>
+<td>getClass</td>
+<td>获取对象运行时的类</td>
+</tr>
+<tr>
+<td>notify</td>
+<td>唤醒在该对象上等待的某个线程</td>
+</tr>
+<tr>
+<td>notifyAll</td>
+<td>唤醒在该对象上等待的所有线程</td>
+</tr>
+<tr>
+<td>wait</td>
+<td>让当前线程进入等待(阻塞)状态。直到其他线程调用此对象的<code>notify()</code>方法或<code>notifyAll()</code>方法。</td>
+</tr>
+</tbody>
+</table>
+<h2 id="equals">equals</h2>
+<p><code>equals</code>方法是Java中的一个重要方法，用于比较两个对象是否相等。默认情况下，<code>Object</code>类中的<code>equals</code>方法比较的是对象的内存地址，但许多类会重写这个方法以实现自定义的比较逻辑。
+<code>Object</code>类中的<code>equals()</code>源码如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>该实现只是简单地比较两个对象的引用是否相同，即是否指向同一个内存地址。</p>
+<h3 id="等价关系">等价关系</h3>
+<p>在Java中，<code>equals</code>方法用于确定两个对象是否相等。为了正确实现这个方法，必须确保它满足等价关系的要求。等价关系是一种自反的、对称的和传递的关系。
+具体来说，<code>equals</code>方法必须遵循以下规则：</p>
+<ul>
+<li>自反性：对于任何非<code>null</code>的引用值<code>x</code>，<code>x.equals(x)</code>必须返回<code>true</code>。</li>
+<li>对称性：对于任何非<code>null</code>的引用值<code>x</code>和<code>y</code>，如果<code>x.equals(y)</code>返回<code>true</code>，那么<code>y.equals(x)</code>也必须返回<code>true</code>。</li>
+<li>传递性：对于任何非<code>null</code>的引用值<code>x</code>、<code>y</code>和<code>z</code>，如果<code>x.equals(y)</code>返回<code>true</code>，并且<code>y.equals(z)</code>返回<code>true</code>，那么<code>x.equals(z)</code>也必须返回<code>true</code>。</li>
+<li>一致性：对于任何非<code>null</code>的引用值<code>x</code>和<code>y</code>，只要对象的状态没有改变，多次调用<code>x.equals(y)</code>应当返回相同的结果。</li>
+<li>非空性：对于任何非<code>null</code>的引用值<code>x</code>，<code>x.equals(null)</code>必须返回<code>false</code>。</li>
+</ul>
+<h3 id="与双等号">与双等号</h3>
+<p>对于基本类型，<code>==</code>判断两个值是否相等，基本类型没有<code>equals()</code>方法。对于引用类型，<code>==</code>判断两个变量是否引用同一个对象，而<code>equals()</code>判断引用的对象是否等价。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Integer x = new Integer(1);
+</span></span><span class="line"><span class="cl">Integer y = new Integer(1);
+</span></span><span class="line"><span class="cl">System.out.println(x.equals(y)); // true
+</span></span><span class="line"><span class="cl">System.out.println(x == y);      // false
+</span></span></code></pre></div><p><code>equals()</code>作用是判断两个对象是否相等，但一般有两种情况：</p>
+<ol>
+<li>类没有覆盖<code>equals</code>方法，则相当于通过 <code>==</code>来比较这两个对象的地址；</li>
+<li>类覆盖<code>equals</code>方法，一般我们通过<code>equals()</code>来比较两个对象的内容是否相等，相等则返回<code>true</code>；</li>
+</ol>
+<p>之前有一道经典的面试题，问的就是<code>==</code>和<code>equals</code>的区别。
+<code>==</code>运算符比较两个引用是否指向同一个对象。
+<code>equals</code>方法比较两个对象的内容是否相等。默认情况下，<code>Object</code>类中的<code>equals</code>方法比较的是对象的内存地址，但许多类会重写这个方法以比较对象的内容。</p>
+<h3 id="重写equals方法">重写equals方法</h3>
+<p><code>equals()</code>在不重写的情况下与<code>==</code>作用一样，都是比较的内存中的地址，但是<code>equals()</code>可以重写。
+重写<code>equals</code>方法的目的是为了定义对象内容相等的逻辑。默认的<code>equals</code>方法比较内存地址，而我们通常需要比较对象的内容。
+重写<code>equals</code>方法一般思路：</p>
+<ol>
+<li>检查是否为同一个对象的引用，如果是直接返回<code>true</code>；</li>
+<li>检查是否是同一个类型，如果不是，直接返回<code>false</code>；</li>
+<li>将<code>Object</code>对象进行转型；</li>
+<li>判断每个关键域是否相等；</li>
+</ol>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">EqualExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">z</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">o</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">o</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">o</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">getClass</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">o</span><span class="p">.</span><span class="na">getClass</span><span class="p">())</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">that</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">EqualExample</span><span class="p">)</span><span class="w"> </span><span class="n">o</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">that</span><span class="p">.</span><span class="na">x</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">y</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">that</span><span class="p">.</span><span class="na">y</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">z</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">that</span><span class="p">.</span><span class="na">z</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="hashcode">hashCode</h2>
+<p>在Java中<code>hashcode</code>方法是<code>Object</code>类的<code>native</code>方法，返回值为int类型，根据一定的规则将与对象相关的信息，如对象的存储地址，对象的字段等，映射成一个数值，这个数值称作为<code>hash</code>值。
+<code>hashCode</code>方法在Java中非常重要，尤其在使用哈希表（如<code>HashMap</code>、<code>HashSet</code>等）时。<code>hashCode</code>方法返回一个整数，该整数称为对象的哈希码。这个哈希码用于确定对象在哈希表中的存储位置。</p>
+<p>为了使<code>hashCode</code>方法正确工作，并确保在集合中对象的行为正确，必须遵循以下约定：</p>
+<ul>
+<li>如果两个对象不相等，它们的哈希码不一定要不同。但是不相等的对象产生不同哈希码，总体上呈均匀分布，可以提高哈希表的性能。</li>
+<li>在程序的同一执行过程中，只要对象的信息没有被修改，多次调用<code>hashCode</code>方法应该返回相同的整数。</li>
+<li>如果根据<code>equals</code>方法，两个对象是相等的，那么调用这两个对象的<code>hashCode</code>方法必须返回相同的整数。</li>
+</ul>
+<p><code>hashCode</code>方法源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">hashCode</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>根据这个方法的声明可知，该方法返回一个<code>int</code>类型的数值，并且是本地方法，因此在<code>Object</code>类中并没有给出具体的实现。</p>
+<h3 id="唯一性">唯一性</h3>
+<p>对于包含容器类型的程序设计语言来说，基本上都会涉及到<code>hashCode</code>。
+在Java中也一样，<code>hashCode</code>方法的主要作用是为了配合基于散列的集合一起正常运行，这样的散列集合包括<code>HashSet、HashMap</code>以及<code>HashTable</code>。</p>
+<p>在集合中已经存在上万条数据或更多的数据场景下向集合中插入对象时，如何判别在集合中是否已经存在该对象了？</p>
+<p>如果采用<code>equals</code>方法去逐一比较，效率必然是一个问题，此时<code>hashCode</code>方法的优点就体现出来了。
+因为两个不同的对象可能会有相同的<code>hashCode</code>值，所有不能通过<code>hashCode</code>值来判断两个对象是否相等，但是可以直接根据<code>hashcode</code>值判断两个对象不等，如果两个对象的<code>hashCode</code>值不等，则必定是两个不同的对象。
+当集合要添加新的对象时，先调用这个对象的<code>hashCode</code>方法，得到对应的<code>hashcode</code>值，如果存放的<code>hash</code>值中没有该<code>hashcode</code>值，它就可以直接存进去，不用再进行任何比较了。
+如果存在该<code>hashcode</code>值，就调用它的<code>equals</code>方法与新元素进行比较，相同的话就不存了，不相同就去存。</p>
+<p>需要额外注意的是，设计<code>hashCode</code>方法时最重要的因素就是，无论何时，对同一个对象调用<code>hashCode()</code>都应该产生同样的值。
+如果在将一个对象用<code>put()</code>添加进<code>HashMap</code>时产生一个<code>hashCdoe</code>值，而用<code>get()</code>取出时却产生了另一个<code>hashCode</code>值，那么就无法获取该对象了。
+所以如果你的<code>hashCode</code>方法依赖于对象中易变的数据，就要当心了，因为此数据发生变化时，<code>hashCode()</code>方法就会生成一个不同的散列码，从而获取不到该对象。
+所以在重写<code>hashCode</code>方法和<code>equals</code>方法的时候，如果对象中的数据易变，则最好在<code>equals</code>方法和<code>hashCode</code>方法中不要依赖于该字段。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Person</span><span class="w"> </span><span class="n">p1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Person</span><span class="p">(</span><span class="s">&#34;lucy&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">22</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 85134311</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">p1</span><span class="p">.</span><span class="na">hashCode</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashMap</span><span class="o">&lt;</span><span class="n">Person</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">hashMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">hashMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">p1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">p1</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="n">13</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// null</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">hashMap</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">p1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Person</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Person</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setAge</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">hashCode</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">name</span><span class="p">.</span><span class="na">hashCode</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">37</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">obj</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">.</span><span class="na">equals</span><span class="p">(((</span><span class="n">Person</span><span class="p">)</span><span class="w"> </span><span class="n">obj</span><span class="p">).</span><span class="na">name</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">age</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p">((</span><span class="n">Person</span><span class="p">)</span><span class="w"> </span><span class="n">obj</span><span class="p">).</span><span class="na">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="hashcode与equals">hashCode与equals</h3>
+<p><code>hashCode()</code>返回散列值，而<code>equals()</code>是用来判断两个对象是否等价。等价的两个对象散列值一定相同，但是散列值相同的两个对象不一定等价。
+<code>equals()</code>地址比较是通过对象的哈希值来比较的。<code>hash</code>值是由<code>hashCode</code>方法产生的，<code>hashCode</code>属于<code>Object</code>类的本地方法，默认使用<code>==</code>比较两个对象。
+如果<code>equals()</code>相等<code>，hashcode</code>一定相等，如果<code>hashcode</code>相等，<code>equals</code>不一定相等。所以在覆盖<code>equals</code>方法时应当总是覆盖<code>hashCode</code>方法，保证等价的两个对象散列值也相等。</p>
+<p>下面的代码中，新建了两个等价的对象，并将它们添加到<code>HashSet</code>中。
+我们希望将这两个对象当成一样的，只在集合中添加一个对象，但是因为<code>EqualExample</code>没有实现<code>hashCode()</code>方法，因此这两个对象的散列值是不同的，最终导致集合添加了两个等价的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">e1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EqualExample</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">EqualExample</span><span class="w"> </span><span class="n">e2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">EqualExample</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">e1</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">e2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HashSet</span><span class="o">&lt;</span><span class="n">EqualExample</span><span class="o">&gt;</span><span class="w"> </span><span class="n">set</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashSet</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">e1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">set</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">e2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">set</span><span class="p">.</span><span class="na">size</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>所以在覆盖 <code>equals()</code>方法时应当总是覆盖<code>hashCode</code>方法，保证等价的两个对象散列值也相等。</p>
+<h3 id="重写hashcode方法">重写hashCode方法</h3>
+<p>重写<code>hashCode</code>方法规则：</p>
+<ul>
+<li>把某个非零的常数值，保存在一个名为<code>result</code>的int类型的常量中；</li>
+<li>字段值哈希码的计算：
+<ul>
+<li>如果是<code>boolean</code>类型，<code>true</code>为1，<code>false</code>则为0；</li>
+<li>如果是<code>byte、char、short</code>和<code>int</code>类型，需要强制转为int的值；</li>
+<li>如果是<code>long</code>类型，计算<code>(int)(f^(f&gt;&gt;32))</code>；</li>
+<li>如果是<code>float</code>类型，计算<code>Float.floatToIntBits(f)</code>；</li>
+<li>如果是<code>double</code>类型，计算<code>Double.doubleToLongBits(f)</code>，再按照<code>long</code>的方法进行计算；</li>
+<li>如果是引用类型，则调用其<code>hashCode</code>方法，假设其<code>hashCode</code>满足你的需求；</li>
+</ul>
+</li>
+<li>代入公式<code>result = result * 31 + c</code>，返回<code>result</code>；</li>
+</ul>
+<p>《Effective Java》的作者推荐使用基于17和31的散列码的算法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">hashCode</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">17</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">31</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">31</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">y</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">31</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">z</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>Java7新增的<code>Objects</code>类提供了计算<code>hashCode</code>的通用方法，可以很简洁实现<code>hashCode</code>方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">hashCode</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">Objects</span><span class="p">.</span><span class="na">hash</span><span class="p">(</span><span class="n">name</span><span class="p">,</span><span class="n">age</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>现在比较流行的写法是用<code>Lombok</code>，在类上使用<code>@EqualsAndHashCode</code>注解：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@EqualsAndHashCode</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Person</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 构造方法、getter、setter等略</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="tostring">toString</h2>
+<p><code>toString</code>方法是<code>Object</code>类里定义的，默认返回类名和它的引用地址，即<code>ToStringExample@4554617c</code>这种形式。其中@后面的数值为散列码的无符号十六进制表示。
+通常情况下，<code>toString</code>方法返回一个字符串，该字符串包含对象的状态信息，便于调试和日志记录。<code>Object</code>类<code>toString</code>源代码如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">getClass</span><span class="p">().</span><span class="na">getName</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;@&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">toHexString</span><span class="p">(</span><span class="n">hashCode</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="重写tostring方法">重写toString方法</h3>
+<p>当我们打印一个对象的引用时，实际是默认调用这个对象的<code>toString</code>方法。
+当打印的对象所在类没有重写<code>Object</code>中的<code>toString()</code>方法时，默认调用的是<code>Object</code>类中<code>toString()</code>方法，返回此对象所在的类及对应的堆空间对象实体的首地址值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// object.ToStringDemo@511d50c0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ToStringDemo</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ToStringDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>当我们打印对象所在类重写了<code>toString()</code>，调用的就是已经重写了的<code>toString</code>方法，一般重写是将类对象的属性信息返回。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ToStringDemo</span><span class="w"> </span><span class="n">toStringDemo</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ToStringDemo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">toStringDemo</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;lucy&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// ToStringDemo{name=&#39;lucy&#39;}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">toStringDemo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">ToStringDemo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setName</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;ToStringDemo{&#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;name=&#39;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">&#39;\&#39;&#39;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="sc">&#39;}&#39;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="使用tostring">使用toString</h3>
+<p>一般情况下，使用<code>toString</code>：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// object.ToStringDemo@511d50c0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ToStringDemo</span><span class="p">().</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>还有有一种隐式的调用方法，当你将一个对象与字符串进行拼接操作时，如果对象不是字符串类型，Java会自动调用该对象的<code>toString</code>方法来获取其字符串表示形式，然后再与其他字符串拼接起来。
+这种行为可以让代码更加简洁和易读，而不需要显式调用<code>toString</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Date</span><span class="w"> </span><span class="n">time</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;time = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">time</span><span class="p">);</span><span class="c1">//相当于下一行代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;time = &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">time</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>基本数据类型转换为<code>String</code>类型也是调用了对应包装类的<code>toString</code>方法，如<code>Integer</code>、<code>Double</code>等。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">int i = 10;
+</span></span><span class="line"><span class="cl">System.out.println(&#34;i=&#34; + i);
+</span></span></code></pre></div><h2 id="clone">clone</h2>
+<p>在Java中可以使用<code>clone</code>方法用于创建并返回一个对象的副本，对象克隆指的是创建一个新的对象，新对象的内容与原始对象相同。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>要在自定义类中实现对象的克隆，需要执行以下步骤：</p>
+<ul>
+<li>实现<code>Cloneable</code>接口，这是一个标记接口，自身没有方法；</li>
+<li>覆盖重写<code>clone</code>方法，可见性提升为<code>public</code>；</li>
+</ul>
+<h3 id="cloneable接口">Cloneable接口</h3>
+<p><code>Cloneable</code>接口是Java开发中常用的一个接口，它是一个标记接口。
+如果一个想要拷贝一个对象，就需要重写<code>Object</code>中的<code>clone</code>方法并让其实现<code>Cloneable</code>接口。如果只重写<code>clone</code>方法，不实现<code>Cloneable</code>接口就会报<code>CloneNotSupportedException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">protected</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>应当注意的是，<code>clone</code>方法并不是<code>Cloneable</code>接口的方法，而是<code>Object</code>的一个<code>protected</code>方法。
+<code>Cloneable</code>接口只是规定，如果一个类没有实现<code>Cloneable</code>接口又调用了<code>clone</code>方法，就会抛出<code>CloneNotSupportedException</code>。
+换言之，<code>clone</code>方法规定了想要拷贝对象，就需要实现<code>Cloneable</code>方法，<code>clone</code>方法让<code>Cloneable</code>接口变得有意义。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CloneExample</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="浅拷贝与深拷贝">浅拷贝与深拷贝</h3>
+<p>拷贝分为浅拷贝与深拷贝：</p>
+<ul>
+<li>浅拷贝：被复制对象的所有值属性都含有与原来对象的相同，而所有的对象引用属性仍然指向原来的对象；</li>
+<li>深拷贝：在浅拷贝的基础上，所有引用其他对象的变量也进行了<code>clone</code>，并指向被复制过的新对象；</li>
+</ul>
+<p>如果一个被复制的属性都是基本类型，那么只需要实现当前类的<code>Cloneable</code>机制就可以了，此为浅拷贝。
+如果被复制对象的属性包含其他实体类对象引用，那么这些实体类对象都需要实现<code>Cloneable</code>接口并覆盖<code>clone</code>方法。</p>
+<ul>
+<li>浅拷贝创建一个新对象，这个新对象的字段内容与原对象相同，但如果字段是引用类型（比如数组、对象），浅拷贝只复制引用地址，不复制引用的实际对象。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyObject</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">MyObject</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w"> </span><span class="c1">// 浅拷贝</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">MyObject</span><span class="w"> </span><span class="n">original</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">(</span><span class="n">42</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">MyObject</span><span class="w"> </span><span class="n">copy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">MyObject</span><span class="p">)</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">original</span><span class="p">.</span><span class="na">array</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">99</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">copy</span><span class="p">.</span><span class="na">array</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 99</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>深拷贝创建一个新对象，这个新对象和原对象完全独立，包括复制所有引用类型字段的实际对象，而不仅仅是引用地址。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyObject</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Cloneable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">MyObject</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">MyObject</span><span class="w"> </span><span class="nf">clone</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arrayCopy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w"> </span><span class="c1">// 复制数组</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">(</span><span class="n">value</span><span class="p">,</span><span class="w"> </span><span class="n">arrayCopy</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">3</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">MyObject</span><span class="w"> </span><span class="n">original</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">(</span><span class="n">42</span><span class="p">,</span><span class="w"> </span><span class="n">arr</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">MyObject</span><span class="w"> </span><span class="n">copy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">clone</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">original</span><span class="p">.</span><span class="na">array</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">99</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">copy</span><span class="p">.</span><span class="na">array</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">CloneNotSupportedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="clone的替代">clone的替代</h3>
+<p>虽然<code>Cloneable</code>和<code>clone()</code>方法在Java中是标准的浅拷贝方式，但它们在实际开发中不太常用。主要是因为使用<code>clone()</code>方法来拷贝一个对象即复杂又有风险，它会抛出异常，并且还需要类型转换。
+《Effective Java》 书上讲到，最好不要去使用 <code>clone()</code>，可以使用拷贝构造函数或者拷贝工厂来拷贝一个对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">CloneConstructorExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneConstructorExample</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">10</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">CloneConstructorExample</span><span class="p">(</span><span class="n">CloneConstructorExample</span><span class="w"> </span><span class="n">original</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">int</span><span class="o">[</span><span class="n">original</span><span class="p">.</span><span class="na">arr</span><span class="p">.</span><span class="na">length</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">arr</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">original</span><span class="p">.</span><span class="na">arr</span><span class="o">[</span><span class="n">i</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">set</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">arr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">get</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">arr</span><span class="o">[</span><span class="n">index</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">CloneConstructorExample e1 = new CloneConstructorExample();
+</span></span><span class="line"><span class="cl">CloneConstructorExample e2 = new CloneConstructorExample(e1);
+</span></span><span class="line"><span class="cl">e1.set(2, 222);
+</span></span><span class="line"><span class="cl">System.out.println(e2.get(2)); // 2
+</span></span></code></pre></div><h2 id="finalize">finalize</h2>
+<p><code>finalize</code>方法是Java提供的对象终止机制，允许开发人员提供对象被销毁之前的自定义处理逻辑。
+当垃圾回收器发现没有引用指向一个对象，即垃圾回收此对象之前，总会先调用这个对象的<code>finalize</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Called by the garbage collector on an object when garbage collection
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * determines that there are no more references to the object.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * A subclass overrides the {@code finalize} method to dispose of
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * system resources or to perform other cleanup.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finalize</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>文档注释大意：当GC确定不再有对对象的引用时，由垃圾收集器在对象上调用。子类重写<code>finalize</code>方法来释放系统资源或执行其他清理。</p>
+<p>简而言之，<code>finalize</code>方法是与Java中的垃圾回收器有关系。当一个对象变成一个垃圾对象的时候，如果此对象的内存被回收，那么就会调用该类中定义的<code>finalize</code>方法。
+当一个对象可被回收时，就需要执行该对象的<code>finalize</code>方法，那么就有可能在该方法中让对象重新被引用，从而实现自救。自救只能进行一次，如果回收的对象之前调用了<code>finalize</code>方法自救，后面回收时不会再调用该方法。</p>
+<p><code>finalize</code>方法允许在子类中被重写，用于在对象被回收时进行资源释放。
+通常在这个方法中进行一些资源释放和清理的工作，比如关闭文件、套接字和数据库连接等。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finalize</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 执行清理操作，比如关闭文件或释放资源</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Finalize method called&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">super</span><span class="p">.</span><span class="na">finalize</span><span class="p">();</span><span class="w"> </span><span class="c1">// 确保调用超类的 finalize 方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>尽管<code>finalize</code>可以被用来释放资源，但在实际开发中已经被认为是不可靠和过时的方式。永远不要主动调用某个对象的<code>finalize</code>方法，应该交给垃圾回收机制调用的原因：</p>
+<ul>
+<li>在调用<code>finalize</code>方法时时可能会导致对象复活；</li>
+<li><code>finalize</code>方法的执行时间是没有保障的，它完全由GC线程决定，极端情况下，若不发生GC，则<code>finalize</code>方法将没有执行机会。
+因为优先级比较低，即使主动调用该方法，也不会因此就直接进行回收；</li>
+<li>一个糟糕的<code>finalize</code>方法会严重影响GC的性能；</li>
+</ul>
+<p>如果从所有的根节点都无法访问到某个对象，说明对象己经不再使用了，一般来说，此对象需要被回收。
+但事实上，也并非是“非死不可”的，这时候它们暂时处于“缓刑”阶段。一个无法触及的对象有可能在某一个条件下“复活”自己，如果这样那么对它的回收就是不合理的，为此虚拟机中定义了的对象可能的三种状态：</p>
+<ul>
+<li>可触及的：从根节点开始，可以到达这个对象；对象存活被使用；</li>
+<li>可复活的：对象的所有引用都被释放，但是对象有可能在<code>finalize</code>中复活；对象被复活，对象在<code>finalize</code>方法中被重新使用；</li>
+<li>不可触及的：对象的<code>finalize</code>方法被调用，并且没有复活，那么就会进入不可触及状态；对象死亡、对象没有被使用；</li>
+</ul>
+<p>只有在对象不可触及时才可以被回收，不可触及的对象不可能被复活，因为<code>finalize</code>只会被调用一次。
+判定一个对象是否可回收，至少要经历两次标记过程：</p>
+<ul>
+<li>如果对象没有没有引用链，则进行第一次标记；</li>
+<li>进行筛选，判断此对象是否有必要执行<code>finalize</code>方法；
+<ol>
+<li>如果对象没有重写<code>finalize</code>方法，或者<code>finalize</code>方法已经被虚拟机调用过，则虚拟机视为“没有必要执行”，对象被判定为不可触及的。</li>
+<li>如果对象重写了<code>finalize</code>方法，且还未执行过，那么会被插入到<code>F-Queue</code>队列中，由一个虚拟机自动创建的、低优先级的<code>Finalizer</code>线程触发其<code>finalize</code>方法执行。</li>
+<li><code>finalize</code>方法是对象逃脱死亡的最后机会，稍后GC会对<code>F-Queue</code>队列中的对象进行第二次标记。如果对象在<code>finalize</code>方法中与引用链上的任何一个对象建立了联系，那么在第二次标记时，该对象会被移出“即将回收”集合。
+之后对象会再次出现没有引用存在的情况。在这个情况下，<code>finalize</code>方法不会被再次调用，对象会直接变成不可触及的状态，也就是说，一个对象的<code>finalize</code>方法只会被调用一次。</li>
+</ol>
+</li>
+</ul>
+<p>代码演示对象能否被回收：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">MainTest</span><span class="w"> </span><span class="n">var</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 此方法只能被调用一次
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 可对该方法进行注释，来测试finalize方法是否能复活对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">finalize</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;调用当前类重写的finalize()方法&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 复活对象 让当前带回收对象重新与引用链中的对象建立联系</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">new</span><span class="w"> </span><span class="n">MainTest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">gc</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;-----------------第一次gc操作------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 因为Finalizer线程的优先级比较低，暂停2秒，以等待它</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">2000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kd">var</span><span class="w"> </span><span class="err">== </span><span class="n">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;对象已经死了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="c1">// 如果第一次对象就死亡了 就终止</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;对象还活着&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;-----------------第二次gc操作------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">var</span><span class="w"> </span><span class="err">= </span><span class="n">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">gc</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 下面代码和上面代码是一样的，但是 对象却自救失败了</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">2000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="kd">var</span><span class="w"> </span><span class="err">== </span><span class="n">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;对象已经死了&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;对象还活着&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="getclass">getClass</h2>
+<p><code>getClass</code>方法是Java中的一个重要方法，它用于返回对象的运行时类。这个方法定义在<code>java.lang.Object</code>类中，因此每个Java对象都可以调用它。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Returns the runtime class of this {@code Object}. The returned
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * {@code Class} object is the object that is locked by {@code
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * static synchronized} methods of the represented class.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">native</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">getClass</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p>文档大意：返回这个对象的运行时类，返回的<code>Class</code>对象是被表示类的<code>static synchronized</code>方法锁定的对象。</p>
+<p><code>getClass</code>方法返回对象运行时的类，返回的类型是<code>Class</code>类型的对象。可以通过这个<code>Class</code>对象来创建调用这个方法的对象和执行一些其他操作，这便是反射的入口。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello, World!&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">getClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">clazz</span><span class="p">.</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;substring&#34;</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="p">)</span><span class="w"> </span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">str</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">,</span><span class="w"> </span><span class="n">12</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Result: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">result</span><span class="p">);</span><span class="w"> </span><span class="c1">// Output: World</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在某些情况下，需要比较两个对象是否属于同一类型。通过<code>getClass</code>方法可以方便地进行类型比较。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MainTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">str1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">str2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;World&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Integer</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">42</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">str1</span><span class="p">.</span><span class="na">getClass</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">str2</span><span class="p">.</span><span class="na">getClass</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;str1 and str2 are of the same type.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">str1</span><span class="p">.</span><span class="na">getClass</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">num</span><span class="p">.</span><span class="na">getClass</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;str1 and num are of different types.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="notify">notify</h2>
+<p><code>notify</code>方法用于唤醒在该对象监视器上等待的一个线程。如果有多个线程在该对象上等待，具体唤醒哪一个线程是由线程调度器决定的，并且是不确定的。
+被唤醒的线程将继续执行，从调用<code>wait</code>方法的地方开始。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">notify</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p><code>notify</code>适用于有多个线程等待一个共享资源，但每次只能一个线程进行处理的情况。
+例如，生产者-消费者模型中，当有一个生产者线程生产了一个产品，可以使用<code>notify</code>唤醒一个消费者线程来消费该产品。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">SharedResource</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Queue</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">queue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CAPACITY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">produce</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">queue</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">queue</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Produced: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notify</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒一个等待的消费者线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">consume</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">queue</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">queue</span><span class="p">.</span><span class="na">poll</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Consumed: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notify</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒一个等待的生产者线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">NotifyExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SharedResource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SharedResource</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">producer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">produce</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">consumer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">consume</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">producer</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">consumer</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="notifyall">notifyAll</h2>
+<p><code>notifyAll</code>方法用于唤醒在该对象监视器上等待的所有线程。所有被唤醒的线程将竞争对象的监视器锁，只有一个线程能成功获得锁并继续执行。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">notifyAll</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><p><code>notifyAll</code>适用于多个线程等待同一个条件，并且当条件满足时，需要所有等待的线程都重新检查条件的情况。
+例如，在某些复杂的同步场景中，当某个状态变化需要通知所有等待线程时，使用<code>notifyAll</code>可以确保所有等待的线程都被唤醒并检查新状态。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">SharedResource</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Queue</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">queue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">CAPACITY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">produce</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">queue</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">CAPACITY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">queue</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Produced: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notifyAll</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒所有等待的消费者线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">synchronized</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">consume</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">queue</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">queue</span><span class="p">.</span><span class="na">poll</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Consumed: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notifyAll</span><span class="p">();</span><span class="w"> </span><span class="c1">// 唤醒所有等待的生产者线程</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">NotifyAllExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SharedResource</span><span class="w"> </span><span class="n">resource</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SharedResource</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">producer1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">produce</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">producer2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">produce</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">consumer1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">consume</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">consumer2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">resource</span><span class="p">.</span><span class="na">consume</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">Thread</span><span class="p">.</span><span class="na">currentThread</span><span class="p">().</span><span class="na">interrupt</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">producer1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">producer2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">consumer1</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">consumer2</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="wait">wait</h2>
+<p><code>wait</code>方法使当前线程进入等待状态，同时<code>wait()</code>也会让当前线程释放它所持有的锁。
+直到其他线程调用该对象的<code>notify</code>方法或<code>notifyAll</code>方法来唤醒它，或者在指定的时间内没有被唤醒。该方法必须在同步块或同步方法中调用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">wait</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">wait</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">timeout</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">wait</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">timeout</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">nanos</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><ul>
+<li><code>wait()</code>：使当前线程无限期等待，直到被唤醒。</li>
+<li><code>wait(long timeout)</code>：使当前线程等待指定的毫秒数后自动唤醒。</li>
+<li><code>wait(long timeout, int nanos)</code>：使当前线程等待指定的时间（以毫秒和纳秒为单位）后自动唤醒。</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WaitNotifyExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="n">lock</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Object</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">waitingThread</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is waiting...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">lock</span><span class="p">.</span><span class="na">wait</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is resumed.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">InterruptedException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="w"> </span><span class="n">notifyingThread</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Thread</span><span class="p">(()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="n">lock</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Thread is notifying...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">lock</span><span class="p">.</span><span class="na">notify</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">waitingThread</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="n">1000</span><span class="p">);</span><span class="w"> </span><span class="c1">// Ensure waitingThread starts waiting</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">notifyingThread</span><span class="p">.</span><span class="na">start</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>需要注意区分<code>wait</code>方法与<code>sleep</code>方法，很多人分不清。<code>sleep</code>和<code>wait</code>方法异同点：</p>
+<ul>
+<li><code>sleep()</code>属于<code>Thread</code>类，<code>wait()</code>属于<code>Object</code>类；</li>
+<li><code>sleep()</code>和<code>wait()</code>都会抛出<code>InterruptedException</code>异常，这个异常属于<code>checkedException</code>是不可避免；</li>
+<li>两者比较的共同之处是，都是使程序等待多长时间。不同的是调用<code>sleep()</code>不会释放锁，会使线程堵塞，而调用<code>wait()</code>会释放锁，让线程进入等待状态，用 <code>notify()</code>、<code>notifyall()</code>可以唤醒，或者等待时间到了；这是因为，如果没有释放锁，那么其它线程就无法进入对象的同步方法或者同步控制块中，那么就无法执行 <code>notify()</code> 或者 <code>notifyAll()</code> 来唤醒挂起的线程，造成死锁。</li>
+<li><code>wait()</code>必须在同步<code>synchronized</code>块里使用，<code>sleep()</code>可以在任意地方使用；</li>
+</ul>
+<p>其中&quot;<code>wait()</code>必须在同步<code>synchronized</code>块里使用&quot;，不止<code>wait</code>方法，<code>notify、notifyAll</code>也和<code>wait</code>方法一样，必须在<code>synchronized</code>块里使用，为什么呢？</p>
+<p>是为了避免丢失唤醒问题。假设没有<code>synchronized</code>修饰，使用了<code>wait</code>方法而没有设置等待时间，也没有调用唤醒方法或者唤醒方法调用的时机不对，这个线程将会永远的堵塞下去。
+<code>wait</code>、<code>notify</code>、<code>notifyAll</code>方法调用的时候要释放锁，你都没给它加锁，他怎么释放锁。所以如果没在<code>synchronized</code>块中调用<code>wait()、notify、notifyAll</code>方法是肯定抛异常的。</p>
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+    
+</script>
+
+
+
+
+
+
+
+
+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/docs/posts/javabasics/rookie-operation/index.html b/docs/posts/javabasics/rookie-operation/index.html
new file mode 100644
index 00000000..479cb524
--- /dev/null
+++ b/docs/posts/javabasics/rookie-operation/index.html
@@ -0,0 +1,2682 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java运算 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="运算符与表达式 运算符 运算符指明对操作数的运算方式。组成表达式的Java操作符有很多种。 运算符按照其要求的操作数数目来分，可以有单目运算符、双目运算符和三目运算符" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
+    
+
+	
+
+    <link rel="shortcut icon" href="https://whiteppure.github.io/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%90%e7%ae%97%e7%ac%a6%e4%b8%8e%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    运算符与表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%ae%97%e6%9c%af%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    算术运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b5%8b%e5%80%bc%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    赋值运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%af%94%e8%be%83%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    比较运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e9%80%bb%e8%be%91%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    逻辑运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%bd%8d%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    位运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e4%b8%89%e7%9b%ae%e8%bf%90%e7%ae%97%e7%ac%a6">
+                    三目运算符
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#instanceof">
+                    instanceof
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%bf%90%e7%ae%97%e9%a1%ba%e5%ba%8f">
+                    运算顺序
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%ad%a3%e5%88%99%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    正则表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#lambda%e8%a1%a8%e8%be%be%e5%bc%8f">
+                    Lambda表达式
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%8e%a7%e5%88%b6%e6%b5%81%e8%af%ad%e5%8f%a5">
+                    控制流语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#if-else%e8%af%ad%e5%8f%a5">
+                    if-else语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#switch%e8%af%ad%e5%8f%a5">
+                    switch语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#for%e8%af%ad%e5%8f%a5">
+                    for语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#do-while%e5%92%8cwhile%e8%af%ad%e5%8f%a5">
+                    do-while和while语句
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%82%e6%95%b0%e4%bc%a0%e9%80%92">
+                    参数传递
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%b5%ae%e7%82%b9%e7%b1%bb%e7%b2%be%e5%ba%a6%e9%97%ae%e9%a2%98">
+                    浮点类精度问题
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#bigdecimal">
+                    BigDecimal
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%9f%ba%e6%9c%ac%e7%94%a8%e6%b3%95">
+                    基本用法
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%88%8d%e5%85%a5%e8%a7%84%e5%88%99">
+                    舍入规则
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#scale%e5%b1%9e%e6%80%a7">
+                    scale属性
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%af%94%e8%be%83%e5%a4%a7%e5%b0%8f">
+                    比较大小
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#math">
+                    Math
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#ceil%e5%92%8cfloor">
+                    ceil和floor
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#random">
+                    random
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#round">
+                    round
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
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+    <div class="main animate__animated animate__fadeInDown" id="main_content">
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+                <a href="https://whiteppure.github.io/iblog/about/">关于</a>
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+        <div class="site_title">
+            <h1>
+                <a href="https://whiteppure.github.io/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
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+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
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+                    <i class="ri-rss-fill"></i>
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+                
+                
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+                        <h2 id="post_single_title">Java运算</h2>
+                        <span id="post_page_title_date" class="date">2021.01.30</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
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+                    <div class="post_content markdown"><h2 id="运算符与表达式">运算符与表达式</h2>
+<h3 id="运算符">运算符</h3>
+<p>运算符指明对操作数的运算方式。组成表达式的Java操作符有很多种。
+运算符按照其要求的操作数数目来分，可以有单目运算符、双目运算符和三目运算符，它们分别对应于1个、2个、3个操作数。
+按其功能来分，可以有算术运算符、赋值运算符、比较(关系)运算符、逻辑运算符、位运算符和其他运算符。</p>
+<h4 id="算术运算符">算术运算符</h4>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>备注</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>+</td>
+<td>加法</td>
+<td>相加运算符两侧的值</td>
+<td></td>
+<td><code>int sum = 5 + 3;</code></td>
+</tr>
+<tr>
+<td>-</td>
+<td>减法</td>
+<td>左操作数减去右操作数</td>
+<td></td>
+<td><code>int difference = 5 - 3;</code></td>
+</tr>
+<tr>
+<td>*</td>
+<td>乘法</td>
+<td>相乘操作符两侧的值</td>
+<td></td>
+<td><code>int product = 5 * 3;</code></td>
+</tr>
+<tr>
+<td>/</td>
+<td>除法</td>
+<td>左操作数除以右操作数</td>
+<td>右操作数不能为0</td>
+<td><code>int quotient = 10 / 2;</code></td>
+</tr>
+<tr>
+<td>%</td>
+<td>取余</td>
+<td>左操作数除以右操作数的余数</td>
+<td></td>
+<td><code>int remainder = 10 % 3;</code></td>
+</tr>
+<tr>
+<td>++</td>
+<td>自增</td>
+<td>操作数的值增加1</td>
+<td></td>
+<td><code>int a = 5; a++;</code></td>
+</tr>
+<tr>
+<td>&ndash;</td>
+<td>自减</td>
+<td>操作数的值减少1</td>
+<td></td>
+<td><code>int a = 5; a--;</code></td>
+</tr>
+</tbody>
+</table>
+<p>关于取余，如果被取余的数小于取余的数，那取余的结果就是被除数，例如，<code>4%5=4</code>、<code>3%5=3</code>；
+如果被取余的数等于取余的数，结果是0，例如，<code>5%5=0</code>；
+如果取余数是1，结果是0，例如，<code>9%1=0</code>。</p>
+<p>当使用随机数生成器产生的结果时，取余运算可将结果限制在上限为操作数最大值减1的范围。
+例如：n是随机数，那么<code>n%10</code>就是<code>0~9</code>中的一个数。无论n是多大的数，<code>n%10</code>只能是<code>0~9</code>之间的一个数，利用这一特性，可以应用在数据库分库、分表等。</p>
+<p>对于自增和自减，需要特别留意的是<code>++</code>和<code>--</code>运算符可以前置、后置，都是合法的语句，如<code>a++</code>和<code>++a</code>都是合法的，上面这两种写法其最终的结果都是是变量a的值加1了，但是它们之间也是有区别的。
+其区别是：表达是<code>++a</code>会先将a的值自增1，然后在使用变量a，而表达式<code>a++</code>是先使用了a的值，然后再让a的值自增1。也就是说在一些表达式，使用<code>a++</code>和使用<code>++a</code>得到的结果时不一样的，例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">i</span><span class="o">++</span><span class="p">);</span><span class="c1">// 1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="o">++</span><span class="n">i</span><span class="p">);</span><span class="c1">// 3</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>++</code>和<code>--</code>两个运算符只能作用于变量，而不能作用于表达式，例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 编译报错</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">((</span><span class="n">j</span><span class="o">+</span><span class="n">i</span><span class="p">)</span><span class="o">++</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="赋值运算符">赋值运算符</h4>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>=</td>
+<td>赋值</td>
+<td>将右操作数的值赋给左侧操作数</td>
+<td><code>int a = 5;</code></td>
+</tr>
+<tr>
+<td>+=</td>
+<td>加等于</td>
+<td>把左操作数和右操作数相加赋值给左操作数</td>
+<td><code>int b = 3; b += 2;</code></td>
+</tr>
+<tr>
+<td>-=</td>
+<td>减等于</td>
+<td>把左操作数和右操作数相减赋值给左操作数</td>
+<td><code>int c = 7; c -= 4;</code></td>
+</tr>
+<tr>
+<td>*=</td>
+<td>乘等于</td>
+<td>把左操作数和右操作数相乘赋值给左操作数</td>
+<td><code>int d = 2; d *= 3;</code></td>
+</tr>
+<tr>
+<td>/=</td>
+<td>除等于</td>
+<td>把左操作数和右操作数相除赋值给左操作数</td>
+<td><code>int e = 10; e /= 2;</code></td>
+</tr>
+<tr>
+<td>%=</td>
+<td>模等于</td>
+<td>把左操作数和右操作数取模后赋值给左操作数</td>
+<td><code>int f = 10; f %= 3;</code></td>
+</tr>
+<tr>
+<td>&laquo;=</td>
+<td>左位移等于</td>
+<td>把左操作数和右操作数进行左移运算后赋值给左操作数</td>
+<td><code>int g = 8; g &lt;&lt;= 2;</code></td>
+</tr>
+<tr>
+<td>&raquo;=</td>
+<td>右位移等于</td>
+<td>把左操作数和右操作数进行右移运算后赋值给左操作数</td>
+<td><code>int h = 16; h &gt;&gt;= 2;</code></td>
+</tr>
+<tr>
+<td>&amp;=</td>
+<td>按位与等于</td>
+<td>把左操作数和右操作数进行按位与运算后赋值给左操作数</td>
+<td><code>int i = 5; i &amp;= 3;</code></td>
+</tr>
+<tr>
+<td>|=</td>
+<td>按位或等于</td>
+<td>把左操作数和右操作数进行按位或运算后赋值给左操作数</td>
+<td><code>int j = 5; j &amp;#124;= 3;</code></td>
+</tr>
+<tr>
+<td>^=</td>
+<td>异或等于</td>
+<td>把左操作数和右操作数进行按位异或运算后赋值给左操作数</td>
+<td><code>int k = 5; k ^= 3;</code></td>
+</tr>
+</tbody>
+</table>
+<p>在进行复合赋值运算时，Java会自动进行类型转换。
+例如，如果左操作数是一个较小的数据类型，而右操作数是一个较大的数据类型，则右操作数会被自动转换为左操作数的类型，然后进行运算。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">byte</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">a</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w"> </span><span class="c1">// 合法，等同于 a = (byte)(a + 5);</span><span class="w">
+</span></span></span></code></pre></div><p>复合赋值运算符是原子操作，即它们是一个完整的、不可分割的操作，不会被中断或其他线程干扰。
+对于数值型数据，特别是整数类型，需要注意复合赋值运算符可能导致的溢出问题。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">byte</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">127</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">b</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// b 现在是 -128，发生了溢出</span><span class="w">
+</span></span></span></code></pre></div><h4 id="比较运算符">比较运算符</h4>
+<p>比较运算符也称为关系运算符，用于展示两个操作数之间的关系。
+使用比较运算符表达式的最终结果为<code>boolean</code>型，也就是其结果只有两个<code>true</code>和<code>false</code>。</p>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>==</td>
+<td>双等号</td>
+<td>检查两个操作数的值是否相等</td>
+<td><code>boolean isEqual = (5 == 5);</code></td>
+</tr>
+<tr>
+<td>!=</td>
+<td>不等号</td>
+<td>检查两个操作数的值是否不相等</td>
+<td><code>boolean notEqual = (5 != 3);</code></td>
+</tr>
+<tr>
+<td>&gt;</td>
+<td>大于</td>
+<td>检查左操作数的值是否大于右操作数</td>
+<td><code>boolean greaterThan = (5 &gt; 3);</code></td>
+</tr>
+<tr>
+<td>&lt;</td>
+<td>小于</td>
+<td>检查左操作数的值是否小于右操作数</td>
+<td><code>boolean lessThan = (5 &lt; 3);</code></td>
+</tr>
+<tr>
+<td>&gt;=</td>
+<td>大于等于</td>
+<td>检查左操作数的值是否大于或等于右操作数</td>
+<td><code>boolean greaterOrEqual = (5 &gt;= 5);</code></td>
+</tr>
+<tr>
+<td>&lt;=</td>
+<td>小于等于</td>
+<td>检查左操作数的值是否小于或等于右操作数</td>
+<td><code>boolean lessOrEqual = (5 &lt;= 5);</code></td>
+</tr>
+</tbody>
+</table>
+<h4 id="逻辑运算符">逻辑运算符</h4>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>&amp;&amp;</td>
+<td>逻辑与</td>
+<td>当且仅当两个操作数都为真时，条件为真</td>
+<td><code>boolean result = (true &amp;&amp; false);</code></td>
+</tr>
+<tr>
+<td>||</td>
+<td>逻辑或</td>
+<td>如果两个操作数任何一个为真时，条件为真</td>
+<td><code>boolean result = (true || false);</code></td>
+</tr>
+<tr>
+<td>!</td>
+<td>逻辑非</td>
+<td>用来反转操作数的逻辑状态，条件取反</td>
+<td><code>boolean result = !true;</code></td>
+</tr>
+</tbody>
+</table>
+<p><code>&amp;&amp;</code>运算符，运算顺序是从左到右计算，运算规则是如果两个操作数都是真，则返回<code>true</code>，否则返回<code>false</code>。
+但是当判定到第一个操作数为<code>false</code>时，其结果必定为<code>false</code>，这时候就不再会判定第二个操作数了。
+这种特性可以在复杂条件语句中提高效率，并可以避免不必要的计算。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">flag</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">++</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">2</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="o">++</span><span class="n">j</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// flag的值: false,i的值:2,j的值:2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;flag的值: %s,i的值:%s,j的值:%s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">flag</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在使用逻辑运算符时，特别是在复杂的条件逻辑中，尽量保证逻辑表达式的意图清晰，建议使用括号明确运算顺序。</p>
+<h4 id="位运算符">位运算符</h4>
+<p>位运算符在追求代码效率和编写底层应用时，使用的比较多，在企业Java开发一般用到的较少。</p>
+<table>
+<thead>
+<tr>
+<th>运算符</th>
+<th>名称</th>
+<th>用法描述</th>
+<th>示例</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>&amp;</td>
+<td>按位与</td>
+<td>如果相对应位都是1，则结果为1，否则为0</td>
+<td><code>int result = 5 &amp; 3;</code></td>
+</tr>
+<tr>
+<td>|</td>
+<td>按位或</td>
+<td>如果相对应位都是0，则结果为0，否则为1</td>
+<td><code>int result = 5 | 3;</code></td>
+</tr>
+<tr>
+<td>^</td>
+<td>按位异或</td>
+<td>如果相对应位值相同，则结果为0，否则为1</td>
+<td><code>int result = 5 ^ 3;</code></td>
+</tr>
+<tr>
+<td>~</td>
+<td>按位取反</td>
+<td>翻转操作数的每一位，即0变成1，1变成0</td>
+<td><code>int result = ~5;</code></td>
+</tr>
+<tr>
+<td>&laquo;</td>
+<td>左移</td>
+<td>左操作数按位左移右操作数指定的位数</td>
+<td><code>int result = 5 &lt;&lt; 2;</code></td>
+</tr>
+<tr>
+<td>&raquo;</td>
+<td>右移</td>
+<td>左操作数按位右移右操作数指定的位数</td>
+<td><code>int result = 5 &gt;&gt; 2;</code></td>
+</tr>
+<tr>
+<td>&raquo;&gt;</td>
+<td>无符号右移</td>
+<td>左操作数的值按右操作数指定的位数右移，移动得到的空位以零填充</td>
+<td><code>int result = 5 &gt;&gt;&gt; 2;</code></td>
+</tr>
+</tbody>
+</table>
+<p>一些小技巧：</p>
+<ul>
+<li><code>&gt;&gt;</code>：右移几位就是相当于除以2的几次幂；</li>
+<li><code>&lt;&lt;</code>：左移几位就是相当于乘以2的几次幂；</li>
+<li><code>%</code>：当b为2的n次方时，有如下替换公式：<code>a % b = a &amp; (b-1)</code>；</li>
+</ul>
+<p>位运算符只能对整数型(<code>int</code>、<code>long</code>、<code>short</code>、<code>byte</code>)和字符型数据(<code>char</code>)进行操作。
+因为位运算符是以<code>bit</code>运算单位的，所以想要弄明白位运算符，就要先弄明白二进制的表示方法。</p>
+<p>以下示例用十进制的1和2进行运算，1用二进制表示为<code>0000 0001</code>，2用二进制表示为<code>0000 0010</code>，为了更好的理解位运算，下面我会详细解析：</p>
+<ul>
+<li><code>&amp;</code>：如果相对应位都是1，则结果为1，否则为0；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">0000 0010
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0000
+</span></span></code></pre></div></li>
+<li><code>|</code>：如果相对应位都是 0，则结果为 0，否则为 1；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">0000 0010
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0011
+</span></span></code></pre></div></li>
+<li><code>^</code>：如果相对应位值相同，则结果为0，否则为1；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">0000 0010
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0011
+</span></span></code></pre></div></li>
+<li><code>~</code>：翻转操作数的每一位，即0变成1，1变成0；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0011
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">1111 1100
+</span></span></code></pre></div></li>
+<li><code>&lt;&lt;</code>：左操作数按位左移右操作数指定的位数，如1左移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0100
+</span></span></code></pre></div></li>
+<li><code>&gt;&gt;</code>：左操作数按位右移右操作数指定的位数；（正数右移高位补0，负数右移高位补1）
+1右移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0000
+</span></span></code></pre></div>负一右移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">1111 1111
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">1111 1111
+</span></span></code></pre></div></li>
+<li><code>&gt;&gt;&gt;</code>：左操作数的值按右操作数指定的位数右移，移动得到的空位以零填充；（无符号右移，无论是正数还是负数，高位通通补0）
+1无符号右移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0000 0001
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0000 0000
+</span></span></code></pre></div>负一无符号右移两位：
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">1111 1111
+</span></span><span class="line"><span class="cl">——————————
+</span></span><span class="line"><span class="cl">0011 1111
+</span></span></code></pre></div></li>
+</ul>
+<h4 id="三目运算符">三目运算符</h4>
+<p>该运算符有3个操作数，其功能是对表达式条件进行判断，根据判断结果是<code>true</code>或者<code>false</code>两种情况赋予赋予不同的返回值。</p>
+<p>该运算符的主要是决定哪个值应该赋值给变量。在某些情况下，可以发现三目运算符和<code>if...else</code>作用是相同的，可以完全替代<code>if...else</code>。
+三目运算符可以使代码更加简洁和可读，特别是在简单的条件赋值或返回语句中，但应该尽量避免过多的嵌套三目运算符，以免降低代码的可读性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">?</span><span class="w">  </span><span class="n">1</span><span class="p">:</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 等价于if...else以下代码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">var2</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那么三目运算符与<code>if...else</code>到底哪有啥不同？要探究这个原因，需要看JVM是对三目运算符怎么处理的。
+用<code>javap -verbose</code>命令，分别把<code>if...else</code>和三目运算符相关代码进行反编译：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 如果var2大于1 则var1等于1 否则等于2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">?</span><span class="w">  </span><span class="n">1</span><span class="p">:</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl">  <span class="o">//</span> <span class="o">...</span>
+</span></span><span class="line"><span class="cl"><span class="p">{</span>
+</span></span><span class="line"><span class="cl"> <span class="o">//</span> <span class="o">...</span>
+</span></span><span class="line"><span class="cl">  <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="n">java</span><span class="o">.</span><span class="n">lang</span><span class="o">.</span><span class="n">String</span><span class="p">[]);</span>
+</span></span><span class="line"><span class="cl">    <span class="n">descriptor</span><span class="p">:</span> <span class="p">([</span><span class="n">Ljava</span><span class="o">/</span><span class="n">lang</span><span class="o">/</span><span class="ne">String</span><span class="p">;)</span><span class="n">V</span>
+</span></span><span class="line"><span class="cl">    <span class="n">flags</span><span class="p">:</span> <span class="n">ACC_PUBLIC</span><span class="p">,</span> <span class="n">ACC_STATIC</span>
+</span></span><span class="line"><span class="cl">    <span class="n">Code</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">      <span class="n">stack</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">locals</span><span class="o">=</span><span class="mi">3</span><span class="p">,</span> <span class="n">args_size</span><span class="o">=</span><span class="mi">1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">0</span><span class="p">:</span> <span class="n">iconst_1</span> <span class="o">//</span> <span class="err">向栈里添加</span><span class="n">int类型</span> <span class="mi">1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">1</span><span class="p">:</span> <span class="n">istore_1</span> <span class="o">//</span> <span class="err">将</span><span class="ne">int</span> <span class="mi">1</span> <span class="err">存储到局部变量</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">2</span><span class="p">:</span> <span class="n">iconst_0</span> <span class="o">//</span> <span class="err">向栈里添加</span><span class="n">int类型</span> <span class="mi">0</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">3</span><span class="p">:</span> <span class="n">istore_2</span> <span class="o">//</span> <span class="err">将</span><span class="ne">int</span> <span class="mi">2</span> <span class="err">存储到局部变量</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">4</span><span class="p">:</span> <span class="n">iload_2</span>  <span class="o">//</span> <span class="err">从局部变量加载</span><span class="ne">int</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">5</span><span class="p">:</span> <span class="n">iconst_1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">6</span><span class="p">:</span> <span class="n">if_icmple</span>     <span class="mi">13</span>  <span class="o">//</span> <span class="err">将</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="err">步骤栈中的变量弹出</span> <span class="err">进行比较</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">9</span><span class="p">:</span> <span class="n">iconst_1</span> <span class="o">//</span> <span class="err">比较成功</span> <span class="err">存储该值到栈中</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">10</span><span class="p">:</span> <span class="n">goto</span>          <span class="mi">14</span> <span class="o">//</span> <span class="err">改变地址</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">13</span><span class="p">:</span> <span class="n">iconst_2</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">14</span><span class="p">:</span> <span class="n">istore_1</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">15</span><span class="p">:</span> <span class="k">return</span>
+</span></span><span class="line"><span class="cl">      <span class="n">LineNumberTable</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">6</span><span class="p">:</span> <span class="mi">0</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">7</span><span class="p">:</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">8</span><span class="p">:</span> <span class="mi">4</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">9</span><span class="p">:</span> <span class="mi">15</span>
+</span></span><span class="line"><span class="cl">      <span class="n">LocalVariableTable</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Start</span>  <span class="n">Length</span>  <span class="n">Slot</span>  <span class="n">Name</span>   <span class="n">Signature</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">0</span>      <span class="mi">16</span>     <span class="mi">0</span>  <span class="n">args</span>   <span class="p">[</span><span class="n">Ljava</span><span class="o">/</span><span class="n">lang</span><span class="o">/</span><span class="ne">String</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">2</span>      <span class="mi">14</span>     <span class="mi">1</span>  <span class="n">var1</span>   <span class="n">I</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">4</span>      <span class="mi">12</span>     <span class="mi">2</span>  <span class="n">var2</span>   <span class="n">I</span>
+</span></span><span class="line"><span class="cl">      <span class="n">StackMapTable</span><span class="p">:</span> <span class="n">number_of_entries</span> <span class="o">=</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">        <span class="n">frame_type</span> <span class="o">=</span> <span class="mi">253</span> <span class="o">/*</span> <span class="n">append</span> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">          <span class="n">offset_delta</span> <span class="o">=</span> <span class="mi">13</span>
+</span></span><span class="line"><span class="cl">          <span class="n">locals</span> <span class="o">=</span> <span class="p">[</span> <span class="ne">int</span><span class="p">,</span> <span class="ne">int</span> <span class="p">]</span>
+</span></span><span class="line"><span class="cl">        <span class="n">frame_type</span> <span class="o">=</span> <span class="mi">64</span> <span class="o">/*</span> <span class="n">same_locals_1_stack_item</span> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">          <span class="n">stack</span> <span class="o">=</span> <span class="p">[</span> <span class="ne">int</span> <span class="p">]</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="o">//</span> <span class="o">...</span>
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="kt">int</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="kt">int</span><span class="w"> </span><span class="n">var2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">var2</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gdscript3" data-lang="gdscript3"><span class="line"><span class="cl">  <span class="o">//</span> <span class="o">...</span>
+</span></span><span class="line"><span class="cl">  <span class="n">public</span> <span class="k">static</span> <span class="n">void</span> <span class="n">main</span><span class="p">(</span><span class="n">java</span><span class="o">.</span><span class="n">lang</span><span class="o">.</span><span class="n">String</span><span class="p">[]);</span>
+</span></span><span class="line"><span class="cl">    <span class="n">descriptor</span><span class="p">:</span> <span class="p">([</span><span class="n">Ljava</span><span class="o">/</span><span class="n">lang</span><span class="o">/</span><span class="ne">String</span><span class="p">;)</span><span class="n">V</span>
+</span></span><span class="line"><span class="cl">    <span class="n">flags</span><span class="p">:</span> <span class="n">ACC_PUBLIC</span><span class="p">,</span> <span class="n">ACC_STATIC</span>
+</span></span><span class="line"><span class="cl">    <span class="n">Code</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">      <span class="n">stack</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">locals</span><span class="o">=</span><span class="mi">3</span><span class="p">,</span> <span class="n">args_size</span><span class="o">=</span><span class="mi">1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">0</span><span class="p">:</span> <span class="n">iconst_1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">1</span><span class="p">:</span> <span class="n">istore_1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">2</span><span class="p">:</span> <span class="n">iconst_0</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">3</span><span class="p">:</span> <span class="n">istore_2</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">4</span><span class="p">:</span> <span class="n">iload_2</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">5</span><span class="p">:</span> <span class="n">iconst_1</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">6</span><span class="p">:</span> <span class="n">if_icmple</span>     <span class="mi">14</span>
+</span></span><span class="line"><span class="cl">         <span class="mi">9</span><span class="p">:</span> <span class="n">iconst_1</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">10</span><span class="p">:</span> <span class="n">istore_1</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">11</span><span class="p">:</span> <span class="n">goto</span>          <span class="mi">16</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">14</span><span class="p">:</span> <span class="n">iconst_2</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">15</span><span class="p">:</span> <span class="n">istore_1</span>
+</span></span><span class="line"><span class="cl">        <span class="mi">16</span><span class="p">:</span> <span class="k">return</span>
+</span></span><span class="line"><span class="cl">      <span class="n">LineNumberTable</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">6</span><span class="p">:</span> <span class="mi">0</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">7</span><span class="p">:</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">8</span><span class="p">:</span> <span class="mi">4</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">9</span><span class="p">:</span> <span class="mi">9</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">11</span><span class="p">:</span> <span class="mi">14</span>
+</span></span><span class="line"><span class="cl">        <span class="n">line</span> <span class="mi">13</span><span class="p">:</span> <span class="mi">16</span>
+</span></span><span class="line"><span class="cl">      <span class="n">LocalVariableTable</span><span class="p">:</span>
+</span></span><span class="line"><span class="cl">        <span class="n">Start</span>  <span class="n">Length</span>  <span class="n">Slot</span>  <span class="n">Name</span>   <span class="n">Signature</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">0</span>      <span class="mi">17</span>     <span class="mi">0</span>  <span class="n">args</span>   <span class="p">[</span><span class="n">Ljava</span><span class="o">/</span><span class="n">lang</span><span class="o">/</span><span class="ne">String</span><span class="p">;</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">2</span>      <span class="mi">15</span>     <span class="mi">1</span>  <span class="n">var1</span>   <span class="n">I</span>
+</span></span><span class="line"><span class="cl">            <span class="mi">4</span>      <span class="mi">13</span>     <span class="mi">2</span>  <span class="n">var2</span>   <span class="n">I</span>
+</span></span><span class="line"><span class="cl">      <span class="n">StackMapTable</span><span class="p">:</span> <span class="n">number_of_entries</span> <span class="o">=</span> <span class="mi">2</span>
+</span></span><span class="line"><span class="cl">        <span class="n">frame_type</span> <span class="o">=</span> <span class="mi">253</span> <span class="o">/*</span> <span class="n">append</span> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl">          <span class="n">offset_delta</span> <span class="o">=</span> <span class="mi">14</span>
+</span></span><span class="line"><span class="cl">          <span class="n">locals</span> <span class="o">=</span> <span class="p">[</span> <span class="ne">int</span><span class="p">,</span> <span class="ne">int</span> <span class="p">]</span>
+</span></span><span class="line"><span class="cl">        <span class="n">frame_type</span> <span class="o">=</span> <span class="mi">1</span> <span class="o">/*</span> <span class="n">same</span> <span class="o">*/</span>
+</span></span><span class="line"><span class="cl"><span class="p">}</span>
+</span></span><span class="line"><span class="cl"><span class="o">//</span> <span class="o">...</span>
+</span></span></code></pre></div><p>通过查阅<a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-6.html">《Java虚拟机指令集》</a>，在参照上面反编译的字节码反编译的内容，可以看到JVM对上边的代码进行了什么处理。
+通过比较两次反编译后的代码可以得出一个结论，即三目运算符与<code>if..else</code>执行的命令几乎没有差异。
+但是对于实际开发来说三目运算符的可读性相对不如<code>if...else</code>代码，所以在常见的编码中，三目运算符更倾向于简单的<code>if...else</code>语句的替代。</p>
+<h4 id="instanceof">instanceof</h4>
+<p><code>instanceof</code>是一个双目运算符，该关键字的作用是判断左边的对象是不是右边类的实例，并返回一个<code>boolean</code>值。
+<code>instanceof</code>可以用来检查对象的类型，包括检查对象是否是其直接类的实例或者其父类的实例，或实现了某个接口。
+在实际开发中经常用于在运行时动态确定对象的类型，从而决定如何处理对象或执行特定的逻辑。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Animal</span><span class="w"> </span><span class="n">animal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断 animal 是否是 Animal 类的实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isAnimal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">animal</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Animal</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Is animal an instance of Animal? &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">isAnimal</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出：true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断 animal 是否是 Dog 类的实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isDog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">animal</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Dog</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Is animal an instance of Dog? &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">isDog</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出：true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 判断 animal 是否是 Object 类的实例</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isObject</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">animal</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">Object</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Is animal an instance of Object? &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">isObject</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出：true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="运算顺序">运算顺序</h4>
+<p>Java语言中运算符的优先级共分为14级，其中1级最高，14级最低，在同一个表达式中运算符优先级高的先执行。
+Java中大部分运算符也是从左向右结合的，只有单目运算符、赋值运算符、三目运算符例外，是从右向左运算的。</p>
+<table>
+<thead>
+<tr>
+<th style="text-align:center">优先级</th>
+<th>运算符</th>
+<th style="text-align:center">结合性</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td style="text-align:center">1</td>
+<td>()、[]</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">2</td>
+<td>!、+、-、~、++、&ndash;</td>
+<td style="text-align:center">从右向左</td>
+</tr>
+<tr>
+<td style="text-align:center">3</td>
+<td>*、/、%</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">4</td>
+<td>+、-</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">5</td>
+<td>«、»、&raquo;&gt;</td>
+<td style="text-align:center">从左向</td>
+</tr>
+<tr>
+<td style="text-align:center">6</td>
+<td>&lt;、&lt;=、&gt;、&gt;=、instanceof</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">7</td>
+<td>==、!=</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">8</td>
+<td>&amp;</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">10</td>
+<td>|</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">11</td>
+<td>&amp;&amp;</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">12</td>
+<td>||</td>
+<td style="text-align:center">从左向右</td>
+</tr>
+<tr>
+<td style="text-align:center">13</td>
+<td>?:</td>
+<td style="text-align:center">从右向左</td>
+</tr>
+<tr>
+<td style="text-align:center">14</td>
+<td>=、+=、-=、*=、/=、&amp;=、|=、^=、~=、&laquo;=、&raquo;=、&raquo;&gt;=</td>
+<td style="text-align:center">从右向左</td>
+</tr>
+</tbody>
+</table>
+<p>在实际开发中，不要把一个表达式写得过于复杂。如果一个表达式过于复杂，则会影响代码可读性，建议把它分成几步来完成。
+不要过多地依赖运算符的优先级来控制表达式的执行顺序，这样可读性太差，尽量使用小括号来控制表达式的执行顺序，这样能提高代码的可读性和减少歧义。</p>
+<h3 id="表达式">表达式</h3>
+<p>在Java中表达式通常是以分号结尾的一段代码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">int</span><span class="w"> </span><span class="n">sum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">c</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">length</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">boolean</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">y</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">a</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div><p>表达式是由运算符和运算对象组成的，表达式可以定义为一组变量、常量、运算符等符号的组合，其结构形成一个计算值的过程，换句话说，表达式是用来计算值的一种编程结构。
+变量的赋值与计算都离不开表达式，表达式的运算依赖于变量、常量和运算符。</p>
+<h4 id="正则表达式">正则表达式</h4>
+<p>正则表达式，又称规则表达式，英语：<code>Regular Expression</code>，在代码中常简写为<code>regex</code>、<code>regexp</code>或<code>RE</code>。
+正则表达式通常被用来检索、替换那些符合某个模式(规则)的文本，在众多语言中都可以支持正则表达式，如<code>Perl</code>、<code>PHP</code>、<code>Java</code>、<code>Python</code>、<code>Ruby</code>等。</p>
+<p>正则表达式并不仅限于某一种语言，但是在每种语言中有细微的差别。
+例如：在其他语言中，<code>\\</code> 表示，在正则表达式中插入一个普通的（字面上的）反斜杠。在Java中，<code>\\</code> 表示，插入一个正则表达式的反斜线，所以其后的字符具有特殊的意义。
+所以，在其他的语言中，一个反斜杠<code>\</code>就足以具有转义的作用，而在Java中正则表达式中则需要有两个反斜杠才能被解析为其他语言中的转义作用。
+也可以简单的理解在Java的正则表达式中，两个 <code>\\</code> 代表其他语言中的一个<code>\</code>，这也就是为什么表示一位数字的正则表达式是 <code>\\d</code>，而表示一个普通的反斜杠是 <code>\\\\</code>。</p>
+<p>正则表达式是由普通字符（如英文字母）以及特殊字符（也称为元字符）组成的文字模式，例如：<code>String str = &quot;abc^123/?[1,2]&quot;;</code>。
+在Java中主要是使用正则表达式处理字符串，Java从jdk1.4开始提供了一个包<code>java.util.regex</code>来处理正则表达式。
+主要使用<code>java.util.regex</code>包中<code>Pattern</code>类，<code>Matcher</code>类来处理字符串，使用正则表达式示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 表示匹配以字母a为开头的单词</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">regx</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;\\ba\\w*\\b&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 将给定的正则表达式编译到具有给定标志的模式中</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Pattern</span><span class="w"> </span><span class="n">pattern</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern</span><span class="p">.</span><span class="na">compile</span><span class="p">(</span><span class="n">regx</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 创建匹配给定输入与此模式的匹配器</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Matcher</span><span class="w"> </span><span class="n">matcher</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pattern</span><span class="p">.</span><span class="na">matcher</span><span class="p">(</span><span class="s">&#34;abcdab cccabcd aaacd&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 循环 查找与上边正则匹配的字符序列</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">matcher</span><span class="p">.</span><span class="na">find</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 返回 由以前匹配操作 所匹配的 输入子序列</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">matcher</span><span class="p">.</span><span class="na">group</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;:&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">res</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">index</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>总的来说，正则表达式是对字符串操作的一种逻辑公式，用事先定义好的一些特定字符、及这些特定字符的组合，组成一个&quot;规则字符串&quot;，这个&quot;规则字符串&quot;用来表达对字符串的一种过滤逻辑。
+正则表达式的灵活性、逻辑性和功能性非常的强，可以迅速地用极简单的方式达到字符串的复杂控制，但是对于刚接触的人来说比较晦涩难懂。以下是常用正则表达式：</p>
+<table>
+<thead>
+<tr>
+<th>描述</th>
+<th>正则表达式</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>是否为数字</td>
+<td><code>^[0-9]*$</code></td>
+</tr>
+<tr>
+<td>是否为n位数数字</td>
+<td><code>^\d{n}$</code></td>
+</tr>
+<tr>
+<td>是否为m-n位的数字</td>
+<td><code>^\d{m,n}$</code></td>
+</tr>
+<tr>
+<td>是否输入至少n位的数字</td>
+<td><code>^\d{n,}$</code></td>
+</tr>
+<tr>
+<td>是否为整数</td>
+<td><code>^-?\d+$</code></td>
+</tr>
+<tr>
+<td>是否为负整数</td>
+<td><code>^-[0-9]*[1-9][0-9]*$</code></td>
+</tr>
+<tr>
+<td>是否为正整数</td>
+<td><code>^[0-9]*[1-9][0-9]*$</code></td>
+</tr>
+<tr>
+<td>是否为汉字</td>
+<td><code>^[\u4e00-\u9fa5]{0,}$</code></td>
+</tr>
+<tr>
+<td>是否为邮箱</td>
+<td><code>^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$</code></td>
+</tr>
+<tr>
+<td>是否为域名</td>
+<td><code>[a-zA-Z0-9][-a-zA-Z0-9]{0,62}(\.[a-zA-Z0-9][-a-zA-Z0-9]{0,62})+\.?</code></td>
+</tr>
+<tr>
+<td>是否为URL</td>
+<td><code>^http://([\w-]+\.)+[\w-]+(/[\w-./?%&amp;=]*)?$</code></td>
+</tr>
+<tr>
+<td>是否为手机号码</td>
+<td>`^(13[0-9]</td>
+</tr>
+<tr>
+<td>是否为固话号码</td>
+<td>`^($$\d{3,4}-)</td>
+</tr>
+<tr>
+<td>是否为身份证号码</td>
+<td>`^(\d{15}</td>
+</tr>
+<tr>
+<td>是否为日期（YYYY-MM-DD）</td>
+<td><code>^\d{4}-\d{2}-\d{2}$</code></td>
+</tr>
+<tr>
+<td>是否为时间（HH:MM:SS）</td>
+<td><code>^\d{2}:\d{2}:\d{2}$</code></td>
+</tr>
+<tr>
+<td>是否为十六进制颜色码</td>
+<td>`^#?([a-fA-F0-9]{6}</td>
+</tr>
+<tr>
+<td>是否包含HTML标签</td>
+<td>`&lt;(&quot;[^&quot;]*&quot;</td>
+</tr>
+<tr>
+<td>是否为金额（带小数点的数字）</td>
+<td><code>^\d+(\.\d{1,2})?$</code></td>
+</tr>
+<tr>
+<td>是否为UUID</td>
+<td><code>^[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}$</code></td>
+</tr>
+</tbody>
+</table>
+<h4 id="lambda表达式">Lambda表达式</h4>
+<p><code>Lambda</code>表达式是Java 8引入的一项重要功能，用于简化实现接口中单个抽象方法的类的写法，使代码更加简洁和易读。
+<code>Lambda</code>表达式可以看作是匿名函数，可以在没有声明其所属类的情况下创建函数对象。</p>
+<p><code>Lambda</code>表达式的基本语法如下：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Consumer</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">consumer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><ul>
+<li>参数列表：<code>(s)</code>为参数，类似于方法的参数；</li>
+<li>箭头符号：<code>-&gt;</code>，用于分隔参数和方法体；</li>
+<li>方法体：<code>System.out.println(s)</code>为方法体，方法体可以是一个表达式或一个代码块；</li>
+</ul>
+<p><code>Lambda</code>表达式通常用于替代匿名类：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 使用匿名类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Comparator</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">comparator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Comparator</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">compare</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s1</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">s2</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用Lambda表达式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Comparator</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">comparatorLambda</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">s1</span><span class="p">,</span><span class="w"> </span><span class="n">s2</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">s2</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p><code>Lambda</code>在开发中最常用的就是集合中<code>Stream</code>流，举例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="s">&#34;a&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;b&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;c&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用forEach方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">list</span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">item</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">item</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用stream API进行过滤和排序</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filteredList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">stream</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="p">.</span><span class="na">filter</span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">startsWith</span><span class="p">(</span><span class="s">&#34;a&#34;</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="p">.</span><span class="na">sorted</span><span class="p">((</span><span class="n">s1</span><span class="p">,</span><span class="w"> </span><span class="n">s2</span><span class="p">)</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s1</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">s2</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="p">.</span><span class="na">collect</span><span class="p">(</span><span class="n">Collectors</span><span class="p">.</span><span class="na">toList</span><span class="p">());</span><span class="w">
+</span></span></span></code></pre></div><p>Java 8引入了许多函数式接口，这些接口在<code>java.util.function</code>包中定义，常用的函数式接口包括：</p>
+<ul>
+<li><code>Consumer&lt;T&gt;</code>：<code>Consumer</code>接口表示接受一个输入参数并且不返回结果的操作，它通常用于对单个参数执行某种操作；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">void</span><span class="w"> </span><span class="nf">accept</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ConsumerExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Consumer</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">printer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">printer</span><span class="p">.</span><span class="na">accept</span><span class="p">(</span><span class="s">&#34;Hello, World!&#34;</span><span class="p">);</span><span class="w">  </span><span class="c1">// 输出：Hello, World!</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>Supplier&lt;T&gt;</code>：<code>Supplier</code>接口表示提供一个结果的供应商，无输入参数，它通常用于提供或生成某种值；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">T</span><span class="w"> </span><span class="nf">get</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SupplierExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Supplier</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">supplier</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="s">&#34;Hello, Supplier!&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">supplier</span><span class="p">.</span><span class="na">get</span><span class="p">());</span><span class="w">  </span><span class="c1">// 输出：Hello, Supplier!</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>Function&lt;T, R&gt;</code>：<code>Function</code>接口表示接受一个输入参数并返回一个结果的函数，它通常用于将输入转换为输出；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">R</span><span class="w"> </span><span class="nf">apply</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FunctionExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Function</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">lengthFunction</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">length</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">lengthFunction</span><span class="p">.</span><span class="na">apply</span><span class="p">(</span><span class="s">&#34;Hello&#34;</span><span class="p">));</span><span class="w">  </span><span class="c1">// 输出：5</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li><code>Predicate&lt;T&gt;</code>：<code>Predicate</code>接口表示一个接受单个参数并返回布尔值的断言，它通常用于条件判断；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">boolean</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">t</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PredicateExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Predicate</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">isEmpty</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">isEmpty</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">));</span><span class="w">  </span><span class="c1">// 输出：true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">isEmpty</span><span class="p">.</span><span class="na">test</span><span class="p">(</span><span class="s">&#34;Hello&#34;</span><span class="p">));</span><span class="w">  </span><span class="c1">// 输出：false</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<p>在<code>Lambda</code>表达式中，方法的引用也发生了变化，使用<code>::</code>操作符，主要有四种类型：</p>
+<ul>
+<li>引用静态方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Consumer</span><span class="o">&lt;</span><span class="n">List</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">sort</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Collections</span><span class="p">::</span><span class="n">sort</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>引用实例方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">String</span><span class="w"> </span><span class="n">str</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;Hello&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Predicate</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">equals</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">str</span><span class="p">::</span><span class="n">equals</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>引用对象的实例方法；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Function</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">length</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">::</span><span class="n">length</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>引用构造函数；
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Supplier</span><span class="o">&lt;</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">listSupplier</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ArrayList</span><span class="p">::</span><span class="k">new</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h2 id="控制流语句">控制流语句</h2>
+<h3 id="if-else语句">if-else语句</h3>
+<p><code>if</code>语句是最基本的控制语句，它只有在<code>if(exception)</code>为<code>true</code>的时候才会执行特定的代码。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">var1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;hello world ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>if</code>语句后面可以跟<code>else</code>语句，当<code>if(exception)</code>为<code>false</code>时，<code>else</code>语句体将被执行。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="n">var1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">var1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;if ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="k">else</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;else ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>if</code>语句后面可以跟<code>else-if-else</code>语句：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HelloWorld</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="kd">var</span><span class="w"> </span><span class="err">= &#34;</span><span class="n">123</span><span class="s">&#34;;
+</span></span></span><span class="line"><span class="cl"><span class="s">        if (&#34;</span><span class="n">123</span><span class="s">&#34;.equals(var)){
+</span></span></span><span class="line"><span class="cl"><span class="s">            System.out.println(&#34;</span><span class="n">123</span><span class="w"> </span><span class="p">...</span><span class="s">&#34;);
+</span></span></span><span class="line"><span class="cl"><span class="s">        }else if(&#34;</span><span class="n">234</span><span class="s">&#34;.equals(var)){
+</span></span></span><span class="line"><span class="cl"><span class="s">            System.out.println(&#34;</span><span class="n">234</span><span class="w"> </span><span class="p">...</span><span class="s">&#34;);
+</span></span></span><span class="line"><span class="cl"><span class="s">        }else if (&#34;</span><span class="n">345</span><span class="s">&#34;.equals(var)){
+</span></span></span><span class="line"><span class="cl"><span class="s">            System.out.println(&#34;</span><span class="n">345</span><span class="w"> </span><span class="p">...</span><span class="s">&#34;);
+</span></span></span><span class="line"><span class="cl"><span class="s">        }else{
+</span></span></span><span class="line"><span class="cl"><span class="s">            System.out.println(&#34;</span><span class="p">...</span><span class="s">&#34;);
+</span></span></span><span class="line"><span class="cl"><span class="s">        }
+</span></span></span><span class="line"><span class="cl"><span class="s">    }
+</span></span></span><span class="line"><span class="cl"><span class="s">}
+</span></span></span></code></pre></div><h3 id="switch语句">switch语句</h3>
+<p><code>switch</code>语句在项目开发中比较常用，可以和<code>if-else</code>实现相同的功能，但使用<code>switch</code>语句可以提高代码的可读性。</p>
+<p><code>switch-case</code>语句用于判断一个变量是否等于一系列值中的某个值，每个值称为一个分支。
+<code>switch</code>语句还可以包含一个<code>default</code>分支，当没有任何<code>case</code>分支的值与变量值相等时，<code>default</code>分支的代码将被执行。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">case</span><span class="w"> </span><span class="s">&#34;123&#34;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;123&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">case</span><span class="w"> </span><span class="s">&#34;456&#34;</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;456&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">         </span><span class="k">default</span><span class="w"> </span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;over ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">   
+</span></span></span></code></pre></div><p>当变量的值与<code>case</code>语句的值相等时，那么<code>case</code>语句之后的语句开始执行，直到<code>break</code>语句出现，才会跳出<code>switch</code>语句。
+如果没有<code>break</code>语句出现，程序会继续执行下一条<code>case</code>语句，直到出现<code>break</code>语句，需要注意的是，<code>default</code>分支不需要<code>break</code>语句。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="k">case</span><span class="w"> </span><span class="n">100</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;first case ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">          </span><span class="k">case</span><span class="w"> </span><span class="n">200</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;second case ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">              </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>switch</code>语句中的变量类型可以是，<code>byte</code>、<code>short</code>、<code>int</code>、<code>char</code>或者<code>enum</code>，从Java7开始，可以在<code>switch</code>条件判断语句中使用<code>String</code>对象。
+<code>switch</code>不支持<code>long</code>，是因为<code>switch</code>的设计初衷是对那些只有少数的几个值进行等值判断，如果值过于复杂，那么还是用<code>if</code>比较合适。</p>
+<h3 id="for语句">for语句</h3>
+<p>for语句提供了一种紧凑的方法来遍历一系列值。因为它反复循环直到满足特定条件，程序员经常将其称为“for循环”。
+for循环执行的次数是在执行前就确定的，for语句的一般形式可以表示为：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">100</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">i</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>for循环的三个表达式是可选的，例如可以这样创建一个无限循环：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">for(;;){
+</span></span><span class="line"><span class="cl">    // to do ...
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div><p><code>foreach</code>语句是Java5的新特征之一，在遍历数组、集合方面，为开发人员提供了极大的方便。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">arr</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">list</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">s</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在for循环中，<code>可以使用continue</code>语句用来结束当前循环，并进入下一次循环。
+注意仅仅这一次循环结束了，不是所有循环结束了，后边的循环依旧进行。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果s等于1,则结束本次循环 执行下次循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">continue</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>break</code>语句作用是跳出循环，<code>break</code>主要用在循环语句或者<code>switch</code>语句中。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HelloWorld</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// s等于2,结束for循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>如果存在多层循环，要注意<code>break</code>只能跳出一层循环，而不能结束多层循环。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;外层 for ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>如果想要跳出多层循环，可以用以下方式，当然也可以用<code>break</code>跳两次循环。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">test</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="w"> </span><span class="n">test</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;外层 for ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>continue</code>也可以用上面的这种方式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nl">test</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">continue</span><span class="w"> </span><span class="n">test</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;外层 for ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>return</code>语句表示从当前方法退出，控制流返回到调用方法的地方。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">arr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;1&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;2&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;3&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">arr</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;外层 for ...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>return</code>语句有两种形式，一种返回值，另一种不返回值。
+要返回一个值，只需将值(或计算该值的表达式)放在<code>return</code>关键字之后即可，像这样<code>return ++count;</code>。</p>
+<h3 id="do-while和while语句">do-while和while语句</h3>
+<p><code>while</code>语句对表达式进行计算，表达式必须返回一个布尔值。如果表达式的计算结果为<code>true</code>,<code>while</code>语句将执行<code>while</code>块中的语句。
+<code>while</code>语句继续测试表达式并执行其块，直到表达式的计算结果为<code>false</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="k">while</span><span class="p">(</span><span class="o">++</span><span class="n">i</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">       </span><span class="n">i</span><span class="o">--</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>do-while</code>循环和<code>while</code>循环相似。对于<code>while</code>循环如果条件一开始不满足，循环体可能一次也不会执行，而<code>do-while</code>循环它会先执行一次循环体，然后再检查条件。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">i</span><span class="o">++</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34; ... &#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">--</span><span class="n">i</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>while</code>循环、<code>do-while</code>循环和for循环是Java中的三种常见循环结构。在大多数情况下，性能差异可以忽略不计，代码的清晰和易读性才是关键。</p>
+<ul>
+<li><code>while</code>循环：用于在满足条件前可能不执行循环体的情况；</li>
+<li><code>do-while</code>循环：用于至少需要执行一次循环体的情况；</li>
+<li>for循环：用于已知循环次数或需要固定迭代次数的情况；</li>
+</ul>
+<h2 id="参数传递">参数传递</h2>
+<p>对于基本数据类型（如int、char、float等），值传递意味着传递的是变量的副本，是值传递。
+如果是对象，那就是引用传递，这个理解是错误的。</p>
+<p>形式参数与实际参数：</p>
+<ul>
+<li>形式参数：是在定义函数名和函数体的时候使用的参数，目的是用来接收调用该函数时传入的参数；</li>
+<li>实际参数：在调用有参函数时，主调函数和被调函数之间有数据传递关系。在主调函数中调用一个函数时，函数名后面括号中的参数称为“实际参数”；</li>
+</ul>
+<p>举个例子：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">HelloWorld</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 实参 </span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">test</span><span class="p">(</span><span class="s">&#34;world&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 形参</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">test</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">param</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;hello &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">param</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>值传递与引用传递：</p>
+<ul>
+<li>值传递: 是指在调用函数时将实际参数复制一份传递到函数中，这样在函数中如果对参数进行修改，将不会影响到实际参数；</li>
+<li>引用传递: 是指在调用函数时将实际参数的地址直接传递到函数中，那么在函数中对参数所进行的修改，将影响到实际参数；</li>
+</ul>
+<table>
+<thead>
+<tr>
+<th></th>
+<th>值传递</th>
+<th>引用传递</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>区别</td>
+<td>传参时会创建副本</td>
+<td>传参数不创建副本</td>
+</tr>
+<tr>
+<td>描述</td>
+<td>方法中无法修改原始对象</td>
+<td>方法中可以修改原始对象</td>
+</tr>
+</tbody>
+</table>
+<p>举个例子，如果在方法中改变对象的字段值会改变原对象该字段值，因为改变的是同一个地址指向的内容。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">PassByValueExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Dog</span><span class="w"> </span><span class="n">dog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">(</span><span class="s">&#34;A&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">func</span><span class="p">(</span><span class="n">dog</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">dog</span><span class="p">.</span><span class="na">getName</span><span class="p">());</span><span class="w">          </span><span class="c1">// B</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">func</span><span class="p">(</span><span class="n">Dog</span><span class="w"> </span><span class="n">dog</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">dog</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;B&#34;</span><span class="p">);</span><span class="c1">//dog.name=&#34;B&#34;;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>然后有人就说Java传递对象类型参数是引用传递，其实这一点在官方<a href="https://docs.oracle.com/javase/tutorial/java/javaOO/arguments.html">《Java™教程》</a>中有相关的描述。</p>
+<blockquote>
+<p>Passing Reference Data Type Arguments.
+Reference data type parameters, such as objects, are also passed into methods by value. This means that when the method returns, the passed-in reference still references the same object as before. However, the values of the object&rsquo;s fields can be changed in the method, if they have the proper access level.<br></p>
+</blockquote>
+<p>文档大意：
+传递引用数据类型参数，引用数据类型参数(如对象)也按值传递给方法。
+这意味着当方法返回时，传入的引用仍然引用与之前相同的对象，但是如果对象的字段具有适当的访问级别，则可以在方法中更改它们的值。</p>
+<p>所以在Java中的参数传递确实是值传递，但在处理对象引用时，表现出的行为可能让人误以为是引用传递。
+举个例子来更好的理解：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyObject</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PassByValueExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">MyObject</span><span class="w"> </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">10</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">modifyObject</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After method call: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="p">);</span><span class="w">  </span><span class="c1">// 输出: 20</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">resetObject</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;After resetObject call: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="p">);</span><span class="w">  </span><span class="c1">// 输出: 20</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">modifyObject</span><span class="p">(</span><span class="n">MyObject</span><span class="w"> </span><span class="n">obj</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">20</span><span class="p">;</span><span class="w">  </span><span class="c1">// 修改对象的属性，会影响原对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">resetObject</span><span class="p">(</span><span class="n">MyObject</span><span class="w"> </span><span class="n">obj</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyObject</span><span class="p">();</span><span class="w">  </span><span class="c1">// 修改的是引用的副本，不影响原引用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">obj</span><span class="p">.</span><span class="na">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">30</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>值传递和引用传递最大的区别是，传递的过程中有没有复制出一个副本来，如果是传递副本，那就是值传递，否则就是引用传递。
+在Java中，其实是通过值传递实现的参数传递，只不过对于Java对象的传递，传递的内容是对象的引用的副本。
+所以Java的参数是以值传递的形式传入方法中，而不是引用传递。
+Java对象的传递，是通过复制的方式把引用关系传递了。如果我们没有改引用关系，而是找到引用的地址，把里面的内容改了，是会对调用方有影响的，因为大家指向的是同一个共享地址。</p>
+<h2 id="浮点类精度问题">浮点类精度问题</h2>
+<p>在Java中，使用浮点类型进行计算会造成精度丢失。例如：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 0.20000005</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 0.19999999999999996</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2d</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>那么为什么浮点类型会存在精度精度丢失问题呢？
+因为Java的浮点类型在计算机中是用二进制来存储的，也就是小数在转二进制的时候出现了精度丢失。</p>
+<p>小数如何转二进制？
+将待转的数字乘以2，取出整数部分作为二进制表示的第1位，然后再将小数部分乘以2，将得到的整数部分作为二进制表示的第2位，以此类推，直到小数部分为0。
+特殊情况，如果小数部分出现循环，无法停止，则用有限的二进制位无法准确表示一个小数，这也是在编程语言中表示小数会出现误差的原因。
+例如，0.1转二进制：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">0.1 x 2 = 0.2  取整数位 0
+</span></span><span class="line"><span class="cl">0.2 x 2 = 0.4  取整数位 0
+</span></span><span class="line"><span class="cl">0.4 x 2 = 0.8  取整数位 0
+</span></span><span class="line"><span class="cl">0.8 x 2 = 1.6  取整数位 1
+</span></span><span class="line"><span class="cl">0.6 x 2 = 1.2  取整数位 1
+</span></span><span class="line"><span class="cl">0.2 x 2 = 0.4  取整数位 0
+</span></span><span class="line"><span class="cl">0.4 x 2 = 0.8  取整数位 0
+</span></span><span class="line"><span class="cl">0.8 x 2 = 1.6  取整数位 1
+</span></span><span class="line"><span class="cl">0.6 x 2 = 1.2  取整数位 1
+</span></span><span class="line"><span class="cl">........无限循环
+</span></span></code></pre></div><p>因为计算机中存储一个浮点类型所用的位数是有限的，所以遇到无限循环的小数，只能选择在某个精度进行保存。
+由于计算机中保存的小数其实是十进制的小数的近似值，并不是准确值，所以，千万不要在代码中使用浮点数来表示金额等重要的指标。</p>
+<p>那怎么解决浮点精度丢失问题？
+Java中的<code>BigDecimal</code>类提供了精确的十进制数学运算，避免了浮点数精度丢失的问题。
+<code>BigDecimal</code>能够保证精度主要因为它基于十进制表示和算术运算，避免了二进制浮点数在表示和计算小数时可能出现的舍入误差和精度问题。</p>
+<h2 id="bigdecimal">BigDecimal</h2>
+<p>Java在<code>java.math</code>包中提供的API类<code>BigDecimal</code>，用来对超过16位有效位的数进行精确的运算。
+双精度浮点型变量<code>double</code>可以处理16位有效数，在实际应用中，需要对更大或者更小的数进行运算和处理，所以需要用到<code>BigDecimal</code>。</p>
+<p>Java中提供了大数字(超过16位有效位)的操作类，即<code>java.math.BinInteger</code>类和<code>java.math.BigDecimal</code>类，用于高精度计算。
+其中<code>BigInteger</code>类是针对大整数的处理类，而<code>BigDecimal</code>类则是针对大小数的处理类。<code>BigDecimal</code>类的实现用到了<code>BigIntege</code>类，不同的是<code>BigDecimal</code>加入了小数的概念。</p>
+<h3 id="基本用法">基本用法</h3>
+<p><code>BigDecimal</code>一共有两种方法可以进行初始化赋值，构造器初始化赋值，<code>valueOf</code>方法初始化赋值。
+在使用<code>BigDecimal</code>中参数为<code>double</code>类型的构造器时，发现存储结果并不准确。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 打印结果: 0.200000000000000011102230246251565404236316680908203125</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="n">0</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>找到Java API中的相关描述：</p>
+<blockquote>
+<p>The results of this constructor can be somewhat unpredictable.
+One might assume that writing {@code new BigDecimal(0.1)} in Java creates a {@code BigDecimal} which is exactly equal to 0.1 (an unscaled value of 1, with a scale of 1), but it is actually equal to 0.1000000000000000055511151231257827021181583404541015625.
+This is because 0.1 cannot be represented exactly as a {@code double} (or, for that matter, as a binary fraction of any finite length).<br>
+Thus, the value that is being passed<i>in</i> to the constructor is not exactly equal to 0.1, appearances notwithstanding.<br>
+The {@code String} constructor, on the other hand, is perfectly predictable: writing {@code new BigDecimal(&ldquo;0.1&rdquo;)} creates a {@code BigDecimal} which is <i>exactly</i> equal to 0.1, as one would expect.  Therefore, it is generally recommended that the {@linkplain #BigDecimal(String)<tt>String</tt> constructor} be used in preference to this one.</p>
+</blockquote>
+<p>大概意思是说，用<code>double</code>作为参数的构造函数，无法精确构造一个<code>BigDecimal</code>对象，需要自己指定一个上下文的环境，也就是指定精确位。
+而利用<code>String</code>对象作为参数传入的构造函数能精确的构造出一个<code>BigDecimal</code>对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 0.2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;0.2&#34;</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>所以要想获得精确的结果，要使用<code>BigDecimal</code>的字符串构造函数，不要使用<code>double</code>参数的构造函数。</p>
+<p><code>BigDecimal</code>所创建的是对象，我们不能使用传统的<code>+、-、*、/</code>等算术运算符直接对其对象进行数学运算，而必须调用其相对应的方法。
+方法中的参数也必须是<code>BigDecimal</code>的对象，构造器是类的特殊方法，专门用来创建对象，特别是带有参数的对象。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 + num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">subtract</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 - num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">multiply</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 * num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">divide</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 / num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 绝对值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;|num1 / num2| = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">.</span><span class="na">abs</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>另外说一下<code>BigDecimal</code>如何转换其他类型。
+<code>BigDecimal</code>类提供了<code>intValue</code>,<code>byteValue</code>,<code>shortValue</code>等将<code>BigDecimal</code>对象转换成对应类型的方法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">bigDecimal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">byteValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">shortValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">intValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">floatValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">doubleValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">bigDecimal</span><span class="p">.</span><span class="na">longValue</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="舍入规则">舍入规则</h3>
+<p>在使用除法的时候如果两个数字，除不尽而又没有设置精确小数位和舍入模式，就会报错：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">divide</span><span class="p">(</span><span class="n">num2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 / num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Exception in thread &#34;main&#34; java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.
+</span></span></code></pre></div><p>为了防止报错，我们可以这样写：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;3&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num1</span><span class="p">.</span><span class="na">divide</span><span class="p">(</span><span class="n">num2</span><span class="p">,</span><span class="n">3</span><span class="p">,</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">.</span><span class="na">ROUND_UP</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 打印结果: num1 / num2 = 0.334</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;num1 / num2 = %s\n&#34;</span><span class="p">,</span><span class="n">num3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>BigDecimal</code>类<code>divide</code>方法中<code>roundingMode</code>参数为舍入规则，如果不指定默认采用则四舍五入方式。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// divisor: 除数; scale: 精确小数位; roundingMode: 舍入规则</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">BigDecimal</span><span class="w"> </span><span class="nf">divide</span><span class="p">(</span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">divisor</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">scale</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">roundingMode</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p><code>BigDecimal</code>类在进行数值运算时，可以通过指定不同的舍入规则来控制计算结果的精确度和舍入方式。
+舍入规则由<code>RoundingMode</code>枚举类定义，Java 提供了几种常见的舍入模式，每种模式都适用于不同的应用场景和需求，我们在使用<code>BigDecimal</code>除法的时候，最好要指定精确小数位和舍入模式。</p>
+<ul>
+<li><code>RoundingMode.UP</code>：向正无穷方向舍入，即始终向远离零的方向舍入。例如，对 <code>3.14</code> 使用 <code>UP</code> 模式舍入结果为 <code>4</code>。</li>
+<li><code>RoundingMode.DOWN</code>：向零方向舍入，即截断小数部分。例如，对 <code>3.14</code> 使用 <code>DOWN</code> 模式舍入结果为 <code>3</code>。</li>
+<li><code>RoundingMode.CEILING</code>：向正无穷方向舍入，如果是正数则表现和 <code>UP</code> 一样，如果是负数则表现和 <code>DOWN</code> 一样。例如，对 <code>-3.14</code> 使用 <code>CEILING</code> 模式舍入结果为 <code>-3</code>；对 <code>3.14</code> 使用 <code>CEILING</code> 模式舍入结果为 <code>4</code>。</li>
+<li><code>RoundingMode.FLOOR</code>：向负无穷方向舍入，如果是正数则表现和 <code>DOWN</code> 一样，如果是负数则表现和 <code>UP</code> 一样。例如，对 <code>-3.14</code> 使用 <code>FLOOR</code> 模式舍入结果为 <code>-4</code>；对 <code>3.14</code> 使用 <code>FLOOR</code> 模式舍入结果为 <code>3</code>。</li>
+<li><code>RoundingMode.HALF_UP</code>：四舍五入，当舍弃部分 &gt;= 0.5 时，舍入行为同 <code>UP</code>；否则，舍入行为同 <code>DOWN</code>。例如，对 <code>3.5</code> 使用 <code>HALF_UP</code> 模式舍入结果为 <code>4</code>；对 <code>3.4</code> 使用 <code>HALF_UP</code> 模式舍入结果为 <code>3</code>。</li>
+<li><code>RoundingMode.HALF_DOWN</code>：四舍五入，当舍弃部分 &gt; 0.5 时，舍入行为同 <code>UP</code>；否则，舍入行为同 <code>DOWN</code>。例如，对 <code>3.5</code> 使用 <code>HALF_DOWN</code> 模式舍入结果为 <code>3</code>；对 <code>3.4</code> 使用 <code>HALF_DOWN</code> 模式舍入结果为 <code>3</code>。</li>
+<li><code>RoundingMode.HALF_EVEN</code>：银行家舍入法，当舍弃部分等于 0.5 时，舍入行为同 <code>HALF_UP</code>；否则，舍入行为同 <code>HALF_DOWN</code>。例如，对 <code>2.5</code> 使用 <code>HALF_EVEN</code> 模式舍入结果为 <code>2</code>；对 <code>3.5</code> 使用 <code>HALF_EVEN</code> 模式舍入结果为 <code>4</code>。</li>
+<li><code>RoundingMode.UNNECESSARY</code>：不需要舍入，如果计算结果需要舍入，则抛出 <code>ArithmeticException</code> 异常。</li>
+</ul>
+<h3 id="scale属性">scale属性</h3>
+<p><code>BigDecimal</code>对象中<code>scale</code>字段属性，指的是小数点后面的位数，比如，对于<code>BigDecimal</code>值 123.45，<code>scale</code>是 2。</p>
+<p><code>setScale</code>可以增加或减少<code>BigDecimal</code>的小数位数。
+当增加小数位数时，新增加的位数会被填充为零。当减少小数位数时，多余的位数会被舍去，并根据指定的舍入模式进行舍入。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">BigDecimalSetScaleExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;123.4567&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 增加 scale</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">increasedScale</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">.</span><span class="na">setScale</span><span class="p">(</span><span class="n">6</span><span class="p">,</span><span class="w"> </span><span class="n">RoundingMode</span><span class="p">.</span><span class="na">UNNECESSARY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Increased scale: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">increasedScale</span><span class="p">);</span><span class="w"> </span><span class="c1">// 123.456700</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 减少 scale，并使用四舍五入模式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">decreasedScale</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">.</span><span class="na">setScale</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">RoundingMode</span><span class="p">.</span><span class="na">HALF_UP</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Decreased scale: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">decreasedScale</span><span class="p">);</span><span class="w"> </span><span class="c1">// 123.46</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 减少 scale，并使用向下舍入模式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">decreasedScaleDown</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">num</span><span class="p">.</span><span class="na">setScale</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="w"> </span><span class="n">RoundingMode</span><span class="p">.</span><span class="na">DOWN</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Decreased scale (down): &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">decreasedScaleDown</span><span class="p">);</span><span class="w"> </span><span class="c1">// 123.45</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>setScale</code>方法用于设置<code>BigDecimal</code>对象的<code>scale</code>，并且可以指定舍入模式。
+在设置新的<code>scale</code>时，如果不指定舍入模式且新的<code>scale</code>小于当前<code>scale</code>，则会抛出<code>ArithmeticException</code>异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.12345&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">num1</span><span class="p">.</span><span class="na">setScale</span><span class="p">(</span><span class="n">4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">num1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">java.lang.ArithmeticException: Rounding necessary
+</span></span></code></pre></div><h3 id="比较大小">比较大小</h3>
+<p>使用<code>BigDecimal</code>进行比较操作需要特别注意，因为<code>BigDecimal</code>是用于精确计算的数据类型，不能像基本数据类型一样直接使用比较操作符，如 <code>&lt;, &gt;, ==</code>来比较。
+可以用<code>BigDecimal</code>的<code>equals</code>方法来进行比较。这里要注意，<code>equals</code>方法会比较数值和精度是否完全相同，即使两个对象表示的是相同的数值但精度不同，也会返回<code>false</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.10&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">num3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// false</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">num1</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">num2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// true</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">num2</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">num3</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>可以看到<code>1.10</code>和<code>1.1</code>数值是相等的，而<code>equals</code>方法返回的却是<code>false</code>。看一下<code>BigDecimal</code>中重写的<code>equals</code>的源码：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * Compares this {@code BigDecimal} with the specified
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * {@code Object} for equality.  Unlike {@link
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * #compareTo(BigDecimal) compareTo}, this method considers two
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * {@code BigDecimal} objects equal only if they are equal in
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * value and scale (thus 2.0 is not equal to 2.00 when compared by
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * this method).
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @param  x {@code Object} to which this {@code BigDecimal} is
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *         to be compared.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @return {@code true} if and only if the specified {@code Object} is a
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *         {@code BigDecimal} whose value and scale are equal to this
+</span></span></span><span class="line"><span class="cl"><span class="cm"> *         {@code BigDecimal}&#39;s.
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @see    #compareTo(java.math.BigDecimal)
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @see    #hashCode
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">equals</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="n">x</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="k">instanceof</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">xDec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">BigDecimal</span><span class="p">)</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">x</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="k">this</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">scale</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">xDec</span><span class="p">.</span><span class="na">scale</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">long</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">intCompact</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">long</span><span class="w"> </span><span class="n">xs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xDec</span><span class="p">.</span><span class="na">intCompact</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">INFLATED</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">xs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">INFLATED</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">xs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">compactValFor</span><span class="p">(</span><span class="n">xDec</span><span class="p">.</span><span class="na">intVal</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">xs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">s</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">xs</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">INFLATED</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">xs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">compactValFor</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">intVal</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">inflated</span><span class="p">().</span><span class="na">equals</span><span class="p">(</span><span class="n">xDec</span><span class="p">.</span><span class="na">inflated</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>文档中有这么一段描述：</p>
+<blockquote>
+<p>objects equal only if they are equal in value and scale. thus 2.0 is not equal to 2.00 when compared by this method</p>
+</blockquote>
+<p>大意：对象只有在<code>value</code>和<code>scale</code>相等时才相等。因此，用本方法比较时，2.0不等于2.00。</p>
+<p>所以不要用<code>equals</code>方法来比较<code>BigDecimal</code>对象，因为它的<code>equals</code>方法会比较<code>scale</code>，如果<code>scale</code>不一样，它会返回<code>false</code>。
+如果需要比较数值相等，不考虑精度，可以使用<code>compareTo</code>方法进行比较，并判断返回的结果是否为0。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.10&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BigDecimal</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BigDecimal</span><span class="p">(</span><span class="s">&#34;1.1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a小于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a等于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a大于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a大于等于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">1</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;a小于等于b&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="math">Math</h2>
+<p><code>java.lang.Math</code>，该类和Java中的运算息息相关。<code>Math</code>类是一个工具类，被<code>final</code>修饰，构造方法是私有的，大部分方法都被<code>public static</code>修饰。</p>
+<p>基本用法：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 计算平方根</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;4的平方根: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">sqrt</span><span class="p">(</span><span class="n">4</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">//计算立方根</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;8的立方根: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">cbrt</span><span class="p">(</span><span class="n">8</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 计算n的m次方</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;2的3次方: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">pow</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="n">3</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 计算最大值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1和2中最大值: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">max</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 计算最小值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1和2中最小值: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">min</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="n">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 求绝对值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;-1的绝对值: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">abs</span><span class="p">(</span><span class="o">-</span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 向上取整</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1.2向上取整: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 向下取整</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1.2向下取整: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">floor</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// [0,1)区间的随机数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;[0,1)区间的随机数: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 返回与参数值最接近的 double值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kt">double</span><span class="w"> </span><span class="n">rint</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">rint</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;rint方法: %s\n&#34;</span><span class="p">,</span><span class="n">rint</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="c1">// 四舍五入 float时返回int值，double时返回long值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kt">long</span><span class="w"> </span><span class="n">round</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">round1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5f</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;round方法: 1.5四舍五入: %s\n&#34;</span><span class="p">,</span><span class="n">round</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="ceil和floor">ceil和floor</h3>
+<p><code>ceil</code>方法的功能是向上取整。<code>ceil</code>译为“天花板”，顾名思义就是对操作数取顶，<code>Math.ceil(a)</code>就是取大于a的最小整数。
+需要注意的是它的返回值不是<code>int</code>类型，而是<code>double</code>类型。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 向上取整</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1.2向上取整: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span></code></pre></div><p><code>floor</code>方法的功能是向下取整。<code>floor</code>译为“地板”，顾名思义是对操作数取底。
+<code>Math.floor(a)</code>，就会取小于a的最大整数。它的返回值类型与<code>ceil</code>一致，也是<code>double</code>类型。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 向下取整</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;1.2向下取整: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">floor</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">2</span><span class="p">));</span><span class="w">
+</span></span></span></code></pre></div><p>一般情况下，<code>Math.ceil(x)</code>的值正好是<code>-Math.floor(-x)</code>的值。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Math.ceil(1.2) = 2.0
+</span></span><span class="line"><span class="cl">-Math.floor(-1.2) = 2.0
+</span></span></code></pre></div><p>特殊情况：</p>
+<ul>
+<li>如果参数值已经等于一个数学整数，则结果与参数相同。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">double</span><span class="w"> </span><span class="n">result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">2</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(2.0): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result1</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 2.0</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>如果参数是NaN或无穷大或正零或负零，则结果与参数相同。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">double</span><span class="w"> </span><span class="n">result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">Double</span><span class="p">.</span><span class="na">NaN</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(Double.NaN): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result2</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 NaN</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">result5</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="n">0</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(0.0): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result5</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 0.0</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">double</span><span class="w"> </span><span class="n">result6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="o">-</span><span class="n">0</span><span class="p">.</span><span class="na">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(-0.0): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result6</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 -0.0</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>如果实参值小于零但大于-1.0，则结果为负零。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kt">double</span><span class="w"> </span><span class="n">result7</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">ceil</span><span class="p">(</span><span class="o">-</span><span class="n">0</span><span class="p">.</span><span class="na">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Math.ceil(-0.5): %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">result7</span><span class="p">);</span><span class="w"> </span><span class="c1">// 输出 -0.0</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ul>
+<h3 id="random">random</h3>
+<p><code>random</code>方法是 Java 中用于生成伪随机数的基本方法之一。它返回一个<code>double</code>类型的随机数，范围在<code>[0.0, 1.0)</code>，包括0.0但不包括1.0。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">RandomExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 生成一个 0.0 到 1.0 之间的随机数（不包括 1.0）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">double</span><span class="w"> </span><span class="n">randomValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;随机数: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">randomValue</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>由于<code>random</code>方法生成的是<code>[0.0, 1.0)</code>之间的随机数，可以通过数学运算将其转换为不同范围的随机数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">RandomExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">5</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">max</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">15</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">randomInt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">min</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">()</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p">((</span><span class="n">max</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">min</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;%d 到 %d 之间的随机整数: %d\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">min</span><span class="p">,</span><span class="w"> </span><span class="n">max</span><span class="p">,</span><span class="w"> </span><span class="n">randomInt</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>通过源码可以看到，<code>Math.random</code>底层是调用了<code>Random</code>类中<code>nextDouble</code>方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">random</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">RandomNumberGeneratorHolder</span><span class="p">.</span><span class="na">randomNumberGenerator</span><span class="p">.</span><span class="na">nextDouble</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// Random.nextDouble</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="nf">nextDouble</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="p">(((</span><span class="kt">long</span><span class="p">)(</span><span class="n">next</span><span class="p">(</span><span class="n">26</span><span class="p">))</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">27</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">next</span><span class="p">(</span><span class="n">27</span><span class="p">))</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">DOUBLE_UNIT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>也就是说以下代码执行的逻辑是相同的：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// [0,1)区间的随机数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;[0,1)区间的随机数: %s\n&#34;</span><span class="p">,</span><span class="n">Math</span><span class="p">.</span><span class="na">random</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;[0,1)区间的随机数: %s\n&#34;</span><span class="p">,</span><span class="k">new</span><span class="w"> </span><span class="n">Random</span><span class="p">().</span><span class="na">nextDouble</span><span class="p">());</span><span class="w">
+</span></span></span></code></pre></div><p><code>Random</code>类位于<code>java.util</code>包下，此类的实例用于生成伪随机数流。
+之所以称之为伪随机，是因为真正意义上的随机数（或者称为随机事件）在某次产生过程中是按照实验过程表现的分布概率随机产生的，其结果是不可预测，不可见的。
+而计算机中的随机函数是按照一定的算法模拟产生的，其结果是确定的，可见的。我们认为这样产生的数据不是真正意义上的随机数，因而称之为伪随机。</p>
+<p>该类提供了两种构造方法，无参构造底层调用的也是有参构造。
+将<code>System.nanoTime()</code>作为参数传递。如果使用无参构造，默认的<code>seed</code>值为<code>System.nanoTime()</code>。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 无参构造</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">Random</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="k">this</span><span class="p">(</span><span class="n">seedUniquifier</span><span class="p">()</span><span class="w"> </span><span class="o">^</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 有参构造</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nf">Random</span><span class="p">(</span><span class="kt">long</span><span class="w"> </span><span class="n">seed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">getClass</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Random</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">seed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicLong</span><span class="p">(</span><span class="n">initialScramble</span><span class="p">(</span><span class="n">seed</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// subclass might have overriden setSeed</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">seed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AtomicLong</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">setSeed</span><span class="p">(</span><span class="n">seed</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>要注意的是用有参构造创建<code>Random</code>对象，如果随机种子相同，不管执行多少次，最后结果都是相同的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Random</span><span class="w"> </span><span class="n">random</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Random</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 第一次执行程序打印结果: 随机数: -1155869325</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 第二次执行程序打印结果: 随机数: -1155869325</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;随机数: %s\n&#34;</span><span class="p">,</span><span class="n">random</span><span class="p">.</span><span class="na">nextInt</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="round">round</h3>
+<p><code>round</code>方法用于对浮点数进行四舍五入，并返回最接近的整数。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 四舍五入 float时返回int值，double时返回long值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">long</span><span class="w"> </span><span class="n">round</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kt">int</span><span class="w"> </span><span class="n">round1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">1</span><span class="p">.</span><span class="na">5f</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;round方法: 1.5四舍五入: %s\n&#34;</span><span class="p">,</span><span class="n">round</span><span class="p">);</span><span class="w">
+</span></span></span></code></pre></div><p>一般情况，<code>round</code>方法用于对浮点数进行四舍五入，并返回最接近的整数。特殊情况:</p>
+<ul>
+<li>如果参数是NaN，结果是0；NaN表示非数值，例如：0.0/0结果为NAN，负数的平方根结果也为NAN；</li>
+<li>如果参数是负无穷大或小于或等于<code>Integer.MIN_VALUE</code>，结果为<code>Integer.MIN_VALUE</code>；</li>
+<li>如果参数是正无穷大或大于或等于<code>Integer.MAX_VALUE</code>，结果为<code>Integer.MAX_VALUE</code>；</li>
+</ul>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 四舍五入 float时返回int值，double时返回long值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">round1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">long</span><span class="w"> </span><span class="n">round2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">Double</span><span class="p">.</span><span class="na">NaN</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">round3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="n">2147483648123L</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">round4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">round</span><span class="p">(</span><span class="o">-</span><span class="n">2147483647123L</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;0四舍五入: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">round1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Double.NaN=[%s],四舍五入: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Double</span><span class="p">.</span><span class="na">NaN</span><span class="p">,</span><span class="w"> </span><span class="n">round2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Integer.MAX_VALUE=[%s] + 1 四舍五入: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">,</span><span class="w"> </span><span class="n">round3</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">&#34;Integer.MIN_VALUE=[%s] - 1 四舍五入: %s\n&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="p">.</span><span class="na">MIN_VALUE</span><span class="p">,</span><span class="w"> </span><span class="n">round4</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Math.round()</code>和<code>BigDecimal</code>类的四舍五入方法在实现和使用上有一些显著的区别。
+<code>Math.round()</code>适用于对普通的浮点数进行简单的整数舍入，例如将浮点数转换为最接近的整数值。
+<code>BigDecimal.setScale()</code>适用于需要精确控制数值精度和舍入方式的场景，特别是在金融计算、税务计算等要求高精度和可预测舍入行为的应用中。</p>
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diff --git a/docs/posts/javabasics/rookie-reflect/index.html b/docs/posts/javabasics/rookie-reflect/index.html
new file mode 100644
index 00000000..517f2e41
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+<html lang="zh" >
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+
+    
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+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%a6%82%e8%bf%b0">
+                    概述
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%b0%84%e5%85%a5%e5%8f%a3">
+                    反射入口
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+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
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+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%93%8d%e4%bd%9c%e5%8f%8d%e5%b0%84">
+                    操作反射
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%b0%84%e7%89%b9%e7%82%b9">
+                    反射特点
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%b0%84%e6%80%a7%e8%83%bd">
+                    反射性能
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%b0%84%e5%8e%9f%e7%90%86">
+                    反射原理
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%b0%84%e5%ba%94%e7%94%a8%e5%9c%ba%e6%99%af">
+                    反射应用场景
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
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+            
+            
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+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%b0%84%e4%b8%8e%e6%b3%a8%e8%a7%a3">
+                    反射与注解
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%b0%84%e4%b8%8e%e6%9e%9a%e4%b8%be">
+                    反射与枚举
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+            </li>
+            
+            
+        </ul>
+        
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+        
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+        
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+                <a class="nav-link text-left" href="#%e5%8f%8d%e5%b0%84%e4%b8%8e%e6%a1%86%e6%9e%b6">
+                    反射与框架
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Java反射</h2>
+                        <span id="post_page_title_date" class="date">2021.10.02</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="概述">概述</h2>
+<p>在Java程序运行状态中，对于任意一个实体类，都能够知道这个类的所有属性和方法，对于任意一个对象，都能够调用它的任意方法和属性。这种动态获取信息以及动态调用对象方法的功能，称为Java语言的反射机制。</p>
+<p>反射是Java语言的一个特性，它允许程序在运行时来进行自我检查并且对内部的成员进行操作。通过反射，我们可以在运行时获得程序或程序集中每一个类型的成员和成员的信息。
+程序中一般的对象的类型都是在编译期就确定下来的，而Java反射机制可以动态地创建对象并调用其属性，这样的对象的类型在编译期是未知的。
+反射的核心是JVM在运行时动态加载类或调用方法、访问属性，它不需要事先知道运行对象是谁。本质是JVM得到<code>class</code>对象之后，再通过<code>class</code>对象进行反编译，从而获取对象的各种信息。</p>
+<h2 id="反射入口">反射入口</h2>
+<p>在操作反射前我们要先了解一些Class类。Java的<code>Class</code>类是java反射机制的基础，通过<code>Class</code>类我们可以获得关于一个类的相关信息。
+虚拟机为每种类型管理一个独一无二的<code>Class</code>对象，也就是说每个类都有一个<code>Class</code>对象。运行程序时，Java虚拟机首先检查是否所要加载的类对应的<code>Class</code>对象是否已经加载。
+如果没有加载，JVM就会根据类名查找<code>.class</code>文件，并将其<code>Class</code>对象载入。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">private</span><span class="w">  </span><span class="nf">Class</span><span class="p">(</span><span class="n">ClassLoader</span><span class="w"> </span><span class="n">loader</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">classLoader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">loader</span><span class="p">;</span><span class="w"> 
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p><code>Class</code>类的构造器是私有的，只有JVM可以创建<code>Class</code>的对象。因此不可以像普通类一样<code>new</code>一个<code>Class</code>对象，但是却可以通过已有的类得到一个<code>Class</code>对象。
+在运行时获取<code>Class</code>的对象，共有三种方式：</p>
+<ol>
+<li>通过<code>Class.forName()</code>方法。这种方式使用类的全限定名（包名+类名）来获取<code>Class</code>对象，常用于动态加载类。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">try {
+</span></span><span class="line"><span class="cl">    Class&lt;?&gt; clazz = Class.forName(&#34;com.example.MyClass&#34;);
+</span></span><span class="line"><span class="cl">} catch (ClassNotFoundException e) {
+</span></span><span class="line"><span class="cl">    e.printStackTrace();
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>通过类的<code>.class</code>属性。这种方式在编译时就已经知道类的类型，适用于静态加载类。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MyClass</span><span class="p">.</span><span class="na">class</span><span class="p">;</span><span class="w">
+</span></span></span></code></pre></div></li>
+<li>通过对象的<code>getClass()</code>方法。这种方式通过已知对象来获取它的<code>Class</code>对象。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="n">MyClass</span><span class="w"> </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">obj</span><span class="p">.</span><span class="na">getClass</span><span class="p">();</span><span class="w">
+</span></span></span></code></pre></div></li>
+</ol>
+<h2 id="操作反射">操作反射</h2>
+<p>在Java中，只要给定类的名字，就可以通过反射机制来获得类的所有信息、调用方法、访问和修改属性等操作。
+反射使得程序可以在运行时检查类的结构和行为，而不需要在编译时知道类的具体信息。使用反射会有异常出现，注意处理异常。Java中<code>Class</code>类和<code>java.lang.reflect</code>一起对反射提供了支持。</p>
+<ul>
+<li>反射可以获取类的完整信息，包括类名、包名、父类、接口、构造函数、字段和方法等。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Class&lt;?&gt; clazz = Class.forName(&#34;java.util.ArrayList&#34;);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取类名
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Class Name: &#34; + clazz.getName());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取包名
+</span></span><span class="line"><span class="cl">Package pkg = clazz.getPackage();
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Package Name: &#34; + pkg.getName());
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取所有构造函数
+</span></span><span class="line"><span class="cl">Constructor&lt;?&gt;[] constructors = clazz.getConstructors();
+</span></span><span class="line"><span class="cl">for (Constructor&lt;?&gt; constructor : constructors) {
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Constructor: &#34; + constructor);
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取所有方法
+</span></span><span class="line"><span class="cl">Method[] methods = clazz.getMethods();
+</span></span><span class="line"><span class="cl">for (Method method : methods) {
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Method: &#34; + method.getName());
+</span></span><span class="line"><span class="cl">}
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取所有字段
+</span></span><span class="line"><span class="cl">Field[] fields = clazz.getDeclaredFields();
+</span></span><span class="line"><span class="cl">for (Field field : fields) {
+</span></span><span class="line"><span class="cl">    System.out.println(&#34;Field: &#34; + field.getName());
+</span></span><span class="line"><span class="cl">}
+</span></span></code></pre></div></li>
+<li>反射可以在运行时创建类的实例，而不需要在编译时知道类的名字。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Class&lt;?&gt; clazz = Class.forName(&#34;java.util.ArrayList&#34;);
+</span></span><span class="line"><span class="cl">Constructor&lt;?&gt; constructor = clazz.getConstructor();
+</span></span><span class="line"><span class="cl">Object instance = constructor.newInstance();
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Instance: &#34; + instance);
+</span></span></code></pre></div></li>
+<li>反射允许在运行时访问和修改对象的字段，即使字段是私有的。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Class&lt;?&gt; clazz = Class.forName(&#34;com.example.Person&#34;);
+</span></span><span class="line"><span class="cl">Object person = clazz.getConstructor().newInstance();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取私有字段
+</span></span><span class="line"><span class="cl">Field nameField = clazz.getDeclaredField(&#34;name&#34;);
+</span></span><span class="line"><span class="cl">nameField.setAccessible(true);  // 允许访问私有字段
+</span></span><span class="line"><span class="cl">nameField.set(person, &#34;John Doe&#34;);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取字段值
+</span></span><span class="line"><span class="cl">String name = (String) nameField.get(person);
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Name: &#34; + name);
+</span></span></code></pre></div></li>
+<li>反射可以在运行时调用对象的方法，包括私有方法。
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">Class&lt;?&gt; clazz = Class.forName(&#34;com.example.Person&#34;);
+</span></span><span class="line"><span class="cl">Object person = clazz.getConstructor().newInstance();
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 获取方法
+</span></span><span class="line"><span class="cl">Method setNameMethod = clazz.getMethod(&#34;setName&#34;, String.class);
+</span></span><span class="line"><span class="cl">Method getNameMethod = clazz.getMethod(&#34;getName&#34;);
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">// 调用方法
+</span></span><span class="line"><span class="cl">setNameMethod.invoke(person, &#34;Jane Doe&#34;);
+</span></span><span class="line"><span class="cl">String name = (String) getNameMethod.invoke(person);
+</span></span><span class="line"><span class="cl">System.out.println(&#34;Name: &#34; + name);
+</span></span></code></pre></div></li>
+</ul>
+<h2 id="反射特点">反射特点</h2>
+<p>通过反射机制我们可以获得类的各种内容，进行反编译。对于Java这种先编译再运行的语言来说，反射机制可以使代码更加灵活，更加容易实现面向对象。</p>
+<ul>
+<li>反射允许在运行时动态加载类、创建对象、调用方法和访问属性，这使得程序具有更高的灵活性和动态性，可以根据运行时的需求来适应不同的情况。</li>
+<li>反射使得编写通用代码和框架变得更加容易。例如，许多框架和库（如Spring和Hibernate）利用反射来实现依赖注入、持久化等功能，从而提高了代码的复用性和可维护性。</li>
+<li>反射可以帮助解耦合，减少类之间的依赖关系。通过反射，可以在不知道具体类名的情况下操作对象，从而简化了系统的结构和设计。</li>
+</ul>
+<p>反射功能虽然强大，但不应任意使用。如果一个功能可以不用反射完成，那么最好就不用。</p>
+<ul>
+<li>性能开销 ：反射操作通常比直接调用要慢。因为反射调用涉及到动态查找方法、字段和进行安全检查，这些步骤在运行时会带来额外的性能开销。在性能敏感的场景下，频繁使用反射可能会导致程序性能下降。</li>
+<li>安全限制 ：反射打破了Java语言的封装性和安全性，可以访问和修改私有成员，甚至可以执行敏感操作。因此在使用反射时需要格外注意安全性问题，避免不必要的暴露和风险。</li>
+<li>内部暴露 ：使用反射可以使代码更加复杂和难以理解。反射操作的代码通常比直接调用的代码更加复杂，可读性较差，可能增加代码维护的困难。</li>
+</ul>
+<h2 id="反射性能">反射性能</h2>
+<p>Java反射机制提供了一种在运行时动态操作类、方法和属性的强大能力。这使得反射成为许多框架和库的基础，如<code>Spring</code>和<code>Hibernate</code>。然而反射的灵活性是有代价的，反射操作通常比直接调用要慢得多。
+以下是一个比较直接方法调用和反射调用性能的示例：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReflectionPerformanceTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MyClass</span><span class="w"> </span><span class="n">myClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MyClass</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;myMethod&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">iterations</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">1000000</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 直接调用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">startTime</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">iterations</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">myClass</span><span class="p">.</span><span class="na">myMethod</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">endTime</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">directCallDuration</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">endTime</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">startTime</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Direct call duration: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">directCallDuration</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; ns&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 反射调用</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">startTime</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">iterations</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">myClass</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">endTime</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">nanoTime</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">reflectionCallDuration</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">endTime</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">startTime</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Reflection call duration: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">reflectionCallDuration</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34; ns&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// Some operation</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>反射慢的主要原因是在于它绕过了编译时的优化，并且在运行时需要动态查找类信息和进行安全性检查，导致额外的性能开销。</p>
+<ol>
+<li>绕过编译时优化： Java编译器可以在编译时对代码进行优化，如方法内联、常量折叠等，以提高执行效率。
+而反射调用是在运行时动态解析的，编译器无法对其进行类似的优化，导致执行速度相对较慢。</li>
+<li>动态查找和安全检查： 反射允许代码在运行时动态获取类的信息、调用方法和访问字段，甚至能够绕过访问控制。
+因此每次反射调用都需要在运行时进行类信息的查找和安全性检查，这些额外的步骤增加了方法调用的开销，使得反射相比直接调用更为缓慢。</li>
+</ol>
+<p>反射适合于那些需要在运行时动态加载类、调用未知类的方法或访问私有成员的情况。在性能要求严格的地方，尽量避免使用反射。
+如果需要多次反射调用，尽量将反射操作放在静态方法或静态初始化块中，来减少实例化对象的开销，避免重复的反射查找。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Method</span><span class="w"> </span><span class="n">myMethod</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">static</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">myMethod</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MyClass</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredMethod</span><span class="p">(</span><span class="s">&#34;methodName&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">myMethod</span><span class="p">.</span><span class="na">setAccessible</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w"> </span><span class="c1">// 如果是私有方法，需要设置访问权限</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">NoSuchMethodException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">invokeMyMethod</span><span class="p">()</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InvocationTargetException</span><span class="p">,</span><span class="w"> </span><span class="n">IllegalAccessException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">myMethod</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="反射原理">反射原理</h2>
+<p>反射的核心是<code>java.lang.reflect</code>包，该包中包含了用于反射操作的类和接口，如<code>Class</code>、<code>Field</code>、<code>Method</code>、<code>Constructor</code>等。反射主要依赖于<code>Class</code>对象来进行操作。
+Java反射的本质是JVM得到<code>class</code>对象之后，再通过<code>class</code>对象进行&quot;反编译&quot;，从而获取对象的各种信息。描述反射为“反编译”可能不太准确，因为反射并不是将字节码重新转换为源代码。实际上，反射是在运行时通过Class对象来查询和操作已加载的类的结构信息。</p>
+<p>反射基本原理大致可分为以下几个步骤：</p>
+<ol>
+<li>JVM的类加载机制负责将类的字节码从不同的源，如<code>.class</code>文件、<code>JAR</code>包等，加载到内存中，并将其转化为可以在JVM上运行的Class对象。反射依赖于JVM的类加载机制来获取类的结构信息并进行操作。</li>
+<li>当使用反射时，首先需要获取类的Class对象。每个类在 JVM 中加载后，都会有一个对应的Class对象。这个对象包含了类的所有信息，包括类的结构（字段、方法、构造函数）、注解、泛型信息等。
+反射的第一步是获取这个Class对象，可以通过类名、对象实例的<code>getClass()</code>方法或者类的字面常量<code>.class</code>来获取。</li>
+<li>通过Class对象，可以使用反射API来访问类的字段、方法和构造函数。实际上，反射是在运行时通过Class对象来查询和操作已加载的类的结构信息。</li>
+<li>在具体实现上，Java反射依赖于<code>java.lang.reflect</code>包中的一系列类和接口。这些类和接口提供了访问和操作类结构的方法，例如<code>Field</code>、<code>Method</code>、<code>Constructor</code>等。</li>
+</ol>
+<h2 id="反射应用场景">反射应用场景</h2>
+<p>反射在Java编程中有广泛的应用场景。它主要用于动态加载类、运行时获取和操作类的信息，以及实现灵活的编程逻辑。
+通过反射，可以实现诸如依赖注入框架，如<code>Spring</code>、ORM框架，如<code>Hibernate</code>、动态代理、自定义注解处理器、插件化系统等功能。
+这些特性使得Java程序能够在运行时动态适应不同的需求和环境，提高了代码的灵活性和可维护性。</p>
+<h3 id="反射与注解">反射与注解</h3>
+<p>反射可以在运行时动态地获取和解析类、方法、字段上的注解信息。利用这个特性我们可以根据注解的内容来实现不同的逻辑，例如自定义的业务规则、权限控制等。</p>
+<p>反射在自定义注解处理器中特别有用，可以通过反射获取类、方法的信息，并根据注解信息生成代码或者进行其他处理。
+这种方式被广泛应用于框架和工具的开发中，例如<code>Spring</code>框架中的各种注解处理器。自定义一个注解体会一下。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="c1">// 定义一个注解</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Retention</span><span class="p">(</span><span class="n">RetentionPolicy</span><span class="p">.</span><span class="na">RUNTIME</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Target</span><span class="p">(</span><span class="n">ElementType</span><span class="p">.</span><span class="na">METHOD</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@interface</span><span class="w"> </span><span class="n">MyAnnotation</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="nf">value</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="c1">// 使用注解的类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">class</span> <span class="nc">MyClass</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@MyAnnotation</span><span class="p">(</span><span class="s">&#34;Hello Annotation&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">myMethod</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Method with annotation&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ReflectionAndAnnotationExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MyClass</span><span class="w"> </span><span class="n">obj</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MyClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">obj</span><span class="p">.</span><span class="na">getClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取方法上的注解信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">clazz</span><span class="p">.</span><span class="na">getDeclaredMethod</span><span class="p">(</span><span class="s">&#34;myMethod&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MyAnnotation</span><span class="w"> </span><span class="n">annotation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">method</span><span class="p">.</span><span class="na">getAnnotation</span><span class="p">(</span><span class="n">MyAnnotation</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">annotation</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Annotation value: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">annotation</span><span class="p">.</span><span class="na">value</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 使用反射调用带有注解的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="反射与枚举">反射与枚举</h3>
+<p>反射不能用于创建枚举类型的对象。因为枚举类型是单例的，每个枚举常量在Java虚拟机中只有一个实例。通过反射创建新的枚举实例会破坏枚举类型的单例性质。
+Java语言规范明确规定了枚举类型的创建和管理方式，禁止反射机制创建新的枚举实例，来确保枚举类型的安全性和一致性。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">enum</span><span class="w"> </span><span class="n">Day</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SUNDAY</span><span class="p">,</span><span class="w"> </span><span class="n">MONDAY</span><span class="p">,</span><span class="w"> </span><span class="n">TUESDAY</span><span class="p">,</span><span class="w"> </span><span class="n">WEDNESDAY</span><span class="p">,</span><span class="w"> </span><span class="n">THURSDAY</span><span class="p">,</span><span class="w"> </span><span class="n">FRIDAY</span><span class="p">,</span><span class="w"> </span><span class="n">SATURDAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">EnumReflectionExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取枚举类型的构造方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Constructor</span><span class="o">&lt;</span><span class="n">Day</span><span class="o">&gt;</span><span class="w"> </span><span class="n">constructor</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Day</span><span class="p">.</span><span class="na">class</span><span class="p">.</span><span class="na">getDeclaredConstructor</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 尝试通过反射调用构造方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">constructor</span><span class="p">.</span><span class="na">setAccessible</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Day</span><span class="w"> </span><span class="n">newDay</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">constructor</span><span class="p">.</span><span class="na">newInstance</span><span class="p">(</span><span class="s">&#34;NEW_DAY&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">7</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;New Day: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">newDay</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 捕获并打印异常信息</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">java.lang.NoSuchMethodException: Day.&lt;init&gt;(java.lang.String, int)
+</span></span><span class="line"><span class="cl">    at java.lang.Class.getDeclaredConstructor0(Native Method)
+</span></span><span class="line"><span class="cl">    at java.lang.Class.getDeclaredConstructor(Class.java:2178)
+</span></span><span class="line"><span class="cl">    at EnumReflectionExample.main(EnumReflectionExample.java:11)
+</span></span></code></pre></div><p>具体的原因是在<code>Constructor</code>类中的<code>newInstance</code>方法，枚举类无法通过反射来创建对象，原因是<code>newInstance</code>方法加了判断如果是枚举类就抛出异常。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@CallerSensitive</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">newInstance</span><span class="p">(</span><span class="n">Object</span><span class="w"> </span><span class="p">...</span><span class="w"> </span><span class="n">initargs</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">throws</span><span class="w"> </span><span class="n">InstantiationException</span><span class="p">,</span><span class="w"> </span><span class="n">IllegalAccessException</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">           </span><span class="n">IllegalArgumentException</span><span class="p">,</span><span class="w"> </span><span class="n">InvocationTargetException</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">override</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">Reflection</span><span class="p">.</span><span class="na">quickCheckMemberAccess</span><span class="p">(</span><span class="n">clazz</span><span class="p">,</span><span class="w"> </span><span class="n">modifiers</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">caller</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Reflection</span><span class="p">.</span><span class="na">getCallerClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">checkAccess</span><span class="p">(</span><span class="n">caller</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">modifiers</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">((</span><span class="n">clazz</span><span class="p">.</span><span class="na">getModifiers</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">Modifier</span><span class="p">.</span><span class="na">ENUM</span><span class="p">)</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;Cannot reflectively create enum objects&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ConstructorAccessor</span><span class="w"> </span><span class="n">ca</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">constructorAccessor</span><span class="p">;</span><span class="w">   </span><span class="c1">// read volatile</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ca</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ca</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">acquireConstructorAccessor</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">T</span><span class="w"> </span><span class="n">inst</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">T</span><span class="p">)</span><span class="w"> </span><span class="n">ca</span><span class="p">.</span><span class="na">newInstance</span><span class="p">(</span><span class="n">initargs</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">inst</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>除了不能创建枚举类的对象外，反射还是能够调用枚举类的方法的。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">enum</span><span class="w"> </span><span class="n">Day</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">SUNDAY</span><span class="p">,</span><span class="w"> </span><span class="n">MONDAY</span><span class="p">,</span><span class="w"> </span><span class="n">TUESDAY</span><span class="p">,</span><span class="w"> </span><span class="n">WEDNESDAY</span><span class="p">,</span><span class="w"> </span><span class="n">THURSDAY</span><span class="p">,</span><span class="w"> </span><span class="n">FRIDAY</span><span class="p">,</span><span class="w"> </span><span class="n">SATURDAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printMessage</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;Today is &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">name</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">EnumReflectionExample</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取枚举常量</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Day</span><span class="w"> </span><span class="n">day</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Day</span><span class="p">.</span><span class="na">SUNDAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取枚举类的 Class 对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">day</span><span class="p">.</span><span class="na">getClass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 获取并调用枚举类的方法</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Method</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">clazz</span><span class="p">.</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;printMessage&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">method</span><span class="p">.</span><span class="na">invoke</span><span class="p">(</span><span class="n">day</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="反射与泛型">反射与泛型</h3>
+<p>Java中的泛型是通过类型擦除来实现的，这意味着泛型信息只在编译期间存在，而在运行时则被擦除。所以反射在运行时无法直接获取具体的泛型类型信息。</p>
+<p>类型擦除是Java泛型的一种实现机制，目的是保持与旧版本的兼容性。在编译过程中，泛型类型被替换为其非泛型上限，通常是<code>Object</code>类，并在需要时插入类型转换。
+这样Java编译器在编译期间进行类型检查，而在运行时不保留泛型类型信息。</p>
+<p>通过反射可以绕过Java泛型的类型检查，这利用了Java泛型的类型擦除机制。在编译时，泛型类型被擦除，实际操作的对象是原始类型<code>Object</code>。
+这使得在运行时可以向泛型集合中插入不同类型的元素。但这种做法会导致类型安全性问题，所以在实际开发中应谨慎使用。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="w"> </span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;</span><span class="n">Integer</span><span class="o">&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">  </span><span class="c1">//这样调用 add 方法只能存储整形，因为泛型类型的实例为 Integer</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">list</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getMethod</span><span class="p">(</span><span class="s">&#34;add&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="p">.</span><span class="na">class</span><span class="p">).</span><span class="na">invoke</span><span class="p">(</span><span class="n">list</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;string&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">list</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">list</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">));</span><span class="c1">// 1 string</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="反射与框架">反射与框架</h3>
+<p>反射在许多Java框架中起着至关重要的作用，它使得框架能够在运行时动态地操作对象、调用方法和访问字段。
+例如，Spring的核心功能之一是依赖注入，就是利用反射动态地创建和注入对象。Spring使用反射来调用构造函数、设置字段和调用方法。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">MyRepository</span><span class="w"> </span><span class="n">myRepository</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>在<code>@Autowired</code>注解文档注释上面，可以看到与之息息相关的一个类<code>AutowiredAnnotationBeanPostProcessor</code>，即<code>@Autowired</code>后置处理器。
+看到该类实现了<code>MergedBeanDefinitionPostProcessor</code>接口，在<code>postProcessMergedBeanDefinition</code>方法上打一个断点，就可以看到<code>@Autowired</code>的调用栈。</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="cm">/*
+</span></span></span><span class="line"><span class="cl"><span class="cm"> * @see AutowiredAnnotationBeanPostProcessor
+</span></span></span><span class="line"><span class="cl"><span class="cm"> */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Target</span><span class="p">({</span><span class="n">ElementType</span><span class="p">.</span><span class="na">CONSTRUCTOR</span><span class="p">,</span><span class="w"> </span><span class="n">ElementType</span><span class="p">.</span><span class="na">METHOD</span><span class="p">,</span><span class="w"> </span><span class="n">ElementType</span><span class="p">.</span><span class="na">PARAMETER</span><span class="p">,</span><span class="w"> </span><span class="n">ElementType</span><span class="p">.</span><span class="na">FIELD</span><span class="p">,</span><span class="w"> </span><span class="n">ElementType</span><span class="p">.</span><span class="na">ANNOTATION_TYPE</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Retention</span><span class="p">(</span><span class="n">RetentionPolicy</span><span class="p">.</span><span class="na">RUNTIME</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Documented</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="nd">@interface</span><span class="w"> </span><span class="n">Autowired</span><span class="p">{}</span><span class="w">
+</span></span></span></code></pre></div><p><code>@Autowired</code>注解调用栈：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">AbstractApplicationContext.refresh(容器初始化)
+</span></span><span class="line"><span class="cl">    ---&gt; registerBeanPostProcessors (注册AutowiredAnnotationBeanPostProcessor) 
+</span></span><span class="line"><span class="cl">    ---&gt; finishBeanFactoryInitialization
+</span></span><span class="line"><span class="cl">    ---&gt; AbstractAutowireCapableBeanFactory.doCreateBean
+</span></span><span class="line"><span class="cl">    ---&gt; AbstractAutowireCapableBeanFactory.applyMergedBeanDefinitionPostProcessors
+</span></span><span class="line"><span class="cl">    ---&gt; MergedBeanDefinitionPostProcessor.postProcessMergedBeanDefinition
+</span></span><span class="line"><span class="cl">    ---&gt; AutowiredAnnotationBeanPostProcessor.findAutowiringMetadata
+</span></span></code></pre></div><p>核心调用：</p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">postProcessMergedBeanDefinition
+</span></span><span class="line"><span class="cl">    ---&gt;findAutowiringMetadata
+</span></span><span class="line"><span class="cl">    ---&gt;buildAutowiringMetadata
+</span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessMergedBeanDefinition</span><span class="p">(</span><span class="n">RootBeanDefinition</span><span class="w"> </span><span class="n">beanDefinition</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">beanType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">beanName</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 调用 findAutowiringMetadata</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">InjectionMetadata</span><span class="w"> </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">findAutowiringMetadata</span><span class="p">(</span><span class="n">beanName</span><span class="p">,</span><span class="w"> </span><span class="n">beanType</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">metadata</span><span class="p">.</span><span class="na">checkConfigMembers</span><span class="p">(</span><span class="n">beanDefinition</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">InjectionMetadata</span><span class="w"> </span><span class="nf">findAutowiringMetadata</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">beanName</span><span class="p">,</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="p">,</span><span class="w"> </span><span class="nd">@Nullable</span><span class="w"> </span><span class="n">PropertyValues</span><span class="w"> </span><span class="n">pvs</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Fall back to class name as cache key, for backwards compatibility with custom callers.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="n">cacheKey</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">hasLength</span><span class="p">(</span><span class="n">beanName</span><span class="p">)</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">beanName</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">clazz</span><span class="p">.</span><span class="na">getName</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// Quick check on the concurrent map first, with minimal locking.</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">InjectionMetadata</span><span class="w"> </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">injectionMetadataCache</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">cacheKey</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">InjectionMetadata</span><span class="p">.</span><span class="na">needsRefresh</span><span class="p">(</span><span class="n">metadata</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">synchronized</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">injectionMetadataCache</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">injectionMetadataCache</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">cacheKey</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">InjectionMetadata</span><span class="p">.</span><span class="na">needsRefresh</span><span class="p">(</span><span class="n">metadata</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">metadata</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="n">metadata</span><span class="p">.</span><span class="na">clear</span><span class="p">(</span><span class="n">pvs</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="c1">// 调用buildAutowiringMetadata</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buildAutowiringMetadata</span><span class="p">(</span><span class="n">clazz</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">this</span><span class="p">.</span><span class="na">injectionMetadataCache</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">cacheKey</span><span class="p">,</span><span class="w"> </span><span class="n">metadata</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">metadata</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">private</span><span class="w"> </span><span class="n">InjectionMetadata</span><span class="w"> </span><span class="nf">buildAutowiringMetadata</span><span class="p">(</span><span class="kd">final</span><span class="w"> </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">clazz</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">LinkedList</span><span class="o">&lt;</span><span class="n">InjectionMetadata</span><span class="p">.</span><span class="na">InjectedElement</span><span class="o">&gt;</span><span class="w"> </span><span class="n">elements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Class</span><span class="o">&lt;?&gt;</span><span class="w"> </span><span class="n">targetClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">clazz</span><span class="p">;</span><span class="c1">//需要处理的目标类</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;</span><span class="n">InjectionMetadata</span><span class="p">.</span><span class="na">InjectedElement</span><span class="o">&gt;</span><span class="w"> </span><span class="n">currElements</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o">&lt;&gt;</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 通过反射获取该类所有的字段，并遍历每一个字段，并通过方法findAutowiredAnnotation遍历每一个字段的所用注解，</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 如果用autowired修饰了，则返回auotowired相关属性</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReflectionUtils</span><span class="p">.</span><span class="na">doWithLocalFields</span><span class="p">(</span><span class="n">targetClass</span><span class="p">,</span><span class="w"> </span><span class="n">field</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">AnnotationAttributes</span><span class="w"> </span><span class="n">ann</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">findAutowiredAnnotation</span><span class="p">(</span><span class="n">field</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ann</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="c1">//校验autowired注解是否用在了static方法上</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Modifier</span><span class="p">.</span><span class="na">isStatic</span><span class="p">(</span><span class="n">field</span><span class="p">.</span><span class="na">getModifiers</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">logger</span><span class="p">.</span><span class="na">isWarnEnabled</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">logger</span><span class="p">.</span><span class="na">warn</span><span class="p">(</span><span class="s">&#34;Autowired annotation is not supported on static fields: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">field</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="c1">//判断是否指定了required</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">boolean</span><span class="w"> </span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">determineRequiredStatus</span><span class="p">(</span><span class="n">ann</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">currElements</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">AutowiredFieldElement</span><span class="p">(</span><span class="n">field</span><span class="p">,</span><span class="w"> </span><span class="n">required</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 和上面一样的逻辑，但是是通过反射处理类的method</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ReflectionUtils</span><span class="p">.</span><span class="na">doWithLocalMethods</span><span class="p">(</span><span class="n">targetClass</span><span class="p">,</span><span class="w"> </span><span class="n">method</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">Method</span><span class="w"> </span><span class="n">bridgedMethod</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BridgeMethodResolver</span><span class="p">.</span><span class="na">findBridgedMethod</span><span class="p">(</span><span class="n">method</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">BridgeMethodResolver</span><span class="p">.</span><span class="na">isVisibilityBridgeMethodPair</span><span class="p">(</span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">bridgedMethod</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">AnnotationAttributes</span><span class="w"> </span><span class="n">ann</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">findAutowiredAnnotation</span><span class="p">(</span><span class="n">bridgedMethod</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ann</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">method</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">ClassUtils</span><span class="p">.</span><span class="na">getMostSpecificMethod</span><span class="p">(</span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">Modifier</span><span class="p">.</span><span class="na">isStatic</span><span class="p">(</span><span class="n">method</span><span class="p">.</span><span class="na">getModifiers</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">logger</span><span class="p">.</span><span class="na">isWarnEnabled</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">logger</span><span class="p">.</span><span class="na">warn</span><span class="p">(</span><span class="s">&#34;Autowired annotation is not supported on static methods: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">method</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">return</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">method</span><span class="p">.</span><span class="na">getParameterCount</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">logger</span><span class="p">.</span><span class="na">isWarnEnabled</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="n">logger</span><span class="p">.</span><span class="na">warn</span><span class="p">(</span><span class="s">&#34;Autowired annotation should only be used on methods with parameters: &#34;</span><span class="w"> </span><span class="o">+</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                </span><span class="n">method</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="kt">boolean</span><span class="w"> </span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">determineRequiredStatus</span><span class="p">(</span><span class="n">ann</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">PropertyDescriptor</span><span class="w"> </span><span class="n">pd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeanUtils</span><span class="p">.</span><span class="na">findPropertyForMethod</span><span class="p">(</span><span class="n">bridgedMethod</span><span class="p">,</span><span class="w"> </span><span class="n">clazz</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">currElements</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">AutowiredMethodElement</span><span class="p">(</span><span class="n">method</span><span class="p">,</span><span class="w"> </span><span class="n">required</span><span class="p">,</span><span class="w"> </span><span class="n">pd</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 用@Autowired修饰的注解可能不止一个，因此都加在currElements这个容器里面，一起处理		</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">elements</span><span class="p">.</span><span class="na">addAll</span><span class="p">(</span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">currElements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">targetClass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">targetClass</span><span class="p">.</span><span class="na">getSuperclass</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">targetClass</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">targetClass</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">Object</span><span class="p">.</span><span class="na">class</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InjectionMetadata</span><span class="p">(</span><span class="n">clazz</span><span class="p">,</span><span class="w"> </span><span class="n">elements</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><p>通过上面的源码，可以看到Spring在运行时通过反射查找<code>@Autowired</code>注解，并自动注入相关字段。
+Spring框架利用反射遍历目标类及其超类的所有字段和方法，查找并收集所有使用了<code>@Autowired</code>注解的元素。对于每个字段和方法，首先通过反射获取注解信息，如果字段或方法被<code>@Autowired</code>注解修饰且符合条件（如非静态），则将其封装成对应的注入元素（<code>AutowiredFieldElement</code>或<code>AutowiredMethodElement</code>）并添加到当前元素列表中。
+最后，这些注入元素会被封装到<code>InjectionMetadata</code>对象中，并用于实际的依赖注入过程，从而实现Spring的自动注入功能。</p>
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diff --git "a/docs/posts/javakeyword/strictfp\345\205\263\351\224\256\345\255\227/index.html" "b/docs/posts/javakeyword/strictfp\345\205\263\351\224\256\345\255\227/index.html"
new file mode 100644
index 00000000..674d76a2
--- /dev/null
+++ "b/docs/posts/javakeyword/strictfp\345\205\263\351\224\256\345\255\227/index.html"
@@ -0,0 +1,342 @@
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diff --git "a/docs/posts/javakeyword/transient\345\205\263\351\224\256\345\255\227/index.html" "b/docs/posts/javakeyword/transient\345\205\263\351\224\256\345\255\227/index.html"
new file mode 100644
index 00000000..674d76a2
--- /dev/null
+++ "b/docs/posts/javakeyword/transient\345\205\263\351\224\256\345\255\227/index.html"
@@ -0,0 +1,342 @@
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+    }).showWidget();
+
+    function addDarkmodeWidget(){
+        const hours = new Date().getHours();
+        if (hours >= 19 || hours <= 5){
+            new Darkmode({
+                right: '32px', 
+                bottom: 'unset', 
+                
+                time: '0.3s', 
+                mixColor: '#f7f7f7', 
+                backgroundColor: '#f7f7f7', 
+                buttonColorDark: '#212121', 
+                buttonColorLight: '#f7f7f7', 
+                saveInCookies: false, 
+                autoMatchOsTheme: true 
+            }).toggle();
+        }
+    }
+    
+    
+</script>
+
+
+
+
+
+
+
+
+
+</body>
+
+</html>
\ No newline at end of file
diff --git a/docs/posts/spring/java-spring/index.html b/docs/posts/spring/java-spring/index.html
index 9d09d978..66296952 100644
--- a/docs/posts/spring/java-spring/index.html
+++ b/docs/posts/spring/java-spring/index.html
@@ -2471,7 +2471,7 @@ <h4 id="finishbeanfactoryinitialization">finishBeanFactoryInitialization</h4>
 </span></span><span class="line"><span class="cl">   --&gt;AbstractAdvisorAutoProxyCreator.findEligibleAdvisors
 </span></span><span class="line"><span class="cl">   --&gt;AbstractAdvisorAutoProxyCreator.findCandidateAdvisors
 </span></span><span class="line"><span class="cl">   --&gt;BeanFactoryAdvisorRetrievalHelper.findAdvisorBeans
-</span></span></code></pre></div><p>BeanFactoryAdvisorRetrievalHelper这个类是一个Spring AOP内部工具类，用来从Bean容器中获取所有Spring的Advisor Bean。
+</span></span></code></pre></div><p><code>BeanFactoryAdvisorRetrievalHelper</code>这个类是一个Spring AOP内部工具类，用来从Bean容器中获取所有Spring的Advisor Bean。
 该工具内部使用了缓存机制，虽然公开的查找方法可能会被调用多次，但并不是每次都会真正查找，而是会利用缓存。</p>
 <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Advisor</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">findAdvisorBeans</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
 </span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="c1">//cachedAdvisorBeanNames是advisor名称的缓存</span><span class="w">
@@ -2995,7 +2995,7 @@ <h3 id="spring事务工作原理">Spring事务工作原理</h3>
 </span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
 </span></span></span></code></pre></div><p><code>invokeWithinTransaction</code>方法是<code>TransactionInterceptor</code>类中的核心方法，它负责在执行目标方法时管理事务的生命周期。首先该方法通过<code>getTransactionAttributeSource()</code>获取事务属性源，进而确定当前方法是否需要事务支持。
 接着根据获取的事务属性，选择合适的事务管理器，并生成一个方法标识以记录当前事务的上下文信息。在方法执行前，会检查是否需要开启新的事务，并在事务环境中执行目标方法的逻辑。
-如果方法执行过程中出现异常，事务管理器会回滚事务以保证数据一致性，否则在方法执行成功后，事务管理器将提交事务。最后无论方法执行结果如何，都会清理事务相关的信息，释放资源并恢复状态，来保证事务管理的完整性和有效性</p>
+如果方法执行过程中出现异常，事务管理器会回滚事务以保证数据一致性，否则在方法执行成功后，事务管理器将提交事务。最后无论方法执行结果如何，都会清理事务相关的信息，释放资源并恢复状态，来保证事务管理的完整性和有效性。</p>
 <p>简而言之，当一个方法使用了<code>@Transactional</code>注解，在程序运行时，JVM为该Bean创建一个代理对象，并且在调用目标方法的时候进行使用<code>TransactionInterceptor</code>拦截，代理对象负责在调用目标方法之前开启事务，然后执行方法的逻辑。
 方法执行成功，则提交事务，如果执行方法中出现异常，则回滚事务。同时Spring利用<code>ThreadLocal</code>会将事务资源（如数据库连接）与当前线程绑定，以确保在同一事务中共享资源，这些资源在事务提交或回滚时会被清理。</p>
 </div>
diff --git a/docs/posts/toy/pay-code/index.html b/docs/posts/toy/pay-code/index.html
new file mode 100644
index 00000000..0b8237c8
--- /dev/null
+++ b/docs/posts/toy/pay-code/index.html
@@ -0,0 +1,3106 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="author" content="whitepure" />
+	
+	
+	
+	<title>Java整合支付功能 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="结构 完整代码：https://gitee.com/gitee_pikaqiu/easy-archetype pom.xml &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.alipay.sdk&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;alipay-sdk-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;4.9.9&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt;" />
+    
+
+    
+    
+    <meta name="keywords" content="whitepure博客, whiteppure, whitepure, 李济芝, Java, 博客, 技术博客" />
+    
+
+	
+
+    <link rel="shortcut icon" href="https://whiteppure.github.io/iblog/images/favicon.ico" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/normalize.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/animate.min.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/zozo.css" />
+	<link rel="stylesheet" type="text/css" media="screen" href="https://cdn.jsdelivr.net/npm/remixicon@2.5.0/fonts/remixicon.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/highlight.css" />
+
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/toc.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/search.css" />
+    <link rel="stylesheet" type="text/css" media="screen" href="https://whiteppure.github.io/iblog/css/img.css" />
+
+    
+    
+</head>
+
+<body>
+    <div class="post-password">
+        
+    </div>
+
+    
+    
+    
+
+
+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%93%e6%9e%84">
+                    结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#pomxml">
+                    pom.xml
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#applicationyml">
+                    application.yml
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%ac%e5%85%b1%e9%83%a8%e5%88%86">
+                    公共部分
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payservice">
+                    PayService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payrefundable">
+                    PayRefundAble
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payorderqueryable">
+                    PayOrderQueryAble
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payordercloseable">
+                    PayOrderCloseAble
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#paymentable">
+                    PaymentAble
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#abstractpayservice">
+                    AbstractPayService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#commonpayrequest">
+                    CommonPayRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payplatformtypeenum">
+                    PayPlatformTypeEnum
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payfacade">
+                    PayFacade
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payfacadeimpl">
+                    PayFacadeImpl
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#payexception">
+                    PayException
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e6%94%af%e4%bb%98%e5%ae%9d">
+                    支付宝
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayrefundservice">
+                    AlipayRefundService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipaypayorderqueryservice">
+                    AlipayPayOrderQueryService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipaypaymentservice">
+                    AlipayPaymentService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayordercloseservice">
+                    AlipayOrderCloseService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#aliapp">
+                    AliApp
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alih5">
+                    AliH5
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipc">
+                    AliPc
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayordercloserequest">
+                    AlipayOrderCloseRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipaypaymentrequest">
+                    AlipayPaymentRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayqueryorderrequest">
+                    AlipayQueryOrderRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayrefundrequest">
+                    AlipayRefundRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayconfiguration">
+                    AlipayConfiguration
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayproperties">
+                    AlipayProperties
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%be%ae%e4%bf%a1">
+                    微信
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayrefundservice">
+                    WxpayRefundService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpaypaymentservice">
+                    WxpayPaymentService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayorderqueryservice">
+                    WxpayOrderQueryService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayordercloseservice">
+                    WxpayOrderCloseService
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxapp">
+                    WxApp
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxh5">
+                    WxH5
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxjsapi">
+                    WxJsapi
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxnative">
+                    WxNative
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxorderqueryrequest">
+                    WxOrderQueryRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayordercloserequest">
+                    WxpayOrderCloseRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpaypaymentrequest">
+                    WxpayPaymentRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxrefundrequest">
+                    WxRefundRequest
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayconfiguration">
+                    WxpayConfiguration
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayproperties">
+                    WxpayProperties
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b0%83%e7%94%a8%e6%b5%8b%e8%af%95">
+                    调用测试
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#alipayexamplecontroller">
+                    AlipayExampleController
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#wxpayexamplecontroller">
+                    WxpayExampleController
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#paytestcontroller">
+                    PayTestController
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+
+    </div>
+
+</div>
+
+
+
+    
+
+    
+    <div class="main animate__animated animate__fadeInDown" id="main_content">
+        <div class="nav_container animated fadeInDown">
+    <div class="site_nav" id="site_nav">
+        <ul><li class="">
+                <a href="https://whiteppure.github.io/iblog/">首页</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/posts/">归档</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/tags/">标签</a>
+            </li><li class="">
+                <a href="https://whiteppure.github.io/iblog/about/">关于</a>
+            </li>
+        </ul>
+    </div>
+    <div class="menu_icon">
+        <a id="menu_icon"><i class="ri-menu-line"></i></a>
+    </div>
+</div>
+        <div id="post_header" class="header animated fadeInDown">
+    <div class="site_title_container">
+        <div class="site_title">
+            <h1>
+                <a href="https://whiteppure.github.io/iblog/">
+                    <span>脚踏实地</span>
+                </a>
+            </h1>
+        </div>
+        <div class="description">
+            <p class="sub_title">
+                
+            </p>
+
+            
+            <div class="my_socials">
+                
+                    
+                    <a href="https://github.com/whiteppure/" title="github" target="_blank">
+                        <i class="ri-github-fill"></i>
+                    </a>
+                    
+                
+                <a href="https://whiteppure.github.io/iblog/index.xml" type="application/rss+xml" title="rss" target="_blank">
+                    <i class="ri-rss-fill"></i>
+                </a>
+                
+                
+                <span id="sys_function" class="sys_function display_none">
+                    <a id="export_pdf"  title="导出pdf" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    <a id="export_pic" title="导出图片" style="border: none; background-color: #ffffff; cursor: pointer; margin-left: 10px">
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+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
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+                        <h2 id="post_single_title">Java整合支付功能</h2>
+                        <span id="post_page_title_date" class="date">2023.08.10</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="结构">结构</h2>
+<p><img alt="整合支付功能" src="/iblog/posts/annex/images/essays/%E6%95%B4%E5%90%88%E6%94%AF%E4%BB%98%E5%8A%9F%E8%83%BD-01.jpg"></p>
+<p>完整代码：<a href="https://gitee.com/gitee_pikaqiu/easy-archetype">https://gitee.com/gitee_pikaqiu/easy-archetype</a></p>
+<h2 id="pomxml">pom.xml</h2>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-xml" data-lang="xml"><span class="line"><span class="cl"><span class="nt">&lt;dependencies&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-web<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-test<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;scope&gt;</span>test<span class="nt">&lt;/scope&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.projectlombok<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>lombok<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;optional&gt;</span>true<span class="nt">&lt;/optional&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>cn.hutool<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>hutool-all<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>5.8.11<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>com.alipay.sdk<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>alipay-sdk-java<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>4.9.9<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>com.github.binarywang<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>weixin-java-pay<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>4.5.0<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl"><span class="nt">&lt;/dependencies&gt;</span>
+</span></span></code></pre></div><h2 id="applicationyml">application.yml</h2>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="nt">server</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">port</span><span class="p">:</span><span class="w"> </span><span class="m">8080</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">pay</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">wechat</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#微信公众号或者小程序等的appid</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">appId</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#微信支付商户号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">mchId</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#微信支付商户密钥</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">mchKey</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#服务商模式下的子商户公众账号ID</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">subAppId</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c">#服务商模式下的子商户号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">subMchId</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># p12证书的位置，可以指定绝对路径，也可以指定类路径（以classpath:开头）</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">keyPath</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">alipay</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 应用ID,您的APPID，收款账号既是您的APPID对应支付宝账号</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">appId</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 商户私钥，您的PKCS8格式RSA2私钥</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">merchantPrivateKey</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 支付宝公钥,查看地址：https://openhome.alipay.com/platform/keyManage.htm 对应APPID下的支付宝公钥。</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">alipayPublicKey</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 服务器异步通知页面路径  需http://格式的完整路径，不能加?id=123这类自定义参数，必须外网可以正常访问</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">notifyUrl</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;http://localhost:8080/ali/paymentNotify&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 页面跳转同步通知页面路径 需http://格式的完整路径，不能加?id=123这类自定义参数，必须外网可以正常访问</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">returnUrl</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;http://localhost:8080/ali/paymentNotify&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 签名方式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">signType</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;RSA2&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 字符编码格式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">charset</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;utf-8&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 格式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">format</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;json&#34;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c"># 支付宝网关</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">gatewayUrl</span><span class="p">:</span><span class="w"> </span><span class="s2">&#34;https://openapi.alipaydev.com/gateway.do&#34;</span><span class="w">
+</span></span></span></code></pre></div><h2 id="公共部分">公共部分</h2>
+<h3 id="payservice">PayService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取支付平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 支付平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付时可能存在的行为; 支付订单 查询订单 生成支付二维码 退款等
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return any
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">apply</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payrefundable">PayRefundAble</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayRefundAble</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payorderqueryable">PayOrderQueryAble</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayOrderQueryAble</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payordercloseable">PayOrderCloseAble</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayOrderCloseAble</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="paymentable">PaymentAble</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PaymentAble</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="abstractpayservice">AbstractPayService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractPayService</span><span class="o">&lt;</span><span class="n">Q</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="p">,</span><span class="n">S</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayService</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">apply</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">payRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Q</span><span class="w"> </span><span class="n">orderInfo</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Q</span><span class="p">)</span><span class="w"> </span><span class="n">payRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 前置处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;开始执行前置处理.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">preprocessing</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="s">&#34;支付前置处理失败,不能继续执行&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;前置处理执行完毕&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;开始执行,请求参数 {}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">S</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">processing</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;执行完毕,响应参数 {}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">result</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 后置处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;开始执行后置处理.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">postprocessing</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;后置处理执行完毕.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 前置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 通过 ; false 不通过
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w">  </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preprocessing</span><span class="p">(</span><span class="n">Q</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 核心处理方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 支付结果
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">S</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">Q</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postprocessing</span><span class="p">(</span><span class="n">Q</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="commonpayrequest">CommonPayRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payplatformtypeenum">PayPlatformTypeEnum</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">enum</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 支付平台</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ALIPAY</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">WECHAT</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payfacade">PayFacade</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PayFacade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付调用接口（指定操作传入class，传入请求参数）
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param &lt;T&gt;       支付操作类型 {@linkplain  PayService}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param orderInfo 订单信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">execute</span><span class="p">(</span><span class="n">Class</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">payClass</span><span class="p">,</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payfacadeimpl">PayFacadeImpl</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PayFacadeImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayFacade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w">  </span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">PayService</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">execute</span><span class="p">(</span><span class="n">Class</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">payClass</span><span class="p">,</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Optional</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">payItem</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">SpringUtil</span><span class="p">.</span><span class="na">getBeansOfType</span><span class="p">(</span><span class="n">payClass</span><span class="p">).</span><span class="na">values</span><span class="p">())</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">stream</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">filter</span><span class="p">(</span><span class="n">item</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">item</span><span class="p">.</span><span class="na">getPayPlatformType</span><span class="p">().</span><span class="na">equals</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">.</span><span class="na">getPayTypeEnum</span><span class="p">()))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">findFirst</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;支付行为[{}],调用平台类型[{}]&#34;</span><span class="p">,</span><span class="n">payClass</span><span class="p">.</span><span class="na">getSimpleName</span><span class="p">(),</span><span class="n">orderInfo</span><span class="p">.</span><span class="na">getPayTypeEnum</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@SuppressWarnings</span><span class="p">(</span><span class="s">&#34;unchecked&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Optional</span><span class="o">&lt;</span><span class="n">PayService</span><span class="o">&gt;</span><span class="w"> </span><span class="n">payService</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">Optional</span><span class="o">&lt;</span><span class="n">PayService</span><span class="o">&gt;</span><span class="p">)</span><span class="w"> </span><span class="n">payItem</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">payService</span><span class="p">.</span><span class="na">isPresent</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">payService</span><span class="p">.</span><span class="na">get</span><span class="p">().</span><span class="na">apply</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;未获取到支付平台类型&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="payexception">PayException</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PayException</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">msg</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">PayException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">msg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">PayException</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">Throwable</span><span class="w"> </span><span class="n">cause</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">message</span><span class="p">,</span><span class="w"> </span><span class="n">cause</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">msg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="支付宝">支付宝</h2>
+<h3 id="alipayrefundservice">AlipayRefundService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayRefundService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="o">&lt;</span><span class="n">AlipayRefundRequest</span><span class="p">,</span><span class="n">AlipayTradeRefundResponse</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayRefundAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradeRefundResponse</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">AlipayRefundRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeRefundRequest</span><span class="w"> </span><span class="n">alipayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayTradeRefundRequest</span><span class="w"> </span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setBizContent</span><span class="p">(</span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeRefundResponse</span><span class="w"> </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">alipayRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">AlipayApiException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">response</span><span class="p">.</span><span class="na">isSuccess</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 退款成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipaypayorderqueryservice">AlipayPayOrderQueryService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayPayOrderQueryService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="o">&lt;</span><span class="n">AlipayQueryOrderRequest</span><span class="p">,</span><span class="n">AlipayTradeQueryResponse</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayOrderQueryAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradeQueryResponse</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">AlipayQueryOrderRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeQueryRequest</span><span class="w"> </span><span class="n">alipayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayTradeQueryRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setBizContent</span><span class="p">(</span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeQueryResponse</span><span class="w"> </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">alipayRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">AlipayApiException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">response</span><span class="p">.</span><span class="na">isSuccess</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 支付成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipaypaymentservice">AlipayPaymentService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayPaymentService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="o">&lt;</span><span class="n">AlipayPaymentRequest</span><span class="p">,</span><span class="w"> </span><span class="n">AlipayTradePagePayResponse</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PaymentAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayProperties</span><span class="w"> </span><span class="n">aliPayProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="n">alipayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setReturnUrl</span><span class="p">(</span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getReturnUrl</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setNotifyUrl</span><span class="p">(</span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getNotifyUrl</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setBizContent</span><span class="p">(</span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayResponse</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">AlipayApiException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayordercloseservice">AlipayOrderCloseService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayOrderCloseService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="o">&lt;</span><span class="n">AlipayOrderCloseRequest</span><span class="p">,</span><span class="n">AlipayTradeCloseResponse</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayOrderCloseAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradeCloseResponse</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">AlipayOrderCloseRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeCloseRequest</span><span class="w"> </span><span class="n">alipayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayTradeCloseRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayRequest</span><span class="p">.</span><span class="na">setBizContent</span><span class="p">(</span><span class="n">JSON</span><span class="p">.</span><span class="na">toJSONString</span><span class="p">(</span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AlipayTradeCloseResponse</span><span class="w"> </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">response</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">alipayRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">AlipayApiException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">response</span><span class="p">.</span><span class="na">isSuccess</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 关闭成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">response</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="aliapp">AliApp</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AliApp</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AlipayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayPaymentRequest</span><span class="p">.</span><span class="na">setProduct_code</span><span class="p">(</span><span class="s">&#34;QUICK_MSECURITY_PAY&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alih5">AliH5</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AliH5</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AlipayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayPaymentRequest</span><span class="p">.</span><span class="na">setProduct_code</span><span class="p">(</span><span class="s">&#34;QUICK_WAP_WAY&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipc">AliPc</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AliPc</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AlipayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">AlipayPaymentRequest</span><span class="w"> </span><span class="n">alipayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">alipayPaymentRequest</span><span class="p">.</span><span class="na">setProduct_code</span><span class="p">(</span><span class="s">&#34;FAST_INSTANT_TRADE_PAY&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">alipayPaymentRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayordercloserequest">AlipayOrderCloseRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayOrderCloseRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 该交易在支付宝系统中的交易流水号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 订单支付时传入的商户订单号,和支付宝交易号不能同时为空。 trade_no,out_trade_no如果同时存在优先取trade_no
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipaypaymentrequest">AlipayPaymentRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayPaymentRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 订单名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subject</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 付款金额
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">total_amount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商品描述
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">body</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 超时时间参数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">timeout_express</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;60m&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 产品编号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">product_code</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayqueryorderrequest">AlipayQueryOrderRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayQueryOrderRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayrefundrequest">AlipayRefundRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayRefundRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付宝交易号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款请求号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_request_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款金额
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refund_amount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">ALIPAY</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayconfiguration">AlipayConfiguration</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Configuration</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@EnableConfigurationProperties</span><span class="p">(</span><span class="n">AlipayProperties</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayConfiguration</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayProperties</span><span class="w"> </span><span class="n">aliPayProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="nf">alipayClient</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultAlipayClient</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getGatewayUrl</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getAppId</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getMerchantPrivateKey</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getFormat</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getCharset</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getAlipayPublicKey</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliPayProperties</span><span class="p">.</span><span class="na">getSignType</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="alipayproperties">AlipayProperties</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@ConfigurationProperties</span><span class="p">(</span><span class="n">prefix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;pay.alipay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayProperties</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 应用ID,您的APPID，收款账号既是您的APPID对应支付宝账号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">appId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户私钥，您的PKCS8格式RSA2私钥
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">merchantPrivateKey</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付宝公钥,查看地址：https://openhome.alipay.com/platform/keyManage.htm 对应APPID下的支付宝公钥。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">alipayPublicKey</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 服务器异步通知页面路径  需http://格式的完整路径，不能加?id=123这类自定义参数，必须外网可以正常访问
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">notifyUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 页面跳转同步通知页面路径 需http://格式的完整路径，不能加?id=123这类自定义参数，必须外网可以正常访问
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">returnUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 签名方式
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">signType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 字符编码格式
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">charset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 格式
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">format</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付宝网关
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">gatewayUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="微信">微信</h2>
+<h3 id="wxpayrefundservice">WxpayRefundService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayRefundService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayRefundAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxRefundRequest</span><span class="w"> </span><span class="n">wxRefundRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">WxRefundRequest</span><span class="p">)</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayRefundRequest</span><span class="w"> </span><span class="n">refundRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayRefundRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setOutRefundNo</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getOutRefundNo</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setRefundAccount</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getRefundAccount</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setRefundDesc</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getRefundDesc</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setRefundFee</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getRefundFee</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setNotifyUrl</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getNotifyUrl</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setRefundFeeType</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getRefundFeeType</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setTransactionId</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getTransactionId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setOutRefundNo</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getOutTradeNo</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">refundRequest</span><span class="p">.</span><span class="na">setTotalFee</span><span class="p">(</span><span class="n">wxRefundRequest</span><span class="p">.</span><span class="na">getTotalFee</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">refund</span><span class="p">(</span><span class="n">refundRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">WxPayException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpaypaymentservice">WxpayPaymentService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayPaymentService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PaymentAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 微信统一下单请求对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">request</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setOutTradeNo</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getOut_trade_no</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setBody</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getBody</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setFeeType</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getFee_type</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setTotalFee</span><span class="p">(</span><span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getTotal_fee</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setSpbillCreateIp</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getSpbill_create_ip</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setNotifyUrl</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getNotify_url</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setProductId</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">valueOf</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">currentTimeMillis</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setTimeExpire</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getTime_expire</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setTimeStart</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getTime_start</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">request</span><span class="p">.</span><span class="na">setProfitSharing</span><span class="p">(</span><span class="s">&#34;Y&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">request</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">unifiedOrder</span><span class="p">(</span><span class="n">buildUnifiedOrderRequest</span><span class="p">((</span><span class="n">WxpayPaymentRequest</span><span class="p">)</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">WxPayException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayorderqueryservice">WxpayOrderQueryService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayOrderQueryService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayOrderQueryAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxOrderQueryRequest</span><span class="w"> </span><span class="n">wxQueryOrder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">WxOrderQueryRequest</span><span class="p">)</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayOrderQueryRequest</span><span class="w"> </span><span class="n">req</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayOrderQueryRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">req</span><span class="p">.</span><span class="na">setSubMchId</span><span class="p">(</span><span class="n">wxQueryOrder</span><span class="p">.</span><span class="na">getSubMchId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">req</span><span class="p">.</span><span class="na">setSubAppId</span><span class="p">(</span><span class="n">wxQueryOrder</span><span class="p">.</span><span class="na">getSubMchAppId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">req</span><span class="p">.</span><span class="na">setOutTradeNo</span><span class="p">(</span><span class="n">wxQueryOrder</span><span class="p">.</span><span class="na">getPayOrderId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayOrderQueryResult</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">queryOrder</span><span class="p">(</span><span class="n">req</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">WxPayException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="s">&#34;微信订单查询异常&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 根据状态判断</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;SUCCESS&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 支付成功</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;USERPAYING&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 支付中，等待用户输入密码</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="s">&#34;CLOSED&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">())</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;REVOKED&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">())</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="s">&#34;PAYERROR&#34;</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">result</span><span class="p">.</span><span class="na">getTradeState</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// CLOSED—已关闭， REVOKED—已撤销(刷卡支付), PAYERROR--支付失败(其他原因，如银行返回失败) 支付失败</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// unknow</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayordercloseservice">WxpayOrderCloseService</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayOrderCloseService</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractPayService</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PayOrderCloseAble</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">Object</span><span class="w"> </span><span class="nf">processing</span><span class="p">(</span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">PayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxpayOrderCloseRequest</span><span class="w"> </span><span class="n">wxOrderInfo</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">WxpayOrderCloseRequest</span><span class="p">)</span><span class="w"> </span><span class="n">orderInfo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayOrderCloseRequest</span><span class="w"> </span><span class="n">wxPayRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayOrderCloseRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayRequest</span><span class="p">.</span><span class="na">setOutTradeNo</span><span class="p">(</span><span class="n">wxOrderInfo</span><span class="p">.</span><span class="na">getOut_trade_no</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayOrderCloseResult</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">closeOrder</span><span class="p">(</span><span class="n">wxPayRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">WxPayException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PayException</span><span class="p">(</span><span class="n">e</span><span class="p">.</span><span class="na">getMessage</span><span class="p">(),</span><span class="w"> </span><span class="n">e</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">result</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayPlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxapp">WxApp</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxApp</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WxpayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setTradeType</span><span class="p">(</span><span class="n">WxPayConstants</span><span class="p">.</span><span class="na">TradeType</span><span class="p">.</span><span class="na">APP</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setOpenid</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getOpenid</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxh5">WxH5</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxH5</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WxpayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setTradeType</span><span class="p">(</span><span class="n">WxPayConstants</span><span class="p">.</span><span class="na">TradeType</span><span class="p">.</span><span class="na">MWEB</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setOpenid</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getOpenid</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxjsapi">WxJsapi</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxJsapi</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WxpayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setTradeType</span><span class="p">(</span><span class="n">WxPayConstants</span><span class="p">.</span><span class="na">TradeType</span><span class="p">.</span><span class="na">JSAPI</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setOpenid</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">.</span><span class="na">getOpenid</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxnative">WxNative</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxNative</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">WxpayPaymentService</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="nf">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">WxpayPaymentRequest</span><span class="w"> </span><span class="n">wxpayOrder</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">buildUnifiedOrderRequest</span><span class="p">(</span><span class="n">wxpayOrder</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">.</span><span class="na">setTradeType</span><span class="p">(</span><span class="n">WxPayConstants</span><span class="p">.</span><span class="na">TradeType</span><span class="p">.</span><span class="na">NATIVE</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayUnifiedOrderRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxorderqueryrequest">WxOrderQueryRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxOrderQueryRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">payOrderId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 特约商户传入</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** 子商户ID **/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subMchId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/** 子账户appID **/</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subMchAppId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayordercloserequest">WxpayOrderCloseRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayOrderCloseRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpaypaymentrequest">WxpayPaymentRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayPaymentRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 公众账号appid
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">appid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mch_id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商品描述
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">body</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 附加数据; 在查询API和支付通知中原样返回，可作为自定义参数使用。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">attach</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号; 要求32个字符内（最少6个字符），只能是数字、大小写字母_-|*且在同一个商户号下唯一
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">out_trade_no</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 总金额(分)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">total_fee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 默认人民币：CNY
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">fee_type</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易起始时间 格式为yyyyMMddHHmmss
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">time_start</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易结束时间 格式为yyyyMMddHHmmss
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">time_expire</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易类型;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * JSAPI -JSAPI支付
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * NATIVE -Native支付
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * APP -APP支付
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">trade_type</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商品ID; trade_type=NATIVE时，此参数必传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">product_id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 用户标识; trade_type=JSAPI时（即JSAPI支付），此参数必传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">openid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 是否分账 不传默认不分账
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;p&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * Y-是，需要分账
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * N-否，不分账
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">profit_sharing</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 回调地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">notify_url</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支持IPV4和IPV6两种格式的IP地址。用户的客户端IP
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">spbill_create_ip</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 随机字符串； 长度要求在32位以内
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">nonce_str</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxrefundrequest">WxRefundRequest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxRefundRequest</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">CommonPayRequest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 微信支付订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">transactionId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 商户退款单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outRefundNo</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 订单金额
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">totalFee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款金额
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">refundFee</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款货币种类
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundFeeType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款资金来源
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundAccount</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款原因
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundDesc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款结果通知url
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">notifyUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="w"> </span><span class="nf">getPayTypeEnum</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">PayPlatformTypeEnum</span><span class="p">.</span><span class="na">WECHAT</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayconfiguration">WxpayConfiguration</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Configuration</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@ConditionalOnClass</span><span class="p">(</span><span class="n">WxPayService</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@EnableConfigurationProperties</span><span class="p">(</span><span class="n">WxpayProperties</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayConfiguration</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WxpayProperties</span><span class="w"> </span><span class="n">properties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@ConditionalOnMissingBean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="nf">wxService</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayConfig</span><span class="w"> </span><span class="n">payConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayConfig</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setAppId</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getAppId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setMchId</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getMchId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setMchKey</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getMchKey</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setSubAppId</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getSubAppId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setSubMchId</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getSubMchId</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setKeyPath</span><span class="p">(</span><span class="n">StringUtils</span><span class="p">.</span><span class="na">trimToNull</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">properties</span><span class="p">.</span><span class="na">getKeyPath</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 可以指定是否使用沙箱环境</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payConfig</span><span class="p">.</span><span class="na">setUseSandboxEnv</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxPayService</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">WxPayServiceImpl</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">wxPayService</span><span class="p">.</span><span class="na">setConfig</span><span class="p">(</span><span class="n">payConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">wxPayService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayproperties">WxpayProperties</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@ConfigurationProperties</span><span class="p">(</span><span class="n">prefix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;pay.wechat&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayProperties</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 设置微信公众号或者小程序等的appid
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">appId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 微信支付商户号
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mchId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 微信支付商户密钥
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">mchKey</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 服务商模式下的子商户公众账号ID，普通模式请不要配置，请在配置文件中将对应项删除
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subAppId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 服务商模式下的子商户号，普通模式请不要配置，最好是请在配置文件中将对应项删除
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">subMchId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * apiclient_cert.p12文件的绝对路径，或者如果放在项目中，请以classpath:开头指定
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">keyPath</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 支付回调地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">payNotifyUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">   * 退款回调地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">   */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundNotifyUrl</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="调用测试">调用测试</h2>
+<h3 id="alipayexamplecontroller">AlipayExampleController</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@RestController</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/example/alipay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AlipayExampleController</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AlipayClient</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 统一下单
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/59da99d0_alipay.trade.page.pay
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/unifiedOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradePagePayResponse</span><span class="w"> </span><span class="nf">unifiedOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradePagePayRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/bff76748_alipay.trade.query
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/queryOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradeQueryResponse</span><span class="w"> </span><span class="nf">queryOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradeQueryRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易退款
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/357441a2_alipay.trade.fastpay
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/refund&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradeRefundResponse</span><span class="w"> </span><span class="nf">refund</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradeRefundRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/357441a2_alipay.trade.fastpay.refund.query
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/refundQuery&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradeFastpayRefundQueryResponse</span><span class="w"> </span><span class="nf">refundQuery</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradeFastpayRefundQueryRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 交易关闭
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址: https://opendocs.alipay.com/open/8dc9ebb3_alipay.trade.close
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.alipay.api.AlipayResponse}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/closeOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AlipayTradeCloseResponse</span><span class="w"> </span><span class="nf">closeOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">AlipayTradeCloseRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">alipayClient</span><span class="p">.</span><span class="na">pageExecute</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="wxpayexamplecontroller">WxpayExampleController</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@RestController</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/example/wxpay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">WxpayExampleController</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">WxPayService</span><span class="w"> </span><span class="n">wxService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 查询订单(详见https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_2)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 该接口提供所有微信支付订单的查询，商户可以通过查询订单接口主动查询订单状态，完成下一步的业务逻辑。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 需要调用查询接口的情况：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * ◆ 当商户后台、网络、服务器等出现异常，商户系统最终未接收到支付通知；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * ◆ 调用支付接口后，返回系统错误或未知交易状态情况；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * ◆ 调用被扫支付API，返回USERPAYING的状态；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * ◆ 调用关单或撤销接口API之前，需确认支付状态；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址：https://api.mch.weixin.qq.com/pay/orderquery
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param transactionId 微信订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param outTradeNo    商户系统内部的订单号，当没提供transactionId时需要传这个。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/queryOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayOrderQueryResult</span><span class="w"> </span><span class="nf">queryOrder</span><span class="p">(</span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">transactionId</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                            </span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">queryOrder</span><span class="p">(</span><span class="n">transactionId</span><span class="p">,</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/queryOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayOrderQueryResult</span><span class="w"> </span><span class="nf">queryOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayOrderQueryRequest</span><span class="w"> </span><span class="n">wxPayOrderQueryRequest</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">queryOrder</span><span class="p">(</span><span class="n">wxPayOrderQueryRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 关闭订单
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 应用场景
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 以下情况需要调用关单接口：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 1. 商户订单支付失败需要生成新单号重新发起支付，要对原订单号调用关单，避免重复支付；
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 2. 系统下单后，用户支付超时，系统退出不再受理，避免用户继续，请调用关单接口。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 注意：订单生成后不能马上调用关单接口，最短调用时间间隔为5分钟。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址：https://api.mch.weixin.qq.com/pay/closeorder
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 是否需要证书：   不需要。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param outTradeNo 商户系统内部的订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/closeOrder/{outTradeNo}&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayOrderCloseResult</span><span class="w"> </span><span class="nf">closeOrder</span><span class="p">(</span><span class="nd">@PathVariable</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">closeOrder</span><span class="p">(</span><span class="n">outTradeNo</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/closeOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayOrderCloseResult</span><span class="w"> </span><span class="nf">closeOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayOrderCloseRequest</span><span class="w"> </span><span class="n">wxPayOrderCloseRequest</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">closeOrder</span><span class="p">(</span><span class="n">wxPayOrderCloseRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 调用统一下单接口，并组装生成支付所需参数对象.
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 统一下单请求参数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param &lt;T&gt;     请使用{@link com.github.binarywang.wxpay.bean.order}包下的类
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 返回 {@link com.github.binarywang.wxpay.bean.order}包下的类对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/createOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">createOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">createOrder</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 统一下单(详见https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_1)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在发起微信支付前，需要调用统一下单接口，获取&#34;预支付交易会话标识&#34;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口地址：https://api.mch.weixin.qq.com/pay/unifiedorder
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象，注意一些参数如appid、mchid等不用设置，方法内会自动从配置对象中获取到（前提是对应配置中已经设置）
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/unifiedOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayUnifiedOrderResult</span><span class="w"> </span><span class="nf">unifiedOrder</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayUnifiedOrderRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">unifiedOrder</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 微信支付-申请退款
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 详见 https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_4
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口链接：https://api.mch.weixin.qq.com/secapi/pay/refund
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param request 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 退款操作结果
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/refund&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayRefundResult</span><span class="w"> </span><span class="nf">refund</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayRefundRequest</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">refund</span><span class="p">(</span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 微信支付-查询退款
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 应用场景：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *  提交退款申请后，通过调用该接口查询退款状态。退款有一定延时，用零钱支付的退款20分钟内到账，
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *  银行卡支付的退款3个工作日后重新查询退款状态。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 详见 https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_5
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 接口链接：https://api.mch.weixin.qq.com/pay/refundquery
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 以下四个参数四选一
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param transactionId 微信订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param outTradeNo    商户订单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param outRefundNo   商户退款单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param refundId      微信退款单号
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 退款信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/refundQuery&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayRefundQueryResult</span><span class="w"> </span><span class="nf">refundQuery</span><span class="p">(</span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">transactionId</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                              </span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                              </span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">outRefundNo</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                                              </span><span class="nd">@RequestParam</span><span class="p">(</span><span class="n">required</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">refundId</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">refundQuery</span><span class="p">(</span><span class="n">transactionId</span><span class="p">,</span><span class="w"> </span><span class="n">outTradeNo</span><span class="p">,</span><span class="w"> </span><span class="n">outRefundNo</span><span class="p">,</span><span class="w"> </span><span class="n">refundId</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款查询
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param wxPayRefundQueryRequest 请求对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 退款信息
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @throws WxPayException
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/refundQuery&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">WxPayRefundQueryResult</span><span class="w"> </span><span class="nf">refundQuery</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">WxPayRefundQueryRequest</span><span class="w"> </span><span class="n">wxPayRefundQueryRequest</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">refundQuery</span><span class="p">(</span><span class="n">wxPayRefundQueryRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 支付回调通知处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/notify/order&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">parseOrderNotifyResult</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">xmlData</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">WxPayOrderNotifyResult</span><span class="w"> </span><span class="n">notifyResult</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">parseOrderNotifyResult</span><span class="p">(</span><span class="n">xmlData</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// TODO 根据自己业务场景需要构造返回对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">WxPayNotifyResponse</span><span class="p">.</span><span class="na">success</span><span class="p">(</span><span class="s">&#34;成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 退款回调通知处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param xmlData
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/notify/refund&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">parseRefundNotifyResult</span><span class="p">(</span><span class="nd">@RequestBody</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">xmlData</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">WxPayRefundNotifyResult</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">parseRefundNotifyResult</span><span class="p">(</span><span class="n">xmlData</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// TODO 根据自己业务场景需要构造返回对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">WxPayNotifyResponse</span><span class="p">.</span><span class="na">success</span><span class="p">(</span><span class="s">&#34;成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 扫码支付回调通知处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@PostMapping</span><span class="p">(</span><span class="s">&#34;/notify/scanpay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">parseScanPayNotifyResult</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">xmlData</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">WxPayException</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">final</span><span class="w"> </span><span class="n">WxScanPayNotifyResult</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">parseScanPayNotifyResult</span><span class="p">(</span><span class="n">xmlData</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// TODO 根据自己业务场景需要构造返回对象</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">WxPayNotifyResponse</span><span class="p">.</span><span class="na">success</span><span class="p">(</span><span class="s">&#34;成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 扫码支付模式一生成二维码的方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 二维码中的内容为链接，形式为：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * weixin://wxpay/bizpayurl?sign=XXXXX&amp;appid=XXXXX&amp;mch_id=XXXXX&amp;product_id=XXXXXX&amp;time_stamp=XXXXXX&amp;nonce_str=XXXXX
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 其中XXXXX为商户需要填写的内容，商户将该链接生成二维码，如需要打印发布二维码，需要采用此格式。商户可调用第三方库生成二维码图片。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文档详见: https://pay.weixin.qq.com/wiki/doc/api/native.php?chapter=6_4
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param productId  产品Id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param logoFile   商户logo图片的文件对象，可以为空
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param sideLength 要生成的二维码的边长，如果为空，则取默认值400
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 生成的二维码的字节数组
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="nf">createScanPayQrcodeMode1</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">productId</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="n">logoFile</span><span class="p">,</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">sideLength</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">wxService</span><span class="p">.</span><span class="na">createScanPayQrcodeMode1</span><span class="p">(</span><span class="n">productId</span><span class="p">,</span><span class="w"> </span><span class="n">logoFile</span><span class="p">,</span><span class="w"> </span><span class="n">sideLength</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 扫码支付模式一生成二维码的方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 二维码中的内容为链接，形式为：
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * weixin://wxpay/bizpayurl?sign=XXXXX&amp;appid=XXXXX&amp;mch_id=XXXXX&amp;product_id=XXXXXX&amp;time_stamp=XXXXXX&amp;nonce_str=XXXXX
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 其中XXXXX为商户需要填写的内容，商户将该链接生成二维码，如需要打印发布二维码，需要采用此格式。商户可调用第三方库生成二维码图片。
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文档详见: https://pay.weixin.qq.com/wiki/doc/api/native.php?chapter=6_4
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * &lt;/pre&gt;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param productId 产品Id
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 生成的二维码URL连接
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span></code></pre></div><h3 id="paytestcontroller">PayTestController</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RestController</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/example/iPay&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PayTestController</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PayFacade</span><span class="w"> </span><span class="n">payFacade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/alipayUnifiedOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">alipayUnifiedOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payFacade</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">PaymentAble</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">new</span><span class="w"> </span><span class="n">AlipayPaymentRequest</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setBody</span><span class="p">(</span><span class="s">&#34;商品描述&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setSubject</span><span class="p">(</span><span class="s">&#34;支付宝测试商品&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setTotal_amount</span><span class="p">(</span><span class="s">&#34;0.1&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setOut_trade_no</span><span class="p">(</span><span class="s">&#34;2023009999999&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;支付宝-支付-交易成功&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/alipayUnifiedOrderNotify&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">alipayUnifiedOrderNotify</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;支付宝-支付回调-交易成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;交易成功！&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/wxUnifiedOrder&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">wxUnifiedOrder</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">payFacade</span><span class="p">.</span><span class="na">execute</span><span class="p">(</span><span class="n">PaymentAble</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">new</span><span class="w"> </span><span class="n">WxpayPaymentRequest</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setBody</span><span class="p">(</span><span class="s">&#34;微信测试商品&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setTotal_fee</span><span class="p">(</span><span class="s">&#34;0.1&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                        </span><span class="p">.</span><span class="na">setOut_trade_no</span><span class="p">(</span><span class="s">&#34;2023009999999&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;微信-支付-交易成功&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/wxUnifiedOrderNotify&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">wxUnifiedOrderNotify</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;微信-支付回调-交易成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="s">&#34;交易成功！&#34;</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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diff --git a/docs/posts/toy/pipeline-business/index.html b/docs/posts/toy/pipeline-business/index.html
new file mode 100644
index 00000000..1beedf71
--- /dev/null
+++ b/docs/posts/toy/pipeline-business/index.html
@@ -0,0 +1,2191 @@
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+<html lang="zh" >
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+	<title>Java管道流设计模式结合业务 ｜ 脚踏实地</title>
+	
+    
+    
+    <meta name="description" content="流程图 代码实现 完整代码：https://gitee.com/gitee_pikaqiu/easy-pipeline pom &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.plugin&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-plugin-core&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;${spring.plugin.core.version}&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt;" />
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+                <a class="nav-link text-left" href="#%e6%b5%81%e7%a8%8b%e5%9b%be">
+                    流程图
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+                <a class="nav-link text-left" href="#%e4%bb%a3%e7%a0%81%e5%ae%9e%e7%8e%b0">
+                    代码实现
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+            
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+        </ul>
+        
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+            <li class="nav-item">
+                <a class="nav-link text-left" href="#pom">
+                    pom
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#context">
+                    context
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#eventcontext">
+                    EventContext
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#biztype">
+                    BizType
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
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+        
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#abstracteventcontext">
+                    AbstractEventContext
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filter">
+                    filter
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#eventfilter">
+                    EventFilter
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+            
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#abstracteventfilter">
+                    AbstractEventFilter
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#eventfilterchain">
+                    EventFilterChain
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filterchainpipeline">
+                    FilterChainPipeline
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+        
+        
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+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#defaulteventfilterchain">
+                    DefaultEventFilterChain
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#selector">
+                    selector
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filterselector">
+                    FilterSelector
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
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+        
+        
+        
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+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#defaultfilterselector">
+                    DefaultFilterSelector
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e8%b0%83%e7%94%a8%e4%bb%a3%e7%a0%81">
+                    调用代码
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#pipelineapplication">
+                    PipelineApplication
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#controller">
+                    controller
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#entity">
+                    entity
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#service">
+                    service
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness1">
+                    service.business1
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness1context">
+                    service.business1.context
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness1filters">
+                    service.business1.filters
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness1plugins">
+                    service.business1.plugins
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness2">
+                    service.business2
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness2context">
+                    service.business2.context
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness2filters">
+                    service.business2.filters
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#servicebusiness2plugins">
+                    service.business2.plugins
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#serviceconfig">
+                    service.config
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#serviceselector">
+                    service.selector
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#applicationyml">
+                    application.yml
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
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+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Java管道流设计模式结合业务</h2>
+                        <span id="post_page_title_date" class="date">2023.06.15</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="流程图">流程图</h2>
+<p><img alt="管道流设计结合业务-01" src="/iblog/posts/annex/images/essays/%E7%AE%A1%E9%81%93%E6%B5%81%E8%AE%BE%E8%AE%A1%E7%BB%93%E5%90%88%E4%B8%9A%E5%8A%A1-01.jpg"></p>
+<h2 id="代码实现">代码实现</h2>
+<p><img alt="管道流设计结合业务-02" src="/iblog/posts/annex/images/essays/%E7%AE%A1%E9%81%93%E6%B5%81%E8%AE%BE%E8%AE%A1%E7%BB%93%E5%90%88%E4%B8%9A%E5%8A%A1-02.jpg"></p>
+<p>完整代码：<a href="https://gitee.com/gitee_pikaqiu/easy-pipeline">https://gitee.com/gitee_pikaqiu/easy-pipeline</a></p>
+<h3 id="pom">pom</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-xml" data-lang="xml"><span class="line"><span class="cl"><span class="nt">&lt;dependencies&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-web<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.plugin<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-plugin-core<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>${spring.plugin.core.version}<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-test<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;scope&gt;</span>test<span class="nt">&lt;/scope&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>org.projectlombok<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>lombok<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;optional&gt;</span>true<span class="nt">&lt;/optional&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">    
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;groupId&gt;</span>cn.hutool<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;artifactId&gt;</span>hutool-all<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;version&gt;</span>${hutool.version}<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl"><span class="nt">&lt;/dependencies&gt;</span>
+</span></span></code></pre></div><h3 id="context">context</h3>
+<h4 id="eventcontext">EventContext</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">EventContext</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 是否继续调用链
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">continueChain</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取当前过滤器选择器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">FilterSelector</span><span class="w"> </span><span class="nf">getFilterSelector</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="biztype">BizType</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">BizType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取业务类型码值
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Integer</span><span class="w"> </span><span class="nf">getCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 业务类型名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="w"> </span><span class="nf">getName</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="abstracteventcontext">AbstractEventContext</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractEventContext</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">EventContext</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">BizType</span><span class="w"> </span><span class="n">businessType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="nf">AbstractEventContext</span><span class="p">(</span><span class="n">BizType</span><span class="w"> </span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">businessType</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">businessType</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">filterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">continueChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="nf">getFilterSelector</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="filter">filter</h3>
+<h4 id="eventfilter">EventFilter</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">EventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 过滤逻辑封装点
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param context 上下文对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param chain   调用链
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">doFilter</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">,</span><span class="w"> </span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">chain</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="abstracteventfilter">AbstractEventFilter</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doFilter</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">,</span><span class="w"> </span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">chain</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 执行</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">context</span><span class="p">.</span><span class="na">getFilterSelector</span><span class="p">().</span><span class="na">matchFilter</span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">getClass</span><span class="p">().</span><span class="na">getSimpleName</span><span class="p">()))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">handler</span><span class="p">(</span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 是否继续执行调用链</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">context</span><span class="p">.</span><span class="na">continueChain</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">chain</span><span class="p">.</span><span class="na">nextHandler</span><span class="p">(</span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param context 上下文对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="eventfilterchain">EventFilterChain</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 执行当前过滤器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param context 上下文对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 跳过当前过滤器 执行下一个执行过滤器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param context 上下文对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">nextHandler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="filterchainpipeline">FilterChainPipeline</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">F</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&gt;</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">DefaultEventFilterChain</span><span class="o">&lt;</span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="n">last</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">F</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">append</span><span class="p">(</span><span class="n">F</span><span class="w"> </span><span class="n">filter</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultEventFilterChain</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">last</span><span class="p">,</span><span class="w"> </span><span class="n">filter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">F</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">append</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">description</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="n">filter</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;过滤器调用链管道开始设置 {} 过滤器&#34;</span><span class="p">,</span><span class="n">description</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultEventFilterChain</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">last</span><span class="p">,</span><span class="w"> </span><span class="n">filter</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">DefaultEventFilterChain</span><span class="o">&lt;</span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getFilterChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">last</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="defaulteventfilterchain">DefaultEventFilterChain</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DefaultEventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventContext</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filter</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">DefaultEventFilterChain</span><span class="p">(</span><span class="n">EventFilterChain</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">next</span><span class="p">,</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filter</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">next</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">next</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">filter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filter</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">filter</span><span class="p">.</span><span class="na">doFilter</span><span class="p">(</span><span class="n">context</span><span class="p">,</span><span class="k">this</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">nextHandler</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">next</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">next</span><span class="p">.</span><span class="na">handler</span><span class="p">(</span><span class="n">context</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="selector">selector</h3>
+<h4 id="filterselector">FilterSelector</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">FilterSelector</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 匹配过滤器
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param currentFilterName 过滤器名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 匹配成功
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">matchFilter</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">currentFilterName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取当前所有过滤器名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 过滤器名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getAllFilterNames</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h4 id="defaultfilterselector">DefaultFilterSelector</h4>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DefaultFilterSelector</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FilterSelector</span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w">  </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filterNames</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CollUtil</span><span class="p">.</span><span class="na">newArrayList</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">matchFilter</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">currentFilterName</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">filterNames</span><span class="p">.</span><span class="na">stream</span><span class="p">().</span><span class="na">anyMatch</span><span class="p">(</span><span class="n">s</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">Objects</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">s</span><span class="p">,</span><span class="n">currentFilterName</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getAllFilterNames</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">filterNames</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="调用代码">调用代码</h2>
+<p><img alt="管道流设计结合业务-03" src="/iblog/posts/annex/images/essays/%E7%AE%A1%E9%81%93%E6%B5%81%E8%AE%BE%E8%AE%A1%E7%BB%93%E5%90%88%E4%B8%9A%E5%8A%A1-03.jpg"></p>
+<h3 id="pipelineapplication">PipelineApplication</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@SpringBootApplication</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@EnablePluginRegistries</span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="n">Business1PostPlugin</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="n">Business2PostPlugin</span><span class="p">.</span><span class="na">class</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PipelineApplication</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">SpringApplication</span><span class="p">.</span><span class="na">run</span><span class="p">(</span><span class="n">PipelineApplication</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="n">args</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="controller">controller</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@RestController</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequestMapping</span><span class="p">(</span><span class="s">&#34;/pipelineTest&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PipelineController</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Service</span><span class="w"> </span><span class="n">business1PipelineTestService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Service</span><span class="w"> </span><span class="n">business2PipelineTestService</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/business1&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">business1</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PipelineRequestVo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setUuid</span><span class="p">(</span><span class="s">&#34;business1-1110-1111231afsas-123adss&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setBusinessCode</span><span class="p">(</span><span class="s">&#34;business1&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Business1Model2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Business1Model1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business1PipelineTestService</span><span class="p">.</span><span class="na">doService</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@GetMapping</span><span class="p">(</span><span class="s">&#34;/business2&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">business2</span><span class="p">(){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">PipelineRequestVo</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setUuid</span><span class="p">(</span><span class="s">&#34;business2-1110-1111231afsas-123adss&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setBusinessCode</span><span class="p">(</span><span class="s">&#34;business2&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setModel3</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Business2Model1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">setModel4</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Business2Model2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business2PipelineTestService</span><span class="p">.</span><span class="na">doService</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="entity">entity</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PipelineRequestVo</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uuid</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">businessCode</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Model2</span><span class="w"> </span><span class="n">model2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Model2</span><span class="w"> </span><span class="n">model4</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="service">service</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">enum</span><span class="w"> </span><span class="n">BusinessTypeEnum</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">BizType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BUSINESS_1</span><span class="p">(</span><span class="n">1</span><span class="p">,</span><span class="s">&#34;业务1&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BUSINESS_2</span><span class="p">(</span><span class="n">2</span><span class="p">,</span><span class="s">&#34;业务2&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">BUSINESS_3</span><span class="p">(</span><span class="n">3</span><span class="p">,</span><span class="s">&#34;业务3&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">code</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">   </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness1">service.business1</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business1Service</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">doService</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1ServiceImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1Service</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Qualifier</span><span class="p">(</span><span class="s">&#34;business1PipelineSelectorFactory&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w">  </span><span class="n">PipelineSelectorFactory</span><span class="w"> </span><span class="n">business1PipelineSelectorFactory</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w">  </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business1PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w">  </span><span class="n">PluginRegistry</span><span class="o">&lt;</span><span class="n">Business1PostPlugin</span><span class="p">,</span><span class="w"> </span><span class="n">Business1Model1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business1PostPlugin</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doService</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============business1开始===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理器参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始获取FilterSelector===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">business1PipelineSelectorFactory</span><span class="p">.</span><span class="na">getFilterSelector</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Context</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Business1Context</span><span class="p">(</span><span class="n">BusinessTypeEnum</span><span class="p">.</span><span class="na">BUSINESS_1</span><span class="p">,</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;获取FilterSelector完成: {}&#34;</span><span class="p">,</span><span class="n">filterSelector</span><span class="p">.</span><span class="na">getAllFilterNames</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============获取FilterSelector完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始执行过滤器===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setPipelineTestRequest</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">getModel2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">getModel1</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">filterChainPipeline</span><span class="p">.</span><span class="na">getFilterChain</span><span class="p">().</span><span class="na">handler</span><span class="p">(</span><span class="n">pipelineEventContext</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============执行过滤器完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理后获取值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始执行后置处理器===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model2</span><span class="w"> </span><span class="n">model2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getModel2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getPipelineTestRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business1PostPlugin</span><span class="p">.</span><span class="na">getPluginsFor</span><span class="p">(</span><span class="n">model1</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">handler</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">handler</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">model1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============执行后置处理器完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============business1结束===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness1context">service.business1.context</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Context</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventContext</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business1Model2</span><span class="w"> </span><span class="n">model2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Business1Context</span><span class="p">(</span><span class="n">BizType</span><span class="w"> </span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">continueChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Model1</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Model2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness1filters">service.business1.filters</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business1PipelineFilter</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">Business1Context</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Filter1</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">Business1Context</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1PipelineFilter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">Business1Context</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟操作数据库 等业务操作 可以利用门面模式进行解耦</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName1</span><span class="p">(</span><span class="s">&#34;张三&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName2</span><span class="p">(</span><span class="s">&#34;李四&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName3</span><span class="p">(</span><span class="s">&#34;王五&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model2</span><span class="w"> </span><span class="n">model2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;18&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;小白&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;Filter1执行完毕...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存入新的值到上下文对象中 下个处理器继续处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">model1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">model2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1Filter2</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">Business1Context</span><span class="o">&gt;</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1PipelineFilter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">Business1Context</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟操作数据库 等业务操作 可以利用门面模式进行解耦</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName1</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName1</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName2</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName2</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName3</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName3</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">100</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;Filter2执行完毕...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存入新的值到上下文对象中 下个处理器继续处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">model1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">context</span><span class="p">.</span><span class="na">getModel2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness1plugins">service.business1.plugins</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business1PostPlugin</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Plugin</span><span class="o">&lt;</span><span class="n">Business1Model1</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param model 处理参数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1ServicePluginImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1PostPlugin</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">supports</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===&gt;{}&#34;</span><span class="p">,</span><span class="n">model</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1ServicePluginImpl2</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business1PostPlugin</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">supports</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business1Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===&gt;{}&#34;</span><span class="p">,</span><span class="n">model</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness2">service.business2</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business2Service</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">doService</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Service</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2ServiceImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2Service</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Qualifier</span><span class="p">(</span><span class="s">&#34;business2PipelineSelectorFactory&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PipelineSelectorFactory</span><span class="w"> </span><span class="n">business2PipelineSelectorFactory</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business2PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">filterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PluginRegistry</span><span class="o">&lt;</span><span class="n">Business2PostPlugin</span><span class="p">,</span><span class="w"> </span><span class="n">Business2Model1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business2PostPlugin</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">doService</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============business2开始===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理器参数</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始获取FilterSelector===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">business2PipelineSelectorFactory</span><span class="p">.</span><span class="na">getFilterSelector</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Context</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Business2Context</span><span class="p">(</span><span class="n">BusinessTypeEnum</span><span class="p">.</span><span class="na">BUSINESS_2</span><span class="p">,</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;获取FilterSelector完成: {}&#34;</span><span class="p">,</span><span class="n">filterSelector</span><span class="p">.</span><span class="na">getAllFilterNames</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============获取FilterSelector完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始执行过滤器===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setPipelineTestRequest</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">getModel4</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">pipelineTestRequest</span><span class="p">.</span><span class="na">getModel3</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">filterChainPipeline</span><span class="p">.</span><span class="na">getFilterChain</span><span class="p">().</span><span class="na">handler</span><span class="p">(</span><span class="n">pipelineEventContext</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============执行过滤器完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 处理后获取值</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============开始执行后置处理器===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model2</span><span class="w"> </span><span class="n">model2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getModel2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">.</span><span class="na">getPipelineTestRequest</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business2PostPlugin</span><span class="p">.</span><span class="na">getPluginsFor</span><span class="p">(</span><span class="n">model1</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">handler</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="n">handler</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">model1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============执行后置处理器完成===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===============business2结束===============&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness2context">service.business2.context</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Context</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventContext</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Business2Model2</span><span class="w"> </span><span class="n">model2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 在自定义的filter中处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Setter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">pipelineTestRequest</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="nf">Business2Context</span><span class="p">(</span><span class="n">BizType</span><span class="w"> </span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kd">super</span><span class="p">(</span><span class="n">businessType</span><span class="p">,</span><span class="w"> </span><span class="n">filterSelector</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">continueChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Model1</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name3</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Model2</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">id</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">age</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness2filters">service.business2.filters</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business2PipelineFilter</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">EventFilter</span><span class="o">&lt;</span><span class="n">Business2Context</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">     </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Filter1</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">Business2Context</span><span class="o">&gt;</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2PipelineFilter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">Business2Context</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟操作数据库 等业务操作 可以利用门面模式进行解耦</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName1</span><span class="p">(</span><span class="s">&#34;张三&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName2</span><span class="p">(</span><span class="s">&#34;李四&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName3</span><span class="p">(</span><span class="s">&#34;王五&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model2</span><span class="w"> </span><span class="n">model2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel2</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setDesc</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setAge</span><span class="p">(</span><span class="s">&#34;18&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model2</span><span class="p">.</span><span class="na">setName</span><span class="p">(</span><span class="s">&#34;小白&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;Filter1执行完毕...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存入新的值到上下文对象中 下个处理器继续处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">model1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">model2</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">1</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2Filter2</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractEventFilter</span><span class="o">&lt;</span><span class="n">Business2Context</span><span class="o">&gt;</span><span class="w">  </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2PipelineFilter</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">handler</span><span class="p">(</span><span class="n">Business2Context</span><span class="w"> </span><span class="n">context</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 模拟操作数据库 等业务操作 可以利用门面模式进行解耦</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">context</span><span class="p">.</span><span class="na">getModel1</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName1</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName1</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName2</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName2</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setName3</span><span class="p">(</span><span class="n">model1</span><span class="p">.</span><span class="na">getName3</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&#34;-------------&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">model1</span><span class="p">.</span><span class="na">setId</span><span class="p">(</span><span class="n">100</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;Filter2执行完毕...&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 存入新的值到上下文对象中 下个处理器继续处理</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel1</span><span class="p">(</span><span class="n">model1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">context</span><span class="p">.</span><span class="na">setModel2</span><span class="p">(</span><span class="n">context</span><span class="p">.</span><span class="na">getModel2</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">order</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">2</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="servicebusiness2plugins">service.business2.plugins</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Business2PostPlugin</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Plugin</span><span class="o">&lt;</span><span class="n">Business2Model1</span><span class="o">&gt;</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param model 处理参数
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2ServicePluginImpl</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2PostPlugin</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">supports</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">pipelineEventContext</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===&gt;{}&#34;</span><span class="p">,</span><span class="n">model</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2ServicePluginImpl2</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Business2PostPlugin</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">supports</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">Business2Model1</span><span class="w"> </span><span class="n">model</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;===&gt;{}&#34;</span><span class="p">,</span><span class="n">model</span><span class="p">.</span><span class="na">getId</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="serviceconfig">service.config</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@ConfigurationProperties</span><span class="p">(</span><span class="n">prefix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;test&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FilterConfigProperties</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">configs</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="nf">getConfigs</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">configs</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">configs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MapUtil</span><span class="p">.</span><span class="na">newHashMap</span><span class="p">(</span><span class="n">16</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">configs</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">PipelineFilterConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Business1PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business1PipelineFilter</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business1PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business1FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">Business2PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business2PipelineFilter</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business2PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">business2FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">FilterConfigProperties</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business1PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">business1ChargePipeline</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">configs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">.</span><span class="na">getConfigs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">business1PipelineFilter</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">configs</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">business1FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">Map</span><span class="p">.</span><span class="na">Entry</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">filtersName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">configs</span><span class="p">.</span><span class="na">entrySet</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">distinctCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filtersName</span><span class="p">.</span><span class="na">stream</span><span class="p">().</span><span class="na">distinct</span><span class="p">().</span><span class="na">count</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">distinctCount</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">business1PipelineFilter</span><span class="p">.</span><span class="na">size</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;设置的过滤器数量大于实际过滤器数量&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business1PipelineFilter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">stream</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">sorted</span><span class="p">(</span><span class="n">Comparator</span><span class="p">.</span><span class="na">comparing</span><span class="p">(</span><span class="n">Business1PipelineFilter</span><span class="p">::</span><span class="n">order</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">business1FilterChainPipeline</span><span class="p">::</span><span class="n">append</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">business1FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterChainPipeline</span><span class="o">&lt;</span><span class="n">Business2PipelineFilter</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">business2ChargePipeline</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Map</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">configs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">.</span><span class="na">getConfigs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">business2PipelineFilter</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">configs</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">business2FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Set</span><span class="o">&lt;</span><span class="n">Map</span><span class="p">.</span><span class="na">Entry</span><span class="o">&lt;</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;&gt;&gt;</span><span class="w"> </span><span class="n">filtersName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">configs</span><span class="p">.</span><span class="na">entrySet</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">long</span><span class="w"> </span><span class="n">distinctCount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">filtersName</span><span class="p">.</span><span class="na">stream</span><span class="p">().</span><span class="na">distinct</span><span class="p">().</span><span class="na">count</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">distinctCount</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">business2PipelineFilter</span><span class="p">.</span><span class="na">size</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">&#34;设置的过滤器数量大于实际过滤器数量&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">business2PipelineFilter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">stream</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">sorted</span><span class="p">(</span><span class="n">Comparator</span><span class="p">.</span><span class="na">comparing</span><span class="p">(</span><span class="n">Business2PipelineFilter</span><span class="p">::</span><span class="n">order</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">.</span><span class="na">forEach</span><span class="p">(</span><span class="n">business2FilterChainPipeline</span><span class="p">::</span><span class="n">append</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">business2FilterChainPipeline</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="serviceselector">service.selector</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">PipelineSelectorFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">FilterSelector</span><span class="w">  </span><span class="nf">getFilterSelector</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">request</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;business1PipelineSelectorFactory&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business1PipelineSelectorFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PipelineSelectorFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">FilterConfigProperties</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="nf">getFilterSelector</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">businessCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">request</span><span class="p">.</span><span class="na">getBusinessCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DefaultFilterSelector</span><span class="w"> </span><span class="n">defaultFilterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultFilterSelector</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">businessCode</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;business1&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">defaultFilterSelector</span><span class="p">.</span><span class="na">setFilterNames</span><span class="p">(</span><span class="n">filterConfigProperties</span><span class="p">.</span><span class="na">getConfigs</span><span class="p">().</span><span class="na">getOrDefault</span><span class="p">(</span><span class="n">businessCode</span><span class="p">,</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">unmodifiableList</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">())));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">defaultFilterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;business2PipelineSelectorFactory&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Business2PipelineSelectorFactory</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">PipelineSelectorFactory</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">FilterConfigProperties</span><span class="w"> </span><span class="n">filterConfigProperties</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">FilterSelector</span><span class="w"> </span><span class="nf">getFilterSelector</span><span class="p">(</span><span class="n">PipelineRequestVo</span><span class="w"> </span><span class="n">request</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">businessCode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">request</span><span class="p">.</span><span class="na">getBusinessCode</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">DefaultFilterSelector</span><span class="w"> </span><span class="n">defaultFilterSelector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DefaultFilterSelector</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">businessCode</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="s">&#34;business2&#34;</span><span class="p">)){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">defaultFilterSelector</span><span class="p">.</span><span class="na">setFilterNames</span><span class="p">(</span><span class="n">filterConfigProperties</span><span class="p">.</span><span class="na">getConfigs</span><span class="p">().</span><span class="na">getOrDefault</span><span class="p">(</span><span class="n">businessCode</span><span class="p">,</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">unmodifiableList</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">())));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">defaultFilterSelector</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="applicationyml">application.yml</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml"><span class="line"><span class="cl"><span class="nt">server</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">port</span><span class="p">:</span><span class="w"> </span><span class="m">8080</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">test</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">configs</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">business1</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span>- <span class="l">Business1Filter1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span>- <span class="l">Business1Filter2</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nt">business2</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span>- <span class="l">Business2Filter1</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">      </span>- <span class="l">Business2Filter2</span><span class="w">
+</span></span></span></code></pre></div></div>
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\ No newline at end of file
diff --git a/docs/posts/toy/uploadfile-code/index.html b/docs/posts/toy/uploadfile-code/index.html
new file mode 100644
index 00000000..8d563724
--- /dev/null
+++ b/docs/posts/toy/uploadfile-code/index.html
@@ -0,0 +1,2188 @@
+<!DOCTYPE html>
+<html lang="zh" >
+<head>
+    <meta charset="utf-8" />
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+	
+	
+	<title>Java整合文件上传功能 ｜ 脚踏实地</title>
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+    
+    
+    <meta name="description" content="结构 pom.xml fastdfs-client-java-1.27.jar：点击下载 &amp;lt;dependencies&amp;gt; &amp;lt;!-- fastdfs --&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.csource&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;fastdfs-client-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;1.27&amp;lt;/version&amp;gt; &amp;lt;systemPath&amp;gt;${project.basedir}/lib/fastdfs-client-java-1.27.jar&amp;lt;/systemPath&amp;gt; &amp;lt;scope&amp;gt;system&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;!--aliyun oss 依赖--&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.aliyun.oss&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;aliyun-sdk-oss&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt;" />
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+    <div class="post-password">
+        
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+
+
+
+
+
+
+
+<div id="post_content_toc" class="toc">
+    <div class="page-header"><strong></strong></div>
+    <div id="page-scrollspy" class="toc-nav">
+
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+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e7%bb%93%e6%9e%84">
+                    结构
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#pomxml">
+                    pom.xml
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#applicationyml">
+                    application.yml
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#%e5%85%ac%e5%85%b1%e9%83%a8%e5%88%86">
+                    公共部分
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filemanagement">
+                    FileManagement
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filebeanmanagement">
+                    FileBeanManagement
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#abstractuploadmanagement">
+                    AbstractUploadManagement
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#abstractdownloadmanagement">
+                    AbstractDownloadManagement
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypefileconfig">
+                    ArchetypeFileConfig
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypefileplatformtype">
+                    ArchetypeFilePlatformType
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#fileconstant">
+                    FileConstant
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filefacade">
+                    FileFacade
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#filemanagementbridge">
+                    FileManagementBridge
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#downloadfileextensions">
+                    DownloadFileExtensions
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#uploadfileextensions">
+                    UploadFileExtensions
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+                    阿里云
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
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+            
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+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#aliyunfileconfig">
+                    AliyunFileConfig
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
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+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#archetypealiyundownload">
+                    ArchetypeAliyunDownload
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
+        </ul>
+        
+        
+        
+        
+        
+        
+        
+        
+        
+        <ul class="nav">
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+                    ArchetypeAliyunUpload
+                </a>
+            </li>
+            
+            
+        </ul>
+        
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+        
+        </ul>
+        
+        
+        
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+        
+        <ul class="nav">
+            
+        <ul class="nav">
+            
+            
+            <li class="nav-item">
+                <a class="nav-link text-left" href="#fastdfs">
+                    fastdfs
+                </a>
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+            
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+        
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+        
+        
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+                    FastDfsConfig
+                </a>
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+            
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+        
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+                </a>
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+            
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+        
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+                </a>
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+            
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+        
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+                <a class="nav-link text-left" href="#localfileconfig">
+                    LocalFileConfig
+                </a>
+            </li>
+            
+            
+        </ul>
+        
+        </ul>
+        
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+        
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+        
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+            
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+                    ArchetypeLocalUpload
+                </a>
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+            
+            
+        </ul>
+        
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+                    <svg t="1688715321313" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5356" width="16" height="16"><path d="M483.555556 199.111111m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5357"></path><path d="M483.555556 540.444444m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5358"></path><path d="M483.555556 881.777778m-85.333334 0a85.333333 85.333333 0 1 0 170.666667 0 85.333333 85.333333 0 1 0-170.666667 0Z" fill="#424242" p-id="5359"></path></svg>
+                </a>
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+                    <svg t="1688723160472" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="15872" width="16" height="16"><path d="M300.105143 592.676571h423.789714a80.676571 80.676571 0 1 0 0-161.353142H300.105143a80.676571 80.676571 0 0 0 0 161.353142z" fill="#8a8a8a" p-id="15873"></path></svg>
+                </a>
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+
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+            <div class="post">
+                <div class="post_title post_detail_title">
+                    <span class="date" id="busuanzi_container_site_pv">访问量 <span id="busuanzi_value_site_pv"></span>次</span>
+                </div>
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+    </div>
+</div>
+        <div class="content">
+            <div class="post_page">
+                <div class="post animate__animated animate__fadeInDown">
+                    <div class="post_title post_detail_title">
+                        <h2 id="post_single_title">Java整合文件上传功能</h2>
+                        <span id="post_page_title_date" class="date">2023.08.11</span>
+                        
+                        <span id="busuanzi_container_page_pv" class="m-l-10">
+                          阅读量<span id="busuanzi_value_page_pv"></span>次
+                        </span>
+                        
+                    </div>
+                    <div class="post_content markdown"><h2 id="结构">结构</h2>
+<p><img alt="整合文件上传功能" src="/iblog/posts/annex/images/essays/%E6%95%B4%E5%90%88%E6%96%87%E4%BB%B6%E4%B8%8A%E4%BC%A0%E5%8A%9F%E8%83%BD-01.jpg"></p>
+<h2 id="pomxml">pom.xml</h2>
+<p>fastdfs-client-java-1.27.jar：<a href="/iblog/posts/annex/jar/lib/fastdfs-client-java-1.27.jar">点击下载</a></p>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-xml" data-lang="xml"><span class="line"><span class="cl">    <span class="nt">&lt;dependencies&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c">&lt;!-- fastdfs --&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>org.csource<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>fastdfs-client-java<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;version&gt;</span>1.27<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;systemPath&gt;</span>${project.basedir}/lib/fastdfs-client-java-1.27.jar<span class="nt">&lt;/systemPath&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;scope&gt;</span>system<span class="nt">&lt;/scope&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="c">&lt;!--aliyun oss 依赖--&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>com.aliyun.oss<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>aliyun-sdk-oss<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-web<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>org.springframework.boot<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>spring-boot-starter-test<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;scope&gt;</span>test<span class="nt">&lt;/scope&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>org.projectlombok<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>lombok<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;optional&gt;</span>true<span class="nt">&lt;/optional&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>cn.hutool<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>hutool-all<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;version&gt;</span>5.8.11<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;dependency&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;groupId&gt;</span>commons-io<span class="nt">&lt;/groupId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;artifactId&gt;</span>commons-io<span class="nt">&lt;/artifactId&gt;</span>
+</span></span><span class="line"><span class="cl">            <span class="nt">&lt;version&gt;</span>2.11.0<span class="nt">&lt;/version&gt;</span>
+</span></span><span class="line"><span class="cl">        <span class="nt">&lt;/dependency&gt;</span>
+</span></span><span class="line"><span class="cl">
+</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/dependencies&gt;</span>
+</span></span></code></pre></div><h2 id="applicationyml">application.yml</h2>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yml" data-lang="yml"><span class="line"><span class="cl"><span class="nt">server</span><span class="p">:</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">  </span><span class="nt">port</span><span class="p">:</span><span class="w"> </span><span class="m">80</span><span class="w">
+</span></span></span></code></pre></div><h2 id="公共部分">公共部分</h2>
+<h3 id="filemanagement">FileManagement</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">FileManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 设置下一个bean的对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param nextFileManagement 下一个bean对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNext</span><span class="p">(</span><span class="n">FileManagement</span><span class="w"> </span><span class="n">nextFileManagement</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="filebeanmanagement">FileBeanManagement</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FileBeanManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;uploadChain&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="nf">uploadChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">buildChain</span><span class="p">(</span><span class="n">AbstractUploadManagement</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Bean</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;downloadChain&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="nf">downloadChain</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">buildChain</span><span class="p">(</span><span class="n">AbstractDownloadManagement</span><span class="p">.</span><span class="na">class</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 设置文件管理bean调用链(环状链)
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param type   文件管理类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param isRing 是否形成环形链表
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param &lt;T&gt;    extends FileManagement 指定类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return bean
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="o">&lt;</span><span class="n">T</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">FileManagement</span><span class="o">&gt;</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">buildChain</span><span class="p">(</span><span class="n">Class</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">type</span><span class="p">,</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isRing</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">beans</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">SpringUtil</span><span class="p">.</span><span class="na">getBeansOfType</span><span class="p">(</span><span class="n">type</span><span class="p">).</span><span class="na">values</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 设置调用链</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">size</span><span class="p">();</span><span class="w"> </span><span class="n">index</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 判断是否到最后一个bean 如果到了最后一个bean将第一个bean设置为尾部的下一个节点 形成环状结构</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">beans</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">index</span><span class="p">).</span><span class="na">setNext</span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">size</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">isRing</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">1</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">beans</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">0</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="abstractuploadmanagement">AbstractUploadManagement</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractUploadManagement</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FileManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="n">self</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNext</span><span class="p">(</span><span class="n">FileManagement</span><span class="w"> </span><span class="n">fileManagement</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">self</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">AbstractUploadManagement</span><span class="p">)</span><span class="n">fileManagement</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">allowUploadFiles</span><span class="p">(</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowFiles</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getAllowFiles</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="n">FileConstant</span><span class="p">.</span><span class="na">DEFAULT_ALLOWED_EXTENSION</span><span class="p">)</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 判断是否是当前平台处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType 指定平台类型 {@linkplain ArchetypeFilePlatformType}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 为当前平台处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 校验允许上传的文件格式; 默认{@code  FileTypeUtils.DEFAULT_ALLOWED_EXTENSION}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileName 文件名称
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 允许上传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">checkAllowUploadFiles</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileName</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">fileName</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowUploadFiles</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">allowUploadFiles</span><span class="p">(</span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">allowUploadFile</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">allowUploadFiles</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">fileName</span><span class="p">.</span><span class="na">toLowerCase</span><span class="p">().</span><span class="na">endsWith</span><span class="p">(</span><span class="n">allowUploadFile</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;当前上传文件仅支持 [{}] 格式&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">allowUploadFiles</span><span class="p">.</span><span class="na">toArray</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 校验允许上传的文件大小
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param bytes 字节数量
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 允许上传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w">  </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">checkSingleAllowUploadSize</span><span class="p">(</span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">bytes</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">bytes</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getAllowFileSize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 前置处理 预留方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 允许上传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传成功后的路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理 预留方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileUri 上传成功后的路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 文件上传路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileUri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 多上传文件模板方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileConfig    文件上传配置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传成功后的文件uri集合
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">uploadTemplate</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">multipartFile</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">emptyList</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">filePlatformType</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getFilePlatformType</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 检索上传文件平台类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">self</span><span class="p">.</span><span class="na">isCurrentPlatform</span><span class="p">(</span><span class="n">filePlatformType</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">uploadTemplate</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 多文件上传需要加循环</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">fileUriList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o">&lt;&gt;</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">self</span><span class="p">.</span><span class="na">beforeCheck</span><span class="p">(</span><span class="n">file</span><span class="p">,</span><span class="n">fileConfig</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">break</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">fileUriList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">self</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">self</span><span class="p">.</span><span class="na">upload</span><span class="p">(</span><span class="n">file</span><span class="p">,</span><span class="n">fileConfig</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;上传文件=&gt; 平台类型:[{}]\t 上传路径:[{}]&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">filePlatformType</span><span class="p">,</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">fileUriList</span><span class="p">.</span><span class="na">toArray</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileUriList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件前置校验
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true校验成功允许上传
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">beforeCheck</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="o">!</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">isEmpty</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getSize</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">checkAllowUploadFiles</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">(),</span><span class="n">fileConfig</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">checkSingleAllowUploadSize</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(),</span><span class="n">fileConfig</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">preProcessing</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="n">fileConfig</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="abstractdownloadmanagement">AbstractDownloadManagement</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AbstractDownloadManagement</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FileManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="n">self</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setNext</span><span class="p">(</span><span class="n">FileManagement</span><span class="w"> </span><span class="n">fileManagement</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">this</span><span class="p">.</span><span class="na">self</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">AbstractDownloadManagement</span><span class="p">)</span><span class="n">fileManagement</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 前置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          下载文件的地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true-允许执行后置操作
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          下载文件地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 下载到的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param downloadFile 下载的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 经过后置处理下载后的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 判断是否是当前平台处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType 指定平台类型 {@linkplain ArchetypeFilePlatformType}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true 为当前平台处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文件下载模板方法
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType 平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          文件地址,支持本地和http地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return file对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">downloadTemplate</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 检索上传文件平台类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">self</span><span class="p">.</span><span class="na">isCurrentPlatform</span><span class="p">(</span><span class="n">platformType</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">downloadTemplate</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 前置下载校验</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">self</span><span class="p">.</span><span class="na">preProcessing</span><span class="p">(</span><span class="n">uri</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">CharSequenceUtil</span><span class="p">.</span><span class="na">EMPTY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 下载文件到指定路径</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">self</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">self</span><span class="p">.</span><span class="na">download</span><span class="p">(</span><span class="n">uri</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">,</span><span class="w"> </span><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="p">,</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="n">fileLength</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;下载文件平台类型: {} 文件大小为:{} MB&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DecimalFormat</span><span class="p">(</span><span class="s">&#34;0.00&#34;</span><span class="p">).</span><span class="na">format</span><span class="p">(</span><span class="n">fileLength</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="n">1024</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1024</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 获取文件名称</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">split</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">uri</span><span class="p">.</span><span class="na">split</span><span class="p">(</span><span class="n">platformType</span><span class="p">.</span><span class="na">getFileSeparator</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">fullFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">split</span><span class="o">[</span><span class="n">split</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">1</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">fileNameWithSuffix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fullFileName</span><span class="p">.</span><span class="na">split</span><span class="p">(</span><span class="s">&#34;\\.&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 指定存放位置(有需求可以自定义)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">path</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;%s%s%s_%s.%s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p">.</span><span class="na">separatorChar</span><span class="p">,</span><span class="w"> </span><span class="n">fileNameWithSuffix</span><span class="o">[</span><span class="n">0</span><span class="o">]</span><span class="p">,</span><span class="w"> </span><span class="n">DateUtil</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(),</span><span class="w"> </span><span class="s">&#34;yyyyMMddHHmmss&#34;</span><span class="p">),</span><span class="w"> </span><span class="n">fileNameWithSuffix</span><span class="o">[</span><span class="n">1</span><span class="o">]</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">path</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 校验文件夹目录是否存在，不存在就创建一个目录</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">file</span><span class="p">.</span><span class="na">getParentFile</span><span class="p">().</span><span class="na">exists</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">file</span><span class="p">.</span><span class="na">getParentFile</span><span class="p">().</span><span class="na">mkdirs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 写入文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@Cleanup</span><span class="w"> </span><span class="n">OutputStream</span><span class="w"> </span><span class="n">out</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Files</span><span class="p">.</span><span class="na">newOutputStream</span><span class="p">(</span><span class="n">file</span><span class="p">.</span><span class="na">toPath</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="nd">@Cleanup</span><span class="w"> </span><span class="n">BufferedInputStream</span><span class="w"> </span><span class="n">bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">BufferedInputStream</span><span class="p">(</span><span class="n">inputStream</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">int</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">0</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="kt">byte</span><span class="o">[]</span><span class="w"> </span><span class="n">buf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="kt">byte</span><span class="o">[</span><span class="n">2048</span><span class="o">]</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bin</span><span class="p">.</span><span class="na">read</span><span class="p">(</span><span class="n">buf</span><span class="p">))</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="o">-</span><span class="n">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">len</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">size</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">out</span><span class="p">.</span><span class="na">write</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span><span class="w"> </span><span class="n">0</span><span class="p">,</span><span class="w"> </span><span class="n">size</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">log</span><span class="p">.</span><span class="na">isDebugEnabled</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">log</span><span class="p">.</span><span class="na">debug</span><span class="p">(</span><span class="s">&#34;下载文件 {} 进度 =&gt;{}%&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fullFileName</span><span class="p">,</span><span class="w"> </span><span class="n">len</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">100L</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">fileLength</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;{} 文件下载成功！&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">path</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">file</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">defaultHttpDownload</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 建立 http 下载连接 建立链接从请求中获取数据</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">HttpURLConnection</span><span class="w"> </span><span class="n">httpUrlConnection</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">HttpURLConnection</span><span class="p">)</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">URL</span><span class="p">(</span><span class="n">uri</span><span class="p">).</span><span class="na">openConnection</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">setConnectTimeout</span><span class="p">(</span><span class="n">10</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">1000</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">setRequestMethod</span><span class="p">(</span><span class="s">&#34;GET&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">setRequestProperty</span><span class="p">(</span><span class="s">&#34;Charset&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;UTF-8&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">connect</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">download</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">,</span><span class="w"> </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">getInputStream</span><span class="p">(),</span><span class="w"> </span><span class="n">httpUrlConnection</span><span class="p">.</span><span class="na">getContentLength</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypefileconfig">ArchetypeFileConfig</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">ArchetypeFileConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 文件平台类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="nf">getFilePlatformType</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">getAllowFiles</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件大小; 单位字节
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">Long</span><span class="w"> </span><span class="nf">getAllowFileSize</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypefileplatformtype">ArchetypeFilePlatformType</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@AllArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">enum</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="c1">// 上传下载文件平台类型</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">LOCAL</span><span class="p">(</span><span class="s">&#34;\\\\&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ALIYUN</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">TENCEN_CLOUD</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">FAST_DFS</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件分隔符
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Getter</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">fileSeparator</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="fileconstant">FileConstant</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">FileConstant</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">IMAGE_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;bmp&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;gif&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;jpg&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;jpeg&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;png&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">FLASH_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;swf&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;flv&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">MEDIA_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;swf&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;flv&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;mp3&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;wav&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;wma&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;wmv&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;mid&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;avi&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;mpg&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;asf&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;rm&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;rmvb&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">VIDEO_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="s">&#34;mp4&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;avi&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;rmvb&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">DEFAULT_ALLOWED_EXTENSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 图片</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;bmp&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;gif&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;jpg&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;jpeg&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;png&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// word excel powerpoint</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;doc&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;docx&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;xls&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;xlsx&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;ppt&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;pptx&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;html&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;htm&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;txt&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 压缩文件</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;rar&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;zip&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;gz&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;bz2&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 视频格式</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;mp4&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;avi&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;rmvb&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// pdf</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="s">&#34;pdf&#34;</span><span class="p">};</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="filefacade">FileFacade</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">FileFacade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileConfig    文件上传配置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传后的文件地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">default</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">upload</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">UploadFileExtensions</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">uploadUriList</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">uploadUriList</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileConfig    文件上传配置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传后的文件地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">default</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">,</span><span class="w"> </span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">upload</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileConfig     文件上传配置
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile  上传的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileExtensions 文件扩展接口; 可在文件上传之前,上传之后进行操作
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 上传后的文件地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">,</span><span class="w"> </span><span class="n">UploadFileExtensions</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType 指定平台类型{@linkplain ArchetypeFilePlatformType}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          文件地址; 支持本地,http
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 下载的文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="k">default</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="nd">@NotNull</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="nd">@NotNull</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">download</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">DownloadFileExtensions</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="kd">public</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="k">return</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">});</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param platformType   指定平台类型{@linkplain ArchetypeFilePlatformType}
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri            文件地址; 支持本地,http
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param fileExtensions 下载文件扩展接口;可在下载上传之前,下载之后进行操作
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 下载的文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">DownloadFileExtensions</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="filemanagementbridge">FileManagementBridge</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FileManagementBridge</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">FileFacade</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Resource</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;uploadChain&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="n">uploadChain</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Resource</span><span class="p">(</span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;downloadChain&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="n">downloadChain</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">,</span><span class="w"> </span><span class="n">UploadFileExtensions</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ObjectUtil</span><span class="p">.</span><span class="na">isAllEmpty</span><span class="p">(</span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getFilePlatformType</span><span class="p">(),</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;upload file need param (platformType:[%s] multipartFile:[%s] maybe is empty.&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">.</span><span class="na">getFilePlatformType</span><span class="p">(),</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">)));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">fileExtensions</span><span class="p">.</span><span class="na">preProcessing</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">Collections</span><span class="p">.</span><span class="na">emptyList</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">uploadChain</span><span class="p">.</span><span class="na">uploadTemplate</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">DownloadFileExtensions</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">ObjectUtil</span><span class="p">.</span><span class="na">isAllEmpty</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;download file need param ( platformType:[%s] uri:[%s] ) maybe is empty.&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">fileExtensions</span><span class="p">.</span><span class="na">preProcessing</span><span class="p">(</span><span class="n">uri</span><span class="p">))</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">CharSequenceUtil</span><span class="p">.</span><span class="na">EMPTY</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileExtensions</span><span class="p">.</span><span class="na">postProcessing</span><span class="p">(</span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">downloadChain</span><span class="p">.</span><span class="na">downloadTemplate</span><span class="p">(</span><span class="n">platformType</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="downloadfileextensions">DownloadFileExtensions</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">DownloadFileExtensions</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件-前置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri 下载的uri
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true-允许下载;false-不允许下载
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件-后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uri          下载的uri
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param downloadFile 下载的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 经过后置处理的下载的文件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="uploadfileextensions">UploadFileExtensions</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">UploadFileExtensions</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件-前置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param multipartFile 上传的文件对象
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return true-能继续处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传文件-后置处理
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @param uploadUriList 上传文件返回的uri地址集合
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * @return 经过后置处理返回的uri地址集合
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="o">[]</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">uploadUriList</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="阿里云">阿里云</h2>
+<h3 id="aliyunfileconfig">AliyunFileConfig</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;aliyunFileConfig&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AliyunFileConfig</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 填写Bucket所在地域对应的Endpoint，可在创建好的Bucket概况页查看
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">endpoint</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 阿里云账号AccessKey里所对应的AccessKey ID
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">accessKeyId</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 阿里云账号AccessKey里所对应的AccessKey Secret
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">accessKeySecret</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * OSS对象存储空间名
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">bucketName</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件大小; 单位字节
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">allowFileSize</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="nf">getFilePlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">ALIYUN</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypealiyundownload">ArchetypeAliyunDownload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeAliyunDownload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeAliyunDownload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypealiyunupload">ArchetypeAliyunUpload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeAliyunUpload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeAliyunUpload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">ALIYUN</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">AliyunFileConfig</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">((</span><span class="n">AliyunFileConfig</span><span class="p">)</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">OSS</span><span class="w"> </span><span class="n">ossClient</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">OSSClientBuilder</span><span class="p">().</span><span class="na">build</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getEndpoint</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getAccessKeyId</span><span class="p">(),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getAccessKeySecret</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 上传文件流</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">InputStream</span><span class="w"> </span><span class="n">inputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getInputStream</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">String</span><span class="w"> </span><span class="n">fileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">fileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">UUID</span><span class="p">.</span><span class="na">randomUUID</span><span class="p">().</span><span class="na">toString</span><span class="p">().</span><span class="na">replaceAll</span><span class="p">(</span><span class="s">&#34;-&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">fileName</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="c1">// 按照当前日期，创建文件夹，上传到创建文件夹里面 20220315/xx.jpg</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">fileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DateUtil</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="n">DateUtil</span><span class="p">.</span><span class="na">date</span><span class="p">(),</span><span class="w"> </span><span class="s">&#34;yyyyMMdd&#34;</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">ALIYUN</span><span class="p">.</span><span class="na">getFileSeparator</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">fileName</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ossClient</span><span class="p">.</span><span class="na">putObject</span><span class="p">(</span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getBucketName</span><span class="p">(),</span><span class="w"> </span><span class="n">fileName</span><span class="p">,</span><span class="w"> </span><span class="n">inputStream</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">ossClient</span><span class="p">.</span><span class="na">shutdown</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="k">return</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;https://%s.%s/%s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getBucketName</span><span class="p">(),</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="p">.</span><span class="na">getEndpoint</span><span class="p">(),</span><span class="w"> </span><span class="n">fileName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileUri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileUri</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="fastdfs">fastdfs</h2>
+<h3 id="fastdfsconfig">FastDfsConfig</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;fastDfsConfig&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FastDfsConfig</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 编码
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">charset</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 连接超时事件
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">connectTimeoutInSecond</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 网络超时时间
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">networkTimeoutInSeconds</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * track端口
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">httpTrackerHttpPort</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * http令牌
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">httpAntiStealToken</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 服务器地址
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">trackerServers</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">storageServiceIp</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">storageServicePort</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Integer</span><span class="w"> </span><span class="n">storageServicePathIndex</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件大小; 单位字节
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">allowFileSize</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="nf">getFilePlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">FAST_DFS</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypefastdfsdownload">ArchetypeFastDfsDownload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeFastDfsDownload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@DependsOn</span><span class="p">({</span><span class="s">&#34;fastDfsConfig&#34;</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeFastDfsDownload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypefastdfsupload">ArchetypeFastDfsUpload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeFastDfsUpload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeFastDfsUpload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">FAST_DFS</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">FastDfsConfig</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">FastDfsConfig</span><span class="p">)</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">init</span><span class="p">(</span><span class="n">fastDfsConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">originalFilename</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">suffix</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">originalFilename</span><span class="p">.</span><span class="na">substring</span><span class="p">(</span><span class="n">originalFilename</span><span class="p">.</span><span class="na">lastIndexOf</span><span class="p">(</span><span class="s">&#34;.&#34;</span><span class="p">)</span><span class="o">+</span><span class="n">1</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">StorageClient</span><span class="w"> </span><span class="n">storageClient</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StorageClient</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StorageServer</span><span class="p">(</span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getStorageServiceIp</span><span class="p">(),</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getStorageServicePort</span><span class="p">(),</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getStorageServicePathIndex</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">strings</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">storageClient</span><span class="p">.</span><span class="na">upload_file</span><span class="p">(</span><span class="n">multipartFile</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(),</span><span class="w"> </span><span class="n">suffix</span><span class="p">,</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;http://%s:%s/%s&#34;</span><span class="p">,</span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getStorageServiceIp</span><span class="p">(),</span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getHttpTrackerHttpPort</span><span class="p">(),</span><span class="n">StrUtil</span><span class="p">.</span><span class="na">join</span><span class="p">(</span><span class="s">&#34;/&#34;</span><span class="p">,</span><span class="n">strings</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">init</span><span class="p">(</span><span class="n">FastDfsConfig</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">){</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 先从容器获取如果没有在加载 fixme</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="c1">// 文件服务器客户端初始化</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">Properties</span><span class="w"> </span><span class="n">properties</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Properties</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.connect_timeout_in_seconds&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getConnectTimeoutInSecond</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.network_timeout_in_seconds&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getNetworkTimeoutInSeconds</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.charset&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getCharset</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.http_tracker_http_port&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getHttpTrackerHttpPort</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.http_anti_steal_token&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getHttpAntiStealToken</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">properties</span><span class="p">.</span><span class="na">setProperty</span><span class="p">(</span><span class="s">&#34;fastdfs.tracker_servers&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="p">.</span><span class="na">getTrackerServers</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">ClientGlobal</span><span class="p">.</span><span class="na">initByProperties</span><span class="p">(</span><span class="n">properties</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;fastdfs客户端初始化成功&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileUri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileUri</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="本地">本地</h2>
+<h3 id="localfileconfig">LocalFileConfig</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Data</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Configuration</span><span class="p">(</span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&#34;localFileConfig&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Accessors</span><span class="p">(</span><span class="n">chain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">LocalFileConfig</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件类型
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">allowFiles</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 允许上传的文件大小; 单位字节
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="n">allowFileSize</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 上传的路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">uploadPath</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 下载文件到指定路径
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">downloadPath</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="nf">getFilePlatformType</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypelocaldownload">ArchetypeLocalDownload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@DependsOn</span><span class="p">({</span><span class="s">&#34;localFileConfig&#34;</span><span class="p">})</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeLocalDownload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeLocalDownload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractDownloadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">LocalFileConfig</span><span class="w"> </span><span class="n">localFileConfig</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">download</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">,</span><span class="w"> </span><span class="n">uri</span><span class="p">,</span><span class="w"> </span><span class="n">localFileConfig</span><span class="p">.</span><span class="na">getDownloadPath</span><span class="p">(),</span><span class="w"> </span><span class="n">Files</span><span class="p">.</span><span class="na">newInputStream</span><span class="p">(</span><span class="n">Paths</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">uri</span><span class="p">)),</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">uri</span><span class="p">).</span><span class="na">length</span><span class="p">());</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">File</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">downloadFile</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h3 id="archetypelocalupload">ArchetypeLocalUpload</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Component</span><span class="p">(</span><span class="s">&#34;archetypeLocalUpload&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RequiredArgsConstructor</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">ArchetypeLocalUpload</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">AbstractUploadManagement</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">isCurrentPlatform</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="w"> </span><span class="n">platformType</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">platformType</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">preProcessing</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">multipartFile</span><span class="p">,</span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@SneakyThrows</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">upload</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">file</span><span class="p">,</span><span class="w"> </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">LocalFileConfig</span><span class="w"> </span><span class="n">localFileConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">LocalFileConfig</span><span class="p">)</span><span class="w"> </span><span class="n">fileConfig</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">fileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">extractFilename</span><span class="p">(</span><span class="n">file</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">String</span><span class="w"> </span><span class="n">absPath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getAbsoluteFile</span><span class="p">(</span><span class="n">localFileConfig</span><span class="p">.</span><span class="na">getUploadPath</span><span class="p">(),</span><span class="w"> </span><span class="n">fileName</span><span class="p">).</span><span class="na">getAbsolutePath</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">file</span><span class="p">.</span><span class="na">transferTo</span><span class="p">(</span><span class="n">Paths</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">absPath</span><span class="p">));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">String</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;%s/%s&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">localFileConfig</span><span class="p">.</span><span class="na">getUploadPath</span><span class="p">(),</span><span class="w"> </span><span class="n">fileName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     * 编码文件名
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">extractFilename</span><span class="p">(</span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">file</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">CharSequenceUtil</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="s">&#34;{}/{}_{}.{}&#34;</span><span class="p">,</span><span class="w"> </span><span class="n">DateUtil</span><span class="p">.</span><span class="na">format</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Date</span><span class="p">(),</span><span class="w"> </span><span class="s">&#34;yyyyMMdd&#34;</span><span class="p">),</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">FilenameUtils</span><span class="p">.</span><span class="na">getBaseName</span><span class="p">(</span><span class="n">file</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">()),</span><span class="w"> </span><span class="n">IdUtil</span><span class="p">.</span><span class="na">getSnowflakeNextIdStr</span><span class="p">(),</span><span class="w"> </span><span class="n">FilenameUtils</span><span class="p">.</span><span class="na">getExtension</span><span class="p">(</span><span class="n">file</span><span class="p">.</span><span class="na">getOriginalFilename</span><span class="p">()));</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="nf">getAbsoluteFile</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">uploadDir</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">fileName</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">File</span><span class="w"> </span><span class="n">desc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="n">uploadDir</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">File</span><span class="p">.</span><span class="na">separator</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">fileName</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">desc</span><span class="p">.</span><span class="na">exists</span><span class="p">()</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="o">!</span><span class="n">desc</span><span class="p">.</span><span class="na">getParentFile</span><span class="p">().</span><span class="na">exists</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="n">desc</span><span class="p">.</span><span class="na">getParentFile</span><span class="p">().</span><span class="na">mkdirs</span><span class="p">();</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">desc</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Override</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">protected</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">postProcessing</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">fileUri</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="n">fileUri</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div><h2 id="调用测试">调用测试</h2>
+<h3 id="filetest">FileTest</h3>
+<div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@RunWith</span><span class="p">(</span><span class="n">SpringRunner</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="nd">@SpringBootTest</span><span class="p">(</span><span class="n">classes</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">FileApplication</span><span class="p">.</span><span class="na">class</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">FileTest</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Autowired</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">private</span><span class="w"> </span><span class="n">FileFacade</span><span class="w"> </span><span class="n">fileFacade</span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *     aliyun:
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFiles: [ &#34;.png&#34;,&#34;.txt&#34; ]
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFileSize: 10240
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       endpoint: oss-cn-shanghai.aliyuncs.com
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       accessKeyId: 
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       accessKeySecret: 
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       bucketName: shanghai-bucketnametest
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">AliyunFileConfig</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFiles</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="s">&#34;.png&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;.txt&#34;</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFileSize</span><span class="p">(</span><span class="n">10240L</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setEndpoint</span><span class="p">(</span><span class="s">&#34;oss-cn-shanghai.aliyuncs.com&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAccessKeyId</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAccessKeySecret</span><span class="p">(</span><span class="s">&#34;&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setBucketName</span><span class="p">(</span><span class="s">&#34;shanghai-bucketnametest&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *     local:
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFiles: [&#34;.png&#34;,&#34;.txt&#34;]
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFileSize: 10240
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       uploadPath: &#34;C:/Users/Administrator/Downloads&#34;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       downloadPath: &#34;C:/Users/Administrator/Downloads&#34;
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">localFileConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LocalFileConfig</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFiles</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="s">&#34;.png&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;.txt&#34;</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFileSize</span><span class="p">(</span><span class="n">10240L</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setUploadPath</span><span class="p">(</span><span class="s">&#34;C:\\Users\\Administrator\\Downloads&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setDownloadPath</span><span class="p">(</span><span class="s">&#34;C:\\Users\\Administrator\\Downloads&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="cm">/**
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *     fastdfs:
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFiles: [ &#34;.png&#34;,&#34;.txt&#34; ]
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       allowFileSize: 10240
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       charset: UTF-8
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       connectTimeoutInSecond: 10
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       networkTimeoutInSeconds: 30
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       httpTrackerHttpPort: 8888
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       httpAntiStealToken: no
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       trackerServers: 172.16.1.199:22122
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       fastdfsUrl: http://172.16.1.199:8888
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       storageServiceIp: 172.16.1.199
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       storageServicePort: 23000
+</span></span></span><span class="line"><span class="cl"><span class="cm">     *       storageServicePathIndex: 0
+</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="n">ArchetypeFileConfig</span><span class="w"> </span><span class="n">fastDfsConfig</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FastDfsConfig</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFiles</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">asList</span><span class="p">(</span><span class="s">&#34;.png&#34;</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;.txt&#34;</span><span class="p">))</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setAllowFileSize</span><span class="p">(</span><span class="n">10240L</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setCharset</span><span class="p">(</span><span class="s">&#34;UTF-8&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setConnectTimeoutInSecond</span><span class="p">(</span><span class="s">&#34;10&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setNetworkTimeoutInSeconds</span><span class="p">(</span><span class="s">&#34;30&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setHttpTrackerHttpPort</span><span class="p">(</span><span class="s">&#34;8888&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setHttpAntiStealToken</span><span class="p">(</span><span class="s">&#34;no&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setTrackerServers</span><span class="p">(</span><span class="s">&#34;172.16.1.199:22122&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setStorageServiceIp</span><span class="p">(</span><span class="s">&#34;172.16.1.199&#34;</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setStorageServicePort</span><span class="p">(</span><span class="n">23000</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">.</span><span class="na">setStorageServicePathIndex</span><span class="p">(</span><span class="n">0</span><span class="p">)</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">            </span><span class="p">;</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">uploadTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">MultipartFile</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">MockMultipartFile</span><span class="p">(</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;file&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;hello11.txt&#34;</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="n">MediaType</span><span class="p">.</span><span class="na">TEXT_PLAIN_VALUE</span><span class="p">,</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">                </span><span class="s">&#34;Hello, World!111111111111111111111111111&#34;</span><span class="p">.</span><span class="na">getBytes</span><span class="p">()</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">List</span><span class="o">&lt;</span><span class="n">String</span><span class="o">&gt;</span><span class="w"> </span><span class="n">uriLs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fileFacade</span><span class="p">.</span><span class="na">upload</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">MultipartFile</span><span class="o">[]</span><span class="p">{</span><span class="n">file</span><span class="p">},</span><span class="w"> </span><span class="n">aliyunFileConfig</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&#34;=&gt;&#34;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">uriLs</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="nd">@Test</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">downloadTest</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">        </span><span class="n">fileFacade</span><span class="p">.</span><span class="na">download</span><span class="p">(</span><span class="n">ArchetypeFilePlatformType</span><span class="p">.</span><span class="na">LOCAL</span><span class="p">,</span><span class="w"> </span><span class="s">&#34;C:\\Users\\Administrator\\Downloads\\20230114\\hello_1614199174685622272.txt&#34;</span><span class="p">);</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">    </span><span class="p">}</span><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w">
+</span></span></span><span class="line"><span class="cl"><span class="w"></span><span class="p">}</span><span class="w">
+</span></span></span></code></pre></div></div>
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+        <svg t="1688628374733" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3166" width="16" height="16"><path d="M966.4 668.8l-435.2-432c-9.6-9.6-25.6-9.6-35.2 0l-441.6 432c-9.6 9.6-9.6 25.6 0 35.2 9.6 9.6 25.6 9.6 35.2 0l425.6-416 416 416c9.6 9.6 25.6 9.6 35.2 0S976 678.4 966.4 668.8z" p-id="3167" fill="#424242"></path></svg>
+    </a>
+</div>
+    <footer class="footer">
+    <div id="footer_powered_by" class="powered_by">
+        <a href="https://varkai.com">Designed by VarKai,</a>
+        <a href="http://www.gohugo.io/">Proudly published with Hugo</a>
+    </div>
+
+    <div id="footer_slogan" class="footer_slogan">
+        <span>from 2021</span>
+    </div>
+</footer>
+    <script src="https://whiteppure.github.io/iblog/js/jquery-3.5.1.min.js"></script>
+<link href="https://whiteppure.github.io/iblog/css/fancybox.min.css" rel="stylesheet">
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\ No newline at end of file
diff --git a/docs/tags/docker/index.html b/docs/tags/docker/index.html
index fc2d1185..2204d497 100644
--- a/docs/tags/docker/index.html
+++ b/docs/tags/docker/index.html
@@ -169,7 +169,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/docker-start/">Docker入门</a>
+                            <a href="/iblog/posts/intro/docker-start/">Docker入门</a>
                             <div class="post_time"><span class="date">04-07</span></div>
                         </div>
                     </div>
diff --git a/docs/tags/docker/index.xml b/docs/tags/docker/index.xml
index d656fcfa..7f621aa6 100644
--- a/docs/tags/docker/index.xml
+++ b/docs/tags/docker/index.xml
@@ -17,9 +17,9 @@
     </item>
     <item>
       <title>Docker入门</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/docker-start/</link>
+      <link>https://whiteppure.github.io/iblog/posts/intro/docker-start/</link>
       <pubDate>Tue, 07 Apr 2020 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/docker-start/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/docker-start/</guid>
       <description>概述 Docker属于Linux容器的一种封装，提供简单易用的容器使用接口。它是目前流行的Linux容器解决方案。Docker将应用程序与该程序的依赖，打包在一个</description>
     </item>
   </channel>
diff --git a/docs/tags/elasticsearch/index.html b/docs/tags/elasticsearch/index.html
index a55e7fab..529a1b5a 100644
--- a/docs/tags/elasticsearch/index.html
+++ b/docs/tags/elasticsearch/index.html
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/elasticsearch/">Elasticsearch详解</a>
+                            <a href="/iblog/posts/detailed/elasticsearch/">Elasticsearch详解</a>
                             <div class="post_time"><span class="date">02-14</span></div>
                         </div>
                     </div>
diff --git a/docs/tags/elasticsearch/index.xml b/docs/tags/elasticsearch/index.xml
index 1a015e80..5d78fbd9 100644
--- a/docs/tags/elasticsearch/index.xml
+++ b/docs/tags/elasticsearch/index.xml
@@ -10,9 +10,9 @@
     <atom:link href="https://whiteppure.github.io/iblog/tags/elasticsearch/index.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>Elasticsearch详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/elasticsearch/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/elasticsearch/</link>
       <pubDate>Tue, 14 Feb 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/elasticsearch/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/elasticsearch/</guid>
       <description>概览 Elasticsearch，简称为 ES， ES是一个开源的高扩展的分布式全文搜索引擎， 是整个 ElasticStack 技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可</description>
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diff --git a/docs/tags/index.html b/docs/tags/index.html
index b9a40ddf..8b90b43b 100644
--- a/docs/tags/index.html
+++ b/docs/tags/index.html
@@ -132,7 +132,7 @@ <h1>
                     
                     <li>
                         <a href="https://whiteppure.github.io/iblog/tags/java">
-                            java <span class="terms_count">46</span>
+                            java <span class="terms_count">49</span>
                         </a>
                     </li>
                     
@@ -155,40 +155,40 @@ <h1>
                     
                     
                     <li>
-                        <a href="https://whiteppure.github.io/iblog/tags/jvm">
-                            jvm <span class="terms_count">15</span>
+                        <a href="https://whiteppure.github.io/iblog/tags/%E8%AF%A6%E8%A7%A3">
+                            详解 <span class="terms_count">17</span>
                         </a>
                     </li>
                     
                     
                     
                     <li>
-                        <a href="https://whiteppure.github.io/iblog/tags/%E8%AF%A6%E8%A7%A3">
-                            详解 <span class="terms_count">15</span>
+                        <a href="https://whiteppure.github.io/iblog/tags/jvm">
+                            jvm <span class="terms_count">15</span>
                         </a>
                     </li>
                     
                     
                     
                     <li>
-                        <a href="https://whiteppure.github.io/iblog/tags/%E5%8F%8D%E6%80%9D%E4%B8%8E%E6%84%9F%E6%82%9F">
-                            反思与感悟 <span class="terms_count">11</span>
+                        <a href="https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7">
+                            玩具 <span class="terms_count">13</span>
                         </a>
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                     <li>
-                        <a href="https://whiteppure.github.io/iblog/tags/java%E5%9F%BA%E7%A1%80">
-                            java基础 <span class="terms_count">10</span>
+                        <a href="https://whiteppure.github.io/iblog/tags/%E5%8F%8D%E6%80%9D%E4%B8%8E%E6%84%9F%E6%82%9F">
+                            反思与感悟 <span class="terms_count">11</span>
                         </a>
                     </li>
                     
                     
                     
                     <li>
-                        <a href="https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7">
-                            玩具 <span class="terms_count">10</span>
+                        <a href="https://whiteppure.github.io/iblog/tags/java%E5%9F%BA%E7%A1%80">
+                            java基础 <span class="terms_count">10</span>
                         </a>
                     </li>
                     
@@ -442,14 +442,6 @@ <h1>
                     
                     
                     
-                    <li>
-                        <a href="https://whiteppure.github.io/iblog/tags/%E7%AE%97%E6%B3%95">
-                            算法 <span class="terms_count">1</span>
-                        </a>
-                    </li>
-                    
-                    
-                    
                     <li>
                         <a href="https://whiteppure.github.io/iblog/tags/%E7%BD%91%E7%BB%9C">
                             网络 <span class="terms_count">1</span>
diff --git a/docs/tags/index.xml b/docs/tags/index.xml
index 221b95dd..83c6e1f0 100644
--- a/docs/tags/index.xml
+++ b/docs/tags/index.xml
@@ -218,6 +218,13 @@
       <guid>https://whiteppure.github.io/iblog/tags/springboot/</guid>
       <description></description>
     </item>
+    <item>
+      <title>玩具</title>
+      <link>https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/</link>
+      <pubDate>Fri, 11 Aug 2023 00:00:00 +0000</pubDate>
+      <guid>https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/</guid>
+      <description></description>
+    </item>
     <item>
       <title>技巧</title>
       <link>https://whiteppure.github.io/iblog/tags/%E6%8A%80%E5%B7%A7/</link>
@@ -232,20 +239,6 @@
       <guid>https://whiteppure.github.io/iblog/tags/elasticsearch/</guid>
       <description></description>
     </item>
-    <item>
-      <title>玩具</title>
-      <link>https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/</link>
-      <pubDate>Sat, 09 Apr 2022 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/</guid>
-      <description></description>
-    </item>
-    <item>
-      <title>算法</title>
-      <link>https://whiteppure.github.io/iblog/tags/%E7%AE%97%E6%B3%95/</link>
-      <pubDate>Fri, 10 Dec 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/tags/%E7%AE%97%E6%B3%95/</guid>
-      <description></description>
-    </item>
     <item>
       <title>网络</title>
       <link>https://whiteppure.github.io/iblog/tags/%E7%BD%91%E7%BB%9C/</link>
diff --git a/docs/tags/java/index.html b/docs/tags/java/index.html
index 145476bc..d1896c7d 100644
--- a/docs/tags/java/index.html
+++ b/docs/tags/java/index.html
@@ -169,7 +169,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-generics/">Java泛型</a>
+                            <a href="/iblog/posts/javabasics/rookie-generics/">Java泛型</a>
                             <div class="post_time"><span class="date">07-15</span></div>
                         </div>
                     </div>
@@ -183,21 +183,21 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/java-keyword-volatile/">volatile关键字详解</a>
+                            <a href="/iblog/posts/javakeyword/java-keyword-volatile/">volatile关键字</a>
                             <div class="post_time"><span class="date">07-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/java-keyword-synchronized/">synchronized关键字详解</a>
+                            <a href="/iblog/posts/javakeyword/java-keyword-synchronized/">synchronized关键字</a>
                             <div class="post_time"><span class="date">07-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-arraylist/">ArrayList详解</a>
+                            <a href="/iblog/posts/detailed/java-arraylist/">ArrayList详解</a>
                             <div class="post_time"><span class="date">06-26</span></div>
                         </div>
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@@ -211,7 +211,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-always-problems/">Java程序常见问题</a>
+                            <a href="/iblog/posts/codeguide/java-always-problems/">Java程序常见问题</a>
                             <div class="post_time"><span class="date">05-28</span></div>
                         </div>
                     </div>
@@ -242,6 +242,27 @@ <h1>
                 <div class="listing_title">2023</div>
                 <div class="listing">
                     
+                    <div class="listing_item">
+                        <div class="listing_post">
+                            <a href="/iblog/posts/toy/uploadfile-code/">Java整合文件上传功能</a>
+                            <div class="post_time"><span class="date">08-11</span></div>
+                        </div>
+                    </div>
+                    
+                    <div class="listing_item">
+                        <div class="listing_post">
+                            <a href="/iblog/posts/toy/pay-code/">Java整合支付功能</a>
+                            <div class="post_time"><span class="date">08-10</span></div>
+                        </div>
+                    </div>
+                    
+                    <div class="listing_item">
+                        <div class="listing_post">
+                            <a href="/iblog/posts/toy/pipeline-business/">Java管道流设计模式结合业务</a>
+                            <div class="post_time"><span class="date">06-15</span></div>
+                        </div>
+                    </div>
+                    
                     <div class="listing_item">
                         <div class="listing_post">
                             <a href="/iblog/posts/spring/java-spring-mvc-webflux/">SpringMVC与SpringWebFlux</a>
@@ -263,7 +284,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-design/">如何做好程序设计功能</a>
+                            <a href="/iblog/posts/codeguide/java-design/">如何做好程序设计功能</a>
                             <div class="post_time"><span class="date">08-02</span></div>
                         </div>
                     </div>
@@ -282,7 +303,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/data-structures-algorithms/">数据结构与算法</a>
+                            <a href="/iblog/posts/detailed/data-structures-algorithms/">数据结构与算法详解</a>
                             <div class="post_time"><span class="date">12-10</span></div>
                         </div>
                     </div>
@@ -296,28 +317,28 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-java-container/">Java集合</a>
+                            <a href="/iblog/posts/javabasics/rookie-java-container/">Java集合</a>
                             <div class="post_time"><span class="date">10-04</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-reflect/">Java反射</a>
+                            <a href="/iblog/posts/javabasics/rookie-reflect/">Java反射</a>
                             <div class="post_time"><span class="date">10-02</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/eye-beam/">Java程序常见故障排查命令及工具</a>
+                            <a href="/iblog/posts/codeguide/eye-beam/">Java程序常见故障排查命令及工具</a>
                             <div class="post_time"><span class="date">09-08</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-objectclass-methods/">JavaObject类方法</a>
+                            <a href="/iblog/posts/javabasics/rookie-objectclass-methods/">JavaObject类方法</a>
                             <div class="post_time"><span class="date">07-10</span></div>
                         </div>
                     </div>
@@ -338,14 +359,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-multi-thread/">Java多线程</a>
+                            <a href="/iblog/posts/javabasics/rookie-multi-thread/">Java多线程</a>
                             <div class="post_time"><span class="date">05-05</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-hashmap/">HashMap详解</a>
+                            <a href="/iblog/posts/detailed/java-hashmap/">HashMap详解</a>
                             <div class="post_time"><span class="date">05-03</span></div>
                         </div>
                     </div>
@@ -387,7 +408,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-io/">JavaIO</a>
+                            <a href="/iblog/posts/javabasics/rookie-io/">JavaIO</a>
                             <div class="post_time"><span class="date">04-09</span></div>
                         </div>
                     </div>
@@ -443,7 +464,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-object-oriented/">Java面向对象</a>
+                            <a href="/iblog/posts/javabasics/rookie-object-oriented/">Java面向对象</a>
                             <div class="post_time"><span class="date">02-15</span></div>
                         </div>
                     </div>
@@ -457,21 +478,21 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-operation/">Java运算</a>
+                            <a href="/iblog/posts/javabasics/rookie-operation/">Java运算</a>
                             <div class="post_time"><span class="date">01-30</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-datatype/">Java数据类型</a>
+                            <a href="/iblog/posts/javabasics/rookie-datatype/">Java数据类型</a>
                             <div class="post_time"><span class="date">01-20</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-exception/">Java异常</a>
+                            <a href="/iblog/posts/javabasics/rookie-exception/">Java异常</a>
                             <div class="post_time"><span class="date">01-13</span></div>
                         </div>
                     </div>
diff --git a/docs/tags/java/index.xml b/docs/tags/java/index.xml
index 7fc1bbd8..8939cc81 100644
--- a/docs/tags/java/index.xml
+++ b/docs/tags/java/index.xml
@@ -17,9 +17,9 @@
     </item>
     <item>
       <title>Java泛型</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-generics/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-generics/</link>
       <pubDate>Mon, 15 Jul 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-generics/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-generics/</guid>
       <description>概览 在Java中，泛型是一种强大的编程特性，允许类、接口和方法在定义时声明一种参数化类型，而在使用时可以指定具体的类型参数。泛型的主要目的是提高代码的重用性和类</description>
     </item>
     <item>
@@ -30,14 +30,14 @@
       <description>概览 语法糖是指编程语言中的一种语法结构，它们并不提供新的功能，而是为了让代码更易读、更易写而设计的。 语法糖使得某些常见的编程模式或操作变得更加简洁和直观，但在底</description>
     </item>
     <item>
-      <title>synchronized关键字详解</title>
+      <title>synchronized关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</guid>
       <description>synchronized synchronized是Java提供的关键字译为同步，是Java中用于实现线程同步的一种机制。它可以确保在同一时间只有一个线程能够执行某段代码，从而避免线程</description>
     </item>
     <item>
-      <title>volatile关键字详解</title>
+      <title>volatile关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</guid>
@@ -45,9 +45,9 @@
     </item>
     <item>
       <title>ArrayList详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</link>
       <pubDate>Wed, 26 Jun 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</guid>
       <description>ArrayList 在List接口实现类中，最常用的就是ArrayList，ArrayList类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删</description>
     </item>
     <item>
@@ -59,9 +59,9 @@
     </item>
     <item>
       <title>Java程序常见问题</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-always-problems/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-always-problems/</link>
       <pubDate>Tue, 28 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-always-problems/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-always-problems/</guid>
       <description>CPU使用过高 一般在生产环境排查程序故障，都会查看日志什么的，但是有些故障日志是看不出来的，就比如：CPU使用过高。 那应该怎么办呢？我们需要结合linux命令和</description>
     </item>
     <item>
@@ -85,6 +85,27 @@
       <guid>https://whiteppure.github.io/iblog/posts/keepupd/valuable-resource/</guid>
       <description>读书推荐 Java电子书 《深入理解计算机系统》 《HeadFirst设计模式》 《Java数据结构和算法》 《大话数据结构》 《Java核心技术卷I基础知识》 《Java编</description>
     </item>
+    <item>
+      <title>Java整合文件上传功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</link>
+      <pubDate>Fri, 11 Aug 2023 00:00:00 +0000</pubDate>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</guid>
+      <description>结构 pom.xml fastdfs-client-java-1.27.jar：点击下载 &amp;lt;dependencies&amp;gt; &amp;lt;!-- fastdfs --&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.csource&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;fastdfs-client-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;1.27&amp;lt;/version&amp;gt; &amp;lt;systemPath&amp;gt;${project.basedir}/lib/fastdfs-client-java-1.27.jar&amp;lt;/systemPath&amp;gt; &amp;lt;scope&amp;gt;system&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;!--aliyun oss 依赖--&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.aliyun.oss&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;aliyun-sdk-oss&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt;</description>
+    </item>
+    <item>
+      <title>Java整合支付功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pay-code/</link>
+      <pubDate>Thu, 10 Aug 2023 00:00:00 +0000</pubDate>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pay-code/</guid>
+      <description>结构 完整代码：https://gitee.com/gitee_pikaqiu/easy-archetype pom.xml &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.alipay.sdk&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;alipay-sdk-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;4.9.9&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt;</description>
+    </item>
+    <item>
+      <title>Java管道流设计模式结合业务</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</link>
+      <pubDate>Thu, 15 Jun 2023 00:00:00 +0000</pubDate>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</guid>
+      <description>流程图 代码实现 完整代码：https://gitee.com/gitee_pikaqiu/easy-pipeline pom &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.plugin&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-plugin-core&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;${spring.plugin.core.version}&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt;</description>
+    </item>
     <item>
       <title>SpringMVC与SpringWebFlux</title>
       <link>https://whiteppure.github.io/iblog/posts/spring/java-spring-mvc-webflux/</link>
@@ -101,9 +122,9 @@
     </item>
     <item>
       <title>如何做好程序设计功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-design/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-design/</link>
       <pubDate>Tue, 02 Aug 2022 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-design/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-design/</guid>
       <description>功能设计流程图 与外部系统交互、本系统模块之间流程，比较好用的画圈软件draw .io或在线的process on 数据库设计 从DDD角度界限上下文、ER图、评审表结构设</description>
     </item>
     <item>
@@ -114,10 +135,10 @@
       <description>写在前面 本文中所涉及的程序均为Java开发，如果您想要直接使用这些工具需要提前配置Java环境。所涉及到的程序均提供完整代码，如果您有兴趣可以尝试运行。 使用ja</description>
     </item>
     <item>
-      <title>数据结构与算法</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/data-structures-algorithms/</link>
+      <title>数据结构与算法详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/data-structures-algorithms/</link>
       <pubDate>Fri, 10 Dec 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/data-structures-algorithms/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/data-structures-algorithms/</guid>
       <description>数据结构 数据结构是一门研究组织数据方式的学科，有了编程语言也就有了数据结构，学好数据结构可以编写出更有效率的代码。数据结构是算法的基础，想要学好算法，就必须把数</description>
     </item>
     <item>
@@ -129,30 +150,30 @@
     </item>
     <item>
       <title>Java集合</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-java-container/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-java-container/</link>
       <pubDate>Mon, 04 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-java-container/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-java-container/</guid>
       <description>概述 Java中的集合主要包括Collection和Map两种，Collection存储着对象的集合，而Map存储着键值对的映射表。 数组 如果你看过ArrayLis</description>
     </item>
     <item>
       <title>Java反射</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-reflect/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-reflect/</link>
       <pubDate>Sat, 02 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-reflect/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-reflect/</guid>
       <description>概述 在Java程序运行状态中，对于任意一个实体类，都能够知道这个类的所有属性和方法，对于任意一个对象，都能够调用它的任意方法和属性。这种动态获取信息以及动态调用</description>
     </item>
     <item>
       <title>Java程序常见故障排查命令及工具</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/eye-beam/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/eye-beam/</link>
       <pubDate>Wed, 08 Sep 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/eye-beam/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/eye-beam/</guid>
       <description>故障排查命令 收录Linux常用命令，以下命令来自https://www.bilibili.com/video/BV14A411378a 关机/重启/注销 常用命令 作</description>
     </item>
     <item>
       <title>JavaObject类方法</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-objectclass-methods/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-objectclass-methods/</link>
       <pubDate>Sat, 10 Jul 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-objectclass-methods/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-objectclass-methods/</guid>
       <description>概览 Object类位于java.lang包中，编译时会自动导入。当我们创建一个类时，如果没有明确继承一个父类，那么它就会自动继承Object，成为Object的</description>
     </item>
     <item>
@@ -171,16 +192,16 @@
     </item>
     <item>
       <title>Java多线程</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-multi-thread/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-multi-thread/</link>
       <pubDate>Wed, 05 May 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-multi-thread/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-multi-thread/</guid>
       <description>线程与进程 进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。 线程是操作系统能够进行运算调度的最小单位。它被包</description>
     </item>
     <item>
       <title>HashMap详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</link>
       <pubDate>Mon, 03 May 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</guid>
       <description>HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问</description>
     </item>
     <item>
@@ -220,9 +241,9 @@
     </item>
     <item>
       <title>JavaIO</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-io/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-io/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-io/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-io/</guid>
       <description>概览 IO，即in和out的缩写，也就是输入和输出，指应用程序和外部设备之间的数据传递，常见的外部设备包括文件、管道、网络连接。 从计算机结构的角度来看IO，IO就</description>
     </item>
     <item>
@@ -276,9 +297,9 @@
     </item>
     <item>
       <title>Java面向对象</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-object-oriented/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-object-oriented/</link>
       <pubDate>Mon, 15 Feb 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-object-oriented/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-object-oriented/</guid>
       <description>概览 面向对象简称OO(object-oriented)是相对面向过程(procedure-oriented)来说的，是一种编程思想，Java就是一门面向对象的语</description>
     </item>
     <item>
@@ -290,23 +311,23 @@
     </item>
     <item>
       <title>Java运算</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-operation/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-operation/</link>
       <pubDate>Sat, 30 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-operation/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-operation/</guid>
       <description>运算符与表达式 运算符 运算符指明对操作数的运算方式。组成表达式的Java操作符有很多种。 运算符按照其要求的操作数数目来分，可以有单目运算符、双目运算符和三目运算符</description>
     </item>
     <item>
       <title>Java数据类型</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-datatype/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-datatype/</link>
       <pubDate>Wed, 20 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-datatype/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-datatype/</guid>
       <description>基本类型 Java语言提供了八种基本类型。六种数值类型（四个整数型，两个浮点型），一种字符类型，还有一种布尔型，俗称4类8种。 这里只介绍称4类8种，实际上，Jav</description>
     </item>
     <item>
       <title>Java异常</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-exception/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-exception/</link>
       <pubDate>Wed, 13 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-exception/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-exception/</guid>
       <description>异常类型 Throwable可以用来表示任何可以作为异常抛出的类，分为两种：Error 和 Exception。 其中Error用来表示Java程序无法处理的错误，这类</description>
     </item>
     <item>
diff --git "a/docs/tags/java\345\237\272\347\241\200/index.html" "b/docs/tags/java\345\237\272\347\241\200/index.html"
index bb3a644f..f294085a 100644
--- "a/docs/tags/java\345\237\272\347\241\200/index.html"
+++ "b/docs/tags/java\345\237\272\347\241\200/index.html"
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-generics/">Java泛型</a>
+                            <a href="/iblog/posts/javabasics/rookie-generics/">Java泛型</a>
                             <div class="post_time"><span class="date">07-15</span></div>
                         </div>
                     </div>
@@ -174,63 +174,63 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-java-container/">Java集合</a>
+                            <a href="/iblog/posts/javabasics/rookie-java-container/">Java集合</a>
                             <div class="post_time"><span class="date">10-04</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-reflect/">Java反射</a>
+                            <a href="/iblog/posts/javabasics/rookie-reflect/">Java反射</a>
                             <div class="post_time"><span class="date">10-02</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-objectclass-methods/">JavaObject类方法</a>
+                            <a href="/iblog/posts/javabasics/rookie-objectclass-methods/">JavaObject类方法</a>
                             <div class="post_time"><span class="date">07-10</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-multi-thread/">Java多线程</a>
+                            <a href="/iblog/posts/javabasics/rookie-multi-thread/">Java多线程</a>
                             <div class="post_time"><span class="date">05-05</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-io/">JavaIO</a>
+                            <a href="/iblog/posts/javabasics/rookie-io/">JavaIO</a>
                             <div class="post_time"><span class="date">04-09</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-object-oriented/">Java面向对象</a>
+                            <a href="/iblog/posts/javabasics/rookie-object-oriented/">Java面向对象</a>
                             <div class="post_time"><span class="date">02-15</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-operation/">Java运算</a>
+                            <a href="/iblog/posts/javabasics/rookie-operation/">Java运算</a>
                             <div class="post_time"><span class="date">01-30</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-datatype/">Java数据类型</a>
+                            <a href="/iblog/posts/javabasics/rookie-datatype/">Java数据类型</a>
                             <div class="post_time"><span class="date">01-20</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/java/rookie-exception/">Java异常</a>
+                            <a href="/iblog/posts/javabasics/rookie-exception/">Java异常</a>
                             <div class="post_time"><span class="date">01-13</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/java\345\237\272\347\241\200/index.xml" "b/docs/tags/java\345\237\272\347\241\200/index.xml"
index 601ec9dd..e95118ee 100644
--- "a/docs/tags/java\345\237\272\347\241\200/index.xml"
+++ "b/docs/tags/java\345\237\272\347\241\200/index.xml"
@@ -10,72 +10,72 @@
     <atom:link href="https://whiteppure.github.io/iblog/tags/java%E5%9F%BA%E7%A1%80/index.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>Java泛型</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-generics/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-generics/</link>
       <pubDate>Mon, 15 Jul 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-generics/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-generics/</guid>
       <description>概览 在Java中，泛型是一种强大的编程特性，允许类、接口和方法在定义时声明一种参数化类型，而在使用时可以指定具体的类型参数。泛型的主要目的是提高代码的重用性和类</description>
     </item>
     <item>
       <title>Java集合</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-java-container/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-java-container/</link>
       <pubDate>Mon, 04 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-java-container/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-java-container/</guid>
       <description>概述 Java中的集合主要包括Collection和Map两种，Collection存储着对象的集合，而Map存储着键值对的映射表。 数组 如果你看过ArrayLis</description>
     </item>
     <item>
       <title>Java反射</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-reflect/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-reflect/</link>
       <pubDate>Sat, 02 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-reflect/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-reflect/</guid>
       <description>概述 在Java程序运行状态中，对于任意一个实体类，都能够知道这个类的所有属性和方法，对于任意一个对象，都能够调用它的任意方法和属性。这种动态获取信息以及动态调用</description>
     </item>
     <item>
       <title>JavaObject类方法</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-objectclass-methods/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-objectclass-methods/</link>
       <pubDate>Sat, 10 Jul 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-objectclass-methods/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-objectclass-methods/</guid>
       <description>概览 Object类位于java.lang包中，编译时会自动导入。当我们创建一个类时，如果没有明确继承一个父类，那么它就会自动继承Object，成为Object的</description>
     </item>
     <item>
       <title>Java多线程</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-multi-thread/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-multi-thread/</link>
       <pubDate>Wed, 05 May 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-multi-thread/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-multi-thread/</guid>
       <description>线程与进程 进程是一个具有一定独立功能的程序关于某个数据集合的一次运行活动。一个正在运行的程序的实例就是一个进程。 线程是操作系统能够进行运算调度的最小单位。它被包</description>
     </item>
     <item>
       <title>JavaIO</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-io/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-io/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-io/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-io/</guid>
       <description>概览 IO，即in和out的缩写，也就是输入和输出，指应用程序和外部设备之间的数据传递，常见的外部设备包括文件、管道、网络连接。 从计算机结构的角度来看IO，IO就</description>
     </item>
     <item>
       <title>Java面向对象</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-object-oriented/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-object-oriented/</link>
       <pubDate>Mon, 15 Feb 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-object-oriented/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-object-oriented/</guid>
       <description>概览 面向对象简称OO(object-oriented)是相对面向过程(procedure-oriented)来说的，是一种编程思想，Java就是一门面向对象的语</description>
     </item>
     <item>
       <title>Java运算</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-operation/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-operation/</link>
       <pubDate>Sat, 30 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-operation/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-operation/</guid>
       <description>运算符与表达式 运算符 运算符指明对操作数的运算方式。组成表达式的Java操作符有很多种。 运算符按照其要求的操作数数目来分，可以有单目运算符、双目运算符和三目运算符</description>
     </item>
     <item>
       <title>Java数据类型</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-datatype/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-datatype/</link>
       <pubDate>Wed, 20 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-datatype/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-datatype/</guid>
       <description>基本类型 Java语言提供了八种基本类型。六种数值类型（四个整数型，两个浮点型），一种字符类型，还有一种布尔型，俗称4类8种。 这里只介绍称4类8种，实际上，Jav</description>
     </item>
     <item>
       <title>Java异常</title>
-      <link>https://whiteppure.github.io/iblog/posts/java/rookie-exception/</link>
+      <link>https://whiteppure.github.io/iblog/posts/javabasics/rookie-exception/</link>
       <pubDate>Wed, 13 Jan 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/java/rookie-exception/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/javabasics/rookie-exception/</guid>
       <description>异常类型 Throwable可以用来表示任何可以作为异常抛出的类，分为两种：Error 和 Exception。 其中Error用来表示Java程序无法处理的错误，这类</description>
     </item>
   </channel>
diff --git a/docs/tags/mq/index.html b/docs/tags/mq/index.html
index d4ae53dd..95dc5e3b 100644
--- a/docs/tags/mq/index.html
+++ b/docs/tags/mq/index.html
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-mq/">MQ详解</a>
+                            <a href="/iblog/posts/detailed/java-mq/">Kafka详解</a>
                             <div class="post_time"><span class="date">10-19</span></div>
                         </div>
                     </div>
diff --git a/docs/tags/mq/index.xml b/docs/tags/mq/index.xml
index 97ba4116..4c776c7d 100644
--- a/docs/tags/mq/index.xml
+++ b/docs/tags/mq/index.xml
@@ -9,10 +9,10 @@
     <lastBuildDate>Tue, 19 Oct 2021 00:00:00 +0000</lastBuildDate>
     <atom:link href="https://whiteppure.github.io/iblog/tags/mq/index.xml" rel="self" type="application/rss+xml" />
     <item>
-      <title>MQ详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-mq/</link>
+      <title>Kafka详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-mq/</link>
       <pubDate>Tue, 19 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-mq/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-mq/</guid>
       <description>概览 MQ 即 messagequeue 消息队列，是分布式系统的重要组件，主要解决异步消息，应用解耦，消峰等问题。从而实现高可用，高性能，可伸缩和最终一致性的架构。使用较多的MQ有：acti</description>
     </item>
     <item>
diff --git a/docs/tags/mysql/index.html b/docs/tags/mysql/index.html
index dea9b1eb..da0b7e1e 100644
--- a/docs/tags/mysql/index.html
+++ b/docs/tags/mysql/index.html
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/sql-select-fast/">MySQL详解</a>
+                            <a href="/iblog/posts/detailed/sql-select-fast/">MySQL详解</a>
                             <div class="post_time"><span class="date">05-30</span></div>
                         </div>
                     </div>
diff --git a/docs/tags/mysql/index.xml b/docs/tags/mysql/index.xml
index af5dec13..739b8314 100644
--- a/docs/tags/mysql/index.xml
+++ b/docs/tags/mysql/index.xml
@@ -10,9 +10,9 @@
     <atom:link href="https://whiteppure.github.io/iblog/tags/mysql/index.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>MySQL详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/sql-select-fast/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/sql-select-fast/</link>
       <pubDate>Thu, 30 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/sql-select-fast/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/sql-select-fast/</guid>
       <description>MySQL介绍 MySQL 是一种关系型数据库，主要用于持久化存储我们系统中的一些数据。 MySQL 如此流行的原因，主要具有下面这些优点： 成熟稳定，功能完善。 开源免费。 文档丰富，既有</description>
     </item>
   </channel>
diff --git a/docs/tags/netty/index.html b/docs/tags/netty/index.html
index 53383514..8b9f860e 100644
--- a/docs/tags/netty/index.html
+++ b/docs/tags/netty/index.html
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-netty/">Netty详解</a>
+                            <a href="/iblog/posts/detailed/java-netty/">Netty详解</a>
                             <div class="post_time"><span class="date">04-09</span></div>
                         </div>
                     </div>
diff --git a/docs/tags/netty/index.xml b/docs/tags/netty/index.xml
index 1edc26eb..95444a9b 100644
--- a/docs/tags/netty/index.xml
+++ b/docs/tags/netty/index.xml
@@ -10,9 +10,9 @@
     <atom:link href="https://whiteppure.github.io/iblog/tags/netty/index.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>Netty详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-netty/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-netty/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-netty/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-netty/</guid>
       <description>Netty 参考文章：https://dongzl.github.io/netty-handbook/#/ 概述 Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers &amp;amp; clients. Netty 是一个异步的、基于事</description>
     </item>
   </channel>
diff --git a/docs/tags/nginx/index.html b/docs/tags/nginx/index.html
index 5c325e84..975f04f8 100644
--- a/docs/tags/nginx/index.html
+++ b/docs/tags/nginx/index.html
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/nginx-start/">Nginx介绍</a>
+                            <a href="/iblog/posts/intro/nginx-start/">Nginx入门</a>
                             <div class="post_time"><span class="date">03-04</span></div>
                         </div>
                     </div>
diff --git a/docs/tags/nginx/index.xml b/docs/tags/nginx/index.xml
index 49f88d68..558f907f 100644
--- a/docs/tags/nginx/index.xml
+++ b/docs/tags/nginx/index.xml
@@ -9,10 +9,10 @@
     <lastBuildDate>Thu, 04 Mar 2021 00:00:00 +0000</lastBuildDate>
     <atom:link href="https://whiteppure.github.io/iblog/tags/nginx/index.xml" rel="self" type="application/rss+xml" />
     <item>
-      <title>Nginx介绍</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/nginx-start/</link>
+      <title>Nginx入门</title>
+      <link>https://whiteppure.github.io/iblog/posts/intro/nginx-start/</link>
       <pubDate>Thu, 04 Mar 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/nginx-start/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/nginx-start/</guid>
       <description>Nginx介绍 Nginx (&amp;ldquo;engine x&amp;rdquo;)是一个高性能的HTTP和反向代理服务器，特点是占有内存少，并发能力强，事实上Nginx的并发能力确实在同类型的网页服务器中表</description>
     </item>
   </channel>
diff --git a/docs/tags/redis/index.html b/docs/tags/redis/index.html
index d008ea49..d5fd6a6b 100644
--- a/docs/tags/redis/index.html
+++ b/docs/tags/redis/index.html
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-redis/">Redis详解</a>
+                            <a href="/iblog/posts/detailed/java-redis/">Redis详解</a>
                             <div class="post_time"><span class="date">06-17</span></div>
                         </div>
                     </div>
diff --git a/docs/tags/redis/index.xml b/docs/tags/redis/index.xml
index 546cdc8b..d7c5b836 100644
--- a/docs/tags/redis/index.xml
+++ b/docs/tags/redis/index.xml
@@ -10,9 +10,9 @@
     <atom:link href="https://whiteppure.github.io/iblog/tags/redis/index.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>Redis详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-redis/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-redis/</link>
       <pubDate>Thu, 17 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-redis/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-redis/</guid>
       <description>Redis概述 参考文章： https://www.runoob.com/redis/redis-intro.html https://www.redis.com.cn/redis-interview-questions.html 什么是Redis Redis(Remote Dictionary Server) Redis 是一个开源的使用 ANSI C 语言编写、遵守 BSD 协议、支持网络、可基于内存亦可持久化的日志型、Key-Value 数据库，</description>
     </item>
     <item>
diff --git "a/docs/tags/\344\275\277\347\224\250\344\273\213\347\273\215/index.html" "b/docs/tags/\344\275\277\347\224\250\344\273\213\347\273\215/index.html"
index c21e0395..65fb65b2 100644
--- "a/docs/tags/\344\275\277\347\224\250\344\273\213\347\273\215/index.html"
+++ "b/docs/tags/\344\275\277\347\224\250\344\273\213\347\273\215/index.html"
@@ -169,7 +169,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/nginx-start/">Nginx介绍</a>
+                            <a href="/iblog/posts/intro/nginx-start/">Nginx入门</a>
                             <div class="post_time"><span class="date">03-04</span></div>
                         </div>
                     </div>
@@ -181,7 +181,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/docker-start/">Docker入门</a>
+                            <a href="/iblog/posts/intro/docker-start/">Docker入门</a>
                             <div class="post_time"><span class="date">04-07</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\344\275\277\347\224\250\344\273\213\347\273\215/index.xml" "b/docs/tags/\344\275\277\347\224\250\344\273\213\347\273\215/index.xml"
index 865bab43..a34af1ec 100644
--- "a/docs/tags/\344\275\277\347\224\250\344\273\213\347\273\215/index.xml"
+++ "b/docs/tags/\344\275\277\347\224\250\344\273\213\347\273\215/index.xml"
@@ -16,17 +16,17 @@
       <description>为什么要学习JVM 大部分Java开发人员，除了会在项目中使用到与Java平台相关的各种高精尖技术，对于Java技术的核心Java虚拟机了解甚少。 一些有一定工作经</description>
     </item>
     <item>
-      <title>Nginx介绍</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/nginx-start/</link>
+      <title>Nginx入门</title>
+      <link>https://whiteppure.github.io/iblog/posts/intro/nginx-start/</link>
       <pubDate>Thu, 04 Mar 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/nginx-start/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/nginx-start/</guid>
       <description>Nginx介绍 Nginx (&amp;ldquo;engine x&amp;rdquo;)是一个高性能的HTTP和反向代理服务器，特点是占有内存少，并发能力强，事实上Nginx的并发能力确实在同类型的网页服务器中表</description>
     </item>
     <item>
       <title>Docker入门</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/docker-start/</link>
+      <link>https://whiteppure.github.io/iblog/posts/intro/docker-start/</link>
       <pubDate>Tue, 07 Apr 2020 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/docker-start/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/docker-start/</guid>
       <description>概述 Docker属于Linux容器的一种封装，提供简单易用的容器使用接口。它是目前流行的Linux容器解决方案。Docker将应用程序与该程序的依赖，打包在一个</description>
     </item>
   </channel>
diff --git "a/docs/tags/\345\205\263\351\224\256\345\255\227/index.html" "b/docs/tags/\345\205\263\351\224\256\345\255\227/index.html"
index 1206c418..51970f4f 100644
--- "a/docs/tags/\345\205\263\351\224\256\345\255\227/index.html"
+++ "b/docs/tags/\345\205\263\351\224\256\345\255\227/index.html"
@@ -162,14 +162,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/java-keyword-volatile/">volatile关键字详解</a>
+                            <a href="/iblog/posts/javakeyword/java-keyword-volatile/">volatile关键字</a>
                             <div class="post_time"><span class="date">07-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/java-keyword-synchronized/">synchronized关键字详解</a>
+                            <a href="/iblog/posts/javakeyword/java-keyword-synchronized/">synchronized关键字</a>
                             <div class="post_time"><span class="date">07-11</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\345\205\263\351\224\256\345\255\227/index.xml" "b/docs/tags/\345\205\263\351\224\256\345\255\227/index.xml"
index 87839233..f62dd292 100644
--- "a/docs/tags/\345\205\263\351\224\256\345\255\227/index.xml"
+++ "b/docs/tags/\345\205\263\351\224\256\345\255\227/index.xml"
@@ -9,14 +9,14 @@
     <lastBuildDate>Thu, 11 Jul 2024 00:00:00 +0000</lastBuildDate>
     <atom:link href="https://whiteppure.github.io/iblog/tags/%E5%85%B3%E9%94%AE%E5%AD%97/index.xml" rel="self" type="application/rss+xml" />
     <item>
-      <title>synchronized关键字详解</title>
+      <title>synchronized关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</guid>
       <description>synchronized synchronized是Java提供的关键字译为同步，是Java中用于实现线程同步的一种机制。它可以确保在同一时间只有一个线程能够执行某段代码，从而避免线程</description>
     </item>
     <item>
-      <title>volatile关键字详解</title>
+      <title>volatile关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</guid>
diff --git "a/docs/tags/\345\205\266\344\273\226/index.html" "b/docs/tags/\345\205\266\344\273\226/index.html"
index 8867ecd0..b6480e82 100644
--- "a/docs/tags/\345\205\266\344\273\226/index.html"
+++ "b/docs/tags/\345\205\266\344\273\226/index.html"
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-always-problems/">Java程序常见问题</a>
+                            <a href="/iblog/posts/codeguide/java-always-problems/">Java程序常见问题</a>
                             <div class="post_time"><span class="date">05-28</span></div>
                         </div>
                     </div>
@@ -195,7 +195,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/eye-beam/">Java程序常见故障排查命令及工具</a>
+                            <a href="/iblog/posts/codeguide/eye-beam/">Java程序常见故障排查命令及工具</a>
                             <div class="post_time"><span class="date">09-08</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\345\205\266\344\273\226/index.xml" "b/docs/tags/\345\205\266\344\273\226/index.xml"
index 7519b128..3b3cf86e 100644
--- "a/docs/tags/\345\205\266\344\273\226/index.xml"
+++ "b/docs/tags/\345\205\266\344\273\226/index.xml"
@@ -10,9 +10,9 @@
     <atom:link href="https://whiteppure.github.io/iblog/tags/%E5%85%B6%E4%BB%96/index.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>Java程序常见问题</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-always-problems/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-always-problems/</link>
       <pubDate>Tue, 28 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-always-problems/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-always-problems/</guid>
       <description>CPU使用过高 一般在生产环境排查程序故障，都会查看日志什么的，但是有些故障日志是看不出来的，就比如：CPU使用过高。 那应该怎么办呢？我们需要结合linux命令和</description>
     </item>
     <item>
@@ -38,9 +38,9 @@
     </item>
     <item>
       <title>Java程序常见故障排查命令及工具</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/eye-beam/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/eye-beam/</link>
       <pubDate>Wed, 08 Sep 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/eye-beam/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/eye-beam/</guid>
       <description>故障排查命令 收录Linux常用命令，以下命令来自https://www.bilibili.com/video/BV14A411378a 关机/重启/注销 常用命令 作</description>
     </item>
   </channel>
diff --git "a/docs/tags/\345\210\206\345\270\203\345\274\217/index.html" "b/docs/tags/\345\210\206\345\270\203\345\274\217/index.html"
index 541d2019..234b2570 100644
--- "a/docs/tags/\345\210\206\345\270\203\345\274\217/index.html"
+++ "b/docs/tags/\345\210\206\345\270\203\345\274\217/index.html"
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/distributed-lock/">分布式锁详解</a>
+                            <a href="/iblog/posts/detailed/distributed-lock/">分布式锁详解</a>
                             <div class="post_time"><span class="date">05-25</span></div>
                         </div>
                     </div>
@@ -174,7 +174,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/distributed-id/">分布式ID</a>
+                            <a href="/iblog/posts/detailed/distributed-id/">分布式ID详解</a>
                             <div class="post_time"><span class="date">03-13</span></div>
                         </div>
                     </div>
@@ -186,14 +186,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-transaction/">分布式事务详解</a>
+                            <a href="/iblog/posts/detailed/java-transaction/">分布式事务详解</a>
                             <div class="post_time"><span class="date">08-02</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-small-service/">微服务治理详解</a>
+                            <a href="/iblog/posts/detailed/java-small-service/">微服务治理详解</a>
                             <div class="post_time"><span class="date">06-21</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\345\210\206\345\270\203\345\274\217/index.xml" "b/docs/tags/\345\210\206\345\270\203\345\274\217/index.xml"
index 626e75c4..cacee485 100644
--- "a/docs/tags/\345\210\206\345\270\203\345\274\217/index.xml"
+++ "b/docs/tags/\345\210\206\345\270\203\345\274\217/index.xml"
@@ -10,30 +10,30 @@
     <atom:link href="https://whiteppure.github.io/iblog/tags/%E5%88%86%E5%B8%83%E5%BC%8F/index.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>分布式锁详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/distributed-lock/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/distributed-lock/</link>
       <pubDate>Sat, 25 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/distributed-lock/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/distributed-lock/</guid>
       <description>概述 在代码里面我们常用ReetrantLock、synchronized保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。 类似这样： public</description>
     </item>
     <item>
-      <title>分布式ID</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/distributed-id/</link>
+      <title>分布式ID详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/distributed-id/</link>
       <pubDate>Mon, 13 Mar 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/distributed-id/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/distributed-id/</guid>
       <description>分布式ID 在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。 但随着数据日渐增长，主从同步也扛不住了，</description>
     </item>
     <item>
       <title>分布式事务详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-transaction/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-transaction/</link>
       <pubDate>Mon, 02 Aug 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-transaction/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-transaction/</guid>
       <description>基础概念 什么是事务 什么是事务？举个例子：你去超市买东西，&amp;ldquo;一手交钱，一手交货&amp;quot;就是一个事务的例子。 交钱和交货必须同时成功，事务才算成功，其</description>
     </item>
     <item>
       <title>微服务治理详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-small-service/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-small-service/</link>
       <pubDate>Mon, 21 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-small-service/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-small-service/</guid>
       <description>什么是微服务架构 In short， the microservice architectural style is an approach to developing a single application as a suite of small services， each running in its own process and communicating with lightweight mechanisms， often an HTTP resource API。 These services are built around business capabilities and independently deployable</description>
     </item>
   </channel>
diff --git "a/docs/tags/\345\255\246\344\271\240\350\267\257\347\272\277/index.html" "b/docs/tags/\345\255\246\344\271\240\350\267\257\347\272\277/index.html"
index a17bba59..4780f2d3 100644
--- "a/docs/tags/\345\255\246\344\271\240\350\267\257\347\272\277/index.html"
+++ "b/docs/tags/\345\255\246\344\271\240\350\267\257\347\272\277/index.html"
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/emp/front-learning-route/">前端学习路线</a>
+                            <a href="/iblog/posts/intro/front-learning-route/">前端学习路线</a>
                             <div class="post_time"><span class="date">02-29</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\345\255\246\344\271\240\350\267\257\347\272\277/index.xml" "b/docs/tags/\345\255\246\344\271\240\350\267\257\347\272\277/index.xml"
index 42e6b3f7..55df15d3 100644
--- "a/docs/tags/\345\255\246\344\271\240\350\267\257\347\272\277/index.xml"
+++ "b/docs/tags/\345\255\246\344\271\240\350\267\257\347\272\277/index.xml"
@@ -10,9 +10,9 @@
     <atom:link href="https://whiteppure.github.io/iblog/tags/%E5%AD%A6%E4%B9%A0%E8%B7%AF%E7%BA%BF/index.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>前端学习路线</title>
-      <link>https://whiteppure.github.io/iblog/posts/emp/front-learning-route/</link>
+      <link>https://whiteppure.github.io/iblog/posts/intro/front-learning-route/</link>
       <pubDate>Thu, 29 Feb 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/emp/front-learning-route/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/front-learning-route/</guid>
       <description>基础知识 网络知识 HTTP DNS 域名 云服务 网络安全 HTTPS CORS 网络渗透 OWASP HTML CSS JavaScript JQuery Ajax ES6-ES11 综合应用 工程化体系 代码规范 CSS预处理器 Less Sass PostCSS Node Promise Axios 工具 包管理工具 Yarn Npm 打包工具 Webpack Parcel 代码格式化工具</description>
     </item>
   </channel>
diff --git "a/docs/tags/\345\260\261\344\270\232/index.html" "b/docs/tags/\345\260\261\344\270\232/index.html"
index f2667881..b78c128d 100644
--- "a/docs/tags/\345\260\261\344\270\232/index.html"
+++ "b/docs/tags/\345\260\261\344\270\232/index.html"
@@ -176,7 +176,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/emp/front-learning-route/">前端学习路线</a>
+                            <a href="/iblog/posts/intro/front-learning-route/">前端学习路线</a>
                             <div class="post_time"><span class="date">02-29</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\345\260\261\344\270\232/index.xml" "b/docs/tags/\345\260\261\344\270\232/index.xml"
index 8c729627..673a5ca1 100644
--- "a/docs/tags/\345\260\261\344\270\232/index.xml"
+++ "b/docs/tags/\345\260\261\344\270\232/index.xml"
@@ -24,9 +24,9 @@
     </item>
     <item>
       <title>前端学习路线</title>
-      <link>https://whiteppure.github.io/iblog/posts/emp/front-learning-route/</link>
+      <link>https://whiteppure.github.io/iblog/posts/intro/front-learning-route/</link>
       <pubDate>Thu, 29 Feb 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/emp/front-learning-route/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/intro/front-learning-route/</guid>
       <description>基础知识 网络知识 HTTP DNS 域名 云服务 网络安全 HTTPS CORS 网络渗透 OWASP HTML CSS JavaScript JQuery Ajax ES6-ES11 综合应用 工程化体系 代码规范 CSS预处理器 Less Sass PostCSS Node Promise Axios 工具 包管理工具 Yarn Npm 打包工具 Webpack Parcel 代码格式化工具</description>
     </item>
     <item>
diff --git "a/docs/tags/\345\272\224\347\224\250/index.html" "b/docs/tags/\345\272\224\347\224\250/index.html"
index 267bc640..fb943874 100644
--- "a/docs/tags/\345\272\224\347\224\250/index.html"
+++ "b/docs/tags/\345\272\224\347\224\250/index.html"
@@ -169,21 +169,21 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/uploadfile-code/">整合文件上传功能</a>
+                            <a href="/iblog/posts/toy/uploadfile-code/">Java整合文件上传功能</a>
                             <div class="post_time"><span class="date">08-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/pay-code/">整合支付功能</a>
+                            <a href="/iblog/posts/toy/pay-code/">Java整合支付功能</a>
                             <div class="post_time"><span class="date">08-10</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/pipeline-business/">管道流设计模式结合业务</a>
+                            <a href="/iblog/posts/toy/pipeline-business/">Java管道流设计模式结合业务</a>
                             <div class="post_time"><span class="date">06-15</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\345\272\224\347\224\250/index.xml" "b/docs/tags/\345\272\224\347\224\250/index.xml"
index 9747d554..8b451881 100644
--- "a/docs/tags/\345\272\224\347\224\250/index.xml"
+++ "b/docs/tags/\345\272\224\347\224\250/index.xml"
@@ -16,24 +16,24 @@
       <description>代码实现 代码结构 pom &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-security&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-quartz&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; 库表结构 -- ---------------------------- -- 定时任务调度表 -- ---------------------------- drop table if exists sys_job; create table sys_job ( job_id bigint(20) not null auto_increment comment &amp;#39;任务ID&amp;#39;, job_name varchar(64) default &amp;#39;&amp;#39; comment</description>
     </item>
     <item>
-      <title>整合文件上传功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/uploadfile-code/</link>
+      <title>Java整合文件上传功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</link>
       <pubDate>Fri, 11 Aug 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/uploadfile-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</guid>
       <description>结构 pom.xml fastdfs-client-java-1.27.jar：点击下载 &amp;lt;dependencies&amp;gt; &amp;lt;!-- fastdfs --&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.csource&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;fastdfs-client-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;1.27&amp;lt;/version&amp;gt; &amp;lt;systemPath&amp;gt;${project.basedir}/lib/fastdfs-client-java-1.27.jar&amp;lt;/systemPath&amp;gt; &amp;lt;scope&amp;gt;system&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;!--aliyun oss 依赖--&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.aliyun.oss&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;aliyun-sdk-oss&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt;</description>
     </item>
     <item>
-      <title>整合支付功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/pay-code/</link>
+      <title>Java整合支付功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pay-code/</link>
       <pubDate>Thu, 10 Aug 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/pay-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pay-code/</guid>
       <description>结构 完整代码：https://gitee.com/gitee_pikaqiu/easy-archetype pom.xml &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.alipay.sdk&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;alipay-sdk-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;4.9.9&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt;</description>
     </item>
     <item>
-      <title>管道流设计模式结合业务</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/pipeline-business/</link>
+      <title>Java管道流设计模式结合业务</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</link>
       <pubDate>Thu, 15 Jun 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/pipeline-business/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</guid>
       <description>流程图 代码实现 完整代码：https://gitee.com/gitee_pikaqiu/easy-pipeline pom &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.plugin&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-plugin-core&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;${spring.plugin.core.version}&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt;</description>
     </item>
   </channel>
diff --git "a/docs/tags/\346\212\200\345\267\247/index.html" "b/docs/tags/\346\212\200\345\267\247/index.html"
index 1b8b4176..06265f5f 100644
--- "a/docs/tags/\346\212\200\345\267\247/index.html"
+++ "b/docs/tags/\346\212\200\345\267\247/index.html"
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-bugs/">如何减少及解决bug</a>
+                            <a href="/iblog/posts/codeguide/java-bugs/">如何减少及解决bug</a>
                             <div class="post_time"><span class="date">03-10</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\346\212\200\345\267\247/index.xml" "b/docs/tags/\346\212\200\345\267\247/index.xml"
index e0783076..7c8860cd 100644
--- "a/docs/tags/\346\212\200\345\267\247/index.xml"
+++ "b/docs/tags/\346\212\200\345\267\247/index.xml"
@@ -10,9 +10,9 @@
     <atom:link href="https://whiteppure.github.io/iblog/tags/%E6%8A%80%E5%B7%A7/index.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>如何减少及解决bug</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-bugs/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-bugs/</link>
       <pubDate>Fri, 10 Mar 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-bugs/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-bugs/</guid>
       <description>bug的起源: 1945年，一只小飞蛾钻进了计算机电路里，导致系统无法工作，一位名叫格蕾丝·赫柏的人把飞蛾拍死在工作日志上，写道：就是这个 bug(虫子)，害我们今</description>
     </item>
     <item>
diff --git "a/docs/tags/\347\216\251\345\205\267/index.html" "b/docs/tags/\347\216\251\345\205\267/index.html"
index 251b8872..d588ff42 100644
--- "a/docs/tags/\347\216\251\345\205\267/index.html"
+++ "b/docs/tags/\347\216\251\345\205\267/index.html"
@@ -157,6 +157,32 @@ <h1>
         <div class="content">
             <div class="list_with_title">
                 
+                <div class="listing_title">2023</div>
+                <div class="listing">
+                    
+                    <div class="listing_item">
+                        <div class="listing_post">
+                            <a href="/iblog/posts/toy/uploadfile-code/">Java整合文件上传功能</a>
+                            <div class="post_time"><span class="date">08-11</span></div>
+                        </div>
+                    </div>
+                    
+                    <div class="listing_item">
+                        <div class="listing_post">
+                            <a href="/iblog/posts/toy/pay-code/">Java整合支付功能</a>
+                            <div class="post_time"><span class="date">08-10</span></div>
+                        </div>
+                    </div>
+                    
+                    <div class="listing_item">
+                        <div class="listing_post">
+                            <a href="/iblog/posts/toy/pipeline-business/">Java管道流设计模式结合业务</a>
+                            <div class="post_time"><span class="date">06-15</span></div>
+                        </div>
+                    </div>
+                    
+                </div>
+                
                 <div class="listing_title">2022</div>
                 <div class="listing">
                     
diff --git "a/docs/tags/\347\216\251\345\205\267/index.xml" "b/docs/tags/\347\216\251\345\205\267/index.xml"
index 34a054dc..5caa7953 100644
--- "a/docs/tags/\347\216\251\345\205\267/index.xml"
+++ "b/docs/tags/\347\216\251\345\205\267/index.xml"
@@ -6,8 +6,29 @@
     <description>Recent content in 玩具 on 脚踏实地</description>
     <generator>Hugo -- gohugo.io</generator>
     <language>zh</language>
-    <lastBuildDate>Sat, 09 Apr 2022 00:00:00 +0000</lastBuildDate>
+    <lastBuildDate>Fri, 11 Aug 2023 00:00:00 +0000</lastBuildDate>
     <atom:link href="https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/index.xml" rel="self" type="application/rss+xml" />
+    <item>
+      <title>Java整合文件上传功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</link>
+      <pubDate>Fri, 11 Aug 2023 00:00:00 +0000</pubDate>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</guid>
+      <description>结构 pom.xml fastdfs-client-java-1.27.jar：点击下载 &amp;lt;dependencies&amp;gt; &amp;lt;!-- fastdfs --&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.csource&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;fastdfs-client-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;1.27&amp;lt;/version&amp;gt; &amp;lt;systemPath&amp;gt;${project.basedir}/lib/fastdfs-client-java-1.27.jar&amp;lt;/systemPath&amp;gt; &amp;lt;scope&amp;gt;system&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;!--aliyun oss 依赖--&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.aliyun.oss&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;aliyun-sdk-oss&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt;</description>
+    </item>
+    <item>
+      <title>Java整合支付功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pay-code/</link>
+      <pubDate>Thu, 10 Aug 2023 00:00:00 +0000</pubDate>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pay-code/</guid>
+      <description>结构 完整代码：https://gitee.com/gitee_pikaqiu/easy-archetype pom.xml &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.alipay.sdk&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;alipay-sdk-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;4.9.9&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt;</description>
+    </item>
+    <item>
+      <title>Java管道流设计模式结合业务</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</link>
+      <pubDate>Thu, 15 Jun 2023 00:00:00 +0000</pubDate>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</guid>
+      <description>流程图 代码实现 完整代码：https://gitee.com/gitee_pikaqiu/easy-pipeline pom &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.plugin&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-plugin-core&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;${spring.plugin.core.version}&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt;</description>
+    </item>
     <item>
       <title>Java小程序集合</title>
       <link>https://whiteppure.github.io/iblog/posts/toy/java-multi-gadget/</link>
diff --git "a/docs/tags/\347\272\277\347\250\213/index.html" "b/docs/tags/\347\272\277\347\250\213/index.html"
index ef0f236f..da6a5f5f 100644
--- "a/docs/tags/\347\272\277\347\250\213/index.html"
+++ "b/docs/tags/\347\272\277\347\250\213/index.html"
@@ -183,7 +183,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/cas-detail/">CAS详解</a>
+                            <a href="/iblog/posts/detailed/cas-detail/">CAS详解</a>
                             <div class="post_time"><span class="date">04-04</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\347\272\277\347\250\213/index.xml" "b/docs/tags/\347\272\277\347\250\213/index.xml"
index de15311a..9c0fac2c 100644
--- "a/docs/tags/\347\272\277\347\250\213/index.xml"
+++ "b/docs/tags/\347\272\277\347\250\213/index.xml"
@@ -31,9 +31,9 @@
     </item>
     <item>
       <title>CAS详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/cas-detail/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/cas-detail/</link>
       <pubDate>Sat, 04 Apr 2020 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/cas-detail/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/cas-detail/</guid>
       <description>CAS CAS全称为Compare and Swap被译为比较并交换，是一种无锁算法。用于实现并发编程中的原子操作。CAS操作检查某个变量是否与预期的值相同，如果相同则将其更</description>
     </item>
   </channel>
diff --git "a/docs/tags/\350\256\276\350\256\241/index.html" "b/docs/tags/\350\256\276\350\256\241/index.html"
index e39d1f3d..ad6dc8e6 100644
--- "a/docs/tags/\350\256\276\350\256\241/index.html"
+++ "b/docs/tags/\350\256\276\350\256\241/index.html"
@@ -169,28 +169,28 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/uploadfile-code/">整合文件上传功能</a>
+                            <a href="/iblog/posts/toy/uploadfile-code/">Java整合文件上传功能</a>
                             <div class="post_time"><span class="date">08-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/pay-code/">整合支付功能</a>
+                            <a href="/iblog/posts/toy/pay-code/">Java整合支付功能</a>
                             <div class="post_time"><span class="date">08-10</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/pipeline-business/">管道流设计模式结合业务</a>
+                            <a href="/iblog/posts/toy/pipeline-business/">Java管道流设计模式结合业务</a>
                             <div class="post_time"><span class="date">06-15</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-project-reconstitution/">重构一个程序</a>
+                            <a href="/iblog/posts/codeguide/java-project-reconstitution/">重构一个程序</a>
                             <div class="post_time"><span class="date">04-20</span></div>
                         </div>
                     </div>
@@ -202,14 +202,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/clean-code/">整洁的代码</a>
+                            <a href="/iblog/posts/codeguide/clean-code/">整洁的代码</a>
                             <div class="post_time"><span class="date">09-01</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-design/">如何做好程序设计功能</a>
+                            <a href="/iblog/posts/codeguide/java-design/">如何做好程序设计功能</a>
                             <div class="post_time"><span class="date">08-02</span></div>
                         </div>
                     </div>
@@ -221,7 +221,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-code-rule/">规范编写Java代码总结</a>
+                            <a href="/iblog/posts/codeguide/java-code-rule/">规范编写Java代码总结</a>
                             <div class="post_time"><span class="date">11-25</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\350\256\276\350\256\241/index.xml" "b/docs/tags/\350\256\276\350\256\241/index.xml"
index 1424e852..7ee4d8e1 100644
--- "a/docs/tags/\350\256\276\350\256\241/index.xml"
+++ "b/docs/tags/\350\256\276\350\256\241/index.xml"
@@ -16,52 +16,52 @@
       <description>代码实现 代码结构 pom &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-security&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-quartz&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; 库表结构 -- ---------------------------- -- 定时任务调度表 -- ---------------------------- drop table if exists sys_job; create table sys_job ( job_id bigint(20) not null auto_increment comment &amp;#39;任务ID&amp;#39;, job_name varchar(64) default &amp;#39;&amp;#39; comment</description>
     </item>
     <item>
-      <title>整合文件上传功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/uploadfile-code/</link>
+      <title>Java整合文件上传功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</link>
       <pubDate>Fri, 11 Aug 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/uploadfile-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</guid>
       <description>结构 pom.xml fastdfs-client-java-1.27.jar：点击下载 &amp;lt;dependencies&amp;gt; &amp;lt;!-- fastdfs --&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.csource&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;fastdfs-client-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;1.27&amp;lt;/version&amp;gt; &amp;lt;systemPath&amp;gt;${project.basedir}/lib/fastdfs-client-java-1.27.jar&amp;lt;/systemPath&amp;gt; &amp;lt;scope&amp;gt;system&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;!--aliyun oss 依赖--&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.aliyun.oss&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;aliyun-sdk-oss&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt;</description>
     </item>
     <item>
-      <title>整合支付功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/pay-code/</link>
+      <title>Java整合支付功能</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pay-code/</link>
       <pubDate>Thu, 10 Aug 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/pay-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pay-code/</guid>
       <description>结构 完整代码：https://gitee.com/gitee_pikaqiu/easy-archetype pom.xml &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;hutool-all&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;5.8.11&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;com.alipay.sdk&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;alipay-sdk-java&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;4.9.9&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt;</description>
     </item>
     <item>
-      <title>管道流设计模式结合业务</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/pipeline-business/</link>
+      <title>Java管道流设计模式结合业务</title>
+      <link>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</link>
       <pubDate>Thu, 15 Jun 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/pipeline-business/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</guid>
       <description>流程图 代码实现 完整代码：https://gitee.com/gitee_pikaqiu/easy-pipeline pom &amp;lt;dependencies&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-web&amp;lt;/artifactId&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.plugin&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-plugin-core&amp;lt;/artifactId&amp;gt; &amp;lt;version&amp;gt;${spring.plugin.core.version}&amp;lt;/version&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.springframework.boot&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;spring-boot-starter-test&amp;lt;/artifactId&amp;gt; &amp;lt;scope&amp;gt;test&amp;lt;/scope&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;org.projectlombok&amp;lt;/groupId&amp;gt; &amp;lt;artifactId&amp;gt;lombok&amp;lt;/artifactId&amp;gt; &amp;lt;optional&amp;gt;true&amp;lt;/optional&amp;gt; &amp;lt;/dependency&amp;gt; &amp;lt;dependency&amp;gt; &amp;lt;groupId&amp;gt;cn.hutool&amp;lt;/groupId&amp;gt;</description>
     </item>
     <item>
       <title>重构一个程序</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-project-reconstitution/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-project-reconstitution/</link>
       <pubDate>Thu, 20 Apr 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-project-reconstitution/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-project-reconstitution/</guid>
       <description>什么是重构 摘自《重构：改善既有代码的设计》 重构(名词形式): 对软件内部结构的一种调整，目的是在不改变软件可观察行为的前提下，提高其可理解性，降低其修改成本。 重构</description>
     </item>
     <item>
       <title>整洁的代码</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/clean-code/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/clean-code/</link>
       <pubDate>Thu, 01 Sep 2022 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/clean-code/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/clean-code/</guid>
       <description>为什么要写整洁的代码 为什么要写整洁的代码,回答这个问题之前,也许应该想想写糟糕的代码的原因 是想快点完成吗?还是要赶时间吗?有可能.或许你觉得自己要干好所需要的时</description>
     </item>
     <item>
       <title>如何做好程序设计功能</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-design/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-design/</link>
       <pubDate>Tue, 02 Aug 2022 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-design/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-design/</guid>
       <description>功能设计流程图 与外部系统交互、本系统模块之间流程，比较好用的画圈软件draw .io或在线的process on 数据库设计 从DDD角度界限上下文、ER图、评审表结构设</description>
     </item>
     <item>
       <title>规范编写Java代码总结</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-code-rule/</link>
+      <link>https://whiteppure.github.io/iblog/posts/codeguide/java-code-rule/</link>
       <pubDate>Thu, 25 Nov 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-code-rule/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/codeguide/java-code-rule/</guid>
       <description>编码规范 我们为什么要遵守规范来编码？ 是因为通常在编码过程中我们不只自己进行开发，通常需要一个团队来进行，开发好之后还需要维护，所以编码规范就显的尤为重要。 代码维</description>
     </item>
   </channel>
diff --git "a/docs/tags/\350\257\246\350\247\243/index.html" "b/docs/tags/\350\257\246\350\247\243/index.html"
index f5d0b0cc..ed002112 100644
--- "a/docs/tags/\350\257\246\350\247\243/index.html"
+++ "b/docs/tags/\350\257\246\350\247\243/index.html"
@@ -169,28 +169,28 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/java-keyword-volatile/">volatile关键字详解</a>
+                            <a href="/iblog/posts/javakeyword/java-keyword-volatile/">volatile关键字</a>
                             <div class="post_time"><span class="date">07-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/javakeyword/java-keyword-synchronized/">synchronized关键字详解</a>
+                            <a href="/iblog/posts/javakeyword/java-keyword-synchronized/">synchronized关键字</a>
                             <div class="post_time"><span class="date">07-11</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-arraylist/">ArrayList详解</a>
+                            <a href="/iblog/posts/detailed/java-arraylist/">ArrayList详解</a>
                             <div class="post_time"><span class="date">06-26</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/sql-select-fast/">MySQL详解</a>
+                            <a href="/iblog/posts/detailed/sql-select-fast/">MySQL详解</a>
                             <div class="post_time"><span class="date">05-30</span></div>
                         </div>
                     </div>
@@ -204,7 +204,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/distributed-lock/">分布式锁详解</a>
+                            <a href="/iblog/posts/detailed/distributed-lock/">分布式锁详解</a>
                             <div class="post_time"><span class="date">05-25</span></div>
                         </div>
                     </div>
@@ -216,7 +216,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/elasticsearch/">Elasticsearch详解</a>
+                            <a href="/iblog/posts/detailed/distributed-id/">分布式ID详解</a>
+                            <div class="post_time"><span class="date">03-13</span></div>
+                        </div>
+                    </div>
+                    
+                    <div class="listing_item">
+                        <div class="listing_post">
+                            <a href="/iblog/posts/detailed/elasticsearch/">Elasticsearch详解</a>
                             <div class="post_time"><span class="date">02-14</span></div>
                         </div>
                     </div>
@@ -228,28 +235,35 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-mq/">MQ详解</a>
+                            <a href="/iblog/posts/detailed/data-structures-algorithms/">数据结构与算法详解</a>
+                            <div class="post_time"><span class="date">12-10</span></div>
+                        </div>
+                    </div>
+                    
+                    <div class="listing_item">
+                        <div class="listing_post">
+                            <a href="/iblog/posts/detailed/java-mq/">Kafka详解</a>
                             <div class="post_time"><span class="date">10-19</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-transaction/">分布式事务详解</a>
+                            <a href="/iblog/posts/detailed/java-transaction/">分布式事务详解</a>
                             <div class="post_time"><span class="date">08-02</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-small-service/">微服务治理详解</a>
+                            <a href="/iblog/posts/detailed/java-small-service/">微服务治理详解</a>
                             <div class="post_time"><span class="date">06-21</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-redis/">Redis详解</a>
+                            <a href="/iblog/posts/detailed/java-redis/">Redis详解</a>
                             <div class="post_time"><span class="date">06-17</span></div>
                         </div>
                     </div>
@@ -263,14 +277,14 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-hashmap/">HashMap详解</a>
+                            <a href="/iblog/posts/detailed/java-hashmap/">HashMap详解</a>
                             <div class="post_time"><span class="date">05-03</span></div>
                         </div>
                     </div>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-netty/">Netty详解</a>
+                            <a href="/iblog/posts/detailed/java-netty/">Netty详解</a>
                             <div class="post_time"><span class="date">04-09</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\350\257\246\350\247\243/index.xml" "b/docs/tags/\350\257\246\350\247\243/index.xml"
index 6ba56f2d..75f3dd97 100644
--- "a/docs/tags/\350\257\246\350\247\243/index.xml"
+++ "b/docs/tags/\350\257\246\350\247\243/index.xml"
@@ -16,14 +16,14 @@
       <description>概览 SpringBoot是由Pivotal团队提供的全新框架，其设计目的是用来简化新Spring应用的初始搭建以及开发过程。 该框架使用了特定的方式来进行配置，从</description>
     </item>
     <item>
-      <title>synchronized关键字详解</title>
+      <title>synchronized关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-synchronized/</guid>
       <description>synchronized synchronized是Java提供的关键字译为同步，是Java中用于实现线程同步的一种机制。它可以确保在同一时间只有一个线程能够执行某段代码，从而避免线程</description>
     </item>
     <item>
-      <title>volatile关键字详解</title>
+      <title>volatile关键字</title>
       <link>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</link>
       <pubDate>Thu, 11 Jul 2024 00:00:00 +0000</pubDate>
       <guid>https://whiteppure.github.io/iblog/posts/javakeyword/java-keyword-volatile/</guid>
@@ -31,16 +31,16 @@
     </item>
     <item>
       <title>ArrayList详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</link>
       <pubDate>Wed, 26 Jun 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</guid>
       <description>ArrayList 在List接口实现类中，最常用的就是ArrayList，ArrayList类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删</description>
     </item>
     <item>
       <title>MySQL详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/sql-select-fast/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/sql-select-fast/</link>
       <pubDate>Thu, 30 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/sql-select-fast/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/sql-select-fast/</guid>
       <description>MySQL介绍 MySQL 是一种关系型数据库，主要用于持久化存储我们系统中的一些数据。 MySQL 如此流行的原因，主要具有下面这些优点： 成熟稳定，功能完善。 开源免费。 文档丰富，既有</description>
     </item>
     <item>
@@ -52,44 +52,58 @@
     </item>
     <item>
       <title>分布式锁详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/distributed-lock/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/distributed-lock/</link>
       <pubDate>Sat, 25 May 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/distributed-lock/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/distributed-lock/</guid>
       <description>概述 在代码里面我们常用ReetrantLock、synchronized保证线程安全。通过上面的锁，在某个时刻只能保证一个线程执行锁作用域内的代码。 类似这样： public</description>
     </item>
+    <item>
+      <title>分布式ID详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/distributed-id/</link>
+      <pubDate>Mon, 13 Mar 2023 00:00:00 +0000</pubDate>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/distributed-id/</guid>
+      <description>分布式ID 在我们业务数据量不大的时候，单库单表完全可以支撑现有业务，数据再大一点搞个MySQL主从同步读写分离也能对付。 但随着数据日渐增长，主从同步也扛不住了，</description>
+    </item>
     <item>
       <title>Elasticsearch详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/elasticsearch/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/elasticsearch/</link>
       <pubDate>Tue, 14 Feb 2023 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/elasticsearch/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/elasticsearch/</guid>
       <description>概览 Elasticsearch，简称为 ES， ES是一个开源的高扩展的分布式全文搜索引擎， 是整个 ElasticStack 技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可</description>
     </item>
     <item>
-      <title>MQ详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-mq/</link>
+      <title>数据结构与算法详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/data-structures-algorithms/</link>
+      <pubDate>Fri, 10 Dec 2021 00:00:00 +0000</pubDate>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/data-structures-algorithms/</guid>
+      <description>数据结构 数据结构是一门研究组织数据方式的学科，有了编程语言也就有了数据结构，学好数据结构可以编写出更有效率的代码。数据结构是算法的基础，想要学好算法，就必须把数</description>
+    </item>
+    <item>
+      <title>Kafka详解</title>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-mq/</link>
       <pubDate>Tue, 19 Oct 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-mq/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-mq/</guid>
       <description>概览 MQ 即 messagequeue 消息队列，是分布式系统的重要组件，主要解决异步消息，应用解耦，消峰等问题。从而实现高可用，高性能，可伸缩和最终一致性的架构。使用较多的MQ有：acti</description>
     </item>
     <item>
       <title>分布式事务详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-transaction/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-transaction/</link>
       <pubDate>Mon, 02 Aug 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-transaction/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-transaction/</guid>
       <description>基础概念 什么是事务 什么是事务？举个例子：你去超市买东西，&amp;ldquo;一手交钱，一手交货&amp;quot;就是一个事务的例子。 交钱和交货必须同时成功，事务才算成功，其</description>
     </item>
     <item>
       <title>微服务治理详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-small-service/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-small-service/</link>
       <pubDate>Mon, 21 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-small-service/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-small-service/</guid>
       <description>什么是微服务架构 In short， the microservice architectural style is an approach to developing a single application as a suite of small services， each running in its own process and communicating with lightweight mechanisms， often an HTTP resource API。 These services are built around business capabilities and independently deployable</description>
     </item>
     <item>
       <title>Redis详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-redis/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-redis/</link>
       <pubDate>Thu, 17 Jun 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-redis/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-redis/</guid>
       <description>Redis概述 参考文章： https://www.runoob.com/redis/redis-intro.html https://www.redis.com.cn/redis-interview-questions.html 什么是Redis Redis(Remote Dictionary Server) Redis 是一个开源的使用 ANSI C 语言编写、遵守 BSD 协议、支持网络、可基于内存亦可持久化的日志型、Key-Value 数据库，</description>
     </item>
     <item>
@@ -101,16 +115,16 @@
     </item>
     <item>
       <title>HashMap详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</link>
       <pubDate>Mon, 03 May 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</guid>
       <description>HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问</description>
     </item>
     <item>
       <title>Netty详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-netty/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-netty/</link>
       <pubDate>Fri, 09 Apr 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-netty/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-netty/</guid>
       <description>Netty 参考文章：https://dongzl.github.io/netty-handbook/#/ 概述 Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers &amp;amp; clients. Netty 是一个异步的、基于事</description>
     </item>
   </channel>
diff --git "a/docs/tags/\351\233\206\345\220\210/index.html" "b/docs/tags/\351\233\206\345\220\210/index.html"
index 6063d149..848dc3f3 100644
--- "a/docs/tags/\351\233\206\345\220\210/index.html"
+++ "b/docs/tags/\351\233\206\345\220\210/index.html"
@@ -162,7 +162,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-arraylist/">ArrayList详解</a>
+                            <a href="/iblog/posts/detailed/java-arraylist/">ArrayList详解</a>
                             <div class="post_time"><span class="date">06-26</span></div>
                         </div>
                     </div>
@@ -174,7 +174,7 @@ <h1>
                     
                     <div class="listing_item">
                         <div class="listing_post">
-                            <a href="/iblog/posts/essays/java-hashmap/">HashMap详解</a>
+                            <a href="/iblog/posts/detailed/java-hashmap/">HashMap详解</a>
                             <div class="post_time"><span class="date">05-03</span></div>
                         </div>
                     </div>
diff --git "a/docs/tags/\351\233\206\345\220\210/index.xml" "b/docs/tags/\351\233\206\345\220\210/index.xml"
index 6e2e70fb..f427d1b1 100644
--- "a/docs/tags/\351\233\206\345\220\210/index.xml"
+++ "b/docs/tags/\351\233\206\345\220\210/index.xml"
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     <item>
       <title>ArrayList详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</link>
       <pubDate>Wed, 26 Jun 2024 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</guid>
       <description>ArrayList 在List接口实现类中，最常用的就是ArrayList，ArrayList类是一个可以动态修改的数组，与普通数组的区别就是它是没有固定大小的限制，可以添加或删</description>
     </item>
     <item>
       <title>HashMap详解</title>
-      <link>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</link>
+      <link>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</link>
       <pubDate>Mon, 03 May 2021 00:00:00 +0000</pubDate>
-      <guid>https://whiteppure.github.io/iblog/posts/essays/java-hashmap/</guid>
+      <guid>https://whiteppure.github.io/iblog/posts/detailed/java-hashmap/</guid>
       <description>HashMap HashMap是一个散列表，它存储的内容是键值对(key-value)映射。 HashMap实现了Map接口，根据键的HashCode值存储数据，具有很快的访问</description>
     </item>
     <item>
diff --git a/docs/zh/sitemap.xml b/docs/zh/sitemap.xml
index 11aaf86f..f9dde105 100644
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@@ -43,7 +43,7 @@
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     <lastmod>2024-07-18T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-generics/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/javabasics/rookie-generics/</loc>
     <lastmod>2024-07-15T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/tags/java%E5%9F%BA%E7%A1%80/</loc>
@@ -61,7 +61,7 @@
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     <lastmod>2024-07-11T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/java-arraylist/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/detailed/java-arraylist/</loc>
     <lastmod>2024-06-26T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/tags/%E9%9B%86%E5%90%88/</loc>
@@ -82,10 +82,10 @@
     <loc>https://whiteppure.github.io/iblog/tags/mysql/</loc>
     <lastmod>2024-05-30T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/sql-select-fast/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/detailed/sql-select-fast/</loc>
     <lastmod>2024-05-30T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/java-always-problems/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/codeguide/java-always-problems/</loc>
     <lastmod>2024-05-28T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/tags/%E5%85%B6%E4%BB%96/</loc>
@@ -106,7 +106,7 @@
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     <lastmod>2024-05-25T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/distributed-lock/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/detailed/distributed-lock/</loc>
     <lastmod>2024-05-25T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/tags/%E4%BB%A3%E7%A0%81%E4%B9%8B%E5%A4%96/</loc>
@@ -313,7 +313,7 @@
     <loc>https://whiteppure.github.io/iblog/posts/essays/force-copy-website-text/</loc>
     <lastmod>2024-03-14T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/emp/front-learning-route/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/intro/front-learning-route/</loc>
     <lastmod>2024-02-29T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/tags/%E5%AD%A6%E4%B9%A0%E8%B7%AF%E7%BA%BF/</loc>
@@ -349,37 +349,40 @@
     <loc>https://whiteppure.github.io/iblog/posts/spring/springboot-nacos/</loc>
     <lastmod>2023-09-04T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/uploadfile-code/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/toy/uploadfile-code/</loc>
     <lastmod>2023-08-11T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/pay-code/</loc>
+    <loc>https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/</loc>
+    <lastmod>2023-08-11T00:00:00+00:00</lastmod>
+  </url><url>
+    <loc>https://whiteppure.github.io/iblog/posts/toy/pay-code/</loc>
     <lastmod>2023-08-10T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/posts/spring/springboot-validator/</loc>
     <lastmod>2023-07-01T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/pipeline-business/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/toy/pipeline-business/</loc>
     <lastmod>2023-06-15T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/java-project-reconstitution/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/codeguide/java-project-reconstitution/</loc>
     <lastmod>2023-04-20T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/posts/spring/java-spring-mvc-webflux/</loc>
     <lastmod>2023-04-14T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/distributed-id/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/detailed/distributed-id/</loc>
     <lastmod>2023-03-13T00:00:00+00:00</lastmod>
   </url><url>
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     <lastmod>2023-03-10T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/java-bugs/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/codeguide/java-bugs/</loc>
     <lastmod>2023-03-10T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/tags/elasticsearch/</loc>
     <lastmod>2023-02-14T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/elasticsearch/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/detailed/elasticsearch/</loc>
     <lastmod>2023-02-14T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/posts/keepupd/java-dict/</loc>
@@ -388,10 +391,10 @@
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   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/clean-code/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/codeguide/clean-code/</loc>
     <lastmod>2022-09-01T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/java-design/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/codeguide/java-design/</loc>
     <lastmod>2022-08-02T00:00:00+00:00</lastmod>
   </url><url>
     <loc>https://whiteppure.github.io/iblog/posts/emp/interview-resume-20220422/</loc>
@@ -400,16 +403,10 @@
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     <lastmod>2022-04-09T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/tags/%E7%8E%A9%E5%85%B7/</loc>
-    <lastmod>2022-04-09T00:00:00+00:00</lastmod>
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-    <lastmod>2021-12-10T00:00:00+00:00</lastmod>
-  </url><url>
-    <loc>https://whiteppure.github.io/iblog/tags/%E7%AE%97%E6%B3%95/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/detailed/data-structures-algorithms/</loc>
     <lastmod>2021-12-10T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/java-code-rule/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/codeguide/java-code-rule/</loc>
     <lastmod>2021-11-25T00:00:00+00:00</lastmod>
   </url><url>
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@@ -418,34 +415,34 @@
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     <lastmod>2021-11-19T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/tags/mq/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/detailed/java-mq/</loc>
     <lastmod>2021-10-19T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/java-mq/</loc>
+    <loc>https://whiteppure.github.io/iblog/tags/mq/</loc>
     <lastmod>2021-10-19T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-java-container/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/javabasics/rookie-java-container/</loc>
     <lastmod>2021-10-04T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-reflect/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/javabasics/rookie-reflect/</loc>
     <lastmod>2021-10-02T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/eye-beam/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/codeguide/eye-beam/</loc>
     <lastmod>2021-09-08T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/essays/java-transaction/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/detailed/java-transaction/</loc>
     <lastmod>2021-08-02T00:00:00+00:00</lastmod>
   </url><url>
-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-objectclass-methods/</loc>
+    <loc>https://whiteppure.github.io/iblog/posts/javabasics/rookie-objectclass-methods/</loc>
     <lastmod>2021-07-10T00:00:00+00:00</lastmod>
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-    <loc>https://whiteppure.github.io/iblog/posts/essays/java-small-service/</loc>
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-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-multi-thread/</loc>
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-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-io/</loc>
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-    <loc>https://whiteppure.github.io/iblog/posts/essays/nginx-start/</loc>
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-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-object-oriented/</loc>
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     <lastmod>2021-02-15T00:00:00+00:00</lastmod>
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-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-operation/</loc>
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-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-datatype/</loc>
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-    <loc>https://whiteppure.github.io/iblog/posts/java/rookie-exception/</loc>
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     <loc>https://whiteppure.github.io/iblog/posts/emp/interview-resume-20201124/</loc>
@@ -556,7 +553,7 @@
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-    <loc>https://whiteppure.github.io/iblog/posts/essays/docker-start/</loc>
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     <loc>https://whiteppure.github.io/iblog/posts/essays/java-locks/</loc>
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-    <loc>https://whiteppure.github.io/iblog/posts/essays/cas-detail/</loc>
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